Photonics

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.

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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, Photonics, Articles

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Simplified Optics and Controls for Laser Communications

NASA’s Jet Propulsion Laboratory, Pasadena, California 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: Tech Briefs, ptb catchall, Photonics, Briefs

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Coherent Detection of High-Rate Optical PPM Signals

Quantum-limited performance is achievable. NASA’s Jet Propulsion Laboratory, Pasadena, California 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: Tech Briefs, ptb catchall, Photonics, Briefs

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White-Light Whispering-Gallery-Mode Optical Resonators

Overlapping resonator modes are exploited to obtain wide, high-Q spectra. NASA’s Jet Propulsion Laboratory, Pasadena, California 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: Tech Briefs, ptb catchall, Photonics, Briefs

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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, Photonics, Articles

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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, Photonics, Articles

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