Optical MEMS

Optical microelectromechanical systems (MEMS), microoptoelectromechanical systems (MOEMS), or optical microsystems are devices or systems that interact with light through actuation or sensing at a micro- or millimeter scale. Optical MEMS have had enormous commercial success in projectors, displays, and fiberoptic communications. The best-known example is Texas Instruments’ digital micromirror devices (DMDs). The development of optical MEMS was impeded seriously by the Telecom Bubble in 2000. Fortunately, DMDs grew their market size even in that economy downturn. Meanwhile, in the last one and half decade, the optical MEMS market has been slowly but steadily recovering. During this time, the major technological change was the shift of thin-film polysilicon microstructures to single-crystal–silicon microsructures. Especially in the last few years, cloud data centers are demanding large-port optical cross connects (OXCs) and autonomous driving looks for miniature LiDAR, and virtual reality/augmented reality (VR/AR) demands tiny optical scanners. This is a new wave of opportunities for optical MEMS. Furthermore, several research institutes around the world have been developing MOEMS devices for extreme applications (very fine tailoring of light beam in terms of phase, intensity, or wavelength) and/or extreme environments (vacuum, cryogenic temperatures) for many years. Accordingly, this Special Issue seeks to showcase research papers, short communications, and review articles that focus on (1) novel design, fabrication, control, and modeling of optical MEMS devices based on all kinds of actuation/sensing mechanisms; and (2) new developments of applying optical MEMS devices of any kind in consumer electronics, optical communications, industry, biology, medicine, agriculture, physics, astronomy, space, or defense

Modeling and simulation of surface profile forming process of microlenses and their application in optical interconnection devices

Free space micro-optical systems require to integrate microlens array, micromirrors, optical waveguides, beam splitter, etc. on a single substrate. Out-of-plane microlens array fabricated by direct lithography provides pre-alignment during mask fabrication stage and has the advantage of mass manufacturing at low cost. However, this technology requires precise control of the surface profile of microlenses, which is a major technical challenge. The quality control of the surface profile of microlenses limits their applications. In this dissertation, the surface forming process of the out-of-plane microlenses in UV-lithography fabrication was modeled and simulated using a simplified cellular automata model. The microlens array was integrated with micromirrors on a single silicon substrate to form a free space interconnect system. The main contributions of this dissertation include: (1) The influences of different processing parameters on the final surface profiles of microlenses were thoroughly analyzed and discussed. A photoresist etching model based on a simplified cellular automata algorithm was established and tested. The forming process and mechanism of the microlens surface profile were explained based on the established model. (2) Microlens arrays with different parameters were designed, fabricated, and tested. The experiment results were compared with the simulation results. The possible causes for the deviation were discussed. (3) A microlens array based beam relay for optical interconnection application was proposed. A sequence of identical microlens array was fabricated on a single silicon substrate simultaneously and its optical performance was tested. A fast replication method for the microlens optical interconnects using PDMS and UV curable polymer was developed. A selective deposition method of micro-optical elements using PDMS ‘lift-off’ technique was realized. No shadow mask was needed during deposition process. With the continuous advances in the integration of micro-optical systems, direct lithography of micro-optical elements will be a potential technology to provide both precision alignment and low cost in manufacturing process. Microlenses and microlens array with precisely controlled surface profiles will be an important part in the micro-optical system

Interferometry-based Free Space Communication And Information Processing

This dissertation studies, analyzes, and experimentally demonstrates the innovative use of interference phenomenon in the field of opto-electronic information processing and optical communications. A number of optical systems using interferometric techniques both in the optical and the electronic domains has been demonstrated in the filed of signal transmission and processing, optical metrology, defense, and physical sensors. Specifically it has been shown that the interference of waves in the form of holography can be exploited to realize a novel optical scanner called Code Multiplexed Optical Scanner (C-MOS). The C-MOS features large aperture, wide scan angles, 3-D beam control, no moving parts, and high beam scanning resolution. A C-MOS based free space optical transceiver for bi-directional communication has also been experimentally demonstrated. For high speed, large bandwidth, and high frequency operation, an optically implemented reconfigurable RF transversal filter design is presented that implements wide range of filtering algorithms. A number of techniques using heterodyne interferometry via acousto-optic device for optical path length measurements have been described. Finally, a whole new class of interferometric sensors for optical metrology and sensing applications is presented. A non-traditional interferometric output signal processing scheme has been developed. Applications include, for example, temperature sensors for harsh environments for a wide temperature range from room temperature to 1000 degree C

Integrated dye lasers for all-polymer photonic Lab-on-a-Chip systems

Basierend auf integrierten Farbstofflasern wurden zwei optische Lab-on-a-Chip Systeme entwickelt. Zur effizienten Anregung von Fluoreszenzmarkern wurden optofluidische Farbstofflaser mit verteilter Rückkopplung (DFB Laser) untersucht. Für die markerfreie Moleküldetektion wurden Mikrokelchlaser entwickelt, die auf Flüstergaleriemoden basieren. Besonderes Augenmerk lag auf einer möglichen Großserienfertigung der Chips als kostengünstige Einwegartikel und auf einer einfachen Handhabung

IMECE2006-15704 THERMO-MECHANICAL BEHAVIOR OF A MICROMIRROR FOR LASER-TO-FIBER ACTIVE ALIGNMENT USING BIMORPHS WITH BREAKABLE TETHERS

ABSTRACT We will present a novel micromirror design in which tethered bimorph strips are used for mirror active alignment including beam steering and position fixing. A micromirror is attached to bimorphs that are pre-stressed at room temperature. A series of tethers link the bimorphs to the substrate to restrain their deformation. Breaking a tether by Joule heating allows the deformation of the bimorph to increase, changing the mirror position and orientation for precision alignment. With a large number of tethers, an optimum alignment can be achieved after breaking a selected group of tethers. We also report the experimental results of devices fabricated

Integrated polymer photonics : fabrication, design, characterization and applications

[no abstract

Evaluating the performance of digital micromirror devices for use as programmable slit masks in multi-object spectrometers

Multi-object spectrometers are extremely useful astronomical instruments that allow simultaneous spectral observations of large numbers of objects. Studies performed with ground-based multi-object spectrometers (MOSs) in the last four decades helped to place unique constraints on cosmology, large scale structure, galaxy evolution, Galactic structure, and contributed to countless other scientific advances. However, terrestrial MOSs use large discrete components for object selection, which, aside from not transferable to space-based applications, are limited in both minimal slit width and minimal time required accommodate a change of the locations of objects of interest in the field of view. There is a pressing need in remotely addressable and fast-re-configurable slit masks, which would allow for a new class of instruments - spacebased MOS. There are Microelectromechanical System (MEMS) - based technologies under development for use in space-based instrumentation, but currently they are still unreliable, even on the ground. A digital micromirror device (DMD) is a highly capable, extremely reliable, and remotely re-configurable spatial light modulator (SLM) that was originally developed by Texas Instruments Incorporated for projection systems. It is a viable and very promising candidate to serve as slit mask for both terrestrial and space-based MOSs. This work focused on assessing the suitability of DMDs for use as slit masks in space-based astronomical MOSs and developing the necessary calibration procedures and algorithms. Radiation testing to the levels of orbit around the second Lagrangian point (L2) was performed using the accelerated heavy-ion irradiation approach. The DMDs were found to be extremely reliable in such radiation environment, the devices did not experience hard failures and there was no permanent damage. Expected single-event upset (SEU) rate was determined to be about 5.6 micro-mirrors per 24 hours on-orbit for 1-megapixel device. Results of vibration and mechanical shock testing performed according to the National Aeronautics and Space Administration (NASA) General Environmental Verification Standard (GEVS) at NASA Goddard Space Flight Center (GSFC) suggest that commercially available DMDs are mechanically suitable for space-deployment with a very significant safety margin. Series of tests to assess the performance and the behaviour of DMDs in cryogenic temperatures (down to 78 K) were also carried out. There were no failures or malfunctions detected in commercially-available devices. An earlier prototype of a terrestrial DMD-based MOS (Rochester Institute of Technology Multi-Object Spectrometer (RITMOS)) was updated with a newer DMD model, and the performance of the instrument was evaluated. All the experiments performed strongly suggest that DMDs are highly reliable and capable devices that are extremely suitable for use as remotely programmable slit masks in MOS

Nanomechanical optical fiber with embedded electrodes actuated by joule heating

Nanomechanical optical fibers with metal electrodes embedded in the jacket were fabricated by a multi-material co-draw technique. At the center of the fibers, two glass cores suspended by thin membranes and surrounded by air form a directional coupler that is highly temperature-dependent. We demonstrate optical switching between the two fiber cores by Joule heating of the electrodes with as little as 0.4 W electrical power, thereby demonstrating an electrically actuated all-fiber microelectromechanical system (MEMS). Simulations show that the main mechanism for optical switching is the transverse thermal expansion of the fiber structure

Smart optical imaging systems with automated electronics

In this dissertation, proposed and demonstrated are several novel smart electronically automated optical designs to efficiently solve existing real-world problems in the field of shape sensing and imaging. First half of the thesis proposes shape sensing techniques that use an Electronically Controlled Variable Focus Lens (ECVFL) within a smart optical design suitable for a wide range of applications including shape sensing and projection displays. The second part of this dissertation involves the use of the Digital Micromirror Device (DMD) deployed within several smart optical designs including an embedded laser beam profiler and a new camera idea which is inspired by the Telecommunication science field. Specifically, proposed and demonstrated is the design and implementation of the novel imaging device called Coded Access Optical Sensor (CAOS) where CAOS is able of operating with different application dependent working modes. Experimentally and successfully demonstrated for the first time are its use for coherent light laser imaging as well as for incoherent imaging of a high dynamic range white light scenario. It is also shown how its design can be further extended for multispectral and hyperspectral imaging applications