Refractive index engineering through swift heavy ion irradiation of LiNbO3 crystal towards improved light guidance.

Swift heavy ion irradiation has been widely used to modify refractive indices of optical materials for waveguide fabrication. In this work, we propose refractive index engineering by swift heavy ion (Ar) irradiation via electronic energy deposition to construct waveguides of diverse geometries in LiNbO3 crystal. The feasibility to modulate the refractive index of LiNbO3 crystal at variable depths through electronic energy depositions of argon ions at different energies has been experimentally explored. The surface and cladding-like optical waveguides with thicknesses of ~13, ~36 and ~23 µm have been produced by using swift Ar ion irradiation at single energy of ~120, ~240, and double energy of (120 + 240) MeV, respectively. The fabricated waveguides are capable of effective waveguiding in single and multiple modes at 1064 nm, which enables efficient guided-wave second harmonic generation at room temperature. This work paves the way to produce waveguides with diverse geometries in dielectric crystals through electronic damage of multiple swift heavy ion irradiation.

First-principles investigation of vacancies in LiTaO3.

Formation energies of neutral and charged vacancies in lithium tantalate, as well as their electronic states have been investigated through first-principles calculations. It is found out that [Formula: see text], [Formula: see text] and [Formula: see text] are the most energy favorable vacancies on O, Li and Ta sites respectively. The formation energy of vacancy on the O site is lower in oxygen poor environments than that in oxygen rich environments, and the formation energy of vacancy on the cation site is lower in oxygen rich environments than that in oxygen poor environments. Among all types of neutral vacancies considered in this study, the energy of Li partial Schottky reaction, 2[Formula: see text] + [Formula: see text], is the lowest at almost all considered chemical environments. Taking into account the distribution of vacancy induced energy levels, we suggest that either [Formula: see text] or [Formula: see text] is responsible for the light absorption band around 460 nm observed in annealed LiTaO3 crystal.

Guided-wave second harmonics in Nd:YCOB optical waveguides for integrated green lasers.

We report on guided-wave second-harmonic generations in nonlinear Nd:YCa4O(BO3)3 (Nd:YCOB) optical waveguides that are produced by the low-fluence swift Ar8+ ion irradiation. The guided-wave second harmonics are realized through the frequency doubling and the self-frequency-doubling of the waveguides under the optical pumps at wavelengths of 1064 and 810 nm, respectively. By virtue of the self-frequency-conversion configuration, the Nd:YCOB waveguides are promising candidates as novel, compact, miniature green laser sources.

Efficient laser emissions at 1.06 µm of swift heavy ion irradiated Nd:YCOB waveguides.

We report on the fabrication of Nd:YCOB (Nd:YCa(4)O(BO(3))(3)) optical waveguides by using 170 MeVAr(8+) ion irradiation at an ultralow fluence of 2×10(12) ions/cm(2). The confocal microphotoluminescence investigation on the produced waveguides has shown the well-preserved fluorescence features within the guiding layer with respect to the bulks. Under the optical pump at wavelength of 810 nm, continuous wave waveguide lasers at 1061.2 nm have been generated at room temperature with a high slope efficiency of ~67.9%.

Continuous wave waveguide lasers of swift argon ion irradiated Nd:YVO4 waveguides.

We report on the fabrication of planar waveguide in Nd:YVO(4) crystal by using swift Ar(8+) ion irradiation. At room temperature continuous wave (cw) laser oscillation at wavelength of ~1067 nm has been realized through the optical pump at 808 nm with a low threshold of 9.3 mW. The slope efficiency of the waveguide laser system is of 8.5%. The optical-to-optical conversion efficiency is 6.6%.