Generation of arbitrary frequency chirps with a fiber-based phase modulator and self-injection-locked diode laser

Abstract

We present a technique for producing pulses of laser light whose frequency is arbitrarily chirped. The output from a diode laser is sent through a fiber-optical delay line containing a fiber-based electro-optical phase modulator. Upon emerging from the fiber, the phase-modulated pulse is used to injection-lock the laser, and the process is repeated. Large phase modulations are realized by multiple passes through the loop, while the high optical power is maintained by self-injection locking after each pass. Arbitrary chirps are produced by driving the modulator with an arbitrary waveform generator. We obtain improved performance, in both chirp rate and chirp range, relative to a diode laser that is injection-locked to a modulated source.