Si thin film as planarizing layer were deposited on Reaction Bonded-SiC (RB-SiC) substrate by using RF magnetron sputtering technique. A set of orthogonal experiments were designed and performed to determine an optimized process condition by characterizing the evolution of the quality and surface morphology of the Si films deposited at various sputtering power, working pressure and Argon flow rate. The planarization was obtained at sputtering power of 120W, working pressure of 1.2 Pa and Argon flow rate of 40 sccm. Then smoothing of inductively coupled plasma (ICP) etching was performed and the surface reflectivity of samples processed under different treatment stages was investigated by using Lambda 950 spectrophotometer. The results show that the surface roughness Sq of RB-SiC sample under planarization and ICP etching process is reduced from 1.819 nm to 0.919 nm compared with untreated RB-SiC sample, and the surface reflectivity of the sample increased by 2%. Therefore the combinatorial optical polishing technology based planarization with RF magnetron sputtering and ICP etching process can enhance the performance of RB-SiC surface finishing.
To achieve the photoelectric controllable characteristics of Frequency Selective Surface (FSS) resonant frequency, a photoelectric controllable FSS is put forward in this paper. The photoconductive thin film is used to control the change of the structure size of FSS, so as to realize the controllability of FSS. This thesis starts from the theory of the photoconductive thin film and the principle of the characteristics that FSS can select frequency. The CST software was used to simulate three kinds of FSS:"tripole" slot-element, "circular" slot-element, "tripole" patch-element, and get the selecting frequency characteristics of different structure sizes. The simulation result shows that, with the changing structure size, the center resonant frequency of the FSS changes from 18 GHz, 25 GHz, and 20.5 GHz to 20.5 GHz, 29 GHz, and 16.5 GHz respectively. Finally, the metallic FSS with the unchanged structure size, and the FSS of the metal and the photoconductive thin film combined, were fabricated by coating, etching, electron beam evaporation and so on. Test the samples and the result shows that the center resonant frequency changes from 18 GHz, 24 GHz, 20 GHz into 20 GHz, 28 GHz, 17 GHz. Compared with the simulation results, the trend is about the same. Ultimately, we can draw the conclusion:in this way, not only can we realize the characteristic of controlling the center resonant frequency, but also we can achieve the conversion of slot-element or patch-element in the structure of FSS.
The formation and stability of surface gap solitons at the interface between a metal and a self-defocusing periodic media are investigated. Such type of surface gap solitons exist only in finite gaps when the lattice depth exceeds a critical value. In the first and second gap, the existence domain of surface gap solitons includes both stable and unstable domains. The critical value of the lattice depth in the second gap is much larger than the critical value of the lattice depth in the first gap. In the first finite gap, if the lattice depth is fixed, the energy flow of surface gap solitons decreases with an increase of the propagation constant, surface gap solitons have short oscillating tails in the lattice region when the propagation constant is increased. For a given propagation constant, the energy flow of surface gap solitons increases with lattice depth increasing, and surface gap solitons can be switched from unstable state to stable state by changing the lattice depth. Unstable surface gap solitons tend to self-bend toward the positive direction of the transverse axis during propagation. The self-deflection angle decreases with an increase of the lattice depth. The trajectory of the main lobe of surface gap soliton is a zigzag curve. In the second gap, surface gap solitons have more tail oscillations, and the unstable domain is close to the upper bound of the existing domain. With the propagation constant increasing, the unstable domain decreases gradually.
A terahertz wave switch based on prism-air-graphene-quartz-Si structure was proposed. The dielectric constant of grapheme was changed by the applied external voltage, which make the terahertz wave reflectivity dramatically was changed. The plasma resonance mechanism was used to control of reflected terahertz wave intensity and realize the function of terahertz wave switch. Firstly, the influence of air gap distance on terahertz wave reflectivity is studied. The results show that when air gap is 20 μm, the minimum value of terahertz wave reflectance is 68.79%, When air gap is 56 μm, the minimum value of terahertz wave reflectance is reduced to 0.04% and the air gap distance reaches the optimum value. Secondly, the influence of graphene chemical potential on terahertz wave reflectivity was determined. The results show that when the chemical potential of graphene increases from 0 eV to 0.2 eV, the reflectivity of terahertz wave increases from zero to 95.89% and changes from zero to total reflection. The numerical results also further show that the proposed structure has enormous potential for terahertz wave switch with the extinction ratio of 33 dB.
Two-dimontional the finite-difference time-domain method was adopted to theoretically study the anomalous optical transmission properties of an asymmetric two integrated metallic nanoslits with an ultrathin separation thickness. The influence of the slit length, the slit number and the incident angle on the optical transmission of the proposed structure were also investigated. The results domenstrate that surface plsamon polaritons, propagating inside the two slits, produce a cross-talk coupling effect via penetrating into the metallic separation, and hybridize into symmetric and antisymmetric modes, resluting in two resonant peaks and a nearly-zero dip in the transmission spectrum; the essential physics of the plasmonic cross-talk coupling for the two integrated slits is the interference between the transverse electric fields of surface plsamon polaritons within the seperation material, and the original phase difference of transverse electric fields between the two integrated slits determines the type of the surface plasmon polariton hybird modes inside it. Since the transmission extremums are associated with the Fabry-Perot resonance inside each slit cavity of the two integrated nanoslits structure, the slit length determines the wavelengths of the tranmission peaks and dip, while the slit number and the incident angle of plane wave only influence the effciency of the tranmission peaks. The two integrated nanoslits structure posses the functions of optical filtering and spatial color dispersion, which have implications on the field of new functional nanooptic devices.
By utilizing the holographic technique, a novel type of twins composite discrete Airy-vortex accelerating beam is generated with discrete Airy-vortex phase which is processed by binary phase. The propagation properties of the accelerating beam and the modulation of different parameters[the linear factor(s)、the number of total layer (N) and the topological gradient (△L)] to the accelerating beam is also studied by theoretical simulation and experiment. The results show that such twins accelerating beam will split itself into several separated Airy-like beams due to the discrete and rotatory effect in propagation; and the separated Airy-like beams evolve into one-dimensional Airy-like beams by adjusting the propagation distance and △L. Furthermore, s and N can modulate the intensity distribution of twins accelerating beam and the space distribution of twins accelerating beam in initial plane (the plane x-y at z=0), respectively; △L also can modulate the intensity distribution of separated Airy-like beams.
In order to generate high-quality optical vortices, this paper presents theoretical analysis, improved design and experimental demonstration of a novel approach for optical vortex generation based on Sagnac interferometer. The additional phase difference π is introduced, based on analyzing the influence of the interference loop on the shear amount, a optical vortex generation setup on the basis of a Sagnac interferometer is built, then the related considerations are given and optical vortices of topological charge +1 and -1 are generated respectively. The intensity distribution and interference patterns at various propagation distance are experimentally recorded and analyzed with topological charge keeping +1 and -1. The improved setup can generate optical vortices with higher quality.
Using precisely atomic layer etching technology, surface etching process of Te-doped GaSb surface by nitrogen plasma in the plasma enhanced atomic layer deposition system, which can improve emission intensity. The emission intensity increased by a factor of 4 at room temperature.With low temperature photoluminescence measurement, the peak associated with TeSb donor defects due to Te doping was found, with a peak position of 0.743 eV. In addition, the changing of band edge emission with temperature from 0.796 eV to 0.723 eV was also observed. By comparing the room temperature spectra and low temperature spectra,when the nitrogen plasma etching power was 100 W, the best etching cycle of Te-GaSb was 200 cycles. Moreover, the nitrogen passivation does not changed the emission mechanism of Te-GaSb, but improves the radiative recombination efficiency of the sample.
The reduced graphene oxide/nano-copper composites were prepared by using in-situ reduction method and characterized. The complex refractive index of the composites in middle and far infrared band were measured, and its absorption coefficient and normal spectral emissivity in the atmospheric window were calculated and verified by experiment, along with the analysis of its absorption and radiance performance in middle and far infrared. The results show that nano-coppers are adsorbed on the surface of reduced graphene oxide, and its size almost concentrate in 15~25 nm. Due to the different sizes of nano-copper, and reduced graphene oxide together with its surface defects and functional groups, the composites have a strong absorption performance in 8~9.2 μm, 6~6.5 μm, 2~3 μm. Its normal spectral emissivity in 3~5 μm is within 0.65~0.68, but it has a minimum value of 0.53 in 8~9.5 μm, and then stabilize at about 0.58. Their total normal emissivity is 0.66 and 0.59 respectively, which are consistent with the experiment. The composites can be used for infrared absorption, extinction materials and stealthy coatings.
TiO2 nanowire arrays were generated on FTO glass by hydrothermal method, and then the TiO2/MoO3 composite film was prepared through electrodepositing MoO3 coating onto TiO2 nanowire arrays. The formation of TiO2/MoO3 composite films were confirmed by X-ray diffraction and scanning electron microscope. Li+ insertion/extraction in LiClO4/PC solution had been studied by electrochemical measurement technologies, and the optical transmittance of the samples in the colored and bleached states were used by UV-Vis NIR spectrophotometer. The parameters of switching time, reversibility, optical modulation and coloration efficiency were obtained. Then, the electrochromic properties were analyzed. The analysis showed that the electrochromic properties of the TiO2/MoO3 composite films were obviously enhanced for comparing with the TiO2 nanowire and MoO3 films. The effects of different thickness MoO3 coating on the discoloration properties of the composite films were studied. The results showed that TiO2/MoO3 composite films with 6 cycles of MoO3 thin films had the best electrochromic performance.
The phenomenon of mutli-soliton pulse is studied in Tm/Ho-codoped fiber laser based on a nonlinear amplified loop mirror as an artificial saturable absorber. By simply adjusting the polarization angle of Polarization Controller (PC), the experiment not only obtained a stable single-soliton pulse, but also observed the pulse sequences of the two-soliton, three-soliton and four-soliton. Increase the pump power under polarization maintaining operation, the evolution of soliton energy quantization is also obtained. The weak birefringence effect in the cavity is important for limiting the gain bandwidth and inducing the generation of multi-soliton. Adjusting the PC is equivalent to changing the gain in the cavity, which is the main reason for the formation of different multiple pulses states. We believe that the results obtained will be helpful in the investigation of multi-soliton pulses dynamics in 2 μm mode-locked fiber lasers.
The nonlinear dynamics of a weak-resonant-cavity Fabry-Perot laser diode subject to optical injection was experimentally investigated. By recording the time series, power spectra and optical spectra of three longitudinal modes ("mode -3", "mode 0", and "mode 13") in the weak-resonant-cavity Fabry-Perot laser diode, the nonlinear dynamical states have been determined. The results show that, after introducing optical injection, through varying injection strength and frequency detuning, the three longitudinal modes can exhibit four-wave mixing, period one, quasi-period, chaos, and stable injection-locking, and the dynamical evolution route is from quasi-period to chaos. Moreover, in order to control the dynamical state accurately, we draw the dynamical state mappings of the three longitudinal modes in the parameter space of injection strength from 0 μW to 450 μW and frequency detuning from -16 GHz to 16 GHz. The results demonstrate that the chaotic region can be observed in the positive and negative frequency detuning for "mode 0" and "mode 13", but cannot be observed in the negative frequency detuning region for "mode -3". And there exist two separate stable injection-locking regions for "mode 0", but there is only one stable injection-locking region for "mode -3" and "mode 13".
The non-absorbing window is adopted in the 915nm semiconductor laser to improve the catastrophic optical damage level of the device. The non-absorbing window is fabricated by impurity free vacancy diffusion induces quantum well intermixing based on SiO2 thin film technology. The theory of the impurity free vacancy diffusion induces quantum well intermixing will be systematic researching. And the different experimental conditions such as the annealing temperature, the thickness of SiO2 thin film, the refractive index of SiO2 film and the cover gaps are evaluated in the paper. And the mechanism is discussed for the effect of the porosity SiO2 film dielectric film in the impurity free vacancy diffusion induces quantum well intermixing. Ultimately the experiment results show that a luminescence blue shift 53 nm is obtained from the sample The optimal experimental conditions are annealing at 875℃ for 90s, and the thickness of the SiO2 thin film is 200 nm with the refractive index is 1.447, choosing GaAs cap piece to be the cover gap.
The blind pixels existing in planner PIN type In0.52Al0.48As/In0.53Ga0.47As/In0.52Al0.48 As short wavelength infrared detector were analyzed with the aid of scanning capacitance microscopy technique. And the simulation of blind pixels by Sentaurus TCAD was also presented. In order to eliminate the blind pixels, the transfer line model chip was fabricated to optimize the ohmic contact of Au electrode on P-In0.52Al0.48As. The result shows that a conductive chanel formed between the P electrode and the N--In0.52Al0.48 As cap layer outside the diffusion region resultes in blind pixel generation. Fourthermore, the special contact resistivity which is 3.52×10-4 Ω·cm-2 of Au on P-In0.52Al0.48As was obatined and the problem of Au flowing occurred in rapid thermal processing was suppressed after optimization, so that the probability of blind pixels generation was reduced.
In0.53Ga0.47As/InP Avalanche Photodiode (APD) with low dark current, wide-range response is prepared by molecular beam epitaxy and open-tube zinc diffusion method. The dark current is less than 10 nA at 0.95Vb (Vb is the avalanche breakdown voltage), and the capacitance density is as low as 1.43×10-8 F/cm2 when the bias voltage is -5 V. The response range of APD is 50 nW~20 mW and the responsibility is up to 1.13 A/W under 1 310 nm infrared laser at 30 V reverse bias voltage. The breakdown voltage and punch-through voltage are investigated by changing concentration of the charge layer and thickness of the multiplication layer. The result shows that the punch-through voltage increases linearly, conversely, the breakdown voltage decreases linearly with increasing concentration of the charge layer. Further, the punch-through voltage increases linearly and breakdown voltage also increases with increasing thickness of the multiplication layer, while the surface density of charge layer is 4.8×1012 cm-2. Through optimizing SAGCM-APD device structure, the APD device achieves a 25 V punch-through voltage and a 57 V breakdown voltage, with low dark current, and wide-range response characteristics.
Atmospheric aerosol extinction coefficient vertical profiles of near-surface in Hefei western suburb were measured by a CCD lidar system in the day and night, which could fill the gap of the traditional Mie-scattering lidar system especially in the blind area and overlapped region. By comparison of the aerosol extinction coefficient retrieved by Mie-scattering aerosol lidar and CCD lidar at night, the reliability of the CCD lidar system was verified, and the daytime detection of the CCD lidar system was feasible. Profiles of atmospheric aerosol extinction coefficient for 10-180 m altitude were obtained with high spatial resolution, of which the highest resolution was up to 1 cm. Two cases of aerosol extinction coefficient profiles showed that the aerosol extinction coefficient was not monotone decreasing in vertical direction, at the same time, changed violently in the day. The spatio-temporal evolution of aerosol extinction coefficient retrieved by CCD lidar showed that the overall aerosol had a tendency to reduce as the day getting dark. The daytime detection of aerosol extinction coefficient profile by using CCD lidar is credible and fulfilled.
Three-channel processing structure was proposed to extend the input dynamic range. Each channel is set up with low, middle or high gain according to the echo intensity from different water depth. Afterwards, a data stitching method and a new fitting approach with the combination of pentagonal and Gaussian function are applied to each three-channel waveform to estimate the depth of water. The multi-channel processing structure was verified on the simulated data sets obtained from the existing Wa-LID waveform simulator. The simulated result has shown that the effective input signal is up to 86.9 dB dynamic range in this new processing technique, and the measured depth reaches 26 m. The bias of the bathymetry estimates is ranging from 1.6 to 4.7 cm with the standard deviation better than 1.1 cm. This multi-channel processing technology can be effectively used in ALB.
A optical image mosaic methods based on a micro-electro-mechanical system gyroscope sensor mounted with camera rigidly was presented. The relation between the camera rotation angles and the movements of point's image coordinates is derived based on camera projection model and coordinates transformation. The rotation angle is calculated by the data from gyroscope, thus the search window size could be obtained; then by using the SURF feature extraction algorithm to extract the feature points, the feature matching is conducted in the search window which avoids global searching and accelerates the matching speed by reducing computation. The experiment platform was built to verify the algorithm. The result shows that 31% running time was reduced compared to the traditional global matching.
In order to analyze hyperspectral images consisted of highly mixed pixels, a new endmembers overall coverage constraint was proposed and introduced in objective function of nonnegative matrix factorization, which forcely maximizes the number of pixels contained in the simplex constructed by endmembers using data geometrical properties in the feature space while satisfies data nonnegative and abundance sum-to-one constraint simultaneously. In the maximum overall coverage constraint nonnegative matrix factorization algorithm, the dimensionality reduction process is prevented to preserve the physical meaning of the source image and multiplicative update rules are applied to avoid stepsize selection problem occurred in traditional gradient-based optimization algorithm frequently. To evaluate the accuracy of endmembers extraction, the performance and robustness, experiments are designed on synthetic and real images. The results demonstrate that the proposed algorithm is an effective method to analyze mixed data in hyperspectral image.
In order to accurately measure the surface deformation information, a surface deformation measurement method based on Empirical Wavelet Transform (EWT) and kernel probability density was proposed. Firstly, the CCD camera was used to collect the digital speckle pattern interferometry (DSPI) maps, the DSPI maps were decomposed to obtain a series of intrinsic components by EWT. According to the kernel probability density of the decomposed component, an adaptive de-noising method was proposed to extract the components with the deformation information, the components were reconstructed DSPI maps; Finally, using Hilbert method to calculate reconstructed DSPI phase, the DSPI phase before and after deformation was subtracted, and the surface deformation information was obtained by decoupling according to the phase difference. The experimental results showed that the method can effectively measure the object surface deformation, and the accuracy is improved by 4 times compared with the EMD method.
A compact spatial heterodyne imaging spectrometer suitable for micro satellite platforms is designed. Two sets of interference structures are used to make the fringes localized outside the system. The imaging plane of front lens system and fringe localization of system are overlapped so that the spatial location information and the spectral information of target are obtained. According to the expression of axis optical field and Nyquist sampling theorem, the relationship between spectral resolution and spectral range and some critical parameters is given. Through the way of ray tracing, the theoretical proof of fringe localization is described in detail, and the universal function expression of instrument is derived. This compact spatial heterodyne imaging spectrometer for observation of O[1D]630nm airglow from satellite is designed and simulated. The spectral sampling interval of the system is 0.762 3 cm-1 and the spectral range is 601.674 9~631.324 6 nm. Finally, a compact spatial heterodyne imaging spectrometer is built to verify the results. And the target image and recovery spectrum of the 632.8nm laser source is obtained. The simulation and experimental results show that spectral sampling interval of the system achieve the design requirements, and the spectral is 20 822 at 630nm. The alignment error (±1°) of quarter-wave plate and polarizer has little influence on the modulation of fringes. It shows that the system has the imaging capabilities and spectral detectability, and can be used as a spatiotemporal mixed modulated spectrometer.
A humidity measurement method based on a fiber loop cavity ring-down spectroscopy system with low gain and low noise erbium-doped fiber amplifier is proposed and experimentally demonstrated. The influence of an erbium-doped fiber amplifier placed inside and outside the fiber ring on the pulse curve and the number of pulse peaks in the annular cavity is analyzed. A length of 2 m low-gain and low-noise erbium-doped fiber in an erbium-doped fiber amplifier is used to reduce waveform distortion and compensate for the noise attenuation of the cavity. Measurement of relation humidity is performed with the fiber loop cavity ring-down spectroscopy system, and the change of relation humidity is gained by recording the ring-down time τ of light pulse in the fiber loop. Results indicate that a good linear relationship is met between relation humidity and τ in the range of 30% to 100%. The sensitivity and accuracy of the fiber loop cavity ring-down spectroscopy system are 3.826 79 μs/RH and 0.994 77 respectively. So it can be employed for the fields of industrial detection, environmental inspection and medical diagnosis.
A highly sensitive microfiber ammonia (NH3) sensor was fabricated by means of flame melting taper in this paper. The sensor is fabricated by splicing a length of 10 mm Polarization Maintaining Fiber (PMF) in the middle of ordinary Single Mode Fibers (SMF), stretching the PMF down to microscale with diameter of 8.33 μm by using optical fiber melt tapering machine. Based on the principle of Mach-Zehnder Interferometer (MZI), this structure utilizes the interaction of PMF core and cladding modes to achieve inter-mode interference. When the NH3 concentration changes in the external environment, the evanescent field in the cone area changes. By detecting the wavelength shift of the transmission spectrum, the concentration of ammonia can be measured by fabricated sensors in this paper. The experimental result shows that the sensor has a quadratic corelation to ammonia concentration in the range of 8 ppm-56 ppm, and the wavelength shift about 5nm in the direction of the long wave. The experimental result also shows that the sensor has a linear corelation to ammonia concentration with sensitivity of 176.08 pm/ppm in the range of 32 ppm-56 ppm. The sensor has the advantages of small size, easy fabrication and high sensitivity making it a good candidate for NH3 sensor in different fields.
An optical fiber gas sensing method was proposed based on the detection of light sensitive phase of light wave combined with organic polymers and the experimental verification was given. When using different concentrations of acid gases to act on the organic polymers, the refractive index of the organic polymer will change. By filling organic polymer film in optical fiber F-P cavity and analyzing the spectral characteristics of fiber F-P cavity output, it can be realized the hydrogen sulfide gas sensing. Experimental results show that accompanied by the increasing of concentration of the gas under the test, the refractive index of organic polymer decreasing. At low concentration, a record (0.726~1.006)×10-2 cm/%VOL of system resolution is obtained, Phase sensitivity is found to be 1.276×10-2 rad/%VOL and concentration resolution is found to be 0.078ppm. Through this test, it is proved that the possibility of gas sensing by using organic polymer. This system can be applied to high-precision measurement of carbon dioxide, hydrogen sulfide and other gases in the petrochemical field.
A compound structure is fabricated by inscribing fiber Bragg gratings in dispersion compensation fiber, which is constituted by interferometer and fiber Bragg grating in a length of fiber. The strain and temperature response mechanisms of cladding mode and Bragg resonance are analyzed. The matrix equation is established through monitoring the cladding modes and Bragg resonance wavelength shift on the reflection spectrum, so that the simultaneous measurement of strain and temperature is achieved. The experimental results indicated that the temperature sensitivity of cladding mode and Bragg resonance are 49.4 pm/℃ and 11.0 pm/℃, respectively. The strain sensitivity of cladding modes is 1.05 pm/με and the strain sensitivity of Bragg resonance is 0.651 pm/με. The four parameters show good linearity. Since the compound structure has low-order cladding modes and core modes, it is insensitive to the environment and can play an important role in the field of strain and temperature simultaneous measurement.
The coupled amplitude equations of stimulated Brillouin scattering in optical fibers are numerically solved with fourth-order Runge-Kutta formula and characteristics methods, the influences of gain, energy, and Full Width at Half Maximum (FWHM) of injected triangular wave Stocks pulses on time delay and pulse broadening are investigated. The results show that the time delay and pulse broadening depend on the gain, energy and FWHM of the triangular pulses. The maximum time delay increases with the injected pulses energy decreasing. Smaller FWHM of pulse induces larger relative time delay. The maximum time delay and less pulse broadening can be obtained by optimizing the gain, energy, and FWHM of injected triangular wave Stocks pulses. These results provide reference for designing novel optical communication or sensing components.
A fiber optic magnetic sensor for the measurement of weak static magnetic field, based on Terfenol-D materials and Fiber Bragg Grating Fabry-Perot (FBG-FP) cavity, is proposed and demonstrated. In order to improve the sensitivity of the sensor, a NdFeB magnet is used to apply bias magnetic field. To compensate the environmental temperature, another FBG-FP coupled with Monel-400 is used as a reference. The measurement sensitivity of the sensor is 1.7×10-3 pm/μT, which results in a magnetic induction resolution of 3.0 μT. The experimental results show that the sensor exhibits excellent linearity and directivity in response to static magnetic field.
In order to further enhance the transmission distance and secret key rate of the Measurement-Device-Independent Quantum Key Distribution (MDI-QKD) system, the Pulse Position Modulation (PPM) technique is introduced to the MDI-QKD protocol, and a new efficient quantum key distribution protocol, named PPM-MDI-QKD protocol, is proposed by utilizing the empty pulses of the weak source and high dimensional encoding technology. In the protocol, two communication parties firstly construct a PPM frame consisting of M consecutive weak pulses, then combine the BB84 polarization encoding and PPM encoding schemes to operate high dimensional encoding, and finally sift out the secure key with the legal PPM frame, the successful Bell-state measurement results, and matched bases. The numerical results show that the PPM-MDI-QKD protocol outperforms MDI-QKD protocol when the intensity of signals is less than 0.13. Moreover, compared with 404 km, the longest distance reported so far, the transmission distance can theoretically be extended to 480 km and the key rate up to 5.4×10-4 bps in 404 km, with the same parameters.
This paper proposed a reconstruction method for the synthetic aperture in-line digital hologram with seams. The calculated means is prefilled at the seams. By using Gerchberg-Saxton (GS) weighted phase retrieval algorithm based on the angular spectrum, the phase is retrieved and the complete complex amplitude on recording surface is obtained. The particle field detection is simulated with this method. The result indicates that the correlation coefficient between the reconstructed image and the simulated particles target image doubled in contrast to the traditional method. Therefore, the influence of information loss at the seams is effectively restrained and high-quality reconstructed image can be achieved.
The properties of the martian dust aerosols was studied, and the log-normal distribution of particle sizes was used to fit the particle size distribution of the martian dust aerosols.The transmission characteristics of laser with different wavelength were studied by using Mie theory and Monte Carlo method. Under the condition of dust, the variety of the visibility, transmissivity and attenuation with particle mass concentration was analyzed.The curve of visibility along with particle mass concentration at wavelength of 0.55 μm was given, and the calculation results of Mie theory and Monte Carlo method were compared. The results show that the visibility drops rapidly and then decreases slowly and tend to be about 2km with the increase of particle mass concentration.The higher the particle concentration is, the more obvious the phenomenon of multiple scattering is,and the visibility calculated by Monte Carlo method is higher than Mie theory. In the several selected wavelengths, the laser transmission attenuation at wavelengths of 7.46 μm is minimal under the condition of dust,so it is the most suitable for wireless laser communication on Mars.