ORALS

Deep-UV (DUV) coherent lights are of great importance to high-tech applications including photolithography photoemission spectroscopy, and attosecond pulse generation. An effective method for obtaining DUV laser is through cascading second-harmonic generation (SHG) of the nonlinear optical (NLO) crystals with large SHG responses, wide transparent window down to DUV region, and sufficient birefringence. Currently, except KBe2BO3F2 (KBBF), no NLO crystal is available for the direct SHG in DUV, but KBBF suffers from the two serious drawbacks, i.e. layering tendency and using carcinogenic BeO in its synthesis, which make the largest thickness of KBBF is only 3.7 mm, far from satisfying commercial requirements. Here we report a new DUV NLO crystal, Cs3B11P2O23 (CBPO), which shares all of the favorable NLO properties of KBBF, including large SHG response (3 × KDP), wide transparent region (165-3503 nm) and suitable birefringence (0.075@532 nm), but does not require BeO in the synthesis and can be easily grown as large (so far up to 20 × 17 × 8 mm3) crystal. With these crystals, we determined type-I phase-matching SHG and third harmonic generation limit of 199 and 188 nm, respectively, and successfully obtained 199 nm DUV coherent radiation based on a direct SHG of CBPO using 398 nm of fundamental laser. These indicate CBPO will be promising as the next generation of DUV NLO crystal.

References:
[1] Liu, H. A.; Wu, H. P.; Hu, Z. G.; Wang, J. Y.; Wu, Y. C.; Yu, H. W., Cs3(BOP)2(B3O7)3: A Deep-Ultraviolet Nonlinear Optical Crystal Designed by Optimizing Matching of Cation and Anion Groups. J. Am. Chem. Soc. 2023, 145, 12691-12700.