The random antireflective structures are modeled by the analysis of the random morphology distribution. According to the effective medium theory, the transmission of the antireflective structure is calculated by dividing the structure into multilayer, and the dependence on parameters of the subwavelength is analyzed in detail. In the single-variable condition, etching depth, half breadth of distribution, and median of distribution get a positive correlation with the transmittance where the etching depth plays a most important part in enhancing the transmittance, whereas the angle of structures gets a negative correlation. The experimental results coincide well with the calculation and analysis. The analysis offers a theory guidance to fabricate random subwavelength antireflected structures using metal dewetting.
A theoretical model is proposed to analyze the fabrication of metal nanopartical resist by metal nanofilm annealing, which is used in the manufacture of the transmission-enhanced subwavelength structures at the interface of the optical glass. Based on the conservation of volume of the metal before annealing and after heat treatment, the theoretical relationships of the structure parameters between the metal nanofilm and the metal nanoparticles are obtained. The experimental results coincide well with the theory model, which offers a theoretical guidance to fabricate subwavelength antireflected structures with the advantage of low cost achieved through metal nanofilm annealing. By this means, the average transmission of the quartz device intensifies to 97.9% for the structures fabricated on the both sides compared with the 93% for the unstructured one.
To overcome the alignment error caused by the overlay when the conventional electron beam lithography produces the four-step relief structure, the paper did a detailed research on the influence of different accelerating voltage on the exposure depth during the process of exposure. Therefore, it drew out the limit value of exposure depth under different accelerating voltage and the relationship between the electron beam energy and critical exposed dose. Through the analysis of the experimental results, it worked out the optimum process parameter combination of exposure. The accelerating voltage of the first exposure was 5keV and the exposed dose was 100μC/cm2, while the second accelerating voltage was 15keV and the exposed dose was 150μC/cm2. Finally, the four-step relief structure was made on the resist layer and this structure met the needs of the graphic transfer process on the etch mask.
With the enormous expansion of laser usage in medicine, industry and research, all facilities must formulate and adhere to specific safety methods that appropriately address user protection. The protective ellipticalal microstructure with grating is a novel technology which can provide the principal means of ensuring against ocular injury, and must be worn at all times during laser operation. On the basis of Fresnel's law and the diffractive law, Solidworks and Lighttools software are applied to design the elliptical micro-lens array and correspondent grating. The height of the microstructure is 100um and its period is 3mm. The period of grating is 5um. It is shown that the amount of emergent light of a specific wavelength (1064nm) can reflect more than 40° from the incident light through simulation, while the incident light is perpendicular to the microstructure. The fabrication adopts the ultra-precision single point diamond method and injection molding method. However, it is found in the test that the surface roughness has a serious effect on the angle between the emergent and incident light. As a result, the element can reflect the vertical incidence beam into a tilted emergent beam with a certain angular degree , as well as protecting users from laser damage injures.
To minimize the risk of laser accidents, especially those involving eye and skin injuries, it is crucial to pay more attention to laser safety. To control the risk of injury, depending on the laser power and wavelength, a number of required safety measures have been put forward, such as specific protection walls, and wearing safety goggles when operating lasers. The direct reflection columnar microstructure can also be used for laser safety. Based on mathematical foundations , a columnar microstructure is designed by the optical design software LightTools. Simulation showed that there is a tilt angle between the emergent and incident light, the incident light being perpendicular to the microstructure, as well as the phenomenon of no direct reflection happened. A novel testing platform was built for the columnar microstructure after it was machined. The applied testing method can measure the angle between the emergent and incident light. The method lays the condition for the further research. It is shown that the columnar microstructure with no direct reflection can be utilized in laser protection systems.
Triangular Pyramid Microstructure Array has the obvious effect that the light can be emitted uniformly. We use hot embossing technology to produce the Triangular Pyramid Array on PMMA, which the period of microstructure is 50μm and the height is 20μm. The film can replace spherical micromirror array film, and then the transmission of light can be improved by 2.2%. The results showed that under certain temperature conditions there is a matching relation between PMMA and mold about the thermal expansion coefficient, and the pressing temperature has great influence on the roughness of the microstructure surface.
In view of the special requirements of the high power laser spectral bands and the incident angle, plate dual wavelength laser high reflecting membrane on the K9 optical glass by using electron beam evaporation deposition. Under the condition of vertical incidence, the reflectivity of 532 nm wavelength is higher than 90%; Under the condition of plus or minus 45 ° incident angle, the reflectivity of 1064 nm wavelength at near infrared band is higher than 99.9%. Through material selection, optimization of process parameters and the method of the ion source assisted deposition to improve the membrane layer density and membrane base binding strength, laser-damaged threshold and meet the requirements of the use of optical instruments under certain environmental conditions.
By using Radio Frequency and Plasma Enhanced Chemical Vapor Deposition(RF-PECVD), GaP film is fabricated on ZnS substrate. Under low load condition, the film features Vickers hardness of 750kgf/mm2and film thickness of 10μm. With designed and fabricated DLC/GaP/ZnS film system on ZnS substrate with thickness of 4.2mm, the average transmittance in the bandwidth 8~12μm reached 80.4%. It is indicated by the study of deposition rate of GaP film, optical and mechanical properties and anti-rain erosion and anti-sand erosion that the film growing rate will be faster with the increase of RF power and the deposition rate will be decreased because of the increase of substrate temperature, so it is as the lab atmospheric pressure increase. However , it has more defects in films with the increase of RF power and this results in more absorption, reflection and scattering in the IR transmittance. The higher lab atmospheric pressure and vacuum is, the less impurity in the deposited film will be. GaP film has the ability of protecting ZnS substrate from rain erosion and this ability increases by the thickness of film. And the combination of DLC and GaP has excellent property in anti-sand erosion.
Photoresist spherical microlens array pattern can be fabricated by using multiple mask photoengraving and thermofusion forming process. By reactive ion beam etching, the spherical photoresist microlens array can be transferred effectively to a quartz substrate. The experimental parameters of the fused quartz microlens are the mean curvature of 40μm, mean bottom size of Φ56μm, mean apex height of 10.6μm.Scanning electron microscope (SEM) and surface contourgraph show that the pattern of spherical microlens array prepared is regular and well distributed, the configuration of each
fused quartz microlens is clear. Its surface is smooth and sleek. Experimental results show that by controlling amount of exposure according to spatial distribution, any surface structure which meets demands can be fabricated on photoresist of a certain thickness. In the process of microlens array pattern transfer by using reactive ion beam etching, etching parameters can be adjusted independently and controlled accurately. In the process, various technical processes can be schemed according to various demands, the best etching technique can be selected. In this paper, main process of microlens array fabrication is narrated. Main factors with influence on fabrication are analyzed.
The line width and period of the shield film were designed and optimized based on the principle of microwave transmission. The photolithography technology has been used to generate a photo mask. Then the mask was duplicated on the anti-refection coated fused silica substrate by adding metal and protective coatings with RF sputtering technology, followed by photoresist removing and other procedures. Finally, a high precision and dense metal shield film were developed on the substrate. A transmission of about 97% has been tested in the final result. A surface resistance of 30Ω/square has also been obtained. The microwave of 2.45GHZ has been completely shielded from radiation.
Inhomogeneous GexC1-xfilm has been prepared by making use of reactive radio frequency magnetron sputtering method. In 8 ~ 12 μm waveband, average transmission rate after film sedimentation on CVD/ZnS single surface is 79.1%, larger than that before filming at 7.8%. As a result of experiments, when ratio of reaction gas flow rate CH4/Ar+CH4changes, refraction ratio of GexC1-x film varies in range of 2.4 ~ 4.1 according to the difference of component X. It makes design of multilayer films and preparation of wide waveband inhomogeneous films very easy. Factors influence transmission rate of GexC1-x film, relationship between refraction ratio of film and ratio of reaction gas flow rate, relationship between film sedimentation speed that corresponds to different refraction ratio and ratio of reaction gas flow rate are analyzed and discussed in this paper.
Infrared AR and protective complex film is coated on the MgF2 substrate associated with ion source aid technology. The complex film is composed of multilayer dielectric film and super hard protective film. The function of dielectric film is antireflection while the super hard film is used as protective layer. Through analyzing the stress match, bond strength and binding force which exist between film and substrate as well as among layers, optimum materials are selected. Efficient antireflective and protective function are realized when the best technological parameter is chosen. The result of the experiment indicates that the reflection of single facet is reduced from 2.5% to 1.5%. Moist and thermal test as well as high and low temperature test have passed. The synthetic result of the experiment is also provided.
Based on reactive ion etching (RIE) technology, a 2-D symmetric tetragonal and columnar subwavelength surface relief structure for infrared antireflection can be made on silicon wafer. By analyzing the impact on etch rate, anisotropy and uniformity caused by some technological parameters in reactive ion etching (RIE), parameters such as etchant gas, concentration and flow rate of the gas, pressure of reaction room and radio-frequency power density can be selected. Meanwhile, surface structure appearance, parameters and infrared transmission performance of etching sample have been measured, and the measure results have been analyzed according to technological demands.
Composite of diamond film on substrate surface of single silicon is studied with method of Heat Filament Chemical Vaporized Deposition, for the purpose of application in optics. Discuss the questions such as the dependent relationship of the quality of diamond film to the carbon source gas, the technical measures to increase the depositing speed of the diamond film and to depress or decrease graphite growth on the substrate, the temperature suitable for the diamond growth on the substrate, and the influence of damage degree of defects of substrate upon the properties of diamond, etc. Besides, the infrared absorption is analyzed, which is brought about by intrinsic defects of diamond film formed in this composition and by impurities, such as non-quantity of H and N, etc., which are brought about by the influence of growth condition.