In this Letter, we investigate the packet error rate (PER) performance of digital pulse interval modulation (DPIM) for free-space optical (FSO) links under the combined effect of turbulence and pointing errors. The theoretical model is developed by considering the effect of some important parameters, including turbulence condition, beamwidth, receiver aperture size, jitter variance, data rate, transmitted optical power, etc. A closed-form average PER expression for DPIM is derived for this fading channel. The results of numerical simulation are further provided to verify the validation of our model. This work can be helpful for selecting DPIM in the FSO system design.

Partially coherent vortex beams are generated by the illumination of high-power red-color light-emitting diodes. We investigate the influence of correlation property of partially coherent vortex beams on intensity distribution. The correlation property of partially coherent vortex beams are modulated by adjusting the propagation distance of the incident light. Effects of the topological charge and propagation distance of vortex beams on the intensity are also studied. Experiment results are consistent with theoretical simulations.

This paper proposes a novel method of multibeam laser heterodyne measurement for an electrostriction coefficient. Based on the Doppler effect and heterodyne technology, loaded with the information of length variation to the frequency difference of the multibeam laser heterodyne signal by the frequency modulation of the oscillating mirror, this method can obtain many values of length variation caused by different voltages after the multibeam laser heterodyne signal demodulation simultaneously. Processing these values by a weighted-average method, it can obtain length variation accurately, and eventually obtain value of electrostriction coefficient of metal by the calculation. This novel method is used to simulate measurement for electrostriction coefficient of PZT under different voltages by MATLAB, and the obtained result shows that the relative measurement error of this method is just 0.98%.

Photoresponse of large-area multi-walled carbon nanotube (MWCNT) films is explored under laser illumination. The experiment shows that the photo-induced current shows nearly linear response to the bias voltage. The photocurrent depends on the laser illumination spot position, with the maximum photocurrent occurring at the metal–film interface, while the minimum photocurrent is observed between two electrodes. We are attributing this photo-generated exciton due to Schottky junction between Al electrodes and the CNTs, and electron's concentration effect. The sample device shows photo responsibility of 521 mA/W at a bias voltage of 2V, which indicates that this device can be developed as a position-sensitive photodetector.

We propose a novel and compact broadband 1×3 beam splitter (BS), which is based on optical tunneling between neighbor and parallel waveguides; thus, it is used to couple energy from one waveguide to another. This device consists of three parallel planar waveguides, in which the energy is transferred in a coherent fashion, so that the direction of propagation is maintained. For complete energy transfer to occur between the neighbor waveguides, they must have identical propagation constants. Thus, indices and height of the waveguide layers are controlled very carefully to provide matching propagation constants. The total length of BS is only about 7 μm. The simulation and analysis show that the BS for transverse magnetic (TM) light at a wavelength of 1.55 μm is designed to split incident light into three beams, whose power is 20, 34, and 18%, respectively. The wavelength bandwidth reaches up to 52 nm with an increase in wavelength from 1.49 to 1.542 μm, in which the maximum power difference of three output ports is less than 10%; moreover, the minimum is nearly 0. BS designed here particularly suits for optical communication and optical information processing.

Fiber Bending causes the bending loss, which mainly reduces the optical signal noise ratio (OSNR) of the optical transmission signal. When the fiber is bent to a certain degree, it will cause an interrupt signal. In this paper, we do the theoretical analysis and simulation for fiber bending, and present some engineering application examples.

Based on Software defined network (SDN), we brought up the NetWork Test Tools for communication networks. It is an innovative application of SDN, which can support the application traffic test.

We propose and experimentally demonstrate a novel approach to measure the Er3+ concentration in Er3+-doped silica fiber by fiber Bragg grating Fabry-Perot (FBG-FP) cavity ring-down spectrum. The relationship between the cavity ring-down time and the Er3+-doped concentration is derived. The results demonstrate that the cavity ring-down time is a function of the temperature of FBG, and an Er3+-doped concentration of 0.3 × 1025 m-3 at the FBG operation temperature of 25℃ is obtained, which is consistent with the commercial Er3+-doped silica fiber parameter. The results obtained have theoretical guidance and develop a new method to measure the ion doped concentration in solid matter.

In order to increase the anti-counterfeiting performance of optically variable devices, the innovative interference security image structures based on metamerism have been developed. In this letter, we show a pair of all-dielectric metameric filters offering a hidden image effect with the color shift at a specific angle of observation. These filters are designed by two materials TiO2/SiO2 based on the different angle color target optimization. The 6-layer- and 9-layer stacks are achieved and the performance of prototype filters prepared by remote plasma sputtering is shown. The color difference index of the experiment is up to 1.19, which shows good metameric matching effect.

We propose a reconfigurable 8PSK/8QAM modulator implementation by employing two cascaded QPSK modulators with an interferometer in between. With simple control of bias voltage of the interferometer, a flexible switching between 8PSK/8QAM can be achieved. The transmission performance of the generated 8PSK/8QAM signals over different link scenarios is compared via numerical simulations. The results reveal that the proposed implementation has the capability of maximizing transmission distance in the case of ynamic optical network.

We propose a dither-free 8-phase-shift-keying (8PSK) generator control scheme for adjusting the bias voltage of Mach–Zehnder modulator (MZM) and the electrical driver signals of two cascaded phase modulators (PMs). The control module includes a delay-line interferometer (DLI), a balanced photo-detector (BPD), and asynchronous sampling data processing. Both analysis and simulation results show that the bias voltage and the driver signal amplitude control can be achieved independently between these cascaded modulators with only one tap point and one control configuration. Finally, the influence of the bit number of A/D converter (ADC) for asynchronous sampling is also discussed for the practical implementation.

In this study, we propose that by diminishing only the pitch of the innermost air-holes-ring of a HF1 photonic crystal fiber, both an effective mode area up to 100 μm2 at 1.55 μm wavelength and nearly zero dispersion of 0.2 ± 1 ps/(km·nm) within a spectrum range of 1.23–1.65 μm can be achieved simultaneously. Because only one parameter is needed to be tuned in the proposed design scheme, the fiber would be easier to be fabricated compared to other fibers using either multiple changing parameters or additional kinds of materials and would have potential applications in optical communications.

A high-performance compact vibration sensor based on fiber Bragg grating (FBG) is designed. The acceleration sensitivity of the FBG vibration sensor is measured to be larger than 30 pm/g. From 10 Hz to 250 Hz, a quite flat frequency-response curve can be obtained with additional damping, which suppresses the resonance peak effectively. A phase-generated carrier (PGC) demodulation technique realized by compact reconfigurable input and output (RIO) system is applied in our sensing system.

We propose, fabricate, and demonstrate a compact fiber-tip Fabry-Perot interferometer of microcavity for high-temperature sensing. The microcavity which can be used for temperature or pressure sensing is fabricated by using arc discharge at the end of a multimode fiber, which is processed with chemical etching. Advantages of the sensor based on the fiber-tip Fabry-Perot interferometer are small size, easy fabrication, low cost and may have potential applications in space-limited and high-temperature environment.

A broadband- and photonic-integrated convenient chaotic-light transmitter with both optical feedback and mutual optical-coupling techniques are proposed. Both numerical simulation and experimental results show that the bandwidth of the presented transmitter is much higher than that of the traditional transmitter with only the optical feedback or the mutual optical-coupling; and the influence of optical feedback strength and mutual optical coupling strength on the bandwidth is also investigated numerically.

Quantitative phase imaging (QPI) of biological cells is an important developing technique. In this paper, a derivative method of phase extraction is put out under several typical blood cells' models, which is completed by numerically simulating the process of QPI. Furthermore, the first-order derivative of the phase is introduced to analyze the cell morphology, and a monocyte model is discussed as an example to demonstrate the method. It shows that the first-order derivative of the phase can be used as a tool for the identification of blood cells.

The application of dark-field (DF) technique with adaptive optics for retinal imaging in vivo is presented to improve retinal imaging contrast. The influence on the imaging contrast introduced by dynamic ocular aberrations should be considered. The qualitative analysis of the influence is discussed. Detail simulation and quantitative analysis are presented. According to our simulation results, when residual aberrations are reduced to less than 5%, it has a little impact on the contrast of DF imaging; while, on increasing the aberrations up to 10%, the contrast of the DF imaging falls off sharply.

We propose modified local mean decomposition to analyze signals of fringe pattern adaptively. It decomposes the signals into a set of functions, each of which is the product of amplitude signal and frequency signal. Then, the physical components of noise and background are extracted according to the corresponding product functions. Moreover, to solve the most likely mode mixing problem, a high-frequency signal is constructed according to the amplitude and frequency characteristics of the intrinsic noise. Using the presented method, carrier signals are recovered accurately as well as the wrapped phase. Compared experiments illustrate the validity of this method.

There is a need to develop a non-destructive and fast detection method for bruising of fruits because the injuries lower quality of fruits, which lead to economic loss. In this paper, we propose a method to detect the bruise on apple surface with hyperspectral imaging technique. A hyperspectral image system consisting of a CCD digital camera, a line scanning spectrometer and a movable platform is designed to acquire the hyperspectral images of injured apples. Two models are established to distinguish the injured area on the surface from the normal area based on image processing technique with spatial clustering and Spectral Angle Mapper Classification (SAM), respectively. The discrimination accuracy of the SAM model is up to 100%, which is much higher than the spatial clustering model.

Laser generation and electromagnetic acoustic transducer (EMAT) detection techniques are combined as a hybrid ultrasonic technique for the inspection of the defects in the steel. Laser transmits through the optical fiber and irradiates on the steel surface. In case of inspection, Rayleigh wave is generated to test the surface defects based on the principle of mode conversion. In order to improve the testing accuracy and signal-to-noise ratio, wavelet soft-threshold method is introduced in the present work. Experimental results show that errors of testing surface defect are less than 10%, which proves laser-EMAT technique to be suitable for nondestructive assessment of metallic materials.

Adaptive optics is implemented in a confocal scanning fluorescence microscopy using a wavefront sensorless correction scheme. Using the image sharpness as the optimization metric, aberration correction is performed to compensate both system- and specimen-induced aberrations by using stochastic parallel gradient descent algorithm based upon Zernike polynomial modes. We demonstrate the idea of using phantom fluorescence samples experimentally. Enhanced imaging contrast and improved signal level are achieved.

We propose a compact hydrogen sensor, based on Fabry-Perot interferometer with Pd/Ag composite film, fabricated by femtosecond laser micromachining and thin-film coating technique. The sensing characteristic of sensor with 150-nm Pd76/Ag24 composite film is studied, and the device is tested to measure the hydrogen volume ratio range of 0-8%. Experimental results show that the response of the sensor is reversible, and the system shows high potential in hydrogen detection.

We propose a simple and low-cost Fabry-Perot (F-P) fiber sensor based on an inner air cavity. The air cavity is fabricated at the fiber-tip by splicing a single-mode fiber and a hollow-core photonic crystal fiber (HC-PCF), with un-collapsed section of the HC-PCF being cleaved. Application of F-P fiber-tip sensor in the external refractive index (RI) measurement is experimentally demonstrated. The sensor exhibits a good linear response and high sensitivity of -54.409 dB/RIU in the RI range of 1.333–1.413. Therefore, it is applied to fiber-optic biological and chemical sensing.

We develop the kinematic model of portable coordinate measuring arm (PCMA) based on the research on its mechanical characteristics and working principle, and present a comprehensive thermally-induced error correction model for PCMA. Based on the model and nominal data provided by a highly accurate coordinate measuring machine, the technique for thermally-induced error compensation of PCMA is presented along with measuring a standard artifact at the corresponding temperature field. Experimental results demonstrate that the deviation of PCMA at different temperatures is controlled in the range of ±10 μm using this technique to calibrate the PCMA.

In present work, we demonstrate that when a transverse magnetic (TM) Gaussian beam is incident to a magnetic metamaterial (MM) slab, it can be completely absorbed at a particular direction, resulting in a unidirectional perfect absorption. The unidirectionality is due to the time reversal symmetry (TRS) breaking nature of the MM; while the perfect absorbing effect is explained by the multiple scattering theory and the effective medium theory. By tuning the magnitude and the orientation of the external magnetic field, the working frequency can be adjusted and the unidirectionality can be reversed. Accordingly, we can design tunable compact optical devices to achieve unidirectional perfect absorption.

Combination of full-vector finite element method with anisotropic perfectly matched layers results in a novel structure of low-dispersion photonic crystal fiber with high birefringence. The negative dispersion can be obtained at a wavelength of 1.55 μm by adjusting the lattice constant Λ and the round air hole diameter d. Numerical results show that the dispersion variation is negative in the C band, the dispersion slope values are between 0.112 and 0.142 ps·km-1·nm-2 over the C band, and the birefringence is 5.7×10-3.

Flat-topped beam theoretical model and unified theory of coherence and polarization of light are used as the bases in examining aberrated, partially coherent, electromagnetic, square, flat-topped pulsed beams focused by a thin lens. This study demonstrates that Astigmatism is not necessarily undesirable in certain circumstances, and a certain amount of astigmatism can be guaranteed a similar spatial envelope of the beams in the geometric focal plane as the source of aberrated, partially coherent, electromagnetic, square, flat-topped pulsed beams. This feature may be useful in determining the fidelity of high-power laser-beam transmission areas.

It is found that application of Retinex color constancy algorithm in machine vision can weaken light interference on printing chromatic aberration. We propose a new method of fusion of Weighted Least Squares and Multi-Scale Retinex in the L*a*b* color space for the purpose of further enhancing the degree of recovery of prints colors. The effectiveness of the proposed method is tested against experiments on images of the same original print acquired in different illuminants. The method exhibits a good application prospect in machine vision in virtue of its great color consistency capability in maintaining the color of the original print.

A planar-hyperlens-based imaging device is presented in this paper. Based on the structure of hyperbolic dispersion metamaterial and with the ability of collecting the evanescent waves from the object, the planar hyperlens can deliver and magnify the super-resolution details of a planar object to the extent that a traditional microscopic objective can resolve them. The super-resolution magnification imaging principle of the device was analyzed, and the relations of the imaging resolution and magnification with the structure parameters of the device were deduced. With careful design, the effectiveness of the device was confirmed in a series of numerical simulations.

In this study, based on magnetic tunable characteristics of nanoparticle magnetic fluid, we design the photonic crystals' defect-localized modes with a defect layer of nanoparticle magnetic fluids. The transmission spectrum of one-dimensional photonic crystals with a defect layer of nanoparticle magnetic fluid is calculated numerically using the transfer matrix method. The results indicate that the wavelength of defect localized modes moves to short wave with the increasing of magnetic field intensity. The maximum variation is 7 nm. When the thickness deviation of defect layer is in the range of 5 nm, the variation of the wavelength is 6 nm. The bandwidth of the defect localized modes is 0.2 nm and its quality factor is of the order of 103. Therefore, the variation of the wavelength of defect-localized modes, which is caused by the thickness deviation of a defect layer, could be compensated by changing the magnetic field. In this study, the defect-localized modes with a certain wavelength are realized.

Re3+, Yb3+ co-doped (Re0.005YbxY(0.995-x))3Al5O12 [Re = Ce, Er, x = 0, 0.02, 0.05, 0.1, and 0.2] transparent ceramics are synthesized by the solid state reaction and vacuum sintering as the down-conversion (DC) materials. The photoluminescence excitation and the photoluminescence spectra demonstrate the near-infrared quantum cutting (QC) and the energy transfer (ET) from Re3+ to Yb3+ in both of these series of samples. The comparison of the near-infrared QC spectra of the two series of samples shows that the Ce3+, Yb3+ co-doped Y3Al5O12 transparent ceramic samples have much higher intensity of the emission spectra in the near-infrared region, and higher ET efficiency than the Er3+, Yb3+ co-doped ones. So, the Ce3+, Yb3+ DC ion pair is a better choice to improve the efficiency of the crystalline silicon-based solar cells.

For linear electrooptic (EO) effect of femtosecond laser pulses that propagates along the direction of non-optical axis in linear-chirped and periodically poled MgO:LiNbO3 (LCPPLMN), we explore the compensation scheme for the phase mismatch and the group-velocity mismatch between the o- and e-light, and discuss the effect of the linear chirp parameter of the LCPPLMN on the waveform of the output o- and e-light. It is found that, for any input pulse duration, the phase mismatch and the group-velocity mismatch can be simultaneously compensated by the optimization of the linear chirp parameter. As a result, high conversion efficiency of linear EO effect can be performed. In addition, we discuss the influence of the linear chirp parameter on the temporal evolutions of the output o- and e-light pulse.

We report on the existence and stability of defect solitons in two-dimensional optical Bessel potentials. It is found that for zero defect, defect solitons are stable in the entire existence domain. For negative defects, defect solitons are unstable in the moderate power region. It is worth emphasizing that for deep enough defects, another unstable domain will emerge in the high power region.

We generate a flat temporal-phase distribution optical pulse by 1.3-mm-long photonic crystal waveguide. The effect of coupled pulse energy on the temporal-phase distribution of the output pulse is analyzed by numeral simulating. Simulation results indicate that the root mean square of the output pulse phase decreases to 0.0095 with the optimum coupled pulse energy, which is about 30 pJ, and the narrowest output pulse width is 418 fs. The generation of a flat temporal-phase distribution optical pulse on-chip scale results in potential application prospect in optical communication, pulse compression, pulse shaping and other nonlinear optical application fields.

Nonlocality control is investigated in nonlinear media using material combination with self-focusing and self-defocusing media, and the controlling effects on the propagation and interaction of the spatial solitons are analyzed by numerical simulation. The propagation is stabilized, the interaction is suppressed by the proper material combination, and the effects of the control depend strictly on material maps.

We investigate the ultrafast nonlinear phenomena of picosecond chirped non-ideal hyperbolic secant pulse evolution in silicon photonic nanowire waveguides with sum frequency generation cross-correlation frequency-resolved optical gating and nonlinear Schr?dinger equation modeling. Pulse broadening and spectral blue shifts are observed experimentally, and they show remarkable agreements with numerical predictions. Nonlinear losses dominate the pulse broadening and limit the spectral bandwidth broadening induced by self-phase modulation. The initial chirp results in noticeable bandwidth compression and aggravation of blue shifts in the presence of nonlinear losses, whereas it plays a negligible role in the output pulse temporal intensity distribution.

Wavefront coding (WFC) is kind of computational imaging technique that controls misfocus and misfocus-related aberrations of optical systems by appending a specially designed phase distribution to the pupil function. This technology has been applied in many fields to increase the performance or/and reduce the cost of imaging systems. The application of WFC technology on an off-axis three-mirror anastigmatic (TMA) system has been proposed in our previous work. In this letter, we describe the alignment, the imaging experiment and image restoration of an actual TMA system with WFC technology.

Demand for large-scale off-axis aspherical mirrors is increasing in next-generation space-borne optical imaging systems. In this paper, a variable-axis single-point grinding strategy is developed for precisely, cost-effectively figuring silicon carbide (SiC) mirror blanks that have high-order high-gradient off-axis aspherical surfaces on a precision five-axis machining center. The grinding strategies also include tool path generation/optimization, feeding direction control and wheel wear reduction/compensation. Applying the developed grinding strategies, by only one grinding cycle, a near-circular Φ372-mm SiC mirror blank is successfully grounded to 7.8 μm in peak to valley, which is comparable to the reported machining accuracy of the BoX? ultraprecision grinding machine. Moreover, the wheel need not have to be dressed during the whole grinding cycle due to the rotary ultrasonic grinding method. Therefore, this paper offers an efficient and economic solution for grinding off-axis aspherical and free from sur to micron-level accuracy, thus significantly decreasing the subsequent lapping/polishing production cycle time.

The removal function test is carried out on the earlier round-pellet polishing pad. The concept of filling factor is introduced to evaluate the removal function obtained from the experiments mentioned in the paper. To improve the filling factor and characteristics of the polishing pad, the pad structure is optimized according to the experimental results of the round-pellet pad. The removal function of the new polishing pad is simulated with MATLAB. The stability experiment is carried out in full aperture at the same time. The fixed abrasive and the slurry abrasive polishing experiment both are performed under the same conditions. Finally, the structural similarity index is introduced to evaluate the similarity between simulations and experiments. The best structural similarity index of multi-square-pellet pad is 0.4257. The comparison results are acceptable and positive. The optimized fixed abrasive polishing pad is proved to be highly promising for large-diameter SiC mirror fabrication.

A graded metallic grating structure acts as a wave trapping system. Different frequencies of THz waves are trapped at different positions along this structured metal surface grating. The real wave propagation speed of such a system is reduced gradually from the light speed in vacuum to zero, which is demonstrated by calculation and simulation. Different frequencies of THz waves are propagated at a designed propagation speed by a partial graded grating according to the practical demand.

In order to meet the requirements of vibration monitoring of large mechanical equipment, the authors design a novel three-dimensional (3D) high-frequency fiber Bragg grating (FBG) accelerometer. First, the operation principle of the sensor is introduced; the theoretical calculation and finite element analysis are performed about its structural parameters in this paper. Second, an FBG demodulation method for vibration signal is studied and a compensation method is put forward to measure the error caused by fluctuation of the light source and line loss. Finally, sensing properties such as amplitude frequency characteristics, sensitivity of the sensor, crosstalk coefficient, space acceleration measurement are tested, and the compensation method for measurement error is validated. The results show that the operating frequency bandwidth of the transducer is 10500 Hz, sensitivity is about 1400 mv/g, crosstalk coefficient is larger than 20.6 dB, and the maximum measurement error of space acceleration is 4.8%, the compensation error is less than 5%. Hence, the sensor is used to monitor the vibration state of mechanical equipment.

A simple, low-cost, and high-efficient method is used for the fabrication of surface-enhanced Raman scattering (SERS) substrates. Silver particles deposited on porous silicon are prepared as a highly efficient SERS substrate by direct immersion of porous silicon in silver solution. The SERS measured with rhodamine 6G as a target molecule is affected by the morphology of silver particles on the top of porous silicon layer. The effect of solution concentration, dipping time, and thickness of porous layer on the morphology of silver particle is investigated. Highly efficient SERS spectra are observed for substrates with porous layer thickness of about 3 μm and incubated in the 50 mM AgNO3 solution for 3 minutes. The SEM images of the substrates show that there are many small Ag particles with the size of a few nanometers among large Ag particles with the size of several microns.

A porous silicon microcavity (PSM) is highly sensitive for sensing applications due to its high surface area and a narrow resonance peak. In this letter, we fabricated the PSM by alternate current density from a low value to a high value during double-tank electrochemical anodization at different electrolyte temperatures. Results show that with the increase of the electrolyte temperature, the rate of the PS etching becomes faster and the refractive index of the PS layer becomes smaller. The thickness of the PS increases faster than the decrease of the refractive index of the PS.

We study all-optical sensing characteristics based on long-range surface plasmon resonance in a four-layered metal-dielectric structure immersed in the liquid to be measured. The resonance peaks in the reflection angle spectra depend on different refractive indices from 1.30 to 1.38, which are calculated and compared in three typical wavelengths of 532, 632.8 and 780 nm, respectively. Compared with 532 nm, the incident light of 780 nm results in an unstable sensing stability, but the resolution enhances two times. The sensitivity of this refractive index sensor at an incident angle of 45° is about 236.7 nm/RIU which uses 532-nm laser as the light source.

The propagation characteristics of lightwave in spatial and temporal domains are reviewed, and a general analogy of spatial diffraction and temporal dispersion is presented in details. By using the transformation pairs of spatial location and time, wave number and dispersion parameter, some more general expressions, such as spot size/wavefront curvature and pulse-width/chirps, space-angle spectrum product and time-bandwidth product, spatial Fresnel number and temporal Fresnel number, focal length of lens and focusing time, are derived.

Doppler spectrum width, which relates to wind turbulence, is one of the essential parameters of coherent LIDAR. Using the Fourier transform theorem and the definition of correlation function, the power spectrum function in the stationary condition is deduced. The effects of pulse shape, pulse duration and the windowing are included. The spectrum width resulted from the turbulence is given under Kolmogorov turbulence model. Based on the power spectrum theory, the spectrum broadening by different pulse shapes and pulse durations are calculated. To validate the accuracy of the theory and usage in the retrieval of turbulence parameters, the numerical simulations of the echo signal are carried out in turbulence conditions. The statistics characteristics of the spectrum broadening from laser pulse shapes and durations are inverted and compared. The results show that the spectrum broadening varies greatly due to the selection of pulse shapes and pulse durations, and the numerical simulation is in accordance with the theory results.

We develop optical fiber nanoprobe by spark fused taper and acid corrosion methods. By coupling with 3-aminopropyltrimethoxysilane, gold nanoparticles are solidified onto the surface of fiber optic and then the optical fiber sensor is prepared using surface-enhanced Raman spectroscopy (SERS) measurement of the cell solution. The SERS of the esophagus cancer cell solution is then measured by direct detection and fiber detection methods, and the relationship between SERS fiber detection and the length of optical fiber ensor is studied. This is helpful for the SERS measurement of tissues and organs using the optical fiber sensor.

In this letter, we introduce the project of multilayer dielectric film based on conventional optics to design laser-protective coating. A desired material with an ideal refractive index is used to optimize the design results. Two film-thickness masks are designed to improve the uniformity of large-size coatings. Experimental results show that the average spectral transmittance from 400 to 1000 nm is higher than 85%, the attenuation of high-energy laser at both 532 and 1064 nm is larger than 98% in the range of ±20° and the film uniformity of large area is more than 98.2%. The coating performance observed meets the requirements of both utilization of solar energy and laser protection.