External resonator diode lasers are the appropriate choice for species detection in application areas such as medicine, climate and industry due to their excellent properties, but have limitations in terms of high detection rates and commercial availability in the MIR region. Especially in the MIR region, many molecules have particularly strong absorption bands, which can result in very low detection limits and is therefore of particular interest. In this paper, we present our new ICbased laser chips with straight and curved waveguides with a center wavelength at 3.4 μm. These are integrated into an external resonator setup and characterized. The IC-based system enables continuous wave operation at room temperature over a wavelength range of 285 nm with several mW output power. With respect to the problem of high sampling rates, one promising technique is MEMS technology integrated as a tuning element in the external resonator structure. This enables planar drive control for high-frequency resonance-driven MEMS scanners, where the sampling frequency corresponds to the resonance frequency. These will be tested for their suitability and integrated into an ECDL setup and evaluated. Our work will address new requirements in terms of tuning range, output power, and acquisition rate.

Optical sensors are quickly evolving to meet the fast-paced demands of smartphones and mobile devices. These increasingly sophisticated sensors include multi-channel ambient light sensors and integrated sensor modules, with continuous improvements in sensor sensitivity, accuracy, and dynamic range performance. With billions of devices manufactured per year, test throughput, repeatability, stability, and accuracy are critical to success. Current production test systems use traditional sources (bulbs or individual LEDs) or multiple LED based simulation systems, but these have limitations (high variability, insufficient throughput, and low resolution) making them unable to efficiently meet the test needs of the advanced optical sensors being developed and deployed.

We explore the system architecture of a novel high fidelity light source capable of creating, matching, and replicating spectra over the wavelength range of 380 to 780nm with 4.5nm FWHM resolution. This capability gives the ability to generate a near-infinite number of spectra ranging from incandescent to a highly structured source such as a compact fluorescent lamp. The system integrates a high brightness Laser Driven Light Source™ and a proprietary high throughput spectral light engine to achieve the needed repeatability, stability, and dynamic range performance.

The instrument was developed with automated test in mind and offers an easy-to-use application interface for system configuration, output characterization, creation and matching of test spectra, and storage of matched spectra to the instrument. The embedded controller deploys application firmware with onboard algorithms, data management, controls, system monitoring, a communications API, and a TTL interface for test system integration. Instrument architecture decisions and performance data such as repeatability, resolution, stability, and dynamic range will be presented.

A newly developed wavelength tunable light source with a near-infrared wavelength range of 800-1700 nm is presented. The NIR-TLS delivers relatively higher output flux with a narrow bandwidth and high stability. The critical components that led to superior performance include: (1) a higher brightness laser-driven light source (LDLS), (2) optimized achromatic optics for light collection and focusing, (3) a higher throughput monochromator, (4) wavelength matched order sorting filters to eliminate second-order and stray light in output, and (5) a 1500μm core diameter optical fiber optimized for NIR transmission.

With a 1 mm slit width monochromator setting, the TLS produces an average in-band flux of 0.44 mW with an 8.5 nm full-width-half-maximum (FWHM) bandwidth. The maximum in-band power reached is 1.6 mW near 920 nm. We will also discuss the results of output stability measurements.

The NIR-TLS could be beneficial for calibrating and testing NIR detectors and image sensors used in growing consumer products.

The continually increasing sensitivity required for the advancement of far-infrared astronomy dictates that the next generation of space-based observatories must employ cryogenically cooled telescopes and instrumentation. Operating cryogenic instrumentation in orbit poses several challenges, including the need for extremely low power dissipation and precise position measurement and control.

In prior work, we reported on the development of a homodyne three-phase range-resolved laser interferometer, which demonstrated a displacement measurement uncertainty of 2:3nmrms at <4K.¹ Effects of low frequency noise (1=f) in the electrical signals at low velocities were performance limiting due to the interpretation of noise as interference fringes. To avoid 1=f noise, a frequency-modulated continuous-wave (FMCW) heterodyne approach was adopted. An FMCW prototype was developed, and the preliminary results yielded an uncertainty of 29nmrms at <4K.²

In this paper we present the design of an integrated cryogenic FMCW range-resolved laser interferometer which features real time data processing for simultaneous displacement measurements of up to 8 axes. The performance of fibers and their coupling under ultra-high vacuum at cryogenic temperatures is largely unexplored, and we present the cryogenic characterization results of several key variables, including fiber type, termination, and mating, along with alignment effects due to the thermal contraction of fiber components. These results have been incorporated into the design of our cryogenic FMCW interferometer. Applications of cryogenic range resolved interferometry are discussed, with a focus on the integration of the FMCW interferometer with a custom 3-axis cryogenic accelerometer.

This paper presents a high-resolution dual-camera hyperspectral imager based on tunable Fabry-Pérot interferometer filter technology. By using this type of filter technology as the bandpass filter of the camera, conventional 2D image sensors can be employed to capture spectrally resolved image data. The hyperspectral instrument developed in this study consists of one camera for visible and near-infrared wavelength range, and another camera for short-wave infrared wavelength region. Both cameras are equipped with optics for high spatial resolution. In airborne measurements from an altitude of 1 km, the ground sample distance of the instrument is 6 cm and 10 cm for the visible and near-infrared camera and for the short-wave infrared camera, respectively. As a use-case example, hyperspectral airborne measurements from a helicopter are presented, along with the routine for preprocessing hyperspectral frame data captured from a moving platform.

The advent of rapid, cost-effective, high-powered lasers are driving forward advancements in the fields of for soft X-ray and EUV imaging, ptychography, spectroscopy and tomography. This coupled with increasing investment in industrial EUV lithography and semiconductor metrology processes is creating demand for fast, high resolution and sensitive detectors in the 20 eV to 10 keV range. Here we present the latest detector developments in the field of sCMOS for direct EUV and soft X-ray detection. We demonstrate how sCMOS technology is able to overcome the limitations of slow scan CCD technology to provide high resolution direct EUV and soft X-ray detection with a greater than 16-fold speed increase whilst maintaining low noise compared to classical CCD detectors.

Most active quench circuits used for single-photon avalanche detectors are designed either with discrete components which lack the flexibility of dynamically changing the control parameters, or with custom ASICs which require a long development time and high cost. As an alternative, we present a reconfigurable and robust hybrid design implemented using a System-on-Chip (SoC), which integrates both an FPGA and a microcontroller. We take advantage of the FPGA’s speed and configuration capabilities to vary the quench and reset parameters dynamically over a large range, thus allowing our circuit to operate with a wide variety of APDs without having to re-design the system. The microcontroller enables the remote adjustment of control parameters and re-calibration of APDs in the field. The ruggedized design uses components with space heritage, thus making it suitable for space-based applications in the fields of telecommunications and quantum key distribution (QKD). We characterize our circuit with a commercial APD cooled to -20°C, and obtain a deadtime of 35ns while maintaining the after-pulsing probability at close to 3%. We also demonstrate versatility of the circuit by directly testing custom fabricated chip-scale APDs, which paves the way for automated wafer-scale testing and characterization.

Future cars enable more use of interior lighting with special visual effects. In order to optimize visual effects, the light scattering behavior of these materials must be precisely characterized. We present the development of a photonic instrument for light scattering measurements in terms of BSDF (bi-directional scattering distribution function). The instrument is principally a goniophotometer. We designed and built a fully automated BSDF measurement device including data processing optimized for low light signals including evaluations and justifications. Due to these optimizations, the photonic device has currently an accuracy of less than 0.08 % (2 sigma standard deviation). In addition, the dynamic range is currently about 10 decades. We will implement further optimization steps soon.

Fresnel reflectivity suppression using random nano-structured surfaces (rARSS) has been investigated by numerous groups in recent years. A variety of measurement methods are used, from simple specular reflection to directional transmission and combinations thereof. In most cases, there is the assumption that the incident irradiance is only divided between specular reflection (R) and on-axis transmission (T), ignoring wavelength-dependent bidirectional scatter radiance distributions that attenuate both on-axis intensities. Broadband spectroscopic measurements over limited surface areas are common, assuming that there is good structure uniformity across the optical surfaces under test. Process development of rARSS requires repetitive functional testing and measurement, which at times is a result of intrusive techniques, such as electron microscopy of sample crossections, albeit in limited surface areas. We explored a double amplitude-division interferometric non-invasive technique, based on a Fabry-Perot etalon/Michelson interferometer (FPE/MI) combined instrument, to extract the absolute specular reflectance and on-axis transmission of single optical surfaces in the midwave to longwave infrared (2.0-12 μm), without sacrificing the samples. The technique was applied to before-and-after rARSS addition on infrared transmissive silicon, gallium arsenide, and germanium windows. The entire FPE/MI test system losses were taken into account, which can be considerable due to differences on sample setup conditions. We determined the interference ordinal-area of the FPE resonances within the MI scanning sub-bands, and extracted single surface values for R and T, which agree with independent spectroscopic measurements. The technique can be applied to large surface areas, limited only by the size of the MI aperture.

Wave Front Phase Imaging (WFPI), a new wafer geometry technique, is presented, that acquires 7.65 million data points in 5 seconds on a full 300mm wafer providing lateral resolution of 96µm. The system has high repeatability with root-mean-square (RMS) standard deviation (σRMS) in the single digit nm for the global wafer geometry and in the sub ångström (Å = 10-10 m) range for the full-wafer nanotopography for both 200mm and 300mm blank silicon wafer. WFPI can collect data on the entire wafer to within a single pixel, in our case 96µm, away from the wafer edge roll off. The flatness of the silicon wafers used to manufacture integrated circuits (IC) is controlled to tight tolerances to help ensure that the full wafer is sufficiently flat for lithographic processing. Advanced lithographic patterning processes require a detailed map of the wafer shape to avoid overlay errors caused by depth-of-focus issues. We present WFPI as a new technique with high resolution and high data count acquired at very high speed.

Time-resolved fluorescence spectroscopy is a promising and versatile spectroscopy technique. While conventional fluorescence spectroscopy is concerned with the spectral features of fluorescence emission, time-resolved fluorescence spectroscopy (TRFS) also captures the temporal behavior of the excited molecules. In addition to applications in rapid medical diagnoses, several applications were reported in forensics, chemical analysis and biology.

The existing TRFS systems are based on complex optical setups which results in bulky and large systems. Therefore, using them in practice is still not feasible. In this work, we present a miniaturized system that combines a compact Czerny-Turner based spectrometer layout with our high-speed time-gated image sensor of 32×32 pixels based on the Current-Assisted Photonic Sampler (CAPS) sensor.

The system operates in the visible wavelength range with a high spectral resolution. The novel image sensor is capable of measuring down to sub-nanosecond lifetimes. The proof-of-concept module was assembled and characterized for three fluorophores.

Photonic spectrographs offer a highly miniaturized, flexible, and stable on-chip solution for astronomical spectroscopy and can be used for various science cases such as determining the atmospheric composition of exoplanets to understand their habitability, formation, and evolution. Arrayed Waveguide Gratings (AWGs) have shown the best promise to be used as an astrophotonic spectrograph. We developed a publicly-available tool to conduct a preliminary examination of the capability of the AWGs in spectrally resolving exoplanet atmospheres. We derived the Line-Spread- Function (LSF) as a function of wavelength and the Full-Width-at-Half-Maximum (FWHM) of the LSF as a function of spectral line width to evaluate the response of a discretely- and continuously sampled low-resolution AWG (R ~ 1000). We observed that the LSF has minimal wavelength dependence (~5%), irrespective of the offset with respect to the center-wavelengths of the AWG channels, contrary to the previous assumptions. We further confirmed that the observed FWHM scales linearly with the emission line width. Finally, we present simulated extraction of a sample molecular absorption spectrum with the discretely- and continuously-sampled low-resolution AWGs. From this, we show that while the discrete AWG matches its expected resolving power, the continuous AWG spectrograph can, in principle, achieve an effective resolution significantly greater (~ 2x) than the discrete AWG. This detailed examination of the AWGs will be foundational for future deployment of AWG spectrographs for astronomical science cases such as exoplanet atmospheres.

The paper presents a novel and fast method to characterize thin film conformality on microscopic 3D High Aspect Ratio substrates. The thin film deposition experiment uses specially designed PillarHall(TM) Lateral High Aspect Ratio (LHAR) silicon chip as a substrate. The measurement on a chip relies on the conventional planar surface characterization tools such as optical microscopy, line-scan reflectometry and ellipsometry. The results show that the method is fast and accurate way to characterize thin film conformality as well as other film properties, and also in wafer-level.

The common challenge for reconstructive spectrometers is achieving high spectral resolution without sacrificing device stability, size and costs. Here a fully integrated scattering chip-based spectrometer build on Raspberry Pi platform is designed and implemented. It exhibits no dependence on temperature and humidity (22.7-23.8 °C and 39.5-41 %), is confined in small space (box 50x35x35 mm) and it can reconstruct spectra with resolution up to 0.05 nm (50 pm). The only instability – gravitational mechanical micromovements were compensated by applying pixel binning and device can still reconstruct spectra from binned pictures as small as 32 x 24 pixels.

An ultraviolet tunable light source (UV-TLS) is a valuable tool in studying the effectiveness of virus inactivation using UV radiation. UV-TLS can verify effective inactivation UV dosages at different wavelengths to help establish industrial UV safety standards and calibrate UV radiation sources.

We developed a high throughput UV-TLS to support research into methods of inactivating coronavirus, including the virus that causes the COVID-19 disease. The light source is powered by a laser-driven light source (LDLS™) with high UV wavelength brightness, superior stability, and a 10,000-hour lifetime. The UV-TLS covers the wavelength range from 200 nm to 770 nm and has a fiber-coupled output. Advanced design features include: (1) all reflective optics for aberrationfree light coupling; (2) a high-efficiency UV grating blazed at 250 nm; (3) fiber-coupled output with a 600 μm core diameter deep-UV fiber for application flexibility.

Measured data shows that the UV-TLS achieved an in-band flux of 0.98 mW with an averaged FWHM of 4.3 nm in the 200 nm to 400 nm range, using the 600 μm fiber. The averaged in-band flux reaches 2.9 mW for free-space output with an averaged FWHM of 7.2 nm.

Advantages of the newly developed UV-TLS are relatively higher in-band flux, UV light output at any wavelength from 200 nm to 400 nm, and the flexibility of a fiber light delivery. The bandwidth of UV output flux can be adjusted by selecting different monochromator slit sizes.

Purposefully induced axial chromatic aberration is the core of the chromatic confocal metrology technique. Through the resulting generation of separated focal planes for each wavelength of a broadband light source a measurement volume is created and a three-dimensional reconstruction of the topography of technical and biomedical surfaces and layers can be performed. Based on the chromatic confocal metrology technique various metrology sensors and measurement systems have been developed, with high axial and lateral resolution, accuracy and precision. For a significant increase in measurement points, that can be measured simultaneously and the resulting reduction in measurement time, a chromatic confocal method utilizing a micro-lens array in combination with a improved spectral peak detection, has been developed. Through a single image acquisition, the object topography can be measured for multiple points simultaneously and therefore mitigating the need for axial as well as lateral scanning of the object. For this reason in-situ applications have become a viable domain. First preliminary results of testing a laboratory setup of the proposed system design are presented.

Time-Domain Low-Coherence Interferometry (TD-LCI) is a well-known optical method to perform absolute distance measurements. As an alternative to conventional TD-LCI, the Self-Mixing Super Luminescent Diode (SM-SLD) technique represents a unique approach for simplicity and compactness. The presence of optical feedback in the source cavity allows obtaining huge interference fringes, even with diffusive targets and without using high-sensitivity and low-noise detectors. In this work, we present the performances of a custom-made SM-SLD interferometer for absolute distance measurements compared with a reference incremental interferometer. Thanks to the simplified acquisition method and the resulting improved signal-to-noise ratio, the system exhibits excellent metrological performances.

An Optical Phased Array (OPA) is similar to a one dimensional (1D) dynamic diffraction array. The phase law of the emitters is numerically programmable and enables to form a beam, that point towards a targeted direction. OPAs have a high potential for a new generation of LiDAR (Light Detection and Ranging) systems, since they avoid mechanical beam scanning. For the development of such LiDAR, many characterizations are essential to optimize the OPA and to get a full control of their performance. To carry out these tests, CEA-Leti has developed a modular optical bench designed to characterize large scale 1D-OPAs in free space. This bench allows beam-forming calibration at various angles thanks to an optical setup based on far-field imaging in the Fourier plane. This set up directly analyses a field of view of 22° (-11°/+11°) and can rotate in the azimuthal plane of the OPA to cover angles ranging from -50° to +50°. The OPA board is mounted on an additional rotation stage to match the OPA beam output with the beam forming set-up optical axis. For practical use, the optical axis is parallel to the floor (i.e. to the optical table). Moreover, after calibration, additional options allow to switch the setup for practical operations, as the OPA use in real space, e.g. for aiming at a target. A Peltier and a regulation loop allow testing the OPA at various temperatures. Fast photodiodes have been implemented to measure the switching time between distinct angular positions. In this paper, we report data acquired with this setup on a 256 channels OPA operating at @1550 nm, that is based on grating antennas with 1.5 μm pitch and thermo-optic phase shifters.

This work focuses on the established self-homodyne coherent receiver (SHCR) method, which is enabled by recent advancements in chip-based coherent receivers. The accuracy of the SHCR method strongly depends on the fiber delay employed. This effect, critical when characterizing narrow-linewidth lasers, is not documented to our knowledge. We present a comprehensive study of this dependence, yielding an optimal fiber delay that maximizes signal-to-noise ratio. The results are validated by comparison with a commercial frequency-noise analyzer, which shows a comparable accuracy between both methods.

Precision displacement laser interferometry is crucial in various applications such as microlithography, high-performance profilometry, and gravitational wave detection. We are currently developing a fiber-based heterodyne laser interferometer that features compact size and low noise floor. Laser beams at two different wavelengths are utilized to construct a fiberbased interferometer system. Narrow band spectral filters are used to separate the beams of different wavelengths and to control their optical paths. The highly common optical paths between the two interferometers provide a high commonmode rejection ratio to instrument and environmental noise sources. In this paper we present the interferometer design, benchtop prototype system, and preliminary measurement results obtained in the lab environments. A benchtop prototype shows sub-nm/√Hz displacement sensitivities in air at frequencies above 100 mHz in our lab.

Optical LIDARs and laser range finders (LRF) require high sensitivity near 1nW while also having fast recovery to overloads as high as 100W peak optical power. Fast overload recovery is required in order to detect subsequent signals after sensing bright targets. In the current work, CMC have created a new family of InGaAs APD LIDAR/LRF receivers, 264-339822-VAR [6] , having a higher dynamic range than most commercially available receivers. While maintaining the existing family of receivers’ bandwidth and APD gain, a 1.8 x increase in responsivity can now be achieved, while reducing the NEP by 12%. In addition, new improvement to the receiver include reducing overload recovery time to 331ns from a laser pulse of 6W peak optical power allowing close secondary target detection, and achieving NEP as low as 184fW/√Hz at +85°C.

In petrochemical industry, downstream operations can be optimized detecting hydrocarbons in the gas phase. Laser-based spectroscopic sensors are well suited for this application, since they proved to be highly selective, sensitive and robust. Quartz enhanced photoacoustic spectroscopy (QEPAS) is an optical technique, offering also a high level of compactness. In this work, a QEPAS sensor implementing a custom T-shaped quartz tuning fork and an interband cascade laser emitting at 3367 nm was employed to detect methane, ethane and propane in natural gas-like mixtures. The partial least square regression analysis was implemented to measure the hydrocarbons concentrations in the acquired signals.

The extension of the detection range is a crucial task for improving the effectiveness of gas sensors. In this work we propose a novel approach in quartz-enhanced photoacoustic detection in which the detection module is composed of a bare 15 kHz custom tuning fork (QTF), aligned with a 12 kHz QTF and mounted inside a vacuum-tight cell. This configuration allows the same molecule to be detected by the bare QTF at high concentration and by the 12 kHz QTF down to part-per-billion scale. The signal from the bare QTF is also useful to gather information on the gas matrix variation.

With emerging technologies, which result in more intensive industry and manufacturing, fully portable and multi-gas detectors are increasingly being required on to handle situations where a wider range of hazardous substances may be present and proper detection equipment is essential.

Most gas monitoring devices focus on a single species. However, there are many sensing applications (e.g.: industrial chemical processes) where several gases need monitoring at the same time and with a single detector. In this regard, a novel portable QEPAS (Quartz-Enhanced Photo-Acoustic Spectroscopy) multi-gas detector with non overlapping QTFs (Quartz Tuning Forks) resonance frequencies can help meet these challenges.

Composite materials offer significant performance advantages due to their lightweight, high-strength, and high stiffness. This led to their adoption in several industrial sectors with particular emphasis on the aerospace industry which has undergone a transformation towards a composite-dominated new standard. In order to respond to the increased demand, it is mandatory to focus on an efficient and well-controlled curing cycle of the resin, which will lead to a significant reduction of cost and an increase in production speed. Currently, manufacturers use filling and curing cycles with high safety margins which can be optimized by applying process monitoring techniques, which up to now use thermocouples and dielectric sensors. However, these electric solutions suffer in terms of operating capabilities and the facilitation of integrating them in composite materials (due to their size and electrically conductive aspect when using carbon fibers). We present the design and evaluation of a miniaturized novel photonic integrated sensor, fabricated in 220 nm top SOI platform, capable of measuring key monitoring values that facilitate optimization of the curing process. The operation principle is the spectral shift of a silicon Bragg grating component's resonant wavelength. Bragg grating design and postprocessing of the integrated chip allows for measuring different key values such as temperature, refractive index and pressure all in ~1.5 mm diameter. The fabricated temperature sensors achieve a significant 0.084 nm/°C thermo-optic efficiency with high accuracy (0.5 °C) and repeatability across a very wide dynamic range (temperature 27 to 180 °C).

Multispectral imaging technology analyzes for each pixel a wide spectrum of light and provides more spectral information compared to traditional RGB images. Most current Unmanned Aerial Vehicles (UAV) camera systems are limited by the number of spectral bands (≤10 bands) and are usually not fully integrated with the ground controller to provide a live view of the spectral data.

We have developed a compact multispectral camera system which has two CMV2K 4x4 snapshot mosaic sensors internally, providing 31 bands in total covering the visible and near-infrared spectral range (460-860nm). It is compatible with (but not limited to) the DJI M600 and can be easily mounted to the drone. Our system is fully integrated with the drone, providing stable and consistent communication between the flight controller, the drone/UAV, and our camera payload. With our camera control application on an Android tablet connected to the flight controller, users can easily control the camera system with a live view of the data and many useful information including histogram, sensor temperature, etc. The system acquires images at a maximum framerate of 2x20 fps and saves them on an internal storage of 1T Byte. The GPS data from the drone is logged with our system automatically. After the flight, data can be easily transferred to an external hard disk. Then the data can be visualized and processed using our software into single multispectral cubes and one stitched multispectral cube with a data quality report and a stitching report.

Optical fiber-based sensing is uniquely qualified for a wide range of harsh environment applications due to the ability of optical fiber to withstand high temperature or chemically corrosive conditions. While off-the-shelf silica fiber is stable up to 800-900°C under a wide range of conditions, single crystal fiber offers a pathway to operation above 1000°C. Current single crystal fiber growth techniques are limited to producing multimode fiber, which limits interrogation approaches to primarily time-domain techniques. Raman-based distributed temperature sensing is one time-domain technique which has demonstrated significant utility for distributed temperature sensing in conjunction with multimode, single crystal fiber.

A distributed temperature sensor based on Raman scattering and consisting of a single crystal probe spliced to an arbitrarily long silica lead is considered for operational environments up to 1400°C. The impact of temperature and wavelength-dependent optical loss on the measured temperature is investigated, particularly at temperatures above 1000°C. Strategies for improved performance at extreme temperatures are also discussed.

Streak cameras are popularly used to passively record dynamic events for numerous studies. However, in conventional operation, they are restricted to one-dimensional field of view (FOV) imaging. To overcome this limitation, the multipleshot and the single-shot two-dimensional (2D) steak imaging approaches have been developed. For the former, the (x,y,t) datacube is acquired by combining the conventional manipulation of streak cameras with a scanning operation. For the latter, the (x,y,t) information is obtained by combining streak imaging with other imaging strategies, such as compressed sensing (CS). Despite contributing to many new studies, the multiple-shot methods require a large number of measurements to synthesize the datacube, and the single-shot approaches reduce the spatiotemporal resolutions or the FOV. Here, we overcome these problems by developing streak-camera-based compressed ultrafast tomographic imaging (CUTI), which is a new work mode universally adaptable to most streak cameras. Grafting the principle of computed tomography to the spatiotemporal domain, CUTI uses temporal shearing and spatiotemporal integration to equivalently perform passive projections of a transient event. By leveraging multiple sweep ranges readily available in a standard streak camera and a new CS-based reconstruction algorithm, the datacube of the transient event can be accurately recovered using a few streak images. Compared to the scanning-based multiple-shot 2D streak imaging approaches, CUTI largely reduces the data acquisition time. Compared to the single-shot methods, CUTI eliminates the trade-off between the spatial resolution or the FOV and temporal resolution.

Wavelength-tuning Fizeau interferometer has been widely applied to measurements of optical surfaces. However, when measuring highly reflective surfaces, such as silicon wafer surfaces, a coupling error between higher harmonics and phase-shift miscalibration, can cause a significant systematic error in the calculated phase. In this study, a new 11-frame phase-extraction algorithm is derived for the suppression of the coupling error. The 11-frame algorithm was visualized in the frequency domain and complex plane, and its compensation capability was confirmed by numerical error analysis. Finally, the surface shape of the silicon wafer was measured by applying the 11-frame algorithm and Fizeau interferometer.

Red palm weevil (RPW) is a harmful pest that has wiped out many palm plantations worldwide. Early detection of RPW is difficult, especially on large plantations. Here, we report on combining fiber–optic distributed acoustic sensing (DAS) and machine learning to detect weevil larvae less than three weeks old, in a controlled environment. In particular, we use the temporal and spectral data provided by a fiber–optic DAS system to train a convolutional neural network (CNN), which distinguishes “healthy” and “infested” signals with a classification accuracy higher than 97%. Additionally, a rigorous machine learning classification approach is introduced to improve the false alarm performance metric by >20%.

In this paper, we propose a hetero-core optical fiber with a high refractive index material, TiO₂, deposited on the inner layer of the Au island films, which is fabricated by sputtering method and annealing. It was confirmed that this structure of TiO₂ deposited on the inner of the Au island films strongly excites the absorption peak in the visible light region and detects the refractive index change in the near-infrared region compared to the conventional hetero-core optical fiber sensor using Au island structure.

We propose the hetero-core fiber optic refractive index sensor using ITO nano-particles. The hetero-core optical fiber has a structure that leaks transmitted light while maintaining mechanical strength. The ITO is well-known to have an absorption band in the infrared region. The ITO nano-particles were formed on the fiber by the wet process. We have experimentally confirmed that the ITO nano-particles hetero-core fiber sensor causes a change in transmission loss at refractive index in the near-infrared region. Therefore, we demonstrated the fiber optic refractive index sensor using the ITO nano-particles film only in the infrared region.

We have proposed and developed a CO₂ sensor by coating hetero-core optical fiber surface plasmon resonance (SPR) sensors with ionic liquid (IL) gel coating. The hetero-core optical fiber has no electrical contact in the sensor portion as a feature of the optical fiber. In our previous study, it was confirmed that the proposed hetero-core fiber CO₂ sensor using 1-ethyl-3-methylimidazolium tetrafluoroborate ([EMIM][BF₄]) as an IL can successfully detect CO₂ gas. However, so far, ILs other than [EMIM][BF4] for the sensor has not been tested yet. Since it is known that the CO₂ solubility in ILs changes by changing cations and/or anions, CO₂ sensing characteristics of the proposed sensor could be affected by the used IL. In the present paper, we examined how the change in cation and/or anion in the IL affects the CO₂ sensing characteristics of the proposed sensor using four different ILs. 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([BMIM][Tf₂N]), 1-butyl-3-methylimidazolium trifluoroacetate ([BMIM][TFA]), 1- butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF₆]), and 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF₄]), having different CO₂ solubility in descending order. By measuring the transmitted spectra and, optical loss change, we evaluated the sensitivity and responsiveness of the fabricated CO₂ sensors. The results showed that for all four IL coatings, the SPR spectra was observed using the fabricated sensors. Further, All the CO₂ sensors with different ILs showed response to CO₂ gas. Especially, the sensor prepared using the IL of [BMIM][TFA] exhibited the highest optical loss change in response to CO₂ concentration change.

This PDF file contains the front matter associated with SPIE Proceedings Volume 12008, including the Title Page, Copyright information, Table of Contents, and Conference Committee listings.