Abstract
A novel, programmable, mode-locked fiber laser design is presented and numerically demonstrated. The laser programmability is enabled by an intracavity optical phase-only pulse shaper, which utilizes the same linearly chirped fiber Bragg grating (LC-FBG) from its two opposite ends to perform real-time optical Fourier transformation. A binary bit-pattern generator (BPG) operating at 20-Gb/s and producing a periodic sequence of 32 bits every 1.6 ns, is subsequently used to drive an optical phase modulator inside the laser cavity. Simulation results indicate stable programmable intensity profiles for each optimized user defined 32 code words. The laser operated in the self-similar mode-locking regime, enabling wave-breaking free operation. The programmable 32 bit code word targeting a specific intensity profile was determined using 100 generations of the genetic algorithm. The control of ultrashort pulse intensity profiles on the picosecond and femtosecond time scales is difficult. The process of stretching and compressing the pulse in the time domain allows for a slower BPG to impose a predefined phase modulation prior to pulse compression. This results in control over the fine features of the intensity profile of the compressed pulse on a picosecond or femtosecond time scale inside the laser cavity. The stability of the proposed scheme depends on the consistency and accuracy of the BPG rise and fall times in practice.
Highlights
The development of lasers and their reliable generation of ultrashort optical pulses on the picosecond and femtosecond time scale, have found a multitude of applications ranging from astronomy [1], to elemental mass spectrometry [2] and to telecommunications [3]
The following sections of this paper explore the theoretical possibility of applying the time-domain pulse shaping set-up in Figure 1 for an interacavity programmable actively mode-locked fiber laser
A user defined 32 bit binary code word can program the laser to produce a variety of intensity profiles operating at the self-similar mode-locking regime, enabling wave-breaking free operation
Summary
The development of lasers and their reliable generation of ultrashort optical pulses on the picosecond and femtosecond time scale, have found a multitude of applications ranging from astronomy [1], to elemental mass spectrometry [2] and to telecommunications [3]. Numerical modeling of passively mode-locked fiber lasers showed the generation of super Gaussian intensity profiles by changing the intensity discriminating mechanism inside the laser cavity from a saturable absorber (SA) to a long period fiber grating (LPFG) [4]. In [5], a programmable, mode-locked fiber laser was demonstrated through introducing a digital micromirror device (DMD)-based arbitrary spectrum amplitude shaper inside. A mode-locked fiber laser with an e-controlled cavity operating in the ultra wide range was demonstrated [7]. The primary objective of this paper is to introduce and numerically demonstrate a novel design for a digitally programmable, mode-locked fiber laser, which utilizes time-domain phase-only pulse shaping inside the laser cavity
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