Moti Margalit

High-repetition-rate mode-locked Er-doped fiber lasers by harmonic injection locking

We present a novel method for the generation of synchronized short pulses at high repetition rates from Er-doped silica fiber lasers. The method employs coupling of an optical pulse train to a passively mode-locked fiber laser. The injected signal repetition rate is slightly detuned from the modal spacing of the fiber laser, such that a subset of the latter modes is injection locked, yielding a high-repetition-rate pulse train. By injecting a 2-GHz train of relatively broad optical pulses at an average power of 100 μW, we achieved a train of 6-ps pulses at rates of 40 GHz from the harmonically locked fiber laser.

Injection locking of a passively mode-locked laser

We present and analyze a model of a passively mode-locked laser, which is subjected to injection of a coherent pulse train. The model, based on soliton perturbation theory, predicts the possibility of coherent injection locking, and gives analytical estimates for the locking ranges. The ability to simultaneously lock the timing and the phase of the output pulses of a mode-locked laser to an injected, coherent pulse train is shown. The interesting limiting case of phase locking the mode-locked laser to a constant amplitude external injection, is addressed with implications for future coherent soliton communication systems.

Injection locking of an actively mode-locked semiconductor laser

We report what is to our knowledge the first observation of synchronous coherent injection locking of an actively mode-locked extended cavity semiconductor laser to an external light pulse train. In the temporal domain, we observed experimentally and verified theoretically a significant narrowing of the output pulse of the mode-locked laser. In the spectral domain, we demonstrated experimentally the narrowing of the output optical spectrum that was due to rejection of spectral components outside the spectral band of the locking pulses. Locking ranges, in the time and the frequency domains, were measured to be ~200 ps and ~5 nm, respectively.

Synchronized two-color operation of a passively mode-locked erbium-doped fiber laser by dual-injection locking

Summary form only given. The simultaneous operation of a passively mode-locked laser at two different wavelengths is important as a source for high-pulse-rate, wavelength-division multiplexing (WDM) schemes, for wideband pump probe and four-wave mixing experiments. Using the recently introduced harmonic injection-locking scheme, we achieved synchronized locking of a passively mode-locked fiber laser, at two wavelengths (1.53 /spl mu/m and 1.55 /spl mu/m) simultaneously, producing pulses of several picoseconds with 7.5-GHz pulse repetition rates. Because the same scheme can also serve as a storage ring, this work demonstrates the feasibility of a two-color memory ring.

Simulation of passively mode locked lasers, using natural boundary conditions: multi pulse evolution and ordering

We present a method for simulating a passively mode locked laser. By selecting the simulation time step as the cavity round trip time, we achieved a proper tracking of the temporal evolution of the individual cavity modes of the laser. Employing the split step Fourier algorithm using this natural modes base, an efficient simulation method was obtained, while retaining at each propagation step the direct physical relations between the calculated phase terms in the time and frequency domains to the actual optical field and individual cavity modes, respectively. Using this method, we tracked the formation of multiple pulses in a passively mode locked fiber laser cavity, and explored the effect of delayed optical feedback as a means for pulse ordering in fiber lasers.

Bistability and optical control of a distributed-Bragg-reflector laser.

We demonstrate bistable operation and optical control of a specially designed distributed-Bragg-reflector laser. Optically controlled turn-on and turn-off with 1-pJ pulses at 1.5 μm and 2-pJ pulses at 1.3 μm, respectively, is demonstrated as well as all-optical flip-flop operation.

Localization immunity and coherence of extended two-dimensional semiconductor vertical cavity-locked laser arrays

Large two-dimensional arrays of vertical cavity semiconductor lasers, unlike similar one-dimensional arrays, exhibit a single lasing mode because of their immunity to defects and inhomogeneities. Both experiments and theoretical study of the coherence of the arrays verified this improved performance and attributed it to possible bypass routes for the propagation of phase information in the two-dimensional structure, which ensured the locking of remote array elements even in the presence of defects.

Noise in pulsed injection locking of a passively modelocked laser

In this paper, noise effects related to pulsed injection locking of a passively modelocked laser (PML) are analyzed. A set of nonlinear equations, derived from a soliton perturbation method, is used to describe the modelocked laser pulse evolution, under injection locking. The equations are linearized, and the stability of the injection locked solution is studied. Subsequently, the linear equations are employed to describe the coupling of both the injected signal noise and the internal noise, to the locked pulses. Noise reduction due to the injection process is demonstrated, with important implications for all optical signal regeneration and synchronization.

Multimode effects on the evolution and long-term stability of a passively mode-locked laser under pulsed injection locking

A multidimensional extension of the injection locking of CW lasers has been recently presented and experimentally verified when both a passively and an actively mode-locked laser were locked to injected coherent pulse trains. Harmonic injection locking of a passively mode-locked laser, where a subset of the laser cavity modes were locked to the injected signal, was also recently realized in a fiber laser to yield trains of 6-ps pulses at rates of up to 40 GHz. In this paper, the multimode injection-locking process is addressed with an emphasis on the long-term dynamics of the laser, pulse buildup under injection locking, memory effects, noise mechanism as well as potential applications, e.g., optical signal regeneration. Using a recently introduced formalism for describing passively mode-locked lasers, the experimental results are compared to numerical simulations.

Multimode injection locking buildup and dephasing in passively mode locked fiber lasers

Abstract The recently introduced harmonic injection locking is a method for generating pulse trains at high repetition rates from passively mode locked lasers. The buildup and dephasing mechanism which are instrumental for the fundamental understanding of the multimode locking process as well as its possible applications, were explored experimentally and by a novel model simulation which was adapted to include the pulsed injection locking. The measured locked pulse buildup time wa.5 μs, which corresponds to several tens of cavity roundtrips. When the injection was interrupted, the laser continued to emit synchronized pulses, indicating a persistence of the injection induced phase relationship of the cavity modes.