Through key technologies such as short-wave continuous ultraviolet laser pointer pump integration, resonator design, mode matching, nonlinear frequency conversion, and optical film production, break through the technical problems of continuous short-wave ultraviolet laser operation, high efficiency, high power and long-term stable operation, and launch the 261 nm short-wave continuous ultraviolet laser.
The laser is a laser diode directly pumped intracavity frequency doubled short-wave ultraviolet all-solid-state laser, as shown in Figure 3. It is mainly composed of a semiconductor laser (LD), a pumped optical shaping mirror, a pumped optical coupling mirror group, a laser gain medium (Pr3+ crystal), a nonlinear frequency doubling crystal (BBO) and two plano-concave mirrors. This laser uses a folded V-shaped resonator.
The folded resonator can provide two optimal beam waists, in the nonlinear crystal and the green laser pointer gain medium, respectively. One beam waist can meet the pattern matching condition, and the other can improve the frequency doubling efficiency. The LD emits a laser with a wavelength of 444 nm corresponding to the absorption of the Pr3+ crystal. The optical distribution of the LD is shaped by pumping the optical shaping lens group, and then injected into the Pr3+ crystal by the pumping optical coupling lens group. The transparent surfaces of the Pr3+ crystals are parallel to each other and coaxial with the resonant cavity.
The nonlinear crystal BBO doubles the frequency of the 522 nm fundamental frequency light in the cavity to achieve a solid-state, continuous 261 nm short-wave ultraviolet laser output. Folding resonators can be made very compact, resulting in mechanical stability. The whole second harmonic generation (SHG) is realized by the reflection of the resonator mirror in one direction, and there is no extra risk of ultraviolet rays passing through the gain material to prevent its optical degradation. In addition, Pr3+ crystals, nonlinear crystals and LDs are all strictly and precisely controlled by a semiconductor cooler (TEC) to achieve stable operation of the laser.