40-wavelength rapidly digitally tunable laser

We present a tunable laser based on an N/sub 1//spl times/N/sub 2/ chirped waveguide grating router that has N/sub 1/N/sub 2/ wavelengths, accessible in a digitally rapid manner, and only N/sub 1/+N/sub 2/+1 semiconductor optical amplifiers. By using chirp, the free-spectral range of the router can be significantly less than the channel span. The version demonstrated here has N/sub 1/=5, N/sub 2/=8, a channel spacing of 100 GHz, and the router free-spectral range is only 20 channels.