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Highlights: • Sub-cavity round-trip time pulses in all fiber YDF laser with AOM were generated. • Generation of pulses were studied in four experimental setups. • Pulses appear to generate after the ON time of AOM. • Pulses of 50–55 ns were achieved in cavity with round-trip time of ∼130 ns. • Pulses with 55 ns duration were amplified ∼19 W average power in two stages. Abstract Generation of stable sub-cavity round-trip time pulses have been achieved in all-fiber Ytterbium-doped Q-switched fiber laser by controlling the modulation window ON-time of acousto-optic modulator (AOM). Short pulses (anomalous pulses) of duration in the range of 50–55 ns have been achieved in experimental configurations with the cavity round-trip time of ∼130 ns, when modulation window “ON-time” of AOM was equal to or shorter than the pulse build-up time of the normal Q-switched pulses. In the case of normal AO Q-switching, pulses of duration more than 1.3 µs with an average power of 30 mW and pulse energy of 0.38 µJ at 80 kHz of repetition rate were obtained at 2 W of pump power. At the same value of the pump power, the anomalous pulses of ∼55 ns with an average power of 12 mW were generated, which are ∼24 times shorter than pulses obtained with conventional Q-switching process (normal pulses). The peak power of the anomalous pulses are higher than the normal pulses by the factor of eight at the same value of the pump power. The anomalous pulses from the AO Q-switched oscillator with 55 ns pulse duration have been amplified in single mode Ytterbium doped all fiber amplifier in two stages. Amplified average output power of ∼19 W was achieved with the output pulse energy and peak power of 240 µJ and 4.4 kW respectively in all fiber configuration. [ABSTRACT FROM AUTHOR]

Abstract: We report the performance study of a 2% atomic doped ceramic Nd:YAG rod for long pulse laser operation in the millisecond regime with pulse duration in the range of 0.5–20ms. A maximum average output power of 520W with 180J maximum pulse energy has been achieved with a slope efficiency of 5.4% using a dual rod configuration, which is the highest for typical lamp pumped ceramic Nd:YAG lasers. The laser output characteristics of the ceramic Nd:YAG rod were revealed to be nearly equivalent or superior to those of high-quality single crystal Nd:YAG rod. The laser pump chamber and resonator were designed and optimized to achieve a high efficiency and good beam quality with a beam parameter product of 16mmmrad (M 2∼47). The laser output beam was efficiently coupled through a 400μm core diameter optical fiber with 90% overall transmission efficiency. This ceramic Nd:YAG laser will be useful for various material processing applications in industry. [Copyright &y& Elsevier]

Abstract: In this paper, we present the experimental and analytical study of self-pulsing dynamics in Yb-doped photonic crystal fiber laser in single-end and double-end pumping configurations. It has been found that the intensity of self-pulses is considerably higher in the single-end pumping configuration as compared to that for double-end pumping configuration. In both the cases, it was noted that when the pump power was sufficiently high, intensity and occurrence of the self-pulses were reduced. However, the reduction in the intensity of self-pulses was significant in the double-end pumping. Experimental study shows that occurrence of self-pulses is due to the initial relaxation oscillations and re-absorption and there is no role of nonlinear phenomena in the generation of self-pulses. The rate equation analysis shows that the non-uniformity in single pass distribution of upper level population along the fiber length is responsible for re-absorption and hence self-pulsing. In the case of single-end pumping, single pass distribution of upper level population along the fiber length has more non-uniformity as compared to the double-end pumping, and hence stronger self-pulsing is observed. [Copyright &y& Elsevier]