Fast, broadband, rugged spectrometer for near-infrared measurements of organic solutions and multicomponent mixtures.

The mode of operation and theoretical concept behind a type of near-infrared spectrometer is discussed, which is used to measure concentrations of glucose, ethanol, CaCl2, and KCl solutions in water, respectively. The main features of the instrument are its potential for short time-to-measurement resolution on the order of tens of milliseconds, its broad spectral bandwidth from 1.0 to 2.

Measurements of NH(3) and CO(2) with Distributed-Feedback Diode Lasers Near 2.0 mum in Bioreactor Vent Gases.

Measurements of NH(3) and CO(2) were made in bioreactor vent gases with distributed-feedback diode-laser sensors operating near 2 mum. Calculated spectra of NH(3) and CO(2) were used to determine the optimum transitions for interrogating with an absorption sensor. For ammonia, a strong and isolated absorption transition at 5016.

Ammonia Detection by use of Near-Infrared Diode-Laser-Based Overtone Spectroscopy.

We describe a portable diode-laser-based sensor for NH(3) detection using vibrational overtone absorption spectroscopy at 1.53 mum. Use of fiber-coupled optical elements makes such a trace gas sensor rugged and easy to align.

Noise figure and photon statistics in coherent anti-Stokes Raman scattering.

Coherent anti-Stokes Raman scattering (CARS) is a well-known Raman scattering process that occurs when Stokes, anti-Stokes and pump waves are properly phase-matched. Using a quantum-field approach with Langevin noise sources, we calculate the noise figure for wavelength conversion between the Stokes and anti-Stokes waves in CARS and show its dependence on phase mismatch. Under phase matched conditions, the minimum noise figure is approximately 3 dB, with a correction that depends on the pump frequency, Stokes shift, refractive indices, and nonlinear susceptibilities.

Raman amplification and lasing in SiGe waveguides.

We describe the first observation of spontaneous Raman emission, stimulated amplification, and lasing in a SiGe waveguide. A pulsed optical gain of 16dB and a lasing threshold of 25 W peak pulse power (20 mW average) is observed for a Si1-xGex waveguide with x=7.5%.