Nonlinear Mirror Mode-locked Laser Research Articles

Short- and long-range temporal cavity soliton interaction in delay models of mode-locked lasers.

Interaction equationsgoverning slow time evolution of the coordinates and phases of two interacting temporal cavity solitons in a delay differential equationmodel of a nonlinear mirror mode-locked laser are derived and analyzed. It is shown that long-range soliton interaction due to gain depletion and recovery can lead either to a development of a harmonic mode-locking regime or to a formation of closely packed incoherent soliton bound state with weakly oscillating intersoliton time separation. Short-range soliton interaction via electric field tails can result in an antiphase or in-phase stationary and breathing harmonic mode-locking regimes.

Picosecond Optical Pulse Generation by Nonlinear Mirror Mode-Locking: A Review

Background/Objectives: This article provides comprehensive review on nonlinear mirror mode-locked laser which is compact, efficient, simplest and stable source of picosecond optical pulse and is of immense research interest. Methods/ Analysis: Starting with the basics of nonlinear mirror mode-locking technique, a chronological development of the subject is presented. Issues with the efficiency and stability of the nonlinear mode-locking are addressed in both theoretical and experimental perspective. Different schemes of nonlinear mirror mode-locking, reported till date, are illustrated and compared in reference to the obtained pulse durations, power scaling, self starting and self sustained efficient modelocking. Findings: Nonlinear mirror, comprising a second harmonic generating crystal and a dichroic output coupler, can mode-lock a laser due to its behaviour analogous to fast saturable absorber. Efficiency of the laser is increased with the diode pumping; however nonlinear mirror is observed prone to passive Q-switching instability. Simultaneously Q-switched and mode-locked operation gives a simple way of increasing the peak power but is of no use because of rapid fluctuations of pulse amplitude and repetition rate. Incorporation of an accousto-optic Q-switch in the laser cavity helps run the laser in actively Q-switched and passively mode-locked regime which provides enormous stability of the Q-switched and modelocked pulse envelops and the enhanced peak power becomes useful. Pure contentious wave mode-locking is obtained by incorporation of additional intensity dependent loss mechanism by way of introducing third harmonic generation in the laser cavity and it gives an inverse saturable nonlinear loss modulation. Inverse saturable nonlinear mirror produces efficient, self sustained and stable contentious wave mode-locked picosecond optical pulse train. Application /Improvement: Nonlinear mirror mode-locked lasers have wide application in micromachining, optical frequency conversion, pumping optical parametric oscillators etc. Propositions are made for getting improved nonlinear mirror mode-locking to get bandwidth limited pulse width.

Realization of inverse saturable absorption by intracavity third-harmonic generation for efficient nonlinear mirror mode-locking

A technique of suppressing passive Q-switching by inverse saturable absorption in a cw nonlinear mirror mode-locked laser is presented. The nonlinear mirror saturable absorber consists of a second-harmonic generation crystal and a dichroic mirror while the inverse saturable loss is realized by intracavity third-harmonic generation. The inverse saturation reduces significantly the critical intracavity pulse energy for stable, self-starting, self-sustained, and power scalable cw mode-locking. Two LiB3O5 crystals are employed to realize the technique in a diode array pumped Nd:YVO4 oscillator providing a peak power of 918W, pulse width of 29ps, and repetition rate of 170MHz.

Stability regime study of a nonlinear mirror mode-locked laser

A diode array pumped nonlinear mirror mode-locked (ML) laser is developed and the regime of the stable operation for such a system is found to occur for a little detuning of intra-cavity second harmonic phase-matching. The existing theory of mode-locking using a fast saturable absorber (FSA) is used to derive corresponding equivalent parameters for a fast nonlinear mirror saturable absorber. The condition for stable single pulse ML operation is evaluated in terms of small signal gain of the laser medium and small signal nonlinear loss. The analysis explains the experimental observations and differentiates the regime of operation in ML, Q-switching and cw mode-locking.