A single photon avalanche diode designed with 0.18um CMOS technology is proposed, with which the weak light in 650~950nm wavelength can effectively detected. The single photon avalanche diode employs a P+/N-well structure, the deeper P+ layer is designed to improve the photon detection efficiency and responsivity in longer light wave; moreover, the increase of the thickness of depletion layer can be got with the use of the low doped deep N well, which can improve the detection sensitivity, and the PN junction formed by deep N well and substrate can effectively isolate substrate in order to reduce substrate noise. The use of P-well as the protection ring can prevent premature edge breakdown phenomenon. The basic structural parameters and process parameters of single photon avalanche diode devices are determined by theoretical analysis, and the device performance is optimized with Silvaco TCAD software. The simulation results show that when the optical window diameter of the device is 10 μm, the avalanche breakdown voltage is 18.4 V, with the illumination of 0.001 W/cm2, the peak of response is of 0.495 A/W at 650 nm will be got. when the reverse bias is excessed the breakdown voltage for 2 V, in the range of 650~950 nm wavelength, the photon detection efficiency is higher than 30%. With the increase of reverse bias, the detection efficiency is improved.
To balance the carrier injection in Quantum Dot Light Emitting Diode (QLEDs), a method to determine the thickness of each functional layer was proposed. The thickness of EL was set firstly, the thickness of Electron Transport Layer (ETL) was determined through tunneling model. On this basis, the thickness of Hole Injection Layer (HTL) was determined at last using space charge limited current model. Devices using red light CdSe/ZnS quantum dot was used as the Light-Emitting Layer (EL), poly-TPD as the HTL, Alq3 as the ETL were fabricated through spin-coating and vacuum evaporation with the thickness of each layer obtained from the simulation results. Experiment results show that compared with other devices, the device with a 45 nm thickness of poly-TPD, 25 nm QDs and 35 nm Alq3 has a higher luminous efficiency and color purity. QLEDs with the thickness of each layer chosen according to the method proposed have a more balanced carrier injection which is advantageous in improving device performance.
An arrayed waveguide grating,which is applied to IEEE 200/400 GbE standard 802.3 bs, is designed and manufactured. The arrayed waveguide grating uses the silica-on-silicon material, which has 2.0% ultra-high refractive index difference, making the less chip size and insertion loss. In addition, in order to obtain a flattened receiving spectrum, the output waveguides are widened and the multimode waveguide structures are used to excite a few of higher order modes. Several patterns are overlaid so that the top of the original Gaussian spectrum is flattened and forms a box-like receiving spectrum. At last, the designed center wavelength of the arrayed waveguide grating is 1 291.10 nm, the channel spacing is 800 GHz, and the device size is 11 mm×4 mm. The microchip is manufactured by plasma enhanced chemical vapor deposition and inductively coupled plasma etching. The test results show that, the minimum insertion loss is about -3.3 dB, the crosstalk between adjacent channels is less than -20 dB, and the single channel 1 dB bandwidth ranging from 2.12 nm to 3.06 nm, realizing a good wavelength demultiplexing and flattening effect, and having a certain practical value in the actual optical communication system.
Based on the application requirements of differential absorption lidar for atmospheric CO2 concentration detection, a single-resonant KTP crystal optical parametric oscillator, pumped by a 1 064 nm single-longitudinal-mode laser, was built with stable ring-cavity and mode matching design, and nanosecond laser pulse output at 2.05 μm wavelength was achieved with high slope conversion efficiency. In the stable ring cavity with a bow-tie configuration, two KTP crystals with type II phase-match condition cut were placed in walk-off-compensated arrangement. When the pump pulse energy reached 11 mJ at a repetition rate of 20 Hz, 2.4 mJ of laser pulse energy output at 2.05 μm signal wavelength was obtained with pulse width of around 24 ns, and the corresponding slope efficiency was 53%. The 2.05 μm signal laser beam quality factor in x and y directions were 1.3 and 1.2 respectively.
A reflective-type infrared filter is proposed based on a two-dimensional periodic micro-structure of circular aluminum disc-circular silica disc-aluminum substrate. Its infrared spectral reflectance is numerically simulated by finite element method. The simulated results show that this micro-structure exhibits excellent spectral filtering over 4~11 μm spectral range which is tunable, insensitive to TE or TM polarization and incident angles over 0 to 60°. The extraordinary infrared reflectance is deciphered with the plasmon polariton resonance theory, upon which a multilayered nanoring structure is proposed for further tuning to longer wavelengths and better absorption efficiency.
According to the diurnal variation of color temperature and brightness of sunlight, a strategy was proposed to simulate the diurnal variation of color temperature and brightness of sunlight by light mixing of RGBW-LEDs, and the genetic algorithm was used to optimize the color rendering index. The simulation was conducted by Matlab, and the simulation results were validated by the sunlight simulation system based on the Arduino open source platform. The experiment shows that using mixed light based on RGBW-LEDs can accurately simulate the change rule of sunlight' color temperature and brightness, and make LED mixed light have the optimal color rendering property through the optimization of genetic algorithm, so that the correctness and effectiveness of the proposed strategy were verified. The sunlight simulation strategy can be applied to the field of solar simulation and engineering practice for special lighting fields, such as enclosed environment lighting and plant lighting and so on.
There is no useful diagnostic technique to measure the shock wave for the target asymmetry in early implosion without extra processing to black cavity and target during the study of laser inertial confinement fusion. The two-axis velocity interferometer system for any reflector was developed based on Shenguang-III prototype laser facility and the experimental results were introduced. Velocity history of shock wave in equatorial and polar of target was obtained by installing small mirror in the target. According to the reflectivity of the material and the influence by the X ray, it is determined that Al is the suitable material for the mirror at present. The difference between the plane shock loading and spherical shock loading was compared. It is found that the accurate for target equipment is the main reason for fewer signals. The diagnostic technique of two-axis velocity interferometer system for any reflector was explored through the experiment, which would give a reference to develop the two-axis velocity interferometer system or multi-axis velocity interferometer system.
A custom quartz tuning fork which is 5 times larger than commercial standard quartz tuning fork and operated at the 1st overtone resonance mode was used and optimized to improve the sensitivity of the quartz-enhanced photoacoustic spectroscopy spectrophone. The optimum ecxiting position for the laser beam was researched. Two resonance antinodes were found in the 1st overtone resonance, and the maxium signal amplitude was obtained at a distance of 8 mm from the tuning fork support. Acoustic micro-resonantors with three different inner diameters were configured with the custom tuning fork to evaluate the performance of the quartz-enhanced photoacoustic spectroscopy spectrophone. With an optinal parameters, a sensitivity gain factor of 30 was achieved with respect to the signal amplitude obtained by the bare tuning fork without acoustic micro-resonantors.
A novel X-ray backlighting imaging Bragg spectrometer was developed based on the Bragg diffraction theory to study and diagnose the driven symmetry and uniformity of laser radiation, analyse the promote layer motor process of target implosion of Inertial Confinement Fusion. The key component of the imaging system was the spherically bent Quartz Bragg crystal. The imaging simulation of the X-ray backlighting imaging Bragg spectrometer was studied with the ray tracing software SHADOW. The monochrome X-ray backlight imaging experiment using spherically bent Quartz Bragg crystal was used to carried out in the Chinese Academy of Engineering Physics. The imaging plate was obtained the two-dimensional, monochromatic backlight mesh imaging. By analyzing the imaging information of the experiment, the spatial resolution of the imaging Bragg spectrometer was 83 μm. The experiment show that the imaging system was adequate for X-ray backlighting imaging diagnosis..
An electro-optic cavity-dumped 1064 nm solid state laser with short pulse duration and high peak power at 1 kHz repetition rate was proposed. The Nd:YAG crystal was side-pumped by an 808 nm pulsed laser diode in a folded biconcave cavity. Transverse voltage addition cavity dumping mechanism realized with a synchronously delayed MgO:LN crystal was used to generate laser pulses. Output pulses with maximum pulse energy and peak power up to 46.7 mJ and 11.5 MW were obtained, corresponding to 200 Hz repetition rate and 4.06 ns pulse duration at 1 064 nm. Peak to peak instabilities of pulse width and pulse energy were ±1.52% and ±2.02%. At the highest repetition rate of 1 kHz, the measured pulse energy, peak power and pulse duration were 18.3 mJ, 3.69 MW and 5.02 ns. Peak to peak instabilities of pulse duration and pulse energy were ±2.75% and ±3.52%, corresponding to the beam quality factors of 3.849 and 3.868, far field divergence angles of 3.46 mrad and 3.55 mrad, and waist spot diamete of 1 508.84 μm and 1 477.30 μm respectively.
A low threshold nanolaser that contains nanowires, air gap and semicircular-top metal nanoridge structure was proposed.Through the finite element method to model characteristics and the quality of the laser gain factor and threshold for numerical calculation, the characteristic factor was studied with the geometric parameters (air gap, metal ridge width and nanowire radius) change. The results show that the property of the laser is optimized by adjusting the parameters. Under the optimal parameters, the gain threshold can reach 0.47 μm-1 and the transmission loss is only about 0.018. This shows that the nanolaser structure can achieve low threshold sub wavelength lasing and low loss transmission. It has a wide application prospect in the fields of biomedicine, optical communication etc. It provides technical support for miniaturization and integration of nano devices.
An ultrashort cavity single-frequency Distributed Bragg Reflector (DBR) laser operating at 1064 nm was proposed with a cavity length of 2 cm, and the gain medium is a 1.1 cm long highly Yb-doped silica fiber. With a proper temperature control, the stable single-frequency laser with a linewidth of 4.8 kHz was achieved. The maximum output power of the DBR fiber laser is 13 mW with a slope efficiency of 3.4% relative to the launched pump power of 378 mW. The measured relative intensity noise is about -132 dB/Hz at frequencies of over 1 MHz. The master oscillator power-amplifier structure was used to amplify the output power of the DBR laser. When the length of the amplification gain laser is given as 56 cm, the output power is scaled up to 325 mW with a slope efficiency of 52.8%.
A structure was designed that a 10m thulium-doped fiber is cascaded to 3 m large-mode-area photonic crystal fiber, and soliton self-frequency shift was generated by a 400 fs, 1 550 nm light pulse. At the same incident power, solitons in thulium-doped fiber experience more frequency-shift than that in large-mode-area fiber by 100-150 nm (30% on the average). Output spectra of soliton and pump at the end of thulium-doped fiber show that the stimulated radiation from Tm3+ is generated among 1.8-2.1 μm by residual pump, which results in greater Raman effect and cause the soliton self-frequency shift enhanced. The findings reveal a way to enhance soliton self-frequency shift, and have significance on extension of tunable range of laser based on soliton self-frequency shift.
Er3+ and Pr3+ co-doped AlN thin films were prepared by ion implantation, luminescence properties were characterized via cathodoluminescence spectrometer. For Er3+ doped AlN thin films, 410 and 480 nm peaks with higher intensity were observed, and there were other weaker peaks observed at 537, 560, 771, and 819 nm. For Pr3+ doped AlN thin films, 528 nm peak with higher intensity was observed, and there were other weaker peaks observed at 657 and 675 nm. However, for Er3+ and Pr3+ co-doped AlN thin films, a new luminescence peak at 494 nm was observed and was attributed to Pr3+. According to the experimental results, the energy transfer mechanism between Er3+ and Pr3+ in AlN thin films were investigated, the results show that resonant energy transfer exists between 4F7/2→4I15/2of Er3+ and 3P0→3H4 of Pr3+, which results in the new 494 nm luminescence peak of Pr3+
The optical properties of self-assembled bilayer InAs/GaAs quantum dots (QDs) are investigated by photoluminescence (PL) and time-resolved photoluminescence (TRPL) as a function of the GaAs spacer thickness. First,the PL spectrum change with excitation intensity are investigated,the variation of PL intensity ratio between the seed layer of QDs (SQDs) and the top layer of QDs (TQDs) with respect to the excitation laser intensity reveals that the coupling and subsequently the interlayer carrier transfer between the two layers of QDs decreases with increasing the GaAs spacer thickness. Then, the temperature-dependent PL behaviors, in measurement of the peak energy (Emax), linewidth (Full Width of Half Maximum, FWHM), and the integrated intensity of QDs, show that the GaAs spacer thickness strongly affect the dynamics and the thermal quenching process of carrier in the bilayer QD structrures. At last,TRPL measurements show that the carrier tunneling time of the 60ML spacer QD sample is significantly longer than that of the 40ML spacer QD sample.
SiO2 films are deposited on Si and sapphire (α-Al2O3) substrates by Dual Ion beam sputtering method. The microstructure, surface morphology, residual stress and optical stability of SiO2 coating in the wavelength of 0.4~1.2 μm and 3~5 μm are investigated, systematically. The results indicate that the residual stress goes through a local minimum value at ~400 ℃. There is a close relationship between the optical constant and the surface conditions, residual stress, microstructure of SiO2 film. As the temperature increases up to 1 000 ℃, SiO2 film can keep well thermal stability without notable damage morphology. The result can give some guidance for designing the optical coatings used in harsh environments.
A Plasmon-Induced Transparency (PIT) metamaterial was proposed comprised of a graphene patch and two pairs of split ring resonators (SRRs) symmetrically. The coupled PIT molecule is termed as dark-bright-dark molecule. By using the finite element method simulation, the PIT metamaterial exhibits double sharp-induced transparency peaks was observed. the PIT windows can be dynamically modulated at the terahertz regime by tuning the Fermi energy in graphene and varying the geometric parameters of the metamaterial. Theoretical calculations show thatthe interaction distance between graphene and two pairs of symmetrically SRRs is 0.5 microns and the graphene Fermi level is 1.5 eV, the optimal double transparent window is obtained.The PIT effects may have some potential applications in nonlinear devices, tunable sensors, switches, and slow light devices.
The electronic structures and the absorption spectra of the Cu and Mn mono and co-doped LiNbO3 crystals were investigated by first-principles based on the density functional theory. The results show that the impurity energy levels of Cu and Mn doped LiNbO3 crystals appear within the band gaps, which are contributed by Cu 3d orbital and Mn 3d orbital. The band gap of each doped crystal is narrower than that of LiNbO3 crystal. There are three absorption peaks at 2.87 eV, 2.24 eV and 1.73 eV respectively in Cu:Mn:LiNbO3 crystal. The first one and last one come from the electron transitions from Cu2+ and Mn2+ level to conduction band respectively. The second one is not photorefractive and relative with the concentrations of Mn3+. Comparing with the Cu:Fe:LiNbO3 crystal, the recording center (Cu2+) is deeper in Cu:Mn:LiNbO3 crystal. In the two-center holographic recording, it is practicable to take suitable higher concentration of Cu ion in Cu:Mn:LiNbO3 crystal to raise the dynamic range and sensitivity via enhancing the refractive-index change. The selecting of accompanying doping ion would affect the storage parameters, even if the recording center ion (deep level) is the same, so it's necessary to select codoping ions according to the simulating datum of the different samples.
In order to reduce the impact of the chronic spectral deformation on TDLAS gas analyzer accuracy, a transfer and restoration method was proposed. By comparing the real time spectra with the calibration spectra for validation gas, the deformation coefficient is obtained. The process gas spectra share the same deformation mechanism with the validation gas. So the process spectra can be restored to the calibration state due to deformation transitivity. Consequently analyzer maintains the original fidelity. It solves the tough issue of spectra restoration for dynamic process gas. It requires no adjustment of hardware parameters of optical or electronics system. The spectra are restored through signal filtering, feature extraction and deformation coefficients calculation. In the simulation, the similarity measure maintained 99.999% between calibration spectra and restorated real time spectra. For the experimentally acquired CO2 gas spectra with different levels of deformation, the similarity measure maintained 99.9% between target spectra and real time spectra with Lagrangian interpolation restoration.
A measurement system for on-line determination of optical properties of tissue with large areas and correction of complex surface profile was developed. First, the three-dimensional surface profile of the tissues was obtained with phase profilometry. According to cosine radiator model, the change of illumination, which was caused by complex surface profile of the tissues, was corrected. Then, diffuse plane was used to replace the phantom in the traditional method, and the absolute optical parameters based on spatial frequency domain measure mode were measured. The absorption coefficient of the tissues was reconstructed using the developed method. Tissues phantoms with height variation less than 29 mm were adopted to verify the method, the relative error of absorption coefficient decreased from 60% to 13% compared to that without correction.
Aimed at the important indicator of deep displacement in landslide body, based on the optical time domain reflection technique, a composite optical fiber transducer was designed to monitor the deep shear displacement. The transducer is composed of square PVC pipe, capillary pipe, optical fiber and mortar. Firstly, the surrounding of 40 mm×40 mm×500 mm (2.0 mm thick) PVC tube was grooved, and the Φ1×500 mm steel capillary was placed in the guide groove. Then the fiber was used to penetrate capillary tube. One end of the optical fiber was fixed, and the other end was wound into a bow form. At last, the mortar with diameter of 110 mm was poured outside PVC, so that a cylindrical composite optical fiber transducer was fabricated. The slope model shear test experiment shows the transducer detection accuracy is 1 mm and the maximum measurement range of fiber grating is 40 mm. Study shows that the composite optical fiber transducer has the advantages of high sensitivity, wide measuring range and convenient installation, and can be used for in-situ landslide monitoring and geotechnical engineering structure monitoring effectively.
Using the fundamental absorption band at the wavelength of 4.25 μm of carbon dioxide molecule, a differential mid-infrared carbon dioxide detection system was developed. The optical part of the system includes infrared thermal emitter, dual-channel pyroelectric detector and spherical mirror and the circuit part mainly consists of signal-processing, source-driving and main-control module. Simulating and optimizing the structure of the gas cell by using Tracepro software, eventually, the optical path of the gas absorption reaches 30 cm, and the performance of the system is improved. Preparing standard carbon dioxide gases with different concentration and investigating the sensing characteristics of system on carbon dioxide gas. Experimental results indicate that, the error between the measured concentration which are obtained by fitting curve and actual concentration is small, in the range of 0~5 000 ppm, the standard deviation of the measured concentration is less than 45 ppm, and that is less than 5 ppm under 500 ppm; the standard deviation of 2 hours long-term measurement concentration on the 0 ppm is about 2.8 ppm; the 1σ theoretical limit of detection obtained from the Allan variance is 2.5 ppm. Finally, each carbon dioxide sensor becomes a sensor node by adding wireless module nRF24L01 on each carbon dioxide sensor. Building a wireless sensor network in the chosen greenhouse. We have collected the carbon dioxide concentration and verified the performance of the developed sensor by filed application.
A miniature wearable Raman spectroscopy system used to achieve noninvasive detection of human blood glucose level was developed. A thallium-doped grin lens was employed as the collection lens and a specially designed wearable fiber optic probe was employed to help the stable and convenient collection of Raman spectrum. The glucose solution, 11 rats and 10 healthy human were studied as subjects. In addition, a method of quantitative analysis of Raman spectrum was proposed which using the peak area as the main reference factor while the peak intensity as the auxiliary reference factor to calculate the target concentration. A non-linearized multivariate dominant factor-based partial least squares model was built for different samples to predict glucose level. The results show that the accuracy are 98.1%, 89.3% and 84.4% for glucose solution, rats and human subjects. The system has the advantages of more compact structure, lower cost, better testing stability and convenient for human body to wear, and is feasible and repeatable to achieve the noninvasive detection of human blood glucose accurately.
To enlarge the depth of field of single-lens system, discrete spectral illumination approach based on imaging dispersion was proposed. Firstly, the relation between object distance and illuminating wavelength were theoretically derived. Next, numerical simulation using ZEMAX indicates high-resolution images at various focal planes was obtained via an optimized illumination system with corresponding spectral light sources, and the simulation results were consistent with the theoretical analysis. Finally, an image acquisition system using biconvex lens was designed for practical measurement, and a biconvex len with focus of 35 mm was used to experiment. The results show that compared to monochromatic illumination and white light, the depth of field of proposed method is increased respectively by 93.6% and 81.8%, and the resolution ratio is improved by 189.7% and 200.3%.
Varied with some optical parameters, such as center wavelength, power, the differential reflectance spectroscopy of unintentionally doped high-purity n-type gallium arsenide were studied by femtosecond laser pump probe technique. These time-resolved differential reflective spectroscopy further analyzed the dynamics of photo-induced carrier of gallium arsenide at room temperature. Firstly, if the pump and the probe power were stabled at 100 mW and 10 mW respectively, the peak differential reflectivity increases with the red shift of center wavelength, and the signal-to-noise ratio increases as well. Secondly, Based on the fitting experimental data of varying pump power and the theoretical model, it is found that there is a linear correlation between the pump power and the differential reflectance in a certain range, through which the saturated carrier concentration of this gallium arsenide sample was calculated as (3.590 1±0.310 3)×1017 cm-3. Thirdly, the dynamics process of photo-induced carriers is divided into three terms: the photo-excitation process (804±67 fs), the initial scattering process (134 ~268 fs), the recombination process with 1 picosecond and 3~6 ps. Last but not least, it seems that the differential reflectance has no significant dependence on the probe power, but the signal-to-noise ratio of the differential reflectance spectrum is correlated with the probe power. In a word, this work not only investigates the ultrafast dynamics of unintentionally doped high purity n-type gallium arsenide, which provides a reference for other materials, but also offers the optimal experimental parameters of pump-probe spectroscopy.
The ultrafast excited state relaxation dynamics of all-trans-Astaxanthin (AXT) in Dimethyl Sulfoxide (DMSO) was investigated using femtosecond time-resolved transient absorption and multiplex transient grating spectroscopies. The results reveal that the S0→S2 absorption transition directly occurs in the AXT/DMSO system, which corresponds to the ground state bleach in the 420~550 nm spectral region. Internal conversion that is ascribed to S2→S1 transition takes place on the time constant of 120~160 fs. The excited state absorption of the S1 state corresponds to the region of the 550~740 nm. The recovery progress of the ground state bleach corresponds to the internal conversion progress, which is attributed to the S1→S0 transition and occurs on the time scale of 4.50~5.50 ps.
In order to overcome the convolutional perfectly matched layer's shortcoming of the poor absorption effect on evanescent wave in the finite difference time domain algorithm, a method of adding special absorption layer after convolutional perfectly matched layer was proposed. Without increasing the distance between the object and the inner layer of the absorbent layer, the decay factors in the special absorption layer were adjusted to make them constants and the absorption factor was increased from 1 to 10 to enhance the absorption layer's absorption performance to the evanescent wave. An example in which the plane wave is incident vertically to the single-layer photonic crystal shows that the absorption boundary with the addition of the special absorption layer can keep the convergence of the calculation result when the distance from the scatterer is 5 mesh, while the traditional absorption boundary is required to be separated by 80 grids to ensure the results converge. By using this absorption boundary in the structure, the transmission characteristic curve of the multilayer photonic crystal was calculated and compared with the result obtained by the conventional method, the results were in good agreement with each other. The numerical results show that the method is effective and correct.
Combined the optical vortex with computer generated holography, an approach for producing optical vortex array with high quality was proposed. The formation and distribution characteristics of optical vortex array were theoretically discussed, and optical vortex array was produced by numerical simulation. The hologram of optical vortex array was generated by conjugate symmetric extension Fourier computer generated holography. Based on spatial light modulator loaded with holograms, the optical vortex arrays were reconstructed in the experiment. In order to evaluate the generated beams, Mach-Zehnder interference system was adopted. It is very simple and easy to produce the optical vortex array, which provides more complicated light distributions and controllable parameters. The research results may have a potential value in optical micromanipulation, optical communication and other fields.
In order to meet the demand for accurate and rapid multiple scattering simulation of fog, when the short-range radar distance was close, a fast and efficient simulation method of multi-scattering was proposed based on the combination of Mie theory and radar equation. First, the fog model was built according to the fog particle size distribution. Then, scattering functions about single particle were given based on Mie theory, and the first order scattering and the second order scattering power densities of single particle in fog model were calculated. The expressions of multiple scattering cross section of single particle and scattering coefficients of fog were deduced based on radar equation. Simulation results show that the second order scattering cross section is approximately proportional to 2/3 power density of fog, and the second order scattering coefficient with increasing visibility decreases more quickly than the first order scattering.
For the task of weak-feature target tracking in infrared image sequences, existing methods failed to track the target accurately for lack of information in the target's surface and the interferences from the strong noise in the scene. Focusing on this problem, a particle filter method is proposed by the Spatial-Temporal Orientation Energy (SOE). The method describes the target by using the SOE histogram. The similarity of the SOE histograms between the particles and the target is employed as the observation input to the particle filter. It is noted that the method is high robustness to target illuminated radiation as the SOE feature reflects target dynamics. Experimental results show that the proposed method has good stability to track targets in different scenes and is more effective and adaptive than the traditional grey-scale feature.