Hour-long continuous operation of a tabletop soft x-ray laser at 50-100 Hz repetition rate

Brendan A Reagan,Carmen S Menoni,Mario C Marconi,Wei Li,Jorge J Rocca,Chase Salsbury,Lukasz Urbanski,Keith A Wernsing,Cory Baumgarten

doi:10.1364/oe.21.028380

Abstract

We report the uninterrupted operation of an 18.9 nm wavelength tabletop soft x-ray laser at 100 Hz repetition rate for extended periods of time. An average power of about 0.1 mW was obtained by irradiating a Mo target with pulses from a compact diode-pumped chirped pulse amplification Yb:YAG laser. Series of up to 1.8 x 10(5) consecutive laser pulses of ~1 µJ energy were generated by displacing the surface of a high shot-capacity rotating molybdenum target by ~2 µm between laser shots. As a proof-of-principle demonstration of the use of this compact ultrashort wavelength laser in applications requiring a high average power coherent beam, we lithographically printed an array of nanometer-scale features using coherent Talbot self-imaging.

Highlights

Applications of coherent soft x-ray radiation made possible by compact soft x-ray lasers (SXRLs) have been demonstrated in several areas and have a promising future in basic research and technology
We have demonstrated the continuous operation of a compact λ = 18.9 nm SXRL at 100 Hz repetition rate for extended periods of time
Combining a soft x-ray plasma amplifier heated by a diode-pumped Yb:YAG laser driver with a high shot-capacity rotating target, we demonstrated the uninterrupted generation of a λ = 18.9 nm laser with ~0.1 mW average power for 30 minutes

Summary

Introduction

Applications of coherent soft x-ray radiation made possible by compact soft x-ray lasers (SXRLs) have been demonstrated in several areas and have a promising future in basic research and technology These applications include soft x-ray interferometry to study dense plasmas [1] and surface dynamics [2], ultra-high resolution microscopy [3, 4], actinic defect inspection of the generation of lithographic masks [5], nanometer-scale probing of surfaces [6], studies of radiation damage in DNA [7], the fabrication of very fine features through laser nano-machining [8], and defect-free coherent lithography [9]. As a demonstration of the enabling power of this laser for applications requiring a high photon flux, we made use of it as a coherent illumination source to print an array of nanometer-scale features by coherent lithography exploiting the Talbot self-imaging effect

Compact high repetition rate soft x-ray laser setup

Continuous high repetition rate soft x-ray laser performance

Coherent soft x-ray laser-based nano-printing

Conclusions