Broadband trapeziform multilayer dielectric grating for femtosecond pulse compressor: design, fabrication, and analysis

Abstract

Rectangular HfO 2 grating fabrication is difficult, so a trapeziform multilayer dielectric pulse compression grating (PCG) has been designed using a genetic algorithm and the Fourier mode method. Simulation results show that a greater than 120 nm wavelength range multilayer dielectric grating (MDG) is obtained with a minus-first-order diffraction efficiency (DE) exceeding 95%. The bandwidth is 136 nm with the minus-first-order DE exceeding 90%. The trapeziform structure shows good tolerances for grating fabrication. The multilayer dielectric is deposited by e-beam evaporation, then the MDG is fabricated by reactive ion beam etching. A 128 nm bandwidth of the MDG for the transverse electric polarization with an efficiency exceeding 90% is obtained, and the maximum DE can reach up to 98.3%. The trapeziform MDG is an ideal PCG for chirped pulse amplification systems with high DE, broad bandwidth and good fabrication tolerances. Laser-induced damage thresholds of 0.53 J cm −2 under 40 fs pulses are experimentally reached with very high and uniform efficiency.

Review of pulse compression gratings for chirped pulse amplification system

“…125,126 The DE and bandwidth of MDGs have been enough optimized. [127][128][129][130][131][132][133][134][135][136][137][138] Afterward, the investigations mainly focused on the improvement of LIDT, which can be achieved through optimizing the structure and the fabrication technology, which will be discussed in Sec. 4.2.3.…”

Diffraction gratings: from principles to applications in high-intensity lasers

“…Interestingly enough, the simulated annealing algorithm [137], together with the experimental work of Martz et al using a grating etched in the top 3 layers, permitted to propose in 2014 a resonant metallo-dielectric grating etched in the top 3 layers composed of two silica layers and one hafnia layer (see Fig. 20) [141]. The grating was optimized with respect to the parameters described in Fig.…”

“…Besides a remarkable agreement between experimental and numerical plots, the results show a diffracted efficiency higher than 90% over a 163 nm bandwidth (the wavelength range of 732−895 nm). Measurements of LIDT were carried out at 45 fs [143], 800 nm wavelength and damage thresholds of 0.32 J/cm2 were obtained [141,144]. The fabrication procedure of this kind of grating was further improved in [145].…”

Design of a High-Efficiency Multilayer Dielectric Diffraction Grating with Enhanced Laser Damage Threshold

“…Nevertheless, their research had two limitations. Firstly, the metal used for this grating would exhibit losses of at least several percent due to absorption, particularly in power scaling, where such losses are completely undesirable [21]. Secondly, although the laser damage threshold (LDT) was improved, the increment still did not reach the optimal level because the electric field was still primarily focused on the HfO 2 layer, which has an average LDT of 1.97 J/cm 2 [22].…”

“…Therefore, multilayer dielectric mirrors are extensively utilized instead of metallic layers owing to their absorption-free properties [14,[19][20][21]. As a result of replacing the metal with a dielectric multilayer dielectric mirror in our investigation, the diffraction efficiency is greatly boosted.…”