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Showing papers in "SPIE milestone series in 1999"


Journal Article
TL;DR: In this article, the advantages of employing silicon as a mechanical material, the relevant mechanical characteristics of silicon, and the processing techniques which are specific to micromechanical structures are discussed.
Abstract: Single-crystal silicon is being increasingly employed in a variety of new commercial products not because of its well-established electronic properties, but rather because of its excellent mechanical properties. In addition, recent trends in the engineering literature indicate a growing interest in the use of silicon as a mechanical material with the ultimate goal of developing a broad range of inexpensive, batch-fabricated, high-performance sensors and transducers which are easily interfaced with the rapidly proliferating microprocessor. This review describes the advantages of employing silicon as a mechanical material, the relevant mechanical characteristics of silicon, and the processing techniques which are specific to micromechanical structures. Finally, the potentials of this new technology are illustrated by numerous detailed examples from the literature. It is clear that silicon will continue to be aggressively exploited in a wide variety of mechanical applications complementary to its traditional role as an electronic material. Furthermore, these multidisciplinary uses of silicon will significantly alter the way we think about all types of miniature mechanical devices and components.

2,707 citations


Journal Article
TL;DR: In this article, a CARS-based multiphoton microscopy based on coherent anti-Stokes Raman scattering (CARS) was proposed for high-resolution 3D sectioning.
Abstract: Confocal [1] and multiphoton [2] fluorescence microscopy have become powerful techniques for threedimensional imaging of chemical and biological samples, especially for live cells. This coincides with developments of various natural and artificial fluorescent probes for cellular constituents [3]. For chemical species or cellular components that either do not fluoresce or cannot tolerate labeling, infrared microscopy and spontaneous Raman microscopy can be used as contrast mechanisms based on vibrational properties. Conventional infrared microscopy is limited to low spatial resolution because of the long wavelength of light used. High resolution Raman microscopy of biological samples has been demonstrated with a confocal microscope [4]. However, the intrinsically weak Raman signal necessitates high laser powers (typically .10 mW) and is often overwhelmed by the fluorescence background of the sample. A multiphoton microscopy based on coherent anti-Stokes Raman scattering (CARS) [5] was put forward as an alternative way of providing vibrational contrast [6]. However, the sensitivity of CARS microscopy was limited by the nonresonant background signal, and high resolution three-dimensional sectioning was not achieved. In the study reported here, we demonstrate CARS microscopy in the chemically interesting vibrational spectral region around 3000 cm21 with high spatial resolution and three-dimensional sectioning capability. Most importantly, the use of near-infrared laser pulses generated by a Ti:sapphire laser s,855 nmd and an optical parametric oscillator/amplifier s,1.2 mmd allows a significant improvement in signal to background ratio in CARS detection. Unlike spontaneous Raman microscopy, the highly sensitive CARS microscopy requires only a moderate average power for excitation s,0.1 mWd, tolerable by most biological samples. CARS spectroscopy has been extensively used as a spectroscopic tool for chemical analyses in the condensed and gas phases [7]. In doing CARS spectroscopy, a pump laser and a Stokes laser beam, with center frequencies of np and nS , respectively, are spatially overlapped. The CARS signal at 2np 2 nS is generated in a direction determined by the phase-matching conditions. When the frequency difference np 2 nS coincides with the frequency of a molecular vibration of the sample, the CARS

1,341 citations


Journal Article
TL;DR: In this article, the authors describe the fabrication techniques, surface activity, atomic bonds, LIGA and SLIGA, and bury and destroy of miniature electromechanical sensors and actuators.
Abstract: Miniature electromechanical sensors and actuators can be mass produced on silicon wafers much like ICs. They combine readily with signal-processing circuitry into powerful tools that measure, analyze, and control their environments. The authors describe the fabrication techniques, surface activity, atomic bonds, LIGA and SLIGA, and bury and destroy. The following applications are discussed: pressure sensors, medical equipment, industrial/consumer equipment, avionics, and mechanical applications.<>

188 citations


Journal Article
TL;DR: In this article, the authors report on vertical mirrors fabricated by deep reactive ion etching of silicon, achieving an aspect ratio higher than 30.3/spl deg/m and a surface roughness below 40 nm rms.
Abstract: We report on vertical mirrors fabricated by deep reactive ion etching of silicon. The mirror height is 75 /spl mu/m, covering the fiber core of a single-mode fiber when the latter is placed into a groove of equal depth and etched simultaneously with the mirror. To obtain a uniform etch depth, etching is stopped on a buried oxide layer. Using the buried oxide as a sacrificial layer allows to fabricate mirrors with suspension and actuation structures as well as fiber-alignment grooves in one and the same processing step. A minimal mirror thickness of 2.3 /spl mu/m was achieved, resulting in an aspect ratio higher than 30. The verticality was better than 89.3/spl deg/. In the upper part of the mirror a surface roughness below 40 nm rms was obtained. At a wavelength of 1300 nm the reflectivity of the aluminum-coated mirrors was measured to be higher than 76%. Using a reactive ion etched mirror we have fabricated an optical fiber switch with electrostatic actuation. The coupling loss in the bar state of two packaged prototypes was between 0.6 and 1.7 dB and between 1.4 and 3.4 dB in the cross state. The switching time is below 0.2 ms.

163 citations


Journal Article
TL;DR: In this paper, the design, development, and performance of the digital micromirror device (DMD), a spatial light modulator for projection displays, are examined, which is a chip about 2.3 cm/sup 2/covered by 442368 movable mirrors, each 16 mu m on a side.
Abstract: The design, development, and performance of the digital micromirror device (DMD), a spatial light modulator for projection displays, are examined. The DMD covers each memory cell of a CMOS static RAM with a movable micromirror. Electrostatic forces contingent on the data in the cell tilt the mirror either on or off, modulating the light incident on its surface. Light reflected from any on-mirrors passes through a projection lens and creates images on a large screen. Light from the remaining off-mirrors is reflected away from the projection lens and trapped. The standard-resolution version of the DMD corresponds to the National Television System Committee (NTSC) or Phase Alternation Line (PAL) standard. It is a chip about 2.3 cm/sup 2/ covered by 442368 movable mirrors, each 16 mu m on a side. >

125 citations


Journal Article
TL;DR: In this article, the techniques used to fabricate micromechanical structures are described and the mechanical properties of silicon, which are important to these applications, are examined, including accelerometers, resonant microsensors, motors and pumps made by these techniques.
Abstract: The techniques used to fabricate micromechanical structures are described. Bulk micromachining is routinely used to fabricate microstructures with critical dimensions that are precisely determined by the crystal structure of the silicon wafer, by etch-stop layer thicknesses, or by the lithographic masking pattern. Silicon fusion bonding has been used to fabricate micro silicon pressure sensor chips. Surface micromachining, based on depositing and etching structural and sacrificial films, allows the designer to exploit the uniformity with which chemical vapor deposition (CVD) films coat irregular surfaces as well as the patterning fidelity of modern plasma etching processes. Silicon accelerometers, resonant microsensors, motors, and pumps made by these techniques are discussed. Measuring the mechanical properties of silicon, which are important to these applications, is examined. >

123 citations


Journal Article
TL;DR: In this article, the authors reported the fabrication of a wavelength tunable optical filter using surface micromachining technology, which can be readily integrated with surface emitting lasers, modulators, and detectors.
Abstract: We report the fabrication of a wavelength tunable optical filter using surface micromachining technology. The center wavelength is 1.517 /spl mu/m and the transmission bandwidth is 5 nm. The device with a 50-/spl mu/m diameter aperture has an optical loss of about 5 dB. A continuous wavelength tuning of 60 nm has been demonstrated. This device may find applications in optical sensing and wavelength division multiplexing systems, and can be readily integrated with surface emitting lasers, modulators, and detectors.

113 citations


Journal Article
TL;DR: In this article, a new free-space micro-optical bench (FSMOB) technology was proposed to reduce the size, weight, and cost of most optical systems, and could have a significant impact on optical switching, optical sensing and optical data storage systems as well as on the packaging of optoelectronic components.
Abstract: The surface-micromachining technique has been employed to fabricate novel three-dimensional micro-optical elements for free-space integrated optics. The optical axes of these optical elements are parallel to the substrate, which enables the entire free-space optical system to be integrated on a single substrate. Microscale Fresnel lenses, mirrors, beam splitters, gratings, and precision optical mounts have been successfully fabricated and characterized. In addition, micropositioners such as rotary stages and linear translational stages are monolithically integrated with the optical components using the same surface-micromachining process to provide on-chip optical alignment or optomechanical switching. Self-aligned hybrid integration with semiconductor edge-emitting lasers and vertical cavity surface-emitting lasers are also demonstrated for the first time. This new free-space micro-optical bench (FSMOB) technology could significantly reduce the size, weight, and cost of most optical systems, and could have a significant impact on optical switching, optical sensing and optical data-storage systems as well as on the packaging of optoelectronic components.

111 citations


Journal Article
TL;DR: In this paper, a self-assembled surface-micromachined micro-XYZ stage with large displacements and fine positioning accuracy has been demonstrated on a Si microoptical bench for optical scanning/alignment applications.
Abstract: A novel self-assembled, surface-micromachined micro-XYZ stage with large displacements and fine positioning accuracy has been demonstrated on a Si microoptical bench for optical scanning/alignment applications. Continuous lateral scanning up to 120 /spl mu/m and vertical scanning up to 250 /spl mu/m have been achieved with integrated scratch drive actuators (SDA), which have step resolutions of 27 nm. The XYZ stage can be fully assembled by applying an electric bias only. Focus adjustment of the micro-Fresnel lens integrated on the micro-XYZ stage has also been successfully demonstrated. This is useful for two-dimensional scanning, dynamic focusing/tracking, and fine optical alignment.

103 citations


Journal Article
TL;DR: In this paper, an InGaAs/AlGaAs vertical-cavity surface-emitting laser operating near 960 nm was used for continuous wavelength tuning of 15 nm.
Abstract: Continuous wavelength tuning of 15 nm was achieved micro‐electromechanically in an InGaAs/AlGaAs vertical‐cavity surface‐emitting laser operating near 960 nm. The device utilizes a micromachined deformable‐membrane top mirror suspended by an air gap above a p‐i‐n diode quantum well active region and bottom mirror. Applied membrane‐substrate bias produces an electrostatic force which reduces the air gap thickness and therefore tunes the lasing wavelength. Typical tuning bias ranged between 15 and 23 V, and the minimum threshold current was 35 mA for pulsed room‐temperature operation.

69 citations


Journal Article
TL;DR: The potential of on-chip optical processing and the recent achievement of free-space integrated optics and micro-optical bench components developed at UCLA, and DMDs developed at Texas Instruments are reviewed in this paper.
Abstract: Micro-optical components, such as diffractive and refractive microlenses, micromirrors, beamsplitters, and beam combiners, have recently received considerable attention in the optics R&D centers and finally in the manufacturing community. This achievement is due to micro-electro-mechanical (MEM) technology that has demonstrated major improvements in overall performance and cost of optical systems while offering the possibility of relativity rapid transition to products for military, industrial, and consumer markets. Because of these technology advances, an industrial infrastructure is rapidly becoming established to combine micro-optical components and MEM-based microactuators for on-chip optical processing. Optical systems that once were considered to be impractical due to the limitations of bulk optics can now easily be designed and fabricated with all required optical paths, signal conditioning, and electronic controls integrated on a single chip. On-chip optical processing will enhance the performance of devices such as focal-plane optical concentrators, smart actuators, color separators, beam shapers, fiber data distribution interface (FDDI) switches, digital micromirror devices (DMDs), and miniature optical scanners. We review advances in microoptical components developed at the Rockwell Science Center. We also review the potential of on-chip optical processing and the recent achievement of free-space integrated optics and micro-optical bench components developed at UCLA, and DMDs developed at Texas Instruments.

Journal Article
TL;DR: In this paper, surface micromachined corner cube reflectors made of 250 /spl mu/m square hinged polysilicon plates have been demonstrated to transmit digital signals over a range of 2 meters by reflecting an interrogating 5 mW laser.
Abstract: Surface micromachined corner cube reflectors made of 250 /spl mu/m square hinged polysilicon plates have been demonstrated to transmit digital signals over a range of 2 meters by reflecting an interrogating 5 mW laser. Measured reflectance ranges from 34% to 77% for different mirror designs. Divergence of light reflected by CCR ranges from 15-35 mrad. The CCRs are electrostatically actuated with 10 to 20 V. The highest data rate transmitted with a CCR is 1 Kbps.

Journal Article
TL;DR: In this paper, a surface-micromachined free-space fiber optic switch with integrated microactuators for optical fiber communication systems is presented, which consists of an out-of-plane micromirror driven by integrated scratch drive actuators and balanced by a spring.
Abstract: We report on a novel surface-micromachined free-space fiber optic switch with integrated microactuators for optical fiber communication systems. The switch consists of an out-of-plane micromirror driven by integrated scratch drive actuators, and balanced by a spring. A fall time and a rise time of 15 ms and 6 ms have been achieved, respectively. The switch is equipped with the fail-safe feature as required by the FDDI optical bypass switch. In addition, a vibration g-test has been conducted while the switch is transmitting data. Error free operation up to 89 g's has been achieved for vibration frequencies from 200 Hz to 10 kHz.

Journal Article
TL;DR: In this article, the design and fabrication of micromachined resonant scanners that have large scan angles at fast scan speeds are described and demonstrated as a laser-beam deflector in a barcode reader.
Abstract: This paper describes the design and fabrication of micromachined resonant scanners that have large scan angles at fast scan speeds. Driven by an electrostatic comb motor, these 200 /spl mu/m by 250 /spl mu/m scanning-micromirrors can scan about 12/spl deg/ (optical) at the resonance frequency of 3 kHz with a sinusoidal voltage input of 20 V in amplitude. Fabricated with a four-poly-layer silicon-surface-micromachining process, these resonant scanners are compact, extremely light in weight, and potentially very low in cost. The power consumption is also minimal since the capacitive motor draws very little current. We have demonstrated the scanner as a laser-beam deflector in a barcode reader, a potentially important application that has a growing popularity in many industries.

Journal Article
TL;DR: Merging microoptics, microelectronics, and micromechanics creates a new and broader class of micro-opto-electro-mechanical (MOEM) devices, which may attract additional industrial demonstrations of commercial devices such as torsional mirrors, laser scanners, optical shutters, and dynamic micromirror displays.
Abstract: Micro-optical devices such as diffractive and refractive microlenses fabricated using integrated circuit technology have been highlighted during the past five years. This scientific breakthrough has created a revolution in optical technology. Miniaturizing devices using microoptics promise to revolutionize many electrooptical systems-from video cameras, video phones, and compact disk data storage to robotic vision, optical scanners, and high-definition projection displays. The supporting technologies for these micro-optical systems, such as binary optics and plastic micro-replication, are built on existing or adapted integrated circuit technologies that have been developed over the past five years. In parallel with this optical technology revolution, researchers have also developed another frontier technology called micro-electro-mechanical (MEM). MEM technology has found applications in automotive, machine tools, airbag actuators, and many generic microsensors. Merging microoptics, microelectronics, and micromechanics creates a new and broader class of micro-opto-electro-mechanical (MOEM) devices, which may attract additional industrial demonstrations of commercial devices such as torsional mirrors, laser scanners, optical shutters, and dynamic micromirror displays. Both constituent technologies of MOEM devices have the potential of batch processing and embossed replication, which, again, makes them highly attractive for low-cost commercial applications. Other more complex microsystems that use MOEM devices such as microspectrometers, microinterferometers, and miniature on-machine-inspection subsystems are being investigated. This new technology enables high-performance devices for microsensor systems that are lighter, easier to produce, more efficient, and less expensive than conventional components.

Journal Article
TL;DR: In this paper, a surface micromachining process, using an oxide sacrificial layer and poly/nitride/poly membranes, has been developed for light modulators integrated on the same chip as the signal processing.
Abstract: The development of compact light modulators integrated on the same chip as the signal processing opens many opportunities for combining inter-chip optical communications with standard silicon circuitry. The use of surface micromachining allows high speed of operation and small size integration with other circuitry. The optical and mechanical requirements for the devices also have to be considered, to ensure compatability with standard silicon processing. A surface micromachining process, using an oxide sacrificial layer and poly/nitride/poly membranes, has been developed. This paper presents the optical and mechanical considerations in the development of a compact micromachined silicon Fabry-Perot interferometer. Initial tests have shown that these micromachined membranes represent a compact and effective light modulating method.

Journal Article
TL;DR: In this paper, the theoretical limits of performance of MEM-DMs for controlling fixed aberrations in optical systems were explored, and an alternative design that uses a lenslet array in conjunction with the MEM-DM was shown through theoretical studies to provide superior aberration correction with lower residual effects due to diffraction.
Abstract: Micro-electro-mechanical deformable mirrors (MEM-DMs) are solid-state electronic devices with small, movable reflective surface elements that can be used to manipulate the phase of optical wavefronts. MEM-DMs differ from more conventional continuous-facesheet deformable mirrors in that the movable surface of a MEM-DM consists of a set of segmented moving surfaces. The segmented, reflective surfaces of a MEM-DM give rise to larger diffraction effects than those provided by continuous-facesheet deformable mirrors. However, MEM-DMs are still attractive due to their low cost and the low drive voltages. We explore the theoretical limits of performance of MEM-DMs for controlling fixed aberrations in optical systems, and we present laboratory results demonstrating reduction of a fixed aberration using a MEM-DM device. Results presented here show that while a MEM-DM does provide some degree of aberration control, diffraction effects arising from the static support structures of the MEM-DM surface are significant. An alternative design that uses a lenslet array in conjunction with the MEM-DM is shown through theoretical studies to provide superior aberration correction with lower residual effects due to diffraction.


Journal Article
TL;DR: The DMD is a semiconductor light switch which is making an impact in digital light processingTM (DLP) applications as mentioned in this paper, and it is the world's largest micro-electro-mechanical structures (MEMS) device with chips ranging from 442-thousand to 2.3 million moving mirrors.
Abstract: The DMD is a semiconductor light switch which is making an impact in digital light processingTM (DLP) applications. It is the world's largest micro-electro-mechanical structures (MEMS) device with chips ranging from 442-thousand to 2.3 million moving mirrors. The DMD operates in a bistable (binary) mode and fully supports the movement to all-digital display systems. Currently, DMD devices are being used to develop a family of projection display products. An overview of digital light processing systems will be given with emphasis on the performance of the first prototypes using this technology, including their value propositions. Finally, the general markets served by this technology, along with the advantages DMD technology offers, will be discussed.

Journal Article
TL;DR: In this paper, a silicon-based, surface micromachined, deformable mirror device for optical applications requiring phase modulation, including adaptive optics and pattern recognition systems is described.
Abstract: A silicon-based, surface micromachined, deformable mirror device for optical applications requiring phase modulation, including adaptive optics and pattern recognition systems is described. The mirror will be supported on a massively parallel system of electrostatically con- trolled, interconnected microactuators that can be coordinated to achieve precise actuation and control at a macroscopic level. Several genera- tions of individual actuators as well as parallel arrays of actuators with segmented/continuous mirrors have been designed, fabricated, and tested. Deflection characteristics and pull-in behavior of the actuators have been closely studied. Devices have been characterized with regard to yield, repeatability, and frequency response. An electromechanical model of the system has been simulated numerically using the shooting method, and good correlation with experimental results has been ob- tained. A twenty-channel parallel control scheme has been developed

Journal Article
TL;DR: In this paper, a rotary stage, a collimating micro-Fresnel lens, and an edge-emitting laser held by three-dimensional alignment structures on a single Si substrate are demonstrated.
Abstract: Free‐space micro‐optical systems on a chip containing three‐dimensional microgratings have been demonstrated using surface‐micromachining technique. The micrograting is integrated with a rotary stage, a collimating micro‐Fresnel lens, and an edge‐emitting laser held by three‐dimensional alignment structures on a single Si substrate. Diffraction patterns for various grating rotation angles are observed. Another optical interconnect module consisting of three cascaded microgratings is also demonstrated. The micrograting is a basic building block for many micro‐optical systems and is very attractive for applications in microspectrometers, free‐space optical interconnect, optoelectronic packaging, and wavelength‐division multiplexed integrated micro‐optical systems.

Journal Article
TL;DR: In this article, the authors present the methods used to fabricate a micromechanical silicon optical modulator for use in a fiber-to-the-home (FTH) applications.
Abstract: We present the methods used to fabricate a micromechanical silicon optical modulator for use in a fiber-to-the-home applications. We emphasize the efforts made to realize a practical, robust, manufacturable, and easily packaged device. In addition, recent speed, temperature stability, and reliability results are presented. Rise and fall times of 132 and 125 ns, respectively, have been observed in response to a square wave drive signal. The device has been temperature cycled from -50/spl deg/C to 90/spl deg/C and shown greater than 10-dB optical contrast ratio over this temperature range. Finally, the device has been cycled at 500 kHz for a period of nearly two months (two-trillion cycles) without a noticeable loss in performance.


Journal Article
TL;DR: This paper reports on the Texas Instruments implementation of a limited-addressability flexure-beam device that has a fill factor up to 74.3% and provides a dc shield for the analog signal on the mirror and requires 30 V to modulate the 2π phase modulation of a 633-nm wavelength using an optical-bench setup.
Abstract: The phase-only spatial light modulator (SLM) is a highly efficient component for the filter plane of a real-time autocorrelator.'3 Texas Instruments has developed several SLMs using micromechanical mirror elements.4 The basic structure of the flexure-beam micromechanical element that we implement in this research is shown in Fig. 1 .Themirror element consists of a square reflecting plate attached at four points to L-shaped flexure hinges. The hinges are attached to four posts that provide the main mechanical support and electrical contact for the element. Each post also mechanically supports four hinges that attach to four different mirrors. The pixel is attracted downward by electrostatic force when it is addressed. The vertical motion of the mirror changes the length of the optical path at the pixel and hence the phase information. There are two approaches to building such a micromirror device: (1) addressing at the mirror through the post and hinge, or (2) addressing at the bottom electrode of the spacer. The advantage of using the first approach is the reduction of capacitance feedthrough caused by a nearby underlayer that carries signals. This approach has a smaller active optical area, because a larger post is needed to provide an electrical signal on one hinge while isolating the signal from the three others. Our chip uses the first approach. The next two sections briefly describe the chip architecture and process flow with a cross section of the flexure-beam micromirror device. The fourth section illustrates the modeling effort for this device. The fifth section then summarizes the characterization and performance of the device.

Journal Article
TL;DR: In this paper, two different technologies for deformable micromirror devices as phase-modulating light valves for high-resolution optical applications are reported, which are compatible with a 30 V CMOS technology for active matrix addressing.
Abstract: We report on two different technologies for deformable micromirror devices as phase-modulating light valves for high-resolution optical applications. Both technologies are compatible with a 30 V CMOS technology for active matrix addressing. We have developed and fabricated a 512 × 464 pixel light valve with CMOS addressing and viscoelastic layer deformable mirrors on top. The performance of the light valve has been demonstrated by an application for fast submicron laser direct writing. Furthermore, we report promising results on cantilever-type deformable mirrors to be integrated with the CMOS active matrix.

Journal Article
TL;DR: In this paper, a novel microactuated micro-XYZ stage with large travel distance and fine positioning capability has been demonstrated using the surface-micromachining technology, consisting of three in-plane translation stages driven by integrated scratch drive actuators.
Abstract: A novel microactuated micro-XYZ stage with large travel distance and fine positioning capability has been demonstrated using the surface-micromachining technology. The micro-XYZ stage consists of three in-plane translation stages driven by integrated scratch drive actuators. Two vertically stacked 45/spl deg/ micromirrors in orthogonal directions are employed to achieve vertical beam adjustment without using vertical actuators. Large travel distance (>30 /spl mu/m) and fine moving steps (11 nm) have been achieved experimentally in all three directions. The micro-XYZ stage can be monolithically integrated with the surface-micromachined microlenses, or other out-of-plane micro-optical elements, for optical alignment or reconfiguration in free-space micro-optical benches (FSMOB).

Journal Article
TL;DR: In this article, a two-dimensional optical scanner suitable for integration in a plane structure has been developed, where bimorph cells are used as the actuator to excite the torsional vibration.
Abstract: A two-dimensional optical scanner suitable for integration in a plane structure has been developed. To make it vibration robust, a torsional vibration system with two degrees of freedom is adopted for the resonator, and the vibration system axis is matched to the center of gravity. Bimorph cells are used as the actuator to excite the torsional vibration. This optical scanner is capable of optical scanning in two orthogonal directions independently or simultaneously at a scanning angle of +30 degrees or more. One-dimensional scanning is enabled by driving the bimorph cells with the resonance frequency of either of the two torsional vibrations. Two-dimensional scanning is achieved if the bimorph cells are operated by adding the resonance frequency signals of the two torsional vibrations.



Journal Article
TL;DR: In this article, a segmented microelectromechanical deformable mirror was used in conjunction with a refractive lenslet array to correct a quadratic aberration with an extreme spherical aberration.
Abstract: Quadratic aberration is successfully corrected with a segmented microelectromechanical deformable mirror in conjunction with a refractive lenslet array. Use of the lenslet array greatly improves the effective fill factor of the correcting element. Experimental results show correction approaching the diffraction limit for an extreme spherical aberration.