Dynamics of optical backward-injection-induced gain-depletion modulation and mode locking in semiconductor optical amplifier fiber lasers

Abstract

The optical gain-depletion-induced mode-locking dynamics of a semiconductor optical-amplifier-based fiber ring laser (SOAFL) backward injected by a purely sinusoidally modulated or digitally encoded distributedfeedback laser diode are theoretically and experimentally demonstrated. The effect of gain depletion and waveform on the mode-locked pulse width, pulse shape, and power of the SOAFL are interpreted from theoretical simulations. The shortest pulse width of 12 ps can be generated from an optically sinusoidal-wave-modulated SOAFL. By backward injecting the SOAFL with a digitally encoded optical signal of adjustable duty cycle, one can observe the optimized gain depletion time of 400-600 ps required for mode locking the SOAFL.

Tunable 19×10GHz L-band FP-SOA based multi-wavelength mode-locked fiber laser

“…In general, a wider injecting pulse signal is able to result in a narrower mode-locked pulse train generation [11]. To investigate external injection optical power influence on mode-locking behaviour, we gradually increased the external injection optical power.…”

“…Because the gain of the SOA is depleted by an injecting external optical signal, the SOA acts as the loss modulator [11][12][13]. The FP-SOA is incorporated into a fiber ring cavity to serve as a tunable comb filter.…”

Numerical study of a harmonic mode-locked semiconductor optical amplifier fiber ring laser

“…In this paper, a traveling-wave rate-equation model [9,10] is adopted to simulate the mode-locked pulse shape and the counterclockwise parts of the travelingwave equations are neglected because of the existence of the Faraday optical isolators. In general, when the pulse train passes through a SOA, the carrier density in the cavity will vary with both time and space.…”

“…SOA acted as the gain medium compared with erbium-doped fiber amplifier (EDFA) can suppress pulse-amplitude fluctuation and supermode noise [5,6], and an all-optical modulation SOA can also act as a mode locker [7,8]. So, a novel model of backward-optical-injection harmonic mode-locked fiber ring laser consisting of two SOAs has been proposed and preliminary experimental and theoretical results have been reported [9,10]. In this experimentation, the first SOA (called as the modulation SOA), which is DC biased slightly above threshold is backward injected by the sinusoidal-wave-modulated distributed-feedback laser diode (DFBLD), functions as an optically controlled loss modulator, whereas the second SOA (called as the gain SOA), which is DC biased on the high current, is employed to offer constant gain without any modulation.…”

SOA-based actively mode-locked fiber ring laser by forward injecting an external pulse train

“…This is because the mode-locked fiber lasers have such features as a capability of generating high-quality optical pulses with picosecond or subpicosecond duration, a wide wavelength tuning span over several tens of nanometers, and a potential to be integrated in a monolithic optical circuit. Several mode-locked fiber lasers have been demonstrated with different active media acting as a mode-locking element, such as electro-absorption modulators (EAMs) [10], lithium niobate modulators [11] and semiconductor optical amplifiers (SOAs) [12][13][14][15][16][17][18][19][20], or combining two of them [21,22]. When EAMs and lithium niobate modulators are used as a mode-locker, they are polarization sensitive and cumbersome polarization controlling is needed in the laser cavity to realize the loss modulation.…”