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3 September 2008 Ultra-fast bandgap photonics: sensing and counter-sensing capabilities
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Ultra-fast laser has been used in laser sensing and laser communication systems as well as for raison d'etre of Target-to-Noise Ratio (TNR or SNR) remote control. Foundation of these quite different applications is in unique ability of ultrafast laser to change photonic characteristics when ultra-short laser pulse interacts with photonic semiconductor. Ultrafast laser is capable to sweep potential free carriers for period of time that is comparable with free carrier's life time and thereto, ultra-short pulse is able to "bleach" photonic bandgap semiconductor making it temporally insensitive to its genuine in-band irradiance. Energy transfer into semiconductor lattice follows the "bleaching". Energy transfer may have different physical mechanisms-direct thermal as well as non-thermal or electronic transfer, leading initially to temporal lattice structure changes, and, with respect to pulse intensity, eventually to band gap collapse and even phase changes in the semiconductor. However, for the purpose of fine sensing the only mild lattice disturbance is important. That will limit focus of our consideration of laser-semiconductor interaction by relatively low intensity ultra-fast and fast laser pulses. Ultra-fast and fast lasers open almost unlimited opportunities in band gap photonic applications by allowing remotely engineer the characteristics of active and passive systems such as bandwidth, spectral responsivity, detectivity, response time etc. In this paper we will discuss applications of ultra-fast lasers-lasers with femto-seconds pulse width and, to some extend-fast lasers-with picoseconds pulse width, to remote engineering of photonic characteristics of active and passive IR and electro-optical systems.
© (2008) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Michael K. Rafailov "Ultra-fast bandgap photonics: sensing and counter-sensing capabilities", Proc. SPIE 7055, Infrared Systems and Photoelectronic Technology III, 70550J (3 September 2008);


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