Design and angle robustness test of chirped periodically poled lithium niobate crystal for 1064nm SHG experiment

Abstract

The 532 nm solid-state laser, generated by means of second-harmonic generation (SHG) technology, has become one of the most extensively used lasers in various applications today. In the tradition scheme, the most prevalent SHG crystal of the 532 nm solid-state is lithium borate (LBO), continues to exhibit insufficient angle robustness and SHG efficiency. In an attempt to overcome these limitations and achieve a SHG crystal with better angle robustness, the research commences with a comprehensive theoretical analysis of angle robustness. On this basis, it proceeds to design the structure of a chirped periodically poled lithium niobate (CPPLN) crystal, taking into account the desired properties for improved performance. The study then implements theoretical simulations and experimental tests to validate the effectiveness of the designed crystal. The simulation results corroborate the superior angle robustness of the CPPLN crystal. Within the range of -3° to +3°, the designed CPPLN crystal exhibits a maximum SHG efficiency of 0.80% and a minimum of 0.51%, which indicates that the SHG efficiency of this crystal in this range can be maintained at 60% of the maximum efficiency. The experimental results show that the SHG efficiency can be more than 11 times that of LBO crystal. Moreover, the study reveals that the half-width of the actual SHG efficiency about the incident angle of the designed CPPLN crystal can exceed 6°, indicating its exceptional tolerance to variations in the incident angle. Furthermore, the output spot of the SHG light generated by the designed CPPLN crystal exhibits a standard Gaussian profile, which remains virtually unaffected by the incident angle. In conclusion, the findings of this research highlight the CPPLN crystal as a promising alternative to LBO, boasting a markedly higher SHG efficiency and better angle robustness. These superior characteristics make the CPPLN crystal a highly attractive candidate for use in a wide array of laser applications.