Hitomichi Takano

In-plane-type channel drop filter in a two-dimensional photonic crystal slab

An in-plane-type channel-drop filtering device with input/output waveguides and a point defect cavity in a two-dimensional photonic crystal slab is investigated. The in-plane operation becomes possible by employing a point defect cavity with an extremely high Q factor to suppress the radiation loss for the out-of-plane direction. 60° bends are also introduced in the output waveguide to avoid interference between the input/output waveguides. The transmission frequency range of the output waveguide with bends is tuned by changing the size of the air holes at the apex of the corner so that the resonant frequency of the point defect cavity is within the transmission band. A channel drop operation with a very high resolution of 0.12 nm is successfully observed at 1.55 μm wavelengths.

Highly efficient multi-channel drop filter in a two-dimensional hetero photonic crystal.

An in-plane, multi-channel drop filter with high efficiency, in a two-dimensional photonic crystal (PC) slab, is experimentally demonstrated. Based on the concept of heterostructure photonic crystals proposed previously, the device consists of multiple simply connected, PC-based filter units, in which each unit has a structure proportional to an optimized basic unit and operates at a different wavelength. Four-channel drop operation was successfully obtained, with high efficiencies of almost 100%, and equal quality factors, across all channels.

Highly efficient in-plane channel drop filter in a two-dimensional heterophotonic crystal

Improvements in the channel drop efficiency of an in-plane drop filter in a two-dimensional photonic crystal slab are presented, using a device consisting of two photonic crystal slabs with different lattice constants. It is theoretically shown that drop efficiencies much higher than the maximum of 25% for a conventional configuration are achievable when utilizing reflections at the photonic crystal heterostructure interface. Additionally, the higher drop efficiency is found to be less sensitive to structural fluctuations. Drop operations with efficiencies of more than 80% are experimentally demonstrated by the fabricated devices.

Two-dimensional photonic-crystal-slab channel-drop filter with flat-top response

We report a theoretical and experimental study of a channel drop filter with two cascaded point-defects between two line-defects in a two-dimensional photonic-crystal slab. Using coupled-mode analysis and a three-dimensional finite-difference time-domain method, we design a filter to engineer the line shape of the drop spectrum. A flat-top and sharp roll-off response is theoretically and experimentally achieved by the designed and fabricated filters. Furthermore, we theoretically demonstrate that drop efficiency is increased dramatically, up to 93%, by introducing hetero-photonic-crystals. We also describe a method to modify the bandwidth of the spectrum.

Highly effective in-plane channel-drop filters in two-dimensional heterostructure photonic-crystal slab

In-plane channel-drop filters consisting of point and line defects in a two-dimensional photonic-crystal slab are investigated. A clear channel-drop operation was successfully demonstrated by employing an ultrahigh quality factor nanocavity and a suitably designed waveguide bend. Moreover, improvements in the channel-drop efficiency of the device were made using a feature of heterostructure photonic crystals, as proposed previously. It is shown theoretically that drop efficiencies much higher than the maximum of 25% for a conventional configuration are achievable using reflection at the heterostructure interface. Drop operations with efficiencies of almost 100% were experimentally demonstrated by the fabricated devices. Moreover, a four-channel drop operation with a high drop efficiency and a constant quality factor was demonstrated by in-plane channel-drop filters in a two-dimensional photonic-crystal slab, with a simple configuration based on heterostructure photonic crystals.

Highly Efficient In-Plane-Type Channel Drop Filter in a Two-Dimensional Heterostructure Photonic Crystal

Improvements in channel-drop efficiency of an in-plane-type filter in a two-dimensional photonic crystal slab are presented. Drop operations with efficiencies of more than 80% are experimentally demonstrated.