High-power, narrow-width, high-repetition-rate, 5.9 eV light source using a passive optical cavity for laser-based photoelectron spectroscopy

Abstract

Summary form only given. Angle-resolved photoelectron spectroscopy (ARPES) is a powerful tool to provide direct information on the electronic structures of materials in energy-momentum space. Recent instrumental developments offer us an opportunity to explore fine structures near the Fermi surface [1, 2]. To use the capability of high-resolution ARPES, we should develop vacuum ultraviolet (VUV) light sources with sub-meV linewidths. However, using the typical light sources of synchrotron radiation and gas discharge lamps, it takes much time to acquire photoelectron spectra with a sufficient signal-to-noise ratio, because of the shortage of the photon flux per wavelength. On the other hand, laser-based light sources have many advantages such as high photon flux densities, high spatial coherence, and easy polarization control. Generally, the conversion efficiency from a sub-meV, near-infrared mode-locked laser to VUV (e.g. fourth-harmonic (FH) generation) is low since the peak intensity of the fundamental is not enough, preventing widespread use of such laser-based sources. To demonstrate the efficient conversion from near infrared to VUV, we developed a narrow-width (<; 0.5 meV), 5.9 eV light source from a 1 W, Ti:sapphire mode-locked laser with the pulse duration and the repetition rate of 10 ps and 73 MHz, respectively, using a passive optical cavity (Ref. [4] demonstrates efficient generation of 205 nm light from a 1.3 ps Ti:sapphire oscillator) and commercially-available nonlinear crystals.