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1.
The slow light propagation in a line waveguide in the two-dimensional triangular photonic crystal has been numerically studied, based on which a wideband photonic crystal waveguide with low group-velocity and low dispersion is proposed. The numerical simulation analysis shows that it is possible to maximize the group index and minimize the group-velocity dispersion in wide bandwidth by increasing the radius of the basic air hole and changing the position of the first two rows of air holes in photonic crysta...  相似文献   

2.
We present a procedure to generate wideband and low dispersion slow light in slotted photonic crystal waveguide. By shifting the first and second rows of air holes of slotted photonic crystal waveguide, the bandwidth of slow light can be increased, with small group velocity dispersion. Using 2D plane wave expansion method, we numerically demonstrate slow light with the nearly constant group indices of 23, 42, and 54 over 17.6 nm, 6.7 nm and 3.3 nm bandwidth, respectively. The maximal normalized delay-bandwidth product is 0.26. From the fabrication's point of review, shifting the position of holes is easier to be controlled technically than changing the diameters of air holes. In addition, our simulations suggest this design is tolerant to deviation for positions of the first two rows of air holes. Therefore, the proposed approach decreases the dependence on the fabrication accuracy.  相似文献   

3.
Hong Jun Shen  Qing Lan Zhang 《Optik》2011,122(13):1174-1178
We report a low-loss photonic crystal slab waveguide formed by deforming the innermost circle air holes in the conventional photonic crystal slab waveguide into elliptical ones. We obtain the photonic bands and group index of guided modes in this photonic crystal waveguide by guided-mode expansion method and investigate the dependence of photonic bands and group index of guided modes on the parameters of the innermost elliptical air holes. The group velocity and group velocity dispersion of this waveguide strongly depend on the innermost elliptical air holes. Photonic crystal slab waveguide with the optimum innermost elliptical air holes possesses a wider single mode region below the light line, in which light can easily propagate without intrinsic loss. At the same time, the guided mode supported by this waveguide has nearly constant group velocity and vanishing group velocity dispersion in a 3-5 nm bandwidth.  相似文献   

4.
A photonic crystal waveguide embedded in silica is proposed and the effects of number of defect rows adjacent to the line-defect, number of rows shifted in transverse direction to the light propagation and the types of holes in these rows on slow light properties are investigated without changing the line-width by plane-wave expansion method. We observe that the structure with one row of ring-shaped holes exhibits better slow light properties than the structure with two and three innermost rows of ring-shaped holes when outer and inner radius of the holes are considered as free parameters. Shifting the second innermost rows of holes is found to be preferable than shifting the second innermost rows of rings. Besides, shifting the second and third innermost rows together does not make considerable enhancement on the slow light properties as shifting only the second innermost rows, no matter the shifting holes are ring-shaped holes or only holes.  相似文献   

5.
一种新型无色散慢光光子晶体薄板波导   总被引:1,自引:0,他引:1       下载免费PDF全文
沈宏君  田慧平  纪越峰 《物理学报》2010,59(4):2820-2826
利用椭圆形孔替代传统光子晶体薄板波导中邻接波导的最内层两排圆孔构成一种新型低损耗光子晶体薄板光波导.该波导的群速度和群速度色散特性强烈依赖于波导中这两排邻接波导的椭圆孔的特性.借助波导导模展开方法,计算得到波导的能带结构和群指数,并分析了它们与椭圆孔的参数关系.通过优化这些椭圆孔的参数,可以增加光子晶体光波导导模在光锥以下的无固有传输损耗带宽,在2—45 nm 的带宽上实现无色散的常数群速度.这些理论结果将为低损耗低色散慢光波导的设计制造提供理论基础. 关键词: 光子晶体薄板波导 群速度 群指数 群速度色散  相似文献   

6.
Symmetrically perturbed photonic crystal waveguide can be constructed by inserting perturbative dielectric rods into photonic crystal waveguide structure with whose rods’ radius distributed according to a certain proportion. Slow light properties in this new structure are studied by using the plane wave expansion method (PWM). In this paper, schemes of adjusting radius of perturbative dielectric rods and adjusting the dielectric constant of perturbative dielectric rods are proposed to optimize slow light properties. The result shows that the scheme for adjusting radius of perturbative rods can realize larger average slow light bandwidth and efficiently control the NDBP value of the waveguide, but it contributes little to obtain smaller group velocity. The scheme for adjusting dielectric constant of perturbative rods can realize smaller group velocity, but can only obtain smaller slow light bandwidth and cannot efficiently enlarge NDBP value of waveguide. Both optimization schemes proposed in this paper realize group velocity that is two magnitudes smaller than the vacuum speed of light meanwhile maintaining large NDBP and low GVD region. Our results provide important theoretical basis for the potential application offered by symmetrically perturbed photonic crystal in future optical networks.  相似文献   

7.
We propose a novel photonic crystal slab waveguide that provides a single-mode band with large bandwidth. The proposed waveguide is obtained by introducing a line defect in a triangular lattice of air holes in a dielectric slab. This line defect consists of holes which are not located in the original lattice points. The plane wave expansion (PWE) method is used to extract the band diagram of guiding modes and based on the results, photonic crystal holes in the defect row and its adjacent rows are modified to maximize the waveguide bandwidth. We show that using the proposed structure, a single-mode bandwidth of 17% can be achieved.  相似文献   

8.
高品质因子和高传输效率的二维光子晶体耦合腔波导研究   总被引:2,自引:1,他引:1  
吕冬妮  沈宏君  余建立 《发光学报》2012,33(11):1241-1246
基于时域有限差分方法,通过仿真计算设计了一种具有较高品质因子和传输效率的二维光子晶体耦合腔波导结构。通过改变二维光子晶体波导微腔结构中隔绝波导与微腔的空气孔的半径和数量,在获得近似90%的传输效率的同时,使得品质因子达到了8.20×104。为了使品质因子在大幅度提高的同时,传输效率只有小幅度的降低,在波导微腔结构中引入了链式微腔。将链式微腔结构与传统的波导微腔结构相结合,使这种新形式的耦合腔结构的品质因子提高了1个数量级,传输效率仅下降了约40%。  相似文献   

9.
In this paper, we propose the use of two two-dimensional photonic crystal line defect waveguides for slow light with large delay–bandwidth product (DBP). One includes air rings localized at each side of the line defect and the other modifies the radius and distance of holes at each side of the waveguide. We show that we can achieve a very flat band corresponding to nearly constant group index over a broad frequency range by adjusting the parameters of the structure. We show further that the group velocity dispersion (GVD) can reach a relatively small amount and the DBP can be more than 0.6 for the first waveguide and 0.34 for the second waveguide. Numerical simulation by the finite-difference time-domain (FDTD) method demonstrates the propagation of the broadband pulse.  相似文献   

10.
This work proposed a methodology based on the liquid infiltration of slotted photonic crystal waveguide (SPCW). By choosing the refractive index that infiltrated in the first and second rows of air holes adjacent to the slot, respectively, SPCW was optimized to possess wideband slow light with large group index and low dispersion. The properties of SPCW were numerically simulated by plane wave expansion (PWE) method and finite-difference time-domain (FDTD) method. Simulation results showed that the designed SPCW could control the group index for the same SPCW with the nearly constant group index of 50, 68, 81, 150, and 200 over 7.5 nm, 5.5 nm, 3.1 nm, 1.65 nm, and 1.15 nm. In addition, we demonstrated that this post-fabrication liquid infiltrated technology has the potential for realizing reconfigurable and tunable SPCW, in which the flexible wavelength range of SPCW can also be controlled by different liquid infiltration.  相似文献   

11.
In this paper, two novel types of semi-slow light photonic crystal waveguide with large transmission bandwidth obtained by shifting the boundaries of a W1 waveguide in the direction of light propagation are presented. One includes air rings localized at only one side of the line defect and the other replaces the holes at each side of the waveguide by the uniform air rings which are constructed by the homocentric square dielectric rod inserted into the air holes. The structure produces unusual “n-type” transmission spectrum depending on the different parameters such as inner radius of air ring, dielectric constant of square dielectric rod, etc. It is shown that the transmission spectra of the two structures are completely different from each other. A versatile control of light propagation with large normalized bandwidth and slow light phenomena can be obtained using a unique geometrical parameter. Numerical simulation by the finite-difference time-domain (FDTD) method demonstrates the propagation of the broadband pulse.  相似文献   

12.
The monolithic combination of active light sources with photonic crystal (PC) waveguide components is a key building block for future highly integrated photonic circuits. We demonstrate the coupling of light from an InGaAs/AlGaAs ridge waveguide laser to a monolithically integrated 2D PC waveguide. The PC guide is formed by removing three or five rows in a triangular lattice of air rods etched into the semiconductor. A tapered ridge waveguide geometry is demonstrated to improve coupling efficiency, so that maximum output powers of up to 10 mW from the PC waveguide are achieved. The resulting coupled cavity laser shows single mode emission with side mode suppression ratios > 35 dB over a broad range of injection currents.  相似文献   

13.
研究了慢光模式在SOI(silicon-on-insulator)材料光子晶体线缺陷弯折波导中的传输特性. 通过优化波导弯折处的结构参数,慢光模式在光子晶体60°与120°弯折波导中的透射率提高10倍以上,归一化透射率分别达到80%和60%以上. 为了进一步减慢光速,设计了新颖的高Q值耦合腔弯折波导结构,在归一化透射率达到75%的基础上,光波群速度低至c/170(c为真空光速). 研究结果对于增强光子晶体的慢光效应,提高光子晶体慢光器件的微型化和集成化都有一定的积 关键词: 光子晶体 慢光 弯折波导 透射率  相似文献   

14.
一种新型光子晶体波导定向耦合型超微偏振光分束器   总被引:3,自引:1,他引:2  
将两个二维空气孔光子晶体波导平行放置,两波导之间由三排空气孔相隔,构成一个定向耦合器.数值分析了TE(磁场平行于空气孔)和TM(电场平行于空气孔)偏振态光波在该定向耦合器中的传播行为.结果表明,减小耦合区两波导间的一排介质柱的半径,TE模的耦合长度减小,而TM模的耦合长度不变.基于此结构,设计了超微偏振光分束器,整个器件的尺寸为10.1μm,与已报道的24.2μm的结果相比,该器件具有更小的器件尺寸和更高的输出效率.  相似文献   

15.
张昌莘  许兴胜 《中国物理 B》2012,21(4):44213-044213
A two-dimensional photonic crystal coupled-cavity waveguide is designed and optimized, the transmission spectrum is calculated by using the finite-difference time-domain method, and the group velocity of c/1856 is obtained. To our knowledge, this value of group velocity is the lowest group velocity in a photonic crystal waveguide calculated from its transmission spectrum so far. The result is confirmed by the photonic band structure calculated by using the plane wave expansion method, and it is found that the photonic crystal waveguide modes in a photonic band structure are in accordance with those in the transmission spectrum by using the finite-difference time-domain method. The mechanism of slow light in the coupled-cavity waveguide of photonic crystal is analysed.  相似文献   

16.
X. Guo  X. Wu  H. Cui  F. Yang  J. Zhou 《Physics letters. A》2019,383(16):1983-1987
We propose a graphene-based photonic crystal (PC) slow light waveguide, which is realized by creating periodical air holes in a silicon layer to achieve spatially varying chemical potentials of graphene. The structure is optimized around 30 THz, and a large group index of 166.6 is obtained, with a very low propagation loss of ?2.1 dB/um. The corresponding normalized delay-bandwidth product reaches as high as 4.00. Furthermore, the slow light performance can be dynamically tuned by changing a bias voltage. The center frequency of the slow light waveguide can be tuned between 19.1 THz and 27.4 THz. Our results suggest that graphene-based PC structures are very promising for slow light devices.  相似文献   

17.
We propose a slow-light photonic crystal waveguide, which uses a combination of circular and elliptical air holes arranged in a hexagonal lattice with the background material of silicon nitride (refractive index n = 2.06). Large value of normalized delay bandwidth product (NDBP = 0.3708) is obtained. We have analyzed nonlinear performance of the structure. With our proposed geometry strong SPM is observed at moderate peak power levels. Proposed photonic crystal waveguide has slow light applications such as reduction in length and power consumption of all-optical and electro-optic switches at optical frequency.  相似文献   

18.
We systematically analyze the effects of the use of an inaccurate supercell termination and an insufficient supercell size of plane-wave expansion method on the dispersion and the slow light properties of the photonic crystal waveguides. The inattentive use of supercells of photonic crystal waveguides appeared in the literature is found to be yielding errors in the dispersion and slow light characteristics of the fundamental guided mode of photonic crystal waveguides. In addition, extra modes appear in the photonic band gap of the photonic crystal waveguide due to inaccurate supercell termination. By examining the field distribution of the modes, the extra modes can be determined and removed from the band diagram. The dispersion, group index and bandwidth characteristics are observed to be less affecting from inaccurate supercell termination as the number of rows adjacent to the waveguide increases. Moreover, the dispersion and the group index-frequency curves of the fundamental guided mode of correctly terminated supercells are found to be converging as the lateral row number along the line-defect is increased.  相似文献   

19.
In the paper, a novel power-splitting scheme based on two dimensional photonic crystal (2D PhC) is proposed. The structure can be divided into three sections, including the input waveguide, coupling region, and output region, and the latter two sections consist of two parallel waveguides placed in proximity. The operation principle of the splitter is that only one of the super-modes splitting from the directional coupler can propagate through coupling region in the frequency range of interest. The radius of air holes next to the guiding region in coupling region is increased to avoid the acute back reflection at the entrance to the input waveguide induced by the modes mismatch between the input waveguide and coupling region. While in output region, the radius of these corresponding air holes is also increased so that the two splitting super-modes have same propagation constants to avoid the coupling between the two output waveguides. Moreover, as the length of coupling region is varied, its influence on the splitting performance is discussed, and it is verified that the relationship between the splitter length and bandwidth has a trade-off.  相似文献   

20.
The slow light and group velocity dispersion properties of 2D triangular lattice photonic crystal line defect waveguide (PCW) with square and circular air-holes are numerically investigated with the plane-wave expansion method. The simulation results show that the guided mode is impacted slightly by the cross section’s shape of the air-holes of the same filling ratio. Adjusting two rows of the inner-hole adjacent to the waveguide and modifying the waveguide width can bring in low-group velocity and low-dispersion (LVLD) region, in which the group index of the square holes can reach 210 which is far better than the circular-holes. At the same air-hole size and waveguide width, the PCW with the square holes can support higher bit rate of the signal up to 35 Gb/s. These results provide important theoretical basis for realizing of optical buffering and optical logic devices in all-optical network.  相似文献   

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