Search

We report optical-damage-resistant Ti:Er:LiNbO3 strip waveguide with high diffusion-doped surface Er^3+ concentration. The waveguide was fabricated starting from a commercial X-cut congruent LiNbO 3 plate with a two-step technological process in sequence of simultaneous work of Er^3+ diffusion doping and Li-poor vapor transport equilibration treatment, and fabrication of 6-μm-wide Ti-diffused strip waveguide (Z-propagation). The waveguide retains still the LiNbO3 phase and has the waveguiding characteristics similar to the conventional Ti:LiNbO3 waveguide except with a larger loss due to the imperfection of waveguide. Secondary ion mass spectrometry study shows that the Er^3+ diffusion reservoir was exhausted and the profile is the desired Gaussian-type with a surface concentration 1.0 mol%, which is about two times larger than the value of conventional Ti:Er:LiNbO3 amplifier. Further optical characterization shows that the waveguide shows stable 1547 nm small-signal gain under the 980 nm pumping without serious photorefractive effect observed. An unsaturated gain 1.7 dB/cm is obtained for the available coupled pump power of 160 mW. With increased pump power, optimized Er ^3+ diffusion condition and degraded loss figure, a higher gain is expected. [ABSTRACT FROM PUBLISHER]

Refractive index in special optical-damage-resistant MgO-diffused near-stoichiometric (NS) Ti:LiNbO3 (Ti:LN) waveguide structure that a number of single-mode strip waveguides are embedded in a planar waveguide is profiled on the basis of the measured mode field profile of strip waveguide. In the NS strip waveguide, the Ti^4 +-induced extraordinary index increase studied follows a sum of two error functions in the width direction and a sum of two Gaussian functions in the depth direction. In the NS planar waveguide, the index increase follows a Gaussian function. On the basis of the established index profile model, the mode field profiles were calculated using variational method and compared with the measured data. The results show that the calculated mode sizes are in good agreement with the measured. In addition, the profile characteristics of Ti^4 +-concentration in both the strip and planar waveguides were analyzed by secondary ion mass spectrometry and are correlated with the refractive index increase. The result shows that the profile characteristics of the index increase and Ti^4 +-concentration are similar for both the strip and planar waveguides and there exists a linear relationship with a slope of \sim2.0\,\times\,10^- 3(mol\\%)^- 1. [ABSTRACT FROM PUBLISHER]

We have measured the polarized visible and near-infrared, and unpolarized mid-infrared (2.7 \mum) 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 Er^3+ 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. [ABSTRACT FROM PUBLISHER]

We report that the polarization property of \Er^3+ transition in \LiNbO3 waveguide or bulk material is closely related to the incident direction of excitation beam relative to the optical axis of the crystal. It is found that the 1.5-\mu\m transition is highly \sigma- (\pi-) polarized as the excitation direction is perpendicular (parallel) to the optical axis, and the 0.67-\mu\m transition reveals a reversed effect. Incident perpendicularly (parallel), the transition is highly \pi- (\sigma-) polarized. The effect is found to be independent of the polarization state and wavelength of the excitation light. It is attributed to the selective Er site excitation. [ABSTRACT FROM PUBLISHER]

A special structure of a strip Ti : \LiNbO3 waveguide embedded in a planar Ti : \LiNbO3 waveguide is proposed to fabricate a long-period waveguide grating (LPWG). Its applicability is demonstrated by fabricating a long-period grating on the waveguide surface using usual photoresist. We show that an LPWG device based on such a special structure is thermally stable. [ABSTRACT FROM PUBLISHER]