ABSTRACT
Optical interferometers are typically categorized by their source type into incoherent (white-light) and coherent (laser). Both approaches provide adequate solutions for many measurement applications, offer unique advantages, and suffer distinct limitations. A novel interferometry method, spectrally controlled interferometry, is presented, which successfully merges many advantages from both categories while bypassing some of the limitations. The relationship between measurement accuracy and fringe stability as a function of fundamental control parameters is explored. Surface measurements of common optical components are presented, and method specific noise sources and measurement accuracy are assessed as well.
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.
