Mikhail Larionov

A 1-kW CW thin disc laser

The thin disc laser is presented as an optimal laser design for the operation of a quasi-three-level laser active medium in the high power regime with high optical efficiency. Numerical calculations of the laser output power show that operation with an output power up to 1 kW with an optical efficiency of 50% and more is possible at room temperature utilizing 16 absorption passes. Scaling of the output power can be realized by scaling the pumped area using one or more discs. The experimental investigations yield a maximum output power of 647 W at 51% optical efficiency for one crystal and of 1070 W with 48% optical efficiency for four crystals at a temperature of the cooling water of 15/spl deg/C.

High-repetition-rate regenerative thin-disk amplifier with 116 μJ pulse energy and 250 fs pulse duration

A thin-disk regenerative amplifier based on Yb-doped potassium yttrium tungstate is operated at 40 kHz with an output pulse energy of 116 microJ and a pulse duration of 250 fs. Dispersive stretching of the pulse during amplification instead of an external stretcher is used to avoid high peak intensities. The small amount of the laser active material in the amplifier inherent for the thin-disk laser design and a large beam radius in the Pockels cell reduce nonlinear effects further. Consequently the output pulses can be compressed to 250 fs using a pair of diffraction gratings.

Advanced pulsed thin disk laser sources

Advanced pulsed thin disk laser sources based on several pulse generation schemes, including regenerative amplification as well as cavity-dumping, will be presented. These sources are able to produce pulse energies in the multi-millijoule range at repetition rates of up to several 100 kHz, resulting in average output powers in excess of 100 W. Also the efficient intra-cavity frequency conversion of these sources will be discussed.

50 W thin-disk laser with variable pulse duration

The laser system is based on an Yb:YAG thin-disk regenerative amplifier, which is operated in different operation modes in order to address broad spectrum of pulse durations. It is especially interesting for application development tasks, when different pulse durations can be tested to find the application optimum. For sub-picosecond pulse duration the dispersion of the regenerative amplifier output is compensated with a pair of diffraction gratings. Pulses with a full width at half maximum of 334 fs at an output power level of 30 W can be produced using a nonlinear spectrum broadening during amplification. Tuning of the distance between gratings or abandoning of the compressor allows for output pulse durations of several picoseconds with an output power of 60 W. A second seed source allows for pulse durations up to several nanoseconds. Further, the amplifier was operated in cavity-dumped or in Q-switched mode just by changing of the electrical control of the Pockels cell in the amplifier. The pulse durations range is extended, correspondingly, to 100 ns and even to microseconds.

Femtosecond Thin Disk Yb:KYW Regenerative Amplifier with Astigmatism Compensation

Pulses with an energy of 116 µJ and 250 fs pulse duration at a repetition rate of 40 kHz are demonstrated. Special technique is applied to compensate the astigmatism of the laser crystal.

Thin disk laser operation and spectroscopic characterization of Yb-doped Sesquioxides

Yb:Sc2O3 and Yb:Lu2O3 crystals have been grown and analyzed spectroscopically. In the thin disk laser configuration cw operation with 61 % slope efficiency and a maximum output power of 18.3 W could be demonstrated with Yb:Sc2O3. Yb-doped potassium tungstates were also operated in a high power cw thin disk laser. 73 W of output power with more than 60 % optical efficiency and 73 % slope efficiency was achieved using Yb:KYW.

Diode pumped solid state kilohertz disk laser system for time-resolved combustion diagnostics under microgravity at the drop tower Bremen.

We describe a specially designed diode pumped solid state laser system based on the disk laser architecture for combustion diagnostics under microgravity (μg) conditions at the drop tower in Bremen. The two-stage oscillator-amplifier-system provides an excellent beam profile (TEM00) at narrowband operation (Δλ < 1 pm) and is tunable from 1018 nm to 1052 nm. The laser repetition rate of up to 4 kHz at pulse durations of 10 ns enables the tracking of processes on a millisecond time scale. Depending on the specific issue it is possible to convert the output radiation up to the fourth harmonic around 257 nm. The very compact laser system is integrated in a slightly modified drop capsule and withstands decelerations of up to 50 g (>11 ms). At first the concept of the two-stage disk laser is briefly explained, followed by a detailed description of the disk laser adaption to the drop tower requirements with special focus on the intended use under μg conditions. In order to demonstrate the capabilities of the capsule laser as a tool for μg combustion diagnostics, we finally present an investigation of the precursor-reactions before the droplet ignition using 2D imaging of the Laser Induced Fluorescence of formaldehyde.

Single-frequency tunable pulsed thin disk laser for drop tower applications

The combination of laser diagnostics and short term microgravity (/spl mu/g) conditions has become an important tool for the investigation of combustion processes. In this paper, a pulsed Yb:YAG laser tunable around 1030 nm is designed for autonomous operation under microgravity conditions. A pulse energy of 21 mJ at 1 kHz and a pulse duration of 20 ns is demonstrated.

50-kHz, 400-μJ, sub-100-fs pulses from a thin disk laser amplifier

A thin disk regenerative amplifier based on Yb:KLW (potassium lutetium tungstate) is operated in different set-ups, changing the net gain and total amount of nonlinearity during amplification. Spectrum broadening during amplification produces Lorentz-shaped pulses with an autocorrelation width of 190 fs after dispersion compenstaion. Damping of bifurcations is demonstrated by nonlinear spectrum broadening, allowing stable operation with an output energy of of nearly 400 μJ at 50 kHz.

Power scalability of thin disk lasers in fundamental mode operation

Experimental results and numerical simulations for the power scalability of an Yb:YAG thin disk laser in fundamental mode operation are presented. So far, an output power of 225 W with an M/sup 2/<1.1 is demonstrated.