Semiconductor three-dimensional and two-dimensional photoniccrystals and devices

Semiconductor three-dimensional (3-D) and two-dimensional (2-D) photonic crystals and their effects on the control of photons are investigated for possible applications to optical chip and functional devices. First we review our approaches creating full 3-D photonic bandgap crystals at near-infrared wavelengths, and also functional devices based on 2-D photonic crystals where the focus is on surface-emitting-type channel-drop filtering devices utilizing single defects in 2-D photonic crystal slabs. Then, we describe the recent progress on 3- and 2-D crystals. On 3-D crystals, the effect of the introduction of a light emitter into the 3-D photonic crystal is investigated, and the design of a single defect cavity is performed. On the 2-D photonic crystals, the photonic states are investigated from the perspective of their polarization properties     

Toward controllable photonic crystals for centimeter- andmillimeter-wave devices

In this paper, we present several experimental and theoretical studies showing the feasibility of active photonic crystal controlled either by electrical elements or by light. The controllability of photonic crystals at centimeter wavelengths is proposed with the periodic insertion of diodes along the wires of a two-dimensional (2-D) metallic structure. For only three crystal periods with commercially available devices, more than 30 dB variations of the crystal transmission are predicted over a multigigahertz range by switching the diodes. From calculation models, a tight analogy is shown between these crystals and those consisting of discontinuous metallic rods with dielectric inserts. The numerical models as well as the proposed technology are validated by experimental measurements on 2-D crystals with either continuous or discontinuous metallic rods. The partial control of a 3-D layer-by-layer dielectric structure at millimeter wavelengths is also demonstrated in the second part of the work. A laser light is used to modulate the transmission level of defect modes by photo-induced free carrier absorption. The overall results are expected to contribute to further developments of switchable electromagnetic windows as well as to tunable waveguide structures in the microwave and millimeter wave domains     

二维金属型光子晶体的有限差分法分析

运用空域有限差分法对二维金属型光子晶体的带隙特性进行了分析,介绍了在周期边界以及金属柱面边界条件下,光子晶体单元内差分矩阵方程的建立过程,通过对所得差分矩阵行列式等于零的特征方程的求解,得出不同周期边界条件下相应的本征频点,从而求得光子晶体的能带结构图。对不同结构的二维金属型光予晶体进行了计算,计算结果经时域有限差分法（FDTD）给出了有效验证。     

一种缓变结构一维光子晶体的缺陷模研究

利用传输矩阵方法,研究了单折射率层缓变准周期结构一维光子晶体存在不同缺陷时的缺陷模。结果表明,当该准周期结构中存在缺陷时,引入了缺陷模,且缺陷模与缺陷层的位置和结构参数相关。缺陷层不同,缺陷模的位置及共振透射峰也不同。随着缺陷层光学厚度的增大,缺陷模波长向长波方向移动。     

Localized function method for modeling defect modes in 2-D photoniccrystals

We present a novel, general, and numerically efficient treatment of electromagnetic modes localized at defects in two-dimensional (2-D) photonic crystals. The method represents the fields in terms of orthogonal functions localized at the defect and is a fully vector treatment     

含有负折射率缺陷的光子晶体中的局域缺陷模

研究了含有负折射率缺陷的光子晶体中的局域缺陷模。利用传输矩阵方法计算了含有3个负折射率缺陷的一维光子晶体的透射谱,讨论了缺陷间的相互作用对缺陷模的影响。与正折射率缺陷情形相比较,负折射率缺陷间的相互作用对缺陷模的影响更大,局域模谱线更宽。     

等离子体填充二维金属光子晶体色散特性研究

 提出了等离子体填充的二维金属光子晶体模型,采用时域有限差分法研究了等离子体填充的二维正方晶格和三角晶格金属光子晶体的色散和带隙特性.对比分析了两种结构中等离子体密度对TM及TE模式传播特性的影响规律.研究发现,由于背景等离子体的引入,二维金属光子晶体的色散曲线明显往高频方向移动,等离子体密度的改变可同时控制TE和TM模的带隙位置和禁带宽度.这些特性使得二维等离子体金属光子晶体在设计可调谐光子晶体器件方面具有潜在的应用价值.     

Intrinsic Surface and Bulk Defect Modes in Quasi-Periodic Photonic Crystals

By analyzing resonances in the local density of states (LDOS) for a fivefold 2-D quasi-periodic photonic crystal (QPC), we reveal the presence of a well-defined number of defect modes in the spectral region of a low LDOS, which are intrinsic to this class of photonic structures. We may distinguish between surface modes, depending on the truncation of the finite-sized structure, and bulk modes. All defects can be traced to a configuration of closely spaced cylinders. Due to mutual coupling, their collective eigenresonance is strongly shifted into the spectral region of a low LDOS, and they appear as defect modes, which are comparable to acceptor modes in periodic photonic crystals. Control over the geometrical parameters of such resonators allows for a simple adjustment of the defect mode frequencies in QPCs.     

Power Density and Efficiency of Thermophotovoltaic Energy Conversion Using a Photonic-Crystal Emitter and a $hbox{2}$ -D Metal-Grid Filter

Three-dimensional metallic photonic crystals have been suggested to be ideal candidates for thermal emitters in thermophotovoltaic energy conversion systems due to their high emission power in the allowed passband and also their emission suppression in the long-wavelength tail. In this paper, calculations were performed to compare a photonic-crystal emitter and a blackbody emitter in the thermodynamic limit of the maximum power density and efficiency that are achievable with an ideal photovoltaic cell. Additionally, realistic-source and GaSb photovoltaic-cell optical characteristics and a novel metal-grid filter are incorporated into the calculations. With an ideal antireflection coating, the measured photonic-crystal radiation was found to give a source electrical power density of 7.77 W/cm² and a system efficiency of 47.58% with an effective source temperature of 1535 K.     

0.35 THz二维光子晶体带通滤波器设计

设计了一种基于二维光子晶体的太赫兹带通滤波器,通过在线缺陷的光子晶体波导两侧引入对称的点缺陷形成谐振腔,在太赫兹频段实现了较好的带通滤波特性。这种二维光子晶体带通滤波器具备较宽的通带带宽,同时还可以通过增加多组对称点缺陷的方式实现多个谐振腔的级联,进一步提高带外抑制特性,可满足太赫兹通信或雷达系统的应用需求,具有良好的应用价值。     

不同背景介质下金属Cu光子晶体带隙

提出了一种利用全反射抑制二维光子晶体表面电磁波泄漏的方法,并计算了不同背景介质下的二维金属Cu光子晶体的带隙结构,得到了带隙结构与填充率间的关系曲线。计算方法采用时域有限差分,金属型光子晶体由Cu柱构成。分别计算了以空气为背景介质和以PMMA为背景介质的正方晶格金属型光子晶体的带隙结构。研究结果表明：以PMMA为背景介质的正方晶格金属型光子晶体与以空气为背景介质相比,第一带隙更窄,第二带隙中心频率更低,且在填充率大于0.70时将会出现第三带隙。这对进一步扩展这种光子晶体的应用具有良好的参考意义。     

Artificial Defect Engineering in Three‐Dimensional Colloidal Photonic Crystals

Artificial defect engineering in 3D colloidal photonic crystals is of paramount importance in terms of device applications. Over the past few years, we have carried out a great deal of research on introducing artificial defects, including point, line, and planar defects, in 3D colloidal photonic crystals by using “bottom‐up” self‐assembly in combination with “top‐down” micromachining techniques. In this Feature Article, we summarize our research results regarding the engineering of artificial defects in self‐assembled 3D photonic crystals, along with other important research breakthroughs in the literature. The significant advancements in the engineering of defects as reviewed here together with the encouraging reports on the fabrication of perfect colloidal crystals without unwanted defects will collectively lead to technological applications of self‐assembled 3D photonic crystals in the near future.     

光子晶体齿状波导的滤波特性研究

为了设计基于光子晶体波导的高性能滤波器件,在2维正方格子光子晶体波导结构中引入一系列齿状缺陷,采用有限元法对齿状光子晶体波导的传输特性进行了数值仿真和理论分析。结果表明,对于单个齿状缺陷,缺陷产生的共振频率使得在光子晶体波导通频域带出现带隙结构,可以实现良好的窄带滤波,并且通过改变齿状缺陷深度可以有效地控制缺陷的共振频率;引入多个齿状缺陷,缺陷之间会经过耦合作用形成一系列缺陷态,使得在光子晶体波导导通频域中出现宽带的带隙结构,可以实现宽带滤波。该光子晶体波导滤波器对窄/宽带滤波可根据波导结构中引入的齿状缺陷进行简单灵活调节。此研究在设计基于光子晶体波导的光子滤波器件方面具有潜在的应用价值。     

正负折射率含缺陷1维光子晶体多通道滤波器

为了分析结构参量对正负折射率材料1维光子晶体缺陷模的影响,利用传输矩阵法计算了基于正负折射率材料含正折射率缺陷1维光子晶体B（AB）m（ACB）n（AB）mB的透射谱,分析了各参量对该结构1维光子晶体缺陷模的影响,并用波动理论定性分析了多通道滤波器形成的原因。结果表明,在各介质层的光学厚度绝对值都为0/4的情况下,每个禁带中都有n个超窄的透射峰,相邻两个透射峰间距比相同结构下正折射率情况的宽;当n=1时,随着C层介质光学厚度以0/4的k倍增加,透射谱中同一禁带内出现了k条透射峰;当n2时,透射谱中同一禁带内出现了nk条透射峰。该研究结果对可调多通道滤波器的设计和研究有一定的参考价值。     

基于石墨烯和1维光子晶体的THz宽带吸收器

为了获得宽带高效率光波吸收器,设计了石墨烯和1维光子晶体的复合结构,采用修正的传输矩阵法研究了其传输特性。结果表明,在一定条件下,复合结构在太赫兹波段具有一定带宽和高效率的吸收带,吸收带的位置和宽度与1维光子晶体通带一致;在一些特别的吸收带,吸收峰值达到1;对相同的结构吸收结果还与入射方向有关。石墨烯和1维光子晶体的结合进一步拓展了它们的应用范围。     

峰值折射率对正弦型函数光子晶体缺陷模的影响

为了分析峰值折射率对1维正弦型函数光子晶体缺陷模的影响,首先对折射率按正弦规律变化的介质进行离散化,然后应用传输矩阵法计算了1维光子晶体(AB)mC(BA)m的透射谱,分析了各介质层的折射率峰值对该结构1维正弦型函数光子晶体缺陷模的影响。结果表明,随着峰值折射率的增大,缺陷模红移,且频率越高缺陷模红移现象越明显;低折射率介质的峰值折射率对缺陷模频移的影响比较显著。这一结果对光子晶体的设计有一定的参考价值。     

Resonant coupling of near-infrared radiation to photonic bandstructure waveguides

Sharp resonance features are observed in the polarized reflectivity spectra of semiconductor photonic crystals fabricated by deep periodic patterning of AlGaAs surface waveguides. Both one- (1-D) and two-dimensional (2-D) lattices are studied by angular dependent reflectivity. By comparison with theory we show that the sharp features in reflectivity arise from resonant coupling of the external radiation to the folded band structure of the photonic crystal waveguides. Wavevector selective coupling to “heavy photon” states at the edge of the photonic Brillouin zone is demonstrated for the 1-D lattices. In the case of the 2-D lattices we observe polarization mixing of the photonic hands. Theoretical reflectivity spectra were obtained from a numerical solution of Maxwells equations for the patterned waveguide and were found to be in very good agreement with experiment     

Measurement of photonic mode dispersion and linewidths in silicon-on-insulator photonic crystal slabs

The dispersion of photonic modes in one-dimensional (1-D) and two-dimensional (2-D) patterned silicon-on-insulator (SOI) waveguides, also containing line defects, is fully investigated both above and below the light line. Quasi-guided (radiative), as well as truly guided modes are probed by means of angle- and polarization-resolved microreflectance and attenuated total reflectance measurements. For the 1-D case, the sharp resonances observed in reflectance spectra are analyzed in terms of the Airy-Fano model, and the measured linewidths are shown to be very close to theoretical predictions. In the 2-D lattices containing W1 line defects the presence of a supercell repetition leads to the simultaneous excitation of defect and bulk modes which are folded in a reduced Brillouin zone. The measured dispersion is in very good agreement with full three-dimensional calculations based on expansion on the waveguide modes, indicating that a deep understanding of the propagation properties of patterned SOI waveguides is achieved.     

Room temperature photonic crystal defect lasers at near-infraredwavelengths in InGaAsP

Room temperature lasing from optically pumped single defects in a two-dimensional (2-D) photonic bandgap (PBG) crystal is demonstrated. The high-Q optical microcavities are formed by etching a triangular array of air holes into a half-wavelength thick multiquantum-well waveguide. Defects in the 2-D photonic crystal are used to support highly localized optical modes with volumes ranging from 2 to 3 (λ/2n)³. Lithographic tuning of the air hole radius and the lattice spacing are used to match the cavity wavelength to the quantum-well gain peak, as well as to increase the cavity Q. The defect lasers were pumped with 10-30 ns pulses of 0.4-1% duty cycle. The threshold pump power was 1.5 mW (≈500 μW absorbed)     

Performance of waveguide-based two-dimensional photonic-crystalmirrors studied with Fabry-Perot resonators

As a step toward the use of photonic crystals in optoelectronic devices, we present a thorough study of 2-D photonic-crystal mirrors etched into a GaAs-AlGaAs planar waveguide. Fabry-Perot resonators are fabricated to deduce the reflectivity, transmission, losses, as well as the penetration lengths of these mirrors. The guided photoluminescence of InAs quantum dots embedded in GaAs is used to obtain the transmission spectra of these cavities. The varying thickness between the mirrors allows a scan across the whole bandgap spectral range. Quality factors (up to 200) and peak transmissions (up to 0.3) are measured showing that mirrors of four rows of holes have 88% reflectivity, 6% transmission and 6% losses. Losses are also related to a two-dimensional transfer matrix method calculation including a recently introduced scheme to account for losses