Fused silica transmission grating plays an important role in the ultra-short laser pulse compression system. Fused silica transmission grating have the advantages of high diffraction efficiency, high damage threshold, long life and no shelter. The design and fabrication of pulse compression grating are investigated theoretically and experimentally in this paper. Rigorous coupled wave theory is used for design transmission grating with trapezoidal structure. The trapezoidal structure has better diffraction efficiency than that of the rectangular structure. The deep-etched fused silica transmission grating (1250lp/mm) is fabricated by holographic recording and ion beam etching. The aperture of transmission grating is Φ65mm, and its thickness is 1mm.The absolute -1st diffraction efficiency is about to 98%(@808nm). Experimental results are coincident with the theoretical analysis.
A nondestructive, accurate and fast method for measuring the grating parameters of relief gratings is proposed in this paper. At first, the 0th diffractive transmission efficiency spectrum from 600nm to 700nm is obtained according to a certain relief grating model with the rigorous coupled-wave analysis (RCWA). Under the condition of normal incidence, the 0th diffractive transmission efficiency will behave as a function of duty cycles, depths and profiles of grooves for both TE and TM polarization. Then the data of the 0th diffractive transmission efficiency spectrum for TE polarization is regarded as measured values of simulation. Finally, grating parameters are obtained with the library matching method. Theoretical analysis and numerical simulation results demonstrate the feasibility and validity of the proposed method. Being accurate, repeatable and nondestructive, this kind of method will obtain the grating parameters quickly in practice without comprehensive and expensive but only commonly spectrometer that will be convenient for measurement of grating parameters in situ.
A novel pulse compression device has been developed for femto-second Ti: sapphire laser at 800nm center wavelength
with 700nm~900nm bandwidth. This new kind of composite pulse compression device consists of two fused silica
transmission gratings with 1250lp/mm and 3300lp/mm respectively and these two fused silica transmission gratings are
located in two optical surfaces of the same fused silica plate. Owing to use anti-reflection transmission gratings with high
space frequency (3300lp/mm), it can avoid the wave-front distort derived from coating antireflection film on one surface
of the fused silica plate. Being made of fused silica, this new composite pulse compression device will be expected to
have high laser damage threshold. The calculation results show that: the -1st order diffraction efficiency of 1250lp/mm
grating is over 87% within the 700nm and 900nm broad-bandwidth for rectangular groove and TE polarization state. And
the average diffraction efficiency within the 700nm and 900nm broad-bandwidth is more than 92%. At 800nm, the -1st
transmitted order diffraction efficiency is great to 96% while the transmittance of 3300lp/mm grating is up to 99.9%.
Analytical phase expressions are presented for an Offner stretcher and transmission grating compressor based on ray
tracing and apply them to analyze a chirped-pulse-amplification (CPA) system. Besides, an optimization method to extract
high-fidelity amplified pulse is proposed by controlling the phase of the entire system. Through theoretical analysis and
numerical simulation, one can adjust the incident angle and perpendicular distance between gratings to completely
compensate dispersion of Offner stretcher over entire wavelength. Finally, the optimized CPA system provides
Fourier-transform-limit pulse which is identical with seed pulse.
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