This PDF file contains the front matter associated with SPIE Proceedings Volume10545, including the Title Page, Copyright information, Table of Contents, Introduction, and Conference Committee listing.

Highly-functional photonic sensor networks integrated in thin polymer foils offer great potential for versatile applications in the life sciences, medicine, environmental analytics or production technology. For their realization, suitable low-cost and high-throughput production techniques need to be developed. Here, we describe work towards this goal, i.e. the fabrication of multimode polymer waveguides through a combination of thermal imprint and doctor blading. For imprint master stamp fabrication, a combined Bosch and O₂ plasma etching process in silicon is utilized. We also demonstrate stamp fabrication by an additive manufacturing method, i.e. by employing maskless UV lithography, to enhance the flexibility and cost-effectiveness of our approach. We, thus, realize various all-polymer waveguide arrays, beam splitters, and grating couplers which serve as basic elements to create more complex photonic circuits. We also demonstrate polymer based transmission lines comprising semiconductor as well as organic light sources and detectors. We discuss both the integration of semiconductor light sources and detectors such as verticalcavity surface-emitting lasers (VCSEL) and photo detectors as well as organic light emitting diodes (OLEDs) and organic photo detectors. In first applications, we combine these elements to create sensor arrays for measuring temperature, strain or refractive index. We show results of various sensor types utilizing different measurement principles implemented in laboratory environments so far. For example, a waveguide array containing a linear discontinuity which serves as elongation zone for displacement, strain or tilt measurement by detecting the intensity variation of the transmitted light propagating inside the structure is presented. In future, we plan to create more powerful sensor photonics networks for reliable and robust applications in real life, e.g. for point-of-care testing or production monitoring.

The design and implementation of flat optical photonic devices have come to the forefront of ongoing scientific research and technology development. These novel photonic devices use sub-wavelength metal or dielectric resonators spaced on a specific two-dimensional pattern that mimic the phase profile of conventional bulk optical elements. However, most of these structures, known as “metasurfaces”, have so far been passive with its optical performance determined only by the spatial configuration of the metasurface constitutive elements. The development of dynamic metasurfaces is currently a growing area of research directed to obtain real-time tunable operation of metasurfaces and new physical phenomena not feasible with static metasurfaces. In this presentation, I will describe the fundamentals and advantages of incorporating metallic and dielectric metasurfaces onto MEMS devices. The MEMS platform enables electrostatic control of curvature, tilt angle and deformation of metasurfaces, enabling flat and agile optical elements with msec reconfiguration time. Faster reconfigurable metasurfaces can be achieved using MEMS based spatial light modulators in which individual pixels are patterned with nanostructures having different optical response, e.g. we could pre program fixed phase shifts onto each pixel, so the device works as a curved mirror with aberration correction on top. By actuating specific sub-set of pixels, the far-field response of the adaptive metasurfaces can be manipulated. These unique dynamic metasurfaces may provide new opportunities for information optics and imaging by performing complex signal processing directly in the optical domain.

In this study, we present diffractive optical elements printed on reduced graphene oxide (rGO) thin film using a femtosecond (fs) laser as the direct laser writing source. Graphene oxide (GO) is an interesting optical material providing unique properties such as the large light absorption modulation level during its laser reduction process; after the photoreduction, the transparent GO become opaque rGO. In order to fabricate the diffractive optical pattern of GO and rGO with sub-micrometer resolution, we use femtosecond laser pulses to induce the photoreduction of GO resulting in the ultrathin binary diffractive optical elements such as a light diffraction grating and a Fresnel lens. In addition, the rGO can play a role as a complaint electrode so that the rGO pattern can be applied to a dielectric elastomer actuation (DEA) after the pattern is transferred to a dielectric elastomer substrate with the few tens of micrometer thickness. As a high voltage is applied to the flexible substrate, it can be stretched, which leads to the expansion of the diffractive element; it means the light diffraction pattern of the element can be tunable as well. Therefore, we could control the optical specifications of the elements, such as grating period and the focal length of the Fresnel lens. Because of the simple fabrication process and arbitrary patterning capability of the femtosecond laser direct writing will provide ultrathin, tunable, compact, cost-effective, and highly efficient optical components over conventional optics.

MEMS technologies have been used successfully to miniaturize optoelectronic systems. Nonetheless alignment issues limit the level of miniaturization for complex optical systems. Especially off-axis optical designs such as used in Czerny-Turner spectrometers or "Schiefspiegler"-cameras offering completely reflective and thus chromatic aberration free optics are difficult to shrink. On the other hand multiple applications request extremely miniaturized and light weight modules for mobile devices, automotive or unmanned aerial vehicles.

A new concept for the efficient realization of complex optical systems has been invented and patented [1]. For the so-called "place and bend assembly" a planar substrate is used which features preprocessed bending lines. Due to the progress in production technologies, 3D printing for small and medium volumes as well as other advanced plastic process technologies for high volumes with supreme accuracy are available. Optical, electronic as well as MEMS components can be placed on such a substrate using standard but precise planar technologies. Then the different parts of the substrate are bent and form the 3D body. Simultaneously the optical path inside is generated. This concept is not limited to rectangular shapes. It may also be possible to realize the "W-configuration" of a Czerny-Turner spectrometer in a very efficient way.

The first proof of concept has been achieved with a camera device realized from a 3D printed substrate. An entrance window, two spherical mirrors, an aperture stop and a detector array have been assembled using planar technology. Afterwards the substrate was folded and fixed. The functional capability has been demonstrated by capturing test images which have been optically evaluated. Challenges for the future development will be named and discussed.

Acoustic wavelengths are about 5 orders of magnitude shorter than EM waves of the same frequency. This can be a critical advantage in the quest to further miniaturize devices that have dimensions linked to their characteristic resonance frequencies. Therefore, many novel multiferroic (MF) devices rely on the transduction of signals from EM radiation to surface and bulk acoustic waves, and yet acoustic wave interactions in complex MF heterostructures are poorly understood. Here, an all-optical interferometric imaging system is developed for two-dimensional scanning imaging of acoustic wave amplitudes with sub-angstrom surface displacement sensitivity and submicron spatial resolution. Measurement capability has been verified with a 50-MHz piezoelectric SAW bandpass filter, with the frequency spectrum showing similar behavior to the S21 transmission measured with a network analyzer, and with a linear dependence on the input power. Spatial dependence of the acoustic waves also behaves as expected, with the largest amplitude near the input electrode. Next, the system has been demonstrated to detect acoustic waves in MF heterostructure-based MEMS devices with frequencies up to 3 GHz. These detections pave the way for fast and reliable troubleshooting of new device designs involving acoustic waves, in which it may not be immediately clear to where or by what mechanism power is being dissipated.

More than 100 million people in the United States of America alone suffer from age-related presbyopia caused by a loss of focal accommodation of the eye crystalline lens as the lens stiffens with age. The resulting accommodative error or lag produces blurred images of objects placed at different distances. Conventional fixed uniform or graded power eyeglasses cannot provide accommodation thus resulting in significant visual impairment. In this paper we will discuss the implementation of lightweight auto-focusing eyeglasses that augment the accommodative range thus partially or fully restoring normal vision function. The paper discusses some aspects of the construction of tunable power eyepieces and the implementation of accommodation correction algorithms.

We discuss the design, manufacturing and characterization of a miniaturized zoom camera objective featuring two gravity-immune liquid-tunable aspherical lenses and three spherical glass lenses. The aspherical tunable lenses, which are 3 mm in diameter, 8 mm in nominal focal length and neutral to gravity effects, can be pressuretuned within a large focal length range with very low spherical aberration. This leads to high optical resolution across the entire zoom range despite the limited number of optical elements in the system. The effective focal length of the objective continuously shifts from 4.5mm to 9 mm, with the field of view changing from 40° to 20°. All the optical components are assembled on a three-layer optical platform, which provides a lateral and axial positioning accuracy of ±10 µm for all components. Furthermore, the platform also maintains fluidic access to the tunable lenses for pressure tuning via an external pressure controller. The total dimensions of the objective are 5 mm×6.5 mm×17 mm, making the system compatible with mobile imaging applications. The highly compact system with the thickness of 6.5mm was achieved by folding the optical path using a 45° mirror. The optical performance of the system is characterized across the entire zoom range through imaging measurements.

We present the concept, realization and prototype demonstration of a compact array camera suitable for automotive applications. The multi aperture optics consists of four similar lens objectives and a facetted mirror array in order to select the specific viewing direction of the individual optical channel (field-of-view segmentation). This partly decouples the trade-off between camera thickness and focal length creating a very compact module. Besides this new design, a hybrid optics technology - creating a mix of spherical glass together with aspherical, wafer-level-optics lens elements – is applied in order to achieve the thermal stability needed for the automotive application.

Current mobile devices such as smartphones are expected to contain high-resolution cameras that include a multitude of features in ever slimmer form factors. These cameras are expected to have a wide field of view, image stabilization, fast auto-focus and a sense of depth to enable depth-of-field effects or gesture recognition. However, physical laws limit straight-forward miniaturization of these cameras.

A folded multi-aperture design with a segmented field of view and laterally trimmed optics promises to deliver the same performance and features in a package that is half the height of a traditional optics module. Only mature technologies such as injection-molded lenses and voice coil motors are necessary to realize this system.

In this work, we present results from our first technological demonstration units. We show that trimming the typical front-stop design lenses of smartphone camera modules only reduces their field of view, without compromises to optical performance in the central field. We discuss how mirror placement affects the behaviour of the system in unexpected ways. Finally, we follow the process of calibrating the demonstration units and outline the challenges in processing the channel images to generate a seamless complete image for all scenes.

Intelligent light management systems are intended to detect the presence of people for enabling a customized lighting control. State-of-the-art systems are based on passive infrared sensors or conventional surveillance cameras. However, they either require a recurring motion within the detected field of view or they are not well-accepted by consumers.

We present the optical design of a highly miniaturized, wide-angle camera, which acquires a large field of view of 110° and offers an ultra-thin appearance with a z - height of less than 1 mm. This combination is achieved by means of multiaperture imaging. The implemented demonstrator contains a double-sided, refractive freeform array combined with a baffle array, which prevents optical crosstalk between the multiple optical channels. Both components are aligned in front of a CMOS sensor.

Until very recently, handheld spectrometers were the domain of major analytical and security instrument companies, like Thermo Fisher Scientific and Smiths Detection, with turnkey analyzers using spectroscopic techniques from x-ray fluorescence (XRF) for metals to Raman, mid-infrared and near-infrared for organics. However, the past few years have seen rapid changes in this landscape with the introduction of handheld laser-induced breakdown spectroscopy (LIBS), ‘smartphone spectroscopy’ focusing on medical diagnostics for low resource areas, a commercial MEMS FTnear-infrared engine, implementation of Texas Instruments’ DLP chip for the near infrared using a Hadamard scheme, ‘hyphenated’ or dual technology instruments, and some low cost visible/near-infrared instruments selling directly to the public.

Successful handheld instruments are designed to give answers to non-scientist operators, and therefore their developers have put extensive resources into reliable identification algorithms, and qualitative and quantitative calibrations. LIBS builds on more than 60 years of experience in optical emission (arc-spark and inductively-coupled plasma) spectroscopy, while smartphone spectroscopy leverages existing colorimetric assays and their ‘chemistries’. Handheld near-infrared analyzers have similarly built on the decades of calibrations on laboratory instruments in food, feed and agriculture. The low-cost consumer instruments use a different model: crowd-sourcing for the company, and also crowd-sourcing for the data, with analysis in the cloud, not on the instrument itself.

This paper outlines the portable spectrometer field, and discusses databases, calibrations and algorithms, and also caveats on crowd-sourced data, especially for heterogeneous samples.

Mid-Infrared (MIR) spectroscopy is a powerful method to identify different molecular species due to the fact that molecular vibrations exhibit strong responses in this spectral range. In order to control and optimize the chemistry process, as well as enhance the chemical output, an in-situ measurement is necessary. However traditional MIR spectrometers are usually bulky and expensive, and are difficult to use for a spatially distributed, real-time detection, especially in a micro-reactor.

We present here a highly-miniaturized continuously tunable optical bandpass filter in the MIR range for chemical detection in microreactors. Similar to a Fabry-Perot interferometer, the micro filter consists of two parallel multi-thin-film Bragg mirrors and an air gap, spaced by Liquid Crystal Elastomers (LCEs). The LCE is a novel actuator material composed of crosslinked polymer chains exhibiting strong macroscopic contraction as temperature is raised. We will show that the LCE can provide an extremely precise yet large mechanical movement of the two parallel mirrors leading to large freedom in the wavelength tuning range. Design, fabrication and measurements will be shown, demonstrating the functionality of the filter.

In this work, we report the detection of C₂H₂ and CO₂ in the NIR range using a MEMS Fourier Transform Infrared (FTIR) spectrometer. For this purpose, a super resolution autoregressive (AR) algorithm is used. The spectrometer is working in the wavelength range 1300–2500 nm while its core engine is a scanning Michelson interferometer micromachined using deep reactive ion etching (DRIE) technology on SOI wafer. The interferometer scanning mirror is driven by a MEMS electrostatic actuator with travel range corresponding to a resolution of about 30 cm^-1.The spectrometer with the algorithm are used for measuring a standard optical filter with line width of 1 nm and measured line width is 1.7 nm that corresponds to 7.5 cm^-1. The spectrum of a mixture of C₂H₂ and CO₂ is measured using the MEMS spectrometer and a gas cell with 10cm light-gas interaction length. The AR model is applied on the interferogram. The resulting spectrum after the AR application shows an enhanced resolution of 15cm^-1 that led to better identification of the absorption peaks.

Next generations of mobile phones will contain spectral analysers. Different concepts and system designs compete in this ultra-high volume market. Especially for the analysis of organic matter, which can be food, human skin or other items, the near infrared range offers substantial advantages, most of all a suitable penetration depth and relevant spectral information. On the other hand the spectrometer has to meet the requirements for the use in a mobile phone, i.e. size and price must drop significantly. The reliable operation, especially for the evaluation of the spectra with chemometric models, requires a very stable wavelength scale of the spectroscopic system. The deviation must not exceed 0.5 nm during operation under any condition and for each device used.

Resonant MEMS devices combine multiple advantages: Ultra compact designs can be realized, MEMS motions allow an operation using a single detector to meet cost issues even with extended InGaAs technology and the position feedback ensures a precise and long term stable wavelength scale. Based on such resonantly actuated MEMS components NIR spectrometers have been designed. Recent research work aims for extreme miniaturization of the optical bench. The presented assembly technology has been optimized for volume production. The outline from the previous published work will be shrunk to 10 x 10 x 5 mm³ with only a slightly reduced resolution. The new design will be optimized for cost efficient production as well.

A low-cost, compact electrostatic deformable mirror is developed using widely available polymeric materials. The fabrication method offers exceptional post-fabrication mirror flatness error of < 250 nm RMS, which can be reduced below 22 nm at best-flat. A custom real-time control system is also constructed and high fidelity reconstruction of Zernike modes up to the 4^th radial order is presented. Real-time wavefront correction is also demonstrated using a spatial-carrier laser interferometer as a wavefront sensor.

We present a design for an on-chip MEMS-actuated Variable Optical Attenuator (VOA) based on Silicon Photonic MEMS technology. The VOA consists of 30 individual mechanically movable MEMS cantilevers, suspended over an integrated, 1 μm wide bus waveguide, each terminating with two optical attenuation bars. By exploiting the pull-in instability, electrostatic actuation allows to move the individual cantilevers into proximity of the waveguide, leading to scattering of the evanescent field and thus attenuation of the remaining optical power in the waveguide. Electrodes are placed below the cantilevers for electrostatic actuation. Mechanical stoppers are used to avoid contact between the cantilevers and the electrodes and to keep the bars at a precisely defined distance of 60 nm away from the bus waveguide. The attenuator provides nearly zero insertion loss in OFF state, while in ON state, the attenuation range is defined by the number of actuated digital attenuation cantilevers and can be adjusted in discrete increments of only 1.2 dB. Owing to the small size, fast microsecond scale response time can be achieved, and electrostatic MEMS actuation allows for broadband and low-power operation. Our design exhibits a compact footprint of 30 μm × 45 μm, attenuation from 0 dB to 36 dB, while keeping return loss below 27 dB. To the best of our knowledge, this is the first presentation of a design of a VOA in Silicon Photonic MEMS technology.

We have designed, fabricated and tested narrow-band Fabry-Perot filters in the infrared using gold porous mirrors and a silicon spacer layer. The filter peaks at 10 μm and 15 μm have approximately 10% transmission and a 1.5% linewidth. A Fabry-Perot structure with plane metal layers having a similar linewidth would have a transmission of only 0.2%. Thus, for the same linewidth we have improved the transmission by a factor of 50. Apart from the optical enhancements, these filters also have the advantage that they can be made inexpensively in a standard silicon MEMS technology and that their resonances can be finely tuned through post processing.

Tunable laser sources are used in a wide range of novel applications such as spectroscopy, biomedicine or gas sensing techniques. New requirements in terms of size, tuning speed and output power are addressed with our work.

We present a miniaturized external cavity diode laser concept which will be compared with well-known laser systems such as distributed feedback (DFB) lasers. DFB lasers suffer high internal losses due to the overlap of the DFB grating with the optical waveguide. Our concept of Micro Electro Mechanical Systems (MEMS) based lasers are stabilized with a transmission grating, resulting in significantly less losses. Furthermore, the tuning of the diffraction efficiency of the gratings allows the optimization of the output power and the overall tuning range, which is measured to be one order of magnitude larger than what can be achieved with DFBs. It is also important to point out the tuning speed of the MEMS lasers due to the fast nature of the tilting capabilities of the MEMS actuators. Excellent relative intensity noise and narrow linewidth features are present in these laser systems due to the low noise driving electronics for both the diode lasers and the MEMS actuators.

The high output power and the low linewidth will enable a higher sensitivity and resolution for a wide range of applications. The performance of the MEMS laser systems will be presented, being suitable for applications such as Raman spectroscopy or tunable diode laser absorption spectroscopy (TDLAS) in the wavelength ranges of 780 nm and 920 nm.

Fluorescence lifetime determination is widely utilized for bioscience research and analysis. The fluorescence stimulation in conventional systems is usually done with expensive picosecond laser systems. We present a cost-effective 370 nm LED based excitation module with a pulse FWHM of 1 ns and a beam diameter of 4 mm. The functionality of the excitation module was demonstrated with the fluorescence dye ATTO 390 with a fluorescence lifetime of 5 ns. The width of 8 mm of the excitation module enables the parallel measurement of adjacent sample chambers of a well plate. Further, a silicon UV-photodiode is designated to monitor the output power of the LED. For a fast analysis of the fluorescence signal, we developed an ASIC for fluorescence histogram recording. The ASIC determines the time between excitation pulse and incoming fluorescence photon with an accuracy of about 80 ps. The ASIC blind time after the excitation pulse is configurable. The determined time is saved in bins. The width of the bins is programmable. For fluorescence light detection a silicon photomultiplier (SiPM) is used. Output of the ASIC is a histogram with the counted amount of photons at the different times after excitation. This histogram equals the fluorescence response of the dye. The fluorescence lifetime can be calculated out of this histogram.

In this work, we report a novel notch optical filter based on the imaging properties of a MEMS-based Multimode Interference (MMI) waveguide. The concept is based on the dependence of the imaging lengths on the different wavelengths, where each wavelength exits the waveguide at a different lateral position. Thus, by properly choosing the output waveguide position, it is possible to have a good selective optical filter as well as a good notch optical filter (the complementary response). To validate this concept an MMI structure is fabricated using Deep Reactive Ion Etching (DRIE) technology on a silicon-on-insulator (SOI) wafer. The walls of the waveguide are metalized with Aluminum to decrease the insertion loss. The design makes use of the compactness of the parabolic butterfly shape to reduce the MMI length. The structure is fed by a 9/125 single-mode fiber and the Amplified Spontaneous Emission ASE out of a Semiconductor Optical Amplifier is used as a wideband source for the optical response characterization. The output is measured on an optical spectrum analyzer demonstrating a notch filter response around 1550 nm with about 20-dB rejection ratio. The reported results open the door for integrated, low-cost and fabrication insensitive optical MEMS notch filter.

In this paper, we demonstrate a compact silicon photonics based vibrometer using an on-chip photonic grating (OPG) based sensor. OPG works on the principle of interference where the motion of the cantilever is captured at the output as an intensity variation. The advantage of OPG based sensor over conventional Laser Doppler vibrometer is increased tolerance to alignment errors as both the grating and the cantilever can be integrated on a single chip. The grating parameters were optimized using 2D-FDTD to achieved maximum sensitivity to the displacement of a cantilever. OPG with on-chip germanium photodetector is studied, which indicates a sensitivity of 54 μW/nm. We experimentally demonstrate the feasibility of the proposed sensor that can achieve a displacement sensitivity of 5.3 μW/nm.

MEMS based microendoscopes have become important imaging tools for early cancer diagnosis and precise tumor resection. Due to various technical challenges, few microendoscopes have been translated to clinics or applied to human patients. Through synergistic collaborations, we have developed novel MEMS scanner enabled microendoscopic multispectral (640nm to 780nm) three- dimensional dual-axis confocal fluorescent imaging system for translational applications, including early cancer detection and staging on colorectal cancer, molecular imaging guided surgical navigation on head and neck cancer. Based on dual-axis confocal microscopic architecture, we have miniaturized the imaging system with compact form-factor by integrating micro-optics and a patterned gold coated MEMS scanners, which have been custom-made and mass-produced in the nanofabrication foundry. The metal coating of the scanning mirror provide over 80% high reflectivity over near infra-red range. Both axes of the MEMS scanner could perform large tilting angle (> 6 degree mechanical scan angle) at DC and resonant mode. By advanced computational imaging approach, we have achieved real-time cross-sectional imaging in either raster or lissajous pattern scanning with fast frame rate (> 10 Hz) with large field-of-view (> 600 microns). Advanced real-time mosaicing algorithm has been developed to achieve broader view in millimeter scale. By utilizing molecular contrast probes conjugated with fluorescence dye, we have successfully demonstrated multi-spectral ex-vivo and in-vivo imaging on small animal tumor models and human tissue specimens, aimed for both early cancer detection and molecular imaging guided surgical navigation.

Retinal imaging laser eyewear has a miniature laser projector inside the frame which provides the wearer with digital image information through the pupil using the retina as a screen. Its principle is based on the geometric optics of the Maxwellian view combined with a parallel and narrow RGB laser beam. A prototype with the trademark of RETISSA® was invented with a miniature laser projector inside the glasses frame using a non-axisymmetric free-surface reflecting mirror. The image resolution was measured based on the visual acuity testing using a retinal projected image of Landolt ring for four subjects with the different naked visual acuity of 0.04, 0.5, 0.9 and 1.2. Also, the theoretical image resolution was studied based on the beam propagation simulation under the eyeball model. The results show how to achieve high resolution and free focus in proper balance by adjusting the laser beam characteristics of the beam diameter and divergence. On the laser safety, RETISSA® was found to be in the Class I category, which has the safety factor of over 700 in the RGB radiation intensity under the international standard of IEC60825-1. RETISSA® also met the thousand times more strict Class I criteria of FDA/CDRH 21CFR1040.10 with the total RGB radiation intensity of less than 0.37 μW, indicating its laser radiation is not considered to be hazardous as stated in the definition of FDA Class I. The experimental evidence that the radiation of RETISSA® is equal to or weaker than displays of conventional digital devices also provide its proof of safety, including its long-term use as one of daily digital devices. The potential of retinal laser imaging is mentioned for use in ophthalmology medicine. The current activity on the medical welfare applications as low vision aids and ophthalmic testing equipment is reviewed including clinical research and trials in Japan and Europe.

Multi-modal endomicroscopy is one of the most promising means to enable optical biopsy methods to attain the specificity and selectivity of conventional biopsy. However, the development of the complex opto-mechanical systems needs very high assembly tolerances, and robust, biocompatible and ultra-slim packaging solutions. Therefore, the prototyping and low-volume manufacturing of multi-modal endomicroscopes are often costly and time intensive processes.

We present the opto-mechanical design of a novel endomicroscope combining wide-field microscopy and 3D OCT, and demonstrate the advantages of 3D glass micro structuring based assembly and packaging in terms of optical performance and device miniaturization. Using ray-tracing based Monte Carlo simulations, we demonstrate that this precision leads to a significantly better optical performance compared to that offered by rival 3D machining techniques, such as the state-of-the-art 3D polymer printers and conventional micromachining based solutions.

This paper presents a novel miniaturized hand-held hyperspectral imager for VNIR range of λ = 600 – 900 nm based on MEMS Fabry-Perot interferometer (MFPI) technology. In recent years, tunable MFPI optical filters have been utilized to demonstrate sensors for mobile applications, including CO2 smartphone sensor for mid infra-red region and hyperspectral iPhone for visible spectrum. This hand-held sensor module targets the VNIR range in order to enable food sensing, while utilizing low-cost camera technology to enable potential volume scalability for future sensing applications. The sensor module is wirelessly connected to a mobile device, which enables further application algorithms development and cloudbased solutions.

The fast growing consumer electronics market of connected and wearable devices is driving a wealth of new applications. Personal capability for detecting and monitoring substances part of our everyday life (food, cosmetics, drugs, etc.) by spectroscopic means will soon become a reality as a number of new miniature spectrometers are being reported. These devices mostly operate in the visible and near infrared spectral region due to the readily available lowcost detectors in these spectral regions. However, enhanced selectivity is achievable in the molecular fingerprint spectral region (7-20 μm), allowing for applications that would be difficult or impossible at lower spectral wavelengths. To this end, a compact, portable, Long-Wave Infrared (LWIR) hyperspectral imager was developed. It is based on INO’s MICROXCAM-384 camera featuring a 384 x 288 pixel, 35 μm pitch uncooled bolometric broadband Focal Plane Array (FPA) and Fraunhofer ENAS’ 2 mm x 2 mm aperture MEMS tunable Fabry-Pérot Interferometer (FPI). The INO’s broadband FPA exhibits a Noise Equivalent Temperature Difference (NETD) lower than 25 mK (for the 8-12 μm range at 300 K, 50 fps and f/1) and a flat spectral response from 3 to 14 μm. The footprint of the hyperspectral imager is 7 cm x 8 cm x 10 cm excluding the source. The spectral resolution varies from 55 to 220 nm depending on the type of FPI used. The Noise Equivalent Spectral Radiance (NESR) is 430 mW/(m² .sr.μm) at 9 μm. Using this hyperspectral imager, spectra of various substances including polymers were recorded in the transmission, reflection and transflectance configurations. A good agreement was found with spectra obtained by applying the FPI transfer function to spectra recorded with a commercial FTIR spectrometer. The LWIR configuration of the imaging spectrometer will be described and test results presented.

Small, tunable MEMS Fabry-Perot interferometer (FPIs) have recently been demonstrated to enable hyperspectral imaging in mobile devices, so far using Bragg reflector mirror technologies, which however limit the device tuning range. This paper presents the realization of a novel MEMS FPI structure based on Ag thin film mirrors (AgMFPI), which allows tuning the entire visible - very near infrared (VNIR) wavelength range (for example 450 - 900 nm) with one single component. The characterized transmission of the components is 12 - 45% with full-width-half-maximum values (FWHM) between 11 - 18 nm using 2 mm optical aperture, while using 3 mm optical aperture results in FWHM values of 12 - 20 nm. A very compact hyperspectral imager can thus be built to cover this spectra by combining this AgMFPI and a typical RGB type of image sensor.

Optical systems for remote sensing commonly employ the principle of multi-/hyperspectral imaging, which is based on the acquisition of a set of two-dimensional images with distinct spectral bands in the ultra-violet, visible and/or infrared domain. Novel applications in the fields of environmental and agricultural monitoring, surveillance and biomedical inspection require miniaturized systems with high spectral and spatial sampling that furthermore enable a single shot image acquisition. However, conventional high resolution multi-spectral imaging solutions rely on bulky setups and depend on scanning techniques. In this work, we propose a multi-spectral imaging concept based on a multi-aperture system approach combined with a slanted linear variable spectral filter in order to overcome these restrictions. In particular, we demonstrate the optical design, fabrication and testing of a highly-compact, cost-effective multispectral imaging system, which exploits state of the art micro-optical manufacturing techniques on wafer level. The developed demonstration system incorporates a conventional full-frame format image sensor, a commercially available linear variable spectral filter and a customized microlens-array. In addition, a tailored baffle array is utilized for preventing optical crosstalk between adjacent optical channels. The setup enables the single-shot acquisition of 66 spectral channels with a linear spectral sampling over an extended wavelength range of 450-850 nm. The compact system with a size of only 60 x 60 x 28 mm³ provides a large field of view of 68° and a spatial sampling of 400x400 pixels per channel. Finally, we demonstrate its capabilities for advanced object classification by utilizing a customized multispectral analysis tool.

A translatory MOEMS actuator with extraordinarily large stroke - especially developed for fast optical path-length modulation in miniaturized FT-spectrometers (FTS) designed for NIR spectral region (800 nm – 2500 nm) - is presented. A precise translational out-of-plane oscillation at 260 Hz with a stroke of up to 700 μm and minimized dynamic mirror deformation of 80 nm is realized by means of an optimized MEMS design. The MOEMS device is driven electro-statically near resonance and is manufactured in a CMOS-compatible SOI process. Due to the significant viscous gas damping, dominated by the drag resistance of the comparatively large mirror plate with 5mm diameter, the resonant MEMS device has to operate under reduced pressure. A mirror stroke of 700 μm at a driving voltage of 4V is achieved by hermetic encapsulation of the actuator at at a maximal pressure of 3.2 Pa. For FTS system integration the MOEMS actuator has been encapsulated in an optical vacuum wafer-level package (VWLP) to guarantee a long-term stable vacuum pressure of 0.1 Pa and lifetime t ≥ 10a.

We report a miniaturized spectrometer based on Hadamard transformation. The compact spectrometer utilizes a single-pixel photodetector and thus can operate at any wavelengths at relatively low cost. The spectrometer utilizes a MEMS-driven moving mask to encode the light intensity at its imaging slit, and the encoded light is then collected by a single-pixel detector. The light spectrum is recovered through an inverse Hadamard transform after a complete set of encoding is measured and recorded. The spectrometer is experimentally demonstrated with a spectral resolution better than 3 nm covering the full visible spectrum from 400 nm to 700 nm, and is capable of measuring over 200 spectra per second.

MEMS-based FTIR spectrometers are good candidates for handheld and IoT applications due to their high speed of operation, ultra-compact size and low cost. Light sources used for FTIR spectroscopy are usually limited to thermal light sources that continuously emit black body radiation. However, the use of pulsed sources has many advantages, such as reducing detector noise and enabling new kinds of spectroscopy measurements that depend on pulsed sources such as supercontinuum sources and non-linear infrared spectroscopy. The use of these pulsed sources with the high-speed MEMS is, thus, of great interest. In this work, we study the effect of using a pulsed IR source with a MEMS FTIR spectrometer on the obtained spectrum. The system is analyzed for different operation regimes from quasi-static to high-speed pulses for different duty cycles and repetition rates. Two measurement setups are used. The first involves using pulsed white light output from a thermal source with an optical chopper. The chopper frequency is changed from 20 Hz to 1 kHz at duty cycle values from 1% to 50%. The second setup uses an acousto-optic modulator to square-wave modulate the amplified spontaneous emission of a semiconductor optical amplifier with a repetition rate ranging from 20 Hz to 2 MHz and duty cycle values from 5% to 50%. Degradation in signal-to-noise ratio as well as spectral distortion are analyzed for different regimes of operation.

In this paper, we report a new electromagnetically-driven two-axis water-immersible scanning mirror with single inductor coil actuator. By making the resonance frequencies significantly different, the scanning motion of the two axes can be decoupled due to the dynamic structural filtering effect. For verification, a prototype micro scanning mirror was designed, fabricated and tested. The resonance frequencies of the fast and slow axes in air and water were determined to be 720/72 Hz and 690/55 Hz, respectively. The optical tilting angle of both fast and slow axes at the resonance frequencies was characterized, which shows good linearity with the amplitude of the driving current. With both axes driven simultaneously at frequencies close to their resonance, stable and repeatable 2D raster scanning was successfully achieved in both air and water, respectively. 2D B-mode ultrasound microscopy was also demonstrated by using this micro scanning mirror.

Various scanning applications like LIDAR sensors, OCT systems and laser projectors require a repeated periodic linear scanning trajectory performed by a quasi-static micro mirror. Since most MOEMS systems have inherent nonlinearities like a progressive spring stiffness and the quadratic voltage-deflection-relation of electrostatic drives, a nonlinear control scheme as presented in our previous paper significantly reduces parasitic oscillations of the resonance frequency and enables a high resolution raster scan combining a quasi-static axis with a cardanic mounted resonant axis. In this paper we address a novel control scheme using a flatness-based feedback control enhanced by a plug-in repetitive controller for the linear scanning axis. We demonstrate the applicability of this feedback control for a quasi-static moving micro mirror with electrostatic staggered vertical comb drives using a microcontroller-based driver. On-chip piezoresistive sensors serve as position feedback. We compare different scan trajectories and repetition rates with respect to the linearity and repeatability showing the robustness of the proposed control regime. Furthermore we discuss the advantage of this method to reduce the individual chip characterization for ramping up mass production.

We introduce Capacitive Micromachined Optical Focusing (CMOF) MEMS consisting of a miniature circular mirrored-membrane which can be electrostatically actuated to change mirror curvature. The central deflection zone is a close approximation to a parabolic mirror. The device is fabricated with minimal membrane mass to be only slightly larger than a diffraction-limited focus of a Gaussian beam. This device is a good candidate for fast tuning of the radius of curvature of laser beams at greater than MHz tuning rates, a feat difficult to achieve with current technologies. We present the design, modeling, and fabrication of a high-speed focusing CMOF MEMS platform. We have developed an equivalent circuit model for CMOFs which is capable of full nonlinear analyze of the CMOFs, and it is validated by ANSYS finite element method (FEM) simulations. By using the equivalent circuit model the non-linear transient response of a CMOF can be rapidly obtained and controlled with nonlinear control systems. The first generation of the proposed device is fabricated with a sacrificial-release process. Fabricated CMOFs have a silicon nitride membrane with 32um radius and 300nm gap spacing between top and bottom electrode. These CMOFs can effectively change their focal length from infinity to 3mm. We tested the device in an optical lens-assembly, and recorded 1mm focal point change by only 100nm deflection on the CMOF surface as measured using a Shack-Hartman wavefront sensor.

Gimbal-less dual axis point-to-point (quasistatic) MEMS mirrors have very wide bandwidths for laser beam steering, however users are often limited to only a third of the bandwidth due to the high Q-factor and use of low-pass filters in open-loop operation to avoid overshoot and oscillation. Closed-loop driving enables the use of the full bandwidth with additional complexity in optics and electronics, which can be undesirable in some low SWaP-C systems. But for many applications which require scanning repetitive patterns, such as LiDAR and biomedical imaging, bandwidth utilization and linearity can be greatly increased without any real-time feedback control by training the device and finding an optimal driving waveform using an iterative learning algorithm.

The algorithm drives the device with a trial waveform, measures the scan on a Position Sensing Device (PSD), calculates the error between the desired waveform and the measured position, and adjusts the drive waveform for the next iteration based on an approximate linear device model. This is repeated until the error is reduced to below an acceptable specification. The waveform is then saved in the MEMS Controller and can be reliably used for extended periods of operation. Multiple such drive signals can be trained and stored on the controller to perform different types of scans.

Several MEMS mirrors, including single- and dual-axis designs, were studied and three are reported here. Overall, in all cases a high accuracy of optical scans is achieved, typically to within ±0.025° of nominal. Repeatability after training, then running in open loop is better than ±0.01° - however, this measurement was limited by the lower resolution of the position detecting sensor. Scan rates achieved vary based on mirror design, but in each case are greatly improved from those achievable with basic driving approaches. Each mirror demonstrated higher quality vector graphics content at faster refresh rates and stable linear rasters at rates below resonance where lines are scanned with uniform velocity. Additionally, each mirror could achieve stable fast rasters with the line-scanning axis rates just below resonance, giving sinusoidal scans with line rates of ~1.6f_res. Finally, each mirror was also demonstrated achieving rasters with rates above resonance, giving line rates of ~2.5f_res. In all of those cases the other axis could scan linear and sharp sawtooth or triangle waveforms. Based on the symmetry of the MEMS design, we demonstrated the same performance at ddegerent angles, e.g. rastering at a 45° angle.

We present the design for a far-UV integral field spectrograph for astronomy enabled by two-axis digital micromirror arrays. Techniques used for integral field spectroscopy in the Optical-IR bandpass either do not apply to the far-UV due to low material transmission, or have other UV-specific challenges. In order to circumvent this limitation, we have designed an all-reflective method of dynamically reformatting the focal plane of a telescope with micro-opto-electro-mechanical systems (MOEMS). The Adaptive Micromirror Array Demonstration Experiment for Ultraviolet Spectroscopy (AMADEUS) is a benchtop far-UV/Optical spectrograph designed to demonstrate that the stability, repeatability, and scattered light contamination are all sufficiently controlable to use these devices in a high sensitivity astronomical instrument. The use of MOEMS devices enables the focal plane mapping to be reconfigured at will, providing some field sampling and path length control advantages relative to conventional Optical/IR techniques for integral field spectroscopy. We report on the design of AMADEUS and present a spectrograph concept for a future sub-orbital mission.

Tunable finesse optical filters and resonators are required for some applications when the signal-to-noise ratio and spectral resolution are traded-off to optimize the system performance. They can be used as well to control the amount of energy stored inside the resonator that can be used for optical trapping and atomistic studies. In this work we report a tunable finesse optical MEMS filter in deeply-etched SOI technology. The structure is composed of an optical cavity formed between a multilayer dielectric-coated optical fiber and slotted micromirror, attached to a comb-drive actuator. The cavity length between the multilayer Bragg coated fiber and the slotted micromirror is constant, while the slit width is being varied. The slit width is controlled by the applied voltage on the actuator. Changing the slit width modulates the reflectivity of the micromirror; and hence the finesse of the optical cavity. The obtained finesse is tuned by a factor of 5 across the band of 1330 nm and 1550 nm.

Electrowetting is a phenomenon that controls the surface tension of droplets by electricity and changes the wettability of the droplets. There are many applications of electrowetting, such as tunable liquid lenses, electronic paper and 3D display. Response time of electrowetting applications is important for them, but the relationship between response time and the physical parameters for electrowetting operation has not been deeply investigated. Therefore, we have investigated the effects of physical properties such as viscosity, interfacial tension and substrate roughness on the response time in AC electrowetting and found the optimal conditions for fast electrowetting. Also, an electrowetting circular lens was fabricated based on the optimal conditions and compared to a conventional electrowetting circular lens for response time. The experiment was conducted on a 0.4 mm thick aluminum plate with a 1μm thin parylene C film deposited with a 50 nm Teflon coating. The experiment results showed that the fastest response time is obtained at 5 mPa∙s conducting liquid (water-glycerol mixture) with 0 wt % SDS (sodium dodecyl sulfate) on default aluminum plate (RMS roughness 270 nm). Through this experiment, it was possible to control the spreading response pattern of electrowetting from under-damped response to over-damped response by changing the conditions of viscosity of conducting liquid, surface tension between two immiscible liquids, and substrate roughness. Also, a critical damping response was implemented using a hardware method by applying the optimum condition without voltage shape variation technology.

The use of electronic Relative Humidity (RH) sensors is widespread. However, when spark-free methods in explosive areas are needed optical RH methods could be employed. Here we present the application of the Mach-Zehnder (MZ) interferometer to study the response of thin films to changes in RH. These films could be used as the sensor element in RH instruments. As an example three types of films have been studied: poly(vinyl alcohol), an Interpenetrated Polymer Hydrogel (IPH) and gelatin. The configuration to study the polymer’s response consists of a climatic chamber where the MZ interferometer is immersed. The thin film is inserted in one arm. When humidity or water vapor increases the film thickness increases and its refractive index decreases. These phenomena will cause the shifting or lateral movement of the interference pattern. By sampling the interference pattern with a fixed point sensor it is possible to find a plot relating light intensity as a function of RH. These plots characterize the material. Several thin films parameters have been studied like Molecular Weight (MW) of poly(vinyl alcohol); thicknesses, hardness, and polymer ratio of an IPH and finally gelatin hardness.

Micro-opto-mechanical pressure sensors (MOMPS) based on integrated optical Mach-Zehnder interferometers (MZI) have been fabricated at IMEC, exhibiting much improved sensitivity and noise performance compared to their piezoelectric and capacitive counterparts. However, the design of next generation MOMPS systems on chip still remains uncertain due to the intrinsic multiphysics nature covering mechanical, optical and electrical phenomena. For this reason, we present a sophisticated, flexible and customizable algorithmic tool for the multiphysics simulation and design of highperformance MOMPS systems on chip, including mechanical and optical effects as well as the electronic circuitry for the readout. Furthermore, static and dynamic operating regimes are analyzed, also comparing analytical solutions with experimental results and demonstrating a good agreement. Finally, system noise contributions generated by the optoelectronic components and readout electronics are calculated and a static sensitivity of 8 mV/Pa is measured in the fabricated sensors.