This PDF file contains the front matter associated with SPIE Proceedings Volume 8977, including the Title Page, Copyright information, Table of Contents, and Conference Committee listing.

We present two novel micro scanning mirrors with large aperture and HR dielectric coatings suitable for high power laser applications in a miniaturized laser-surgical instrument for neurosurgery to cut skull tissue. An electrostatic driven 2D-raster scanning mirror with 5x7.1mm aperture is used for dynamic steering of a ps-laser beam of the laser cutting process. A second magnetic 2D-beam steering mirror enables a static beam correction of a hand guided laser instrument. Optimizations of a magnetic gimbal micro mirror with 6 mm x 8 mm mirror plate are presented; here static deflections of 3° were reached. Both MEMS devices were successfully tested with a high power ps-laser at 532nm up to 20W average laser power.

This paper presents designs and fabrication process of two single-axis PZT micromirrors with 1 mm diameter and 1.4 mm × 4 mm apertures, whose frequencies are 60 kHz and 17 kHz, respectively. These micromirrors achieve large optical scan angles of about 40° driven by 10 V rectangular pulses and show high Q-factors of more than 1000. The investigation on the long-term stability of a PZT driven micromirror has detected more than 100 Billion cycles. The combined results of experimental diagnostics and FEM analyses give rise to new designs iteratively leading to a larger deflection and appropriate frequencies, which are currently fabricated.

Typical applications for resonantly driven vacuum packaged MEMS scanners including laser projection displays require a feedback signal for closed-loop operation as well as high accuracy angle synchronization for data processing. A well known and widely used method is based on determining the angular velocity of the oscillating micromirror by measuring the time derivative of a capacitance. In this work we analyze a capacitive sensing approach that uses integrated vertical comb structures to synchronize the angular motion of a torsional micromirror oscillating in resonance. The investigated measurement method is implemented in a laser display that generates a video projection by scanning a RBG laser beam. As the 2D-micromirror performs sinusoidal oscillations on both perpendicular axes a continuously moving Lissajous pattern is projected. By measuring the displacement current due to an angular deflection of the movable comb structures an appropriate feedback signal for actuation and data synchronization is computed. In order to estimate the angular deflection and velocity a mathematical model of the capacitive sensing system is presented. In particular, the nonlinear characteristic of the capacitance as a function of the angle that is calculated using FEM analysis is approximated using cubic splines. Combining this nonlinear function with a dynamic model of the micromirror oscillation and the analog electronics a mathematical model of the capacitive measurement system is derived. To evaluate the proposed model numerical simulations are realized using MATLAB/Simulink and are compared to experimental measurements.

In situ process information in the chemical, pharmaceutical or food industry as well as emission monitoring, sensitive trace detection and biological sensing applications would increasingly rely on MIR-spectroscopic anal­ysis in the 3 μm - 12 μm wavelength range. However, cost effective, portable, low power consuming and fast spectrometers with a wide tuning range are not available so far. To provide these MIR-spectrometer properties, the combination of quantum cascade lasers with a MOEMS scanning grating as wavelength selective element in the external cavity is addressed to provide a very compact and fast tunable laser source for spectroscopic analysis.

MEMS deformable mirrors are versatile elements for optical focus control. Electrostatic-pneumatic actuation of the mirrors offers relatively large membrane stroke to increase focus range. Moreover, this novel actuation method provides high speed focus control with either positive or negative focus. The speed of focusing is dependent on membrane tension, membrane size, air channel configuration, and the size of the backchamber. A 3 mm diameter mirror with 5 mm diameter actuator membrane achieves 30 kHz bandwidth with electrostatic actuation and 8 kHz bandwidth with pneumatic actuation. The settling time of the step response for both electrostatic and pneumatic actuation is approximately 100μs.

Hermetic wafer level packaging of optical MEMS scanning mirrors is essential for mass-market applications. It is the key to enable reliable low-cost mass producible scanning solutions. Vacuum packaging of resonant MEMS scanning mirrors widens the parameter range specifically with respect to scan angle and scan frequency. It also allows extending the utilizable range of mirror aperture size based on the fact that the energy of the high-Q oscillator can be effectively conserved and accumulated. But there are also some drawbacks associated with vacuum packaging. This paper discusses the different advantageous and disadvantageous aspects of vacuum packaging of MEMS scanning mirrors with respect to laser projection displays. Improved MEMS scanning mirror designs are being presented which focus on overcoming previous limitations. Finally an outlook is presented on the suitability of this technology for very large aperture scanning mirrors to be used in high power laser applications.

A new hybrid 3D finite-element/behavioral-modeling approach is presented that can be used to accurately predict the nonlinear dynamics (parametric resonance) in electrostatically driven 2D resonant MEMS scanning mirrors. We demonstrate new levels of accuracy and speed for thick SOI scanning mirrors with large scanning angles and validate the modeling approach against measurement on a previously fabricated scanning mirror. The modeling approach is fast and treats the design parameters as variables thus enabling rapid design iterations, automatic sensitivity and statistical yield analyses, and integration with system and circuit simulators for coupled MEMS-IC cosimulation.

A time-of-flight (TOF) based three dimensional (3D) image capturing system and its enhanced optical modulating device are presented. The 3D image capturing system includes 850nm IR emitter (typically compact Laser diodes) and high speed image modulator, so called optical shutter. The optical shutter consists of multi-layered optical resonance cavity and electro-absorptive layers. The optical shutter is a solid-state controllable filter which modulates the IR image to extract the phase delay due to TOF of the emitting IR light. This presentation especially addresses robustness issues and solutions when operated under practical environments such as ambient temperature variation and existence of strong ambient light (e.g. outdoors). The wavelength of laser diode varies substantially depending on the ambient temperature, which degrades the modulation efficiency. To get a robust operation, the bandwidth of transmittance of the optical shutter is drastically improved with a novel coupled Fabry-Perot resonance cavity design to come up with the wavelength variation of the laser diode. Also, to suppress the interference of solar irradiance to IR source signal, a novel driving scheme is applied, in which IR light and optical shutter modulation duties are timely localized, i. e. ‘bursted’. Suggested novel optical shutter design and burst driving scheme enable capturing of a full HD resolution of depth image under the realistic usage environments, which so far tackle the commercialization of TOF cameras. Design, fabrication, and evaluation of the optical shutter; and, 3D capturing system prototype, image test results are presented.

The concept for a hyperspectral imaging system using a Fabry-Perot tunable filter (FPTF) array that is fabricated using “miniature optical electrical mechanical system” (MOEMS) technology. [1] Using an array of FPTF as an approach to hyperspectral imaging relaxes wavelength tuning requirements considerably because of the reduced portion of the spectrum that is covered by each element in the array. In this paper, Pacific Advanced Technology and ARL present the results of a concept design and performed analysis of a MOEMS based tunable Fabry-Perot array (FPTF) to perform simultaneous multispectral and hyperspectral imaging with relatively high spatial resolution. The concept design was developed with support of an Army SBIR Phase I program The Fabry-Perot tunable MOEMS filter array was combined with a miniature optics array and a focal plane array of 1024 x 1024 pixels to produce 16 colors every frame of the camera. Each color image has a spatial resolution of 256 x 256 pixels with an IFOV of 1.7 mrads and FOV of 25 degrees. The spectral images are collected simultaneously allowing high resolution spectral-spatial-temporal information in each frame of the camera, thus enabling the implementation of spectral-temporal-spatial algorithms in real-time to provide high sensitivity for the detection of weak signals in a high clutter background environment with low sensitivity to camera motion. The challenge in the design was the independent actuation of each Fabry Perot element in the array allowing for individual tuning. An additional challenge was the need to maximize the fill factor to improve the spatial coverage with minimal dead space. This paper will only address the concept design and analysis of the Fabry-Perot tunable filter array. A previous paper presented at SPIE DSS in 2012 explained the design of the optical array.

A MEMS-FTIR engine has been developed as a key device for the Fourier-Transform Infrared Spectrometer, which consists of a Michelson interferometer including an electro-static actuator to control a moving mirror, an optical fiber groove for incident light and a photodetector. All these elements except for the photodetector are monolithically fabricated in Silicon using MEMS technology. The optical elements such as a beam splitter, a fixed mirror and a moving mirror are formed and aligned simultaneously with high degree of precision by Deep Reactive Ion Etching (DRIE). The vertical side walls are utilized as optical planes so that the incident light path is located in parallel with the Silicon substrate. The moving mirror is driven by an electro-static MEMS actuator. The photodetector is placed above an angled mirror, which is formed by alkaline wet etching exposing the Silicon crystal plane at the end position of light path. All the elements including the photodetector are hermetically covered by a lid of Silicon in the vacuum chamber by using a surface activate bonding technology. In order to reduce the cost, wafer level process and separation of each chip by a laser dicer after all assembly processes are introduced. The realized MEMS-FTIR is 10×17×1 mm in size and a signal noise ratio (SNR) of better than 35dB, which comes from a good verticality of less than 0.2 degree in the vertical side walls as optical planes by managing the DRIE etching conditions.

Mid infrared spectroscopy has been developed to a powerful and essential method of material analysis, with a steadily increasing number of industrial and scientific application fields. The so called spectral fingerprint range enables identification of chemical compounds by their unique spectral pattern. To provide a suitable miniaturized and portable MIR spectrometer solution at an affordable price, an existing MEMS NIR spectrometer module which already bases on micro system technology has been expanded in its wavelength range. The developed spectrometer belongs to the category of scanning grating spectrometers. Main component is a fast oscillating micro-mirror which moves sinusoidal with high mechanical precision enabling a high stability of according wavelength axis. This is supported by a highly precise optical tracking of the actual motion. Mono-crystalline silicon guarantees a long-life operation with no wear even under harsh environmental conditions. Spectral signal acquisition is realized by using a TE-cooled MCT single element detector assisted by low noise trans-impedance amplifier. With the help of integrated logic components a data pre-processing takes place, such as averaging, offset subtraction, detector transfer characteristic correction and noise shaping. Due the compact and flexible setup, the spectrometer is suitable for the use in various applications, such as process control in chemical industry, gas mixture analysis or liquid verification. The portability of the device opens up new application possibilities in mobile environment. The advances of the promising technology and its specific applications will be described in this paper. Advanced performance issues of the device be reviewed in detail.

We studied how a surface-micromachined Fabry-Perot interferometer, realized with Si / air-gap distributed Bragg reflectors, would perform at the middle-infrared wavelengths. Compared with traditional solid-film pairs, this Si-FPI technology features better index contrast, which enables wider stop band and potentially higher resolution. Four different designs of interferometers were prepared and compared. Two designs apply the solid-film reflectors of Si/SiO₂ structure. Their data is exploited as a reference of a middle-infrared interferometer and, as a template for mapping the performance from the simulation results to the measured data. The third design operates at the thermal infrared and it was our first embodiment with the Si/air-gap mirrors. The performance, reported earlier, is here referred to for estimating the technology scalability down to shorter wavelengths. Finally, we realized a non-tunable proof-of-concept version of the Si/air-gap technology for middle infrared. The measured data is mapped into an estimate of the achievable performance of a tunable version. We present the transmission and resolution data and argument the simulation models that reproduce the data. The prediction for the tunable middle-infrared Si-FPI is then presented. The results indicate that such a device is expected to have two-fold better resolution and a clearly wider stop band, compared with the prior art.

Optical phased arrays (OPAs) with fast response time are of great interest for various applications such as displays, free space optical communications, and lidar. Existing liquid crystal OPAs have millisecond response time and small beam steering angle. Here, we report on a novel 32×32 MEMS OPA with fast response time (<4 microseconds), large field of view (±2°), and narrow beam divergence (0.1°). The OPA is composed of high-contrast grating (HCG) mirrors which function as phase shifters. Relative to beam steering systems based on a single rotating MEMS mirror, which are typically limited to bandwidths below 50 kHz, the MEMS OPA described here has the advantage of greatly reduced mass and therefore achieves a bandwidth over 500 kHz. The OPA is fabricated using deep UV lithography to create submicron mechanical springs and electrical interconnects, enabling a high (85%) fill-factor. Each HCG mirror is composed of only a single layer of polysilicon and achieves >99% reflectivity through the use of a subwavelength grating patterned into the mirror’s polysilicon surface. Conventional metal-coated MEMS mirrors must be thick (1- 50 μm) to prevent warpage arising from thermal and residual stress. The single material construction used here results in a high degree of flatness even in a thin 400 nm HCG mirror. Beam steering is demonstrated using binary phase patterns and is accomplished with the help of a closed-loop phase control system based on a phase-shifting interferometer that provides in-situ measurement of the phase shift of each mirror in the array.

In this paper, we introduce a floating plasmonic absorber having multiple resonances in the 8 ~ 14 μm spectral range and broadband absorption characteristics by adjusting Drude relaxation rate of metal. This plasmonic broadband resonator capable of capturing light with a large optical cross-section area is able to substantially enhance the performance of micro-bolometer (response time, noise equivalent temperature difference, pixel size and so on) due to the significantly reduced thermal mass and conductance. Firstly, to adjust Drude relaxation rate, the mean crystalline size of metal was optimized by changing the deposition condition and the absorption characteristics of absorber were measured by Fourier transform infrared spectroscopy in the 8 ~ 14 μm spectral range. The measurement results show that 1.62 times of broadening in bandwidth was obtained by decreasing the crystalline size from 5.73 nm to 3.18 nm while maintaining the maximum absorption at resonant wavelength of 10 μm within 93 ~ 95%. Comparisons between measurements and CST microwave studio simulations show similar spectral absorption trends. And then, to integrate plasmonic absorber with micro-bolometer, various kinds of plasmonic absorbers which have combinations of short and long dipole resonators were designed and simulated. Based on these results, 12 μm micro-bolometer pixels integrated with plasmonic broadband Ti absorber are designed and fabricated. The optimized Ti resonators with multiple resonance and small crystalline size absorb 88 % of the unpolarized radiation in the 8 ~ 14 μm spectral range on the average.

We demonstrate light collimation of single-mode optical fibers using deeply-etched three-dimensional curved micromirror on silicon chip. The three-dimensional curvature of the mirror is controlled by a process combining deep reactive ion etching and isotropic etching of silicon. The produced surface is astigmatic with out-of-plane radius of curvature that is about one half the in-plane radius of curvature. Having a 300-μm in-plane radius and incident beam inplane inclined with an angle of 45 degrees with respect to the principal axis, the reflected beam is maintained stigmatic with about 4.25 times reduction in the beam expansion angle in free space and about 12-dB reduction in propagation losses, when received by a limited-aperture detector.

In this paper, the analog to electromagnetically induced transparency (EIT) in the double-coupled one-dimensional photonic crystal cavities are proposed and experimentally observed. This EIT-like effect is due to the interference of two resonance modes and the leaky propagation mode. A nanoelectromechanical systems (NEMS) comb drive is used to align the two resonant wavelengths up, which is first used in the studies of the EIT-like effect. The fabrication of the device bases on the standard semiconductor process. Finally, the evolution of the EIT-like transmission spectrum with the applied voltages is shown in the last part of this paper.

In this paper, we demonstrate a configuration of optical force actuator based on coupled one-dimensional photonic crystal cavities (1D PCCs). A NEMS structure, which consists of 3 cascaded folded-beam-springs and an electrostatic comb drive, is integrated into the device to finely tune the gap between cavities so that the relation between the cavities’ resonance shift and their gap changes can be precisely and straightforwardly characterized. Resonance modes of the cavities are utilized to drive the spring structures, which can generate much larger optical forces than waveguide modes due to their high quality factors. The even resonance mode produces an attractive force, while the odd mode produces a repulsive force. In addition, there is the thermo-optic effect accompanying with the optical forces. Here, a decoupling method is also introduced by calibrating the relations of resonance shift versus gap change with the help of the NEMS and resonance shift versus temperature variation in advance. The experimental results show that one cavity is pulled to (pushed away from) the other cavity by 37.1 nm (11.4 nm) for the optomechanical actuator proposed here. This kind of optical actuator has the potential applications of all-optical circuits in future communication and sensing systems.

A new design for bi-material microbeams is presented in this paper which enables the tuning of their thermal actuation response to deliver out-of-plane rotation . The design is applied to a group of 300 μm long and 20 μm wide gold-over-polysilicon microbeams with a 60 μm long top gold strip positioned in different locations along the beam length. Numerical simulation predicts that if the gold strip is situated 20 μm from one end of the microbeam, a maximum out-of- plane rotation angle of 0.9 degree can be achieved with a temperature increase of 150 °C. Thermal loading experiments carried out on fabricated similar microbeams show similar responses to those predicted by finite element simulations.

We demonstrate a holographic image reconstructed by a FPD-based complex spatial light modulator (SLM) which is composed of a phase-only SLM and a sheet of beam combiner. A complex SLM which modulates both amplitude and phase independently is necessary for a better image quality with reducing conjugate images. The two-phase encoding method is one of the most practical candidates for the complex SLM. The proposed complex SLM is presented in a phase-only LCD panel which can be manufactured in a conventional LCD process and it was used for generating different phases. The PAL (Parallel-Aligned nematic Liquid crystal) mode is used to modulate the phase without the amplitude change. The film-type beam combiner consists of a prism array and a grating made by a conventional fabrication process. The beam combiner plays a vital role to merge two pixels and to adjust effective complex modulation. In this paper, the holographic image by the proposed complex SLM is verified by the experimental and simulation work in a monochromatic reconstruction. This complex SLM can be scaled up and it is a promising candidate SLM for a large-size holographic 3D display.

Fraunhofer IPMS has developed a one-dimensional high-speed spatial light modulator in cooperation with Micronic Mydata AB. This SLM is the core element of the Swedish company’s new LDI 5sp series of Laser-Direct-Imaging systems optimized for processing of advanced substrates for semiconductor packaging. This paper reports on design, technology, characterization and application results of the new SLM. With a resolution of 8192 pixels that can be modulated in the MHz range and the capability to generate intensity gray-levels instantly without time multiplexing, the SLM is applicable also in many other fields, wherever modulation of ultraviolet light needs to be combined with high throughput and high precision.

MEMS-scanning laser projector have seen tremendous performance improvements in the past year, demonstrating devices with very good performances in terms of size, energy efficiency and image quality that were expected from the theory point of view. The last challenge that was not solved yet is the speckle reduction, which is the main bottleneck for this technology adoption. The paper presents an innovative design to reduce speckle contrast without degrading any other features and benefits of the projection system. The proposed despeckling solution is a single, non-movable part with less than 0.1cc in volume and of 4mm in thickness.

Multi-object spectroscopy (MOS) is a powerful tool for space and ground-based telescopes for the study of the formation and evolution of galaxies. This technique requires a programmable slit mask for astronomical object selection. We are engaged in a European development of micromirror arrays (MMA) for generating reflective slit masks in future MOS, called MIRA. MMA with 100 × 200 μm² single-crystal silicon micromirrors were successfully designed, fabricated and tested. Arrays are composed of 2048 micromirrors (32 x 64) with a peak-to-valley deformation less than 10 nm, a tilt angle of 24° for an actuation voltage of 130 V. The micromirrors were actuated successfully before, during and after cryogenic cooling, down to 162K. The micromirror surface deformation was measured at cryo and is below 30 nm peak-to-valley. These performances demonstrate the ability of such MOEMS device to work as objects selector in future generation of MOS instruments both in ground-based and space telescopes. In order to fill large focal planes (mosaicing of several chips), we are currently developing large micromirror arrays integrated with their electronics.

MEMS spectrometers have very strong potential in future healthcare and environmental monitoring applications, where Michelson interferometers are the core optical engine. Recently, MEMS Michelson interferometers based on using silicon interface as a beam splitter (BS) has been proposed [7, 8]. This allows having a monolithically-integrated on-chip FTIR spectrometer. However silicon BS exhibits high absorption loss in the visible range and high material dispersion in the near infrared (NIR) range. For this reason, we propose in this work a novel MOEMS interferometer allowing operation over wider spectral range covering both the infrared (IR) and the visible ranges. The proposed architecture is based on spatial splitting and combining of optical beams using the imaging properties of Multi-Mode Interference MMI waveguide. The proposed structure includes an optical splitter for spatial splitting an input beam into two beams and a combiner for spatial combining the two interferometer beams. A MEMS moveable mirror is provided to produce an optical path difference between the two beams. The new interferometer is fabricated using DRIE technology on an SOI wafer. The movable mirror is metalized and attached to a comb-drive actuator fabricated in the same lithography step in a self-aligned manner on chip. The novel interferometer is tested as a Fourier transform spectrometer. Red laser, IR laser and absorption spectra of different materials are measured with a resolution of 2.5 nm at 635-nm wavelength. The structure is a very compact one that allows its integration and fabrication on a large scale with very low cost.

In this work, we report about optical spectrometry using gold nano-structures printed on a polymer based integrated optical waveguide. The optical waveguide is a single mode buried waveguide, having dimensions of 3×2.2μm². It is made from a combination of photo-polymerizable materials and is fabricated by photolithography on a glass substrate. To sense the electric field inside the waveguide, a gold nano-coupler array of thin lines (50 nm thick and 8 μm length) is embedded on top of the aforementioned waveguide. They are produced by E-beam lithography. The array pitch is 2.872 μm and the number of lines 564, which yields an array of 1.619 mm length. The device is enclosed with a glass superstrate to prevent it from dust and destruction. Both waveguide ports are polished and the output port in particular, is coated with a thin gold layer to assimilate a mirror and hence, it enables the creation of stationary waves inside the structure. The measurement procedure involves light injection using a single mode fiber carrying both visible light (658nm) and infrared light (785nm), used for alignment and measurement purposes respectively. Stationary waves generated inside the guide constitute the spatial interferogram. Locally, light is out-coupled using the nano-couplers and allows measuring the interferogram structure. The resulting pattern is imaged by a vision system involving an optical microscope with a digital camera mounted on-top of it. Signal processing, mainly based on Fast Fourier transform is performed on the captured signal to extract the spectral content of the measured signal.

Micromachined tunable Fabry-Pérot filters (μFPF) are key elements in a new class of miniature spectrometers and analyzers. Different groups all over the world are working on μFPF for spectral ranges from the visible up to the long wave infrared. In order to achieve a large tuning range, the filters are normally operated in the first interference order. At the same time the spectral resolution is limited due to a limited effective finesse. A variety of applications demand for higher resolutions. This is particularly true for the multicomponent analysis of hydrocarbon gases, because the individual absorption bands are very similar and widely overlapping. In this paper μFPF in 3rd and 4th order configuration with a spectral resolution of about (20. . . 30) nm and a tuning range of (3.1. . . 3.7) μm are presented. For the measurement of additional gases in adjacent ranges (e.g. CO₂ around 4.3 μm) a dualband configuration with simultaneous use of different orders is proposed. A largely reduced damping of the μFPF and the combination with a lead selenide photoresistor instead of a thermal detector allows for a fast acquisition of spectra.

VTT Technical research centre of Finland has developed a MEMS Fabry-Perot interferometer (FPI) for the wavelength range from 7.5 μm to 9.5 μm. The device consists of two Distributed Bragg Reflectors (DBR) manufactured with MEMS processing techniques. The full width half maximum of the transmission peak is 150nm. This transmission peak can be tuned from 7.5 μm to 9.5 μm by applying a control voltage from 0 V to 30 V. A laboratory demonstrator has been put together to show the use of this module as a part of a spectral measurement setup. Several gas samples have been measured with the setup and compared against measurement results found in literature.

We report a MEMS optical tunable filter based on high-aspect-ratio etching of sub-wavelength silicon layers on a silicon- on-insulator wafer. The reported filter has measured free-spectral and filter-tuning ranges of approximately 100 nm and a finesse of about 20 around a wavelength of 1550 nm, enabled by the use of 1000 nm-thick silicon layers and a balanced tilt-free motion using a lithographically-aligned electrostatic actuator. The average insertion loss of the filter is about 12 dB with a superior wavelength-dependent loss of about 1.5 dB. The filter has an out-of-band to in-band wavelength rejection ratio that is better than 20 dB. The reported filter experimental characteristics and its integrability are suitable for the production of integrated swept sources for optical coherence tomography application and miniaturized spectrometers.

The suspended MEMS structure is suitable for reducing the energy loss due to the thermal conduction. There is the possibility that IR photon energy can be well-controlled to generate some physical effects. A new method bases on the nonlinear oscillation for the detector. The thin film torsional spring exhibits a large hard spring effect when the deflection occurs in the out-of-plane direction of the film. When IR is absorbed, the resonator bends due to the thermal expansion. The torsional spring becomes harder increasing the resonant frequency. The frequency measurement is suited for the precise sensing. The device response is measured using the laser (wavelength of 650nm). The resonant frequency is 88-94kHz. Q factor is about 1600 in vacuum (1Pa). The sensitivity is -0.144[kHz/(kW/m²)]. As for the emitter, nondispersive IR gas sensor is considered. The molecules have their intrinsic absorptions. CO₂ absorbs the wavelength 4.2- 4.3μm. The major incandescent light bulbs have the broad spectrum emitting IR which is not used for gas sensing. The wavelength selectivity at the gas bandwidth will improve the efficiency. A new principle uses the microheater placed facing to the grating. SPP is excited carrying IR energy on the grating surface. IR emission is the reverse process of excitation occurring at the output end. The emission spectra show SPP related peak having the width of 190nm. When the input power increases from 0.3 to 1.9W, the peak at wavelength of 3.5μm becomes clearer.

This paper presents a novel MOEMS Fabry-Perot interferometer (FPI) process platform for the range of 800 – 1050 nm. Simulation results including design and optimization of device properties in terms of transmission peak width, tuning range and electrical properties are discussed. Process flow for the device fabrication is presented, with overall process integration and backend dicing steps resulting in successful fabrication yield. The mirrors of the FPI consist of LPCVD (low-pressure chemical vapor) deposited polySi-SiN λ/4-thin film Bragg reflectors, with the air gap formed by sacrificial SiO2 etching in HF vapor. Silicon substrate below the optical aperture is removed by inductively coupled plasma (ICP) etching to ensure transmission in the visible – near infra-red (NIR), which is below silicon transmission range. The characterized optical properties of the chips are compared to the simulated values. Achieved optical aperture diameter size enables utilization of the chips in both imaging as well as single-point spectral sensors.

In this work we present a new type of optical strain sensor that can be manufactured by MEMS typical processes such as photolithography or by hot embossing. Such sensors can be of interest for a range of new applications in structural health monitoring for buildings and aircraft, process control and life science. The approach aims at high sensitivity and dynamic range for 1D and 2D sensing of mechanical strain and can also be extended to quantities such as pressure, force, and humidity. The sensor consists of an array of planar polymer-based multimode waveguides whose output light is guided through a measurement area and focused onto a second array of smaller detection waveguides by using micro-optical elements. Strain induced in the measurement area varies the distance between the two waveguide arrays, thus, changing the coupling efficiency. This, in turn, leads to a variation in output intensity or wavelength which is monitored. We performed extensive optical simulations in order to identify the optimal sensor layout with regard to either resolution or measurement range or both. Since the initial approach relies on manufacturing polymer waveguides with cross sections between 20×20 μm² and 100×100 μm² the simulations were carried out using raytracing models. For the readout of the sensor a simple fitting algorithm is proposed.

We have developed a silicon MEMS optical accelerometer in which the motion of the proof mass is mechanically amplified using a V-beam mechanism prior to transduction. The output motion of the V-beam is detected using a Fabry-Pérot interferometer (FPI) which is interrogated in reflection mode via a single-mode optical fibre. Mechanical amplification allows the sensitivity of the accelerometer to be increased without compromising the resonant frequency or measurement bandwidth. We have also devised an all-optical method for calibrating the return signal from the FPI, based on photothermal actuation of the V-beam structure using fibre-delivered light of a different wavelength. A finite-element model has been used to predict the relationship between the incident optical power and the cavity length at steady state, as well as the step response which determines the minimum time for calibration. Prototype devices have been fabricated with resonant frequencies above 10 kHz and approximately linear response for accelerations in the range 0.01 to 15 g.

Fourier modal method (FMM) is known as a powerful tool in simulations of periodic micro-structures, e.g., gratings. For an arbitrary plane wave incidence, the Rayleigh coefficients for both reflected and transmitted field can be calculated with the FMM efficiently. When dealing with a general beam incidence, FMM together with plane wave decomposition can still provide solutions. However the needed computational resources increase with the number of plane wave components in the angular spectrum domain. To solve this problem, we put forward an efficient approach which integrates interpolation technique into the method above. For most diffractive thin elements, the complex Rayleigh coefficients distribution is smooth. In this case several well-selected plane wave components are enough to characterize the diffraction property. In our method, only these selected plane wave components are analyzed with FMM while the results of other components are obtained by interpolation technique. Besides that, an efficient approach for especially divergent incident beam is also presented in this article. It enable a parallel FMM analysis which calculates a set of plane wave components in one computational loop.

The thin element approximation is an efficient algorithm to analyze diffractive optical elements (DOEs), whose feature size is large enough compared with the working wavelength. However, the thin element approximation is only valid under the condition of normal illumination. We hereby extend an algorithm, which is called the parabasal thin element approximation, to include the non-perpendicular illumination. More specifically, the thin element approximation is valid for paraxial incident beam, while the parabasal thin element approximation is valid for parabasal beam. In this article, we present the algorithm of the parabasal thin element approximation and compare the result with that of rigorous method. All the simulations are based on field tracing and done with the optical software VirtualLab™.

A new concept for the realization of a micro optical laser gyroscope was developed. It allows minimization of the influence of alignment errors by the use of double mirrors. As a consequence, the performance of a ring resonator structure is less vulnerable to micro assembly tolerances. The idea being pursued to improve the design robustness is based on the use of double mirror elements in which the angle between the two mirrors is intrinsically defined by silicon crystalline structure. With an angle of 120° between the mirrors the resulting reflection direction from each double mirror element is robust against deviations from ideal incidence angle. Here, the optical distortions due to rotational misalignments of double mirror elements that occur either during assembly or during operation due to thermal stresses are extremely low and can be determined after production and compensated. After describing the free space ring resonator concept all major processing and manufacturing steps of the double mirror elements are discussed. For the fabrication of these mirrors silicon wafers are used which are almost in (100) orientation but are tilted by 5.3° in <011> direction and, therefore, provide an etching facet with a slope of 60° by KOH wet chemical etching. A 33% KOH solution with addition of isopropanol is used to obtain more uniform and smooth facet surfaces. Two wafers structured in such way are connected by silicon direct bonding and then cut into small mirror elements which are mounted onto the gyroscope micro platform.

This paper presents a gimbaled MEMS scanning mirror (MSM) especially developed for adaptive raster scanning in a novel 3D ToF laser camera. Large quasi-static deflections of ±10° are provided by vertical comb drives in vertical direction in contrast to resonant horizontal scanning of the 2.6x3.6mm elliptical mirror at 1600 Hz and 80° optical scan range. For position feedback piezo-resistive position sensors are integrated on chip for both axes. To guarantee the full reception aperture of effective 5 mm a synchronized driven MEMS scanner array - consisting of five hybrid assembled MEMS devices - are used in a novel 3D ToF laser scanner enabling a distance measuring rate of 1MVoxel/s and an uncertainty of ToF distance measurement of 3…5 mm at 7.5 m measuring range for a gray target.