Christian Theobald

Passively mode-locked picosecond Nd:YVO4 self-Raman laser

We report on a passively mode-locked Nd:YVO4 self-Raman laser which consists of two coupled resonators and generates pulses at 1176nm with a duration of 4.8ps, a repetition rate of 73MHz, and an average power of 420mW.

High energy cw-diode pumped Nd:YVO4 regenerative amplifier with efficient second harmonic generation.

We report on a 888 nm diode-pumped Nd:YVO4 regenerative amplifier with up to 33.7 W output power with a repetition-rate of 20 kHz and an adjustable pulse duration between 217 ps and 1 ns. This setup allowed for efficient second harmonic generation with an efficiency of up to 79%.

Efficient generation of mode-locked pulses in Nd:YVO 4 with a pulse duration adjustable between 34 ps and 1 ns

We report on the generation of highly stable active continuous mode-locked pulses in diode pumped Nd:YVO(4) with an adjustable pulse duration between 34 ps and 1 ns. With this laser an average output power of up to 7.3 W with an excellent stability and beam quality with a M(2)-value of < 1.1 is obtained. For all pulse durations the pulses were within a factor of 1.15 above the Fourier limit. Due to these characteristics the presented system is an attractive oscillator for OPCPA concepts.

Mode-locking of a high power, 888 nm pumped Nd:YVO 4 laser using nonlinear polarization rotation via Type I second harmonic generation

Continuous-wave mode-locking of a laser exploiting the nonlinear polarization rotation (NPR) technique via Type I second harmonic generation is demonstrated for the first time. The NPR is generated by a lithium triborate crystal and transformed into nonlinear cavity losses of a 888 nm pumped Nd:YVO4 laser. Self-starting, reliable mode-locking has been achieved at a high average output power of 20.6 W and a pulse duration of 7.3 ps. Furthermore, transform limited pulses down to 2.7 ps have been demonstrated at 9.9 W.

High-average power Nd:YVO4 regenerative amplifier seeded by a gain switched diode laser

We report on a Nd:YVO4 regenerative amplifier (RA), end pumped by 888 nm-diode lasers. The output power was about 46W at repetition rates from 150 to 833kHz with an M2-factor of 1.2. The amplifier was seeded by a gain switched diode laser, generating pulses with a duration of 65 ps and a pulse energy of ≈ 5 pJ. The high gain of the RA of more than 70 dB provides amplified pulse energies as high as 180μJ. Bifurcations of the pulse energy could be avoided. Pulse amplitude fluctuations of only 1.2% for 10,000 consecutive pulses were measured. The long term output power stability of the laboratory setup was 0.3%.

Passively Q-switched mode-locked picosecond Nd:YVO 4 self-Raman laser

We report on a passively Q-switched mode-locked Nd:YVO4 self-Raman laser generating pulses at 1176 nm with a duration of 5.9 ps and an average power of 490 mW at a repetition-rate of 75 MHz.

54 W, 150 MHz, Passively Mode-Locked TEM 00 Nd:YVO 4 Oscillator Pumped at 888 nm

We report on a passively mode-locked TEM00 Nd:YVO4 oscillator providing 54 W of power at a repetition rate of 150 MHz, thanks to the high gain of Nd:YVO4 and its optimized pumping at 888 nm.

Cavity-dumped Yb:YAG ceramic in the 20 W, 12 mJ range at 6.7 ns operating from 20 Hz to 5 kHz with fluorescence feedback control.

Increasing data acquisition rates in metrology applications based on optical parametric oscillators (OPOs) can accelerate measurement processes. To achieve this, flash-lamp systems with low pulse repetition frequencies of 10-100 Hz used as a pump source for the OPOs could be replaced by diode-pumped solid-state lasers in the kHz range. We demonstrate a 969 nm pumped Yb:YAG ceramic laser yielding 21.6 W output power, 12.5 mJ pulse energy, and excellent beam quality. Fluorescence feedback control, developed from gain dynamics simulations in two operating regimes, allows stable operation at 6.7 ns from 20 to 5000 Hz. Third harmonic generation to 343 nm yields 3.24 W at 2 kHz. The system provides constant pulse duration in a huge repetition rate interval, which is beneficial for pump sources for future metrology devices.

50W CW output power and 12mJ pulses from a quasi-2-level Yb:YAG ceramic rod laser end-pumped at the 969nm zero-phonon line

With the advent of high power and narrow bandwidth 969 nm pump diodes, direct pumping into the upper laser level of Yb:YAG and hence quasi-2-level lasers became possible. Pumping directly into the emitting level leads to higher quantum efficiency and reduction of non-radiative decay. Consequently, thermal load, thermal lensing and risk of fracture are reduced significantly. Moreover pump saturation and thermal population of uninvolved energy-levels in ground and excited states are benefical for a homogenous distribution of the pump beam as well as the reduction of reabsorption loss compared to 3-level systems, which allows for high-power DPSS lasers. Beside continuous-wave (cw) operation, nanosecond pulses with a repetition rate between 1 and 5 kHz are an attractive alternative to flashlamp-pumped systems (10-100 Hz) in various measurement applications that require higher data acquisition rates because of new faster detectors. Based on measurements of the absorption and a detailed numerical model for pump beam distribution, including beam propagation and saturation factors, power-scaling of a ceramic rod Yb:YAG oscillator was possible. Finally a cw output power of 50 W with 33 % pump efficiency at 1030 nm has been demonstrated (M2 < 1.2). Nanosecond pulses have been produced by cavity-dumping of this system. The cavity-dumped setup allowed for 3-10 ns pulses with a pulse energy of 12.5 mJ at 1 kHz (M2 < 1.1). In order to achieve these results a systematic experimental and numerical investigation on gain dynamics and the identification of different stable operating regimes has been carried out.

Generation of continuous mode-locked pulses in Nd:YVO 4 with an adjustable pulse duration between 34 ps and 1 ns

We report on highly stable active continuous mode-locking in diode-pumped Nd:YVO<inf>4</inf> with adjustable pulse durations between 34ps and 1ns. An average output power till 7.3W, an excellent beam quality M²≪1.1 and transform-limited pulses were obtained.