Masamitsu Mochizuki

Surface-emitting channel drop filters using single defects in two-dimensional photonic crystal slabs

We report a theoretical analysis of trapping and emission of photons by a single defect in a two-dimensional photonic crystal slab. We show that the tuning of emission wavelength is possible by selecting appropriate geometry of structure while keeping the emission efficiency maximal. The results suggest the possibility of applying it to ultra-small channel add/drop device in wavelength division multiplexed optical communications.

Design of a channel drop filter by using a donor-type cavity with high-quality factor in a two-dimensional photonic crystal slab

We report a design of the surface-emitting-type channel drop filters based on point defect cavities and line defect waveguides in two-dimensional photonic crystal slabs, which aim to improve the filtering resolution and light emission characteristics. Since the filters are passive, the mode volume size of the defects needs not be minimized, but the interaction between the defect cavity and the line defect waveguide must be considered. By adopting a donor-type point defect with three missing holes of linear shape, the quality factor of the filter theoretically increases to values as high as 2900 while it reached only 500 in the previously utilized acceptor-type defect. The results suggest that this donor-type defect is very useful for the development of ultrasmall channel add/drop devices.

Channel drop filter using a single defect in a 2-D photonic crystal slab waveguide

This paper describes a theoretical and experimental analysis of the channel drop filter using a single defect formed near the two-dimensional (2-D) photonic crystal slab waveguide. First, we calculate the transmission spectrum of a 2-D photonic crystal waveguide and show that high transmittance for a wide wavelength range (/spl sim/60 nm) is obtained in the 1.55-/spl mu/m region. We also show that a defect state having a wavelength within the high transmission wavelength range can be formed in the photonic bandgap by introducing a single defect of appropriate radius. Next, we fabricate several devices and show that the emission wavelength from each defect can be tuned by changing the defect radius. The measured tuning characteristics coincide well with the calculated results. From the near-field pattern of the device, we estimate the emission efficiency of the present device at almost a few tens percent. We clarify the structural condition in order to obtain the maximum output efficiency and show that tuning of emission wavelength while maintaining high output efficiency is possible by selecting appropriate defect radius and position. Based on these results, we propose an ultrasmall channel drop filter for a wavelength-division-multiplex optical communication system.

Semiconductor three-dimensional and two-dimensional photonic crystals and devices

Semiconductor three-dimensional (3-D) and two-dimensional (2-D) photonic crystals and their effects on the control of photons are investigated for possible applications to optical chip and functional devices. First we review our approaches creating full 3-D photonic bandgap crystals at near-infrared wavelengths, and also functional devices based on 2-D photonic crystals where the focus is on surface-emitting-type channel-drop filtering devices utilizing single defects in 2-D photonic crystal slabs. Then, we describe the recent progress on 3- and 2-D crystals. On 3-D crystals, the effect of the introduction of a light emitter into the 3-D photonic crystal is investigated, and the design of a single defect cavity is performed. On the 2-D photonic crystals, the photonic states are investigated from the perspective of their polarization properties.

Analysis of coupling between two-dimensional photonic crystal waveguide and external waveguide

Coupling between conventional wire waveguide and two-dimensional photonic crystal waveguide was analyzed by means of a three-dimensional finite difference time domain method. We evaluated the transmittance corresponding to the coupling efficiency between two waveguides. By using SiO2 clad below the wire and setting the width of the wire to be an appropriate value, we obtained single mode guiding and a coupling efficiency over 80% for the wave length around 1.55 μm.

A channel drop filter using a single defect in a 2-D photonic crystal slab-defect engineering with respect to polarization mode and ratio of emissions from upper and lower sides

A detailed theoretical analysis of defect engineering in a channel drop filter consisting of a single point defect near a waveguide in a two-dimensional (2-D) photonic crystal (PC) slab is presented. Initially, engineering of the point defect to control the polarization modes of emitted light is examined. By introducing an elliptical defect laterally shifted from the PC lattice, a single linearly polarized light mode can be selected to emit the majority of light, whereas light emitted from the original circular defect is made up of a range of linearly polarized modes. It is also shown that the ratio of light emitted from the top and bottom side of the defect can be improved considerably by introducing a defect with a stepped section along the vertical axis, thereby increasing the net efficiency of the device.

Theoretical analysis of trapping and emission of photons by a single defect in a 2D photonic crystal slab

Trapping and emission of photons by a single defect in a 2D photonic crystal slab is analyzed. We show that the tuning of emission wavelength is possible by selecting appropriate geometry of structure while keeping the high emission efficiency.

Optical Properties of a Single Defect in 2D Photonic Crystal Slab For Possible Application to Ultrasmall Channel Drop Filter

We investigate the optical properties of a single defect in 2D photonic crystal slab, which can be potentially applied to ultrasmall surface-emitting-type channel drop filter. It is shown that the frequency and polarization of the dropped light can be controlled by changing the size and/or shape of the defect.