Thorsten Ulm

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 mode-locked 1 GHz MOPA system generating sub-500-fs pulses after external compression

We compared the performance of DQW and TQW edge-emitters in a passively mode-locked 1GHz MOPA system at 1075 nm wavelength. Passive mode-locking is induced by applying a reverse DC voltage to the absorber section. The average power is increased up to 0.9Wby a single-stripe pre-amplifier and a tapered amplifier. After compensation of the quadratic chirp in a grating compressor we achieved a pulse duration of 342 fs. We found that the oscillator gain current and the absorber bias voltage have significant impact on the pulse duration. Both parameters were used to optimize the MOPA system with respect to the shortest pulse length after compression.

High Power Femtosecond Diode Lasers

We present a concept for a femtosecond laser based on a passively mode-locked semiconductor diode laser and a tapered amplifier. The absorption in the monolithically integrated quantum well absorber is controlled by a reverse voltage bias. Excellent mode-locking stability was observed without any rf modulation applied to gain current or absorber voltage. To avoid fast gain saturation and strong nonlinear pulse distortions within the tapered amplifier the technique of chirped pulse amplification is applied. In contrast to common chirped pulse amplification setups the oscillator emits pre-chirped pulses and a stretcher stage can be omitted. A pulse duration of 267 fs was achieved after compression in the colliding pulse mode-locking regime. For the first time we adapted this technique to the generation of tailored chirped pulses and investigated the influence of the collision point in an asymmetric two-section oscillator. This diode laser system is suited as a ultrafast pulse source for high power bulk or fiber amplifiers and paves a road to highly integrated laser systems.

InGaAs diode laser system for the generation of 480 fs long pulses with 340 W peak power

480 fs long pulses with 340 W peak power are generated with an InGaAs diode laser MOPA system and a grating compressor, without stretching the pulses before amplification as required in commonly used CPA systems.

Diode laser MOPA system for the generation of 920 nm femtosecond pulses with 65 W peak power

A master oscillator power amplifier (MOPA) generates chirped 3ps pulses at 920nm with a repetition rate of 4GHz. Without requiring CPA the pulses are compressed to 600fs with a peak power of up to 65W.