Artificial Intelligence (AI) opens a new era in scientific imaging
While it’s less common to see technology developments fundamentally alter how life scientists work, this is exactly the kind of shift underway in scientific imaging. Advances now coming to the fore not only portend breakthrough discoveries, they will forever change the way we think about and conduct scientific research. The catalyst for this transformation is artificial intelligence (AI)--in particular, the ability to use deep learning to process huge volumes of scientific imagery comprehensively and with super-human accuracy in a fraction of the time required by teams of human scientists.
Illumination-design software optimizes complex geometries
Classical optical lens-design software has grown vastly more capable over the years, but when an optical engineer needs to design non-imaging systems such as illuminators, there’s nothing better than dedicated illumination optical-design software to do the job. Such software (which can be a standalone application or a module of a standard lens-design package) is intended for designing light pipes, lens arrays, diffusers, light sources, standard optics, and combinations of all these, all with highly asymmetrical configurations if needed, and producing customized illumination intensities and patterns if desired. The following is a sampling of various types of illumination-design programs on the market.
High-power diode-laser enhancements boost efficiency and reliability
The development of diode lasers follows the priorities of their industrial users, with a key performance indicator expressed in the cost-per-watt relation. Diode lasers have been available in ever-improving commercial quantities and qualities for quite some time, but it has taken important improvements in performance to enable new areas of application. And diode lasers are still advancing--in particular, their efficiency, peak power, brilliance, and range of emission spectra. Academic research has resulted in new performance records, including more than 60% conversion efficiency at 1 kW and output powers of more than 1.5 kW from a 1 cm bar.
PHOTOTHERAPY: Photobiomodulation therapy--easy to do, but difficult to get right
Light treatments are routinely used in medicine such as blue light phototherapy for neonatal jaundice, psoralen UVA for psoriasis, and anti-tumor photodynamic therapy. The fundamental premise of these treatments is to destroy the targeted chromophore, inflammatory, or tumor cells. In contrast, the use of non-ionizing, non-thermal low dose light treatments is termed photobiomodulation (PBM) therapy. When used in the right dose and clinical context, this treatment can reduce pain and alleviate inflammation while stimulating tissue healing and regeneration. Praveen Arany, president of the World Association for photobiomoduLation Therapy (W.A.L.T.), discusses recent progress in biological mechanisms and its implications on continuously evolving biophotonics technologies in improving clinical delivery.
FIBER OPTICS: Fiber-optic bundles provide 3D stereo imaging
Launching an image through a typical optical fiber results in a scrambled output bearing no resemblance to the input. One way around this is to transmit the image through a bundle of small optical fibers. Each fiber in the bundle acts as a pixel and guides light independently from the other fibers. This maintains the spatial structure of the input image, resulting in a faithful 2D image output. But the added bonus of obtaining 3D stereo information in the form of the “light field” transmitted by the fiber bundles is explained by Antony Orth, as research fellow at RMIT University, enabling unique applications such as biophotonic in-vivo endoscopy and fluorescence microscopy.
LASER DESIGN: Understanding and optimizing laser resonator designs: An overview
Many aspects of the performance of a laser depend substantially on the design of its laser resonator: the power conversion efficiency, the beam quality and the alignment sensitivity, for example. Therefore, it is essential--but often not easy--to develop optimized laser resonator designs. In this article, Rüdiger Paschotta of RP Photonics gives an overview of the important aspects of bulk laser resonators (fiber lasers are outside of the scope of this article), and best design practices.
FIBER-OPTIC SENSING: Smart fiber-optic sensing systems enhance physical border walls and fences
Fiber-optic sensing systems based on elastic or inelastic light scattering effects in standard telecom fibers are powerful tools for analyzing spatially resolved profiles of physical quantities along fiber-optic cables. Their success in multiple applications comes from the cost-efficient measurement of thousands of locations with a single interrogator, the large distance range, and the immunity to electromagnetic interference. After giving an overview on distributed fiber-optic sensing architectures and their main applications, Wieland Hill from NKT Photonics, John Williams from OptaSense, and Gareth Lees from AP Sensing will discuss how a “smart” fiber-optic fence can efficiently complement physical border walls or perimeter fences of critical infrastructure by providing real-time monitoring of intrusions.
OPTICS FOR AUTOMOTIVE LIDAR: Metasurface beam steering enables solid-state, high-performance lidar
One of the newest forms of optical materials to arise from research, metamaterials, and specifically metasurface optics (2D metamaterials), is making the transition from research to practical use. An important example of this is the formation of the automotive lidar components company Lumotive (Bellevue, WA; USA), which has developed a unique form of silicon-chip-based metasurface optics to create an extremely compact and rugged laser-beam steering module for automotive lidar. In this article, engineers from Lumotive discuss their design and progress in developing industry prototypes.
LASER BEAM QUALITY: Beam propagation and quality factors: A primer
Characterizing a laser system may seem like a daunting task, especially when just the laser source itself has many influencing factors, such as power stability, coherence, and wavelength, that govern which application it is most suitable for. However, there are a few key parameters concerning the beam profile itself that provide some insight into the overall system performance, whether it is a gaussian beam in metrology, diode laser system, or high-power materials processing. In this article, Randall Hinton of Edmund Optics (Barrington, NJ; USA) provides an overview of best practices for measuring laser beam quality.
Free-license software removes trial and error in metamaterial design
Because metamaterials can exhibit properties not normally found in nature, the allure of transformational technologies has tantalized researchers for more than a decade. If such promises are realized, virtually every field of research that uses imaging--from biology to astronomy, archaeology to high-energy physics--stands to benefit. On behalf of DARPA, Sandia’s National Security Photonics Center developed the first inverse-design metamaterials software called MIRaGE--short for Multiscale Inverse Rapid Group-theory for Engineered-metamaterials. In other words, a user tells MIRaGE what he or she wants a metamaterial to do, and the program fills in the steps to create it.
Ultrafast lasers hit the spot in medical device manufacturing
The transition from mechanical or chemical processes to laser machining was primarily driven by the need to create very small precise features at a high yield and lower cost. Fine laser welding, marking, drilling, and cutting of metals, glass, and polymers has found application in the fabrication of a wide variety of medical devices and instruments, such as creating lab-on-chip features and dark-marked stainless steel. But in the 21st century, ultrafast laser micromachining has been proven to simplify the overall manufacturing process, particularly by eliminating post-processing steps and reducing overall manufacturing cost for intricate microscale devices such as stents.
Optics replicate human vision in AR/VR display testing
Display testing for augmented and virtual reality (AR and VR) devices demands unique image characterization data and analyses. For instance, luminance and color uniformity are critical when combining images from eye to eye, or when images are overlaid on top of the surrounding ambient environment (as in AR). Emerging AR/VR technologies require an innovative approach to display testing, including new methodology, software algorithms, and--of critical importance for in-headset measurement--new optical geometries. Traditional imaging solutions attempt to meet the unique testing criteria for AR/VR devices but have significant limitations. Above all, a measurement solution needs to closely match the visual capabilities of the human eye to evaluate the true user experience.
FMCW LIDAR: An alternative for self-driving cars
Early in the development of autonomous cars, design engineers chose pulsed lidar systems emitting at 905 nm because such systems were commercially available to plug into their test vehicles. However, today’s 905 nm pulsed lidar has important limits: the high cost of mechanical scanning, interference from solar glare and other light sources, and eye-safety power restrictions that limit lidar range to 60-100 m. Shifting to the retinal-safe 1550 nm band allows pulse powers high enough to range from 200 to 300 m, and advances in solid-state scanning should reduce costs.
MACHINE VISION: Deep learning brings a new dimension to machine vision
Many terms are now being used to describe what is, by some, being promoted as a revolution in machine vision, namely the ability for systems to analyze and classify objects without the need for computer programming. Artificial intelligence (AI) and deep learning are just two terminologies used to promote such concepts. As such, the measurement of parts can be classified as good or bad, depending on whether they fit some pre-determined criteria. Unlike such measurement techniques, so-called “deep learning” tools are better categorized as image classifiers. Unlike software that specifically reads barcode data, they are designed to determine whether an object in an image is present or good or bad, for example.
NANOPHOTONICS: Pattern-transfer nanomanufacturing for micro-optics and spectroscopy
Patterned nanoscale structures hold tremendous promise for both the life-science and photonics industries. Such structures will enable substrates capable of capturing specific biological chemistries, optics to be directly integrated onto the tip of a fiber optic, and the next generation of polarizers and antireflective coatings using metasurfaces on flat or curved surfaces. To create 2D patterned structures at the nanoscale, companies presently use cleanroom microlithography originally developed for transistor manufacturing. An alternative approach created at CIRTEMO, called MagAssemble, is a nanomanufacturing process derived from hard-disk drive technology that takes advantage of the more than 50 years of research and development in that area to lower costs and increase manufacturing flexibility.
3D SURFACE METROLOGY: Getting aligned with freeform optics metrology
For centuries, optical systems were made from spherical and plane optical elements only. Historic images of the first moon landing, tuberculosis bacteria, or of Jupiter’s moons were all made possible without a single asphere or freeform optical element. Since the 21st century, however, the progress of miniaturization has placed new demands on the performance of optical systems, requiring sophisticated laser- and optics-based production and metrology technologies. To measure freeform optics, Mahr metrology systems use mechanical reference points and 3D positioning systems to eliminate as many degrees of freedom as possible to improve--in a step-by-step process--freeform optics production quality and form-to-fit accuracy.
IMAGE FUSION: Spatial-domain filtering techniques dictate low-light visible and IR image-fusion performance
Image fusion is the art of combining multiple images from different sensors to enhance the overall information content as compared to the limited data found in a single-sensor image. For visible and infrared (IR) images, the difference lies in the fact that visible images are the result of reflected light while IR images result from the emission of radiation from the object being viewed. The fused visible-IR image provides supplementary information that improves the perception of the object for the viewer. The performance of image-fusion algorithms depends heavily on how spatial information is extracted and processed through a variety of spatial-filtering techniques.
PHOTONICS APPLED: Quantum Photonics: UNIQORN--Making quantum photonics affordable
Optical setups that can produce, manipulate, and measure single quantum states are expensive, and more importantly, rather bulky and fragile due to the implementation in free-space optics. Within the UNIQORN project, 17 partners are driving the second quantum revolution by merging quantum communications with photonic integration technology in the framework of the European Quantum Flagship. One of the goals of the UNIQORN project is the miniaturization of laboratory-proven QKD and other quantum communications setups by combining photonic integration with free-space optics via a newly developed on-chip micro-optical bench in a PolyBoard platform. The aim is room-temperature-compatible, low-cost, and small-footprint pluggable devices that can make quantum technologies available for everyone.
SUMMARY REPORT: The 2019 Lasers & Photonics Marketplace Seminar
This digest compiles, in written form, the content delivered at the 2019 Lasers & Photonics Marketplace Seminar, held each year in conjunction with Photonics West. A summary of the complete program including keynote from Novanta, forecast information from Allen Nogee, trade and tariff issues in China, lasers in flow cytometry, and scaling quantum information systems are all available at your fingertips. Be sure to attend next year’s conference to see how the laser and photonics marketplaces will fare and if “what goes up” must come down.
PHOTONICS PRODUCTS: Imaging for Surveillance and Security: SWIR cameras cut through haze for surveillance and security
The use of imaging systems for security, defense, and surveillance depends greatly on taking advantage of the infrared (IR) spectrum, which can be divided into near-, shortwave-, midwave-, and longwave-infrared (NIR, SWIR, MWIR, and LWIR, respectively). NIR cameras for security and surveillance are typically low-light (night vision) devices, while MWIR and LWIR cameras accomplish their tasks via thermal imaging. However, SWIR cameras are useful security and surveillance devices in their own right--sometimes by themselves, and often in combination with other imagers. John Wallace cuts through the haze in this feature.
Nonlinear Optics: Engineered metaoptics forge new nonlinear devices
Nanophotonics describes the subwavelength localization of light, and it is usually associated with plasmonics. However, the emerging field of optically resonant dielectric nanophotonics provides novel research directions for nanoscale optics.1 All-dielectric resonant nanophotonics use subwavelength Mie-resonant (or particle morphology-dependent) dielectric nanoparticles as elementary units (or “meta-atoms”) for creating highly efficient optical metadevices. Whether called metamaterial-based optics or metaoptics, the unique optical resonances of these engineered nanoscale structures are accompanied by strong localization of both electric and magnetic fields, and they are expected to replace different plasmonic components in a range of potential applications.
Ray-tracing Software: Structural-thermal-optical performance analysis: The quintessential multiphysics model
The task of setting up a high-fidelity model becomes more challenging for cameras, telescopes, spectrometers, and similar devices operating in extreme environments. This challenge is perhaps most daunting for optical systems on spacecraft. The environment of space can subject equipment to extreme temperature gradients, from the cold vacuum of space itself to the overwhelming heat of the sun and everything in between. Numerical simulation has become an indispensable tool for the design, optimization, and diagnostics of optical systems. A high-fidelity computational model can greatly cut down the amount of time and effort spent on prototyping and related experimental work.
PHOTONICS APPLIED: Biometric Security: The second wave of consumer biometrics is reshaping the VCSEL industry
Fingerprint identification was the first biometric technology used for consumers mainly for historical reasons, beginning with the criminal fingerprint database established by the U.S. FBI in 1892 using ink-based techniques. Fingerprint sensing has remained the most common biometric technology currently used in the consumer space--but probably not for long. But due to the growth of other technologies such as 3D facial recognition, 2018 will be the last year in which fingerprint sensing dominates biometric technologies.
Photodiodes: Dynamic photodiodes reach single-photon sensitivity at low voltages, with minimal noise
With no need for amplification, dynamic photodiodes (DPDs) convert light intensity into time by operating in switched bias mode, generating large forward currents for low-noise, sensitive measurements in high-volume wearable and IoT applications. Tunability of a DPD, accomplished by changing the number of electrons needed for triggering by changing the applied voltage, can be used to increase the dynamic range and background light immunity of the DPD. Potentially, it can help avoid a macropixel architecture, radically reduce the pixel size, and serve many portable sensing applications that increasingly depend on device miniaturization.
Annual Laser Market Review & Forecast 2019: What goes up...
For 2019, despite obvious signs that the past decade of global growth may not be sustainable, we forecast 6.11% growth to $14.6 billion as medical, military, and certain niche industries maintain positive momentum for the laser industry. We can only hope that tariffs will be reversed, stock markets will not crash, and fears of an impending economic downturn are “fake news.” Materials processing and lithography continue to dominate laser sales in 2018—not far behind is communications and data storage, with instrumentation, medical, and displays following the lead. Our annual laser market forecast is our “state of the union” on the laser industry.
Optical Fiber Manufacturing: Gravity-free optical fiber manufacturing breaks Earthly limitations
The compounds that comprise ZBLAN vary greatly in density, giving the material attractive properties across the near-to-mid infrared spectrum. Because of its unique composition of heavy metal fluoride compounds, ZBLAN is formed as a crystalline lattice. This lattice, however, cannot form properly in Earth’s gravity, creating significant barriers to its potential as a commercial telecommunications fiber and limiting production to small quantities for specialty applications. Despite these barriers, ZBLAN fiber is still used in lasers, endoscopy and spectroscopy equipment, supercontinuum light sources, and advanced optics and sensors, and will be dramatically improved when manufactured in zero gravity.
Quantum Photonics: Ensuring quantum-secured communications
Data encoded using current algorithmic key distribution schemes is vulnerable to being cracked with mathematical insight, powerful computers, or future quantum computers. Work is underway on new mathematical algorithms (“post-quantum” cryptography) that will not be vulnerable. However, it will be very hard to provide security against all possible future quantum computer cryptanalysis. QKD techniques encode the key using a physical process, not an algorithmic one. As such, key security depends on the physical performance of the QKD system at the time of key creation.
TECHNOLOGY REVIEW: Laser Focus World’s top 20 photonics technology picks for 2018
Perhaps you believe that the rate of technical invention--the number of good technological ideas conceived per year--is trending upward. If so, you have some facts to back you up: there are more people, and thus more smarts, in the world every year; our tools for inventing are improving, in some ways spectacularly (computing, artificial intelligence, advanced photonic and other hardware). 2018 produces another crop of innovations in photonics that will affect industry, science, academia, and everyone else as well. LFW senior editor John Wallace defines his top 20 photonics technology selections for 2018.
PHOTONICS APPLIED: Transportation: Datasets accelerate integration of thermal imaging systems into autonomous vehicles
Advanced driver-assistance systems (ADAS) increase vehicle safety through features such as adaptive cruise control, lane departure warning, automatic parking, and collision warning avoidance. Automobile manufacturers rely on the advancement of ADAS to achieve the Society of Automotive Engineers (SAE) automation levels of 4 (high automation) and 5 (full automation). However, the sensor suite that enables ADAS--typically visible-light cameras, lidar, and radar sensors--have shortcomings in darkness and through fog, dust, and sun glare. Thermal sensor datasets empower the automotive community to create safer and more efficient ADAS and driverless-vehicle systems in these tough conditions.
Advances in Detectors: The Quanta image sensor (QIS): Making every photon count
A new paradigm for image sensing and capture was suggested in 2005 that led to what is now called the Quanta image sensor (QIS). A room-temperature photon-counting image sensor implemented in a slightly modified mainstream CMOS image sensor (CIS) 3D stacked, backside illumination (BSI) fabrication process that does not use avalanche multiplication, the QIS consists of specialized, low-full-well-capacity, sub-diffraction-limited pixels called jots. Demonstrating single-photon sensitivity at room temperature, QIS technology offers many degrees of freedom in image reconstruction to emphasize resolution, sensitivity, and motion-deblur capability.
Photovoltaics: Collaboration helps scale perovskite photovoltaics for commercial deployment
Despite many unique properties, perovskite PV devices are now competing with well-known and widely deployed silicon-based PV technologies. The efficiency of perovskite solar cells is already on par with silicon cells and is predicted to increase in the following years. Olga Malinkeiwicz, co-founder and CTO of Saule Technologies (Warsaw, Poland), discusses the importance of the involvement of industry partners and clients in the new product development process and how these relationships influence the scaling of perovskite PV technology from the lab to industry from the perspective of an early stage, fast-growing technology company.
PHOTONICS PRODUCTS: Lidar Systems: Automotive lidar draws heavily on photonics industry
Billions of dollars are now being devoted to R&D on autonomous cars and other vehicles. Light detection and ranging (lidar), which has the ability to capture precise 3D images of its surroundings with no dependence on external light sources, is a near-ideal way for autonomous vehicles to “see” and thus to navigate. As a result, automotive lidar is a hot topic, spurring existing photonics companies to ramp up development of lidar components, and new lidar-systems companies to form (and sometimes to be snapped up by large automotive firms). In this article, senior editor John Wallace delves into the technology behind automotive lidar, highlighting the most recent advances.
Advances in Optical Systems: Chalcogenide’s place in the infrared optical materials spectrum
When designing infrared optics, a number of factors must be considered with regard to what materials to use, including refractive properties, optical transmission, athermal performance, hardness/durability, environmental susceptibility, weight/density, fabrication techniques and cost. Chalcogenide glass is one important optical material used for IR systems; in this article, engineers from LightPath Technologies detail chalcogenide’s place in the infrared material spectrum, and when best to use it in your design.
Photonics for Datacenters: Integrated optics permeate datacenter networks
Datacenter networks are facing a key inflection point: While the reach of electrical interconnects shrinks with increasing signaling rates, the capabilities of merchant switch silicon are outpacing those of pluggable optical modules. Rockley Photonics (Pasadena, CA) VP of business development Gregory Finn, system architect Cyriel Minkenberg, and colleagues describe how co-packaging of switch application-specific integrated circuits (ASICs) with silicon-photonics-based optical engines and photonic-integrated circuits (PICs) paves the way out of this predicament.
Ultrafast Lasers: Numerical simulation aids design of fiber-based ultrafast laser sources Optical fibers can be used as laser gain media, including for ultrafast lasers. However, working out designs for such sources is often more challenging than with bulk laser technology, particularly due to strong nonlinear and dispersive effects. Rüdiger Paschotta from RP Photonics (Bad Dürrheim, Germany) provides some example cases showing how such crucial technical aspects can be properly handled in a design process supported by numerical simulations. This leads to prototype and product designs with proven handling of nonlinear effects--for example, so that subsequent implementation in the lab is far quicker and more efficient than with a trial-and-error approach.
Asphere Fabrication: Deterministic aspheric polishing uses multiwavelength interferometry for metrology
The need for more precise aspheric optics has resulted in several new polishing techniques, among them deterministic polishing. By using feedback from a metrology device and proprietary corrective software, computer numerical control (CNC) polishers can now use deterministic polishing to directly achieve form errors of sub 100 nm without the need for additional finishing techniques, such as magnetorheological finishing (MRF). In this article, Matt Zabko at AMETEK Taylor Hobson details how to achieve such results with an interferometric scanning metrology system working in concert with a highly precise optics polishing machine equipped with corrective process software.
PHOTONICS PRODUCTS: Vibration Control: Hexapods provide precise positioning in six axes The hexapod is a simple and elegant way to provide six-degrees-of-freedom (6DoF) position control of a test platform relative to a base. If the movable platform and stationary base are considered rigid triangles for the sake of discussion, the structure of the archetypal hexapod is akin to an octahedron, with six side edges extensible in length and three top and three bottom edges rigid (although some real hexapods don’t look much like octahedrons). Hexapods come in high-precision, high-accuracy, and high-load versions and serve to align optics for assembly, simulate or isolate vibration, and many other tasks.
Interferometry: Hong-Ou-Mandel quantum interferometry breaks nanometer measurement barrier
A simple Hong-Ou-Mandel (HOM) interferometer is typically formed of a source of photon pairs, usually based on spontaneous parametric down-conversion (SPDC) within a nonlinear crystal and a 50:50 beamsplitter with some variable path length for one of the input photons. Quantum optical coherence tomography (QOCT) is a process that uses this feature to measure the structure of layered semi-transparent samples. One arm of the interferometer is directed towards the sample and the reflected photons are collected. Then, a HOM dip is observed for each refractive index boundary that causes a reflection, and the position of the dips gives their locations.
Thin-film Coatings: Ultrathin tunable conducting oxide nanofilms create broadband, near-perfect absorbers
Ultrathin optical films with strong absorption are required for numerous optical applications, including light-harvesting technologies and high-resolution optical space technologies. However, perfect absorption (> 99.9%) usually requires multiple optical film layers with high losses and large thicknesses. Consequently, there is significant interest in the development of new ultrathin optical films with advanced functionalities. A team at Baylor University studies conducting oxide epsilon-near-zero (ENZ) materials that can be used to make ultrathin perfect absorbers with broadband and electronically tunable responses.
Hyperspectral Imaging: Hyperspectral microscopy serves biological pathology
Conventional histopathology relies on stained tissue cell specimens viewed by a microscope with transmission illumination. However, interpretation of these images is often subjective due to limitations in human vision to distinguish subtle color differences. This can be complicated by other phenomenon such as quenching and autofluorescence as well as the use of (RGB) color cameras due to their limited gamut. The inability to objectively delineate critical features such as tumor margins limits the effectiveness of such techniques. However, engineers at Hinalea Imaging describe how hyperspectral imaging, when combined with image processing techniques such as spectral unmixing and classification, enable such features to be easily visualized and identified.
Modeling Software: Understanding the Sagnac effect through ray optics simulation
Engineers developing technologies such as laser and fiber ring gyroscopes for civilian and military applications have the need to test new ideas and configurations in the virtual world using numerical simulation. Here, designers at COMSOL describe how the Ray Optics Module portion of the COMSOL Multiphysics software has been enhanced to provide this capability. In this article, techniques to model the effects of mechanical rotation, or combinations of translation and rotation, are described for optical or fiber-optic systems.
PHOTONICS APPLIED: Atmospheric Sensing: TDLAS atmospheric water vapor sensing improves weather forecasting
Through aircraft-based meteorological observations, tunable diode laser absorption spectroscopy (TDLAS) techniques are making a global contribution to atmospheric sensing advances. A scientist at SpectraSensors describes the performance of its Water Vapor Sensing System (WVSS-II), which combines accurate atmospheric water vapor data for meteorological applications with high reliability, low maintenance, and other characteristics required to achieve certification on commercial aircraft. The article details how the WVSS-II TDLAS instrument is used in harsh aviation conditions to provide atmospheric data for the World Meteorological Organization, the U.S. National Weather Service, airlines such as Southwest and Lufthansa, and partners such as Rockwell Collins.
PHOTONICS PRODUCTS: Fiber Lasers: Visible fiber lasers do red, green, and now bluish
Visible-wavelength fiber lasers (often called visible fiber lasers) have, over the past decade, established their presence in the commercial laser arena. But what is a visible fiber laser? The question is an interesting one, because there is actually no fiber laser on the market that produces visible laser light from within the lasing fiber itself. Visible light can, however, be obtained from a near-infrared (IR)-emitting fiber laser by external frequency conversion--for example, Raman-shifting, frequency-doubling, frequency sum-mixing, or combinations of these approaches. For the purposes of this article, this will be the definition of a visible fiber laser.
Motion Control: Linear motion devices: What is a voice-coil actuator?
A voice-coil actuator, also known as a noncommutated DC linear actuator, is a type of direct-drive linear motor. The term “voice coil” comes from one of its historically first applications: vibrating the paper cone of a loudspeaker. These devices are currently used for a wide range of applications, including moving much larger masses. For example, in optics, voice-coil actuators are typically used in focusing applications, oscillatory systems, mirror tilting, and miniature position control of up to three axes. Understanding the basics of voice-coil actuators, and their characteristics compared to solenoids, enables the proper choice of linear-motion device for your optics application.
OLEDs: Reducing particle defects in cathode film layers improves OLED yield
Comparable to the semiconductor industry where a particle defect can ruin an entire chip, a single particle on a large OLED display can destroy the entire display. Because of the parallels of the display industry to the semiconductor industry, inspection techniques such as automated optical inspection (AOI) have been adopted from the semiconductor industry for OLED display manufactures to monitor their device yield. These AOI quality assurance systems monitor and detect electroluminescence (EL) and color consistency as well as pixel defects in each OLED display.
AR/VR Displays: Engineering the ultimate augmented reality display: Paths towards a digital window into the world
Augmented reality (AR) was first launched in the 1960s with Ivan Sutherland’s AR helmet-mounted display. This clear innovation has set a path to this day in the development of the technology, all the way to the sunglass format that aims to catch the consumer market, to the medical (surgical) and industrial wearables that solve real-world problems beyond entertainment and convenience. In this article, Jannick Rolland from the University of Rochester will walk us through the technical challenges and market opportunities in creating the ultimate AR display.
Advances in Test & Measurement: Photonic advances to dramatically improve astronomical interferometry in the next decade
The technology to enable long-baseline optical/IR interferometry has advanced tremendously in the nearly 100 years since Michelson and Pease first made measurements of Betelgeuse. Today astronomical interferometers routinely use modern telescopes, lasers, precision metrology, low-order adaptive optics, fiber optics, low-noise detectors and high-speed computers. In the coming years, newer telescope technologies, deformable mirrors, integrated optics beam combiners, better detectors, and long-distance beam transport via fibers will revolutionize the field. Experts from the CHARA, NPOI, and MRO Interferometer programs review the current technologies in use at astronomical interferometer sites today and discuss some of the challenges and likely technological upgrades anticipated by the community in the coming decade.
HOW TO CHOOSE A LASER SERIES: How to choose a laser for microscopy
While laser wavelength and power are obvious critical parameters, there are numerous other factors to consider when specifying an optical microscope illumination system. In this article in our How-to choose a laser series, engineers from Coherent (Santa Clara, CA) will answer important questions about choosing a laser for fluorescence microscopy. This choice often determines the success of experiments. The authors review the most critical parameters and explain the impact they have on microscope performance, and direct the reader towards understanding the options and finding a proper solution.
PHOTONICS PRODUCTS: Scientific CMOS Cameras: sCMOS cameras reach new levels of capability
When CMOS cameras first came on the market, their imaging capabilities were too basic for many precision uses in science and industry. Over the years, however, CMOS imaging technology has grown in efficiency, dynamic range, frame rate, and signal-to-noise ratio, resulting in the scientific CMOS (sCMOS) sensor--and sCMOS technology is still advancing. In this article, Laser Focus World Senior Editor John Wallace discusses scientific CMOS cameras and presents numerous product examples.
Photonic Crystal Fibers: Porous-core photonic crystal fibers guide polarization-preserving terahertz waves
Researchers at the University of Adelaide in Australia have developed a novel optical-fiber waveguide consisting of oligo-porous core photonic crystal fiber (PCF) with a kagome lattice cladding for highly birefringent and near-zero-dispersion flattened applications of terahertz waves. Simulation results demonstrate that an ultrahigh birefringence, low effective material loss, higher core power fraction, and negligible confinement loss are achieved at 1 THz. With its favorable terahertz waveguiding properties, imaging, sensing, and polarization-maintaining applications in the terahertz frequency range are possible.
Optical Manufacturing: Polishing aspheres: Spanning the scale of material hardness
Polishing an aspheric optical element with UltraForm Finishing (UFF) is a process that involves a moving belt of polishing material wrapped around a precision compressive wheel. One material property that plays a significant role in the UFF process is material hardness. Fused silica, silicon, and silicon carbide are three different materials that range from relatively soft to extremely hard in terms of Knoop hardness. In this article, engineers at Optipro outline how, by selecting the best UFF belt and coolant/slurry combination, aspheric optical components can be efficiently polished to the desired surface-quality specification.
PHOTONICS APPLIED: Photonics--a fundamental enabler for the Internet of Things
According to Wikipedia, the Internet of things (IoT) is the “inter-networking of physical devices, vehicles, buildings, and other items embedded with electronics, software, sensors, actuators, and network connectivity which enable these objects to collect and exchange data.” If you consider the use of imaging sensors, optics, fiber optics, positioning equipment, and software, you don’t have to look very far to find thousands of existing and emerging IoT applications that can be included in the “photonics IoT” universe. This article sheds light on the most significant photonics IoT applications: 5G, crowd sensing, safety & security, and numerous other applications enabled by photonics.
HOW TO CHOOSE A LASER: How to choose a laser diode for your application
Many engineers consider using a laser diode for any of hundreds of applications. This tutorial by engineers from eagleyard will answer their most prominent questions: Which laser diode is the right one for my application? How to select and work with a supplier? The tutorial will ask a set of questions that directs the reader towards a proper solution using a flow diagram plus lots of comments from seasoned experts in the field. This is part of our series on HOW TO CHOOSE A LASER. Look for other features in upcoming issues of Laser Focus World.
Infrared Optics: New materials extend laser spectral coverage deep into the infrared
Interest in nonlinear optical (NLO) materials for mid-infrared frequency conversion has exploded in recent years due to the emergence of new laser applications ranging from frequency-comb-based spectroscopy to high harmonic generation. Traditional NLO oxide crystals such as LiNbO3 or KTP have limited output wavelengths due to multi-phonon absorption. NLO semiconductors such as ZnGeP and more recently orientation-patterned GaAs offer transparency much deeper into the mid-IR region (including the THz range). Recently, BAE Systems has developed birefringent and quasi-phase matched analogs for these materials--namely CdSiP and orientation-patterned GaP. Peter Schunemann explains recent advances in these groundbreaking new crystals, with wider band gaps and deeper IR transparency.
OPTICAL DESIGN SOFTWARE: Numerical analysis enables energy-efficient photonic switches
Thermo-optic silicon-photonic switches are under design and development at Huawei Technologies Canada for the communications and high-performance computing industries. Design optimization via numerical analysis using COMSOL multiphysics software is being used to minimize power consumption and maximize switching speed. This case study illustrates the crucial importance of knowing, via computer simulation, the characteristics of a silicon-photonics design as it develops and matures.
MODE-DIVISION MULTIPLEXING: On-chip mode-division-multiplexing extends single-fiber communications capacity
As bandwidth demands rapidly increase, new ways to extend communications capacity are required. Technical University of Denmark (DTU) researchers provide a quick overview of one possible solution: mode-division multiplexing. A silicon on-chip mode-division multiplexing/demultiplexing chip developed at DTU is presented that can multiplex from the chip into both polarizations of a few-moded fiber. They describe a demonstration of multiplexing and demultiplexing data--transmitting 3 x 32 Gbit/s over three modes. Furthermore, they describe the possible use of orbital angular momentum modes for mode-division multiplexing.
NONLINEAR OPTICS: Femtosecond lasers and nonlinear optics: New approaches solve old problems in ophthalmology
Ever since the first documented use of spectacles for vision correction around the mid-1200s, scientists have been looking for better ways to correct human vision. A wide range of technologies have been developed to correct vision including eyeglasses, contact lenses, intraocular lenses, and of course, LASIK surgery. Wayne Knox, professor at the University of Rochester, and colleagues have developed an alternative less-invasive approach to vision correction that directly changes the index of refraction of ophthalmic materials by femtosecond laser micromachining. Knox describes the research and development efforts leading to this noninvasive, nonlinear approach to vision correction and its readiness for human testing.
ASPHERES: Finding the right tool: metrology for the manufacture of freeform optics
Freeform optical surfaces are gaining popularity with lens designers and optical system integrators as a method to solve complex optical system design problems. Fortunately, advances in optical manufacturing have opened the possibility of realizing the fabrication of these complex surfaces. However, as manufacturing techniques improve, so must the metrology necessary to measure these parts. Three metrology tools for the measurement of freeform optics are compared: the coordinate measurement machine, a high-accuracy profilometer, and a noncontact optical technique called fringe reflection deflectometry.
WEARABLE PHOTONIC TECHNOLOGY: Photonics gets up close and personal: Advancing wearable technology with light
IDTechEx forecasts the wearable device market to reach more than $150 billion by 2027. Many wearable devices for displaying information or tracking your personal fitness or medical parameters use electrical signals, chemical reactions, or materials-deformation technology. But many wearables depend on light: the emission of light directly into the skin for the purposes of healing, monitoring, and even predicting dangerous medical conditions; illuminated clothing as a personal art statement or safety device; and even photovoltaic wearables that absorb rather than emit light for charging your smartphone or other wearable device.
PHOTODETECTORS: 4th International WORKshop on Infrared Technologies highlights IR photodetector advances
In November 2017, about 80 scientists and engineers with a stake in the infrared (IR) photonics industry gathered at ASU for the 4th International WORKshop on Infrared Technologies, which was held for the first time in the U.S. and was sponsored by Laser Components. Speakers from both industry and academia described the latest advances for detectors operating in a broad range of physical environments and spanning wavelengths from the shortwave-IR (SWIR) region through the midwave-IR (MWIR) or critical chemical 'fingerprint' region and out to the longwave-IR (LWIR) region. Nearly all presenters emphasized that IR photodetector developers need to focus on miniaturization, room-temperature operation, and scalable fabrication.
ANNUAL LASER MARKET REVIEW AND FORECAST: Lasers enabling lasers
Let’s cut to the chase: the key drivers for the laser market in 2017 were consumer electronics devices and China, and the biggest winners on the technology side were fiber lasers, light detection and ranging (lidar) lasers, and vertical-cavity surface-emitting lasers (VCSELs). These trends resulted in record profits for equipment providers in laser materials processing and semiconductor manufacturing, and many of the suppliers of lasers and photonics devices to these manufacturers. In short, lasers are playing a key role in speeding the fabrication of the semiconductor wafers and consumer appliances that are hungry for yet more lasers.
THIN-FILM COATINGS: Thin-film manufacturing considerations for semiconductor lasers
Given the large differences in roadmap technology sharing and scale, it would initially seem unlikely that the laser industry would benefit from microelectronic equipment practices. In fact, many of its practices are directly relevant and are already being adopted by leading semiconductor laser equipment vendors. These suppliers are large enough to have developed proprietary platforms and control systems, and offer processes as well as equipment support, yet small enough to provide the platform customization needed to meet the unique needs of each manufacturer. We will explore some of these practices considering both the process equipment and factory cost of ownership.
SPECTROSCOPY: Back-illuminated CCDs enable advanced spectroscopy instrumentation
Detection systems for spectroscopy are typically 2D silicon charge-coupled device (CCD) arrays, capable of operation from < 200 to 1100 nm. CCDs are available with front- and back-illuminated sensors of various designs. Back-illuminated CCDs include a depletion region of epitaxial silicon varying in thickness from approximately 13 to 40 microns, with the latter designed for improved red quantum efficiency (QE). As you will learn, these are mainstream detectors for spectroscopy because they offer excellent sensitivity, low noise performance, and a variety of configurations to meet the needs of researchers.
Technology Review: Laser Focus World’s top 20 photonics technology picks for 2017
The digital revolution is changing our world in ways both social and technological. While the various overt and subtle changes to our culture(s) may not be fully understood for decades, if that, the changes in technology are more apparent. Optics and photonics contribute hugely to the digital revolution and are in turn furthered by it. Some of these contributions are evident to the average tech-savvy but non-specialist consumer, while others are known mainly to those in the optics and photonics arena. This year’s Tech Review Top 20 list contains items from both categories.
Scientific Imaging: Near-IR microscopes image through silicon without damaging the finished product
While reflected-light microscopy is ideal for illuminating a sample from above, transmitted-light IR microscopy brings light to a sample through silicon from beneath the sample, providing higher contrast. The transmitted-light approach is especially useful for the inspection of alignment patterns or fiducial marks through silicon. Imaging through silicon with dedicated IR objective lenses enables nondestructive flip-chip analysis and other essential evaluations. Olympus Corporation describes how scientific imaging with near-IR microscopes improves imaging outcomes.
Beam Steering: Laser materials processing drives new servo control technologies
Over the past two decades, the use of laser processing for medical, imaging, marking, and manufacturing applications has grown exponentially. This growth is supported by advances in the beam-steering technologies that make these applications possible and the unique requirements for each application motivate the development of new control techniques for servomechanism (servo) drivers that steer the laser beams. For many years, the analog servo driver has been the benchmark for performance, with its flexible tune configurations providing targeted performance at an attractive price and form factor. However, an increasing number of applications have specific performance requirements that are best met with digital technology.
Lidar: A photonics guide to the autonomous vehicle market
Aside from traditional sensors such as cameras, ultrasonic sensors, and radar, lidar technologies are becoming the key enabler in the fusion of sensors needed to achieve higher levels of autonomous control (levels 4/5). Today, there are already multiple designs of lidar systems whose key components are photonic devices such as light sources, photodetectors, and MEMS mirrors. This article by engineers from Hamamatsu will provide an overview of the tradeoffs for lidar vs. competing sensor technologies (camera, radar, and ultrasonic) and reinforce the need for sensor fusion, as well as summarize and compare the top mechanical and solid-state lidar designs that exist on the market today.
PHOTONICS PRODUCTS: High-power Laser Diodes: Pump laser diodes deliver high power for leading-edge application
Because laser diodes are 1) highly electrically efficient, 2) narrowband, 3) bright, and 4) long-life, they are the ideal light source for pumping other lasers. In addition, another defining feature should be added to the list: 5) laser diodes, especially in the form of arrays, can be made to produce extremely high optical powers. In this article, Senior Editor John Wallace looks solely at high-power laser diodes for pumping of solid-state and fiber lasers. Technical and application details of numerous pump laser-diode products on the market will be a highlight of this article.
Microoptics: Surface functionalization -- How microoptics are changing industrial laser applications
As laser technology matures, the question changes from “What can we do with these laser parameters?” to “What laser parameters do we need for that manufacturing process?” Designs of products ranging from consumer electronics to automobiles are creating new shapes and features based on the capabilities of laser technology. As engineers from LIMO explain, microoptics can deliver the essential laser parameters from an off-the-shelve laser source and add more laser-enabled features. They will explain how microoptics provide new options and give examples from semiconductor and automotive applications.
PHOTONICS APPLIED: Terahertz Imaging: Terahertz imaging tackles solar cell and semiconductor process inspection
Optoelectronic systems for terahertz spectroscopy applications have matured significantly over the last few years. An important driver of this trend is the increased use of integrated optical technology from the telecom sector enabling the build-up of compact and high-performance time-domain spectroscopy (TDS) systems. In modern terahertz TDS systems, fiber-coupled and integrated components have fully replaced distributed free-space beam optics, not only improving robustness and space requirements, but also facilitating the integration of terahertz measurement capabilities into different system environments. CEO Michael Nagel and colleagues at Protemics describe new terahertz applications in both scientific and industrial applications--specifically in wafer analysis systems (solar and semiconductor).
Vertical-cavity surface-emitting lasers: VCSEL arrays provide leading-edge illumination for 3D sensing
Compact lidar systems are used in industry, for self-driving automobiles and driver assistance, and other applications. For maximum range in lidar, higher-peak-power lasers are required that are very compact, rugged, and low-cost. For example, several watts of laser power are needed at a distance of up to 100 m. Vertical-cavity surface-emitting laser (VCSEL) arrays are robust and enable such power scaling, providing short pulses at high power density. In this article, Holger Moench of Philips Photonics describes the technology behind and the use of VCSELs for lidar, including applications in consumer and automotive markets.
Spectroscopy: Time-stretch spectroscopy STEAMs ahead
When a pulse of light travels through a dispersive medium such as an optical fiber the group velocity dispersion (GVD) of the medium can act to stretch the pulse in time, with different wavelengths traveling at different velocities. If the cumulative amount of GVD experienced by the pulse is sufficiently large, the spectral profile of the input pulse becomes mapped onto the temporal profile of the output stretched pulse. This intuitively simple process enables a wide variety of cutting-edge photonic time-stretch applications such as serial time-encoded amplified microscopy (STEAM), enabling billion-frame-per-second imaging rates, as described by Robert Thomson of Heriot-Watt University.
PHOTONICS PRODUCTS: Laser Scanning: Polygon beam scanners enable essential applications
One approach for scanning a laser beam is to use one or more oscillating galvanometer (galvo) mirrors, which can allow arbitrary control of the beam position in one or two dimensions. However, if what is needed is a repeated linear scan (or, with slow movement of a stage or second mirror in a perpendicular direction, a 2D raster scan), nothing beats a rotating polygon mirror for simplicity, as there is no oscillatory element with its more-complex control system needed to create linear scans. In combination with an f-theta lens, which translates the constant-angular-velocity scan of a polygon mirror to a constant-linear-velocity scan at the work surface, a polygon mirror and motor can produce a highly accurate scan.
Advances in Imaging: Terahertz imaging--a technology in search of applications
The first advances in terahertz sources, operating at frequencies of 0.1 to 3.0 THz and corresponding to a wavelength range of 3.0 to 0.1 mm, date back to the 1970s. Development of time-domain terahertz technology based on generation of terahertz waves by ultrafast lasers created the second round of excitement about the potential of terahertz imaging in the 1990s. And video-rate terahertz imaging enabled by microbolometer detector arrays developed by INO and NEC around 2005 caused the next wave of excitement in terahertz imaging technologies. But despite losing traction for cancer and security screening, terahertz imaging continues to target several agricultural and industrial applications that may finally benefit terahertz equipment vendors.
Diffractive Optics: How ultrashort laser pulses influence beam-shaping optics
Optical simulation tools can provide a thorough understanding of how ultrashort laser pulses influence the beam-shaping characteristics and capabilities of diffractive optical elements. While versatile and robust, DOEs are highly chromatic in that their functionality depends strongly on the wavelength of light. Using the physical-optics simulation tool VirtualLab developed by LightTrans International, which can accommodate most DOE families (including beamsplitters and beam shapers), engineers at Holo/Or have studied the influence of USP lasers on DOE functionality and found that while effects on most beam-shaper DOEs are negligible, high-angle beamsplitters such as grating-based DOEs can see significant and undesirable chromatic effects
PHOTONICS APPLIED: IR Optics Manufacturing: Laser-assisted μ-LAM process cuts through infrared optics
Ceramics, semiconductors, and optical crystals are characterized by covalent or ionic bonding with high hardness and low fracture toughness, making them difficult to fabricate with traditional diamond-turning or machining processes. But a new technique from Micro-LAM Technologies termed micro-laser assisted machining (μ-LAM) is being used to improve fabrication of silicon (Si), calcium fluoride (CaF2), zinc selenide (ZnSe), and zinc sulfide (ZnS) materials. The patented µ-LAM technology directly heats and thermally softens the workpiece material, in the chip deformation and generation zone, increasing the material’s ductility and reducing material hardness. The process allows easier chip formation, decreased brittleness, and ultimately higher material removal rates.
Fiber-optic Sensing: Transforming FOG coil manufacture from an art to a science
Fiber-optic gyroscopes (FOGs) are one of the most successful fiber-optic sensing systems, with many important applications in navigation and positioning systems, angular velocity sensors, and stabilization equipment. The sensing element is a fiber coil whose quality has a direct impact on its overall performance. Unfortunately, coil winding has been considered an art, not a science, mainly because no effective measurement methods have been available to quantify a coil’s performance. Recently, however, General Photonics introduced multiple methods and processes to quantitatively characterize both the static and dynamic parameters of polarization-maintaining (PM) and single-mode (SM) fiber coils to insure consistent manufacturing of defect-free coils and ultimately, enabling ultra-reliable FOG devices.
Visible Semiconductor Lasers: Standardized multilaser modules enable comprehensive data sets in life sciences
Optically pumped semiconductor lasers (OPSLs) have enjoyed success in life-science applications such as confocal microscopy, DNA sequencing, and flow cytometry. The key trend Coherent (Santa Clara, CA) engineers are seeing in the life sciences laser market--both original-equipment manufacturer (OEM) and end user--is the increasing use of standardized modules or subsystems that are targeted at a specific group of applications. These light engines integrate lasers, optics, mechanics, and electronics in a solution optimized for the application. Specifically, these products offer guaranteed overall system performance, rather than just a particular set of bare laser output parameters. This article reviews three of the key application drivers behind this trend.