This article presents new hyperspectral imaging (HSI) results from a standoff chemical detection system that utilizes monolithic arrays of Distributed Feedback (DFB) Quantum Cascade Lasers (QCLs) as a source, with each array element at a slightly different wavelength than its neighbor. In this rastering approach to HSI, analysis of analyte/substrate pairs benefits from a laser source with characteristics offered uniquely by a QCL Array. In addition to describing the HSI system developed, a description of experimental standoff detection results using the man-portable system from 1.4 meters are presented. We present HSI results on two very different chemical substrate pairs; trace solid PETN on aluminum and the liquid VX on polycarbonate.
ThermoFisher Scientific (formerly Ahura Scientific) has developed a handheld, modular detection and identification system for trace-level gases, chemical vapors and aerosols, and swab analyses. The sample chamber is a separate, removable module that can be tailored specifically to the users’ needs. The vapor module can operate in three modes: ambient sampling, vapor/aerosol preconcentration, and direct injection. A swab module can be used to analyze thermally desorbed vapors from a sample swab. Limits of identification for vapors are as low as 0.1 ppm following a 15-min preconcentration period. The swab module can detect as little as 5 μg of TNT.
Proc. SPIE. 3626, Testing, Packaging, Reliability, and Applications of Semiconductor Lasers IV
KEYWORDS: Multimode fibers, Metals, Spectroscopy, Composites, Reliability, Near field scanning optical microscopy, Near field, Associative arrays, Vertical cavity surface emitting lasers, Near field optics
We have studied the spatial and spectral characteristics of vertical-cavity surface-emitting laser emission using near- field scanning optical microscopy. We report the multi- transverse-mode characteristics of 15 micrometers diameter proton- implanted 850 nm devices used in a 2 Gbit/s multimode fiber- optic links. Spectrally resolved and integrated intensity scans over a 20 X 20 area were performed. The intensity of each resolvable transverse mode was integrated and its wavelength range false-colored at each scan position. The resulting composite image displays relative intensity and spatial distribution information for each transverse mode. Correlation with the shear force data allows mapping of the optical distributions to topographical features. Lasing filaments were observed at high drive currents. Gain competition among spatially overlapping transverse modes was observed while spatially isolated modes coexisted without competition.