摘要：
Based on the theoretical analysis of microbolometer thermoelectric characteristics and temperature response, a new kind of temperature compensation readout integrated circuit for microbolometric focal plane array is proposed. The proposed readout integrated circuit provides different bias voltages for different microbolometers to control their bias currents and allow the whole microbolometric focal plane array have a wide range of operating ambient temperature. This kind of readout integrated circuit can compensate not only the operating temperature fluctuation but also the thermoelectric-parameter nonuniformity for microbolometer array. Experimental results in our laboratory show that the microbolometric focal plane array on the basis of the proposed readout circuit has well uniform voltage responses of the microbolometers in the focal plane array at different ambient temperatures to the same microbolometric temperature change. The proposed temperature compensation readout integrated circuit is potential for the design of practical low-consumption and high-resolution microbolometric focal plane arrays without thermoelectric coolers.
摘要：
In this paper, a new high-voltage level shifter (HVLS) structure is proposed, which has a significantly improved transient response over existing structures. To overcome signal transfer delay of the conventional HVLS caused by parasitic capacitance due to high-voltage MOSFETs, this structure employs a novel circuit module "inverse Schmitt trigger" to drive the pull-up transistors of conventional HVLS. As a result, the "Miller Plateau" caused by parasitic capacitance can be minimized. Hence, the overall transfer delay of the structure is significantly reduced. The simulation results based on SPECTRE and 0.5 m high-voltage CMOS process show that compared to other currently available structures whose transfer delays are several nanoseconds on average, the proposed structure is able to provide a nanosecond transfer delay without using large boost capacitors which are impractical to be integrated or using complex logic units which decrease reliability of circuit. Also, the typical transfer delay of the proposed structure is a constant 1.3 ns, which is irrelevant to parasitic capacitance and insensitive to transfer voltage level.
摘要：
Control of light by light is a current research topic and is important for a variety of fundamental studies and practical applications. Here, we put forward a chip-scale scheme for all-optical control of small-signal photon transport and Fano-like lineshape in a coupled quantum-dot-pillar microcavity system based on a control-probe technique. Specifically, a bichromatic input light field, which consists of a weak probe field and a tunable control field, is applied to simultaneously drive the pillar cavity mode (called the control-probe technique) and both its reflectivity from and transmittivity through the pillar cavity constitute two output channels (i.e., a reflectivity signal channel and a transmittivity signal channel). We derive full analytical expressions for the reflectivity and transmittivity coefficients via a perturbation method. Using experimentally realistic parameters, theoretical analysis shows that the output probe light of the reflectivity and transmittivity channels can be switched on or off by simply turning on or off the control light field. Hence, the present system can be utilized to realize all-optical switching of the probe light by the control light with high switching contrast similar to 1 by means of these two output channels. Interestingly, the reflectivity channel and the transmittivity channel are complementary and offer versatile applications in a two-channel switching. In addition, it is shown that the strong asymmetric Fano lineshape can be generated by properly tuning the frequency of the control light field in this control-probe scheme. The present investigation may be used for developing novel all-optical switching and tunable Fano devices on-chip. Published by AIP Publishing.
作者机构：
[Lu, Lulu; Yang, Lijian; Jia, Ya] Cent China Normal Univ, Inst Biophys, Wuhan 430079, Hubei, Peoples R China.;[Lu, Lulu; Yang, Lijian; Jia, Ya] Cent China Normal Univ, Dept Phys, Wuhan 430079, Hubei, Peoples R China.;[Liu, Wangheng] Wuhan Polytech Univ, Sch Elect & Elect Engn, Wuhan 430023, Hubei, Peoples R China.
通讯机构：
[Jia, Ya] C;Cent China Normal Univ, Inst Biophys, Wuhan 430079, Hubei, Peoples R China.;Cent China Normal Univ, Dept Phys, Wuhan 430079, Hubei, Peoples R China.
摘要：
We study the time evolution of the populations in a two-dimensional (2D) graphene system by employing a few-cycle laser pulse with a linear polarization. Specifically, we present a comparative numerical analysis of the population dynamics of graphene in three different model configurations. Our results show that the Rabi-like oscillations and intraband population inversion can be observed in the population spectrum, which originated from the periodicity of a few-cycle laser pulse and the intraband Coulomb scattering. Also, coherent population oscillations are produced across the Dirac point when the Rabi frequency of the laser field which is used to couple the interband transition is much larger than that couples the intraband transition, and vice versa. These investigations may be helpful to enhance the performance of graphene-based ultrafast electronic and optoelectronic devices, including light-emitting devices, touch screens, photodetectors, and ultrafast lasers.
摘要：
We explore the possibility of using an active doubly resonant microtoroid resonator to produce high-efficiency third-harmonic generation (THG) by exploiting optical third-order nonlinearity. In a microresonator, the active fundamental mode is coherently driven with a continuous-wave input laser at the telecommunication wavelength (1550 nm), and then, the visible THG signal (517 nm) is monitored via an individual bus waveguide. We thoroughly compare our results with those obtained from the conventional passive (i.e., loss) microtoroid resonator by a systematic analysis and detailed numerical simulations based on the Heisenberg-Langevin equations of motion. It is shown that the achievable THG spectrum features an ultralow critical input power. The THG power transmission can be significantly enhanced by about three orders of magnitude at a low input power of 0.1 μW as compared with the obtained results in the passive microtoroid resonator THG system. Moreover, the THG efficiency can reach up to 100% with optical critical input power as low as a few microwatts. In turn, the analytical expressions of the critical intracavity intensity of the light in the microcavity, the critical input pump power, and the maximum THG efficiency are obtained. The enhanced THG power transmission and high conversion efficiency are attributed to a gain-induced loss compensation in the microtoroid resonator, reducing the effective loss felt by the resonator photons. With state-of-the art technologies in the field of solid-state resonators, including but not limited to microtoroids, the proposed THG scheme is experimentally realizable.
关键词：
BaTiO3 film;Surface effect;Dielectric;Curie temperature;Depolarization field
摘要：
The influence of the surface effect on the ferroelectric property of strained barium titanate film has been investigated. In this study, based on time-dependent Ginsburg-Landau-Devonshire thermodynamic theory, the surface effects have been simulated by introducing a surface constant, which leads to the strained BaTiO3 film consisting of inner tetragonal core and gradient lattice strain layer. Further, surface effects produce a depolarization field which has a dominant effect on the ferroelectric properties of the films. The spontaneous polarization, dielectric properties and ferroelectric hysteresis loop of BaTiO3 film are calculated under different boundary conditions. Theoretical and experimental results for strained BaTiO3 film are compared and discussed.
摘要：
Non-stoichiometric hydrogenated amorphous silicon carbide thin films (α-SiC:H) were deposited by plasma-enhanced chemical vapor deposition. The samples were subsequently post-annealed at 750, 900, 1050, and 1200 °C, respectively. Photoluminescence (PL) was measured by fluorescence spectrometer at room temperature. Infrared absorption was carried out by Fourier transform infrared absorption. Chemical compositions were analyzed by X-ray photoelectron spectroscopy. The synthesis of silicon quantum dots (Si-QDs) was characterized by Raman scattering spectroscopy and directly by high-resolution transmission electron microscope. PL measurements revealed that there were complicatedly shifted sub-bands upon the thermal annealing temperature increase. The behaviors of these shifted sub-bands showed converse trends as that of the local SiC bonding densities. A possible influence for the PL by the evolvement of the local SiC bonding densities and the synthesis of Si-QDs in the α-SiC:H samples is supposed.
摘要：
Occlusion is one of the most challenging problems in visual object tracking. Recently, a lot of discriminative methods have been proposed to deal with this problem. For the discriminative methods, it is difficult to select the representative samples for the target template updating. In general, the holistic bounding boxes that contain tracked results are selected as the positive samples. However, when the objects are occluded, this simple strategy easily introduces the noises into the training data set and the target template and then leads the tracker to drift away from the target seriously. To address this problem, we propose a robust patch-based visual tracker with online representative sample selection. Different from previous works, we divide the object and the candidates into several patches uniformly and propose a score function to calculate the score of each patch independently. Then, the average score is adopted to determine the optimal candidate. Finally, we utilize the non-negative least square method to find the representative samples, which are used to update the target template. The experimental results on the object tracking benchmark 2013 and on the 13 challenging sequences show that the proposed method is robust to the occlusion and achieves promising results. (C) 2017 SPIE and IS&T.
摘要：
One of the current challenges in second-harmonic generation (SHG) is to increase the efficiency of the second-harmonic conversion process while maintaining or even decreasing the fundamental-harmonic pump powers in a compact device. Here, we put forward an on-chip scheme to realize high-efficiency optical SHG in active-passive-coupled microring resonators with the aid of the intrinsic second-order nonlinearity. By careful analysis and extensive simulations, it is found that the introduction of an active microring resonator makes the strong SHG process feature an ultralow-power pump threshold, which is about four orders of magnitude lower than that in a single-microring resonator SHG system reported previously by X. Guo et al. [Optica 3, 1126 (2016)]. The observed SHG is enhanced by a factor of over 200 compared to the single-microring-resonator SHG system. The SHG conversion efficiency of over 72% can be reached with optical pump power as low as a few microwatts for our proposed device. This investigation may open a new route towards development of easily fabricated radiation sources of coherent high-energy (shorter-wavelength) photons with an ultralow-power laser-triggered SHG process.
摘要：
Based on the fundamental principle of target radiation and microbolometer infrared detection, the microbolometric temperature response to infrared-target temperature change is theoretically analyzed and an exact microbolometric temperature response expression is obtained in theory. The theoretical expression is verified in our laboratory and can be utilized to correct the conventional temperature response expression. Moreover, the theoretical expression can predict temperature change in microbolometer to target temperature and guide the design of electronic-respond-signal processing circuits.
关键词：
Grounded inductor simulator;Floating inductor simulator;Active inductor;CMOS integrated circuits;MOSFET;Operational frequency
摘要：
In this paper, an improved inductor simulator structure is presented, which can be configured as either grounded or floating inductor simulator with low component count. To achieve simplified structure, inductor simulator circuits are designed using a minimal number of transistors and small capacitance, rather than the complex components/modules such as current convey and operational trans-conductance amplifier which are traditionally used. The simulation results based on
$$0.5\, \upmu \hbox {m}$$
CMOS process parameters show that the proposed structure is able to produce a broad range of inductance values and compared to other similar structures, it provides wider operational frequency bandwidth for the same or comparable inductance value. Furthermore, the structure can be implemented with much smaller chip area using a small capacitance in the circuit, but at the price that it has a higher minimum operational frequency compared to other structures.
摘要：
The temperature dependence of dc magnetization is investigated for the rare earth chromites SmCrO
$$_{3}$$
and the doped compound SmCr
$$_{0.9}$$
Mn
$$_{0.1}$$
O
$$_{3}$$
. Different from the magnetization behavior of SmCrO
$$_{3}$$
, temperature-induced magnetization reversals are observed in the Mn
$$^{3+}$$
-doped compound. Moreover, low-temperature isothermal magnetization measurement indicates the magnetic ground state of SmCr
$$_{0.9}$$
Mn
$$_{0.1}$$
O
$$_{3}$$
to be antiferromagnetic with a spin canting. The field-cooling magnetic hysteresis loop reveals that an exchange bias (EB) phenomenon is present in the sample. The reversal of magnetization and the corresponding EB field is discussed on the basis of the competitive interaction between the antiferromagnetically coupled Cr-rich clusters and Cr–Mn ordered clusters.
摘要：
Based on the analysis of the physical thermal model for a microbolometer under pulse bias, a new temperature compensation method for microbolometric focal plane array is proposed to compensate the substrate temperature fluctuation in microbolometric array. The self-heating and infrared responding voltage expressions of the microbolometer under pulse current bias are derived from the heat balance equation of the physical thermal model for the microbolometer, and these two expressions indicate that the microbolometer self-heating and infrared voltage responsivity expressions are dependent on the substrate temperature of the microbolometer with some other constant characteristic parameters. Through the obtained expressions, different pulse bias currents are provided to the microbolometer and its corresponding blind element at different substrate temperatures to get the same voltage responsivity of the microbolometer at different ambient temperatures. The proposed temperature compensation method can be utilized for a microbolometric focal plane array with low-power consumption and high temperature-resolution.
摘要：
Silicon quantum dots (QDs) embedded in non-stoichiometric hydrogenated silicon carbide (SiC:H) thin films have been successfully synthesized by plasma-enhanced chemical vapor deposition and post-annealing. The chemical composition analyses have been carried out by x-ray photoelectron spectroscopy (XPS). The bonding configurations have been deduced from Fourier transform infrared absorption measurements (FTIR). The evolution of microstructure with temperature has been characterized by glancing incident x-ray diffraction (XRD) and Raman diffraction spectroscopy. XPS and FTIR show that it is in Si-rich feature and there are a few hydrogenated silicon clusters in the as-grown sample. XRD and Raman diffraction spectroscopy show that it is in amorphous for the as-grown sample, while crystalline silicon QDs have been synthesized in the 900°C annealed sample. Silicon atoms precipitation from the SiC matrix or silicon phase transition from amorphous SiC is enhanced with annealing temperature increase. The average sizes of silicon QDs are about 5.1 nm and 5.6 nm, the number densities are as high as 1.7 × 1012 cm−2 and 3.2 × 1012 cm−2, and the crystalline volume fractions are about 58.3% and 61.3% for the 900°C and 1050°C annealed samples, respectively. These structural properties analyses provide an understanding about the synthesis of silicon QDs upon thermal annealing for applications in next generation optoelectronic and photovoltaic devices.
