With the development of the micro/nano machining technology, various devices tend to be miniaturized and lightweight. Micro-optical elements as one of most important devices, for its easy integration and broad functions, has been extensively studied. Microlens have been widely used in the fields of imaging, detection and sensing. In order to enhance the stability and broaden the application environment of the microlens, fabricating the microlens based on hard and brittle materials is necessary. Hard and brittle material different from soft materials, which have high thermal and mechanical stability, and have the ability used in harsh conditions. In this study, we combined femtosecond laser single pulse fabrication with HF wet etching on fused silica to realized concave microlens on fused silica. Moreover, microlens with different focus can be realized by adjusting fabrication parameters. The results indicated that the fabricated microlens have excellent focusing and imaging properties. The femtosecond laser single pulse fabrication assisted with HF wet etching exhibits high flexibility and shows the huge potential of fabrication micro-optical elements on fused silica.
Monocrystal sapphire have excellent properties such as high strength, hard and brittle, high temperature resistance, chemical corrosion resistance, wear resistance and good infrared transmittance, which are widely used in semiconductor, defense, aerospace and other frontier fields. As a typical hard and brittle material, sapphire has become an obstacle to the development of its application for ultra-precision machining with high efficiency and low damage. Therefore, a suitable method is needed to achieve ultra-precision processing of monocrystal sapphire. Different from traditional machining, laser polishing technology has the characteristics of non-contact processing and no mechanical processing stress, while femtosecond laser processing technology has the advantages of cold processing and no selectivity to the material, so it is suitable for surface polishing of sapphire. In this article, the influence of the femtosecond laser with the center wavelength of 515 nm on the surface polishing of sapphire under different processing modes, scanning interval and scanning speed was studied. By adjusting the laser parameters, the surface roughness of single crystal sapphire was reduced from 1.58 μm to less than 0.3 μm by femtosecond laser polishing.
Micro-optical element has the advantages of miniaturization and integration, has developed rapidly. Many kinds of micro-optical elements have been proposed, designed and fabricated, due to their unique optical properties, showing great application prospects. The Fresnel zone plate (FZP), a kind of diffractive optical elements, which were convenient for design, process, and has the advantages of thin, lightweight, have been attained a lot of researches. Femtosecond laser processing has the ability of flexibility and accuracy, combined with High precision platform with three-axis, which can be used for fabricate FZP array rapidly. In this letter, a novel FZP array with the same focal length on the surface of the fused quartz fabricated with femtosecond laser direct writing by precise control and optimization of femtosecond processing parameters. As formed FZP array exhibited unique optical performance of imaging, which have important applications in the fields of the integrated optical imaging system.
Micro/nanostructure with a subwavelength period can be induced on the material surface by femtosecond laser, named as Laser Induced Periodic Surface Structure (LIPSS). The uniform LIPSS structure act as a grating that diffracts light, which can display vivid structural colors when illuminating the surface with white light. Structural color with periodic LIPSS structure has strong angle dependence, depends on the direction of the LIPSS structure, which provided us with a new method to realize multi-direction micro/nanostructure processing. By changing the femtosecond laser polarization, we can get the periodic micro/nanostructures in different directions. The polarization controllable femtosecond fabrication can be used for multi-pattern fabrication. The structural color with polarization sensitivity, different patterns could be observed in different directions. Moreover, different from other coloration methods, structural color has inherent stability, which have potential application in the fields of anti-counterfeiting, information storage and dynamic display. In this letter, we introduce a half wave plate to adjust the polarization state of the laser, and realize femtosecond laser variable polarization processing multi-pattern on a stainless steel foil.
Fused quartz has been broadly used as a base material for micro-optical components and microfluidic chips due to its high optical transmittance, high hardness and high chemical stability. These characteristics make fused quartz difficult to machine using conventional mechanical or chemical processing technology. When cutting, drilling or surface microstructure machining, it is easy to produce cracks and fractures, which will reduce the machining quality. Femtosecond laser can achieve high-precision, high-quality, and non-contact processing due to its ultra-short pulse width and ultra-high peak power, which giving it unique advantages in the field of micromachining. This paper proposes a method for precision machining of fused silica by femtosecond laser with a center wavelength of 515 nm, the relationship between the depth and the roughness of the micromachining and the processing parameters had been studied. Common micro-optical elements (dammann grating) with high surface quality could be fabricated on the fused quartz surface by the proper processing parameter, which showed a good performance of beam splitting.
In recent years, micro texture has been widely used in bearing and tool friction reduction. Laser machining is one of the most commonly used methods to process micro texture. Aiming at the recast layer and heat affected zone produced in laser texturing process, a water assisted laser processing technology was used to eliminate the adverse effects as much as possible. Taking 304 stainless steel as the research object, the effects of laser processing in the air and water assisted laser processing on the processing area and micro texture edge morphology were compared and analyzed. The influence of two machining methods on friction coefficient of lubrication micro texture friction pair was analyzed. The results show that the water assisted machining method reduces the heat affected zone and the cone angle of the edge. Moreover, water assisted laser processing avoids the generation of micro cracks which is very beneficial to the texture process of laser processing.
Sapphire is widely used in industry, national defense, aerospace, space technology and other fields due to its excellent physical and chemical properties such as ultra-high hardness, good thermal and chemical stability, high transmittance and so on. Because of the brittleness of sapphire, edge collapse and fragmentation are occurring easily during the process of traditional mechanical machining. Therefore, development of a rapid and high-quality processing method has great significance. Compared with continuous / long pulse laser processing, femtosecond laser processing with ultra-short duration and extremely high peak power has the advantages of small thermal effect, high processing accuracy, real three-dimensional and wide material adaptability. In this paper, a method of machining sapphire with a center wavelength of 515 nm femtosecond laser and scanning galvanometer is proposed. The effects of laser power, processing speed and scanning pitch on the machining depth and surface roughness are studied. A 3D structure is fabricated by combining a scanning galvanometer and the XYZ platform with high speed. Finally, two types of arrays of 3D structure have been fabricated on sapphire, which has high machined surface quality.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.