Petr Hiršl

Quasi-continuously pumped passively mode-locked operation of a Nd:GdVO4 and Nd:YVO4 laser in a bounce geometry

The comparative study of pulsed diode pumped Nd:GdVO4 and Nd:YVO4 slab lasers in a bounce geometry in a free running and a passively mode-locked regime was performed. The better efficiency of Nd:GdVO4 in both regimes was obtained. In the free running regime the efficiency of 39% was achieved from Nd:GdVO4 comparing with 28% from Nd:YVO4. Passive mode-locking of both lasers using a semiconductor saturable absorber in the transmission mode was demonstrated. Trains containing 6 pulses were generated in both cases but the pump energy for Nd:GdVO4 was 50% lower. The single pulse extraction using cavity dumping was demonstrated with contrast better than 10−3.

Passively Q-switched quasi-continuously pumped 2.4% Nd:YAG laser in a bounce geometry

We report on quasi-continuously pumped laser based on highly 2.4 at.% doped crystalline Nd:YAG in a bounce geometry passively Q-switched by a Cr:YAG and V:YAG saturable absorber respectively. The optimization of laser parameters and successive pulse amplification in the second Nd:YAG crystal led to efficient linearly polarized operation. At 1.06 μm the oscillator 5 ns long output pulse with energy of 1.3 mJ was further amplified to 3.5 mJ. At 1.3 μm the 13 ns long output pulse with energy of 600 μJ was amplified to 800 μJ in single pass.

Mode locked Nd:YVO4 laser with intracavity synchronously pumped optical parametric oscillator

The motivation of this work is the development of laser sensor and gyroscope based on short pulse solid state ring laser. In comparison with regular ring laser containing the gain medium and saturable absorber, where counterpropagating pulses overlap, a ring synchronously pumped optical parametric oscillator, in which the pulse crossing point is controlled externally by the time of arrival of the pump pulses, is the ideal source for short pulse laser sensor. The optimum configuration is a synchronously pumped parametric oscillator inserted inside the optical resonator of the diode pumped mode-locked solid state laser. We are developing a such system, as a first step we have demonstrated operation of a diode pumped Nd:YVO4 passively mode-locked laser using semiconductor saturable absorber with synchronously pumped intracavity optical parametric oscillator in linear configuration. The repetition rate of the pump laser was 132 MHz and the pulse duration of 15 ps. Parametric oscillator was based on 20 mm long Brewster cut single grating (with poling periode of 30.3 μm) periodically poled magnesium doped lithium niobate (MgO:PPLN) crystal. The temperature tuning of parametric luminescence from the crystal with peak wavelength at 1537 nm - 1550 nm for temperature variation from 30 °C to 57 °C was observed.

Cavity dumping of single 19 ps pulses from passively mode-locked quasi-continuously pumped highly doped Nd:YAG laser

The common approach for a picosecond laser source with output energy in millijoule level is a continuously pumped mode locked oscillator with single pulse selector followed by a regenerative amplifier. Systems can operate with repetition rates up to 100 kHz with single pulse duration around 10 ps. For many applications, as for example laser ranging, lasers operating at repetition rates below 1 kHz with longer pulse durations are more suitable. Such pulses can be obtained from passively mode-locked lasers with pulsed pumping, where the microjoule pulses are generated directly from oscillators and simple single or double pass amplifiers are sufficient for additional pulse amplification. Recently we reported about development of a 0.8 mJ laser with output pulse duration of 113 ps, where for passive mode-locking special semiconductor saturable absorbers with 100 quantum wells were used under Brewster angle in resonator in transmission mode [1].

Quasi-continuously pumped operation of 2.4% doped crystalline Nd:YAG in a bounce geometry

We report on efficient operation of highly doped 2.4 at. % crystalline Czochralski grown Nd:YAG at 1.06μm, 1.3μm and 1.4μm in a diode pumped bounce amplifier configuration under quasi-continuous pumping. At wavelength of 1064nm the linearly polarized pulses with energy of 16.8 mJ in free running regime with repetition rate of 10 Hz (optical to optical efficiency of 44.6 % and slope efficiency of 50%) and 1 mJ in passively Q-switched regime with pulse duration of 6.4 ns were generated.The passively Q switched operation at 1.3μm was also demonstrated.

Pulse shortening by passive negative feedback in mode-locked train from highly-doped Nd:YAG in a bounce geometry

Investigation of pulse shortening by passive negative feedback in mode locked train from 2.4 at. % crystalline Czochralski grown Nd:YAG in a bounce geometry under QCW diode pumping is reported. For passive mode locking a semiconductor saturable absorber with 33 quantum wells grown on GaAa substrate acting also as nonlinear element for passive negative feedback by beam defocusing was used. Temporal diagnostics was performed with high speed digital oscilloscope with bandwidth of 9 GHz combined with fast photodiode which enabled direct observation of pulse shortening along extended pulse trains from single laser shot. Efficient pulse shortening from 120 ps in the beginning of the train to 35 ps for pulses at the end of the extended train containing more than 100 pulses was achieved.

Passively mode locked quasi-continuously pumped 2.4% doped crystalline Nd:YAG laser in a bounce geometry

In this paper we report on optimization of quasi-continuously pumped 2.4at.% Nd crystalline Nd:YAG laser in a bounce geometry passively mode-locked by semiconductor saturable absorbers consisted of 33 or 100 quantum wells in transmission mode. Depending on the laser resonator configuration, either long output trains consisted of more than 100 pulses with total energy of 170 μJ and variable pulse duration from 120 ps in the beginning to 35 ps at the end of the train, or short trains consisted of 5 pulses and the total energy of 325 μJ with 71 ps pulse duration were generated.

15 ps quasi-continuously pumped passively mode-locked 2.4% doped Nd:YAG laser in bounce geometry

Passive mode-locking of a quasi-continuously pumped 2.4% Nd:YAG slab in a bounce geometry is reported. The 500 μJ trains with 15 ps pulse duration and excellent stability ± 2 ps were generated.

Quasi-continuously pumped passively mode-locked 2.4% doped Nd:YAG oscillator-amplifier system in a bounce geometry

We report on oscillator-amplifier system based on two highly doped 2.4 at. % crystalline Czochralski grown Nd:YAG crystals in a diode pumped bounce geometry configuration under quasi-continuous pumping. The oscillator was passively mode-locked by the semiconductor saturable absorber in transmission mode. The output pulse train consisted of 5 pulses with total energy of 270 μJ and pulse duration of 75 ps. The output train from the oscillator was amplified to the energy of 1 mJ by single pass amplifier.

Pr:YAP Q-switched laser operation

The powerful radiation in the visible part of spectrum is suitable for basic physical experiments as well as for many applications (spectroscopy, medicine, etc.). So far, a lot has been reported about Pr-laser action in free-running regime with low power output. In all those examples, the output generation was cw or pulses with lengths within µs region. Therefore, the peak power from those outputs was not high. Some of those lasers proved to work in mode-locking regime [1]. In that case, the peak power obtained was of the order of tens of watts. To our knowledge, there is still a gap for materials based on Pr3+ ions in nanosecond pulse region.