The authors investigate the nonlinear and bistable behavior of a high-Q GaAs photonic crystal heterostructure nanocavity, side coupled to a line-defect slab waveguide. The observations agree well with a model incorporating the relevant nonlinearities. The power threshold for bistable behavior is at least one order of magnitude lower than what is reported so far.

International audienceThe authors realized an ultrahigh quality factor nanocavity in a GaAs membrane with the highest loaded Q reported to date of 250 000 in a side-coupled cavity-waveguide system. This result could be obtained using an original aluminum-free material system combined with a carefully adjusted fabrication technology, yielding a device with small roughness and very good verticality of holes as well as small disorder. The authors show that the intrinsic Q factor is around 3.0x105 using a coupled-mode model

A single-line-defect low-loss photonic crystal waveguide based on a perforated GaAs membrane in an aluminium-free material system is demonstrated. The GaInP lattice is matched to GaAs as the cladding/sacrificial layer. Fabry-Perot resonances are analyzed to obtain the group velocity dispersion for a 1-mm long guide. The losses are deduced to be close to 5 dB/cm, taking into account the wavelength dependent reflectivity of the guide extremities. In this framework, side-coupled nanocavities are also investigated. Feasibility of low-loss photonic-crystal-based devices combined with a reliable industrial material systems is thus demonstrated.

The authors propose highly resolved optical low-coherence reflectometry for investigating low-loss photonic crystal slab waveguides. This technique allows a fast, reliable, and straightforward measurement of the group delay and propagation losses for both TE and TM polarizations. The agreement with theory is very good. These measurements reveal effects related to structural disorder. The versatility and deep physical insight of this measurement technique will play a key role in the study of slow-light devices such as photonic crystal waveguides.

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