Dao-Yin Yu

Refractive Index Profile in Photorefractive-Damage-Resistant Near-Stoichiometric Ti:Mg:Er:

Refractive index profile in photorefractive-damage-resistant near-stoichiometric (NS) single-mode Ti:Mg:Er: <formula formulatype=inline><tex Notation=TeX>

\hbox{LiNbO}_{3}

hbox{LiNbO}_{3}

Strip Waveguide

</tex></formula> strip waveguide is constructed from the measured mode field distribution. Like the conventional congruent Ti:<formula formulatype=inline><tex Notation=TeX>

Relation of Refractive Index to Ti-Concentration in Near-Stoichiometric

hbox{LiNbO}_{3}

{\rm Ti{:}LiNbO}_{3}

</tex></formula> waveguide, the Ti-induced refractive index increase in the NS waveguide studied here follows a sum of two error functions in the width direction and a Gaussian function in the depth direction. Based upon the established index profile model, the mode sizes were calculated using the variational method and compared with the experimental results. The Ti-induced index increment at the NS waveguide surface was also evaluated according to the empirical relation previously reported for the conventional congruent Ti: <formula formulatype=inline><tex Notation=TeX>

Waveguide

hbox{LiNbO}_{3}

Emission and Absorption Cross Sections of Photorefractive-Damage-Resistant Locally Er-Mg-Doped Near-Stoichiometric

</tex></formula> waveguide and compared with the data deduced from the mode field distribution. All comparisons show good agreement, showing that the index model proposed is close to the practical scenario.

{\rm Ti}:{\rm Mg}:{\rm Er}:{\rm LiNbO}_{3}

Multi-mode near-stoichiometric (NS) Ti:LiNbO3 planar waveguide was fabricated by co-work of Li-rich vapor transport equilibration and in-diffusion of Ti-film on an initially congruent LiNbO3 substrate. The Ti-concentration is profiled by secondary ion mass spectrometry. The refractive index profile is constructed from measured mode indices and correlated with the Ti-concentration profile. The results show that the index change and Ti-concentration follow an exponential relationship with a power index 0.75/0.49 for the ordinary/extraordinary ray. The relationship is different from that of either conventional congruent waveguide or homogeneously Ti-doped NS bulk material or NS waveguide fabricated by direct Ti-diffusion in an NS substrate.

Strip Waveguides

We have measured the polarized visible and near-infrared, and unpolarized mid-infrared (2.7 μm) emission spectra of photorefractive-damage-resistant locally Er-Mg-doped near-stoichiometric (NS) Ti:Mg:Er:LiNbO3 strip waveguide, fabricated on an X-cut initially congruent LiNbO3 substrate in sequence by local Er doping in air, Mg-Ti pre-diffusion in wet O2 and post Li-rich vapor transport equilibration treatment. From the measured emission spectra, the emission and absorption cross section spectra were calculated based upon McCumber theory. The spectroscopic features are discussed in comparison with the spectra recorded from the area outside the waveguide, and with the previously reported results of bulk-doped NS Er:Mg:LiNbO3 crystals and congruent Er:LiNbO3 bulk material or Ti:Er:LiNbO3 waveguide structure. The results show that the spectra of the NS waveguide are traditional and reveal small differences from those spectra outside the waveguide in spectral shape, polarization dependence, as well as cross section values. In contrast, the cross section values of the NS waveguide show considerable differences from those of bulk-doped NS material and congruent bulk material or waveguide structure. The 552, 673, 996, and 1531 nm emission lifetimes of the Er3+ ions outside the waveguide were also measured, and found to be comparable to the results of the bulk-doped NS crystal and the congruent bulk material or waveguide structure.

Optical-Damage-Resistant Ti-Diffused LiNbO 3 Strip Waveguide Doped With Scandium

We report Sc3+-doped Ti:LiNbO3 (Ti:Sc:LN) strip waveguide fabricated by Ti-diffusion following homogeneous Sc3+-diffusion-doping in a Z-cut congruent substrate. We show that Sc3+-doping has little contribution to the substrate index and the Li2O out-diffusion was effectively suppressed. The refractive index increases in the waveguide layer are mainly contributed from the Ti4+ dopants. The waveguide well supports both transverse electric (TE) and magnetic (TM) modes, is single-mode at 1.5-μm wavelength, and has a loss of 1.4 dB/cm for the TE mode and 1.8 dB/cm for the TM mode. A secondary ion mass spectrometry study shows that the Sc3+-profile covers 80% ordinary refractive index profile and almost 100% extraordinary refractive index profile, and the 1/e Sc3+ concentration is above the threshold of photorefractive effect. Further, two-beam hologram recording experimental results verify the optical-damage-resistant feature of the waveguide. Highlights are given for fabrication of an optical-damage-resistant Ti:Sc:LN waveguide.