Depressed cladding waveguides are fabricated in Pr:LiYF₄ (YLF) crystal by femtosecond laser inscription following a helical scheme. With the optimized parameters, the propagation loss of the waveguide is around 0.12 dB/cm for multimode guiding. Under optical pumping with InGaN laser diodes at 444 nm, efficient waveguide lasers in the orange around 604 nm (π-polarized) are achieved with minimum lasing threshold of 119.8 mW, maximum slope efficiency of 16.6%, and maximum output power of 120.6 mW. Benefiting from their optimized performances, the waveguides produced in this work are promising for applications as compact orange laser sources.

Lithium niobate (LiNbO3, LN) channel and ridge waveguides have been successfully fabricated by He ion implantation, which has energy of 500 keV and fluence of 1.5×1016ions/cm2 and is combined with lithography and the precise diamond dicing technique. The refractive index profile of the annealed LN planar waveguide was reconstructed. The propagation loss of the channel waveguide with a width of 10 µm and that of the ridge waveguides with widths of 25 µm and 15 µm were investigated by the end-face coupling method. In our work, the factors that affect the waveguide properties of channel and ridge waveguides were revealed.

We report an interesting study of electric-field-induced transformation from a single domain ferroelectric state to the multiple domain ferroelectric state in a KTa_1-xNb_xO₃ (KTN) crystal. Experimental results obtained using the confocal μ-Raman spectroscopy confirm the dynamic change of lattice structures induced by an external electric field. Furthermore, the dependence of relative permittivity on the applied voltage also indicates the transformation of ferroelectric states involving the processes of splintering, inversion, and re-formation of ferroelectric domains.

Lithium niobate (LiNbO3) is a versatile crystalline material for various photonic applications. With the recent advances in LiNbO3-on-insulator (LNOI) thin film technology, LiNbO3 has been regarded as one of the most promising platforms for multi-functional integrated photonics. In this work, we present the field enhancement due to collective resonances in arrayed LiNbO3 nanoantennas. These resonances arise from the enhanced radiative coupling of localized Mie resonances in the individual nanoparticles and Rayleigh anomalies due to in-plane diffraction orders of the lattice. We describe the pronounced differences in field enhancement and field distributions for electric and magnetic dipoles, offering valuable information for the design and optimization of high-quality-factor optical metasurfaces based on LiNbO3.

We report on the fabrication and optimization of lithium niobate planar and ridge waveguides at the wavelength of 633 nm. To obtain a planar waveguide, oxygen ions with an energy of 3.0 MeV and a fluence of 1.5×1015ions/cm2 are implanted in the polished face of LiNbO3 crystals. For planar waveguides, a loss of 0.5 dB/cm is obtained after annealing at 300°C for 30 min. The ridge waveguide is fabricated by the diamond blade dicing method on optimized planar waveguides. The guiding properties are investigated by prism coupling and end-face coupling methods.

Optical channel waveguides with depressed cladding configurations have been produced in Nd,Gd:CaF2 laser crystals by using ultrafast laser inscription. Waveguide properties are investigated in terms of guiding behaviors and localized laser-induced lattice damages. Under an optical pump of 808 nm light, continuous-wave waveguide lasing at 1.06 μm is achieved, with a single-mode operation and a minimum lasing threshold of 98.8 mW. Furthermore, the visible emissions of Nd3+ with short wavelengths ranging from 415 nm to 550 nm and long wavelengths from 550 nm to 625 nm are observed upon 808 nm laser excitation via the up-converted process. The intensity ratios of two wavelength ranges are proved to be tunable through changing the pumping polarizations.

In this Letter, we report the existence and relaxation properties of a critical phenomenon on called a 3D super crystal that emerges at T = T_C ? 3.5°C, that is, in the proximity of the Curie temperature of a Cu:KTN sample. The dynamics processes of a 3D super crystal manifest in its formation containing polarized nanometric regions and/or polarized clusters. However, with strong coupling and interaction of microcomponents, the characteristic relaxation time measured by dynamic light scattering demonstrates a fully new relaxation mechanism with a much longer relaxation time. As the relaxation mechanism of a relaxator is so-far undetermined, this research provides a novel perspective. These results can help structure a fundamental theory of ferroelectric relaxation.