Dai Ohnishi

Room temperature continuous wave operation of a surface-emitting two-dimensional photonic crystal diode laser

We achieved room temperature continuous wave operation of a surface-emitting two-dimensional photonic crystal diode laser by current injection. This is the first time ever that room temperature continuous wave operation of a photonic crystal diode laser has been realized. This laser features single mode oscillation over a large area, which is impossible for conventional lasers. In this work, we optimized the epitaxial layer composition for better carrier confinement and clarified the relationship between the diameter of the air holes in the photonic crystal and the threshold current of the laser in order to estimate the optimized threshold current.

Lasing band-edge identification for a surface-emitting photonic crystal laser

The possibility of single-mode oscillation over a large cavity area for photonic crystal lasers emitting at the photonic band edge has resulted in much interest in such materials for new forms of solid-state laser. In this paper, we measure the photonic bandstructure in our sample and identify the lasing band edge. By mapping out the bandstructure at the /spl Gamma/-point, we have observed fine structure at the band edge. The experimental results are in good agreement with the theoretically predicted bandstructure. Above threshold, we observe a lasing peak at 965 nm at one of the band edges. The far-field distribution of the laser is measured, showing an annular profile and azimuthal polarization. Calculations on the far-field distribution at the lasing band edge suggest the annular profile is due to an anti-symmetric resonant mode.

Refractive index sensor based on hybrid coupler with short-range surface plasmon polariton and dielectric waveguide

An integrated sensor based on a vertical hybrid coupler composed of a short-range surface plasmon polariton (SRSPP) waveguide and a SiNx dielectric waveguide has been realized. The output power of the sensor is observed to change drastically with the refractive index of the detection liquid, and the sensing region can be adjusted by varying the width of the SiNx waveguide. The resolution is estimated to be as high as 7.3 × 10−6 refractive index units. This sensor is expected to have significantly high effective sensitivity for detecting a hundred-nanometer-thick layer owing to the highly bounded field of the SRSPP mode.

Extremely high efficient coupling between long range surface plasmon polariton and dielectric waveguide mode

To connect the surface plasmon polariton (SPP) based devices with the conventional dielectric devices is a significant issue for the further development of SPP and related applications. In this paper, extremely high efficient coupling (>99%) between long range SPP (LRSPP) waveguide mode and TM mode of dielectric waveguide has been demonstrated from a hybrid coupler, which composed of an Au (LRSPP) waveguide and a SiN (dielectric) waveguide. Based on this hybrid coupler, a polarization splitter with pure TM mode output from one arm and TE mode output from the other arm with high TE/TM extinction ratio has been realized.

Excitation of short range surface plasmon polariton mode based on integrated hybrid coupler

The excitation method of short range surface plasmon polariton mode with hybrid coupler structure is analyzed numerically.

High-power single-lobed surface-emitting photonic-crystal laser

High-power (46 mW), single-lobed, surface-emitting operation is successfully achieved in a 2D photonic-crystal laser by optimizing the structure of the lattice points, under room temperature, continuous-wave conditions.

Inhibition of multipolar plasmon excitation in periodic chains of gold nanoblocks

Periodically corrugated chains of gold nanoblocks, fabricated with high precision by electron-beam lithography and lift-off techniques, were found to exhibit optical signatures of particle plasmon states in which relative contribution of longitudinal multipolar plasmons is significantly lower than that in equivalent rectangular gold nanorods. Plasmonic response of periodic chains is dominated by dipolar plasmon modes, which in the absence of multipolar exciations are seen as background-free and spectrally well-resolved extinction peaks at infrared (IR) wavelengths. This observation may help improve spectral parameters of IR plasmonic sub-wavelength antennae. Comparative studies of plasmon damping and dephasing in corrugated chains of nanoblocks and smooth rectangular nanorods are also presented.

Band structure observation of 2D photonic crystal with various V-shaped air-hole arrangements

The band structure of three types of photonic crystals is studied. In these photonic crystals, the rotationally asymmetric V-shaped air holes are combined while changing their orientation. We find that the band structure is very sensitive to the method of combination. From this result, we can say that the periodical perturbation produced only by change of the air-hole orientation can change the band structure largely. This idea can be applied to many apprications such as lasers which have unique beam patterns.

Linearly-Polarized Single-Lobed Beam in a Surface-Emitting Photonic-Crystal Laser

A linearly-polarized, single-lobed beam has been demonstrated in a surface-emitting photonic-crystal laser under single-mode operation by employing fine-tuned elliptical lattice points and π-phase shift. A crystal structure, including the elliptical lattice points with a short/long axis ratio of 0.95, has been successfully fabricated. The resulting beam was strongly polarized in one direction, although the shape of the lattice points was nearly circular. It was found that two-dimensional optical coupling was compatible with strong linear polarization.

High-Power Surface-Emitting Photonic Crystal Laser

We report on a record CW surface-emitting output-power operation of 2D photonic-crystal lasers at RT. We also propose new cavity design for further increase of output power.