Relaxor-lead titanate (PbTiO₃) crystals, which exhibit extremely high piezoelectricity, are believed to possess high electro-optic (EO) coefficients. However, the optical transparency of relaxor-PbTiO₃crystals is severely reduced as a result of light scattering and reflection by domain walls, limiting electro-optic applications. Through synergistic design of a ferroelectric phase, crystal orientation, and poling technique, we successfully removed all light-scattering domain walls and achieved an extremely high transmittance of 99.6% in antireflection film–coated crystals, with an ultrahigh EO coefficientr₃₃of 900 picometers per volt (pm V⁻¹), >30 times as high as that of conventionally used EO crystals. Using these crystals, we fabricated ultracompact EO Q-switches that require very low driving voltages, with superior performance to that of commercial Q-switches. Development of these materials is important for the portability and low driving voltage of EO devices.

An electro-optic (EO) modulator is one of the most important optical devices and has been widely used in the photonic industry. Performance of EO modulators mainly depends on the property of EO materials. Here, the EO property of the (111)-oriented single domain rhombohedra phase (1-x)Pb(Mg_1/3Nb_2/3)O₃-xPbTiO₃ (PMN-PT) single crystal is investigated. Due to the light scattering by domain walls, a single domain crystal is essential and has been well prepared here by a thermal annealing and high temperature poling process. It is found that domains become irregular with significantly decreased dimension after annealing, which indicates that the ferroelastic domain walls are eliminated. A crack-free single domain crystal shows excellent optical quality, with a high transmittance of approximately 70% in near-infrared regions. Finally, the effective EO coefficient of the (111)-oriented rhombohedral phase PMN-PT crystal is measured by a Senarmont compensator amplitude modulator. An effective EO coefficient of 112 pm/V is obtained in the (111)-oriented rhombohedral phase PMN-PT crystal, which is much higher than that of the commercial LiNbO₃ crystal, indicating the potential for use in compact and low driving voltage EO devices.

An electro-optic coefficient (EOC) is an important optical property of optical crystals. In this work, a single-path multiple reflection interferometer is proposed to measure the components of signed EOCs with high precision. With the help of the normalization method, the influence of incident light was removed, and repeatability of the experimental results was improved. The signed EOCs of a congruent L i N b O 3 crystal were determined under a small external electric field as γ 31 = + 9.6 ± 0.3 p m / V and γ 33 = + 29.5 ± 0.5 p m / V . This study may contribute to the development of potential anisotropic devices of optical crystals.

The inseparability criterion provides a straightforward and efficient method for identifying and quantifying two-mode Gaussian quantum entanglement, making it a crucial tool in quantum optics experiments. However, it is crucial to recognize that the inseparability criterion serves only as a sufficient condition for entanglement assessment, thereby posing a risk of missed detection during evaluation. This paper investigates the use of the inseparability criterion in assessing two-mode squeezed states, with a particular focus on examining missed entanglement detection due to entanglement asymmetry. The results show that when decoherence symmetrically affects both modes, the inseparability criterion effectively detects entanglement. In contrast, when this symmetry is broken, the criterion may fail to identify entanglement, with the likelihood of missed detection increasing with increasing asymmetry. By comparing these results with the positive partial transpose criterion, which serves as a necessary and sufficient condition, the occurrence of missed detections by the inseparability criterion is confirmed. Our research not only provides valuable insights into the application of the inseparability criterion in quantum information tasks but also deepens the understanding of its operational principles and limitations.

Multiple-reflection (MR) effects in flat optical crystals can cause significant errors in electro-optic coefficient (EOC) measurements. We present a Mach–Zehnder interferometer method that incorporates MR modeling and suppresses its influence by selecting specific incidence angles [Θ=2m π and Θ=(2m+1) π ]. Numerical simulations with congruent lithium niobate show that angular deviations below 0.1 limit EOC errors to <2.5%. Experiments using a He–Ne laser achieve <1% variance in γ ₁₃ and γ ₃₃ , confirming theoretical predictions. The approach also enables frequency-resolved EOC characterization, offering a simple, high-precision solution for MR suppression in optical metrology.

The inseparability criterion provides a straightforward and efficient method for identifying and quantifying two-mode Gaussian quantum entanglement, making it a crucial tool in quantum optics experiments. However, it is crucial to recognize that the inseparability criterion serves only as a sufficient condition for entanglement assessment, thereby posing a risk of missed detection during evaluation. This paper investigates the use of the inseparability criterion in assessing two-mode squeezed states, with a particular focus on examining missed entanglement detection due to entanglement asymmetry. The results show that when decoherence symmetrically affects both modes, the inseparability criterion effectively detects entanglement. In contrast, when this symmetry is broken, the criterion may fail to identify entanglement, with the likelihood of missed detection increasing alongside rising asymmetry. By comparing these results with the positive partial transpose criterion, which serves as a necessary and sufficient condition, the occurrence of missed detections by the inseparability criterion is confirmed. Our research not only provide valuable insights into the application of the inseparability criterion in quantum information tasks but also deepens the understanding of its operational principles and limitations.