2025/03/12 by Wu‐Zhen Li, Li, Wuzhen, Zhi‐Yuan Zhou +5
Materials Science · Physics and Astronomy · Biochemistry, Genetics and Molecular Biology · #Nonlinear Optical Materials Research #Optical and Acousto-Optic Technologies #Spectroscopy Techniques in Biomedical and Chemical Research
paper · pdf · doi:10.48550/arxiv.2503.09023
Given that the phase amplification method based on harmonic generation exhibits significant phase super-resolution capability in interferometric precision measurement, extending this technology to birefringence interferometers to achieve super-resolution characterization of birefringent crystal properties has important research significance and application value. Here, we achieve a four-fold enhancement in the measurement resolution of the thermo-optic coefficient of a KTiOPO4 crystal by combining a self-stabilized birefringence interferometer with cascaded second harmonic generation processes. We observe the tunable interference beating phenomenon by rotating a birefringent crystal versus the temperature of the crystal for the fundamental wave, second harmonic, and fourth harmonic. Furthermore, the fourth harmonic interference fringes beat 4 times faster than the fundamental wave interference fringes. This beating effect is used to determine the thermo-optic coefficients of the two principal refractive axes with a single measurement. This work provides a feasible, real-time, and robust method for super-resolution measurements based on birefringence interferometry.