Position calculation of the frequency band gap in the finite photonic crystal with multiple alternations using boundary element method

In this paper, the wave transmission from finite photonic crystals with multiple alternations is investigated using boundary element method (BEM). Since that, in these structures the alternation is not in all directions of space; the investigations of the frequency band gap with desired accuracy are not practical by analytical methods. Also, the frequency dispersion of dielectric rods is an effective parameter in photonic crystals, which this effect in our calculations has been considered. Due to the high capabilities of the BEM, the transmitted wave spectrum in the photonic crystal is calculated by changing the geometrical and optical parameters of the photonic crystal and applying more alternation in its structure and the position and width of the frequency band gap is investigated. Then, it is assumed that the photonic crystal with an arbitrary angle is rotated around the axis which is perpendicular on the crystal cross section and then, it is irradiated with a plan wave. The band gap of the photonic crystals with the desired structure, desired rotation angle and multiple alternations have been solved. Very low information volume, high speed and accuracy during the calculation and useable for any desired structures are the characteristics of this method.     

Optimizing the spectral efficiency of photonic quantum well structures

One can construct photonic single quantum well structures by sandwiching a homogeneous medium slab as a defect between two symmetrical photonic crystals (PCs). It is shown that the number of observed resonant peaks increases with increasing slab thickness. It is found that while the slab is composed of alternatively stacked step-index films, the frequencies of these resonant peaks can be adjusted finely by changing the film thickness properly. In this case, the frequency and frequency interval of confined states can be tuned accurately, and the spectral efficiency can be greatly enhanced without increasing the volume of optical devices. Numerical simulation is based on the finite-difference time-domain (FDTD) method.     

Photonic crystal waveguides for coarse-selectivity devices

We discuss devices based on photonic crystal planar waveguides for use as wavelength-selective applications via the mini-stopband extraction mechanism. We present experimental data for the core of a compact demux system. We show that spatial and spectral behaviours are as intended from coupled-mode theory, as well as from the finite-difference time-domain approach. Finally, we propose architectures with large crosstalk and some inherent fabrication-related advantages achieved by duplicating the basic multimode waveguide and using it as a spectral filter.     

Photonic crystal channel drop filters with mirror cavities

In this paper, a new channel drop filter in two dimensional photonic crystals with mirror cavities is proposed. In the structure, three cavities are used. One is used for a resonant tunneling-based channel drop filter. The others are used to realize reflection feedback in the bus waveguide, which consists of a point defect micro-cavity side-coupled to a waveguide. The simulation results by using the finite-difference time-domain method conclude 98% output efficiency.     

Trends in microdisk laser research and linear optical modelling

Research into microdisk lasers demonstrates new achievements both in the technology and in the associated physical effects and applications. Melting and rounding of the disk edge boosts the Q-factors due to improved surface smoothness. In-plane cavity shape is widely used as a design instrument. Optimal shaping of pumped area lowers the threshold power. Photonic molecules made of several microdisks as “photonic atoms” show lasing at several closely spaced frequencies. A microdisk with a single quantum dot as an active region is considered as the most promising system for realisation of a single photon emitter necessary for quantum computing. These new effects and devices can be simulated with accurate numerical techniques, developed recently for “warm-cavity” linear modelling, that are able to bring a new vision of the physics of lasing.     

一维光子晶体缺陷模的偏振特性研究

利用周期结构的布洛赫定理推导了一维无限光子晶体缺陷模方程,研究了缺陷模的偏振特性,以及在不同入射角和缺陷层厚度下缺陷模位置的变化.利用传输矩阵方法对有限周期数光子晶体也进行了研究,分别对应一维无限光子晶体和有限周期数光子晶体给出了数值计算结果.通过比较这两者的数值结果得出了缺陷模随入射角和缺陷层厚度变化的一般规律.     

一维光子晶体缺陷模偏振特性的研究

利用一维光子晶体的透射率公式,计算出一维光子晶体掺杂后TE波和TM波缺陷模的波长随入射角的响应曲线、缺陷模透射峰随入射角的响应曲线、缺陷模透射峰随入射波长的响应曲线.研究发现,TE波和TM波的缺陷模透射峰均随入射角的增加而向短波方向移动；TE波缺陷模透射峰的半高宽度(FWHM)和峰值随入射角的增加而减小,而TM波缺陷模透射峰的半高宽度(FWHM)和峰值确随入射角的增加而增加；对TM波其波长为λ0的缺陷模也存在明显的“广义布儒斯特角”现象, TE波的缺陷模不存在“广义布儒斯特角”现象.     

Three-dimensional photofabrication with femtosecond lasers for applications in photonics and biomedicine

A status report on rapidly advancing femtosecond laser technology, three-dimensional (3D) microstructuring by multiphoton illumination technique, is given. Taking its origin from multiphoton microscopy, this technique is now becoming an important microfabrication tool. In our work we apply near-infrared Ti:sapphire femtosecond laser pulses (at 800/780 nm) for 3D material processing. When tightly focused into the volume of a photosensitive material (or photoresist), they initiate 2PP process by, for example, transferring liquid into the solid state. This allows the fabrication of any computer generated 3D structure by direct laser “recording” into the volume of photosensitive material. 2PP of photosensitive materials irradiated by femtosecond laser pulses is now considered as enabling technology for the fabrication of 3D photonic crystals and photonic crystal templates. In particular, 2PP allows one to introduce defects at any desired locations, which is crucial for the practical applications. Recently, we studied possible applications of 2PP technique in biomedicine. 2PP is a very interesting technique for the fabrication of drug delivery systems, scaffolds for tissue engineering, and medical implants. These and other biomedical applications of 2PP will be reviewed.     

Fabrication and optical properties of 3D composite photonic crystals of core-shell structures

Three-dimensional (3D) composite colloidal photonic crystals with SiO₂ core and ZnO shell were fabricated on borosilicate glass (BSG) substrate by a two-stage deposition method. Scanning electron microscopy (SEM) measurements show that both the pre-deposited SiO₂ and SiO₂/ZnO core-shell structures are oriented with their (1 1 1) axes parallel to the substrates. Optical measurement reveals that the periodic arrays exhibit a photonic band gap in the (1 1 1) direction. The optical properties of SiO₂/ZnO core-shell structures strongly depend on the size dispersions of colloidal spheres and the intrinsic defects in the sample.     

Fiber-optic CATV system performance improvement by using split-band technique and photonic crystal fiber

A directly-modulated amplitude modulation-vestigial sideband (AM-VSB) cable television (CATV) erbium-doped fiber amplifier (EDFA)-repeated system that uses split-band technique and photonic crystal fiber (PCF) as a broadband dispersion compensation device is proposed and demonstrated. In contrast to a conventional externally-modulated fiber-optic CATV system, good performance of carrier-to-noise ratio (CNR), composite second order (CSO) and composite triple beat (CTB) were obtained in our proposed systems over a combination of 100-km single-mode fiber (SMF) and 3.6 km PCF.