Large polarization rotation via atomic coherence

We report significant enhancement of the nonlinear Faraday rotation in optically thick Rb vapor. Polarization rotation angles as large as 10 rad were observed for what is believed to be the first time for sub-Gauss magnetic fields. The use of this effect for high-precision magnetometry is also discussed.     

Au-197 Mössbauer spectra of some gold-boron cluster compounds

The first¹⁹⁷Au Mössbauer spectra for compounds in which gold is bound to boron clusters are reported, and their relation to the structure and bonding involved are discussed.

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Au-197 Mössbauer spectra of some gold-boron cluster compounds

     

Reliability of AuGe/Pt and AuGe/Ni ohmic contacts on GaAs

The reliability of AuGe/Pt and AuGe/Ni ohmic contacts with and without overlay metal (Ti/Au, Ti/Pt/Au or TiW/Au) has been studied. AuGe/Ni contacts have proved superior and more reliable than AuGe/Pt contacts with or without overlay. AuGe/Pt contacts are stable without overlay but degrade rapidly with overlay. AuGe/Ni contacts exhibit thermal stability after 1000 hours' aging at 250°C.     

NIST reference materials to support accuracy in drug testing

Substance abuse is a major problem worldwide. There is considerable emphasis placed upon testing individuals for evidence of use of controlled substances. Because the consequences of a positive test can be quite severe, laboratories conducting such tests must rigorously follow a carefully designed quality assurance program. Such a QA program should include use of reference materials to assure that the methods used to detect and quantify drugs are providing accurate results. The National Institute of Standards and Technology (NIST) supports accuracy in drugs of abuse testing by providing Standard Reference Materials (SRMs) with certified concentrations of drugs of abuse in urine- and hair-based reference materials. NIST, working in collaboration with the College of American Pathologists (CAP), has developed urine-based SRMs for marijuana metabolite, cocaine metabolite, morphine and codeine, and morphine glucuronide and CAP Reference Materials for amphetamines and phencyclidine. Certification measurements performed at NIST involve two independent methods for each analyte, one of which always uses GC/MS with the other usually being an LC method with either MS or UV detection. Work has recently been completed on a seven component drug in urine SRM. In addition NIST conducts research in the analysis of hair for drugs of abuse. To assist laboratories testing hair for that purpose, NIST has developed two drugs in hair reference materials.College of American Pathologists Research Associate at NIST     

Reflectance as an indirect measurement of the extent oflaser-induced coagulation

Two-dimensional reflectance images and surface thermal distributions were recorded during argon laser induced coagulation. During laser irradiation, coagulated egg yolk formed a white lesion. The whiteness, or reflectance caused by backscattering of light from the forming lesion, would be measured after a short delay from the onset of laser irradiation. In the experiments which covered exposure time from 4.5 to 17.0 s, we found that it started slowly, the reflectance increased rapidly once the surface temperature of the lesion reached approximately 90 degrees C. After this rapid rise, the reflectance began to taper off until no change in reflectance was recorded. There was a 0.98 correlation between lesion diameter measured from a two dimensional reflectance image and the lesion diameter that was measured microscopically. There was a 0.92 correlation between reflectance at the center of the lesion and microscopically measured depth of coagulation at the same point. However, the correlation between microscopically measured coagulation depth and width was only 0.88.     

High-power diffraction-limited monolithic broad area masteroscillator power amplifier

High-power monolithically integrated broad-area master oscillator power amplifiers (MBA-MOPAs), consisting of a distributed-Bragg-reflector (DBR) laser, a preamplifier, a coherent beam expander, and a broad area power amplifier producing up to 800 mW in a single spectral and spatial mode, are fabricated. The MBA-MOPA operates in an edge-emitting configuration with a primarily single-lobe output having a transverse beam divergence of 0.45°, indicating a uniform phase over the 130-μm emitting aperture     

Frequency-doubled monolithic master oscillator power amplifierlaser diode

Single-pass frequency doubling of laser diodes extends the wavelength range of infrared laser diodes to blue-green wavelengths. We describe the first experiments of frequency doubling of a coherent, high-power, monolithic master oscillator power amplifier (M-MOPA) laser diode. The output from a l-W M-MOPA is frequency doubled in a single pass through an 8.2-mm-long KNbO₃ crystal. We obtained 3.7-mW diffraction-limited output power at a wavelength of 491 nm and modulation at 20 MHz was demonstrated     

1 W CW single frequency, diffraction-limited unstable resonatorsemiconductor laser with distributed Bragg reflector mirrors

A high power tapered unstable resonator oscillator has been fabricated with distributed Bragg reflectors which operates in a single spectral mode at 941.0 nm to an output power of 1 W CW with a diffraction-limited far field pattern