Synthesis of Optical Pulses Using Brillouin Amplification

A technique for Fourier synthesis of optical pulses involves radio-frequency (RF) phase modulation of laser beams, Brillouin selective amplification of modulation sidebands, and, finally, generation of pulses through coherent superposition of (and thus interference among) the sidebands. (Brillouin amplification is a consequence of a nonlinear interaction of the pump and signal beams with an optical fiber via the electrostrictive effect, and has been described in several prior articles in NASA Tech Briefs.) Coherent superposition is possible because the Brillouin selective sideband amplification (BSSA) automatically locks the various sidebands together in phase. The shape and duration of the pulses can be controlled by controlling the gain for each sideband, while the pulse-repetition frequency can be controlled by controlling the frequency of the modulation. Other attractive features of this technique include built-in optical amplification, simple electronic control, insensitivity to polarization, and conversion of a low-phase noise RF signal into low-jitter optical pulses.