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Topological inverse design of fabrication-constrained nanophotonic devices via adaptive projection method: supplemental document

We demonstrate a new, to the best of our knowledge, dimensional “horizontal optimization” scheme, which can improve the high-speed characteristics of a PIN photodetector by designing the incident optical field distribution. First, coaxially incident faculae with the same peak and same power are studied and simulated, revealing that the bandwidth of the photodetector illuminated by uniform light is higher than that of the device illuminated by nonuniform light. Next, an annular optical field is designed incident to the photodetector, and the bandwidth is further improved. For a PIN photodetector, by carefully optimizing the incident optical field distribution, the photodetector bandwidth under an annular optical field can be increased significantly compared with that under conventional coaxial illumination.

A synchronous-traveling carrier photodetector (STC-PD) with a thick absorption region and large diameter is presented and investigated for 100 Gbps PAM4 applications. In the STC structure, a suitable electric field is introduced to synchronize the traveling of electrons and holes, which achieves high bandwidth while maintaining large responsivity. The characteristics of STC-PD, including electric field distribution, energy band diagram, responsivity, junction capacitance, and frequency response, have been studied carefully.

To investigate the association between non-syndromic cleft lip with or without cleft palate (NSCL/P) and environmental factors in Ningxia population.This case-control study involved 453 NSCL/P patients and 452 normal newborns from Ningxia. A questionnaire focusing on various factors, including family history, pregnancy reaction, drug use during pregnancy, and infections, was used and responses were analyzed through Chi-square test and Logistic regression analysis with SPSS 16.0.The constituent ratio of different types of NSCL/P was cleft lip∶cleft lip and palate∶cleft palate equal to 1︰2.02︰1.51. Logistic regression analysis revealed that abnormal pregnancy, infection, abortion, drugs, drinking, smoking, and living near factories likely increased the risk of NSCL/P (P0.05). Single fetus, pregnancy-related nausea, vomiting, parents' moderate tastes, and eating soy foods and fruits decreased the risk of NSCL/P (P0.05).The incidence of NSCL/P should be reduced to enhance the conditions of women during pregnancy by maintaining a balanced diet and avoiding infections, abortion, drugs, and negative habits. .目的 探讨宁夏地区非综合征型唇腭裂（NSCL/P）发病相关环境因素。方法 采用病例对照研究方法纳入NSCL/P患者453例，正常新生儿452例。对研究对象进行问卷调查，利用SPSS 16.0统计软件对数据进行卡方检验和Logistic回归分析。结果 NSCL/P患病类型构成比为唇裂︰唇裂合并腭裂︰腭裂=1︰2.02︰1.51。Logistic回归分析显示妊娠期发生异常、妊娠期感染、流产史、孕前孕中服用药物、饮茶、吸烟、饮酒、居住地附近工厂为危险因素（P0.05）。单胎、早孕反应、食用豆制品食物、水果为保护因素（P0.05）。结论 加强母亲孕期饮食均衡，避免感染、流产、服用药物以及不良生活习惯对降低NSCL/P的发生具有重要意义。.

In this paper we propose a prototype of the visible light communications system for long distance applications. Channel impairments are analyzed, and the design of the transmitter and the receiver is described. Experiments show the system works well at a distance of 10.7 Km at a data rate of 28.8 Kbps.

A novel slanted grating coupler is proposed and demonstrated for perfectly-vertical coupling between optical fibers and waveguides. It offers a coupling efficiency as high as 88.6% for TE polarizations at the wavelength of $1.55\ \mu\mathrm{m}$ .

A 1.55 µm nanoscale laser array is proposed and designed on v-groove patterned Si (0 0 1) substrates. The laser array is designed by taking full advantage of the periodic groove structures of the patterned substrates. The periodic groove structures separated by a SiO2 mask can effectively reduce threading dislocation density in the active region and provide a strong lateral optical confinement for the laser array structure. The optical mode distributions of the single laser are investigated in detail, and the optical confinement factor is calculated to optimize the structure parameters of the laser array. An optimal value of 9.3% for the optical confinement factor is obtained. The analysis of threshold conditions shows that the laser array can achieve lasing with a cavity length of about 1 mm for an internal loss of 40 cm−1.

Optical microcavity can confine light into a small volume by resonant recirculation. Devices based on optical microcavities are already indispensable for a wide range of applications and studies. They not only apply to traditional optics, but also have broad application prospects in quantum information and integrated optoelectronic chips. In quantum optical devices, microcavity can cause atoms or quantum dots to emit spontaneous photons in a desired direction or can provide an environment where dissipative mechanisms such as spontaneous emission are overcome so that quantum entanglement of radiation and matter is possible. For better application in quantum communication, optical microcavity needs to have a high quality factor and a low mode volume. Considering the beam coupling, spot shape and experimental production and others, the Fabry-Perot (F-P) microcavity has been widely applied to the field of optoelectronics. However, the Q-factor of the F-P microcavity is generally low, and the mode volume is large, so it needs to be improved.In addition, high Q-factor microcavity can also play a large role in detecting particles and biological macromolecules.In this paper, through the theory of wave optics, the eigenmodes of a new type of cone-top cylindrical optical micro-cavity are analyzed, and the resonant wavelength expression of the resonant cavity is obtained. We discuss the effects of the top mirror angle on the resonator performance and application of COMSOL simulation software to verify the proposed cone-top cylindrical microcavity. The optimized design and simulation results show that the quality factor of the new resonator can be increased by 22.4% to 49928.5 and the effective mode volume of the resonator can be reduced by 47.8% compared with the traditional parallel resonator. In this case, the corresponding new cavity length is 4.51 μm and the diameter is 3.13 μm. In this article its fabrications are also discussed.

The generation of a flat supercontinuum of over 80 nm in the 1550 nm region by injecting 1.6 ps 10 GHz repetition rate optical pulses into an 80-m-long dispersion-flattened microstructure fibre is demonstrated. The fibre has small normal dispersion with a variation smaller than 1.5 (ps.nm−1.km−1) between 1500 and 1650 nm. The generated supercontinuum ranging from 1513 to 1591 nm has the flatness of ±1.5 dB and it is not so flat in the range of several nanometres around the pump wavelength 1552 nm. Numerical simulation is also used to study the effect of optical loss, fibre parameters and pumping conditions on supercontinuum generation in the dispersion-flattened microstructure fibre, and can be used for further optimization to generate flat broad spectra.

A fully vectorial effective index method is developed for accurate dispersion calculation of photonic crystal fibres (PCFs). In order to improve the accuracy of the model, different values for the effective core radius are used when PCFs have different fibre parameters. The accuracy of our approach is demonstrated by comparing our results with other numerical and experimental results reported in literature. It is found that the accuracy of the fully vectorial effective index method is improved and our results agree well with accurate numerical results obtained by other methods as well as the previously reported experimental data.

A reflection-enhanced dual-absorption InP-PIN/GaAs-DBR photodetector was fabricated and characterized. The photodetector is monolithically integrated using a heteroepitaxy growth of an InGaAs/InP dual-absorption “PINIP” structure on the GaAs/AlGaAs Bragg reflectors. These features lead to an increase in quantum efficiency over a wide wavelength range while maintaining a high speed. The measured quantum efficiency was increased by 48.8% in comparison with that without reflectors. A quantum efficiency of 64% at a wavelength of 1522 nm and a 3 dB bandwidth of 26 GHz at a reverse bias of 3 V were simultaneously obtained in the device.

High-contrast-gratings reflector providing phase front control of transmitted light as well as high reflectivity is presented. The properties of the beam steering and transmission are numerically studied with the Finite Element Method (FEM). The results show that the reflectivity is 90.4% and the steering angle is 36.2510 degree which is very consistent with the theoretical 40 degree.

A dispersion-flattened photonic crystal fiber with normal dispersion is designed for generating flat wideband supercontinuum, and the supercontinuum generation in this fiber is numerically analyzed. The results show that by appropriately designing the photonic crystal fiber, it can achieve flattened dispersion in the normal dispersion region. It is found that a fiber characterized by a flattened dispersion with a small normal dispersion is suitable for a flat wideband supercontinuum generation. In the process of spectral broadening, self-phase modulation effect plays a dominant role. By filtering the supercontinuum, pulses with different central wavelength over a wide spectral range can be obtained. The pulse width is determined by the bandwidth of the filter.

Non-degenerate four wave mixing based on third-order susceptibility χ3 in high nonlinearity microstructure fibres is experimentally demonstrated. The Stokes and anti-Stokes peaks are observed simultaneously by launching 10-fs pulses from an 800 nm Ti:sapphire laser into the fibre.

In this paper, we study 3-point correlation function of primordial gravitational waves generated in the de Sitter background in the framework of the general covariant Ho��ava-Lifshitz gravity with an arbitrary coupling constant $��$. We find that, at cubic order, the interaction Hamiltonian receives contributions from four terms built of the 3-dimensional Ricci tensor $R_{ij}$ of the leaves $t = $ constant. In particular, the 3D Ricci scalar $R$ yields the same $k$-dependence as that in general relativity, but with different magnitude due to coupling with the $U(1)$ field $A$ and a UV history. Interestingly, the two terms $R_{ij}R^{ij}$ and $\left(\nabla^{i}R^{jk}\right)\left(\nabla_{i}R_{jk}\right)$ exhibit peaks at the squeezed limit. We show that this is due to the effects of the polarization tensors. The signal generated by the fourth term, $R^i_j R^j_k R^k_i$, favors the equilateral shape when spins of the three tensor fields are the same, but peaks in between the equilateral and squeezed limits when spins are mixed. The consistency with the recently-released Planck observations on non-Gaussianity is also discussed and is found that $\left(H/M_*\right)^2\left(H/M_{pl}\right) \le 10^{-8}$, where $M_{*}$ denotes the suppression energy of high-order operators, $M_{pl}$ the Planck mass, and $H$ the energy of inflation., revtex4, 16 figures. Version to appear in Phys. Rev. D

In this paper, we study the effects of parity violation on non-gaussianities of primordial gravitational waves in the framework of Ho��ava-Lifshitz theory of gravity, in which high-order spatial derivative operators, including the ones violating parity, generically appear. By calculating the three point function, we find that the leading-order contributions to the non-gaussianities come from the usual second-order derivative terms, which produce the same bispectrum as that found in general relativity. The contributions from high-order spatial n-th derivative terms are always suppressed by a factor $(H/M_*)^{n-2} \; (n \ge 3)$, where $H$ denotes the inflationary energy and $M_*$ the suppression mass scale of the high-order spatial derivative operators of the theory. Therefore, the next leading-order contributions come from the 3-dimensional gravitational Chern-Simons term. With some reasonable arguments, it is shown that this 3-dimensional operator is the only one that violates the parity and in the meantime has non-vanishing contributions to non-gaussianities., Revtex4, six figures

In this paper, we study non-Gaussianity generated by a single scalar field in slow-roll inflation in the framework of the non-relativistic general covariant Ho��ava-Lifshitz theory of gravity with the projectability condition and an arbitrary coupling constant $��$, where $��$ characterizes the deviation of the theory from general relativity (GR) in the infrared. We find that the leading effect of self-interaction, in contrary to the case of minimal scenario of GR, is in general of the order $\hat��_{n} ��^{3/2}$, where $��$ is a slow-roll parameter, and $\hat��_{n} (n = 3, 5)$ are the dimensionless coupling coefficients of the six-order operators of the Lifshitz scalar, and have no contributions to power spectra and indices of both scalar and tensor. The bispectrum, comparing with the standard one given in GR, is enhanced, and gives rise to a large value of the nonlinearity parameter $f_{\text{NL}}$.We study how the modified dispersion relation with high order moment terms affects the evaluation of the mode function and in turn the bispectrum, and show explicitly that the mode function takes various asymptotic forms during different periods of its evolution. In particular, we find that it is in general of superpositions of oscillatory functions, instead of plane waves like in the minimal scenario of GR. This results in a large enhancement of the folded shape in the bispectrum., Added new references and corrected some typos. 5 figures, revtex4. Phys. Rev. D86, 103523 (2012)

This paper introduced the principle of parallel prefix network (PPN) and proved the feasibility of applying PPN to differential quadrature phase-shift keying (DQPSK) precoder. Kogge Stone (KS) adder is a typical parallel algorithm of PPN. A ameliorated KS adder was proposed to implement the precoder. With 78Mb/s and 128 parallel channels, 20Gb/s DQPSK precoder was achieved in ML523 (Xilinx Virtex V FPGA). Results presented that the clock minimum period was 1.154 ns and the maximum frequency was 866.551 MHz. About 2% of slice logic resource was employed in the implementation.

In this paper, we investigate three important issues: stability, ghost and strong coupling, in the Horava-Melby-Thompson setup of the Horava-Lifshitz theory with $��\not= 1$, generalized recently by da Silva. We first develop the general linear scalar perturbations of the Friedmann-Robertson-Walker (FRW) universe with arbitrary spatial curvature, and find that an immediate by-product of the setup is that, in all the inflationary models described by a scalar field, the FRW universe is necessarily flat. Applying them to the case of the Minkowski background, we find that it is stable, and, similar to the case $��= 1$, the spin-0 graviton is eliminated. The vector perturbations vanish identically in the Minkowski background. Thus, similar to general relativity, a free gravitational field in this setup is completely described by a spin-2 massless graviton even with $��\not= 1$. We also study the ghost problem in the FRW background, and find explicitly the ghost-free conditions. To study the strong coupling problem, we consider two different kinds of spacetimes all with the presence of matter, one is cosmological and the one is static. We find that the coupling becomes strong for a process with energy higher than $M_{pl} |c_��|^{5/2}$ in the flat FRW background, and $M_{pl}|c_��|^{3}$ in a static weak gravitational field, where $|c_��| \equiv |(1-��)/(3 ��-1)|^{1/2}$., Comments on the analysis of strong coupling added. Title is changed. revtex4, 12 pages and no figures. To appear in Physical Reviews D

Trap bags were used to assess the presence of anArmillaria species in aPinus koraiensis plantation in Heilongjiang, China. 216 trap bags containing bark were placed in three plots at 2 × 2m spacing. After 10 weeks, the presence ofArmillaria was determined from the growth of rhizomorphs in the trap bags. The trap bag method proved successful in determining the presence of viableArmillaria rhizomorphs where only a few dead trees showed signs of the disease. The distribution of positive traps corresponded generally with the presence of rhizomorphs in the soil taken from the trap holes. However, the trap bags were superior to soil samples for evaluating the presence of viable rhizomorphs. The fresh, abundant rhizomorphs were easily identified by persons inexperienced in the assessmentof Armillaria root rot. Several practical problems need to be solved before the method is applicable in general forest management in China.

Two-dimensional subwavelength gratings (2D-SWGs) that consist of net-grid structure are studied by rigorous coupled-wave approach (RCWA) and finite-difference-time-domain (FDTD) method. 2D-SWGs can be designed as infrared reflectors whose reflectivity can reach 99.98% at 1.55µm while maintaining reflectivity higher than 99% across the 1.47–1.59µm wavelength range. We design these SWGs as the bottom mirrors in resonant cavity enhanced photodetectors (RCE-PDs) for optical communication system. Because SWGs can achieve high reflectivity as well as wide bandwidth, RCE PD's quantum efficiency is increased to 95.7% at 1.55µm and the device has a significant size reduction compared with using DBR bottom mirror.

SFP optical modules are widely used in the practical network, this paper proposes an application and realization of a monitoring system for SFP optical transceiver module. It analyses the basic principles of digital diagnosis monitoring function of the intelligent SFP optical modules first. Then it introduces the SFF-8472 protocol architecture and the basic principles of I2C bus. With the adoption of this system, the key parameters of optical transceiver module's monitoring can be realized. Moreover the testing results of the optical transceiver module base on this system are according to the requirements.

We systematically study the evolution of the Friedmann-Robertson-Walker (FRW) universe coupled with a cosmological constant $��$ and a perfect fluid that has the equation of state $p=w��$, where $p$ and $��$ denote, respectively, the pressure and energy density of the fluid, and $w$ is an arbitrary real constant. Depending on the specific values of $w,\; ��$, and the curvature $k$ of 3-dimensional space, we separate all of the solutions into various cases. In each case the main properties of the evolution are given in detail, including the periods of deceleration and/or acceleration, and the existence of big bang, big crunch, and big rip singularities. In some cases, errors in classification and interpretation appearing in standard textbooks have been corrected., revtex4, 24 figures

A new management framework of GMPLS protocol stack is proposed. On the basis of the requirement of intelligent optical network, we explore design scheme for the management model. Specially, the management model focuses on global topology discovery, point-to-point link management, fault management and link provision. Then the performance of the framework will be analyzed in the test-bed setup in our lab.

In this paper, polarization dependent characteristics of resonant cavity enhanced (RCE) photodetector (PD) with respect to the incident light angle were analyzed in detail. The simulations carry out on a 1.3μm GaInNAs quantum wells RCE PD, which is fabricated in our group. Analysis results show that the influence of polarization can only be neglected at small angle of incidence.

This paper discussed a novel resonant cavity enhanced (RCE) photodetector with a flat-top response, which is promising for WDM application. We analyzed and compared the response curves and crosstalks of the novel RCE and conventional RCE photodetectors, and the influences of the layer-thickness errors on the response curves of the flat-top response RCE photodetectors, and the dependencies of the flat-top RCE photodetector's response on incident angle and polarization were also given.

With PP and PE film as samples, the chemical groups, free radicals, micro pores and trap densities during the electrical ageing process in vacuum, air, and corona are measured in this paper. It is shown in test results that the variation of characteristic peaks of groups in the IR spectrum, and free radicals are similar to that of trap densities. It is suggested that trap densities can be used an an indication of electrical ageing degree in polymers. Finally, the mechanism of trap creation and ageing breakdown in polymers is discussed. >

In this paper, an InP-based mesa-structure uni-traveling-carrier photodetector is designed. By adopting Gaussian doping scheme in the absorption layer and incorporating an appropriate cliff layer, high speed and high saturation current characteristics are both achieved simultaneously. For the device with a 14 μm2 active area, the simulated results indicate that the bandwidth reaches 58 GHz and DC saturation current increases up to 158 mA at a reverse bias of 2 V. Under high optical injection, the bandwidth degradation and current saturation are studied, which are caused by energy band shift and electric field collapse.

A new approach to designing planar, high numerical aperture, low loss, focusing reflectors using circular subwavelength high contrast gratings is presented. Through analyzing particular physical scene, a mathematical transformation from existing “focus line” convergent beam, which can be achieved by bar grating reflector, to the convergent beam with a “focus point”, is obtained. By changing the shape of the bar grating reflector with the mathematical transformation obtained, a circular grating reflector, which can achieve “focus point” convergent beam, is obtained. The focusing properties and reflection characteristic of the circular grating reflector are numerically studied with the finite element method. After the radially polarized light reflected from circular grating reflector with a diameter of 29.788 μm, the beam will focus at 10 μm away from the reflector, resulting in a numerical aperture of 0.8302 and a reflectivity of 0.9163. In the focal plane, the numerical simulation results present a field distribution with a full width half maximum value of 1.5548μm, which is extremely close to diffraction limit.

To explain different doping effects in a buffer layer, thermally annealed interface, and upper epilayers of GaAs/Si films grown by Metalorganic Chemical Vapor Deposition (MOCVD), the behaviors of unintentional doping in GaAs/Si films are investigated in detail. A third doping mechanism of arsine impurity incorporation during the growth process of GaAs/Si films, apart from conventional mechanisms of gas phase reaction and diffusion from the silicon substrate, is proposed. The experimental results reveal that the doping behavior in the buffer layer studied is determined by the three types of doping mechanisms together. However in the thermally annealed interface and upper epilayers, the third doping mechanism is dominant. According to the third mechanism, the background carrier concentration in GaAs/Si films grown by MOCVD could be properly controlled through the arsine flow rate.

The fabrication of self-catalyzed InP nanowires (NWs) is investigated under different growth conditions. Indium droplets induced by surface reconstruction act as nucleation sites for NW growth. Vertical standing NWs with uniform cross sections are obtained under optimized conditions. It is confirmed that the growth rate of NWs is strongly affected by the surface diffusion adatoms while contributions from the direct impingement of vapor species onto the In droplets can be negligible. The results indicate that the droplet acts as an adatom collector rather than a catalyst. Moreover, the diffusion flow rate of adatoms increases with time at the beginning of growth and stabilizes as the growth proceeds.

Vertical p-type gallium arsenide (GaAs) nanowires with pure zinc blende structure were grown on GaAs (111) B substrate by metal-organic chemical vapor deposition via a Au-catalyst vapor-liquid-solid mechanism. The p-type doping was investigated by additional diethyl zinc (DEZn). In the high II/III ratio range (II/III>9.1%), there exists a critical length beyond which kinking takes place. Two possible reasons are discussed. Zn occurrence in the nanowires was verified by energy dispersive X-ray (EDX) analysis. Corresponding to II/III D 0.2%, the doping concentration is about 8 10 18 cm 3 .