Abstract

In support of an integrated soft x-ray projection lithography system being developed at the Lawrence Livermore National Laboratory we are developing a kilowatt class, advanced solid state laser that requires: (1) a laser source capable of peak power in the range of 50 to 200 MW, (2) per pulse energy of about 0.5 to 1 J, and (3) repetition rates up to 1.5 kHz, to allow high volume throughput. The required pulse duration is in the range of 5 to 10 ns. A diode-pumped, solid-state laser was designed and built to meet these basic requirements. The high average power requirement dictates the use of an Nd³⁺:YAG slab of dimensions 200 x 25 x 6 mm³. The use of diode laser pumping minimizes heating of the medium. The high average power and high repetition rate are enabled by employing a laser diode array pump with a thermally efficient method of packaging in which the diode bars are mounted on micro channel coolers. These coolers minimize the thermal impedance typically associated with heat transport across the cooling water boundary layers of high-performance heat sink systems. Our laser employs two arrays each incorporating 150 diode packages and capable of providing >500 W/cm² peak power at 808 nm over an area 150 x 20 mm².

© 1994 Optical Society of America