MLD vs. Transmission Gratings for the Highest-Efficiency, Most-Compact Pulse Compressors

OSA High-brightness Sources and Light-driven Interactions Congress 2020 (EUVXRAY, HILAS, MICS)
OSA Technical Digest (Optical Society of America, 2020), paper HM2B.2

Author:  T. Erdogan

Contrary to popular belief MLD gratings can be designed with a wide range of periods to provide the highest overall efficiency pulse compressors that are as compact and flexible as those based on transmission gratings.

Compact compressor with a single MLD grating

All-dielectric diffraction gratings are well-suited for chirped-pulse amplification (CPA) lasers with pulse lengths as short as 100’s of fs and moderate bandwidths up to 10’s of nm. They provide higher diffraction efficiency and laser-induced damage threshold than metallic reflection gratings, resulting in higher overall compressor efficiency and more compact compressor formats, and have extremely low absorption loss. Low loss is especially important for high-repetition-rate, high-average-power (HAP) lasers. The two primary types of all-dielectric gratings are surface-relief transmission and multi-layer dielectric (MLD) reflection gratings. Here we compare these two types of gratings for 1 μm laser applications (e.g., 1030 nm Yb-based systems) in terms of compressor efficiency and compactness, including practical considerations like manufacturability.

Plymouth Grating Laboratory is dedicated to making the highest-quality diffraction gratings available today. Our focus is on lasers and laser systems. PGL gratings offer exceptionally high diffraction efficiency and laser damage threshold, combined with superior wavefront error and uniformity over large areas. This performance is made possible by PGL’s exclusive use of the Nanoruler, based on the proprietary Scanning Beam Interference Lithography technology developed at MIT, and PGL’s industry-leading process expertise. The company occupies 20,000 sq. ft. of dedicated manufacturing, engineering, and office space in Carver, MA, just outside of Plymouth, and about 45 miles south of Boston.

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