The current invention provides for encapsulated release structures, intermediates thereof and methods for their fabrication. The multi-layer structure has a capping layer, that preferably comprises silicon oxide and/or silicon nitride, and which is formed over an etch resistant substrate. A patterned device layer, preferably comprising silicon nitride, is embedded in a sacrificial material, preferably comprising polysilicon, and is disposed between the etch resistant substrate and the capping layer. Access trenches or holes are formed in to capping layer and the sacrificial material are selectively etched through the access trenches, such that portions of the device layer are release from sacrificial material. The etchant preferably comprises a noble gas fluoride NGF 2x (wherein Ng=Xe, Kr or Ar: and where x=1, 2 or 3). After etching that sacrificial material, the access trenches are sealed to encapsulate released portions the device layer between the etch resistant substrate and the capping layer. The current invention is particularly useful for fabricating MEMS devices, multiple cavity devices and devices with multiple release features.

Microelectronic mechanical system and methods

An adjustable diffractive light modulator is used to equalize the power level of wavelength multiplexed signals in wavelength division multiplexing applications. An optical channel transmits a multi-wavelength input signal through a wavelength demultiplexer. The input signal comprises a plurality of component signals defined according to a plurality of wavelengths. The de-multiplexer spatially separates the multi-wavelength input signal into its respective plurality of component signals, which are transmitted through a plurality of optical channels onto a plurality of controllable diffractive light modulators. The diffractive light modulators are advantageously comprised of grating light valves. Component signals are reflected off their respective diffractive light modulators and collected in a plurality of optical channels for re-transmission into a wavelength multiplexer. The reflected signals are combined through a multiplexing process and transmitted as an output beam. Control of the diffractive light modulator is achieved by sensors measuring the power level of signals passing through the plurality of optical channels. The measured power levels of light are converted to digital values which are input into an electronic controller for processing. Control output signals from the controller are used to independently control individual pixels within the diffractive light modulator to equalize the reflected light signals.

Method and apparatus for dynamic equalization in wavelength division multiplexing

A method and apparatus for reducing speckle uses polarization averaging. A polarizing beam splitter divides a first polarized laser output into a second polarized laser output and a third polarized laser output. A plurality of mirrors creates an optical path difference between the second and third polarized laser outputs. The optical path difference is at least about a coherence length for the first polarized laser output. The second and third polarized laser outputs are combined into a fourth laser output, which illuminates an depolarizing screen. If a human eye or an optical system having a intensity detector views the depolarizing screen, the eye or the intensity detector will detect reduced speckle, which results from uncorrelated speckle patterns created by the second polarized laser output and the third polarized laser output.

Method and apparatus for reducing laser speckle using polarization averaging

A device comprising movable micro-structures configured to contact a substrate is disclosed. The substrate has a metal-insulator-metal construction with an upper metal layer and an insulator being patterned to provide substrate contact regions to a lower metal layer. The micro-structures have metal under layers for providing ribbon contact regions and non-contact regions. In use, a bias voltage is applied across the micro-structures and the top metal layer of the substrate causing the micro-structures and the substrate to contact through the contact regions. During contact, the contact regions are maintained at a potential that is substantially less than the applied bias voltage, thereby reducing the formation of asperities and/or sticking between contacting parts. The micro-structures are preferably ribbon structures in an optical MEM device configured to modulate light.

Reduced formation of asperities in contact micro-structures

An optical MEM device is fabricated with a patterned device layer formed on a silicon wafer. Preferably, the patterned device layer is patterned with plurality of ribbons and/or access trenches. The central portion of the ribbon is released from the silicon wafer using a selective etch process, wherein a cavity is formed under the central portion of the ribbon, while opposing ribbon ends remain attached to the wafer. The selective etching process preferably utilizes an enchant comprising xenon difluoride. In accordance with further embodiments, the silicon wafer is doped, patterned or otherwise modified to enhance the selectivity of the etching process.

Silicon substrate as a light modulator sacrificial layer

The present article reports a new technique for elimination of speckle noise. The method is based on the fact that if the state of polarisation of the illuminating beam is changed the microstructure of the speckle produced by a diffused object changes. Experi¬mental results have been presented.

Reduction of Speckle Noise by Varying the Polarisation of Illuminating Beam

The phenomenon of the shift of the far field diffraction pattern when a small aperature is half-covered with a transparent or partly transmitting film, which has been called the “Talbot effect”, has been studied in detail for dielectric and metallic films. The physical shifts of the central maximum and the first minimum, as well as the variation of relative irradiances at fixed points in the far field have been specifically investigated. Experimental results have been presented to confirm this phenomenon and to illustrate the application of the effect to the measurement of thickness of thin barium stearate and aluminium films. The results show that the effect can be used for the determination of thickness of thin films of known optical constants.

The Talbot Effect and its Use in the Diffractometry of Thin Films

Experimental results presented in the paper conclusively demonstrate that the technique of simulating apodizers by binary filters offers a relatively simple but effective method of practical fabrication of optimum apodizers.

Binary Apodizers - an Experimental Study

Possibilities of simulating an optimum apodizer by binary filters are explored. Numerical computations show that the binary filters provide a fairly close estimate of performance of the grey level apodizers.

A Feasibility Study on Binary Apodizers

A novel set-up for a fibre-optic medium-to-moderately high pressure sensor using the rotation of the polarization in monomode optical fibre due to geometric effect, has been presented. The presure sensing part consists of a small length single mode fibre, shaped into a single-turn, helix, wound over a cylinder made of rubberised material. The applied pressure changes the pitch of the helix and hence the plane of polarization of the light output is rotated. Besides simplicity, the excellent feature of the proposed sensor is that the sensing fibre does not at all make any direct physical contact with the pressure transmitting mechanism, and it is conceptually capable to being used in any high pressure range.

P. C. Kundu

Papers

Reduction of Speckle Noise by Varying the Polarisation of Illuminating Beam

The Talbot Effect and its Use in the Diffractometry of Thin Films

Binary Apodizers - an Experimental Study

A Feasibility Study on Binary Apodizers

Fibre-Optic Medium-To-moderately High Pressure Sensor Using The Polarization Change In Single Mode Fibre Due To Geometrical Effect