A new method for measuring the natural frequency of a complex structure using fiber Bragg grating (FBG) sensor is introduced. The FBG strain sensor is stuck on the surface of the drill block. The natural frequency of the drill is measured to be 23.9 Hz by monitoring the strain change caused by mechanical vibration. It matches the result achieved by ANSYS finite element analysis very well.

Multiple input multiple output (MIMO) technology using phase shift keying orthogonal frequency division multiplexing modulation (PSK-OFDM) in free-space optical (FSO) communication is studied and MIMO-OFDM communication system based on Gamma-Gamma atmospheric turbulence channel is analyzed. A closed-form expression of bit error rate (BER) for FSO communication is derived with Meijer G function. The simulation result shows that MIMO technology which uses PSK-OFDM modulation can reduce BER effectively over different atmospheric turbulence. As the turbulence intensity becomes stronger, the effect of MIMO technology in reducing BER is gradually enhanced.

The relation between groove density error of the Rowland grating and wavelength accuracy for the Paschen-Runge mount is analyzed. An in-situ detection method for interference fringe density of the exposure field with which Rowland grating is made is proposed. A reference grating with expected groove density is put into the exposure field where the photoresist grating is exposed. The interference fringe density error of the exposure field is detected through the deviation between recording beam and its collimating diffracted light. The expression of interference fringe density error and deviation of recording beam′s collimating diffracted light is deduced. It is discovered that the interference fringe density error is related to the deviation of recording beam′s collimating diffraction light, grating curvature radius and exposure wavelength, but not the grating groove density. Taking a Rowland grating with 750.2 mm curvature radius for example, when the exposure wavelength is 441.6 nm, the interference fringe density error can be limited to 0.035 groove/mm.

Compared with the traditional two-dimensional (2D) projection display, three-dimensional (3D) projection display with good market prospect not only enables the observer to see a more vivid projection image, but also provides 3D information. On the basis of principle of information optics, we put forward a process to a 3D holographic projection, which is based on a holographic lens array screen: the images sampled by camera array are transformed and projected by projector arrays to a holographic projection. The projection consists of holographic optical elementsholographic lens array, through which the projection beam is transformed into directional diffraction integral, reproducing the 3D information of the object and realizing 3D projection. The experiment making the holographic lens array is described, which can control the orientation of the projection beam diffraction; and the method of achieving 3D projection by using holographic optical elements is investigated.

A summarized analysis of computer-generated hologram algorithm of three-dimensional (3D) virtual object is presented. Based on the analysis results, 3D object surface is deemed to be a combination of right triangular area units with different shapes and locations. A convenient generation algorithm of computer-generated hologram is derived, and a calculation example of computer-generated hologram of smooth surface of 3D object is also presented. Based on sampling theory, the algorithm of calculating computer-generated hologram of diffuse 3D object is studied, and an example of computer-generated hologram of diffuse 3D object is given.

In order to rapidly and accurately measure the size and the shape of Chinese herbal medicine cell, the digital image-plane holographic microscopy (DIPHM) with spherical reference wave is studied theoretically and experimentally. The results show that: through appropriately adjusting the location of the reference light source, DIPHM with spherical reference wave can rapidly and accurately eliminate the quadratic phase aberration introduced by microscope objective. The automatic procedure for aberration compensation can rapidly and efficiently eliminate the aberration brought by the bias of spherical point source in the reference light path in DIPHM, and then accurate phase reconstruction of the sample can be achieved. Based on the above study, the elliptical typhaceae pollen as a kind of Chinese herbal medicine cell is quantitatively imaged using DIPHM. Through the accurate three-dimensional phase distribution, the morphological image and the size of elliptical Typhaceae pollen are obtained.

For the researches on remote sensing image fusion of low-resolution multispectral image and high-resolution panchromatic image, traditional intensity-hue-saturation (IHS) transform faces a problem of color distortion while the traditional wavelet transform has a problem of blurring. To enhance the spatial resolution of fusion image as well as preserve spectral information of the original multispectral image, a novel efficient algorithm based on IHS and wavelet transform is presented. Firstly the intensity component of multispectral image is extracted. The intensity component is analyzed using principal component analysis (PCA) and the revised intensity component is merged with the panchromatic image based on wavelet transform. The fusion image is obtained via inverse IHS transform. Experiments prove that the proposed method quantitatively outperforms the traditional ones, in terms of geometric, radiometric, and spectral fidelity.

Based on conventional Gerchberg-Saxton (GS) algorithm, transport of intensity equation (TIE) method and accelerated angular spectrum iterative algorithm are introduced to put forward a kind of more accurate and rapid phase recovery algorithm: accelerated angular spectrum iterative algorithm for two-dimensional (2D) phase retrieval from TIE. The intensity distribution of three planes, e.g., an incident plane and two emergent planes, is employed to retrieve the initial phase by TIE and then retrieve the phase of incident optical field by accelerated angular spectrum iterative algorithm. The simulation result shows that this algorithm can retrieve the phase distribution of an arbitrary 2D incident optical field in high accuracy. Through numerical simulation, this algorithm is proved in 2D image phase recovery process to be more accurate and faster and its noise immunityis stronger. In the recovery phase control range, the iteration tends to be stable after 40 steps, and the mean square (RMS) error can be controlled in the order of magnitude of 10-6.

The influence of thulium ion concentration and output-mirror transmittance on Tm:YAP crystal laser output performance is experimentally investigated. Three c-cut crystals in size of 3 mm×3 mm×5 mm with 3%, 4% and 5% Tm3+ (ionic-number fraction) are examined with the transmittance of 5%. Experimental results showed that the best power performance is obtained with the 4% Tm:YAP crystal. By using 24.8 W incident pump power, a maximum output power of 7.5 W is obtained. The slope efficiency is 48.8%. Using different output transmittances of 2%, 5% and 10%, we investigate the laser performance with 4% thulium ion. The results show that with the transmittance of 5%, the highest slope efficiency is obtained.

In the process of laser cladding forming, the performance of the powder-feeding nozzle has an important influence on the quality of cladding molded parts. To explore the key parameters that affect the performance of the powder-feeding nozzle, numerical calculation model is established using FLUENT software. Numerical simulation is performed on powder flow for the powder-feeding channel with different contraction angles and outlet diameters, and the key parameters of the powder-feeding nozzle are determined based on the simulation results. The results show that the contraction angle of powder-feeding channel of 2.5° and the diameter of powder outlet of 1.5 mm are beneficial to improve the powder convergence of powder-feeding nozzle and the cladding forming effect with other process parameters invariable. A powder-feeding nozzle is fabricated based on the obtained key parameters, and the experiment of powder convergence and laser cladding forming is carried out. The effect of powder-feeding nozzle is validated.

Shape correction is an important tool in ensuring the forming precision of sheet metal parts. In order to improve the correction effect and efficiency, a new method of laser correction of thin-walled aluminum alloy part is proposed. When laser beam irradiates the residual stress gathering area of the formed part, the elastic energy in this area is transformed into plastic work due to laser thermal effect, thus the forming error is corrected and the forming precision is improved. The formed part is produced by standard three-point bending test, and then laser beam scans it along the bending line, so that the actual correction values are obtained. The correction effect is discussed through the quantitative analysis of the experimental data. The actual correction rate varies with the choice of material and thickness of specimen. The feasibility of the laser correction technique is verified. Research foundation is laid for further application of laser correction in engineering.

Based on the composite cavity model, the feedback-induced instabilities which may cause coherence collapse in single-longitudinal-mode distributed feedback (DFB) fiber lasers are analyzed. The coherence collapse of DFB fiber laser is detected, and the longitudinal operating mode splitting phenomena of DFB fiber laser due to Rayleigh backscattering and the facet reflection are measured simultaneously. Experiments show that the threshold of the length of the leading fiber cannot exceed 200 m, which keeps quantitative agreement with the results of simulation. The investigation proves the feasibility of the two methods for detecting coherence collapse, i.e., mode splitting method and phase noise method, and provides a guide to the design of DFB fiber laser sensor array.

All-normal-dispersion mode-locked fiber lasers can generate high-energy and high-linear-chirp dissipative soliton pulses, so they have attracted much attention. The generation of dissipative solitons is attributed to an integrated result of all kinds of effects in the laser cavity, such as gain, loss, gain saturation, nonlinear effects and filtering. The effect of filter on the performance of output dissipative soliton pulses is detailedly investigated. Numerical simulation shows that dissipative solitons obtained in the fiber lasers with band-pass filter have narrower pulse duration and broader spectrum width than those from the lasers without a filter. Moreover, the establishing time of stable mode locking is shorter. The peak power of dissipative soliton pulses increases with the filter bandwidth decreasing, while the pulse energy almost keeps invariable within certain range of filter bandwidth. But in the limiting case of narrow filter bandwidth, the pulse energy decreases abruptly due to the large induced loss.

The laser-controlled micro-crystallization technology for hydrogenated amorphous silicon aH-Si thin films is studied. The aH-Si thin films on crystalline silicon (c-Si) are annealed by YAG laser with the frequencies of 4, 8, 10, 12, 15 Hz, while keeping the laser power, pulse width and facula unchanged. The influence of laser frequency on aH-Si thin film crystallization is studied. The analysis of aH-Si thin film microstructure and surface morphology is conducted using X-ray diffractometer (XRD) and atomic force microscope (AFM). The results show that the grain size of the aH-Si thin film becomes larger with the laser frequency increasing from 4 Hz to 10 Hz, and decreases with the laser frequency keeping increasing from 10 Hz to 15 Hz. The maximum average grain size reaches 45 nm in the film annealed by the 10 Hz YAG laser. The sheet resistance of the film generally decreases with the laser frequency in creasing, while the film with the largest grain size obtains the lowest sheet resistance.

Optical coherence tomography (OCT) is an novel optical signal acquisition and processing method which can capture micrometer-resolution three-dimensional images from optical scattering media. Monocrystalline silicon wafers obtained with different texturing time and same corrosion solution are measured by sweep light source OCT. Through processing the OCT acquired data, the quality of monocrystalline silicon in different texturing time can be estimated. It may provide a new method for the test of textured monocrystalline silicon.

A method for attenuating laser power density employing the reflection characteristics of material is studied. By using the classical Phong reflection model, the reflection characteristics of material are theoretically analyzed, and the function describing the relation among power, radiant intensity and observation angle is presented under continuous-wave (CW) laser irradiation. By selecting appropriate parameters of material for the Phong reflection model, the numerical simulation results for the structure for attenuating laser power density are given, such as the three-dimensional (3D) laser beam spatial profile of the structure at the output and the attenuation coefficient at different distance from the output. They are consistent with the experimental results. The research results demonstrate that the structure is suitable for attenuating laser power density and quantitatively measuring laser parameters.

A truncated pyramid is usually used as a secondary optical element in the concentrated photovoltaic system. Usually, the total internal reflection (TIR) condition should be met twice in the design section when designing the truncated pyramid. However, the truncated pyramid is non-rotating axisymmetric relative to the optical axis. The propagation situation of the light in the non-design section is different with the one in the design section. The influence of the truncated pyramid′s non-rotating axisymmetry on the light TIR is studied with the vector method. It is proved that if a light in the design section meets the TIR condition twice, then setting the opposite sidewalls as a group, the light which has the same included angle with the axis in the non-design section meets the TIR condition twice in both groups. This provides a basis for the design of the truncated pyramid secondary optical elements.

Phosphor layer is solidified by ultraviolet (UV) radiation. Experiments are done on various components of UV glue to study the influence of curing on the film transmittance. The best matching ratio to get the highest transmittance is obtained. Mixing phosphor with the best proportion of UV glue, the phenomenon of phosphor sedimentation is observed and it is compared with that of the traditional glue. The optical performance of LED respectively packaged by UV glue and AB glue are measured. Through the measurement results, the influence of UV curing on LED optical performance is analyzed. It is found that the phosphor sedimentation phenomenon is more obvious in the AB glue than that in the UV glue. While compared with AB curing LED, the UV curing LED has no significant discrepancy on the optical properties such as the distribution of the LED spectrum, color rendering index, correlated color temperature and luminous flux.

Application of chemical/biological agents in terrorism and unmilitary fields induce serious impact to the public safety. Principles of laser warning and detection technology for chemical/biological agents based on Mie scattering signals, Rayleigh scattering signals, Raman scattering signals, absorption signals and laser induced fluorescence signals are described. The key technologies in the laser warning and detection system are analyzed, the laser warning and detection technology development profiles in the United States, Russia, German and France are introduced.

Nanoimprint lithography (NIL) is a nano-size scale fabrication technology which could fabricate patterns mechanically with such advantages as simple machines, easy operation, good repeatability and low costs. Meanwhile, it can achieve precise nanopatterns on whole 2-inch or 4-inch wafers (1 inch=25.4 mm), which makes it possible to fabricate nano-size optoelectronic devices with high throughput and low costs. On the other hand, solid state lighting using compound semiconductor materials is an attractive field both in academia and industry of the world. High-efficiency light-emitting diodes (LED) are taking place of traditional lighting sources，in order to realize high-quality, green lighting. This review covers the basic principles and process of nanoimprinting, with an emphasis on the application of nanoimprinting for the new inorganic and organic LED, achieving the nano-LED structures and photonic crystals to improve the efficiency of optoelectronic devices.

Biospeckle is a phenomenon generated by laser light scattering in biological tissues or surfaces. The shape and intensity of speckle pattern vary with time, and this variance is believed to have relation with the biological activity of the sample. Biospeckle is a kind of optical measuring technology which has many advantages such as whole field measuring, non-contacting, real time, etc. Hence it is applied widely in the areas of biomedicine and agriculture. A brief introduction to the theory is presented. The research progress and achievements are also introduced. The theory and characteristic of main image processing methods are analyzed and compared.

Distributed optical fiber vibration sensing (DOFVS) technology is the research focus of the optical fiber sensing field in recent years, and it has been widely used in many application areas such as perimeter security, pipeline maintenance and engineering structural health monitoring. This paper summarizes the features and research status of optical-fiber interferometer-based distributed vibration sensing technology, emphasizing on the new progress in the past few years. The fundamental working principles, location methods and main technical specifications of the novel system configurations and sensing theories are analyzed in detail. Moreover, the purpose and implementation process of the novel data-processing algorithms are also introduced. The developing trend and application prospect are presented and discussed.

High-quality Yb-doped large-mode area silica glass optical fiber has attracted much attention in the world over the past decade, due to its application in high-power fiber lasers and amplifiers. In this paper, several Yb-doped large-mode area silica glass optical fibers which have been successfully used in high-power laser systems are introduced. The development of Yb-doped large mode area silica glass optical fiber in China is analyzed. Finally, it is forecasted that the Yb-doped large-mode area silica glass optical fiber has wide application prospects.

As an important tool of space-based remote sensing system, space-borne laser altimeter has a lot of advantages, such as high accuracy, high resolution and ability of vertical resolution. So it has unique advantages and bright prospect in topographic mapping, deep-space exploration, global alert and monitoring and so on. The development of space-borne laser altimetry is briefly introduced, and the working principles of space-borne laser altimeter and push-broom laser altimeter using multiple beams are given respectively. For the latter, key technologies are analyzed, such as the transmission technology of multiple laser beams, the laser technology, the array detecting and receiving technology of multiplexing signals and so on. The application of space-borne laser altimetry is also described. Finally, the prospect of space-borne push-broom laser altimetry based on multiple beams is predicted and the development of space-borne laser altimetry in china is presented.

The effective coupling between waveguide and optical fiber is the key to the commercialization of integrated optical devices. The coupling efficiency not only directly affects the performance of these optical components, but also is a problem that must be solved in optical fiber communication and integrated-optics fields. In the case of fiber and waveguide in alignment, the mode-field mismatch loss is the main factor affecting the coupling efficiency. We mainly review some domestic and foreign methods of coupling between waveguide and optical fiber, including the wedge-shaped coupler, lens coupler and grating coupler. Summary and comparison are given for these methods. The result shows that a simply-fabricated reverse cone-shaped coupler has an absolute advantage in improving the coupling efficiency, so it has a higher application value in optical-fiber communication and integrated-optics field.

The introduction of low-dimensional nanostructures provides a potential application to the development of intermediate band solar cell, which is one of the hottest researches in the third-generation photovoltaic power field. By analyzing the mechanism of quantum dot intermediate band solar cell, the usual preparation and characterization are introduced. It is significant to review the late research development of a typical III-V compound and silicon-based structure of quantum dot intermediate band solar cell, especially the various methods proposed by researchers to improve the battery. In addition, a new kind of structure named quantum ring is briefly overviewed though it is a deformed quantum dot. This new nanostructure with its most significant feature that has no stress is an effective means to solve the quantum dots stress accumulation. Finally, some remarkable research problems are also addressed.

Novel quantum-dot optical amplifiers obtain development and applications, because they possess the advantages of broader bandwidth, higher gain, lower noise and higher power amplification. Starting from the structure and main characteristics of quantum dots, this paper summarizes the research and application status of several common quantum dots in optical amplifiers. Whereafter, the basic structure and working mechanisms are emphatically introduced for the quantum-dot semiconductor optical amplifiers and fiber amplifiers. The spectral characteristics of CdSe/ZnS quantum-dot optical fiber are briefly described. Some problems awaiting solution to further developing quantum-dot optical amplifiers are proposed and an outlook is given for quantum-dots applications in optical communication field.

Chalcogenide glass fibers have attracted great attention in the infrared (IR) sensing fields, such as liquid monitoring, gas checking, biochemical, microbiology and medicine, for their advantages of wide infrared transmission band, resistance to corrosion, devitrification and not sensitive to microwave radiations. We firstly review the research progress of sensors using chalcogenide glass fibers, and then introduce their working principles. The research of chalcogenide glass fibers is reviewed in terms of sensor application. Their development prospects are also discussed.

In order to obtain spectral response curve of grating dispersive imaging spectrometer for laboratory calibration by back illuminated thinned 1243×576 detector array, a set of spectral calibration device which implements a spectral calibration method with the accuracy of ±1 nm is designed. Factors influencing spectral response including the light source spectral distribution, the grating efficiency, spectral bandwidth of the monochromator, the spectral-line bending and fringes phenomenon are evaluated, and for these confounding factors we propose a mathematical model for calibration. The spectral calibration results show that: the pixel average spectral bandwidth is 2.20 nm, the maximum value of spectral-line bending is 0.925 nm and the bending direction is in line with the theoretical direction. Repeating the test with the mercury lamp, the spectral uncerainty is less than 0.6 nm.