With reception in the h-bar afterwards.
General audience abstract Application-friendly sources of coherent radiation in the soft X-ray (SXR: 0.6 - 8 nm, 2 - 0.15 keV) are currently limited to select large-scale facilities such as synchrotrons and XFELs. Nonetheless, scientific and technology-enabling applications for SXR light abound: from bio-imaging, to semiconductor metrology, to studying the fastest dynamics in matter. We are developing a stable, tabletop source of coherent SXR light that utilizes an extreme nonlinear optical process known as high-harmonic generation (HHG) to up-convert ultrafast, energetic pulses of mid-infrared laser light. In this talk, I will describe our ground-up development of a 3 µm wavelength optical parametric chirped pulse amplifier (OPCPA) and a novel high-harmonic source.
Technical abstract Coherent light sources in the soft X-ray region (SXR: 0.6 - 8 nm, 2 - 0.15 keV) are vital to a number of scientific and industrial applications. The short wavelength and well-defined absorption features throughout this spectral region impart SXR imaging and spectroscopy techniques with excellent elemental specificity and high spatial resolution - enabling applications ranging from bioimaging in the water window (284-532 eV) to semiconductor metrology. At present, coherent SXR sources are generally limited to less-accessible large-scale facilities such as synchrotrons and XFELs. In this work, we present a stable, tabletop source of coherent SXR light that uses high-harmonic generation (HHG) to convert pulses of mid-infrared laser light to pulses of spatially and temporally coherent SXR light. We describe the ground-up development of a 1 kHz, 3 µm wavelength optical parametric chirped pulse amplification (OPCPA) system generating ∼650 µJ, 100 fs near-transform limited pulses used to drive HHG. Optical parametric amplification (OPA) is done in four-stages, each utilizing a periodically-poled lithium niobate nonlinear crystal and pumped by a ∼20 mJ single-stage, uncompressed cryogenically-cooled Yb:YAG regenerative amplifier. We use numerical simulations to inform the optimization of the OPA process. The highly stable, all-fiber front-end is based on a single twin-output erbium oscillator. The 1 µm seed for the regenerative amplifier is formed via dispersive wave generation in a highly nonlinear fiber, and the broadband, 35 fs 1.5 µm OPA seed is generated in a dispersion-managed erbium fiber amplifier. A modular high-harmonic source was developed with an emphasis on differential pumping and versatility. Using a multiatmosphere gas cell, we generated high-harmonics in argon reaching the argon absorption edge at 248 eV and to just above the carbon K-edge (284 eV) using nitrogen gas. The source is applications oriented by design, with an emphasis on stability and robustness. We present an avenue towards the generation of harmonics in the keV range using helium gas.