Difference Frequency Generation from Integrated Nonlinearities in Two-Wavelength Quantum Cascade Lasers

Evidence for Difference Frequency Generation in Quantum Cascade Lasers with integrated nonlinearities is presented. Light at the difference frequency (lambda = 13.3mum) is detected from a two-wavelength (lambda = 5.3mum and 8.8mum) laser processed with a split-ridge configuration.