Optical parametric amplification of a 1.54-μm single-mode DFB laser in a Ti:LiNbO3 waveguide

Optical parametric amplification of radiation from a 1.54-μm single-mode DFB laser in a Ti:LiNbO₃ waveguide has been investigated by measuring the idler created in the nonlinear process. The pump was a frequency-doubled Nd:YAG laser at 532-nm wavelength, operated either Q-switched or both Q-switched and mode-locked to avoid permanent surface damage and to minimize photorefractive index changes. On comparison with theoretical predictions, the output was found to correspond to a pump power one order of magnitude below the true power in the waveguide. The highest gain obtained was 4.7 dB with 49 W of pump power in a 27-mm-long waveguide. Although the experimental results can be improved, it is obvious that the major difficulty to overcome is the large pump power required. The prospect of decreasing the power requirement by using materials with higher effective nonlinear coefficients or by using quasi-phase-matching techniques is discussed. A more fundamental drawback is that the amplification is polarization dependent, and it is unclear how this can be handled