Effect of disorder on self-collimated beam in photonic crystal

We report a numerical analysis of various types of disorder effects on self-collimated beam in two-dimensional photonic crystal. Finite-difference time-domain (FDTD) method is used to simulate the process by using a pulse propagation technique. The position disorders along the directions parallel and perpendicular to the incidence are considered. We show that random disorder along the perpendicular direction will have a lesser effect on the performance of the dispersion waveguides than those along the parallel direction. Furthermore, the self-collimation waveguide (SCW) has new characteristics when compared with the photonic crystal line defect waveguide. (c) 2006 Elsevier B.V. All rights reserved.

Design of two-dimensional photonic crystal edge emitting laser for photonic integrated circuits

An edge emitting laser based on two-dimensional photonic crystal slabs is proposed. The device consists of a square lattice microcavity, which is composed of two structures with the same period but different radius of air-holes, and a waveguide. In the cavity, laser resonance in the inner structure benelits from not only the anomalous dispersion characteristic of the first band-edge at the M point in the first Brillouin-zone but also zero photon states in the outer structure. A line defect waveguide is introduced in the outer structure for extracting photons from the inner cavity. Three-dimensional finite-difference time-domain simulations apparently show the in-plane laser output from the waveguide. The microcavity has an effective mode volume of about 3.2(lambda/eta(slab))(3) for oscillation -mode and the quality factor of the device including line defect waveguide is estimated to be as high as 1300.

Tunable Fano resonance in photonic crystal slabs

A three dimensional analysis of a special class of anisotropic materials is presented. We introduce an extension of the Scattering Matrix Method (SMM) to investigate the behavior of anisotropic Photonic Crystal Slabs (PhCS) subject to external radiation. We show how the Fano effect can play a fundamental role in the realization of tunable optical devices. Moreover, we show how to utilize electron injection, electric field and temperature as parameters to control the Fano resonance shift in both isotropic and anisotropic materials as Si and Potassium Titanium Oxide Phosphate (KTP). We will see that because Fano modes are sensitive and controllable, a broad range of applications can be considered. (c) 2006 Optical Society of America

Light-propagation characteristics of photonic crystal waveguide based on SOI materials at different polarized states

Straight single-line defect optical waveguides in photonic crystal slabs are designed by the plane wave expansion method and fabricated into silicon-on-insulator (SOI) wafer by 248-nm deep UV lithography. We present an efficient way to measure the light transmission spectrum of the photonic crystal waveguide (PhC WG) at given polarization states. By employing the Mueller/Stokes method, we measure and analyse the light propagation properties of the PhC WG at different polarized states. It is shown that experimental results are in agreement with the simulation results of the three-dimensional finite-difference-time-domain method.

Dipole mode photonic crystal point defect laser on InGaAsP/InP

In this paper, we focus on the dipole mode of the two-dimensional (2D) photonic crystal (PC) single point defect cavity (SPDC) lasers and we report the fabrication and characterization of 2D PC SPDC lasers with the structure of adjusted innermost air holes. The photonic band and cavity Q factors are simulated by means of plane wave expansion (PWE) and finite-difference time-domain (FDTD), respectively. In order to improve the optical confinement of the SPDC, the diameter of the innermost holes was adjusted. Different lasing performances are observed experimentally. The experimental results agree with the theoretical prediction very well. (c) 2006 Elsevier B.V. All rights reserved.

Photoluminescence from the nitrogen-perturbed above-bandgap states in dilute GaAs1-xNx alloys: A microphotoluminescence study

Using microphotoluminescence (mu-PL), in dilute N GaAs1-xNx alloys, we observe a PL band far above the bandgap E-0 with its peak energy following the so-called E+ transition, but with contribution from perturbed GaAs host states in a broad spectral range (> 100 meV). This finding is in sharp contrast to the general understanding that E+ is associated with a well-defined conduction band level (either L-1c or N-x). Beyond this insight regarding the strong perturbation of the GaAs band structure caused by N incorporation, we demonstrate that a small amount of isoelectronic doping in conjunction with mu-PL allows direct observation of above-bandgap transitions that are not usually accessible by PL.

Line defect splitters for self-collimated beams in photonic crystals

A one-to-two splitter for self-collimated beams in photonic crystal (PC) is designed by inserting one row of line defects. Finite-difference time-domain (FDTD) method is used to simulate the light propagation process. Our systematical studies show that the splitting ratio is a function of the airholes size of the line defect radius, and stays fairly constant as a function of frequency. Furthermore, it is shown the numerical results can be analyzed by coupled-mode theory. (C) 2005 Elsevier B.V. All rights reserved.

Optical properties of semiconductor quantum-well material using photonic crystal fabricated by micro-fabrication machine

Two-dimensional photonic crystals in near infrared region were fabricated by using the focused ion beam ( FIB) method and the method of electron-beam lithography (EBL) combined with dry etching. Both methods can fabricate perfect crystals, the method of FIB is simple,the other is more complicated. It is shown that the material with the photonic crystal fabricated by FIB has no fluorescence,on the other hand, the small-lattice photonic crystal made by EBL combined with dry etching can enhance the extraction efficiency two folds, though the photonic crystal has some disorder. The mechanisms of the enhanced-emission and the absence of emission are also discussed.

Investigation progress on key photonic integration for application in optical communication network

Proceeding from the consideration of the demands from the functional architecture of high speed, high capacity optical communication network, this paper points out that photonic integrated devices, including high speed response laser source, narrow band response photodetector high speed wavelength converter, dense wavelength multi/demultiplexer, low loss high speed response photo-switch and multi-beam coupler are the key components in the system. The, investigation progress in the laboratory will be introduced.

Impact of wide bandgap p-type nc-Si on the performance of a-Si solar cells

This paper reports the impact of a wide bandgap p-type hydrogenated nanocrystalline silicon (nc-Si:H) on the performances of hydrogenated amorphous silicon (a-Si:H) based solar cells. The player consists of nanometer-sized Si crystallites and has a wide effective bandgap determined mainly by the quantum size-confinement effect (QSE). By incorporation of this p-layer into the devices we have obtained high performances of a-Si:H top solar cells with V-infinity=1.045 V and FF=70.3 %, and much improved mid and bottom a-SiGe:H cells, deposited on stainless steel (SS) substrate. The effects of the band-edge mismatch at the p/i-interface on the I-V characteristics of the solar cells arc discussed on the bases of the density-functional approach and the AMPS model.

Photonic switch and NOT logic gate based on the hybrid integration of a GaAsVCSEL and a GaAs MISS

The hybrid integrated photonic switch and not logic gate based on the integration of a GaAs VCSEL (Vertical Cavity Surface Emitting Lasers) and a MISS (Metal-Insulator-Semiconductor Switches) device are reported. The GaAs VCSEL is fabricated by selective etching and selective oxidation. The Ultra-Thin semi-Insulating layer (UTI) of the GaAs MISS is formed by using oxidation of A1As that is grown by MBE. The accurate control of UTI and the processing compatibility between VCSEL and MISS are solved by this procedure. Ifa VCSEL is connected in series with a MISS, the integrated device can be used as a photonic switch, or a light amplifier. A low switching power (10 mu W) and a good on-off ratio (17 dB contrast) have been achieved. If they are connected in parallel, they perform a photonic NOT gate operation.

Single dipole mode photonic crystal laser on InGaAsP/InP QW waveguide slab - art. no. 698436

Single point defect microcavity possesses only the degenerate dipole modes under certain photonic crystal structure parameters. By deforming lattice structure, the degeneracy of the dipole modes has been broken. Theoretical simulation shows the large splitting of 65nm between the splitted x-mode and y-mode, approximate to the luminescent gain spectrum, which benefits for the single mode lasing. Experimentally the single dipole mode lasing, y-mode, is achieved in the deformed microcavity.

Mode analysis of photonic crystal polarization beam splitter and its application in integrated circuits design - art. no. 698437

In this work, the guided modes of a photonic crystal polarization beam splitter (PC-PBS) are studied. We demonstrate that the transmission of a low-loss photonic crystal 120 degrees waveguide bend integrated with the PBS will be influenced if the PBS is multi-moded. We propose a single-moded PC-PBS structure by introducing deformed structures, and it shows twice the enhancement of the transmission. This device with remarkable improvement of performance is promising in the use of photonic crystal integrated circuits design.

The whispering gallery mode in photonic crystal ring cavity - art. no. 698438

Whispering gallery modes (WGMs) in microcavities possess ultra-high cavity Q factor. Such microcavity are easy to be fabricated, so WGMs have attracted much attention in the area of photonics and integrated photonic circuits. It is well known that the effect of total internal reflection restricts the size of this mirocavity. Such drawback goes against the integration of photon. However, the photonic crystal microcavities (PCMC) make a breakthrough recently. The WGMs in the PCMC are possible to gain both ultra-high Q and ultra-small mode volume. In this paper, the property of the mode in photonic crystal ring cavity is analyzed by FDTD and PWE. By modifying the airholes in the corners of the ring cavity, we can obtain the WGM. Also the Q factor of WGM in photonic crystal ring cavity is calculated. This favors the design of the photonic crystal microcavity components.