It is hard to judge quality of CaF2 window from its nominal specification, because suppliers are used to testing products performance under relatively weak spectral lines from lamp, which can not tell the real operation behavior of CaF2 window under intense laser irradiation. We report a method of testing the transmissivity of three different grade commercially available CaF2 windows under high pulse repetition rate laser irradiation at 193nm, and the lab prototype of test module distinguishes them well with a repeatability better than 2%.
Due to complex kinetics of formation and loss mechanisms, such as ion-ion recombination reaction, neutral species harpoon reaction, excited state quenching and photon absorption, as well as their interactions, the performance behavior of different laser gas medium parameters for excimer laser varies greatly. Therefore, the effects of gas composition and total gas pressure on excimer laser performance attract continual research studies. In this work, orthogonal experimental design (OED) is used to investigate quantitative and qualitative correlations between output laser energy characteristics and gas medium parameters for an ArF excimer laser with plano-plano optical resonator operation. Optimized output laser energy with good pulse to pulse stability can be obtained effectively by proper selection of the gas medium parameters, which makes the most of the ArF excimer laser device. Simple and efficient method for gas medium optimization is proposed and demonstrated experimentally, which provides a global and systematic solution. By detailed statistical analysis, the significance sequence of relevant parameter factors and the optimized composition for gas medium parameters are obtained. Compared with conventional route of varying single gas parameter factor sequentially, this paper presents a more comprehensive way of considering multivariables simultaneously, which seems promising in striking an appropriate balance among various complicated parameters for power scaling study of an excimer laser.
A self-seeded discharge-excited ArF excimer laser oscillator using a dual-cavity configuration with long cavity lengths was developed and characterized. Proper designs for effective mode-locking in long cavity-lengths are proposed and demonstrated experimentally, which will significantly improve the energy and monochromaticity. By using the techniques of efficient mode-locking, self-seeded laser outputs with nearly the same linewidths with the seeders and larger energies are obtained. And the mode-locking can be achieved at different laser linewidths and wavelength centers.
A coherence length tunable solid-state laser based on Fabry-Perot (F-P) etalon with high stability is constructed. Principles of the coherence length tuning method by rotating the F-P etalon are theoretically analyzed and experimentally verified. By using Nd:YAG as the gain medium, an all-solid-state 1064 nm laser with 375 mW output power, 0.37% high power stability(RMS), high beam quality, and tunable coherence lengths from 9.37 cm to 20.05 cm is achieved. This method could be extended to multiband center wavelengths for their tuning of coherence length.
The inscription method of FBGs on large-mode-area double-clad fibers (LMA-DCFs) with phase mask technique was
described. A pair of LMA FBGs was prepared and the center wavelengths of them were both around 1076nm with 3 dB
bandwidths of about 0.5nm. The reflectivities of them are 99% and 10% in the fundamental mode, respectively. In order
to be protected and to withstand high-power laser, the FBGs were metally packaged, and then applied to an Yb3+-doped
LMA-DCF laser as the laser cavity. An output power of 314 W centered at 1075.71 nm with a slope efficiency of 60%