Nanophotonic integrated lasers

The unique optical properties of photonic crystals allow a dense and simple integration of optical functionality on a small footprint. We have investigated the integration of tunable photonic crystal (PhC) lasers with a wavelength monitor. The small size of the monitor allows an integration on an all-active layer structure, which leads to a rather simple fabrication process. The tunable lasers are based on two coupled PhC waveguides with slightly different length. PhC mirrors are placed at the end, joint and front of the two waveguides. Tuning is achieved by a variation of the injection currents in the two segments. The wavelength monitor, which is placed behind the rear mirror of the laser, consists of a multi-mode PhC waveguide. Mode coupling between the fundamental mode and a higher order mode results in a wavelength-dependent transmission of the waveguide. In the region of the mode coupling, the higher order mode is extracted out of the waveguide through a sufficiently thin waveguide boundary. The power of the transmitted and extracted light is detected by two photodiodes, which are integrated with the wavelength monitor. The photocurrents of the these diodes show a clear dependence on the laser wavelength, in good agreement with simulations.