21 August 2003 Broadly tunable master/local oscillator lasers for advanced laser radar applications
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A number of scientific, defense, and civilian/commercial applications of coherent laser radar require correction and/or deliberate generation of very large offset frequencies between the local oscillator (LO) reference frequency and the pulsed transmitter laser frequency. An example of this system requirement is the need for agile, stable, multi-GHz offset control between master and local oscillator (MO/LO) sources in space-based lidar applications, where platform motion must be compensated for in order to perform efficient heterodyne detection of much smaller Doppler shifts due to atmospheric winds, and to lower system signal processing bandwidth demands. Another example is generation of few-GHz MO/LO offsets to accurately resolve atmospheric absorption spectra and measure gas species concentration in coherent differential absorption lidar (DIAL) applications. In this paper, we describe the development of two generations of eyesafe, diode-pumped MO/LO laser technology and actively phase-locked control electronics, specific to the space-based Doppler platform compensation problem. The lasers are based on CTI's METEOR single frequency laser technology, using Tm,Ho:YLF (2.05 μm wavelength). Fast, programmable offset-locking of the two single-frequency lasers to as much as ± 10.0 GHz was consistently demonstrated using a custom-fabricated wideband (~ 4 GHz @ 3 dB down) 2 μm-sensitive heterodyne photoreceiver as the servo detection element. Offset-frequency step settling time, control accuracy, and the phase-sensitive servo system will be described in detail. Application of the technique and technology in atmospheric CO2 DIAL measurement applications currently under way at CTI will also be discussed.
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Charley P. Hale, Charley P. Hale, John W. Hobbs, John W. Hobbs, Philip Gatt, Philip Gatt, "Broadly tunable master/local oscillator lasers for advanced laser radar applications", Proc. SPIE 5086, Laser Radar Technology and Applications VIII, (21 August 2003); doi: 10.1117/12.488097; https://doi.org/10.1117/12.488097

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