A new way to reduce the critical power of the bistable behavior in nonlinear optical waveguides is presented. This is achieved by embedding circular photonic crystals (PCs), satisfying the Bragg condition, along a channel waveguide. Three different schemes are anaylzed: PCs in the core region only. PCs in the cladding region only, and a partial fulfillment of the core with PCs. All cases presented a decreasing of the critical or threshold power. Our numerical simulations, using the finite-element method, show the possibility to reduce up to three times the critical power, as compared to a conventional nonlinear channel waveguide. Threshold powers as low as 30 muW can be achieved. (C) 2004 Wiley Periodicals. Inc.4114043