Stability and Bandwidth Enhancement of Difference Frequency Generation Based Wavelength Conversion by Pump Detuning

Difference frequency generation (DFG) is an attractive method for wavelength conversion in wavelength division multiplexed (WDM) optical networks. DFG-based devices have been demonstrated successfully in quasi-phasematched (QPM) AlGaAs sup 2 and LiNbO sub 3 sup (3,4) waveguides. Although such process has a wide signal conversion bandwidth (~ 60-90 nm), the pump bandwidth is in general narrow (~ 0.1 nm). Traditionally, the pump is chosen to operate at the degenerate phasematching wavelength, where lambda out = lambda signal, 0 and lambda pump, 0 = lambda signal, 0/2. (lambda out, lambda signal, lambda pump are pump, input signal and converted wavelengths, respectively; subscript 0 denotes degeneracy). However, under these circumstances, the conversion efficiency and its bandwidth will be sensitive to drifts in device temperature or in the pump wavelength. In this paper, we address and solve this instability problem by detuning the pump from the degenerate phasematching wavelength We also discuss the possibility of further enhancing the device stability and bandwidth using nonuniform QPM structures.