Electronic Military & Defense Annual Resource

4th Edition

Electronic Military & Defense magazine was developed for engineers, program managers, project managers, and those involved in the design and development of electronic and electro-optic systems for military, defense, and aerospace applications.

Issue link: https://electronicsmilitarydefense.epubxp.com/i/350588

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Page 16 of 59

which the sample is exposed, enabling the measurement of sensitive and combustible samples without the risk of ignition. This combination of SERS and ROS sampling enables the development of a new generation of sensitive handheld units for the detection of explosives and other hazards in the battlefield setting. Additional advances in Raman have resulted from the use of different lasers with unique properties and advantages depending on their wavelength. The choice of laser wavelength must be made carefully because the intensity of Raman scattering decreases at the fourth power of the laser wavelength. The tradeoff in Raman scattering intensity and sample fluorescence must be considered when selecting the best excitation wavelength for a particular Raman measurement. Shorter laser wavelengths increase the intensity of Raman scattering but usually result in a higher fluorescence background from the sample. Alternatively, longer laser wavelengths usually result in lower background fluorescence but result in decreased Raman scattering intensity. Knowledge of the characteristics of laser wavelengths used for Raman measurements enables researchers to leverage the choice of excitation wavelength to optimize their results for a given sample. NIR (near infrared) laser excitation using a 1064 nm laser is often used for Raman measurements of compounds that fluoresce. The suspicious white powders that raise security alerts are notorious for high fluorescence at lower Raman excitation wavelengths so they are often measured with a 1064 nm laser. While fluorescence is lower with 1064 nm Raman, there are a few limitations to consider — including the reduction in Raman-scattering intensity at the longer laser wavelength, the need for a thermoelectric cooler (TEC) to reduce noise in the indium gallium arsenide (InGaAs) detectors used for NIR wavelengths, and additional eye safety concerns to protect soldiers from the 1064 nm laser, which is not visible to the naked eye. Work to mitigate the sensitivity, power, and noise limitations is already under way with the development of more sensitive detectors along with improvements in batteries and the power management of field devices. At the opposite end of the spectrum, ultraviolet (UV) P r e c i s i o n E n g i n e e r i n g I s C o r e Novotech is a global supplier of infrared Optics and Assemblies. Infrared Germanium is another core to Novotech and weÕre stocked in substantial inventories from ingots to optics to assemblies. Other materials include: Silicon, ZnSe, and ZnS. Crystal growth, fabrication and coating capabilities allow us to offer a FRPSUHKHQVLYHDQGÁH[LEOHUDQJHRILQIUDUHG materials solutions and quick deliveries. ph: 978.929.9458 e: optics@novotech.net www.novotech.net 17 Technology Electronic Military & Defense Annual Resource, 4th Edition

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