Snjezana Tomljenovic-Hanic

Diamond based photonic crystal microcavities.

Diamond based technologies offer a material platform for the implementation of qubits for quantum computing. The photonic crystal architecture provides the route for a scalable and controllable implementation of high quality factor (Q) nanocavities, operating in the strong coupling regime for cavity quantum electrodynamics. Here we compute the photonic band structures and quality factors of microcavities in photonic crystal slabs in diamond, and compare the results with those of the more commonly-used silicon platform. We find that, in spite of the lower index contrast, diamond based photonic crystal microcavities can exhibit quality factors of Q=3.0x10(4), sufficient for proof of principle demonstrations in the quantum regime.

Design of high-Q cavities in photonic crystal slab heterostructures by air-holes infiltration

We design novel photonic crystal slab heterostructures, substituting the air in the holes with materials of refractive index higher than n=1. This can be achieved by infiltrating the photonic crystal slab (PCS) with liquid crystal, polymer or nano-porous silica. We find that the heterostructures designed in this way can have quality factors up to Q=10(6). This high-Q result is comparable with the result of previously reported designs in which the lattice is elongated in one direction. Unlike conventional heterostructures, our design does not require nanometre-scale changes in the geometry. Additionally, infiltrated PCS can be constructed at any time after PCS fabrication.

Microfluidic photonic crystal double heterostructures

The support of the Australian Research Council through its Federation Fellow, Centres of Excellence, Denison Foundation, and Discovery Grant programs is gratefully acknowledged.

Reconfigurable microfluidic photonic crystal slab cavities

We demonstrate the spectral and spatial reconfigurability of photonic crystal double-heterostructure cavities in silicon by microfluidic infiltration of selected air holes. The lengths of the microfluidic cavities are changed by adjusting the region of infiltrated holes in steps of several microns. We systematically investigate the spectral signature of these cavities, showing high Q-factor resonances for a broad range of cavity lengths. The fluid can be removed by immersing the device in toluene, offering complete reconfigurability. Our cavity writing technique allows for tolerances in the infiltration process and provides flexibility as it can be employed at any time after photonic crystal fabrication.

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.

Diamond in tellurite glass: a new medium for quantum information.

M. R. Henderson, B. C. Gibson, H. Ebendorff-Heidepriem, K. Kuan , S. Afshar V., J. O. Orwa, I. Aharonovich ,S. Tomljenovic-Hanic, A. D. Greentree, S. Prawer, and T. M. Monro

Flexible design of ultrahigh-Q microcavities in diamond-based photonic crystal slabs.

We design extremely flexible ultrahigh-Q diamond-based double-heterostructure photonic crystal slab cavities by modifying the refractive index of the diamond. The refractive index changes needed for ultrahigh-Q cavities with Q approximately 10(7), are well within what can be achieved (Delta n approximately 0.02). The cavity modes have relatively small volumes V<2 (lambda/n)(3), making them ideal for cavity quantum electro-dynamic applications. Importantly for realistic fabrication, our design is flexible because the range of parameters, cavity length and the index changes, that enables an ultrahigh-Q is quite broad. Furthermore as the index modification is post-processed, an efficient technique to generate cavities around defect centres is achievable, improving prospects for defect-tolerant quantum architectures.

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.

Temperature stabilization of optofluidic photonic crystal cavities

We present a principle for the temperature stabilization of photonic crystal (PhC) cavities based on optofluidics. We introduce an analytic method enabling a specific mode of a cavity to be made wavelength insensitive to changes in ambient temperature. Using this analysis, we experimentally demonstrate a PhC cavity with a quality factor of Q≈15 000 that exhibits a temperature-independent resonance. Temperature-stable cavities constitute a major building block in the development of a large suite of applications from high-sensitivity sensor systems for chemical and biomedical applications to microlasers, optical filters, and switches.

Photowritten high-Q cavities in two-dimensional chalcogenide glass photonic crystals

We demonstrate a high-Q(approximately 125,000) photonic crystal (PhC) cavity formed using a postprocessing optical exposure technique where the refractive index of a photosensitive chalcogenide PhC is modified locally. The evolution of the cavity resonances was monitored in situ during writing using a tapered fiber evanescent coupling system, and the Q of 125,000 represents 1 order of magnitude increase over previously reported cavities in two-dimensional chalcogenide glass PhC.