In order to inhibit the effects of atmospheric turbulence by using the non-diffracting, self recovery and self bending property of Airy beam and realize the remote wireless optical communication, the intensity evolution of partially coherent Airy beams propagating in turbulent atmosphere were studied. By using the cross spectral density function of Gauss-Schell model, the generalized Huygens-Finel principle and the methods of Rytov phase approximation, the expressions for the average intensity of partially coherent Airy in turbulent atmosphere were derived. Then, the influences of propagation distance, turbulence intensity and other parameters on the intensity distribution were simulated, and the influence of the beam parameters on the intensity distribution was verified by experiments. The results show that the side lobe of the partially coherent Airy beam is gradually attenuated and the main lobe is gradually spread, with the increase of the propagation distance. When the spread is long enough, the side lobe is gradually lost, and the main lobe is gradually evolved into Gauss distribution. The simulation and experimental results show that the smaller the truncation factor is, the longer the characteristic length and the coherence length is, so that the beam intensity distribution is maintained integrally.
In order to analyze the influence of different mixing patterns of mixed particles on the quantum satellite communication, according to the spectral distribution function of hazeparticles and water-cloud particles and the extinction factor in different mixing patterns, the attenuation relationship of the quantum satellite communication channel in external mixing mode was proposed, and the Core-shell channel attenuation model was established. Thus the quantitative relation among the volume ratio of the mixed particles, fidelity of quantum communication and channel bit error rate were analyzed and simulated. The simulation results show that, when the volume ratio of mixing particles is 0.2 (0.8), the channel capacity, channel average fidelity and the channel bit error rate of external mixing mode will be 0.39 (0.27), 0.8 (0.8) and 0.003 (0.009), respectively; the channel capacity, channel average fidelity and the channel bit error rate of external mixing mode will be 0.8 (0.21), 0.94 (0.81) and 0.018 (0.021), respectively. It can be seen that the influence of different mixing modes of haze aerosol and water cloud particles on the communication performance of quantum satellite is different. Therefore, the parameters of the communication system should be adjusted adaptively based on the different mixing patterns to improve the reliability of the quantum satellite communication.
A method of measuring atmospheric transmittance from a single frame of multi-spectral image for non and weak absorption waveband was proposed, which can be applied to evaluate and correct atmospheric attenuation effect in optoelectronics engineering field. Firstly, a radiometric image can be acquired using the camera with absolute radiometric calibration; secondly, according to the optical model of image degradation in atmosphere and the dark channel prior statistical theory, average atmospheric transmittance of dark channel can be calculated from radiometric image; finally, the atmospheric transmittance of specific wavelength is calculated using the average extinction coefficient relation database of the specific wavelength and the dark channel waveband. The experimental comparison indicates that the correlations between the transmittances measured by the new method, visibility meter and lidar are good. For the new method and visibility meter, the correlation coefficients are between 0.89 and 0.95, and the average relative deviations are no more than 9%, 15%, 30% for 1km, 4 km and 6 km, respectively; while for the new method and lidar, the correlation coefficients are between 0.95 and 0.97, and the average relative deviations are no more than 6%, 9%, 18% for 1 km, 4 km and 6 km, respectively.
A mobile lidar system was developed which can be used to measure the lower layer atmospheric SO2. The lasers with wavelength of 300.05 nm and 301.50 nm are adopted in this system. The laser beams, produced by two narrow linewidth dye lasers pumped by two Nd:YAG lasers, are frequency doubled by second harmonic generation crystals. They are merged, expanded and transmitted into the atmosphere coaxially with telescope. The back scattering signals are received by the Newton telescope and converted into electrical signals by photomultiplier. The data are obtained by A/D acquisition card and used to estimate the profile of sulfur dioxide. The horizontal detection were field experimented in Huainan, the results show that the mean concentration of atmospheric SO2 is about 20 μg·m-3 in the range from 0.8 km to 3.0 km. It conforms with the results of ground instrument from meteorological department whose results is about 18-22 μg·m-3.
In order to analyze the influence of atmospheric turbulence on the performance of free space Quantum Key Distribution (QKD), the turbulence is modeled as randomly distributed atmospheric bubbles so as to conceive the propagation process of single photon using geometric optics. The fluctuation of photon transmission ratio k and Quantum Bit Error Rate (QBER) Ep has been quantitatively calculated, which both are caused by the change of polarization state after continuous refractions. Then the trends of these two values are simulated with random turbulence refractive index using Monte-Carlo method. Furthermore, the key generation rate of decoy state free space QKD has been derived under turbulence situation. The upper bound of k is achieved through analyzing the source of QBER and the relationship between Ep and incident angle and turbulence refractive index is established which defines the secure threshold of Ep. Simulation results show that when incident angle is between 44.8±and 76.5±while the refractive index falls within 1~1.33 will meet the required upper bound of Ep, which provides theoretical reference to quantum communication in turbulence scenario.
Adopting modified Sagnac interference grating writing system, the fiber Bragg gratings were written in two kinds of As2S3 chalcogenide fibers with different cladding diameter by use of a near bandgap light at 532 nm and +1/-1 diffracted orders phase mask, and the gratings dynamic characteristics during the exposure were studied. It is found that the depth of grating transmission peak in low-loss As2S3 chalcogenide fiber increases with a decrease of the cladding diameter. During exposure, the Bragg wavelength shifts fast towards short wavelength at first, and then with increasing exposure time restores slowly towards long wavelength. At exposure time from 800 s to 1000 s, the good quality Bragg grating with about -2.6 dB bandgap and about 0.37 nm bandwidth in transmission spectra was fabricated in As2S3 chalcogenide fiber with about 140 μm cladding diameter. In addition, an analysis of photosensitivity in the As2S3 chalcogenide fiber core shows that the refractive index modulation amplitude and the change of average refractive index with the exposure time can achieve to be on the order of 10-4 and 10-3, respectively.
A scheme of coaxial reflective laser communication antenna added an axicon pair was proposed. This antenna could rearrange the light intensity distribution of the incident beam, leading to a great reduction of the energy loss caused by the central obscuration of the coaxial reflective structure and an increasing of the light-energy-utilization-ratio. Using the diffraction optical principle, the optical field distribution of the monochromatic Gaussian beam propagating to the antenna optical stop plane passed the axicon pair was analyzed and simulated, and the transmitting light energy utilization ratios of the ordinary coaxial reflective antenna and the high light-energy-utilization-ratio antenna in different incident beam waist and line obscuration ratios were compared. It was found that at the line obscuration ratio of 0.1 and 0.25, the light-energy-utilization-ratios of the high light-energy-utilization-ratio antenna were more than 99% and 96% through adjusting the incident beam waist diameter reasonably, which were much highest than that of the traditional coaxial reflective antenna. The far-field optical intensity of the light-energy-utilization-ratio antenna transmitting beam was analyzed, and the the light intensity in the receiving antenna aperture can be considered as a flat top distribution.
Optical microsphere (OM) cavities supporting Whispering Gallery Modes (WGMs) have received much attention because of their high quality factor (Q). The study analyzes the Fabry-Perot (FP) cavity and OM cavity theories. An OM cavity with diameter of 1.2 mm was produced by melting a silica optical fiber using a CO2 laser, and the coupling structure for OM cavity and tapered fiber was tested. We designed an OM cavity frequency stabilization system based on basic PDH frequency stabilization system. Absorption and dispersion characteristics of error signal curves used to be frequency discrimination curves were analyzed. We compared the relationships between error signal slopes and different modulation frequency, OM cavity's diameter, coupling loss, transmission loss. The results show that the maximum Q factor of OM cavity coupled by the tapered fiber is 1.1×108. Transverse electric (TE) mode and transverse magnetic (TM) mode can be transformed to optimize coupling efficiency. The transmission spectrum of the second radial mode was obtained by matching dimensions between OM cavity and tapered fiber. The slope of the error signal is 15.4 A mW/MHz. Our work shows its potential to improve the sensitivity of the PDH technique.
The dual Mach-Zehnder interferometer-type distributed optical fiber sensing system is susceptible to environmental noise and system noise due to its high sensitivity, which makes a large error in calculating the position of the disturbance signal by direct cross correlation algorithm. The quadratic cross correlation algorithm was used to process the two received signals, and then process the autocorrelation of one signal. The disturbance signal was located by estimating the delay of the two signals. With the improved method, it can reduce the error caused by noise and improve the calculation accuracy. The theoretical simulation and analysis of the algorithm were carried out, and the experimental device was experimentally verified. The experimental results show that compared with the results of using the direct correlation algorithm, the proposed algorithm can effectively improve the positioning accuracy of the disturbance signal and has higher real-time performance.
In order to compensate the transmission limits of the high-speed signal caused by dispersion of the fiber, an all-solid dual-concentric-core photonic crystal fiber for dispersion compensation was proposed. Firstly, the mode coupling characteristics of the fiber was theoretically analyzed, and then multipole method was used to calculate the relationship between the parameters of the fiber and the dispersion value as well as the shift of phase matching wavelength, and the regularity was studied. Finally a dispersion compensating fiber with dispersion value of -32 620 ps/(nm·km) at 1 550 nm was achieved by optimizing the structural parameters of fiber, and numerical results also show that the loss is 0.29 dB/km and the splicing loss with SMF-28 fiber is 4.77 dB at 1 550 nm. The fiber can compensate 1 910 times the length of the SMF-28 single-mode fiber dispersion, its compensation ability is much larger than the conventional dispersion compensation fiber. The all-solid dispersion compensating photonic crystal fiber has the advantages of easy to fabricate and easy to splice with the traditional communication fiber compared with air-silica photonic crystal fiber.
A kind of cladding-carved Distributed Bragg Reflection (DBR) fiber laser was proposed for fiber laser refractive index detection. The core sensing unit is a single longitudinal mode dual polarization DBR fiber laser, the beat signal generated by the structure birefringence is used as the sensor signal to detect the refractive index. Frequency coding using in the experiment has the advantages of high sensitivity and is easy to demodulate. Using the thermal effect of the CO2 laser can carve the cavity of DBR fiber laser. The effects of different structural parameters on the sensitivity characteristics were studied by controlling the scanning range and the power of the CO2 laser. The effects of different structural parameters on the sensitivity characteristics were studied. The measured optimum sensitivity is -240 MHz/RI-unit. In addition, the temperature sensing characteristics of the structure were tested, and the sensitivity was increased by 21% to 1.73 MHz/℃, compared to the non-carved structure. The device has the advantages of compact structure, high stability, simple preparation and low cost, and can be used to further study of the sensing and multiplex characteristics of DBR fiber lasers.
By a full-vector finite-element method, the dual-core photonic crystal fiber for hydrostatic pressure sensing with two layers of air holes in the cross-section missed was designed and optimized, The mode field radius and numerical aperture of the optimized dual-core photonic crystal fiber are almost the same as that of the single mode fiber, which contributes to a relatively low splicing loss between the optimized dual-core photonic crystal fiber and the single mode fiber. The calculations results show that the total loss induced by the similar mode field radius and numerical aperture is as low as about 0.026 dB, less than that between the traditional photonic crystal fiber and single mode fiber of 0.1 dB. The performance of the hydrostatic pressure sensor based on the optimized dual-core photonic crystal fiber with a length of 20 cm was studied, and the results show the sensitivity is about -1.6 pm/MPa in the range from 0 to 500 MPa.
In consideration of low nonlinearity and maintaining of loss and dispersion when few-mode fiber is operated in single mode, the coexistence scheme of quantum-classical signals based on few-mode fiber operated in single mode was put forward. The coexistence model of quantum-classical signals based on few-mode fiber operated in single mode was built by Optisystem. The transmission performance of the model was analysed and compared with the existing model based on single-mode fiber. The result shows that the nonlinearity and signal crosstalk in existing model have been reduced efficiently in the proposed model. The bit error rate is two orders of magnitude lower than existing model and the transmission quality is improved obviously. It is suitable to apply the proposed model to massive network realization of quantum private communication.
An ultra-short polarization splitter based on dual-core Photonic Crystal Fiber (PCF) with a gold wire filled into the air hole between the two cores has been proposed and analyzed with the finite element method. Surface Plasmon Polaritons (SPPs) excited on the surface of gold wire have strong resonant coupling with the guided core modes of PCF, which enables a short polarization-splitting length and broadband operation. Compared to its counterparts, the proposed polarization splitter exhibits a shorter length and higher Extinction Ratio (ER), simultaneously. Numerical results indicate that the 0.263 mm long polarization splitter can achieve an ER of -70 dB at the wavelength of 1.55 μm with -20 dB-ER bandwidth of 124 nm.
A gain-flattened Raman fiber amplifier was proposed by using the method of cascading photonic crystal fiber, which improves the Raman gain coefficient and reduces the gain flatness of the traditional Raman fiber amplifier. Based on steady-state analysis theory of the stimulated Raman scattering effect, the photonic crystal fiber Raman gain spectrum and established the theoretical model of this Raman amplifier were analyzed. Through solving the coupled equation, the constraint condition for realizing gain-flattened is deduced, showing that the fiber length and pump power are two parameters affecting gain flatness of Raman fiber amplifier. Numerical simulation results show that a photonic crystal Raman fiber amplifier with 21 dB high gain and only 0.14 dB gain flatness over the bandwidth range of 1 508 nm to 1 544 nm, can be obtained. It will play an important role in the design of high efficient optical fiber communication systems.
In order to further investigate the lateral leakage loss behavior of shallowly-etched rib waveguides on silicon-on-insulator, a kind of shallowly-etched rib waveguide with non-rectangular crosssection was proposed and analyzed. A periodical loss model and a formula of loss period of this waveguide were obtained by the interference theory, and then phenomena of periodic variation of lateral leakage loss and shift of the maximum loss point for TM0-like mode were observed through the finite element method simulation in frequency domain with perfectly-matched layerconditions. The period in simulation results are highly consistent with theoretical calculation, and the average relative error is only 0.56%.In addition, it is found that TM0 mode loss can be adjusted from maximum to minimum by changing the cross section of rib waveguides with some trench widths, while TM0 mode loss is not sensitive to the change of cross section in rib waveguide with other trench widths. These findings can simplify process and improve fabrication tolerance, which provide theoretical guidance for the design and fabrication of this kind of waveguide.
In order to realize the detection and recognition of underwater acoustic signals, the characteristic expression of coherent detection signal under spectral aliasing was given theoretically, and a kind of signal demodulation method based on Hilbert transform was proposed by studying the characteristics of underwater multi-source coherence detection signals. Acoustic frequency demodulation of underwater multi-sources was realized in case of spectral aliasing. In this method, the Hilbert transform is carried out after filtering and smoothing processes to obtain the analytic form of the signal. Then, the second filtering and smoothing processes are carried out for the squares of the analytic signal modulo to separate the aliasing bands. After that, the spectrum of the obtained signal is analyzed. Frequency of each underwater acoustic signal can be calculated according to the frequency shift value finally. A laser coherence detection system was built in the optical darkroom, and the underwater acoustic signals of 2~6 kHz were experimented. The results show that the proposed method can effectively separate the signal bands that are mixed together in the detection signal, the accurately extract the frequency of each underwater acoustic signal, and the frequency extraction repeatability is not more than 2.5 Hz.
A self-calibration three-dimensional object surface measurement method with three image frames based on Gram-Schmidt orthonormalization method was proposed. The phase shift fringe map was obtained by translation grating, and the fringe background was eliminated by subtracting phase shift fringe maps with different frames. Then a phase demodulation method using Gram-Schmidt orthonormalization method and the least-square method was developed, so that the measurement phase can be extracted. Taking five steps Harlharan algorithm as a reference, the object surface was measured by different algorithms. The results show that compared with three steps phase shift algorithm and principal component analysis algorithm, the proposed method is more precise with phase error less than 0.5 rad and simplifies the mensuration.
In order to detect and recognize rotors based on laser micro-doppler effect, the modulation of laser echo by rotating area rotor is studied. Micro-doppler echo model of rectangular area rotor is built using the physical optics method of scattering echo superposition. Simulation of laser echo based on this model is completed and the micro-doppler feature different from line target rotor is extracted using time-frequency analysis method. Mechanism analysis confirms that the feature contains lateral size information of rotor. This paper proposes a method to calculate the chord of rectangular rotor through laser echo and verifies this method to be effective through rotor echo simulation of various aspect ratio. Error analysis shows that using the method of changing the window size of short-time Fourier transform (STFT) to extract time and frequency information respectively can reduce the chord length calculation error to 1.58% compared to single size. This model can realize the calculation of aircraft rotor chord size, providing an important reference for the research of rotor identification.
The Casimir interaction of a sandwich structure was investigated, where the structure was formed by means of inserting a dispersive metamaterial slab between the metal slab and the dielectric substrate. Based on Casimir-Liftshitz theory, the radiation pressure of the vacuum fluctuation was calculated by the Maxwell tensor method, and the situation for the sandwich structure was numerically calculated and analyzed by the method of transfer matrix of the electromagnetic mode. The calculation results show that the Casimir force for two-slab structure may turn into repulsion for the sandwich structure by means of inserting a metamaterial slab to the previous bi-layer structure, therefore the thin metal slab can be levitated by the repulsive Casimir force. The influences of the metamaterial dispersive electromagnetic response properties and the dielectric substrate were discussed. It is seen that when the larger magnetic plasma frequency of the metamaterial, the smaller magnetic resonance frequency and the smaller dielectric constant of the dielectric substrate are taken, the greater repulsion force can be obtained in the sandwich structure. In addition, it is found that when the slab distance is increased to a certain extent, the restoring Casimir force can be obtained in the sandwich structure. For the formation of restoring force, it shows that when the smaller filling factor of the metamaterial, the larger layer separation and larger layer thickness are adopted, the restoring force in the sandwich structure will appear at farther slab separation position. The quantum levitation and the restoring force may guarantee the stability of the micro-and nano-electromechanical system devices, and show the new application prospect based on the radiation pressure of vacuum fluctuation.
The monolayer grapheme film was employed in the metal structures when researching the spontaneous emission of atoms. The spontaneous emission of atoms was controlled by the special photoelectric properties of graphene. The local density of electromagnetic states was numerically calculated with the electric dyadic Green's function through the finite-difference frequency-domain method. The results show that with the increase of chemical potential, spontaneous emission peak appears blue shift phenomenon and the spontaneous emission are enhanced. The tunability of the peak position and amplitude of the spontaneous emission of the atoms is theoretically achieved. The theoretical results can be used as references for the fabrication and optimization of novel nano-devices and optoelectronic devices.
For the noise amplification problem during gradient transform based image enhancement, an improved algorithm combined with Gaussian curvature filter was proposed. First, the nonlinear gradient transformation is utilized for image gradient field to enhance the contrast. Then the enhanced image is reconstructed by minimizing an energy functional through gradient descent method. During iteration of gradient descent, the reconstructed image and its first and second derivatives are smoothed by Gaussian curvature filter, which can solve the promblems of nonlinear amplification and diffusion of noise in image reconstruction and preserve details. The experimental results with various images show the proposed algorithm can effectively suppress noises and enhance the image edges contrast at the same time.
In order to filter out the noise points of the spine 3D model effectively,a denoising and spreading method for spine 3D model based on bilateral filter operator was proposed.The bilateral filter operator is used to extract the contours of the 3D model, design and improve the adaptive diffusion coefficient, in order to better optimize the control of the entire diffusion process. The discrete iterative equation is established and the iterative stop criterion is designed so that the iteration is stopped when the de-noising effect is optimal. Compared with classical methods such as approximate diffusion model method, the proposed method achieves good filtering effect in solving the denoising method, which is much better than the traditional filtering algorithm.
According to the low accuracy and low stability of the single feature-based method for tungsten ore primary selection, a multi-feature fusion based on fuzzy support vector machine and D-S evidence theory was proposed. Firstly, the three types of vision feature that is color, gray and texture were extracted from the ore image after a series of image processing. Their probability function were acquired according to each type of feature utilizing fuzzy support vector machine and the results were used to D-S evidence theory as evidence. Finally, using D-S combination rule of evidence to achieve the decision fusion and giving final recognition result by classification rules. The experimental results show that the accuracy of multi-feature fusion methods is over 96% and it has good performance on accuracy and stability compared to the single feature-based method in tungsten ore primary selection. The accuracy and stability can meet the requirement of production process.
A set of 6×, 10×, 16×, 25×and 40×magnifications of digital slit-lamp microscope optical system is designed with Zemax. The optical system structure of traditional stereo slit-lamp microscope is analyzed, on its basis, the digital slit-lamp is divided into shared front-objective, Galileo telescope and photographic lens, using parallel Galileo telescope system structure to change rate. The optical properties and the technical indicators of shared front-objective, Galileo telescope and photographic lens are discussed, and the appropriate type of the lens is selected. Under the good imaging quality foundation in coaxial situation, the optical system is carried out the transition to non-coaxial and optimized. The modulation transfer function curve values are mainly greater than 0.2 at the position of 115 lp/mm in 6×, 10×, 16×, 25×except the low diffraction limit at 40×, and the spot diagram shows that the spot size in different magnifications are substantially less than the Airy disk. The lens has a good imaging effect with simple structure, easy processing and low cost.
In order to satisfy the high precision calibration of the detection ability of star sensor in different spectrum distribution, a design method of star simulator light source system with spectrum adjustable based on digital micro-mirror device was presented, which could solve the issue of star sensor optical signal calibration precision caused by the mismatch between star simulator's color temperature and star sensor's detecting color temperature. Firstly, according to the design technical specification, the Czerny-Turner optical system was selected as the light source optical system, two main aberrations of Czerny-Turner system, coma and astigmatism, were analyzed, and a coma-corrected Czerny-Turner structure was adopted. Secondly, the initial structure parameters of Czerny-Turner optical system was calculated by MATLAB and then optimized by ZEMAX. Finally, the tolerance analysis of the optical system was carried out. The result shows that the spectral resolution is less than 2 nm within the working spectrum range from 400 nm to 1 100 nm, which meets the requirements, and effectively diminishes the calibration error caused by spectral mismatch.
This paper presented a self-designed scanning laser optical tomography mesoscopic imaging system based on LabVIEW and explored its capabilities to image intact biological organs or tissues. The system is consisted of an aligned laser, a four dimension translation stage, a scanning mirror and a photomultiplier tube. The spatial resolution of the system is better than 20 μm with an imaging field of 1 cm. The system operation process and preliminary biomedical applications were demonstrated through the 3-D autofluorescence imaging of a mouse lung. Compared to the traditional biomedical optical imaging techniques, scanning laser optical tomography provides the advantages of high photon collection efficiency, large sample range and easy operation.
In order to solve the problem that stereo matching of binocular underwater image could not meet conventional epipolar constraint in the air, a semi-global algorithm for dense stereo matching of underwater image based on depth constraint was proposed. Firstly, a depth constraint was used to determine the searching area during stereo matching; based on depth constraint area, the absolute difference function and gradient calculation were extended to two dimensional directions and then fused by weighted factor. During candidate searching in the depth constraint area, the winner-takes-all was adopted to get the best line aberration under each disparity and their corresponding cost values, these cost values were regarded as data item of semi-global algorithm and an initial disparity map was obtained. Finally the sub-pixel dense disparity map was obtained by parabolic fit. Experiments were performed on underwater image to obtain dense disparity map, the results show that compare with other semi-global algorithms, the proposed algorithm could greatly accelerate underwater stereo matching and improve accuracy of matching.
Based on the theory of the Fresnel polarization reflectance,the polarization factor was put forward by decomposing the incident light into electric vector, which could affect the intensity of glare and play a leading role during eliminating glare. According to the imaging detection model, the displacement factor was presented, which could change the glare position and the size of the glare area, and play a supplementary role during eliminating glare. The image gray-scale transformation curves under different polarizations and different positions were gained by sampling and contrasting the image datas of a certain object, and these image data were measured in the equivalent environment while different situations. The proposed theory was verified by analysing the relationship of gray-scale transformation curve with polarization and position. The results show that the essence of glare eliminating is reducing the light intensity and contrast between with the glare area and neighborhood region. Furthermore, the joint mobilization of the displacement factor and polarization factor can almost eliminate the glare completely completely.
By analyzing the electronic noise sources of shot noise photodetector based on the L-C coupled transimpedance amplifier circuit, the effect of the parasitic capacitance of the utilized inductance on the electronic noise was theoretically investigated and experimentally validated. The result shows that the parasitic capacitance of the inductor may increase the electronic noise of the detector via increasing the input voltage noise gain of the transimpedance amplifier. Given that the total inductance of the L-C circuit is 1 mH, the contribution to the electronic noise of choosing two series inductor with 0.5 mH each is much smaller than that of choosing a single inductor with 1mH. Furthermore, the higher the self resonant frequency of the inductor is, the smaller the parasitic capacitance and thus the smaller the electronic noise will be. The experiment results show that, at the analyzing frequency of 2.5 MHz, the electronic noise reduction of the two inductors in series with inductance of two 0.5 mH and resonance frequency of 6 MHz can reach up to 3 dB, compared to that using a single 1 mH inductor with the resonance frequency of 1.6 MHz. Under a certain incident optical power, the signal-to-noise ratio of the detector can be thus improved effectively.