Chongjun Jin

Optical properties of tetragonal photonic crystal synthesized via template-assisted self-assembly

A (001) oriented three-dimensionally periodic photonic crystal, free of cracks, has been fabricated via a modified template-assisted colloidal self-assembly method with polystyrene spheres. Analysis of the opal-type crystals has revealed the structure to be noncubic. This is a face-centered tetragonal (fct), (001) oriented photonic crystal. The optical properties of the crystals have been characterized at near-normal incidence by reflectance spectroscopy. It is found that the photonic stop band shifts to shorter wavelengths compared with an identical cubic structure oriented along the (001) direction. We have also simulated the stop band behavior of such fct crystals and their inverse silicon analogs, revealing that the polymer opal could provide an inverse template for the formation of photonic crystals with a complete band gap.

Photonic crystal and photonic wire nano-photonics based on silicon-on-insulator

Silicon-on-insulator (SOI) is a strong candidate for application in future planar waveguide integration technology, whether or not luminescence is extracted from the silicon. We review recent research on photonic devices based on silicon-on-insulator. These devices exploit either photonic crystal or photonic wire concepts—or combinations of both. Aspects of the technologies used that are particularly critical for successful implementation of SOI-based photonics are addressed.

Transmission of photonic crystal coupled-resonator waveguide (PhCCRW) structure enhanced via mode matching

A method for increasing the coupling efficiency between ridge optical waveguides and PhCCRWs is described. This increase is achieved via W1 channel waveguide sections, formed within a two-dimensional triangular lattice photonic crystal using mode-matching. The mode-matching is achieved by low quality-factor modified cavities added to both the input and output ports of the PhCCRW. A three dimensional finite-difference time-domain method has been used to simulate light propagation through the modified PhCCRW. We have fabricated PhCCRWs working at 1.5microm in silicon-on-insulator material. Measurements and simulations show that the overall transmission is improved by a factor of two.

Increasing optical metamaterials functionality

Gold Split Ring Resonators (SRRs) were fabricated on silicon substrates by electron beam lithography and lift-off, with overall dimensions of approximately 200 nm. Reflectance spectra from the SRRs are similar to those published elsewhere. New devices are proposed based on the additional functionality afforded by the use of a silicon substrate.

Template-assisted self-assembly growth of [100] oriented three-dimensional photonic crystal

A (100) oriented three-dimensional photonic crystal with more than 10 layers of spheres has been fabricated by using template-assisted convective self-assembly method

Photonic crystal and photonic wire device structures

Photonic devices that exploit photonic crystal (PhC) principles in a planar environment continue to provide a fertile field of research. 2D PhC based channel waveguides can provide both strong confinement and controlled dispersion behaviour. In conjunction with, for instance, various electro-optic, thermo-optic and other effects, a range of device functionality is accessible in very compact PhC channel-guide devices that offer the potential for high-density integration. Low enough propagation losses are now being obtained with photonic crystal channel-guide structures that their use in real applications has become plausible. Photonic wires (PhWs) can also provide strong confinement and low propagation losses. Bragg-gratings imposed on photonic wires can provide dispersion and frequency selection in device structures that are intrinsically simpler than 2D PhC channel guides--and can compete with them under realistic conditions.

Nanophotonic structures: from photonic crystals to metamaterials

We present a summary of our work concerned with nanophotonic structures-covering fabrication and measurement of 3-D (100) oriented photonic crystals; 2-D coupled-cavity resonators waveguides with enhanced transmission resulting from adjusted cavity matching; 1-D photonic wire waveguides based on silicon-on-insulator, with tapered Bragg gratings-and metamaterials based on arrays of split-ring resonators with polarisation dependent resonances in the visible range.

Enhanced transmission of photonic crystal coupled-resonator waveguide structure via mode matching

A mode matching method is proposed to improve the coupling efficiency between a photonic crystal coupled-resonator waveguide and a ridge waveguide. It has been demonstrated that the coupling efficiency can be improved by as much as a factor of three

Semiconductor-based active and passive nanophotonics

Nano-structured semiconductors will play a vital role in future photonics, providing efficient localised photon generation and various other functions for communications, sensing, imaging and display applications. We shall provide several illustrative examples of possibilities.