Widely tunable ultraviolet C generation using wavelength selective external high-Q-cavity and a blue laser diode system

This paper presents a second harmonic generation scheme using a nonlinear optic crystal and a multimode Fabry-Perot blue laser diode that has potential to generate widely tunable coherent deep ultraviolet at approximately 225 nm. Using the Fabry-Perot multimode laser diode with the sum-frequency technique, a high second harmonic power is hardly observed due to low conversion efficiency. In this paper, an approximately 1 μW second harmonic ultraviolet power at around 225 nm ultraviolet wavelength and approximately 6 nm ultraviolet wavelength tunability can be obtained using a multi mode blue LD chip, a nonlinear optic crystal, and an external high-Q-cavity setup.