This PDF file contains the front matter associated with SPIE Proceedings Volume 11293, including the Title Page, Copyright Information, Table of Contents, Author and Conference Committee lists.

We developed a novel 512 x 320 tip-tilt micro mirror array (MMA) together with the entire related technology platform, including mirror fabrication process, integrated CMOS address circuitry and external drive electronics. The MMA itself consists of 2axis-tip-tilt actuators at 48μm pixel size, allowing a continuous pure tip-tilt motion up to 3.5° in arbitrary directions, fully calibratable at standard deviations of better than 0.025°. The mirrors are realized within a 2-level architecture defined by three structural layers, two for hinge and reinforcement suspension and one for the overlying mirror. They are fabricated by surface-micromachining within a fully CMOS compatible process. MMA programming is accomplished by an underlying CMOS backplane supporting drive voltages up to 27V and frame rates up to 3.6kHz.

Rapid 3D optical scanning of points or patterned light is widely employed across applications in microscopy, material processing, adaptive optics and surveying. Despite this broadness in applicability, embodiments of 3D scanning tools may vary considerably as a result of the specific performance needs of each application. We present here a micromirror arraybased modular framework for the systemic design of such high-speed scanning tools. Our framework combines a semicustom commercial fabrication process with a comprehensive simulation pipeline in order to optimally reconfigure pixel wiring schemes across specific applications for the efficient allocation of available degrees of freedom. As a demonstration of this framework and to address existing bottlenecks in axial focusing, we produced a 32-ring concentric micromirror array capable of performing random-access focusing for wavelengths of up to 1040 nm at a response rate of 8.75 kHz. By partitioning the rings into electrostatically driven piston-mode pixels, we are able to operate the array through simple openloop 30 V drive, minimizing insertion complexity, and to ensure stable operation by preventing torsional failure and curling from stress. Furthermore, by taking advantage of phase-wrapping and the 32 degrees of freedom afforded by the number of independently addressable rings, we achieve good axial resolvability across the tool’s operating range with an axial fullwidth- half-maximum to range ratio of 3.5% as well as the ability to address focus depth-dependent aberrations resulting from the optical system or sample under study.

In the previous work a quasi-static MEMS mirror with a novel design and powerful piezoelectric driving material of AlScN was shown, which possesses large mechanical tilt angles of up to ±12.5°, high frequency of about 1 kHz, high fill-factor (aperture diameter is 0.8 mm and die size is 1.3 x 1.1 mm²), great long-term stability and great linearity. Further developments have been done for improving the material properties of AlScN, moreover, to integrate the mirror plate onto actuators by BEOL bonding process instead of hybrid assembly, since for the high fill-factor and good mechanical linearity the mirror plate and actuators are on different planes. Additionally, a third wafer of TSV wafer is used for the vertical electrical contacts. This unique technology includes not only triple-wafers-bonding, after which the wafer stacks also have to withstand grinding and pattering via DRIE. This paper shows the process efforts for realizing the triple-wafer-stack and discusses the technological challenges and also achieved results.

This paper presents a 2D MEMS mirror for smart headlights, combing high-Q vacuum package with AR (Anti Reflecting)-coating, piezoelectric driving and Lissajous scanning. While the vacuum package protects the MEMS device and the AR-coating suppresses parasite reflections from the glass lid, the AlN-based piezoelectric actuators are robust against shock and vibration in harsh environment, comparing to fragile capacitive finger structures. This gimbal-less MEMS mirror with a large circular aperture (diameter = 5.5 mm) utilizes Lissajous scanning possessing two perpendicular torsion modes with frequencies of f_x = 2.26 kHz, f_y = 2.30 kHz fulfilling high light density and large total optical scanning angles of 55°, 30° at ± 40 V_AC. A 2D projection of 50° x 20° was realized, where the angle loss comparing to the 1D testing arose from pincushion distortion, whose effect was severely reduced by the redesign run. Due to the great long-term stability of AlN and protection of vacuum packages, the MEMS mirror also shows a good reliability. This paper will describe and discuss the design, fabrication and characterization results of this MEMS mirror.

Novel research focuses on the use of micro scanning mirrors in mobile applications like automotive LiDAR sensors, head-mounted displays or portable micro beamer. Even under normal conditions, micro scanners are exposed to considerable environmental influences. Particularly disturbances such as shock, vibration and temperature fluctuations are relevant for miniaturized scanning systems. In this publication we show the critical environmental parameters for quasi-static micro mirrors with a staggered vertical comb drive intended for high-precision trajectory tracking control. Scanners are controlled based on a piezo-resistive position sensor feedback. Focus will be experimental shock and vibration analysis by exposure to sinusoidal and wide-band random vibration excitation as typical for automotive industry specifications. These are the most demanding requirements compared with other application fields of MEMS mirrors. The on-chip piezo-resistive sensor enables evaluation of the vibration load on the micro scanner, without any optical measurement setup. MEMS mirrors are mounted on a shaker system for characterization and are attached to a vehicle body to evaluate a real application scenario. Furthermore the performance in open-loop and closed-loop control mode is analyzed and shows very good applicability of micro scanners in an automotive environment.

Presented here is the world’s first resonant 1D MEMS mirror achieving mechanical scanning angles exceeding ±45° and thus providing a field of view of up to 180°. The MEMS scanner features a 2 mm x 4 mm ellipsoid mirror plate and oscillates at a scan frequency of about 1.5 kHz. Integrated sensors and closed-loop control allow for an accurate position detection below 0.1°. To achieve the scan angles as well as to guarantee long lifetime and reliability, the MEMS mirror is hermetically sealed on wafer level by a dedicated glass cover and operated in vacuum.

LiDAR systems in applications such as autonomous mobile robots, drones, vehicles, and other commercial applications that demand compact, low-cost, and dynamic scanning will inevitably turn to MEMS mirrors as the beam-steering component. Beam scanning-based LiDAR architectures have a significant advantage as the full power and attention of the sensor is given sequentially to each point (voxel) in the scan. Competitive LiDAR designs typically utilize scanning and are differentiated by their scanning architecture and the specific hardware utilized, with the general goal of moving away from bulky mechanical and motor-based systems and toward compact silicon-based MEMS technology.

Both single-axis and dual-axis MEMS mirrors are employed to enable two-dimensional (2D LiDAR) and three dimensional (3D LiDAR) point cloud sensing, respectively. The underlying time-of-flight sensor can be generic – a laser rangefinder or single-point LiDAR, with any typical wavelength or sensing method (pulsed ToF, AMCW, FMCW, etc.). The sensor is arranged with scanning elements which brings forth challenging trade-offs, discussed here. Architectures differ in whether transmitter and receiver are arranged coaxially or biaxially, each with its advantages and disadvantages. We present a hybrid architecture, Synchronized MEMS Pair LiDAR (SyMPL), which simplifies the coaxial design significantly and increases its efficiency by removing any beam splitting components or beam dumps. Multiple prototype LiDARs are compared and evaluated on the basis of SNR, scan speed, robustness to shock and vibration, eye safety, and resilience to mutual interference and echo signals. The work discusses the varying impacts on manufacturing and cost for applications demanding large volumes of LiDAR systems.

External cavity diode lasers (ECDLs) are a well-established laboratory tool due to their excellent emission properties. However, if the ECDLs are used outside the laboratory, they have limitations in terms of tuning speed and robustness. For overcoming these limitations, we developed a new micro-electro-mechanical system (MEMS) based ECDL cavity concept. The 1D MEMS actuator defines the angle of incidence at the diffraction grating as well as the cavity length of the ECDL. Due to the high resonance frequency of the MEMS actuator in the kHz range, the switching speed of the ECDL emission wavelength is drastically reduced. Furthermore, the MEMS actuator minimizes the sensitivity to external disturbance which opens a path to handheld wide mode-hop free tunable ECDLs in the near future. Therefore we have also optimized our curved waveguide concept based on GaSb for the ECDL design, whereby a wavelength range from NIR to the MIR range can be better covered. These features qualify the new developed MEMS tunable ECDL for the high demands of the high resolution multi-species molecular spectroscopy. Application examples of the MEMS based ECDL and the curved gain chips will be provided.

A recently introduced new CMOS compatible actuator class, called nano electrostatic drive (NED), uses electrostatic actuation to provide significant deflections of elastic structures. The behavior of such actuators can be dominated by nonlinear phenomena, if the nonlinearities are not understood and not considered in the design. One of the main nonlinearity sources is the electrostatic actuation, which results in the well-known instability named pull-in. Additionally, due to large deflections provided by NED technology, stress stiffening and large deformation significantly influence the system, shifting the eigenfrequencies, altering the pull-in voltage, or even introducing geometrical buckling. All these effects together characterize static and dynamic behavior and can be tailored to partially counterbalance each-other by specific designs. In following, we use finite element method (FEM) to analyze the static and dynamic behavior of MEMS based on NED technology. Owing to coupled-field FEM technique, we observe effects like static pull-in, electromechanical eigenfrequency shift and transient phenomena in detail. The numerical results are validated during optical experiments, which supports the conclusions arose from the FEM. Finally, characterizing of the nonlinearities grants the ability to tailor and minimize them during the MEMS design process.

We report a surface-engineered glass waveguide based optofluidic reactor system. Photocatalyst is coated on waveguide surfaces and is activated under light irradiation. In traditional design, light gradually spreads and diminishes along the waveguide, leading to non-uniform distribution of light energy. Here we present a method for modifying glass waveguide surfaces through gradient etching, to extend light transmission length and make light refraction more uniform. The effect of waveguide dimensions and etching patterns on the light refraction intensity profiles along transmission was examined. These waveguides with specially designed surfaces were applied in an optofluidic reactor for photocatalytically converting CO2 into fuels.

This work presents experimental and simulation results of a 3D measurement concept based on fiber-optic interference pattern generation. A demonstrator system which is able to adjust different optical and mechanical parameters is described. The results of parameter variation studies are discussed along with possible applications in the field of micro-optical 3D measurement systems like endoscopes. The experiments were prepared with different structures with various scattering properties. To implement that approach into a micro-optical 3D measurement system, the combination of distance variation between the fibers and a controlled phase shift introduced by a retarder can be used to design the system versatile.

This work presents a novel approach for generating a foveated image with a scanning laser. Foveated image is desired especially in near-eye displays such as AR/VR displays. No display system as of today could provide an image with a sufficiently high field of view while maintaining a retina level resolution around the desired fixation point. When projecting a foveated rasterized image one has to manipulate the density of pixels within a line and the density of the lines. Also, different pixels density usually creates different light intensity.

Usually, obtaining a foveated image is carried by super-imposing of at least two images, a low-resolution wide field of view with a high-resolution narrow field of view. This is normally done by combing two or more light sources or combing two display panels optically. In the presented work, a single light source is being used to project a foveated image. The system is based on a MEMS scanning mirror with a dedicated controller. Precise motion control of the mirror along with the presented method allows manipulating the location of each pixel. A pixel location is a timed light pulse synchronized with the mirror orientation. The algorithm times the pixels achieving a dense area of pixels around the desired fixation point and sparse area of pixels elsewhere. The pixels locations may vary for each frame. Moreover, compensation to the different light intensities within the frame is applied. The presented algorithm allows projecting a foveated image by a laser scanning without the tangle of sophisticated hardware.

Miniature lenses with tunable focus are essential components for many modern applications involving compact optical systems. In this work, a microscale Alvarez lens fabricated with the integration of microelectromechanical systems (MEMS) and metasurfaces is proposed. Electrical experiment results have proven the micropositioning ability of actuatable Alvarez metasurface platform with high controllability, showing a quadratic dependence of the actuated displacement on the driving voltage. The optical experiment results have verified the simulated possibility of focal tuning with the miniature Alvarez metasurface system. This MEMS-integrated Alvarez metasurface lens is capable to produce fast, precise and reproducible focus tuning with the fabrication process entirely compatible with CMOS technologies, granting it the potential to be integrated with other IC components to create full-function 3D display or sensing systems.

Miniaturized versions of nowadays tabletop setups will be necessary for a successful commercialization of quantum cryptography and computing. Within this contribution, we present a concept for downsizing the Hanbury Brown-Twiss configuration. The design is based on optical simulations, with the aim of finding the best compromise of detection efficiency and level of miniaturization. Since scattering effects are important for evaluating the system’s performance, a complete scattering analysis got performed.

In this work we report on combining MEMS Michelson interferometer core engine cascaded with a low finesse Fabry-Perot (FP) tunable filter to enhance the spectral resolution over a wide spectral range. In this scheme, the different FP longitudinal modes within the FTIR spectrometer range are utilized simultaneously to scan the spectrum of the measured material by tuning the filter, while the FTIR engine discriminates between the contributions of the different FP modes; given that the spectral resolution of the FTIR engine is smaller than the FSR of the FP. The presented scheme is implemented experimentally using a FP cavity which is finely tuned using piezo actuator, with a scanning MEMS Michelson interferometer achieving a resolution of 16 nm at 1550 nm. The system is used to resolve two laser lines at 1548 nm and 1552 nm achieving a resolution of 4 nm at 1550 nm leading to four times enhancement. We also measured the absorption lines of a references material in the wavelength range of 1450 nm to 1750 nm and compared it to the measurement of a bench top spectrometer and the two results are in close agreement

A miniaturized version of a light-sheet microscopy (LSM) system, with 3D imaging enabled through active optical control, is presented. Even though the field of LSM technology has advanced significantly in recent years, it is still not considered an easily available technique. This is mainly due to its cost compared to epifluorescence setups and the requirement for specific sample mounting techniques in most cases, as well as stringent optical alignment and difficulty to reduce motion artifacts when the sample is moved through the light path to create the imaging slices. In our research, we demonstrate a miniaturized version of an LSM that can reduce size and cost, and is able to achieve 3D imaging through control of multiple active optical elements and MEMS micromirrors used in both the illumination and imaging path instead of moving the sample. The laser excitation is controlled and shaped via multiple MEMS elements for 3D beam position control and multi-lens beam shaping to generate a 2.85 μm wide light-sheet with controllable height of up to 550 μm, and orthogonal positioning over a 200 μm range. Additionally, the focal point of the excitation can be shifted along the laser propagation direction by 200 μm. The orthogonally positioned imaging path incorporates a x20, NA = 0.4 objective and a tunable lens for imaging selected focal planes synchronized with the excitation positioning. The imaging results show sub-micron resolution with a field-of-view of 400 μm x 300 μm. The synchronization of the two active elements allows for fast imaging of different slices of a sample and promises convenient 3D reconstruction and representation of cell tissue.

In this paper, we present a single-pixel hyperspectral imager based on Hadamard transformat ion. The imager uses a micromirror array and a resonant scanning mirror to implement spatial and spectral encoding. For a proof of concept, the sensing wavelength of the imager is 450nm to 750nm, but it can easily be applied to the infrared wavelengths. It has high robustness and high frame rate compared with conventional single-pixel hyperspectral imagers. We also introduce a cascading method that can enhance the spatial resolution of the single-pixel hyperspectral imager. Some experimental results are presented in the paper to demonstrate the performance of our proposed system.

We present a miniaturized actuator for volumetric tissue imaging. The device consists of a hydraulically actuated accordion-like part for axial scanning (focus adjustment), and an electromagnetically actuated 2D scanner for lateral scanning. The device is manufactured using selective laser sintering, allowing for very low cost and rapid production. We demonstrate 3D scanning capability through observing the lateral scan pattern at different axial locations with a CMOS camera, and through scanning of a multi-layered phantom. We further investigate reliability of the electromagnetically actuated lateral scanner, as well as the hysteresis behavior of the hydraulic scanner.

Passively levitating pyrolytic graphite (PyG) milli-robots can be controlled optically due to the thermal dependence of PyG’s magnetic susceptibility and optically induced, localized temperature changes. A combination of projector technology and optically absorbent coatings is proposed to address the challenge of simultaneous parallel control of levitating PyG milli-robots. Experimental results demonstrate successful parallel control using commercially available projector technology. Experimental actuation responses show marginal ability of absorbent coatings to increase PyG robot maximum actuation speed as well as reduce minimum controllable robot size under fixed optical power density constraints. While enhanced optical absorption opens opportunities for system miniaturization and extension to device-level magneto-optic actuators, doing so with minimal impact to levitating properties in a highly thermally conductive material remains a challenge.

Handheld spectrometers are gaining attention due to their growing market. The customers seek to analyze their own samples with good accuracy and reasonable cost. Therefore, the spectrometer manufacturers miniaturize their products and reduce their cost. However, this leads to decreased spectral resolution and optical throughput rendering the task of the identifying closely spaced spectral lines challenging. In this work, we report the application of the compressive sensing (CS) techniques on a MEMS Fourier Transform Infrared spectrometer, for the sake of resolution enhancement based on the spectrum sparsity. The spectrometer wavelength range is 1300–2500 nm while its core engine is a micromachined scanning Michelson interferometer. The interferometer scanning mirror is driven by a MEMS electrostatic actuator with programmable travel range corresponding to two different resolutions of about 16 nm and 8 nm around 1550 nm. The CS algorithm is applied on filtered white light around a wavelength of 2000 nm fed to the spectrometer using multimode optical fiber and is found to enhance the resolving power down to 3 nm starting from the 22 nm resolution. Then the algorithm is applied on larger number of lines by superposing the spectral lines of a tuneable laser source around 1550 nm. The spacing between the spectral lines is varied and the reconstructed spectra by direct FFT and using the CS technique are compared. The CS technique shows overall better spectral resolution the efficiency of the technique is found to deteriorate as the number of spectral lines increases.

Emerging Near-InfraRed (NIR) spectroscopic applications such as biomedical, agrofood, health & beauty and in-line industrial applications require compact and low-cost miniaturized spectrometers. One of the main elements for such devices is the wideband light source, which can be ultimately in the form of an integrated source. In this work, we report a Multi-Walled Carbon Nanotubes (MWCNTs) NIR source for operation with a micro-electro-mechanical system (MEMS) FTIR spectrometer. The source consists of joule micro heater machined on a highly doped silicon substrate, where the heater surrounds an active area. The micro heater is made of a platinum film sputtered on silicon with a thin titanium layer used as an adhesion layer. The chips are singulated then the MWCNTs are plotted in the active area. The SonoPlot® Microplotter II is used to plot a multi-layered 4x4 mm² MWCNTs thin film with a layer thickness of about 1μm in the active area. A voltage difference is applied to the designated pads on the chip, allowing uniform heating of the square area containing the MWCNTs. The MEMS FTIR spectrometer is used to measure the emitted power spectral density (PSD) from the source with and without the plotting of the MWCNTs thin film. The micro-plotting of the MWCNTs over the silicon substrate improved the PSD recorded by the spectrometer. The reported results show that an engineered light source based on MWCNTs and silicon serves as a good candidate for miniaturized spectrometers.

In this work, we investigate the optical reflectivity of deeply etched vertical mirrors using the effective medium approximation and the transfer matrix method. The reflectivity is studied versus the incident light wavelength for different metal film thickness ranging from 10 nm to 200 nm, grain to air volume ratio (or fill factor) ranging from 10 % to 100 %, and for 1, 2 or 3 effective metallic layers with different grain size. The model predicts that the reflectivity of the vertical mirror can be about 55% of its nominal expected value of the bulk metal reflectivity for a fill factor of 35% and a film thickness of 24 nm, which is equal to 4 times the skin depth at a wavelength of 1550 nm. A vertical mirror is etched and metallized on a silicon-on-insulator (SOI) wafer and its reflectivity is measured in the wavelength range of 1300 nm to 2100 nm, showing good agreement with the theoretical predictions.

In this work, we present a MEMS-based ATR FTIR spectrometer operating in the wavelength range of 1.8 μm to 6.8 μm. The core engine of the spectrometer is a monolithically integrated scanning Michelson interferometer on a silicon chip. The ATR crystal is illuminated with an IR source and the output light of the crystal is free-space coupled to the MEMS interferometer using micro-optics reflective mirrors and the modulated light from the interferometer is then coupled to an MCT photodetector. The recorded SNR of the spectrometer is about 1000:1 in 10 seconds measurement time with a spectral resolution of 66 cm^-1. The spectra of different liquid samples were obtained and the effect of the ATR crystal refractive index on the absorption depth was investigated, showing good agreement with the theoretical model. The proposed miniaturized ATR MEMS spectrometer opens the door for various applications in oil analysis, food safety and health care among others.

The electromechanical actuation of two silicon nitride membranes forming a monolithic MOEMS is investigated. By controlling the tensile stress of the high quality membranes via a piezoelectrically controlled compressive force applied to the chip we demonstrate tuning of their mechanical spectrum, as well as strong intermode electromechanical coupling. Piezoelectric actuation is shown to enhance the nonlinear response of the membranes, which is evidenced by parametric amplification of the thermal fluctuations. Such a MOEMS array represents an attractive tunable and versatile platform for optomechanics and sensing applications.

We present and discuss the infrared properties of molybdenum silicide thin films, molybdenum silicide photonic crystals and the electromigration of molybdenum silicide. Magnetronsputtered and annealed molybdenum silicide layers were investigated via infrared spectral ellipsometry. Simulations of optical properties of molybdenum silicide photonic crystals [metal-insulator-metal structures] show that properties influenced by the size of the structures differ to those of widely used photonic crystals made of Ag. The infrared absorption of MIM-structures comprising of a solid molybdenum silicide layer and one molybdenum silicide layer in form of disks were simulated for different disk diameters and layer thicknesses. A first maximum of absorption (at about 2740 nm) is almost independent of the diameter of the molybdenum silicide disk. A second maximum of absorption (7120 nm -7750 nm) shows an increase of its resonance wavelength with increasing disk diameter. A third maximum of absorption (at about 11000nm) instead shows a respective decrease. In the simulations the thicknesses of the metal layers and the dielectric layer were varied. Changes in the thickness of the dielectric layer caused greater changes in the absorption spectra than changes in the thicknesses of the metal layers. For the application in thermal emitters, the knowledge of electromigration properties of molybdenum silicide layers is crucial. Investigations via accelerated tests with different acceleration factors are demonstrated for test structures. We investigated structures based on molybdenum silicide and for comparison with a well known system analogous structures made of aluminum. We find that molybdenum silicide shows considerably lower electromigration than aluminium.

This article presents the design and system integration of a hybrid MEMS scanner array (MSM) developed for a real time 3D imaging with a panoramic optical field of view (FOV) of 360° × 60° (horizontal × vertical). The pulsed ToF LiDAR system targets on a distance measurement range of 100 m with a video-like frame rate of 10 Hz. The fast vertical scan axis is realized by a synchronous scanning MSM array with large receiver aperture. It increases the scanning rate to 3200 Hz, which is four times faster in comparison to state-of-the-art fast macroscopic polygon scanning systems used in actual LIDAR systems. A hybrid assembly of frequency selected scanner elements was chosen instead of a monolithic MEMS array to guaranty high yield of MEMS fabrication and a synchronous operation of all resonant MEMS elements at 1600 Hz with large FOV of 60°. The hybrid MSM array consists of a separate emitting mirror for laser scanning of the target and 22 reception elements resulting in a large reception aperture of D_eff = 23mm. All MSM are driven in parametric resonance to enable a fully synchronized operation of all individual MEMS scanner elements. Therefore, piezo-resistive position sensors are integrated inside the MEMS chip used for position feedback of driving control. The paper focus on the MEMS system integration including the synchronized operation of multiple MEMS scanning elements. It presents technical details to meet the narrow tolerance budgets for (i) micro assembly and (ii) synchronous driving of multiple MEMS scanner elements.