Generation of deep-UV sources (160-250 nm) by frequency mixing in lithium-triborate crystal

The newly discovered nonlinear crystal of lithium triborate, LiB3O5 (LBO), has several advantages over another borate family, 8-BaB2O4.13 These include nonhydroscopic, wide transparency (0.16-2.6 sm), high damage threshold and may be temperature-tuned for noncritical phase-matching (NPCM). NCPM using LBO (temperature-tuned) for the second harmonic generation (SHG) and sum frequency mixing (SFM) of N&YAG laser and YAG-laser-pumped Raman cell in H2 gas was reported.4 In this paper we present the phase-matching curves of LBO for the generation of UV-sources (160-250 nm), where 160 nm is the absorption edge of LBO crystal (see Fig. 1). In Section 2, we analyze the phasematching conditions for second harmonic generation (SHG), third harmonic generation (THG) and sum-frequency- mixing (SFM) and provide the general guidance for achieving phase-matchable shortest wavelengths. Section 3 shows the numerical results based on the Seilmeir equations of LBO, where UV and IR sources are mixed for deep-UV sources. Schematics of proposed experimental setups are also shown.