Chalcogenide glass photonic crystals

All-optical switching devices are based on a material possessing a nonlinear optical response, enabling light to control light, and are enjoying renewed interest. Photonic crystals are a promising platform for realizing compact all-optical switches operating at very low power and integrated on an optical integrated circuit. In this review, we show that by making photonic crystals from a highly nonlinear chalcogenide glass, we have the potential to integrate a variety of active devices into a photonic chip. We describe the fabrication and testing of two-dimensional Ge₃₃As₁₂ Se₅₅ chalcogenide glass photonic crystal membrane devices (waveguides and microcavities). We then demonstrate the ability to post-tune the devices using the material photosensitivity. In one proposal we hope to introduce a double-heterostructure microcavity using the photosensitivity alone.     

High-Q cavities in photosensitive photonic crystals

We propose a novel concept for creating high-Q cavities in photonic crystal slabs (PCSs) composed of photosensitive material. To date, high-Q cavities have been realized through the use of double heterostructures where the lattice geometry is altered via nanolithography. Here, we show that selective postexposure to light of a uniform PCS composed of photosensitive material, altering the refractive index permanently, can also yield high-Q microcavities. We show theoretically that high-Q cavities (up to Q = 1 x 10(6)) can be achieved with photoinduced index changes that are well within what can be achieved in chalcogenide glasses.     

New design for a variable optical attenuator based on a bent channel waveguide

We present a new method for bend loss control in a curved channel optical waveguide and employ it in a novel design of a thermo-optic variable optical attenuator. We show that the introduced asymmetric refractive index profile of the waveguide structure, combined with the optimal placement of the heating electrodes, leads to a significant increase of the dynamic range of the attenuator. PACS 42.82.Et; 42.70.Jk; 42.79.Ta     

Analysis of bend loss in waveguides employing photonic band gap effect

We analyse bend loss properties of a band gap-guided periodic structure, and give reasons for the effects found. In many cases, a tight bend produces only a slight reduction in power transmitted. We also make a comparison of bend losses in conventional waveguides and bend-resistant waveguides.     

Packing density of conventional waveguides and photonic crystal waveguides

We compare coupling between parallel waveguides within one-dimensional photonic crystals and coupling between conventional waveguides. We consider the situation in which coupling between the waveguides is minimized, so that light in the waveguides propagates essentially independently. Subject to this condition, we compare the minimum mutual distance between conventional planar waveguides and waveguides in one-dimensional photonic crystals. We find that the packing densities of the conventional and periodic structures are comparable.     

High-Q microfluidic cavities in silicon-based two-dimensional photonic crystal structures

We demonstrate postprocessed microfluidic double-heterostructure cavities in silicon-based photonic crystal slab waveguides. The cavity structure is realized by selective fluid infiltration of air holes using a glass microtip, resulting in a local change of the average refractive index of the photonic crystal. The microcavities are probed by evanescent coupling from a silica nanowire. An intrinsic quality factor of 57,000 has been derived from our measurements, representing what we believe to be the largest value observed in microfluidic photonic crystal cavities to date.