Takeyoshi Tajiri

Circular dichroism in a three-dimensional semiconductor chiral photonic crystal

Circular dichroism covering the telecommunication band is experimentally demonstrated in a semiconductor-based three-dimensional chiral photonic crystal (PhC). We design a rotationally stacked woodpile PhC structure where neighboring layers are rotated by 60° and three layers construct a single helical unit. The mirror-asymmetric PhC made from GaAs with sub-micron periodicity is fabricated by a micro-manipulation technique. Due to the large contrast of refractive indices between GaAs and air, the experimentally obtained circular dichroism extends over a wide wavelength range, with the transmittance of right-handed circularly polarized incident light being 85% and that of left-handed light being 15% at a wavelength of 1.3 μm. The obtained results show good agreement with numerical simulations.

Demonstration of a three-dimensional photonic crystal nanocavity in a ⟨110⟩-layered diamond structure

We experimentally demonstrate a three-dimensional photonic crystal (3D PC) nanocavity in a ⟨110⟩-layered diamond structure with a quality factor (Q-factor) of 12 800 at a wavelength of 1.1 μm. The observed Q is 1.2 times higher than that of a 3D PC nanocavity in a woodpile structure with the same in-plane size and the same number of stacked layers. This result indicates the potential importance of the ⟨110⟩-layered diamond structure for getting high Q 3D PC nanocavities within a limited in-plane space.

Circularly polarized vacuum field in three-dimensional chiral photonic crystals probed by quantum dot emission

The quantum nature of light-matter interactions in a circularly polarized vacuum field was probed by spontaneous emission from quantum dots in three-dimensional chiral photonic crystals. Due to the circularly polarized eigenmodes along the helical axis in the GaAs-based mirror-asymmetric structures we studied, we observed highly circularly polarized emission from the quantum dots. Both spectroscopic and time-resolved measurements confirmed that the obtained circularly polarized light was influenced by a large difference in the photonic density of states between the orthogonal components of the circular polarization in the vacuum field.

High-Q nanocavities in semiconductor-based three-dimensional photonic crystals

We experimentally demonstrated high quality factors (Q-factors) of nanocavities in three-dimensional photonic crystals by increasing the in-plane area of the structure. Entire structures made of GaAs were fabricated by a micro-manipulation technique, and the nanocavities contained InAs self-assembled quantum dots that emitted near-infrared light. The obtained Q-factor was improved to 93,000, which is 2.4-times larger than that in a previous report of a three-dimensional photonic crystal nanocavity. Due to this large Q-factor, we successfully observed a lasing oscillation from this cavity mode.

Control of quantum dot light emission by chiral photonic crystal structures

Summary form only given. Photonic crystal (PhC) structures are good platform for solid-state quantum photonics. Efficient generation and guiding of single photons from semiconductor quantum dots (QDs) embedded in two dimensional (2D) PhC waveguides have been demonstrated recently. Various cavity quantum electrodynamics (CQED) phenomena have also been intensively explored in 2D PhC nanocavities coupled with a single QD. On the other hand, three-dimensional (3D) structures can provide other degrees of freedom for controlling photons and light-matter interaction. In this presentation, after a short review of our recent progresses on QD-CQED systems using 2D PhC nanocavities, we will discuss chiral 3D PhCs and its applications to control the light emission properties of QDs. Because of the chiral nature of the structure, chiral 3D PhCs enable to engineer the electromagnetic vacuum field for circularly polarized photons. This results in the generation of highly circularly polarized photons from QDs embedded in such chiral structures.

Control of Light Polarization using Photonic and Phononic Crystals

Photonic and phnonic crystals offer the possibilities of controlling light polarization efficiently. Here, we discuss giant optical rotation in a chiral photonic crystal and enhanced photoelastic modulation in a phononic crystal cavity.

Circularly polarized light emission of quantum dots at the band edge of three-dimensional chiral photonic crystals

We demonstrate highly circularly polarized emission from quantum dots in semiconductor chiral photonic crystals. The emission is influenced by the difference in density of states between the orthogonal circular polarizations at the polarization band edge.

Design of a three-dimensional photonic crystal nanocavity based on a -layered diamond structure

We design a novel three-dimensional (3D) photonic crystal (PC) nanocavity based on a <110>-layered diamond structure. The designed structure, comprised of self-sustainable layers, is suitable for fabrication by a layer stacking technique. Numerical simulations indicate that the quality factor of the designed nanocavity with 35 stacked layers can reach as high as 250,000. This value is 2.4 times higher than that of a conventional 3D PC nanocavity based on a woodpile structure with the same in-plane size and with the same number of