Photonics/Optics

Pointing Reference Scheme for Free-Space Optical Communications Systems

A scheme is proposed for referencing the propagation direction of the transmit laser signal in pointing a free-space optical communications terminal. This recently developed scheme enables the use of low-cost, commercial silicon-based sensors for tracking the direction of the transmit laser, regardless of the transmit wavelength. Compared with previous methods, the scheme offers some advantages of less mechanical and optical complexity and avoids expensive and exotic sensor technologies.

Posted in: ptb catchall, Tech Briefs, Briefs, TSP, Photonics, Lasers, Optics, Sensors and actuators, Telecommunications, Lasers, Optics, Sensors and actuators, Telecommunications
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Single-Phase Rare-Earth Oxide/Aluminum Oxide Glasses

Glasses that comprise rare-earth oxides and aluminum oxide plus, optionally, lesser amounts of other oxides, have been invented. The other oxide(s) can include SiO2, B2O3, GeO2, and/or any of a variety of glass-forming oxides that have been used heretofore in making a variety of common and specialty glasses. The glasses of the invention can be manufactured in bulk single-phase forms to ensure near uniformity in optical and mechanical characteristics, as needed for such devices as optical amplifiers, lasers, and optical waveguides (including optical fibers). These glasses can also be formulated to have high indices of refraction, as needed in some of such devices.

Posted in: ptb catchall, Tech Briefs, Briefs, Photonics, Molding, Composite materials, Glass, Refractory materials
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Distributed Intelligence Drives High-Energy Laser Manufacturing

Historically, high-energy (Joule-class) nanosecond YAG lasers have been confined primarily to laboratory research facilities and government labs. System designs were unique for each facility and the low number of systems worldwide made the learning curve for system improvement slow. It is only in recent years that the maturity of the technology has reached a state that makes it possible to consider these lasers for industrial applications.

Posted in: Features, ptb catchall, Articles, Photonics, Lasers, Lasers, Manufacturing equipment and machinery, Industrial vehicles and equipment
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DFM Your Device? Simulation Is the Answer

Design for Manufacturing (DFM) has taken off like a rocket in the electronics industry in recent years. Performing process and device simulations on CMOS transistors in a DFM flow have proven to be important in shortening the design cycle and reducing the production cost by improving yield. These are the key elements to why DFM mans the gate to the success of semiconductor foundries and companies.

Posted in: Features, ptb catchall, Articles, Photonics, CAD / CAM / CAE, CAD, CAM, and CAE, Transistors, Transistors, Product development, Semiconductors
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HBLEDs: Tackle Your Silicone Packaging Problems

It is widely known that the light emitting diode (LED) R&D and commercialization community is striving to produce higher power, bright-white-light LEDs. From both a temperature and UV-resistance standpoint, silicone is rapidly becoming the material of choice for the next-generation chip encapsulant. But as LED manufacturers look to employ silicones in their manufacturing processes, they must be aware of potential problems. Cure inhibition can lead to unacceptable variations in the manufacturing process and thus, the finished product. This article takes a brief look at the benefits of using silicones in high-brightness LED (HBLED) applications, with a focus on potential production floor issues and their solutions.

Posted in: Features, ptb catchall, Articles, Photonics, Light emitting diodes (LEDs), Light emitting diodes (LEDs), Forming, Packaging, Silicon alloys
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Simplified Optics and Controls for Laser Communications

A document discusses an architecture of a spaceborne laser communication system that provides for a simplified control subsystem that stabilizes the line of sight in a desired direction. Heretofore, a typical design for a spaceborne laser communication system has called for a high-bandwidth control loop, a steering mirror and associated optics, and a fast steering mirror actuator to stabilize the line of sight in the presence of vibrations. In the present architecture, the need for this fast steering-mirror subsystem is eliminated by mounting the laser-communication optics on a disturbance-free platform (DFP) that suppresses coupling of vibrations to the optics by ≥60 dB. Taking advantage of microgravitation, in the DFP, the optical assembly is free-flying relative to the rest of the spacecraft, and a low-spring-constant pointing control subsystem exerts small forces to regulate the position and orientation of the optics via voice coils. All steering is effected via the DFP, which can be controlled in all six degrees of freedom relative to the spacecraft. A second control loop, closed around a position sensor and the spacecraft attitude-control system, moves the spacecraft as needed to prevent mechanical contact with the optical assembly.

Posted in: ptb catchall, Tech Briefs, Briefs, TSP, Photonics, Architecture, Lasers, Optics, Telecommunications, Architecture, Lasers, Optics, Telecommunications, Vibration, Vibration
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Coherent Detection of High-Rate Optical PPM Signals

A method of coherent detection of high-rate pulse-position modulation (PPM) on a received laser beam has been conceived as a means of reducing the deleterious effects of noise and atmospheric turbulence in free-space optical communication using focal-plane detector array technologies. In comparison with a receiver based on direct detection of the intensity modulation of a PPM signal, a receiver based on the present method of coherent detection performs well at much higher background levels.

Posted in: ptb catchall, Tech Briefs, Briefs, TSP, Photonics, Mathematical analysis, Lasers, Lasers, Performance tests, Turbulence
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White-Light Whispering-Gallery-Mode Optical Resonators

Whispering-gallery-mode (WGM) optical resonators can be designed to exhibit continuous spectra over wide wavelength bands (in effect, white-light spectra), with ultrahigh values of the resonance quality factor (Q) that are nearly independent of frequency. White-light WGM resonators have potential as superior alternatives to (1) larger, conventional optical resonators in ring-down spectroscopy, and (2) optical-resonator/electro-optical modulator structures used in coupling of microwave and optical signals in atomic clocks. In these and other potential applications, the use of white-light WGM resonators makes it possible to relax the requirement of high-frequency stability of lasers, thereby enabling the use of cheaper lasers.

Posted in: ptb catchall, Tech Briefs, Briefs, TSP, Photonics, Lasers, Optics, Spectroscopy, Lasers, Optics, Spectroscopy
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Middleware Bridges the Optical/Mechanical Design Gap

Mechanical CAD (computer-aided design) programs have become very sophisticated during the past few years. Unfortunately, there is still a portion of the engineering spectrum that cannot be handled well in a traditional CAD program: optical modeling. If you are creating a complicated optical system (think of a camera zoom lens), then it is best to perform almost all of the design in a specialized optical design software program and then transfer the optical design to a CAD program for the later stages of the design process where items like housings, threads, cams, and motors are designed and integrated into the model.

Posted in: Features, ptb catchall, Articles, Photonics, CAD / CAM / CAE, CAD, CAM, and CAE, Design processes, Optics, Optics
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Photonics Tech Briefs Presents 2005 Products of the Year

Photonics Tech Briefs (PTB) recently presented the 2005 Readers’ Choice Products of the Year at a special awards dinner held at The Water Club in New York City. The top three products chosen by the readers of PTB were honored at the event.

Posted in: Features, ptb catchall, Articles, Photonics, Optics, Sensors and actuators, Optics, Sensors and actuators, Product development
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