Low jitter Q-switched fiber laser using optically driven surface-normal saturable absorber modulator

Stable dark pulses produced by a graphite oxide saturable absorber in a fiber laser cavity

In this paper, we report for the first time, to the best of our knowledge, the experimental generation of dark pulses in the 1.5 µm band from a passively $Q$Q-switched fiber laser employing graphite oxide as the saturable absorber, generating tunable microsecond pulses with kHz repetition rates. The graphite oxide samples were obtained by recycling the graphite present in Li-ion batteries used in cell phones through a chemical separation and oxidation process. Sample characterization employing x-ray diffraction, solid-state $ ^{{13}}{\rm C} $¹³C nuclear magnetic resonance, and Raman spectroscopy showed that the produced graphite oxide exhibited a homogeneously oxidized structure. Dark pulse emission could be observed at a relatively low pump threshold of 35 mW in a short 20 m laser cavity, indicating that the graphite oxide acted as a saturable absorber, significantly enhancing the nonlinearity of the laser cavity. Additionally, dark pulse operation was demonstrated at a high stability with a signal-to-noise ratio of 56 dB and a pulse-to-pulse timing jitter of 159.84 fs.

Ytterbium-doped fiber laser as pulsed source of narrowband amplified spontaneous emission

We report random noise pulsed regime of an ytterbium-doped fiber laser arranged in common Fabry-Perot configuration. We show that the laser output obeys the photon statistics inherent to narrowband amplified spontaneous emission and that the noise pulsing is properly addressed in terms of probability density and autocorrelation functions. Our novel approach reveals, in particular, that the regime’s coherence time dramatically shortens, from few ns to tens ps, with increasing laser power.

Role of modulation frequency in a hybrid Q-switched Nd:LuVO₄ laser with an acousto-optic modulator and a Cr⁴⁺:YAG saturable absorber

This study presents a hybrid Q-switched Nd:LuVO₄ laser with an acousto-optic modulator (AOM) and a Cr⁴⁺:YAG saturable absorber. The importance of the modulation frequency of the AOM in this dual-loss modulation system is examined with two distinct observations: (1) the periodic-ramp pulse characteristics with the modulation frequency, and (2) the existence of the intrinsic modulation frequency for minimizing the pulsewidth. The shortest pulsewidth and the highest peak power were 10.6 ns and 13.9 kW, respectively, at a pump power of 10 W. Compared with the passively Q-switched laser, which has a pulsewidth of 18.3 ns, the ratio of pulse compression reaches 42%. Finally, numerical simulations based on the rate equations are used to verify the experimental results.

Investigation of terahertz generation from passively Q-switched dual-frequency laser pulses

When two Nd:YLF crystals share a Cr:YAG crystal functioning as a single passive Q switch, the timing jitter between each pair of dual-frequency pulses generated by the two crystals has been reduced by a factor of 20. Such a reduction in the timing jitter allows us to generate terahertz pulses by focusing such a passively Q-switched laser beam onto a nonlinear crystal. Such a result represents the first step for us to eventually implement a compact terahertz source based on ultracompact microchip lasers.

Hybrid Q-switched Yb-doped fiber laser

We investigate the performance of a hybrid Q-switched (HQS) fiber laser that is constructed with a low RF-power driven acousto-optic (AO) Q-switch and an AlGaInAs semiconductor saturable absorber. Compared to a pure passively Q-switched (PQS) fiber laser, the ratio of timing jitter to pulse period can be significantly reduced from 2% to 0.3% in the regime of far above threshold. On the other hand, the prelasing effect in a pure actively Q-switched fiber laser can be considerably improved. More importantly, the maximum pulse energy of the HQS fiber laser can be increased approximately 25% in comparison with the result of the PQS fiber laser. At a pump power of 24 W, the highest pulse energy is up to 0.56 mJ with the pulse duration of 50 ns at the repetition rate of 23 kHz.