Physical Sciences

Measuring Two Key Parameters of H3 Color Centers in Diamond

These parameters are needed for the further development of diamond lasers.A method of measuring two key parameters of H3 color centers in diamond has been created as part of a continuing effort to develop tunable, continuouswave, visible lasers that would utilize diamond as the lasing medium. (An H3 color center in a diamond crystal lattice comprises two nitrogen atoms substituted for two carbon atoms bonded to a third carbon atom. H3 color centers can be induced artificially; they also occur naturally. If present in sufficient density, they impart a yellow hue.) The method may also be applicable to the corresponding parameters of other candidate lasing media. One of the parameters is the number density of color centers, which is needed for designing an efficient laser. The other parameter is an optical-absorption cross section, which, as explained below, is needed for determining the number density.

Posted in: Physical Sciences, Photonics, Briefs

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Networked Equipment Makes Spherical and Aspheric Optics Manufacturing Predictable

Optical component production becomes more stable and predictable when metrology results inform the manufacturing process. In their quest for the twin grails of high production volume and extreme precision in the manufacture of both spherical and aspherical optical surfaces, manufacturers have been stymied by the difficulty of translating measurement results obtained from metrology tools to adjustments of grinding and polishing processes. In the past, this process involved manual analysis by highly skilled technical personnel — in other words, error-prone humans.

Posted in: Physical Sciences, Photonics, Briefs

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Power Meter Design Minimizes Fiber Power Measurement Inaccuracies

Integrating cavity design minimizes variability caused by fiber positioning, connector orientation, and polarization.Manufacturers of multiplexers, attenuators, amplifiers, and other fiber-optic components must characterize their products for parameters such as insertion loss and polarization-dependent loss. Insertion loss is usually accomplished by measuring output power variations before and after the component has been connected to a laser source. Polarization-dependent loss is measured by varying the input polarization to the device, and measuring the variation in power as the polarization vector is swept through all possible angles. The power meter used to perform these measurements may be sensitive to these types of variations, compromising measurement accuracy of the component under test. Most power meters, for instance, are sensitive to changes in polarization as well as uniformity of illumination of the detector surface and position of the fiber end with respect to the detector. In practice, integrating spheres are used to reduce these sensitivities.

Posted in: Physical Sciences, Photonics, Briefs

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Infrared Emitter Combines Photonic Crystal Technology With MEMS Manufacturing

Microelectromechanical system (MEMS) machining enables infrared emitters to be built directly on a silicon chip.In one of the first real-world applications of photonic crystals, two companies partnered to produce a photonic crystal enhanced (PCE) micro-hotplate device with applications in areas from military combat identification to commercial and biomedical gas sensing technology. Ion Optics, which manufactures optical-based MEMS gas detection sensors and wavelength-tuned infrared emitters, partnered with IMT, which produced the device using its MEMS prototyping and production capabilities.

Posted in: Physical Sciences, Photonics, Briefs

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GaAs QWIP Array Containing More Than a Million Pixels

GaAs offers advantages over InSb and HgCdTe. A 1,024 × 1,024-pixel array of quantumwell infrared photodetectors (QWIPs) has been built on a 1.8 × 1.8-cm GaAs chip. In tests, the array was found to perform well in detecting images at wavelengths from 8 to 9 μm in operation at temperatures between 60 and 70 K. The largest-format QWIP prior array that performed successfully in tests contained 512 × 640 pixels.

Posted in: Physical Sciences, Photonics, Briefs

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Software Analyzes Heat Buildup in VCSELs

Modeling allows redesign without diminishing reliability.Internal heating is a key issue for vertical cavity surface emitting lasers (VCSELs), a semiconductor microlaser diode that emits light in a cylindrical beam vertically from the surface of a fabricated wafer. They generally have higher thermal impedance than edgeemitting lasers and are fairly efficient for optical devices, running at roughly 25% efficiency in contrast to light emitting diodes’ (LEDs) typical 2% to 3%. For instance, they produce 10 mW of optical power from a 40-mW input; the remaining is dissipated as heat.

Posted in: Physical Sciences, Photonics, Briefs

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Wavelength Translation Using SFP Transceivers Enables Extension of Optical-Communication Links

Optical-Electrical-Optical (OEO) wavelength translation (WT) based on smallform- factor pluggable (SFP) transceivers is meeting with increased interest in metro optical-network applications. It provides a flexible and low-cost solution when it interfaces with legacy optical equipment that does not support International Telecommunications Union (ITU) wavelengths. WT improves the performance of optical systems by changing the operating wavelength of the incoming optical signal to a wavelength that enables longer reach through lower attenuation or lower dispersion penalty.

Posted in: Physical Sciences, Photonics, Briefs

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