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Green pulsed lidar-radar emitter based on a multipass frequency-shifting external cavity

Abstract : This paper investigates the radio frequency (RF) up-conversion properties of a frequency-shifting external cavity on a laser beam. We consider an infrared passively Q-switched pulsed laser whose intensity modulation results from the multiple round-trips in the external cavity, which contains a frequency shifter. The output beam undergoes optical second-harmonic generation necessary to reach the green wavelength. We model the pulse train using a rate-equation model to simulate the laser pulses, together with a time-delayed interference calculation taking both the diffraction efficiency and the Gaussian beam propagation into account. The predictions are verified experimentally using a diode-pumped Nd:YAG laser passively Q-switched by Cr4+:YAG whose pulse train makes multiple round-trips in a mode-matched external cavity containing an acousto-optic frequency shifter driven at 85 MHz. Second-harmonic generation is realized in a KTP crystal, yielding RF-modulated pulses at 532 nm with a modulation contrast of almost 100%. RF harmonics up to the 6th order (1.020 GHz) are observed in the green output pulses. Such a RF-modulated green laser may find applications in underwater detection and ranging. (C) 2016 Optical Society of America
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Contributor : Laurent Jonchère <>
Submitted on : Friday, July 8, 2016 - 1:28:54 PM
Last modification on : Tuesday, January 12, 2021 - 4:44:14 PM



Haiyang Zhang, Marc Brunel, Marco Romanelli, Marc Vallet. Green pulsed lidar-radar emitter based on a multipass frequency-shifting external cavity. Applied optics, Optical Society of America, 2016, 55 (10), pp.2467--2473. ⟨10.1364/AO.55.002467⟩. ⟨hal-01343399⟩



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