Control of the nonlinear carrier response time of AlGaAs photonic crystal waveguides by sample design

We have used reflection geometry pump-probe spectroscopy to investigate the free carrier response time of AlGaAs high refractive index contrast one-dimensional photonic crystal waveguides. We have observed pump-induced shifts of photonic resonances in the near infrared spectral region, and have studied the dependence of the decay time on the sample parameters. We find that the response time can be varied from 8to33ps by changing the structure period and etch depth. This, combined with the large changes observed in the reflectivity, demonstrates excellent potential for application as ultrafast photonic switches with a controllable recovery time.