Vortrag von Dr. Christelle Kieleck vom Deutsch-Französischen Forschungsinstitut Saint-Louis:
Recent Advances in High‐Power Sources in the 1.5‐5 μm Range
Photonic sources in the short-wave to mid-wave infrared (SWIR to MIR) wavelength region are key elements for many current and future applications, e.g. in medicine, environmental sensing, LIDAR, stand-off spectroscopy and detection or for infrared countermeasures or laser effectors. High output power or pulse energy at simultaneously high beam quality at wavelengths in the atmospheric transmission windows around 1.5 μm, 2 μm and between 3 μm to 5 μm are essential, and many applications pose high demands on size, weight and power efficiency. Thus, research has to focus on attaining and pushing the true limits of single-source lasers and non-linear converters employing novel laser components and concepts.
In Er3+-doped solid-state lasers emitting at 1.6 μm substantial progress has been achieved for illumination or LIDAR applications creating 30 mJ/30 ns pulses at 30 Hz with M2~1. To address high-power laser effectors at 1.6 μm, the Er3+:YAG heat-capacity laser was developed, keeping the current record of 4.6 kW of output power. To increase beam quality a novel intra-cavity adaptive optic has been realized and current research addresses ceramic laser media for optimum thermal management. A scaled source with 25-30 kW of output power is under construction.
Considerably high output power and energy have been demonstrated with Tm3+-doped and Tm3+,Ho3+-codoped fiber lasers around 2-2.1 μm delivering the full output peak power and average power out of a single oscillator, thus avoiding complex multi-stage amplifiers. They are ideal sources for direct applications or for pumping nonlinear frequency converters or non-linear fibers for the 3-5 μm range.
The mid-infrared range is addressed by optical parametric oscillators (OPO) based on either ZnGeP2 or Orientation-Patterned GaAs non-linear crystals directly pumped by optimized 2 μm pump sources, achieving 10-W-level output power in high-repetition-rate operation in the MIR.
High-power ultra-broadband mid-IR supercontinuum is generated by pumping non-linear fibers with simultaneously Q-switched and mode-locked Tm3+:silica fiber lasers, creating up to 2000 times higher pulse energy than conventional mode-locked fiber lasers. In ZBLAN fibers an emission to beyond 4.2 μm with high power (7.8 W) and high conversion efficiency was achieved. Further extension of the supercontinuum in non-linear chalcogenide fibers has been demonstrated for the first time, thus validating the concept of cascaded supercontinuum generation.
Using novel OPO cavities based on fractional image rotation, allowing for high ruggedness, beam quality and simplicity, record-high pulse energies of > 120 mJ / 15 ns in the 3-5 μm range with up to 78 % conversion slope based on Q-switched 2 μm pumping have been achieved. These sources will enable new high-pulse energy applications in the MIR range.
Vortragssprache ist die des angegebenen Vortragstitels.
Einladender: Prof. Dr. N. Joly
Kontakt: Prof. Dr. N. Lindlein