Pulse compressor grating-waveguide structure for high-power chirped pulse amplification at wavelengths around 2 µm

Area of Science:

• Optics and Photonics
• Laser Technology
• Materials Science

Background:

• High-power laser systems require efficient pulse compression for various applications.
• Existing pulse compressor gratings often face limitations in efficiency and damage threshold at specific wavelengths.
• Development of advanced optical components is crucial for enhancing laser system performance.

Purpose of the Study:

• To design and demonstrate a high-efficiency pulse compressor grating operating in reflection.
• To achieve high diffraction efficiency at a wavelength of approximately 2 micrometers for high-power laser systems.
• To evaluate the grating's performance, including spectral bandwidth, tolerance to fabrication variations, and laser-induced damage threshold.

Main Methods:

• Conceptual design of a reflection grating optimized for 2-micrometer wavelength.
• Theoretical analysis of diffraction efficiency (>99%) over a 42 nm spectral bandwidth centered at 2050 nm.
• Comprehensive tolerance analysis for fabrication parameters (groove depth, duty cycle, sidewall angle) and refractive index variations.
• Estimation of laser-induced damage threshold (>0.68 J/cm² for 500 fs pulses).
• Experimental fabrication and characterization of the pulse compressor grating.

Main Results:

• Theoretical diffraction efficiency exceeding 99% over a 42 nm bandwidth at 2050 nm.
• High theoretical laser-induced damage threshold (>0.68 J/cm² for 500 fs pulses).
• Experimental characterization confirmed a diffraction efficiency of 97% for the fabricated grating.
• This 97% efficiency is the highest reported to date for a 2-micrometer pulse compressor grating.

Conclusions:

• The demonstrated reflection grating concept offers high efficiency for 2-micrometer pulse compression.
• The grating exhibits excellent theoretical performance and a high laser-induced damage threshold, suitable for high-power laser systems.
• The achieved experimental efficiency represents a significant advancement in grating technology for this wavelength range.