MgSiP₂: An Infrared Nonlinear Optical Crystal with a Large Non‐Resonant Phase‐Matchable Second Harmonic Coefficient and High Laser Damage Threshold

Abstract

Superior infrared nonlinear optical (NLO) crystals are in urgent demand in the development of lasers and optical technologies for communications and computing. The critical challenge is to find a crystal with large non‐resonant phase‐matchable NLO coefficients and high laser damage threshold (LDTs) simultaneously, which however scale inversely. This work reports such a material, MgSiP2, that exhibits a large second harmonic generation (SHG) coefficient of d14≈d36 = 89 ± 5 pm V−1 at 1550 nm fundamental wavelength, surpassing the commercial NLO crystals AgGaS2, AgGaSe2, and ZnGeP2. First principles theory reveals the polarizability and geometric arrangement of the [SiP4] tetrahedral units as the origin of this large nonlinear response. Remarkably, it also exhibits a high LDT value of 684 GW cm−2, which is six times larger than ZnGeP2 and three times larger than CdSiP2. It has a wide transparency window of 0.53–10.35 µm, allowing broadband tunability. Further, it is Type I and Type II phase‐matchable with large effective SHG coefficients of deff,I ≈80.2 pm V−1 and deff,II ≈73.4 pm V−1. The outstanding properties of MgSiP2 make it a highly attractive candidate for optical frequency conversion in the infrared.

Novel Laser Crystal Nd:LiY(MoO4)2: Crystal Growth, Characterization, and Orthogonally Polarized Dual-Wavelength Laser

“…The LDT is a pivotal parameter to evaluate laser crystal performance, which can reflect the ability of the crystal to resist laser damage. − When the power density of the incident laser exceeds the LDT of the crystal, the surface or interior of the crystal will be damaged. Generally, the larger the input power of the pump laser, the higher the OOCE of the laser crystal.…”

Enhanced near-infrared optical transmission in zinc germanium phosphide crystals via precise magnesium doping

“…Based on the similar chalcopyrite structure of the ZGP crystals, researchers have embarked on an extensive exploration, leading to the discovery of numerous high-performance nonlinear optical materials incorporating magnesium. 43–49 Employing magnesium doping during the growth of ZGP crystals presents a viable method for manipulating their intrinsic point defect structure. This approach is designed to concurrently diminish the optical absorption and fortify the laser damage threshold, potentially leading to improvements of other functional properties.…”