In-Plane Optical Beam Collimation Using a Three-Dimensional Curved MEMS Mirror (original) (raw)

Integration of optoelectronics and MEMS by free-space micro-optics

2000

This report represents the completion of a three-year Laborato~-Directed Research and Development (LDRD) program to investigate combining microelectromechmicd systems (MEMS) with optoelectronic components as a means of realizing compact optomechanica.1 subsystems. Some examples of possible applications are laser beam scanning, switching and routing and active focusing, spectral filtering or shattering of optical sources. The two technologies use dissimilar materials with significant compatibility problems for a common process line. This project emphasized a hybrid approach to integrating optoelectronics and MEMS. Significant progress was made in developing processing capabilities for adding optical function to MEMS components, such as metal mirror coatings and through-vias in the substrate. These processes were used to demonstrate two integration examples, a MEMS discriminator driven by laser illuminated photovoltaic cells and a MEMS shutter or chopper. Another major difficulty with direct integration is providing the optical path for the MEMS components to interact with the light. We explored using folded optical paths in a transparent substrate to provide the interconnection route between the components of the system. The components can be surface-mounted by flip-chip bonding to the substrate. Micro-optics can be fabricated into the substrate to reflect and refocus the light so that it can propagate from one device to another and them be directed out of the substrate into free space. The MEMS components do not require the development of transparent optics and can be completely compatible with the current 5-level polysilicon process. We report progress on a MEMS-based laser scanner using these concepts.

Micromachined integrated optics for free-space interconnections

Proceedings IEEE Micro Electro Mechanical Systems. 1995, 1995

A novel surface micro-machined micro-optical bench (MOB) has been demonstrated. Free-space micro-optics such as micro-Fresnel lenses, rotatable mirrors, beam-splitters and gratings are implemented on a single Si chip using IC-like microfabrication processes. Self-aligned hybrid integration with semiconductor lasers are also demonstrated for the first time. The MOB technology realizes a microoptical system on a single Si chip and has significant impact on free-space integrated optics, optical switching, optical data storage, and optoelectronic packaging.

High-Quality Microlenses and High-Performance Systems For Optical Microelectromechanical Systems

2003

Major opportunities exist for optical microelectromechanical systems (MEMS) and, despite recent economic setbacks for companies working in the field, concentrated research on optical MEMS is underway at many locations. Most of the research reported thus far has been focused on activated-mirror-micro-optical systems-which have instantly recognizable applications in the display and fiber-optic-switching fields. Optical components other than activated mirrors must, however, be available for designers to produce micro-optical systems for other applications that are already of proven value in macro designs. Chief among the needed components are lenses with high optical quality that can be accurately formed and placed at specified locations in an optical system. Another need is for polarized-light beam splitters that can be fabricated using the materials and technologies that are generally available to MEMS designers. Research at the Berkeley Sensor & Actuator Center (BSAC) has led to important advances in producing both precise high-quality lenses and high-performance polarization-beam splitters for micro-optical MEMS [1], [2]. In this White Paper, we first make clear the need for precision microlenses and then describe an important new MEMS optical system that would be made possible by precision microlenses. We begin with a review of the significant progress that we have already made in building high-quality lenses as well as high-performance polarizationbeam splitters at BSAC. We then describe some opportunity areas that have been opened through this progress. In a final section we present guidelines and milestones that will advance this work and lead to new optical-MEMS capabilities.

Monolithic fabrication of optical benches and scanning mirror using silicon bulk micromachining

Journal of Micromechanics and Microengineering, 2005

This paper details an optical scanning mirror with a 54.74 • inclined reflective plane and optical benches to align the optical components simply in a monolithic silicon substrate so as to implement a miniaturized laser scanner. The scanning mirror was designed and fabricated to achieve laser scanning on a miniaturized scale so that fluorescence detection of arrays of patterns on biochips can be performed by a handheld system. The inclined (1 1 1) reflective plane of the scanning mirror was formed by the KOH wet etching process, and proved to be a very appropriate structure for the assembly of optical scanning systems composed of a laser input and a scanning mirror in a silicon substrate. The optical benches, torsion spring and comb electrodes were fabricated using the DRIE process. The scanning mirror is actuated by its moment of inertia, the electrostatic torque of the comb electrodes and the restoring torque of the torsion spring. As designed, the scanning mirror is 2165 × 778 µm 2 in an upper part of the rotor of the mirror, and the chip size including optical bench guides is 9 × 10 × 1 mm 3. The deflection angle of the scanning mirror was measured by a laser displacement meter (LC2420, Keyence, Japan), and the optical components were assembled and aligned in optical bench guides to observe the laser scanning. The deflection angle of the scanning mirror depends on matching the frequency of the driving signal and the mechanical oscillation of the scanning mirror, and a maximum deflection angle of ±7 • was obtained when a 16 V peak-peak square wave was applied to the comb electrodes. The scanning mirror with an inclined reflective plane and optical benches fabricated in a monolithic silicon substrate was proved to be a smart structure to implement a handheld-type scanning system for biochip application.

Fabrication of integrated diffractive micro-optics for MEMS applications

SPIE Proceedings, 2001

We investigated the fabrication of integrated diffractive micro-optical features on MEMS structures for the purpose of motion detection. The process of producing the diffractive features and the MEMS structures by focused ion beam milling is described in detail, as is the ion beam sputtering process used to produce coatings on these structures. The diffractive features of the circular Fresnel zone plate (FZP) and spiral FZP were fabricated on MEMS structures and the relevant diffraction theory is discussed. The spiral FZP diffractive features produced well defined foci whose intensity varies with distance from the FZP. Observation of these intensity variations enabled us to detect the motion of the MEMS structure, and the resulting device was used to scan an IR image of a hot object.

Monolithic silicon-micromachined free-space optical interferometers onchip

Laser & Photonics Reviews, 2014

The integration of microactuators within a silicon photonic chip gave rise to the field of optical micro-electromechanical systems (MEMS) that was originally driven by the telecommunication market. Following the latter's bubble collapse in the beginning of the third millennium, new directions of research with considerable momentum appeared focusing on the realization and applications of miniaturized instrumentation in biology, chemistry, physics and materials science. At the heart of these applications light interferometry is a key optical phenomenon, in which miniaturized scanning interferometers are the manipulating optical devices. Monolithic free-space optical interferometers realized on a silicon chip take advantage of the recent progress in the microfabrication technology that is enabling accurate control of the etching depth, the aspect ratio, the verticality and the curvature of the etched surfaces. The fabrication technology, the library of micro-optical and mechanical components, the realized architectures and their characterization are described in detail in this review, followed by a discussion of the foreseen challenges.

Analysis of Optical Diffraction Profiles Created by Phase-Modulating MEMS Micromirror Arrays

Micromachines

This paper presents modeling and analysis of light diffraction and light-intensity modulation performed by an optical phased array (OPA) system based on metal-coated silicon micromirrors. The models can be used in the design process of a microelectromechanical system (MEMS)-based OPA device to predict its optical performance in terms of its field of view, response, angular resolution, and long-range transmission. Numerical results are derived using an extended model for the 1st-order diffracted light intensity modulation due to phase shift. The estimations of the optical characteristics are utilized in the designs of an OPA system capable of active phase modulation and an OPA system capable of array pitch tuning. Both designs are realized using the Multi-User MEMS Processes (PolyMUMPs) in which polysilicon is used as structural material for the MEMS-actuated mirrors. The experiments are performed to evaluate the optical performance of the prototypes. The tests show that the individu...

Fabrication of micro-mirrors with pyramidal shape using anisotropic etching of silicon

2004

Gold micro-mirrors have been formed in silicon in an inverted pyramidal shape. The pyramidal structures are created in the (100) surface of a silicon wafer by anisotropic etching in potassium hydroxide. High quality micro-mirrors are then formed by sputtering gold onto the smooth silicon (111) faces of the pyramids. These mirrors show great promise as high quality optical devices suitable for integration into MOEMS systems.

Curved Silicon Micromirror for Linear Displacement-to-Angle Conversion With Uniform Spot Size

IEEE Journal of Selected Topics in Quantum Electronics, 2015

This paper reports a novel class of deeply etched curved micromirrors enabling linear conversion between the reflection angle of incident light beam and displacement of the beam axis with respect to the curved mirror principal axis. Moreover, the mirror provides phase-transformation of the light beam independent of the inclination angle of the incident light on the mirror surface. The micromirrors are fabricated on SOI substrate by deep reactive ion etching technology. The profile of the curved surface is optimized and controlled precisely, thanks to the photolithographic process. High optical throughput micromirrors exhibiting submillimeter focal lengths are fabricated with 200-μm etching depth and with a sidewall angle deviation from perfect verticality, which is smaller than 0.1°. Optical measurements at wavelengths of 675 and 1550 nm show transformation of the optical beam with high optical spot size stability during a beam steering process with less than ±5% dependence on the inclination/reflection angle over a scanning angle range of 120°. The presented micromirror has applications in MEMS scanners, displacement/rotation sensing, and optical imaging. Index Terms-Curved micro-optics, displacement sensor, DRIE, MEMS optical bench technology, optical scanner.

Wafer-scale micro-optics fabrication

Micro-optics is an indispensable key enabling technology for many products and applications today. Probably the most prestigious examples are the diffractive light shaping elements used in high-end DUV lithography steppers. Highly-effi cient refractive and diffractive micro-optical elements are used for precise beam and pupil shaping. Micro-optics had a major impact on the reduction of aberrations and diffraction effects in projection lithography, allowing a resolution enhancement from 250 nm to 45 nm within the past decade. Micro-optics also plays a decisive role in medical devices (endoscopes, ophthalmology), in all laser-based devices and fi ber communication networks, bringing high-speed internet to our homes. Even our modern smart phones contain a variety of micro-optical elements. For example, LED fl ash light shaping elements, the secondary camera, ambient light and proximity sensors. Wherever light is involved, micro-optics offers the chance to further miniaturize a device, to improve its performance, or to reduce manufacturing and packaging costs. Wafer-scale micro-optics fabrication is based on technology established by the semiconductor industry. Thousands of components are fabricated in parallel on a wafer. This review paper recapitulates major steps and inventions in wafer-scale micro-optics technology. The state-of-the-art of fabrication, testing and packaging technology is summarized.