Structural and optical properties of RbTiOPO₄:Nb crystals

Abstract

When dealing with crystals showing self-frequency conversion properties, RbTiOPO4 doped with Nb5+ (RTP:Nb) is a better matrix than RTP for hosting luminescent ions in higher concentration. Therefore, we investigated the structural and the non-linear optical properties of RTP:Nb and RTP crystals for comparison. We used a new crystal growth process for RTP:Nb, which provides isometric inclusion- and crack-free crystals. Structural studies show that Nb5+ ions are located in Ti positions only, which is confirmed by optical absorption and polarized Raman scattering studies. Moreover, the transparency domain of RTP:Nb is affected in the UV edge and in the IR region by the presence of Nb5+ ions. Finally, we found that the fundamental wavelengths of type II angular non-critical phase-matching for second-harmonic generation along the x and y principal axes are smaller in RTP:Nb than in RTP, approaching those of KTP.

Femtosecond-Laser Microstructuring of Ribs on Active (Yb,Nb):RTP/RTP Planar Waveguides

“…Basically, the Raman spectra recorded correspond to those of RTP in a polarization configuration [27]. However, we observed significant differences in the intensity of the peaks located at and cm for the spectra recorded in the ablated and unablated areas, respectively.…”

“…For instance, the intensity of the peak at 976 cm is also reduced in the ablated areas. This peak corresponds to the vibration of PO tetrahedra [27] indicating that not only are modes related to the TiO group affected by the constraint on their vibrational degrees of freedom, but modes related to PO tetrahedra also are. In fact, the peaks related to Rb-O polar vibration [27] appearing at around 330 cm are also affected by the decrease in intensity depending on the polarization analyzed in the spectra, indicating that the whole structure of (Yb,Nb):RTP crystal is affected by the permanent induced stress generated by ultrafast laser ablation.…”

Lasers and optics: looking towards third generation gravitational wave detectors

“…Additional absorption bands are caused by overtones of vibrational modes in the XO 4 tetrahedra starting above 3 µm [32]. The UV-absorption edge of all crystals within the MTiOXO 4 family is near 350 nm [32]. Similar to LiNbO 3 , the largest electro-optical coefficient in all MTiOXO 4 crystals is r 33 .…”

“…The first absorption band is typically around λ = 2.8 µm, likely caused by ionized O − H-molecules inside the crystal. Additional absorption bands are caused by overtones of vibrational modes in the XO 4 tetrahedra starting above 3 µm [32]. The UV-absorption edge of all crystals within the MTiOXO 4 family is near 350 nm [32].…”

Parallel phase modulation scheme for interferometric gravitational-wave detectors

“…We used Rubidium Titanyl Phosphate (RTP) crystals obtained from Raicol [18], with the same dimensions and material as the electro-optic crystals used in aLIGO. The Sellmeier coefficients for the index of refraction have been measured for RTP [19] to give an index of refraction n 0z = 1.8580 at 1064 nm. The electro-optic coefficient r 33 has been measured in the range from 520 to 930 nm [20]; using these fitted Sellmeier coefficients gives an EO coefficient of r 33 = 34.35 pm V at 1064 nm.…”