Design of an optical filter using photonic band gap material

The article presents a design of an optical filter using Photonic Band Gap (PBG) materials in the visible and infrared region of the electromagnetic spectrum. This idea is based on the famous Kronig-Penny model in the band theory of solids. The suggested filter may work at any range of the wavelength that can be achieved by choosing the appropriate values of the controlling parameters. This structure is also able to pass the light emitted by the Ruby laser and this acts as a monochromator. Also, we have studied the anomalous behavior of refractive index for the structure having alternate layers of air and GaAs.     

Diffractionless optical networking in an inverse opal photonic band gap micro-chip

We present a design for a photonic crystal (PC) all-optical micro-chip based on a three-dimensional (3D) inverse opal heterostructure intercalated with a two-dimensional (2D) triangular lattice photonic crystal slab. Within the 2D micro-chip layer, we demonstrate single-mode (diffractionless) waveguiding of light in air, throughout a bandwidth of more than 70 nm near 1.55 μm. This suggests that inverse opal photonic band gap (PBG) materials can facilitate on-chip optical networking functions over the telecommunication frequency band used in current-day optical fibers.     

Nonlinear band gap transmission in optical waveguide arrays

The effect of nonlinear transmission in coupled optical waveguide arrays is theoretically investigated and a realistic experimental setup is suggested. The beam is injected in a single boundary waveguide, linear refractive index of which (n(0)) is larger than refractive indexes (n) of other identical waveguides in the array. Particularly, the effect holds if omega(n(0)-n)/c>2Q, where Q is a linear coupling constant between array waveguides, omega is a carrier wave frequency, and c is a light velocity. Numerical experiments show that the energy transfers from the boundary waveguide to the waveguide array above a certain threshold intensity of the injected beam. This effect is due to the creation and the propagation of gap solitons in full analogy with a similar phenomenon in sine-Gordon lattice [Phys. Rev. Lett. 89, 134102 (2002)]].     

Energy transmission in the forbidden band gap of a nonlinear chain

A nonlinear chain driven by one end may propagate energy in the forbidden band gap by means of nonlinear modes. For harmonic driving at a given frequency, the process occurs at a threshold amplitude by sudden large energy flow that we call nonlinear supratransmission. The bifurcation of energy transmission is demonstrated numerically and experimentally on the chain of coupled pendula (sine-Gordon and nonlinear Klein-Gordon equations) and sustained by an extremely simple theory.     

Optical control of the edge of the band gap of semiconductor layered Fabry-Perot type structures

A mechanism of controlling light is studied, which is based on the change of refractive indices of narrow-gap layers in a semiconductor layered periodic Fabry-Perot type structure (superlattice) caused by the contribution of nonequilibrium charge carriers produced by controlling radiation. By choosing the wavelength of controlling light near the edge of intrinsic absorption of narrow-gap layers and by choosing the wavelength of controlled light near the edge of the band gap of a structure, one can obtain for 1.5-μm controlled radiation the modulation depth above 90%, with controlling radiation intensity of ～6 kW/cm².     

Optical bistability in one-dimensional photonic band gap structures with coupled nonlinear defects

Using the transfer matrix method, we study the transmission property of one-dimensional photonic band gap structure with two coupled nonlinear defects separated by a linear middle layer and find that such composite structure exhibits a bistability that’s strongly dependent of the linear middle layer. The switching threshold values can be greatly reduced just by choosing the proper parameters of the linear middle layer.     

染料掺杂光子晶体荧光带隙边缘的激射研究

利用激光全息光刻技术, 在重铬酸盐明胶 感光材料中制备了掺杂有机染料的层状光子晶体. 在532 nm纳秒脉冲激光激励下, 样品的荧光光谱表现出良好的带隙特征; 随着抽运能量的增加, 在荧光带隙带边位置获得了激射光, 并进一步研究了光子晶体的带边位置与染料荧光峰的匹配对激射的影响.带边位置越靠近染料的荧光峰, 激射阈值越低, 反之则不易产生激射.该研究为超低阈值光子晶体激光器的发展提供了思路和方法. 关键词： 全息光刻 光子晶体 荧光带隙 低阈值激射     

Generation of the second optical harmonic in porous-silicon-based structures with a photonic band gap

Efficient generation of the second optical harmonic is observed experimentally in a multilayer periodic structure based on porous silicon. The second-harmonic signal is much stronger than the signal from a uniform porous silicon layer or from the single-crystal silicon substrate. The orientational dependence of the second-harmonic signal is isotropic. The second-harmonic intensity as a function of the reflection angle reaches a maximum in the direction corresponding to the minimum phase detuning in a multilayer periodic structure. Pis’ma Zh. éksp. Teor. Fiz. 69, No. 4, 274–279 (25 February 1999) Deceased.     

One dimensional photonic band gap material as an omnidirectional reflector

In this article, the reflection properties in one-dimensional dielectric-dielectric photonic band gap (PBG) structure have been studied. We have used SiO₂ as material of low refractive index and Te as a high refractive index material. Reflectivity of proposed PBG structure is plotted as a function of wavelength and angle of incidence and omni-directional PBGs are computed theoretically. To obtain reflectance, we used transfer matrix method for solving Maxwell’s equations for electromagnetic wave in PBG structures. For a large range of frequency, the PBG structure is found to exhibit omni-directional reflection which can be exploited in devices such as optical resonators, mirrors, etc.     

双负介质对光子晶体透射能带谱的简并效应研究

利用传输矩阵法理论,通过数值计算模拟的方法,研究双负介质对一维光子晶体透射能带谱的影响。结果表明:当C介质由双正介质变成双负介质时,光子晶体(CBAABC)n的禁带、能带和光子晶体(AB)m(CBAABC)n(BA)m的透射峰均出现明显的简并现象,即前者相邻多禁带和多能带结构简并为较宽的单禁带和单能带结构,后者的透射峰由2n+1条简并成2n-1条;当双负介质C的光学厚度负值减小时,光子晶体(AB)m(CBAABC)n(BA)m的透射峰向禁带中心靠拢,出现简并趋势。双负介质对光子晶体透射能带谱的简并效应,为光子晶体设计光学滤波器件、光学开关等提供参考。     

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用时域有限差分法研究了电磁波在等离子体光子晶体中的传播特性。数值模拟中使用完全匹配层吸收边界条件,计算了电磁波通过等离子体光子晶体的反射和透射系数。讨论了等离子体密度、等离子体温度、介电常数比和引入缺陷层对等离子体光子晶体光子带隙的影响。     

Analysis of photonic band gap structure for the design of photonic devices

A detailed analysis, based on Kronig–Penney model and finite-difference time-domain (FDTD) method, is used to explain the air-filling factor effect on the optical properties of defect-free photonic crystals. By the use of the Kronig–Penney model, we calculated the photonic band structure for electromagnetic waves in a structure consisting of a periodic square array of dielectric rods of lattice constant a separated by air holes. Gaps in the resulting band structures are found for waves of both polarisations. We analysed the air-filling factor effect on both polarisations in low and high frequency regions. It is shown that the frequency of the lower TE (transverse-electric) band edge is independent of the air-filling factor in the low frequency region. The opposite behaviour holds for the upper band edge, growing rapidly with the air-filling factor. Using the FDTD we simulated the electric field as the pulse propagates through the structure. The results of both approaches are compared, and the operation characteristics of the measuring air-filling factor device are described. We investigate the optical properties of a single and two defects incorporated in the PC, which can be potentially applied to ultra small surface-emitting-type channel drop filter. It is shown that the frequency and polarisation of the dropped light can be controlled by changing the size and/or shape of the defect. The electric field distribution calculations show that the electric field for a given frequency is located only at the defect, which means that each defect can detect only its corresponding wavelength. To cite this article: F. Ouerghi et al., C. R. Physique 5 (2004).     

Entanglement of a two-level atom and its spontaneous emission near the edge of a photonic band gap

The entanglement of a two-level atom and its radiation field near the edge of a photonic band gap is studied by using the quantum entropy. Unlike the free space case, there is a steady-state entanglement between the atom and its spontaneous emission field even when the atomic transition frequency lies outside the band gap. Moreover, the degree of entanglement, which is due to the formation of atom–photon bound dressed state, depends on the detuning of the atomic transition frequency from the photonic band edge and can be controlled by a controllable photonic band gap crystal.     

Confined band gap in an air-bridge type of two-dimensional AlGaAs photonic crystal

The transmittance spectrum for an air-bridge type of AlGaAs photonic crystal (PC) slabs successfully fabricated was measured. It is found that the observed spectrum is consistent with both the theoretical band structure and the calculated one. Moreover, the transmittance due to the modes below the light line is found to be almost 100%, indicating that the guided modes should exist. The respective stop bands are observed in the gamma-M direction for TM-like and TE-like modes, implying that a photonic band gap should exist for the TE-like guided modes. The present PC is very suited for controlling the radiation field.     

Low-threshold lasing at the edge of a photonic stop band in cholesteric liquid crystals

Low-threshold lasing is observed at the edge of the stop band of a one-dimensional structure-a dye-doped cholesteric liquid-crystal film. The mode closest to the edge has the lowest lasing threshold. The rates of spontaneous and stimulated emission are suppressed within the stop band and enhanced at the band edge. The ratio of right to left circularly polarized spontaneous emission is in good agreement with calculated density of photon states.