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Cantilevers with interferometric high bandwidth force sensors can resolve nonlinear tip-sample interaction forces in tapping-mode atomic force microscopy. In this paper, we provide a detailed analysis of time-resolved force measurements using such cantilever. We first model the probe as a coupled spring-mass system and investigate its steady state dynamics under tapping-mode imaging conditions. Next, we analyze the optical response of the interferometric force sensor: Diffraction patterns as a function of tip displacement are obtained both analytically and by simulations. Finally, the frequency response of the force sensor is calculated, and the effects of the sensor geometry variations on the sensor mechanical response are analyzed. [ABSTRACT FROM AUTHOR]

Small interfering RNAs (siRNAs) can be designed to specifically and potently target and silence a mutant allele, with little or no effect on the corresponding wild-type allele expression, presenting an opportunity for therapeutic intervention. Although several siRNAs have entered clinical trials, the development of siRNA therapeutics as a new drug class will require the development of improved delivery technologies. In this study, a reporter mouse model (transgenic click beetle luciferase/humanized monster green fluorescent protein) was developed to enable the study of siRNA delivery to skin; in this transgenic mouse, green fluorescent protein reporter gene expression is confined to the epidermis. Intradermal injection of siRNAs targeting the reporter gene resulted in marked reduction of green fluorescent protein expression in the localized treatment areas as measured by histology, real-time quantitative polymerase chain reaction and intravital imaging using a dual-axes confocal fluorescence microscope. These results indicate that this transgenic mouse skin model, coupled with in vivo imaging, will be useful for development of efficient and ‘patient-friendly’ siRNA delivery techniques and should facilitate the translation of siRNA-based therapeutics to the clinic for treatment of skin disorders.Gene Therapy (2009) 16, 963–972; doi:10.1038/gt.2009.62; published online 28 May 2009 [ABSTRACT FROM AUTHOR]

This paper describes a free-space 1 timesP cyclically tunable optical multiplexer based on a stationary tunable blazed grating (TBG). An analytical model is used in deriving a closed- form expression for the transmission of the deformable grating, given an actuation scheme that requires only (P -1) control signals. A 1 times3 demultiplexer is implemented using a six-element TBG, and tuning over a free spectral range of 13.5 nm in C-band is demonstrated. [ABSTRACT FROM PUBLISHER]

This paper reports on a superresolution digital image enhancement technique using subpixel image translation with a scanning micromirror. We demonstrate that the spatial resolution of digital photomicrography, employing typical black-and-white pixelated image sensors, can be improved by acquiring multiple images with predetermined subpixel shifts and combining them with a superresolution image reconstruction algorithm. A two-axis gimbaled micromirror fabricated with a bulk-micromachining process is used to control the translational image displacements with subpixel accuracy [ABSTRACT FROM PUBLISHER]

In this paper, we present a single-crystal-silicon (SCS) continuous membrane deformable mirror (DM) as a corrective adaptive-optics (AO) element for space-based telescopes. In order to correct the polishing errors in large aperture (~8 m) primary mirrors, a separate high-quality surface DM array must be used. Up to 400000 elements and a mirror stroke of ~100 nm are required for the correction of these polishing errors. A continuous membrane mirror formed by the the SCS device layer of a silicon-on-insulator (SOI) wafer is used to achieve a high-quality optical surface and to minimize the additional diffractive effects in the optical system. To achieve substantial local deformation needed to correct high-order errors, we use a highly deformable silicon membrane of 300-nm thickness. This thin membrane is able to deform locally by 125 nm at an operating voltage of 100 V with a pixel pitch of 200 mum. The resonance frequency of a pixel is 25 kHz with a low Q-factor of 1.7 due to squeeze-film damping. The device is fabricated by processing the microelectromechanical system (MEMS) and electronic chips separately and then combining them by flip-chip bonding. This allows optimization of the MEMS and electronics separately and also allows the use of an SOI layer for the mirror by building the MEMS bottom up. A small prototype array of 5times5 pixels with 200-mum pitch is fabricated, and we demonstrate single pixel and multiple pixel actuation [ABSTRACT FROM PUBLISHER]

In this paper, we present a piston-type spatial light modulator (SLM) as a programmable optical pattern generator for maskless lithography. The SLM is a dual-lever-type actuator with pixel-overlapping springs to achieve low voltage actuation with a small capacitor area. Large arrays of up to ~40000 mirrors with 20-mum pixels and ~17000 mirrors with 30-mum pixels have been fabricated. The arrays have various prewired configurations to alleviate the need to control all the pixels individually. The mirrors have high resonance frequencies for fast response and achieve deflections of lambda/2 (lambda=193 nm for 20-mum pixels and lambda=633 nm for 30-mum pixels) at voltages less than 100 V. The mirrors are fabricated using thin-film processing and chemical mechanical polishing of the reflector layer. Using the SLM in an aerial imaging system, we demonstrate the generation of dark lines, dark areas, linewidth modulation, and subgrid positioning. We also demonstrate compensation of image shifts due to through-focus wafer drift using a double exposure (or phase-compensated exposure) technique [ABSTRACT FROM PUBLISHER]

We report on a tunable optical bandpass filter with precise and independent control of its optical bandwidth and center wavelength. The optical filter is based on a double-pass monochromator configuration and a variable-aperture microelectromechanical systems (MEMS) reflector with two blocking micromirrors that manipulate the optical passband. The MEMS reflector is fabricated on the sidewalls of (110) silicon-on-insulator material by a combination of wet etching and deep reactive ion etching. The 1-dB optical bandwidth is continuously tunable from 3.65 to 6.35 nm by changing the position of the blocking micromirrors with lateral combdrive actuators. The center wavelength can be accurately controlled within a 30-nm spectral range by rotating the diffraction grating and/or changing the center location of the variable aperture with the combdrive actuators. The measured group delay variation across the passband was negligible [ABSTRACT FROM PUBLISHER]

The intensive investment in optical microelectromechanical systems (MEMS) in the last decade has led to many successful components that satisfy the requirements of lightwave communication networks. In this paper, we review the current state of the art of MEMS devices and subsystems for lightwave communication applications. Depending on the design, these components can either be broadband (wavelength independent) or wavelength selective. Broadband devices include optical switches, crossconnects, optical attenuators, and data modulators, while wavelength-selective components encompass wavelength add/drop multiplexers, wavelength-selective switches and crossconnects, spectral equalizers, dispersion compensators, spectrometers, and tunable lasers. Integration of MEMS and planar lightwave circuits, microresonators, and photonic crystals could lead to further reduction in size and cost [ABSTRACT FROM PUBLISHER]

We present a micromechanical grating array that acts as a configurable optical filter for low-cost and compact visible and near-infrared spectrometric sensors. We show how the grating array can be used either as a fast scanning monochromator or as a diffractive filter, and that the expected signal-to-noise ratio is approximately equal for the two modes of measurement. The free spectral range of the filter can be matched to a defined spectral measurement region, so that we can optimize the relationship between spectral resolution and electromechanical complexity. We have numerically studied diffraction efficiency and errors in filter shape. Finally, we fabricated a small configurable grating array and present measurement results that demonstrate electrostatic filter modulation. [ABSTRACT FROM PUBLISHER]

We present tunable optical filters based on a modified Gires-Tournois interferometer. The back reflection plane of the interferometer is replaced with a one-dimensional micromirror array for phase modulation. Using Gaussian beam optics, we show that the transfer function of the device has the form of the transversal filter in digital signal processing. The design and analysis techniques of conventional digital filters can, therefore, be adapted to tunable optical filters. Both the amplitude and phase of the transfer function can be controlled by reconfiguring the micromirrors. Application examples in dispersion compensation and variable bandwidth bandpass filtering are discussed and experimentally demonstrated. [ABSTRACT FROM PUBLISHER]

We demonstrate high-resolution, raster-scanning display systems based on pairs of orthogonally scanning, surface-micromachined mirrors. The first mirror of the raster-scanning pair determines the line-scan rate of the display and is driven at its resonant frequency which is on the order of 4.7 kHz. The second mirror, driven at a frequency below its resonance and scanning orthogonally to the first mirror, determines the image refresh rate. Both mirrors have a maximum optical scanning angle of 15°. Single-chip and two-chip scanners are demonstrated. The resolution of the single-chip display, based on average pixel size, is 102×119 pixels. The curvature of the mirror surfaces are characterized and optically compensated to achieve this resolution [ABSTRACT FROM PUBLISHER]

A multi-functional microelectromechanical system (MEMS) tunable optical filter as an amplified spontaneous emission (ASE) rejection filter in an optical communication system is presented. The MEMS tunable filter can tune both the centre wavelength and the passband independently and continuously in C-band. This filter was applied to a 10 Gbit/s system and system-performance improvement by adjusting the amount of ASE noise rejection was observed. [ABSTRACT FROM AUTHOR]

We present a micromachined cantilever with an integrated high-bandwidth resonator for direct measurement of tip-sample interaction forces in tapping-mode atomic force microscopy. Force measurements are achieved by a diffraction grating that serves as a differential displacement sensor for the tip motion relative to the cantilever body. Time-resolved tip-sample interaction force measurement is demonstrated on a silicon sample following calibration of the probe structure. By using lock-in detection, the harmonics of periodic tip-sample interaction have been utilized to obtain high-contrast, material specific images. The harmonic images of patterned silicon/silicon nitride control samples and triblock copolymers are presented. [ABSTRACT FROM AUTHOR]

A wavelength-selective optical switch based on waveguide grating routers (WGRs), passive splitters, and combiners is described. Tunable lasers on the transmitter side are the only active switching elements. The WGR is operated on multiple free-spectral ranges (FSRs) to achieve increased port count and switching capacity. Switching times of less than 24 ns between wavelengths covering three FSRs are demonstrated experimentally. [ABSTRACT FROM PUBLISHER]

We demonstrate system level performance and rapid switching (10 mus) of a 1times3 wavelength multiplexer/demultiplexer (mux/demux) based on a Gires-Tournois interferometer with cyclically tunable center wavelengths. Group delay ripple within the passband is measured to be <8 ps. Less than 0.5-dB power penalty is observed for 10-Gb/s data propagating through the demux. Additionally, rapid optical code-division multiple-access code hopping using this tunable demux has been shown [ABSTRACT FROM PUBLISHER]

We have fabricated and characterized a micromechanical Fresnel lens that serves as a reconfigurable filter for near-infrared spectrometry, for the analysis of gas, liquids, or solids. The lens consists of silicon segments that can be individually actuated. Moving the segments vertically controls the spectrum of the light that is focused on a detector. The holographic pattern on top of the segments permits both focusing of the light and spectral control. We have demonstrated experimentally the desired spectral control of the filter. [ABSTRACT FROM PUBLISHER]

This letter describes a free-space optical fiber cross-connect that uses a pair of micromirror arrays to redirect optical beams from an input-fiber array to an output array. This confocal switch architecture is well suited for simultaneous switching of multiple wavelength channels. We show that confocal switches with low insertion loss, low crosstalk, and large port counts can be implemented with surface-micromachined mirror arrays, and we demonstrate a 2×2 single-mode (1550 nm) switch configuration with insertion loss of -4.2 dB and crosstalk of -50.5 dB. Our micromirror design has sufficient size and angular deflection for scaling to 32×32 ports [ABSTRACT FROM PUBLISHER]

Examines the modulation efficiency of an attenuated total internal reflection light modulator. Effects of electric field application across the electro-optic film on the reflective light; Impact of ghost reflections on the degree of reflectance; Use of electro-optic materials in obtaining high modulation index.