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16 May 2007 MIT/LL development of broadband linear frequency chirp for high resolution ladar
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The development of a high-resolution laser radar (ladar) exhibiting sub-mm resolution would have a great impact on standoff identification applications. It would provide biometric identification capabilities such as three-dimensional facial recognition, interrogation of skin pore patterns and skin texture, and iris recognition. The most significant technical challenge to developing such a ladar is to produce the appropriate optical waveform with high fideltiy. One implementation of such a system requires a 1.5-THz linear frequency sweep in 75 &mgr;s. Previous demonstrations of imaging with such waveforms achieved a 1 THz sweep in > 100 ms, and required additional corrections to compensate for sweep nonlinearity. The generation of high fidelity, temporally short frequency-swept waveforms is of considerable interest to the DoD community. We are developing a technique that utilizes a novel method to generate a 1 THz sweep in 50 &mgr;s from a mode-locked laser. As a proof-of-principle demonstration of this technique we have successfully generated a 20 GHz sweep in 1 µs with a fidelity sufficient to produce better than -20 dB sidelobes for a range measurement without using any additional corrections. This method is scalable to produce the entire 1 THz sweep in 50 &mgr;s.
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Kevin W. Holman, David G. Kocher, and Sumanth Kaushik "MIT/LL development of broadband linear frequency chirp for high resolution ladar", Proc. SPIE 6572, Enabling Photonics Technologies for Defense, Security, and Aerospace Applications III, 65720J (16 May 2007);

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