This PDF file contains the front matter associated with SPIE Proceedings Volume 12665, including the Title Page, Copyright information, Table of Contents, and Conference Committee information.

In this paper, we demonstrate Er³⁺ doped tellurite multi-mode microlasers in 1.5 μm-1.6 μm wavelength range fabricated via the plasma torch method. It is a simple and cost-effective method to produce microspheres with diameter ranges from 11-88 micrometers. Multimode laser output was observed with 0.98 μm pump laser. In addition, we measured luminescence and decay time of the Er³⁺ doped (0.5 mol %, 1 mol % and 2 mol %) samples.

We present theoretical and experimental results of low-noise microstructured mirrors based on silicon on silica for applications in ultrastable lasers. In particular, we show the experimental realization of a hybrid etalon containing microstructured and conventional mirrors. We address the measurement of reflectivity with cavity ringdown spectroscopy, the calculation of noise contributions, and scattered light measurements on the mirror.

Laser frequency fluctuations are one of the limiting factors for many laser-involved precision measurements such as interferometry. Laser frequency locks with the Pound-Drever-Hall (PDH) method use typically an optical cavity as a reference, which are very sensitive to environmental noises. In contrast, spectroscopy methods using atom or molecular transitions and phase modulation spectroscopy behave better in the long term. A wellsealed fiber-based Hydrogen Cyanide (HCN) gas cell that is very compact and light-weighted is chosen. And We investigate laser frequency stabilization using the absorption line of an HCN gas cell instead of a cavity to provide better frequency stability in the low-frequency regime. In our lab, a fiber-coupled HCN gas cell laser frequency lock was built and thermally stabilized to provide better long-term stability. It is designed to work with our heterodyne interferometer around 1550 nm wavelength. The HCN gas cell locking setup using phase modulation (PM) spectroscopy shows less than 0.5MHz frequency drift over 12 hours measurement and stability levels of 1 kHz/ √ Hz for frequencies above 0.2 Hz.

We present a flexible and automated technique to evaluate the quality of periodically poled crystals throughout their entire volume. By translating the crystal perpendicular to the pump laser beam and recording the parametric signal conversion efficiency simultaneously, we were able to quantitatively describe the homogeneity of the ferroelectric domain structure in periodically poled lithium niobate (MgO:PPLN) and potassium titanyl phosphate (Rb:PPKTP) crystals. This analysis included crystals with single, multi, and fan-out grating designs. Such evaluation is non-destructive, achieves precise control and resolution, and provides a practical assessment of the overall efficiency of the quasi-phase-matched device.

Integrated photonic biosensors constitute an important technology for the growing point-of-care paradigm. Due to their high sensitivity and ample design freedom, interferometric sensors are an attractive embodiment for this application. In an effort to continuously lower the limit of detection and build ultra-precise devices, the sensitivity is steadily increased. Thereby, the limiting factors are optical loss, noise, and cross-sensitivities to external perturbations. We present a novel design method for integrated interferometers to inherently compensate for the cross-sensitivity to bulk perturbations in the matrix’s refractive index. We exploit that the analyte induces a localized effect when binding to the bioreceptors. By using different guided modes with engineered phase signals in the interferometer, we distinguish between analyte binding and bulk perturbations. To first order, their optical path may be designed such that the relative change due to bulk perturbations vanishes while sensitivity to the analyte is retained. We demonstrate this methodology via simulations of a Mach-Zehnder-interferometer for an immunosensor based on a silicon nitride platform. We show that this design may be easily incorporated in most conventional layouts, due to an excess of degrees of freedom, and could further be applied in fiber-based devices. In this manner, interferometers utilizing guided modes could compensate cross-talk for perturbations in the matrix’s temperature, pH, or general chemical composition. We believe that eliminating these limiting external impacts could help integrated photonic biosensors to overcome current issues with reliability and robustness.

Endometriosis is a chronic inflammatory disease in women aged from 20 to 40. While laparoscopy and MRI are commonly used methods for detecting endometriosis, its diagnosis remains a challenge due to variations in location of endometrial tissue and symptoms which can vary between individuals.1 We are designing a system that implements photoacoustic spectroscopy in combination with ultrasound to detect endometriosis in vivo without the insertion of a transvaginal probe. In this paper, we will present the design of our system, preliminary results using optical phantoms and discuss the feasibility of our approach in non-invasive in vivo detection of endometriosis.

Light shaping approaches are fundamental techniques adopted in a variety of applications such as material processing, communication, and microscopy. Here, we present a method based on wave front engineering to generate 3D arrangements of Bessel Beams (BB) with independent optical properties all encoded in one single, flat, and lightweight optical element. We fabricated and characterized a Silicon Nitride (SiNx) element using Meta-Surface (MS) technology to generate one of the designed BB lattices. We demonstrated its application in microscopy by integrating it along the excitation path of a light-sheet microscope (LSM) and recording neuronal activity from the zebrafish larva brain.

This project demonstrates the prototype of a low-cost strain sensor by directly coupling light from a resonant cavity light emitting diode into a single mode fiber with a fiber Bragg grating and detecting the transmitted light using a fiber-coupled photodiode. While most strain sensors use expensive techniques for measuring the spectral shift in the reflected or transmitted light from the fiber Bragg grating, such as optical spectrum analyzers or spectrometers, this project demonstrates the use of a silicon photodiode for detection. We measure the coupling efficiency between the resonant cavity light emitting diode and single mode fiber, showing that it is more efficient than coupling between a surface emitting light emitting diode and a single mode fiber. We demonstrate a proof-of-concept strain sensor using these low-cost components that has a detection limit of approximately 100 με. This work could help enable a new application space for fiber-based sensors where many inexpensive sensors are needed, such as distributed sensing networks.

On-product overlay (OPO), with its continually shrinking overlay budget, remains a constraint in the continued effort at increasing device yield. Overlay metrology capability currently lags the need for improved overlay control, especially for multi-patterning applications. The free form shape of the silicon wafer is critical for process monitoring and is usually controlled through bow and warp measurements during the process flow. As the OPO budget shrinks, non-lithography process induced stress causing in plane distortions (IPD) becomes a more dominant contributor to the shrinking overlay budget. To estimate the wafer process induced IPD parameters after cucking the wafer inside the lithographic scanner, a high-resolution measurement of the freeform wafer shape of the unclamped wafer is needed. The free form wafer shape can then be used in a feed-forward prediction algorithm to predict both intra field and intra die distortions, as has been published by ASML, to minimize the need for alignment marks on the die and wafer and allows for overlay to be performed at any lithography layer. Up until now, the semiconductor industry has been using Coherent Gradient Sensing (CGS) interferometry or Fizeau interferometry to generate the wave front phase from the reflecting wafer surface. The wave front phase is then used to calculate the slope which again generates a shape map of the silicon wafer. However, these techniques have only been available for 300mm wafers. In this paper we introduce Wave Front Phase Imaging (WFPI), a new technique that can measure the free form wafer shape of a patterned silicon wafer using only the intensity of the reflected light. In the WFPI system, the wafer is held vertically to avoid the effects of gravity during measurements. The wave front phase is then measured by acquiring only the 2- dimensional intensity distribution of the reflected non-coherent light at two or more distances along the optical path using a standard, low noise, CMOS sensor. This method allows for very high data acquisition speed, equal to the camera’s shutter time, and a high number of data points with the same number of pixels as available in the digital imaging sensor. In the measurements presented in this paper, we acquired 7.3 million data points on a full 200mm patterned silicon wafer with a lateral resolution of 65μm. The same system presented can also acquire data on a 300mm silicon wafer in which case 16.3 million data points with the same 65μm spatial resolution were collected.

Laser-driven light sources (LDLS) have been gaining popularity in semiconductor metrology and spectroscopic measurement in the past 20 years because of their much higher brightness across a broad spectral range with higher stability than traditional electrode-based lamps. In addition, fiber-coupled LDLS systems offer more flexibility and convenience than free-spaced ones. However, due to the limited NA of fiber coupling optics, only light output from one side of a Xe plasma bulb is coupled to the fiber port, with light emitted into the opposite side of the Xe bulb wasted. To address this issue, a dual fiber coupling system is designed and implemented to collect the photons from both sides of a Xe plasma bulb. This paper will present the optical design of EQ-99 based LDLS lamp head with two fiber-coupled ports, the elliptical mirror alignment and optimization, and the performance of both fiber ports’ output, including power spectrum, beam profile, and stability. Besides the total light power from two fiber ports being nearly doubled with the same laser power driver, the mirror coatings and output windows can be individually configured and optimized for different spectral ranges, which can be useful for broadband applications. One good example is its integration into the extended range CSE system to obtain a decent output flux covering 350 to 1100nm.

We explore three types of advanced optical components for use in EO/IR systems. Freeform, GRIN, and meta- optics and combinations of all three used in various system designs are being studied to develop a trade space road map for future utilization. The emphasis is on SWAP benefits while maintaining or improving performance compared to existing systems.

We combine a spectral filter based on an optical rotator with the snapshot polarization and color filtering provided by a modern polarization camera. The combination allows one to convert an RGB color polarization camera into a 12-band snapshot multispectral camera. We discuss the measurement principles and show experimental results from our system.

A broadband spectrum matching light source with a visible to near-infrared (NIR) wavelength range is a valuable tool for broad applications. Based on Energetiq’s early version of spectrum matching light source covering the visible wavelength range (380 to 800nm), we extended the range of spectral matching to 1100nm. The new source has two input beam channels for the visible and NIR light from a single Energetiq LDLS light source. The two beams share the same grating, the digital mirror device (DMD), and the optical path. This innovative design extends the wavelength range with a smooth spectral transition. The new system has a compact system size with a 6.5mm diameter liquid light guide output. The light source has a 5.3nm full-width-half-maximum (FWHM) linewidth from 380 to 800nm and about 11nm FWHM between 680 and 1100nm, based on the input fiber size selection. With its high resolution, the source can be a valuable tool for sensor calibration, hyperspectral imaging, spectroscopy, and biomedical-related applications, which also need to consider the ambient light or NIR light effects and simulate the detailed spectral profiles of arbitrary light sources with more extended wavelength range and high fidelity. The source throughput, switching speed, and output stability will also be discussed.

The precise overlay in see-through AR applications and the development of methods to calculate the registration error for such applications using an AR head-mounted display (HMD) present significant challenges. This difficulty arises primarily due to the absence of ground truth data (GTD) as the scene is partially hidden by view restrictions. Traditional approaches may require expensive setups, like cameras or laser scanners, to capture the hidden area and generate GTD. We propose an approach to calculate the registration error by using a marker-based pose estimation method. We use synthetic data to show the suitability of our method. The synthetic data is created in Unity, where we replicated a see-through application. Therefore, we employ image augmentation technologies for simulating a real see-through forklift application. The utilization of the simulation environment enables the generation of GT). This data forms the basis for evaluating the accuracy of our proposed method. Our primary contributions include a simulated see-through AR application in Unity, a labeled, application-specific synthetic dataset, and a validated method for determining the 3D registration error in world units (mm). This work demonstrates the suitability of the development of a marker-based registration error method to determine a 3D registration error in AR HMD see-through applications, providing an alternative to traditional, more costly approaches.

Additive manufacturing (AM) is an enabling technology for the fabrication of next-generation aluminum mirrors and optical assembles for space applications. Using honeycomb core lattice structures, highly efficient, complex, lightweight optical assemblies have been produced in a single step, reducing both manufacturing times and cost. However, most of the research in this area has been focused on AlSi10Mg, an aluminum casting alloy that was originally adopted for AM due to its ease of processing, despite its limited properties. Recent advancements have allowed for 7A77, a high strength, Al-7075 analog alloy to be additively manufactured. This material has a 2x improvement in tensile strength compared to AlSi10Mg. While optical assemblies are often stiffness driven, the significantly higher strength of 7A77 allows for an even higher degree of margin available for light-weighting, as well as improvements to dimensional stability. To achieve optimal performance, several key properties must be controlled: residual stress and micro-yield strength (MYS). MYS describes the material’s ability to resist irreversible deformation and can be directly related to the dimensional stability of the optic. Residual stress and MYS were optimized through thermal post-processing. The various heat-treated materials were strain gauged and evaluated for changes to MYS. Reductions in residual stress with processing were also evaluated using center hole-drilling measurements. In this work, the T7 temper produced the best combination of residual stress reduction and micro-yield strength. Additionally, the micro-yield strength achieved in this study rivals the macro-yield strength of 6061-T6, which allows for significantly further lightweighting of future metallic optics.

Dichroic mirrors are widely applied in optical and photonic systems due to their light and spectral management capability. We report the fabrication of large-area dichroic mirrors by multilayer inkjet printing. Our approach allows for the additive manufacturing of dichroic structures in different sizes, variable lateral patterns, large areas, and flexible substrates.

Photochromic gemstones exhibit optically controllable coloration at ambient temperatures, strongly affecting their visual appearance and potential market value. As a result, a comprehensive study of characteristic photochromic properties is required to estimate the potential influence on gemstone evaluation. A UV-Visible absorption spectrometer integrating a tunable light source for external excitation has been developed to investigate the wavelength- and time-dependence of photochromism for colored gemstones, focusing on natural, laboratory-grown, and color-treated pink diamonds. The results can be used to develop a color stabilization protocol to improve the reliability of color grading for valuable gemstones.

Reliable and accurate pressure measurement is critical for a variety of applications where regulating flow, volume, and product quality are essential for ensuring safe operation. Traditionally, pressure is measured using gauges. While offering a cost-effect measurement solution, pressure gauges suffer from many limitations, such as frequent calibration needs, low tolerance in harsh environments, and the ability to only provide pressure at the discrete gauge location. To overcome the limitations of conventional pressure gauges, this study describes the development and demonstration of a quasi-distributed optical fiber-based distributed pressure sensor using fiber Bragg-gratings (FBGs) inscribed in a single fiber. The sensor assembly was experimentally demonstrated to show pressure-induced wavelength change that was quantified to successfully estimate pressure for different pressure conditions. The results are validated with finite element method-based numerical simulation.

Hazardous location lighting presents many challenges for illumination. The nature of the environment is such that if lighting fails it could be dangerous to the human operators of the equipment. If the lighting produced has high glare than the features of interest are difficult to distinguish further endangering the operators. A novel optical design is presented which improves glare through an indirect TIR + reflector optic which blends and hides direct view of the LED chips while producing a uniform intensity pattern which meets MSHA distribution requirements for continuous mining and roof bolter machines.

Surface excitation using deep ultra-violet (DUV) laser light has been applied to diamond which reveals growth structures, as well as photoluminescence originating from crystallographic defects features. This valuable information can aid in distinguishing natural diamonds from their lab-grown counterparts and non-diamond gemstone materials. In this research, we presented a dual photoluminescence imaging and spectroscopy setup using a 193nm argon fluoride (ArF) excimer laser, chosen for its above diamond bandgap (5.5eV) photon energy and high average power. This setup enables the detection of diamond’s characteristic photoluminescence emission features and growth patterns under room temperature conditions. Various types of diamonds, including chemical vapor deposition (CVD) as-grown, CVD grownhigh pressure high temperature (HPHT) treated, HPHT-grown, natural diamond and diamond simulant samples were characterized under this setup.

Nonlinear refractive index n₂ is the material parameter, which is used to describe the strength of phenomena caused by third-order nonlinearity, so measuring it accurately is one of the key tasks of nonlinear optics. Several techniques to estimate n₂ of the PCF have been demonstrated, but for example Z-scan is not suitable for any type optical fibers, because this method only allows to estimate n₂ of the material preform of the PCF. Other methods, such as four-wave mixing, self-phase modulation, cross-phase modulation allow qualitatively good estimation of n₂ only when pump wavelength is close to the zero dispersion wavelength (ZDW) of the optical fiber. In this paper, we present a new method of polarization-maintaining photonic crystal fiber nonlinear refractive index measurement using phase shift between orthogonal polarization modes.

High quality imaging camera adaptable for various light environments are highly desirable in artificial visions for autonomous vehicles and drones. The cephalopod vision, especially the cuttlefish eye composed of a W-shaped pupil, a hemispherical lens, and a curved retina with densified pixel distribution and polarization recognizing microvilli, inspires a novel camera system. Here, we report an artificial cuttlefish eye camera, which enables high-contrast and high-acuity imaging by balancing vertically uneven light environments via the W-shaped aperture, by focusing on target visual regions with high resolution via pixel density distribution, and by recognizing the polarization noise via the flexible film polarizer.

We propose novel medical spectacles with the aim to aid in the treatment of torsional diplopia. Using a pixelated approach these may be light, compact and cheap to produce. We found that for a large field of view, or when far from the eye these work well. There was a significant reduction in view quality when close to the eye, especially for the central field of view.

We design an ideal thin lens lookalike surface using a new free-form optical construction method. The method incorporates a one-to-one correspondence to the desired ideal thin lens, resulting in a set of solvable differential equations. The view through the component was simulated and compared to the view through an ideal thin lens. While the resulting lookalike lens mimicked an ideal thin lens near perfectly, it only works well for one specific position — the design position.

This work introduces a pH detector based on a Mach-Zehnder Interferometer (MZI) designed to operate in pH 4.0, 7.0, and 10.0 buffer solutions. The sensor utilizes the monitoring for a particular solution comprising Alizarin Red S and OH carbon nanotubes at a wavelength of 1559 nm.

Skin malformation non-invasive diagnostics is a useful tool to check the state of health and warn if the formation is potentially malignant. A portable smartphone-based system with a triple wavelength illuminator and a diffusive reflector enabling uniform illumination was created for spectral line imaging. Overall 30 skin malformations were analyzed using four modified Beer-Lambert law models for skin chromophore calculations in 3D representation. The first and second Beer-Lambert law models gave the most promising results for hemangioma analysis, the second model gave false results for nevi, and the first and fourth models worked best for melanoma analysis.

This is an ongoing project which involves both the physics of light propagation and magnetism. The idea of the project is to trap photons inside an optical cavity and force these photons to probe magneto-optically responsive samples multiple times – enhancing the non-reciprocal magneto-optic Faraday rotation (FR) imparted to the optical beam. Often, FR in thin film samples is very sensitive to film thickness and its optical properties. In a conventional single-pass arrangement, the usefulness of this technique is limited to films that are thick enough to result in measurable amount of rotation. Such films are typically opaque and therefore are not amenable to transmission techniques like FR. Previously, we measured FR in submicron ITO films on glass substrates [1]. While the FR signal is dominated by the substrate, we can resolve the FR response of the thin films themselves. However, these films, in terms of their thickness, are already a challenge for our set up. An FR-based based multipass sample probing affords reliability to these measurement via an amplification to the FR response. We are optimistic that such an enhancement in the magnetic effects would drastically improve the signal-to-noise ratio of the received optical signal at the detector. This paper focuses on two things; a) the design and performance measurement of an optical cavity for magneto-optic measurements, and b) preliminary characterization of some simple thin film samples. The future goal would be to characterize more challenging samples and measure their response to modulated magnetic fields inside the cavity.

The operation of the optical system in the short-wave part of the optical spectrum makes it possible to increase the value of the resolution. This is relevant for microscopy using lens objectives. It is proposed to design the monochromatic microscope optics for use in NUV and DUV spectral ranges. Also an increase in the resolution is possible when using immersion, for example, water. Upon reaching increased values of resolution, it is necessary to increase the scale of the image obtained on the microscope. The unification of structural parameters for the same type of lens objectives operating in a given spectral range becomes an original engineering solution.

In the classical layout of the light microscope, when the objective is used as a projection system, and eyepiece as an observation, the redistribution of overall and functional parameters is proposed. In the classical layout typically, own linear magnification for objectives is from 2.5 to 100x, and eyepieces from 5 to 30x. It is proposed to use objectives of magnification of not more than 10-15x but having extremely achievable input numerical apertures. In this case, the range of increases of the eyepieces expands to 50x and even 100x. We offer examples of optical designs of objectives and eyepieces. The objective 10x magnification has NA=0.90 and 12.5x NA=1.20 of the water immersion. The linear field in the space of images is 20 mm. In addition, examples of optical designs of eyepieces 50x and 100x are offered too.