Optically Driven Deformable Mirrors

There is no wiring on the back sides of these mirrors.

Optically driven deformable mirrors may eventually supplant electrically driven deformable mirrors in some adaptive-optics and active-optics applications. Traditionally, the mirror facets in electrically driven deformable mirrors are actuated, variously, by means of piezoelectric, electrostrictive, microelectromechanical, liquid-crystal, or thermal devices. At least one such device must be dedicated to each facet, and there must be at least one wire carrying a control or drive signal to the device. If a deformable mirror comprises many (e.g., thousands) of facets, then wiring becomes a major problem for design, and the problem is compounded in cases of piezoelectric or other actuators for which high drive voltages are required. In contrast, in optically driven mirrors, the wiring problem is eliminated.

Posted in: Briefs, TSP, ptb catchall, Tech Briefs, Photonics, Mirrors, Wiring, Wiring

Automatic Alignment of Displacement-Measuring Interferometer

Corrections are derived from fluctuations associated with circular dithering of a laser beam.

A control system strives to maintain the correct alignment of a laser beam in an interferometer dedicated to measuring the displacement or distance between two fiducial corner-cube reflectors. The correct alignment of the laser beam is parallel to the line between the corner points of the corner-cube reflectors: Any deviation from parallelism changes the length of the optical path between the reflectors, thereby introducing a displacement or distance measurement error.

Posted in: Briefs, TSP, ptb catchall, Tech Briefs, Photonics, Measurements, Electronic control systems, Lasers, Electronic control systems, Lasers, Test equipment and instrumentation

Even Illumination From Fiber-Optic-Coupled Laser Diodes

Emerging light beams would be shaped by diffractive fiber-optic tips.

A method of equipping fiber-optic-coupled laser diodes to evenly illuminate specified fields of view has been proposed. The essence of the method is to shape the tips of the optical fibers into suitably designed diffractive optical elements. One of the main benefits afforded by the method would be more nearly complete utilization of the available light.

Posted in: Briefs, TSP, ptb catchall, Tech Briefs, Photonics, Exterior lighting, Fiber optics, Lasers, Fiber optics, Lasers

Excimer Leverages Litho Lessons for kHz Micromachining

Features developed for lithography light sources are creating a mid-tier excimer laser niche.

Coherent, Santa Clara, California

Ultraviolet lasers currently are used in a very diverse range of industries and applications. This is because their high-energy photons directly can break inter-atomic bonds in many materials, and the short wavelength enables a high degree of spatial resolution (see Figure 1). Amongst ultraviolet lasers, excimers are unique in their ability to deliver a combination of high pulse energy and high average power. Because of these advantages, excimers are used in applications as diverse as ophthalmic corrective procedures, low-temperature silicon annealing for flat-panel displays, drilling inkjet nozzles, and treating the cylinder liners of diesel engines for greener automobile performance.

Posted in: Briefs, ptb catchall, Tech Briefs, Photonics, Lasers, Lasers, Manufacturing equipment and machinery, Reliability, Reliability

QC Lasers Improve Hazardous Gas Monitoring

The measurement of gases associated with industrial processing/emissions monitoring has become increasingly important as the need to improve efficiencies in process control has increased, and legislation governing emissions has come into force. Gases including NOx, SOx, CO2, CO, NH3, and H2O commonly are used to assess processes such as combustion and quenching, while many fall under emissions legislation resulting from the Kyoto agreement.

Posted in: Articles, Features, ptb catchall, Motion Control, Photonics, Lasers, Lasers, Emissions measurement, Gases

LUTs: Take Control of Your Imaging Application

It is hard to see how machine-vision camera manufacturers produce decent-quality products at reasonable prices. The multi-megapixel sensors at the heart of current machine-vision cameras are among the largest of VLSI (very-large-scale integration) semiconductor chips, and it is almost impossible to make them with the pixel-to-pixel uniformity required for high-precision imaging applications. Without some way of compensating for manufacturing variations across a given image sensor, many otherwise acceptable chips would have to be discarded. That would drastically reduce manufacturing yields and drive sensor-chip prices far beyond levels acceptable for many applications.

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

Water Jets and Lasers Cut Through Electronic Industry’s Problems

Semiconductor manufacturers need the flexibility of a wafer-cutting machine that supports various wafer sizes and cuts them without the mechanical and thermal damage often seen with traditional cutting methods, including the mechanical stress that occurs with conventional sawing, or the contamination and/or ablated material caused by laser cutting. Employing a dicing process that makes the wafers less prone to breakage would allow manufacturers to introduce thinner wafers into the production line, thereby increasing the number of functions on a given device. A machine that cuts lasers without a heat-affected zone would also offer efficiency advantages to manufacturers.

Posted in: Application Briefs, Applications, ptb catchall, Photonics, Lasers, Lasers, Water, Cutting, Semiconductors

Full-Duplex Digital Communication on a Single Laser Beam

The laser beam would be transmitted with one modulation and retroreflected with another modulation.

A proposed free-space optical communication system would operate in a full-duplex mode, using a single constant-power laser beam for transmission and reception of binary signals at both ends of the free-space optical path. The system was conceived for two-way data communication between a ground station and a spacecraft in a low orbit around the Earth. It has been estimated that in this application, a data rate of 10 kb/s could be achieved at a ground-station-to-spacecraft distance of 320 km, using a laser power of only 100 mW. The basic system concept is also applicable to terrestrial free-space optical communications.

Posted in: Briefs, ptb catchall, Tech Briefs, Photonics, Data acquisition and handling, Lasers, Optics, Data acquisition and handling, Lasers, Optics

Stabilizing Microwave Frequency of a Photonic Oscillator

Microwave frequency is stabilized by stabilizing optical frequency to an atomic transition.

A scheme for stabilizing the frequency of a microwave signal is proposed that exploits the operational characteristics of a coupled optoelectronic oscillator (COEO) and related optoelectronic equipment. An essential element in the scheme is a fiber mode-locked laser (MLL), the optical frequency of which is locked to an atomic transition. In this scheme, the optical frequency stability of the mode-locked laser is transferred to that of the microwave in the same device. Relative to prior schemes for using wideband optical frequency comb to stabilize microwave signals, this scheme is simpler and lends itself more readily to implementation in relatively compact, rugged equipment. The anticipated development of small, low-power, lightweight, highly stable microwave oscillators based on this scheme would afford great benefits in communication, navigation, metrology, and fundamental sciences.

Posted in: Briefs, TSP, ptb catchall, Tech Briefs, Photonics, Electronic equipment, Lasers, Optics, Electronic equipment, Lasers, Optics

Microwave Oscillators Based on Nonlinear WGM Resonators

Optical signals are phase-modulated with spectrally pure microwave signals.

Optical oscillators that exploit resonantly enhanced four-wave mixing in nonlinear whispering-gallery-mode (WGM) resonators are under investigation for potential utility as low-power, ultra-miniature sources of stable, spectrally pure microwave signals. There are numerous potential uses for such oscillators in radar systems, communication systems, and scientific instrumentation.

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

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