This PDF file contains the front matter associated with SPIE Proceedings Volume 8616, including the Title Page, Copyright information, Table of Contents, and Conference Committee listing.

The long anticipated deployment of nano-optics that can enable next generation computing has encountered several practical impediments that have delayed widespread adoption in commercial processes. However, the global market in nano-enabled products is expected to grow to over $80B USD within the next 3 years. In response, the research community is creating solutions to overcome challenging issues such as reliability and cost-effective fabrication. New approaches in sensing, continuous uptime powering, and post silicon manufacturing will maximize overall performance and allow unprecedented commercial applications. This paper reviews present limitations of nano-optics and then considers the new generation of devices and their manufacturing that may turn promises into reality. We highlight several recent innovations: high sensitivity/selectivity nano-optical sensing devices; sustainable power from polymer energy harvesting and storage; optical variable devices for visual authentication of secure documents; and nano-template masters for high-volume manufacturing.

The technology for enhanced geothermal systems (EGS), in which fractures connecting deep underground wells are deliberately formed through high pressure stimulation for energy generation, is projected to enormously expand the available reserves of geothermal energy in the U.S. EGS could provide up to 100,000 MWe within the U.S. by the next 50 years. Pressure measurements, in particular, are important for determining the state of the fluid, i.e., liquid or steam, the fluid flow, and the effectiveness of the well stimulation. However, it has been especially difficult to accurately measure pressure at temperatures above ~200°C at a distance of 10 km below ground. MEMS technology has been employed for many years for extremely accurate pressure measurements through electrical readout of a MEMS fabricated resonator. By combining optical readout and drive at the end of a fiber optical cable with a MEMS resonator, it is possible to employ these highly accurate sensors within the harsh environment of a geothermal well. Sensor prototypes based on two beam and four beam resonator designs have been designed, fabricated and characterized for pressure response and accuracy. Resonant frequencies of the sensors vary between ~15 kHz and 90 kHz depending on sensor design, and laboratory measurements yielded sensitivities of frequency variation with external pressure of 0.9-2.2 Hz/psi. An opto-electronic feedback loop was designed and implemented for the field test. The sensors were packaged and deployed as part of a cable that was deployed at a geothermal well over the course of 2½ weeks. Error of the sensor versus the reference gage was 1.2% over the duration of the test. There is a high likelihood that this error is a result of hydrogen darkening of the fiber that is reducing the temperature of the resonator and, if corrected, could reduce the error to less than 0.01%.

In this report, Optical probe system for modality, optical coherence tomography (OCT) and optical coherence microscope (OCM), is presented. In order to control the back focal length from 2.2 mm to 27 mm, optical probe is designed using two liquid lenses and several lenses. The narrow depth of focus (DOF) in microscope is extended by phase filter such as cubic filter. The filter is modified so that DOF is extended only In the OCM mode. The section for the extended DOF of probe is controlled by iris. Therefore in OCT mode, the phase filter does not affect on the DOF of lens. In OCM mode, the Gaussian light and modified light will affect the DOF. The probe dimension is less than 4 mm diameter and less than 60 mm long. The scan range of system is 0.88 mm wide, 1 mm deep in the OCT and 510 μm wide, 1 mm deep in the OCM mode. The lens curvature and iris aperture are operated by digital microelectrofluidic lens and iris.

We present the preliminary design, construction and technology of a microoptical, millimeter-size 3-D microlens scanner, which is a key-component for a number of optical on-chip microscopes with emphasis on the architecture of confocal microscope. The construction of the device relies on the vertical integration of micromachined building blocks: top glass lid, silicon electrostatic comb-drive X-Y and Z microactuators with integrated scanning microlenses, ceramic LTCC spacer, and bottom lid with focusing microlens. All components are connected on the wafer level only by sequential anodic bonding. The technology of through wafer vias is applied to create electrical connections through a stack of wafers. More generally, the presented bonding/connection technologies are also of a great importance for the development of various silicon-based devices based on vertical integration scheme. This approach offers a space-effective integration of complex MOEMS devices and an effective integration of various heterogeneous technologies.

An electrostatically-driven microelectromechanical systems (MEMS) based pyramidal-polygonal micro-scanner is developed for circumferential-scanning endoscopic probes. In this paper, an endoscopic optical coherence tomography (OCT) probe is proposed, which utilizes multiple parallel incident light beams to drastically reduce the required mechanical rotation angle to achieve near 360-degree circumferential scanning. Manual assembly is employed to construct this micro scanner, which combines a silicon micromachined MEMS actuator with four sets of electrostatic comb-drives and a polymer-based pyramidal-polygonal micro-reflector. The pyramidal-polygonal micro-reflector is developed using a combination of high-precision diamond turning and soft lithography molding technologies. The measured average surface roughness and root-mean-square roughness of the diamond turned mold are 7.02 nm and 9.02 nm respectively, and those of the PDMS casted polygon micro-reflector with an Au coating are 48.95 nm and 61.90 nm respectively. Since near-infrared light sources with wavelengths ranging from 930 nm to 1550 nm are typically utilized for OCT applications, the surface roughness of the polygon reflector is better than λ/10 of the operating wavelength indicating that its quality meets the requirement of the OCT bio-imaging applications. An overall optical scan angle of near-360 degrees is demonstrated experimentally at a resonant frequency of 180 Hz with 80 Vpp ac driving voltage. The proposed MEMS scanner offers an alternative solution for circumferential scanning in endoscopic OCT probes owing to its advantages of compact design, fast scanning speed and low operational power consumption.

For both ultrasound and photoacoustic microscopic imaging, a fast scanning ability is required, whereas the liquid environment for acoustic propagation limits the usage of traditional MEMS scanning mirrors. In this paper, a new waterimmersible scanning mirror microsystem has been designed, fabricated and tested. To achieve reliable underwater scanning, flexible polymer torsion hinges fabricated by laser micromachining were used to support the reflective silicon mirror plate. Two efficient electromagnetic microactuators consisting of compact RF choke inductors and high-strength neodymium magnet disc were constructed to drive the silicon mirror plate around a fast axis and a slow axis, respectively. The performance of the water-immersible scanning mirror microsystem in both air and water were tested using the laser tracing method. For the fast axis, the resonance frequency reached 224 Hz in air and 164 Hz in water, respectively. The scanning angles in air and water under ±10 V AC driving (at the resonance frequencies) were ±13.6° and ±10°. The scanning angles in both air and water under ±16 V DC driving were ±12°. For the slow axis, the resonance frequency reached 55 Hz in air and 38 Hz in water, respectively. The scanning angles in air and water under ±10 V AC driving (at the resonance frequencies) were ±8.5° and ±6°. The scanning angles in both air and water under ±10 V DC driving were ± 6.5°. The feasibility of using such a water-immersible scanning mirror microsystem for scanning ultrasound microscopic (SAM) imaging has been demonstrated with a 25-MHz ultrasound pulse/echo system and a target consisting of three optical fibers.

We present an integrated beam scanning system without moving mechanical parts. The device based on the thermooptical effect. In combination with a silicon oxynitrid waveguide and a planar integrated lens we use thin film heaters for thermooptical deflection of a guided mode close to the edge of an integrated optical chip. This leads to a deflection at the collimation optic consisting of a planar lens. We show thermal simulation for the optimization of the heater position. The result of the thermal simulation is combined with BPM simulation to evaluate the change of the mode position during heating. First deflection measurements of the system are shown.

Low-cost automotive laser scanners for environment perception are needed to enable the integration of advanced driver assistant systems (ADAS) into all automotive vehicle segments, a key to reducing the number of traffic accidents on roads. An omnidirectional 360 degree laser scanning concept has been developed based on combination of an omnidirectional lens and a biaxial large aperture MEMS mirror. This omnidirectional scanning concept is the core of a small sized low-cost time-of-flight based range sensor development. This paper describes concept, design, fabrication and first measurement results of a resonant biaxial 7mm gimbal-less MEMS mirror that is electrostatically actuated by stacked vertical comb drives. Identical frequencies of the two resonant axes are necessary to enable the required circle scanning capability. A tripod suspension was chosen since it allows minimizing the frequency splitting of the two resonant axes. Low mirror curvature is achieved by a thickness of the mirror of more than 500 μm. Hermetic wafer level vacuum packaging of such large mirrors based on multiple wafer bonding has been developed to enable to achieve a large mechanical tilt angle of +/- 6.5 degrees in each axis. The 7mm-MEMS mirror demonstrates large angle circular scanning at 1.5kHz.

We report on a position sensing system for quasistatic MEMS mirrors using a point source LED imaged onto the backside of the mirror. The position signal is detected by a 4-quadrant-diode and can be used for digital closed-loop control. The resulting resolution is about 13 bit at a sampling frequency of 500 ksps. The whole detection system is integrated in a package enclosing the MEMS mirror, the optical beam path as well as the amplifier circuit of the 4-quadrant-diode. Based on similar control principles, a laser steering system for searching and tracking of moving objects, marked by retro-reflectors, will be presented. During an initial search, the laser steering system identifies objects by their initial position within a detection range between 1.5 m and 5 m distance and a maximum detection angle between 20 degrees and 72 degrees. The system follows the detected object on random trajectories by minimizing the zero-position error of the back reflected beam on a 4- quadrant-diode. Angular velocities of more than 100 degrees per arcsec have been measured.

Although a lot of micromechanical mirror devices are already available, there is still a lack of devices for measurement applications with large reflective plains and static deflection in the range of <-10° to >10° in analog mode. In our approach, aluminum nitride (AlN) deposited by reactive sputtering is used as torsional spring material. In contrast to crystalline and amorphous materials such as silicon or silica, the nanocrystallinity of AlN inhibits the propagation of cracks. Material tests show high mechanical strength and linear elastic behavior. Fatigue of the hinges couldn’t be observed so far. Those material attributes enable the fabrication of thin and compliant springs. Aside from the geometric parameters, spring stiffness can be tuned by the mechanical film stress during deposition. To reach highly dynamic mirror deflection, electrostatic actuation is used. Measurement results show an analog mechanical deflection range of ±11.7°. Using the pull-in, a digital rotation angle of about ±21° is achieved. These results match well with simulations. The mirror plain is stiffened by a bulk silicon layer. The samples have a mirror plate of 1.2 x 1.0 mm²suspended by 20 or 30 μm wide, 350 μm long and 0.4 μm thin stacked AlN (300 nm) /Al (100 nm) torsional springs.

Intensive industrial and academic research is oriented towards the design and fabrication of optical beam steering systems based on MEMS technology. In most of these systems, the scanning is achieved by rotating a flat micromirror around a central axis in which the main challenge is achieving a wide mirror rotation angle. In this work, a novel method of optical beam scanning based on reflection from a curved surface is presented. The scanning occurs when the optical axis of the curved surface is displaced with respect to the optical axis of the incident beam. To overcome the possible deformation of the spot with the scanning angle, the curved surface is designed with a specific aspherical profile. Moreover, the scanning exhibits a more linearized scanning angle-displacement relation than the conventional spherical profile. The presented scanner is fabricated using DRIE technology on an SOI wafer. The curved surface (reflector) is metalized and attached to a comb-drive actuator fabricated in the same lithography step. A single-mode fiber, behaving as a Gaussian beam source, is positioned on the substrate facing the mirror. The reflected optical beam angle and spotsize in the far field is recorded versus the relative shift between the fiber and the curved mirror. The spot size is plotted versus the scanning angle and a scanning spot size uniformity of about ±10% is obtained for optical deflection angles up to 100 degrees. As the optical beam is propagating parallel to the wafer substrate, a completely integrated laser scanner can be achieved with filters and actuators self-aligned on the same chip that allows low cost and mass production of this important product.

MEMS scanners are of interest for their potential as low-cost, low operating power devices for use in various photonic systems. The devices reported here are actuated by the electromagnetic force between a static external magnetic field and a current flowing through an SOI MEMS scanner. These scanners have several modes of operation: their mirrors may be rotated and maintained at a static angle (up to ± 1.4 degrees), scanned rapidly (up to 500 Hz); or may be operated in a resonance mode, at the device’s mechanical resonance frequency (~1.2 kHz) for higher rate scanning. The use of these scanners as a Q-switching element within a Nd:YAG laser cavity has been demonstrated. Pulse durations of 400 ns were obtained with a pulse energy of 58 μJ and a pulse peak power of 145 W. The use of an external magnetic field, generated by compact rare-earth magnets, allows a simple and cost-effective commercial fabrication process to be employed (the multi-user SOI process provided by MEMSCAP Inc) and avoids the requirement to deposit magnetic materials on the MEMS structure.

An arrayed beam steering device enables much simplified system architectures for high quality multiview 3D displays by adapting time multiplexing and eye tracking scheme. An array device consisting of microscale liquid prisms is presented, where the prism surface between two immiscible liquids is electrically controlled to steer light beams by the principle of electrowetting. An array prototype with 280×280μm pixels was fabricated and demonstrated of its full optical performances. The maximum tilting angle of each prism was measured to be 22.5° in average, with a tracking resolution of less than 0.04°. In this paper, we report a design and fabrication of eletrowetting based prism array, opto-fluidic simulations, optical characterizations, as well as applications to achieve low fatigue 3D displays.

This paper reports the fabrication of a 20×20 micro mirror array (MMA) designed for high optical power application (5- 8kW/m²). Each pixel can attain a 2D mechanical tilt angle of +/- 4° in any arbitrary axis with an applied voltage of 150V. A novel packaging architecture is proposed to increase the ratio of mirror surface to packaging surface based on fully vertically integration process of the actuation (vertical electrodes), electrical interconnections (TSV) and signal processing (electronic). All components have a pitch smaller than the mirror surface. A detailed assessment of the fabrication process - including 3D wafer level assembly, through silicon via (TSV), electronic integration, and characterization methodology is presented with experimental results.

In this paper, we present a new concept and fabrication of micro optical switch of which application is transmissive display devices. The micro optical switch consists of two parallel plate electrodes and is driven by electrostatic force. The first electrode is patterned on the glass substrate and the second electrode is disposed spaced apart from the first electrode. Each electrode has holes and the holes in each electrode do not overlap with one another. Light passes through the holes in the second electrode via the holes in the first electrode. All dimensions and fabrication process of the micro optical switch were designed to be compatible with Liquid Crystal Display (LCD) fabrication process. The size of the fabricated micro optical switch was 254μm × 254 μm. The micro optical switch was fabricated by surface micromachining. Aluminum was used as electrodes and patterned by plasma etching process. Photoresist was used as a sacrificial layer, which defined the gap between the two electrodes. Plasma ahsing was used to remove the sacrificial layer. Finally, anti-stiction layer was coated by Molecular Vapor Deposition (MVD) process. When voltage was applied, the second electrode moved down and contacted the first electrode. When voltage applying stopped, the second electrode returned to its original position. The voltage required to pull in the second electrode was below than 15 V. The sum of transition time, from on to off-state and from off to on-state, was below than 100 ㎲ and operating frequency was more than the 10 kHz.

Programmable MEMS diffraction gratings are used for spectroscopic applications because of their potential in tailoring visible and infrared spectra. A fully programmable MEMS diffraction grating (FPMDG), where every micro-mirror can move independently in a range 0 - λ/2, where λ is the wavelength of light, leads to a better control of the intensity for each wavelength in the synthetized spectrum – the intensity can take any value from 0 (micro-mirror λ/4-condition) to the maximum (no micro-mirror displacement). The FPMDG chip contains 64 micro-mirrors which are actuated electrostatically. Rigid Si micro-mirrors are connected to side electrodes via linkage arms, permitting the micro-mirror to follow a pure vertical displacement, reducing the micro-mirror bending throughout actuation. Microfabrication is based on a 4 mask photolithography process, using SOI and Pyrex wafers. Each micro-mirror of the FPMDG chip can move by 1.25μm at voltages below 100 V. Two families of micro-mirrors, 50μm or 80μm wide, show negligible cross-talk during actuation. The micro-mirror bowing is as small as 0.14 μm over 700 μm and remains unchanged throughout actuation. Extinction ratios of up to 100 have been achieved by actuating only 3 adjacent micro-mirrors. The measurements have shown high stability and good reproducibility over time. Finally, FPMDGs are used to demonstrate shaping of the input spectrum: the intensity in a particular wavelength region is controlled through independent actuation of a set of adjacent micro-mirrors. The result is attenuation or cancellation of the corresponding wavelengths.

Grating spectrometer, like the well-established Czerny-Turner, are based on an optical design consisting of several components. Typically at least two slits, two mirrors, the grating stage and a detector are required. There has been much work to reduce this effort, setups using only one mirror (Ebert - Fastie) or the replacement of the entrance slit through the use of thin optical fibers as well as integrated electronic detector arrays instead of a moving grating and an exit slit and single detector device have been applied. Reduced effort comes along with performance limitations: Either the optical resolution or throughput is affected or the use of the system is limited to the availability of detectors arrays with reasonable price. Components in micro opto electro mechanical systems (MOEMS-) technology and spectroscopic systems based thereon have been developed to improve this situation. Miniaturized scanning gratings fabricated on bonded silicon on insulator (BSOI-) wafers were used to design grating spectrometer for the near infrared requiring single detectors only. Discrete components offer flexibility but also need for adjustment of two mirrors, grating stage, fiber mount and the detector with its slit and optionally a second slit in the entrance area. Further development leads towards the integration of the slits into the MOEMS chip, thus less effort for adjustment. Flexibility might be reduced as adjustments of the optical design or grating spacing would require a new chip with own set of masks. Nevertheless if extreme miniaturization is desired this approach seems to be promising. Besides this, high volume production might be able for a comparable low price. A new chip was developed offering grating, two slits and a cavity for the detector chip. The optical design was adjusted to a planar arrangement of grating and slits. A detector buried in a chip cavity required a new mounting strategy. Other optical components were optimized and fabricated then the systems was assembled with electronics and software adjusted to the new design including some new features like integrated position sensors. A first test of systems to grant function of all components is presented. Further work will be aimed at improved performance like higher resolution and lower SNR.

SWIFTS, or Stationary-Wave Integrated Fourier Transform Spectrometer, is a new, highly integrated high-resolution spectroscopy technology that represents a major advance in the field. This is the first public presentation on the state-ofthe- art SWIFTS system. SWIFTS combines groundbreaking nanotechnology research, integrated optics, microelectronics and embedded software, resulting in high-resolution spectrometer technology bundled into a single device that is over 100 times more powerful in terms of spectral resolution than existing mini-spectrometers and more than 2,000 times smaller than highend spectrometers offering a similar level of performance. Systems based on this technology can typically achieve a spectral resolution of a few pm / 0.2 cm^-1 / 6 GHz, with a good SNR over a bandwidth ranging from several nm to a few hundred nm on a chip measuring a few mm², opening the way for product development based on the most demanding applications currently performed in research laboratories. The principle behind this patented technology will be explained, as will the technological choices made by Resolution Spectra Systems. We will present the most challenging building blocks of the technology: nano-pattern deposition, hybrid-chip assembly, light collection, calibration and data processing. In order to cater for different applications, the SWIFTS principle can be implemented in numerous configurations: multiple bands, multiplexing, spectro-imaging, integrated bio-sensors, etc. Various results have been obtained with either research setups or new products in the Visible and Near-Infrared, including analysis of tunable, multi-mode and high-stability lasers, Bragg sensor interrogator and high-depth Optical Coherent Tomography.

Fiber lasers have reached kW levels of output power. To achieve this level it is necessary to use reliable high-power components that sustain these power levels. Double-clad fibers (DCFs) are often used in high-power fiber lasers. Cladding-light strippers (CLSs) are used to remove unwanted light from the inner cladding of the DCF. This unwanted light consists of residual pump light or signal light that leaked into the cladding, thus requiring that the CLS removes both high-NA (>0.4) and low-NA (<0.1) light. Often high-index polymers are used to remove the unwanted light from DCFs^1,2,3. Because the CLS has to be able to withstand several 100W and most polymers are not capable of exceeding temperatures more than 200°C, we investigated a CLS without polymers, based on an etching process. We present results from a CLS that was tested up to 500W of stripped power. We determined the angle dependency of the stripping efficiency by launching both high- and low-NA light into the fiber and evaluating the NA attenuation. Furthermore, we measured the dependency of the stripping efficiency on the length of the etched area and the etching time. With optimized parameters an attenuation of more than 20 dB when launching high-NA light and 6 dB with low-NA light was achieved. The CLS did not show any degradation in terms of attenuation or thermal behavior in a six-hour stability test.

In this paper a novel approach for optical beam splitting for MEMS based Fourier transform spectrometer is proposed. This approach is mainly based on spatial truncation of the input Gaussian beam into two symmetric Semi- Gaussian beams using V shape mirror and hence eliminating the use of a beam splitter and allowing the integration of optical spectrometers. It can be used over wide spectral range including infrared and visible region. Unlike the traditional Michelson interferometers which return half of the optical power to the source, the reflected power is negligible. This enables the use of multiple reflecting mirrors increasing the optical path difference by a factor of four. The analytical model describing the beams propagation and interference is derived using Fourier optics techniques and verified using Finite Difference time domain method. Mechanical model providing the mirror displacement to produce the optical pass difference is conducted and verified using finite element method. Mechanical displacement of 160 μm is achieved which is multiplied by a factor of four, resulting is a resolution of 9 nm at wavelength 1.55 μm. Finally, the effect of different design parameters on the interference pattern, interferogram and resolution are demonstrated.

Light trapping in optical cavities has many applications in optical telecommunications, biomedical optics, atomic studies, and chemical analysis. Efficient optical coupling in these cavities is an important engineering problem that affects greatly the cavity performance. One interesting way to form an optical cavity, while simultaneously connected to the rest of the optical systems, is to use an optical fiber surface as one of the cavity mirrors while the second mirror is fabricated by MEMS technology. In this way, cavity tuning with a MEMS actuator is a simple achievable task with low cost in mass production. The main problem in this solution is the high diffraction loss associated with the small spot size at the output of the standard single-mode fiber (SMF). Diffraction loss in the cavity is usually overcome by using an expensive lensed fiber or by inserting a coated lens in the cavity leading to a long cavity with small free spectral range (FSR). In this work, we report a Fabry-Perot cavity formed by a multilayer-coated cleaved-surface SMF inserted into a grove while facing a spherical micromirror; both are fabricated by silicon micromachining. The light is trapped inside the cavity while propagating in-plane of the wafer substrate. The light is injected in and collected from a Corning SMF-28 optical fiber with a coated surface reflectivity of about 98% at 1330 nm (O-band). The silicon mirror surface is aluminum metalized with a reflectivity of about 92%. The measured cavity has a line width of 0.45 nm around 1330 nm with a FSR of 26 nm. The obtained results indicate an almost diffraction-loss free optical cavity with a quality factor close to 3000, limited by the optical surfaces reflectivity that can be improved in future by an optimized mirror fabrication process and better matching of the fiber multilayer coating.

In this paper, we demonstrate a novel split-ladder photonic crystal cavity, which can be tuned across a very large wavelength range by an on-chip integrated nano-electromechanical actuator. The nano-electromechanical actuator is used to control the cavity’s central gap. When the cavity gap is widened, the resonance wavelength is blue-shifted correspondingly. The dimensions of the proposed split-ladder cavity are designed by 3D Finite-difference time-domain (FDTD) calculations. We fabricated and tested the devices. Experimental results show that the optomechanical coupling coefficient of the second order resonance mode is about 80 GHz/nm. In addition, there is a relatively linear relationship between the resonance shift and the gap change. The maximum measured resonance wavelength shift is about 17 nm, corresponding to a cavity central gap increase of 26 nm.

We propose compact holographic printer using RGB waveguide hologram while reducing overall device size and quantity of elements with integrated functionality of each optical element. For glasses-free 3D experience anywhere anytime, it is critical to make holography device that can be as compact and integrated as possible. Compared to the conventional optics-based structure, our RGB WGH-based one reduces the overall size by 20 times, the number of components by 10 times, and improves the optical efficiency by 3 times, with comparable holographic quality to the conventional optics-based approaches. Proposed research can be useful for both general consumers and professionals like 3D photography and medical 3D image printing applications.

The electrostatic actuation is still a preferred principle in modern microelectromechanical systems (MEMS). Based on the Coulomb attraction between two different point charges, the electrostatic actuation is a surface effect and thus volume-independent. In addition, the efficiency of electrostatic actuation increases with a decreasing gap size between the electrodes. The relatively simple morphology of an electrostatic actuator allows low-cost wafer-level fabrication, making it a versatile and convenient principle for MEMS actuators. Although the electrostatic principle seems only to be applicable for actuators in micrometer scale, this paper presents the successful upscaling of an electrostatic actuator to the millimeter scale, still utilizing the major advantages, including wafer-level fabrication, of the said principle and providing a high stroke with low actuation voltage. For such an actuator, we replace the common silicon with the non-conducting OrmoComp, a UV-curable hybrid polymer, suitable for wafer-level fabrication. With a significantly lower elastic modulus, only a fraction of actuation voltage is necessary for a similar deflection. The electrodes are realized with additional coatings of thin metal layers. To achieve a high stroke, while maintaining a relatively low voltage, the actuator design is based on a redesigned zipper actuator. With our developed fabrication process, we are able to create a highly displaced out-of-plane actuator, while almost eliminating the initial gap between the electrodes. Experimental results of a wafer-level fabricated zipper actuator show an out-of-plane motion up to 470 μm at an actuation voltage of 374 V.

MEMS diffraction gratings whose period can be tuned during operation find applications in microspectrometers and in display devices. These structures were designed using fixed-fixed beams of 10 μm width and spacing of 2 μm between them and were actuated in an out-of-plane motion. It was found that non-planar bending of fixed-fixed beams reduces the amount of light diffracted into the first order by about 4% compared to ideal planar beam displacement. A new fixed-fixed beam design with modified spring constant and actuation mechanism was proposed to improve the planarity of the beam during actuation. The profiles of the two structures (proposed design and normal beam), when displaced by λ/4 (relative displacement between two beams required for diffraction), were extracted using Intellisuite simulations and this data was fitted with a ninth order polynomial to model the beam displacement. The grating transfer function was modeled with the acquired displacement profiles and it was found that the new design improved the efficiency in the first order by about 2% when simulated in MATLAB for 633 nm wavelength. The grating structures were fabricated using a 4-mask process and were released using a wet release process developed in the lab. The electrical characterization of the devices indicates that the devices were released. The grating structures were tested optically using an optical setup built in the lab.

Due to climate protection and increasing oil prices, renewable energy is becoming extremely important. Anaerobic digestion is a particular environmental and resource-saving way of heat and power production in biogas plants. These plants can be operated decentralized and independent of weather conditions and allow peak load operation. To maximize energy production, plants should be operated at a high efficiency. That means the entire installed power production capacity (e.g. CHP) and biogas production have to be used. However, current plant utilization in many areas is significantly lower, which is economically and environmentally inefficient, since the biochemical process responds to fluctuations in boundary conditions, e.g. mixing in the conditions and substrate composition. At present only a few easily accessible parameters such as fill level, flow rates and temperature are determined on-line. Monitoring of substrate composition occurs only sporadically with the help of laboratory methods. Direct acquisition of substrate composition combined with a smart control and regulation concept enables significant improvement in plant efficiency. This requires a compact, reliable and cost-efficient sensor. It is for this reason that a MEMS sensor system based on NIR spectroscopy has been developed. Requirements are high accuracy, which is the basic condition for exact chemometric evaluation of the sample as well as optimized MEMS design and packaging in order to work in poor environmental conditions. Another issue is sample presentation, which needs an exact adopted optical-mechanical system. In this paper, the development and application of a MEMS-based analyzer for biogas plants will be explained. The above mentioned problems and challenges will be discussed. Measurement results will be shown to demonstrate its performance.

The hetero-integration of InGaAsP/InP on highly doped silicon micro wire structure for Si hybrid laser using the plasma assisted direct bonding has been carried out. For strong adhesion, bonding assisted pattern was used for the silicon wire to the InGaAsP/InP layers. The I-V characteristics of the highly doped silicon micro wire to InP/InGaAsP layers are measured and compared to the Si/InP bulk bonding. The improvement of the heterointegration with long time annealing was also discussed and realized the direct current injection from Si wire platforms to compound semiconductor active layer for silicon hybrid laser.

The nano-gratings are widely used in the optical measurement, integrated optics, optical information processing and other fields. It has been prepared by using electron beam lithography, etching, electroplating, nano imprinting, and LIGA technologies. In general, the fabrications of nano-grating require expensive and sophisticated equipment. The fabrication procedures involved are often complicated, therefore resulting in high cost and long production cycles. We report a new technology to fabricate nano-grating with much lower-cost. The technology is based on utilizing the high flexibility of PDMS and the nano-molding technology. Using this technology, nano-gratings can be fabricated in low-cost and no expensive or high precision equipment is needed. Because of the excellent replication property of PDMS molds, large number of gratings can be made with a single master mold.

A new design concept for a dynamically focusing micromachined silicon membrane mirror with 6 mm diameter and electrostatic actuation was realized. To eliminate the influence of residual stress a special stress relief design of the membrane`s suspension was developed in order to achieve a distortion-free optical mirror (distortion < λ/10 (λ = 1064 nm). Even silicon membranes fabricated in SOI technology mostly suffer from buckling by residual compressive stress caused by mismatch in the coefficients of thermal expansion between silicon and the buried silicon oxide layer [1, 2].This often leads to severe distortion of stress sensitive devices such as membrane based micro mirror devices [3]. Even though a tensile pre-stress might improve the distortion in case of a non-deformed membrane, a tensile stress in the membrane increases the stiffness and thus reduces the sensitivity e.g. for capacitive sensors or for actuating devices. Different methods are reviewed for stress compensation or stress relief in membranes. We developed and fabricated a new stress relief structure which reduces the stress induced deformation of membranes and leads to substantially flat micromirrors of high optical quality. This is achieved by a special tangential beam suspension which allows an in-plane expansion or contraction of the membrane proportional to its inherent compressive or tensile stress. Optimized beam structures and the voltage dependence of the mirror’s deflection were determined by 3D FEM simulations. For membranes with a compressive pre-stress of -20MPa simulations show a decrease in bow to values < 18 nm in comparison with 700 nm for a conventional rigidly clamped membrane. A deflection of 16 μm within an aperture of 5 mm diameter is theoretically achieved by a voltage U₀ = 200 V resulting in a minimal focal length of 97 mm. The fabricated devices have been characterized by the means of interferometric optical measurement. The measurement results are in good agreement with the theoretical prediction of FEM simulations.

We report on the development of sub-millimeter size adaptive liquid microlenses and microlens arrays using two immiscible liquids to form individual lenses. Microlenses and microlens arrays having aperture diameters as small as 50 microns were fabricated on a planar quartz substrate using patterned hydrophobic/hydrophilic regions. Liquid lenses were formed by a self-assembled oil dosing process that created well-defined lenses having a high fill factor. Variable focus was achieved by controlling the lens curvature through electrowetting. Greater than 70° of contact angle change was achieved with less than 20 volts, which results in a large optical power dynamic range.

We introduce sputtered aluminum nitride thin films for tunable micro-optics. During lens fabrication, AlN is deposited on a silicon substrate. Silicon is structured by using DRIE, which allows fabrication of circular, rectangular and irregular membrane shapes. In this contribution, we present the design, fabrication and characterization of AlN membranes for tunable cylindrical lenses. An optimized “dogbone” membrane is presented, which deflects cylindrically and has a small footprint. Compared to conventional rectangular membranes the optically useful area is doubled. The load deflection characteristic is investigated and basic relations between the refractive power and applied pressure are found. The relation can be used for tailoring the membrane properties, i.e. their residual stress, for a specific application. According to this calculation, a refractive power of 25 dpt with a lens aperture of 3x3 mm² is achieved for 12 kPa of applied pressure. The cylindrical deflection of the “dogbone” membrane is measured. The maximum shape difference in measured to be 270 nm.

This paper presents experimental results on several liquid lenses based on Electrowetting which are commercially available. It will be shown that larger aperture lenses are basically of the same optical quality than smaller lenses, sometimes reaching the diffraction limit, then opening new kind of applications areas for variable lenses in laser science. Regarding response time, actual performances of liquids lenses based on Electrowetting are presented and compared to a model simulating the internal fluid reorganization, seen as the main source of delay between electrical actuation and optical evolution of the lens. This simplified analytical model is supporting experimental results in various situations (focus and tilt variations), in static and dynamic regimes.

MOEMS (Micro-Opto-Elecro-Mechanical Systems) has brought new inspirations to the traditional optics design and manufacturing, due to their advantages such as micro sizes, low cost, good performance, easy to integrate, and mass production. From the microfabrication technology perspective, microlens is among the most difficult components to make, and it is also the most important component of all free space micro-optic components. In recent years, the aspherical lens with controllable curvature has become one of the most popular research subjects since it is helpful in eliminating aberration. In this paper, we report a new method of fabricating and replicating aspherical microlens array with primary optic axis in parallel with the substrate surface. The technology was based on ultra-violet (UV) lithography of SU-8 thick resist. A novel water bath oblique lithography technique was adopted. Diameter of the prototype microlenses fabricated is about 200 μm. By changing the pattern of mask and other process parameters, aspherical microlenses with different sizes and surface curvatures can be obtained. The microlens made using this technique has its main optical axis in parallel with the substrate, this makes it much easier to be integrated with other components into on-chip optical platforms such as optical switch and the imaging systems. This kind of micro-lens arrays will also be incorporated to microfluidic systems such as micro flow cytometry for fluorescence detections.

We suggest a Time-of-Flight (TOF) video camera capturing real-time depth images (a.k.a depth map), which are generated from the fast-modulated IR images utilizing a novel MOEMS modulator having switching speed of 20 MHz. In general, 3 or 4 independent IR (e.g. 850nm) images are required to generate a single frame of depth image. Captured video image of a moving object frequently shows motion drag between sequentially captured IR images, which results in so called ‘motion blur’ problem even when the frame rate of depth image is fast (e.g. 30 to 60 Hz). We propose a novel ‘single shot’ TOF 3D camera architecture generating a single depth image out of synchronized captured IR images. The imaging system constitutes of 2x2 imaging lens array, MOEMS optical shutters (modulator) placed on each lens aperture and a standard CMOS image sensor. The IR light reflected from object is modulated by optical shutters on the apertures of 2x2 lens array and then transmitted images are captured on the image sensor resulting in 2x2 sub-IR images. As a result, the depth image is generated with those simultaneously captured 4 independent sub-IR images, hence the motion blur problem is canceled. The resulting performance is very useful in the applications of 3D camera to a human-machine interaction device such as user interface of TV, monitor, or hand held devices and motion capturing of human body. In addition, we show that the presented 3D camera can be modified to capture color together with depth image simultaneously on ‘single shot’ frame rate.

There is a need for small compact multispectral and hyperspectral imaging systems that simultaneously images in many spectral bands across the infrared spectral region from short to long-wave infrared. This is a challenge for conventional optics and usually requires large, costly and complex optical systems. However, with the advances in materials and photolithographic technology, Micro-Optical-Electrical-Machine-Systems (MOEMS) can meet these goals. In this paper Pacific Advanced Technology and ECBC will present the work that we are doing under a SBIR contract to the US Army using a MOEMS based diffractive optical lenslet array to perform simultaneous multispectral and hyperspectral imaging with relatively high spatial resolution. Under this program we will develop a proof of concept system that demonstrates how a diffractive optical (DO) lenslet array can image 1024 x 1024 pixels in 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 purpose of this work is to simultaneously image multiple colors each frame and reduce the temporal changes between colors that are apparent in sequential multispectral imaging. Translating the lenslet array will collect hyperspectral image data cubes as will be explained later in this paper. Because the optics is integrated with the detector the entire multispectral/hyperspectral system can be contained in a miniature package. The spectral images are collected simultaneously allowing high resolution spectral-spatial-temporal information each frame of the camera. Thus enabling the implementation of spectral-temporal-spatial algorithms in real-time with high sensitivity for the detection of weak signals in a high background clutter environment with low sensitivity to camera motion. Using MOEMS actuation the DO lenslet array is translated along the optical axis to complete the full hyperspectral data cube in just a few frames of the camera, i.e. less than 1 second. In addition to numerous defense and security applications the same technology can be applied to biomedical cellular and molecular imaging.

As demonstrated in microelectronics, the batch fabrication based on the processing of wafers can lead to a significant reduction in prize as well as in size. This concept was adapted to the fabrication of imaging optics extensively used in mobile phone cameras relying on small pixels and low resolutions such as VGA. We report on batch fabricated customer specific opto-electronical modules used in machine sensing and automotive applications relying on large pixel sizes and non-conventional sensor characteristics. We specially focus on the lens mold mastering for the subsequent UV-replication since comparatively large sag heights of 250μm are required. Two technological approaches were applied, first, based on reflow of photoresist and, second, using diamond turning for the generation of a single lens mold and a subsequent step&repeat-process for array mastering on 8" wafers. Aspects of the optical design and simulation, the batch fabrication based on 8" wafers and characterization results are provided by the example of an f/1.1 opto-electronic sensor and an objective for a global shutter imager using 550x550 pixels with 3.6μm pitch.

Image sensors for digital cameras are built with ever decreasing pixel sizes. The size of the pixels seems to be limited by technology only. However, there are also hard theoretical limits for classical miniature camera systems: During a certain exposure time only a certain number of photons will reach the sensor. The resulting shot noise thus limits the signal-to-noise ratio. On the other hand, diffraction sets another limit for image resolution in case that there is enough brightness in the scene. In this work we show that current sensors are already surprisingly close to these limits.

Optical MEMS could be major candidates for designing future generation of space instruments. In addition to their compactness, scalability, and specific task customization, they could generate new functions not available with current technologies. We have listed new functions associated with several types of MEMS. Instrumental applications are derived and we propose two promising concepts using object selection and spectral tailoring techniques. In Earth Observation instruments, observation of scenes including bright sources leads to an important degradation of the recorded signal. We propose a new concept to remove dynamically the bright sources and obtain a field of view (FOV) with an optically enhanced SNR. Our concept consists in replacing the plain slit in classical designs by an active row of MOEMS. Experimental demonstration of this concept has been conducted on a dedicated bench: a scene with a contiguous bright area has been focused on a micromirror array and imaged on a CCD detector. After the programmable slit, the straylight issued from the bright zone is polluting the scene; the micromirrors located on the bright area are switched off, removing almost completely the straylight in the instrument. In Astronomy and Earth Observation, we propose an innovative reconfigurable instrument: a programmable wide-field spectrograph where both the FOV and the spectrum could be tailored thanks to a 2D micromirror array. The FOV is linear and each point spectrum could be modified dynamically along the second direction. A demonstrator has been designed and its realization is under way for testing the unique performances of this instrument.

In this paper we present a driver for accurate positioning of certain electrostatically driven micro-opto-electromechanical system (MOEMS) based scanner mirrors. The driver unit can control up to six quasi-static mirror axes using closed loop control. The electronics are described in this contribution together with different closed-loop control algorithms, which were implemented for fast and accurate positioning. Results from closed loop operation are compared to the characteristics of the devices when driven in open loop mode. Settlings times and operating bandwidth can be improved by a factor of up 40.