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August 2018

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.

 

 

July 2018

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.

 

June 2018

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.

 

May 2018

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.

 

April 2018

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.
 

March 2018

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.   

 

February 2018

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.

 

January 2018

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.

 

December 2017

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.

 

Novemner 2017

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.
 

October 2017

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.

 

September 2017

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

 

August 2017

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.