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Flexible Laser Design Targets Low-Volume Material Processing Needs

A flexible approach to diode-pumped laser design combines customized performance with cost-effective manufacturing. Coherent, Inc., Santa Clara, California Q-switched, diode-pumped solid-state lasers with an end-pumped cavity design are now widely used in micromachining, materials processing, marking, and related applications. They are used to process a broad range of materials including metals, glass, plastics, and semiconductors. But this application diversity creates a concomitant need for laser diversity. Namely, while each application requires superior reliability and performance, the definition of “superior performance” is very application-specific. For example, some metal ablation applications may benefit from a long laser pulse, whereas semiconductor scribing needs a short pulse and a very high pulse repetition rate.

Posted in: Photonics, Briefs, ptb catchall, Tech Briefs, Photonics

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Aligning Optical Fibers by Means of Actuated MEMS Wedges

Wedges would be fabricated using gray-scale exposure of photoresist. Goddard Space Flight Center, Greenbelt, Maryland Microelectromechanical systems (MEMS) of a proposed type would be designed and fabricated to effect lateral and vertical alignment of optical fibers with respect to optical, electro-optical, optoelectronic, and/or photonic devices on integrated circuit chips and similar monolithic device structures. A MEMS device of this type would consist of a pair of oppositely sloped alignment wedges attached to linear actuators that would translate the wedges in the plane of a substrate, causing an optical fiber in contact with the sloping wedge surfaces to undergo various displacements parallel and perpendicular to the plane. In making it possible to accurately align optical fibers individually during the packaging stages of fabrication of the affected devices, this MEMS device would also make it possible to relax tolerances in other stages of fabrication, thereby potentially reducing costs and increasing yields.

Posted in: Photonics, Briefs, ptb catchall, Tech Briefs, Photonics

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Optical Characterization of Molecular Contaminant Films

A theoretical model is correlated with measured spectral transmittances and VUV exposures of spacecraft optics. Lyndon B. Johnson Space Center, Houston, Texas A semi-empirical method of optical characterization of thin contaminant films on surfaces of optical components has been conceived. The method was originally intended for application to films that become photochemically deposited on such optical components as science windows, lenses, prisms, thin-film radiators, and glass solar-cell covers aboard spacecraft and satellites in orbit. The method should also be applicable, with suitable modifications, to thin optical films (whether deposited deliberately or formed as contaminants) on optical components used on Earth in the computer microchip laser communications and thin-film industries.

Posted in: Photonics, Briefs, ptb catchall, Tech Briefs, Photonics

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Photonics West Exhibitor Preview

View these and other new products on display by exhibitors at Photonics West, January 23-25, in San Jose, CA. Visit Photonics Tech Briefs at Booth 435. Visit http://spie.org/Conferences/programs/07/pw/ for more information.

Posted in: Products, Products

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Card Provides PCI-Based Multi-Axis Motion Control

Performance Motion Devices (Lincoln, MA) offers the Prodigy™-PCI motion card for multi-axis motion control. Available in 1-, 2-, 3-, and 4-axis versions, the card provides trajectory generation, performance trace, on-the-fly changes, and commutation. Motor type can be software- selected on a per-axis basis, and includes DC brush, brushless DC, step, and microstepping. The card communicates via a PCI bus, CANbus, or serial port. Card features include S-curve, trapezoidal, velocity contouring, electronic gearing, and user-generated profile modes. The card accepts input parameters such as position, velocity, acceleration, and jerk from the host, and generates a corresponding trajectory.

Posted in: Products, Products

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Sensor Interface Design Demystified

With the rapid expansion of available sensor elements driven by the growth of MEMS (microelectromechanical systems) sensors, the considerations of sensor interface design become ever more important. The design engineer needs to understand both the sensor as well as the application in order to make the proper design tradeoffs in this already tricky art of analog front-end design. The challenge is further compounded with the trend toward MEMS technologies and their inherently smaller signals. This article attempts to cover some of the basics of sensor interface design and gives a cursory overview of the challenges and trade-offs of the possible approaches. It’s Not Just a Resistor Fundamentally, every sensor can be modeled as a simpler component, albeit a component with a value that changes over time. Usually this means we can treat them as either a simple passive impedance, such as a resistance, capacitance, or inductance, or as an active source, such as a current or voltage source. As these values change with time, we need to be able to convert that change into a time-varying voltage. Furthermore, we need to maintain the linearity of the sensor while we do this.

Posted in: Articles, Articles

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Advanced Ceramic Heaters Improve IC Packaging and System Performance

The continuous increase in the consumption of semiconductor devices and the emergence of new applications in optical components — MEMS, LCD display, flip-chip, chip-onglass, and multichip modules — has created a vast demand for faster throughput and better die-bonding equipment for IC packaging. IC packaging requires a typical ramp rate of 100ºC per second to 400 to 500ºC ±2°C, and a cycle time of 7 to 15 seconds. Similarly, IC chip testing, which stresses chips between -40 to 125ºC while monitoring electrical parameters, also requires a faster cycle rate. To manufacture ICs of all types, a die bonder or die attach equipment is used to attach the die to the die pad or die cavity of the package’s support structure. The two most common processes for attaching the die to the die pad or substrate are adhesive die attach and eutectic die attach. In adhesive die attach, adhesives such as epoxy, polyimide, and Ag-filled glass frit are used to attach the die. Eutectic die attach uses a eutectic alloy. Au-Si eutectic, one commonly used alloy, has a liquidous temperature of 370ºC, while another alloy, Au-Sn, has a liquidous temperature of 280ºC.

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