Tech Briefs

Manufacture of Sparse-Spectrum Optical Microresonators

Multiple units having the same spectral parameters could be produced. An alternative design for dielectric optical microresonators and a relatively simple process to fabricate them have been proposed. The proposed microresonators would exploit the same basic physical phenomena as those of microtorus optical resonators and of the microsphere optical resonators described in several prior NASA Tech Briefs articles. The resonances in such devices are associated with the propagation of electromagnetic waves along circumferential.paths in “whispering-gallery” modes. The main advantage afforded by the proposal is that the design and the fabrication process are expected to be amenable to production of multiple microresonators having reproducible spectral parameters — including, most notably, high values of the resonance quality factor (Q) and reproducible resonance frequencies.

Posted in: Briefs, TSP, Physical Sciences

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Exact Tuning of High-Q Optical Microresonators by Use of UV

Resonance frequencies can be shifted permanently by controlled amounts. In one of several alternative approaches to the design and fabrication of a "whispering-gallery" optical microresonator of high resonance quality (high Q), the index of refraction of the resonator material and, hence, the resonance frequencies (which depend on the index of refraction) are tailored by use of ultraviolet (UV) light. The principles of operation of optical microresonators, and other approaches to the design and fabrication of optical microresonators, have been described in prior NASA Tech Briefs articles, including the two immediately preceding this one.

Posted in: Briefs, TSP, Physical Sciences

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Graded-Index “Whispering-Gallery” Optical Microresonators

Improvements would include equidistant resonances and reduced evanescent field. Graded-index-of- refraction dielectric optical microresonators have been proposed as a superior alternative to prior dielectric optical microresonators, which include microspheres (described in several prior NASA Tech Briefs articles) and microtori wherein electromagnetic waves propagate along circumferential paths in “whispering-gallery” modes. The design and method of fabrication of the proposed microresonators would afford improved performance by exploiting a combination of the propagation characteristics of the whisperinggallery modes and the effect of a graded index of refraction on the modes.

Posted in: Briefs, TSP, Physical Sciences

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Thermally Stable Piezoelectric and Pyroelectric Polymers

Neither mechanical nor solvent treatment is necessary for orientation of polymer molecules. A class of thermally stable piezoelectric and pyroelectric polymers, and an improved method of making them, have been invented. These polymers can be used as substrates for a wide variety of electro- mechanical transducers, sensors, and actuators.

Posted in: Briefs, Materials

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Combustion Synthesis of Ca3(PO4)2 Net-Shape Surgical Implants

More-biocompatible materials are produced in fewer processing steps. ASelf-propagating high-temperature combustion synthesis (SHS) is the basis of a method of making components of porous tricalcium phosphate [Ca3(PO4)2] and related compounds in net sizes and shapes for use as surgical implants that are compatible with bone. Ca3(PO4)2-based materials are among those preferred for use in orthopedic, restorative, and reconstructive surgery. As explained below, the SHS method offers advantages over prior methods of manufacturing Ca3(PO4)2-based surgical implants.

Posted in: Briefs, TSP, Materials

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Robust Control for the Mercury Laser Altimeter

Mercury Laser Altimeter Science Algorithms is a software system for controlling the laser altimeter aboard the Messenger spacecraft, which is to enter into orbit about Mercury in 2011. The software will control the altimeter by dynamically modifying hardware inputs for gain, threshold, channel- disable flags, range- window start location, and range- window width, by using ranging information provided by the spacecraft and noise counts from instrument hardware. In addition, because of severe bandwidth restrictions, the software also selects returns for downlink. To reduce mission risk, the software incorporates three different modes of operation. The three modes are denoted as fixed, range-driven, and closedloop (or adaptive). The fixed mode provides fixed hardware inputs for all but the threshold. The range-driven mode receives and utilizes ranging information from the spacecraft regarding its slant range to the planet or asteroid. The adaptive mode is capable of improving upon the ranging information provided by the spacecraft by use of a closed-loop range-estimation algorithm. The software is sufficiently robust that it could be used on other missions, and in fact, this has already been proposed.

Posted in: Briefs, TSP, Software

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DAVE-ML Utility Programs

DAVEtools is a set of Java archives (*.jar files) that embodies tools for manipulating flight-dynamics models that have been encoded in dynamic aerospace vehicle exchange markup language (DAVE-ML). [DAVE-ML is an application program, written in Extensible Markup Language (XML), for encoding complete computational models of the dynamics of aircraft and spacecraft. The goal in the continuing development of DAVE-ML is to expedite the exchange and validation of dynamical models, via the Internet, in a manner that is consistent and is independent of computational-simulation facilities, computing languages, and simulation software.] At present, DAVEtools includes two tools: dave (a basic DAVE-ML parser), which generates a Java-based version of a model encoded in DAVE-ML and dave2sl, which builds on dave to create Simulink® representations of models encoded in DAVE-ML.

Posted in: Briefs, Software

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