Short, Shorter, Shortest: Diode Lasers In The Deep Ultraviolet.pdf

Diode lasers in the deep ultraviolet range are being developed for various applications, including semiconductor lithography, inspection, and scientific research. Conventional laser systems have limitations in providing UV light, but novel frequency-doubling techniques and digital control electronics enable higher output powers and stable long-term operation. Diode-based laser systems can produce continuous-wave tunable UV output, and new laser sources operating in the deep-ultraviolet range can help streamline industrial and scientific applications. External-cavity diode lasers (ECDLs) achieve a free-running linewidth of a few kilohertz and can be tuned continuously without mode-hopping. Frequency-converted diode lasers provide continuous-wave light down to below 200 nm in the vacuum UV. Second-harmonic generation (SHG) via frequency-doubling of laser light is an alternative way to extend the wavelength range of diode lasers. State-of-the-art ECDLs and semiconductor tapered amplifiers (TAs) are ideal candidates for fundamental sources in frequency-converted laser systems. Steady improvements in optical semiconductor materials and frequency-doubling technology have led to increased output power and filled spectral gaps in the visible and near-UV ranges.