M.J. Li

Nd:MgO:LiNbO 3 waveguide laser and amplifier

We report efficient operation of a channel waveguide laser and a channel waveguide amplifier in Nd:MgO:LiNbO(3). For the laser a cw output power of 2.9 mW was obtained for 23.6 mW of absorbed pump power. The absorbed pump power at threshold was 1.5 mW, and a slope efficiency of 13% was achieved. For the amplifier a small-signal gain of 7.5 dB was achieved for 22 mW of coupled pump power.

Nd:MgO:LiNbO/sub 3/ channel waveguide laser devices

A report is presented on the fabrication and efficient CW operation at 1.085 mu m of Nd:MgO:LiNbO/sub 3/ proton-exchanged channel waveguide lasers and amplifiers optically pumped at 0.814 mu m. Thresholds as low as 1.5 mW and slope efficiencies up to 34% were achieved in monolithic miniature laser devices. Up to 14 mW of output power could be achieved without observation of photorefractive damage. Diode laser pumping was also demonstrated. For the amplifier a small-signal gain of 7.5 dB was achieved for 22 mW of coupled pump power. Experimental results were analyzed with the use of a mode overlap formalism and a value of 0.93 was found for the pump quantum efficiency. Absorption spectra, fluorescence spectra, and lifetime measurements are also reported for the bulk and waveguide material. >

Cerenkov configuration second harmonic generation in proton-exchanged lithium niobate guides

A theoretical and experimental study of second-harmonic generation using the Cerenkov configuration with proton-exchanged lithium niobate guides is presented. The analytic solution of the problem for the case of planar step-index guides makes it possible to identify the essential role played by the discontinuity of the nonlinear polarization at the guide-substrate interface. This leads to the prediction of an increasing conversion efficiency for decreasing values of guide nonlinearity. It is shown that the experimental results are consistent with a reduction of 50 to 70% of the value of the nonlinear coefficient in unannealed waveguides fabricated in slightly diluted or pure benzoic acid. The results presented permit the optimization of guide design for efficient second-harmonic generation in the Cerenkov configuration. >

High index low loss LiNbO3 waveguides

Abstract We report the first fabrication, by a double proton exchange process (Double Exchange, DE) of planar LiNbO3 waveguides simultaneously presenting high index modifications (δne=0.11 at a wavelength of 632.8 nm) and losses as low as 0.4 dB/cm at the same wavelength. We also demonstrate the possibility of superimposing the DE process with titanium indiffusion (Titanium Indiffusion Double Exchange, TIDE) in order to realise high quality guides supporting both TE and TM modes, useful in phase-matched applications.

Fabrication and characterisation of PE waveguides presenting a low index increase and a very good optical quality

Presents a new type of proton exchange, which allows the realisation of LiNbO3 waveguides with, for extraordinarily polarised light, an index profile similar to that of titanium indiffused guides, but of a better optical quality.

Towards A Laser Diode Pumped Nd:LiNbO3 Waveguide Laser

Laser properties of Nd:LiNb03 were investigated and low loss proton exchange planar optical waveguides were fabricated in this material. Nd3+ spectroscopic properties were found to be unchanged indicating that the realization of a diode pumped Nd:LiNb03 waveguide laser should be possible.

Cerenkov Configuration Second Harmonic Generation

The use of the largest nonlinear coefficient d33 of LiNbO3 for second harmonic generation (SHG), first demonstrated with a guided wave phase-matched interaction suffering from poor field overlap integrals (1), has been considerably improved by the use of a Cerenkov type configuration : nonlinear polarization having a phase velocity greater than that of light in the waveguide, harmonic radiated into the substrate (2,3). The excellent results obtained by T. Taniuchi and K. Yamamoto (1) demonstrate the interest of second harmonic generation (SHG) in the form of Cerenkov radiation (2) In the first part of this paper, we present a new calculation of the efficiency of this process in step index waveguides. In the second part, the validity of this model is checked by studying second harmonic Cerenkov radiation in planar step index waveguides realized by proton exchange (PE) (5) in LiNbO3. The comparison of computed and measured efficiencies show a good relative agreement for multimode waveguides using the usual value of the non-linear coefficient in the exchanged region.