Multi-microjoule, MHz repetition rate Ti:sapphire ultrafast regenerative amplifier system

Xiaoshi Zhang,Henry Kaptyen,Sterling Backus,Greg Taft,Eric Schneider,Margaret Murnane

doi:10.1364/oe.20.007015

Abstract

We demonstrate a cryogenically cooled Ti:sapphire ultrafast regenerative amplifier laser system producing >20 μJ energies at 50 kHz, >12 μJ at 200 kHz and >3.5 μJ at 1MHz with repetition rates continuously tunable from 50 kHz up to 1.7 MHz in a footprint of only 60x180 cm². This laser uses down-chirped pulse amplification employing a grism stretcher and a glass-block compressor, achieving sub-60-fs pulse duration. This laser represents a several-times improvement in repetition-rate and average power over past Ti:sapphire-based ultrafast lasers in this class. We discuss the unique challenges and solutions for this laser system. This laser system has wide applications especially in ultrafast photoemission, nonlinear imaging and spectroscopy, as well as for micro/nano-machining and ultrafast laser therapy and surgery.

Highlights

We demonstrate a cryogenically cooled Ti:sapphire ultrafast regenerative amplifier laser system producing >20 μJ energies at 50 kHz, >12 μJ at 200 kHz and >3.5 μJ at 1MHz with repetition rates continuously tunable from 50 kHz up to 1.7 MHz in a footprint of only 60x180 cm2
A large number of scientific and industrial applications benefit from the use of laser pulses with moderate energy (~μJ) and ultrashort sub-100fs duration at the highest possible repetition rate
In scientific applications such as pump-probe multi-dimensional spectroscopy [1] for studying chemical/biological dynamics, or photoelectron spectroscopy, highly tunable laser pulses and extensive signal averaging are necessary to extract small signals

Summary

Introduction

A large number of scientific and industrial applications benefit from the use of laser pulses with moderate energy (~μJ) and ultrashort sub-100fs duration at the highest possible repetition rate. Other applications that benefit from moderate energy laser pulses at high repetition rates include ultrafast electron microscopy and diffraction imaging [2, 3], which are powerful techniques for investigating structural dynamics in condensed matter under unprecedented “atomic”scale spatial and femtosecond-scale temporal resolutions. Considerable evidence suggests that the shortest possible pulses with very “clean” pulse structure are necessary for machining the most-fragile materials, making a Ti:sapphire laser a viable contender in this area—especially if the repetition-rate of the laser can be increased to maximize throughput Another example is the use of high harmonic generation to achieve a table-top “laser” like EUV/Soft X-ray source for applications such as extreme-UV (EUV) metrology, high-resolution EUV imaging, and microscopy, that benefit from high average power and high repetition rate.

Laser system

Challenges

Findings

Conclusion and summary