Laser writing system for fabrication of diffractive optics elements

We report a laser writing system for fabrication of diffractive optical elements with He-Cd laser. The wavelength of the light source is 441.6 nm. The output beam is collimated into parallel light with uniform intensity distribution after passing through the spatial filter with a pinhole of 25μm and the collimating device. A microscopy objective lens with numerical aperture (NA) of 0.65 is used to focus the beam into a small diffraction spot. Any pattern can be written with this system. Experimental results are presented.The written gratings and the phase patterns were verified with a conventional optical microscopy and the Taylor Hobson equipment.     

基于塔尔博特效应的分波器和分束器

给出一个单一器件同时具有分波器和大规模分束器功能的实验结果，其设计原理基于塔尔博特自成像效应。以两波长为例，通过改变分数塔尔博特距离和光栅周期等参量，实验上实现了两波长光信号在空间上的交叉分离。     

Grating imaging scanning lithography

We present a grating imaging scanning lithography system for the fabrication of large-sized gratings. In this technology, ±1-order diffractive beams are generated by a phase grating and selected by a spatial filter. Meanwhile, a 4f system enables the ±1-order diffractive beams to form a grating image with a clear jagged-edge boundary on the substrate. A high-precision two-dimensional （2D） mobile stage is used for complementary cyclical scanning, thereby effectively eliminating image stitching errors. The absence of such errors results in a seamless and uniform large-sized grating. Characterized by a simple structure, high energy use, and good stability, this lithography system is highly relevant to the high-speed and cost- effective production of large-sized gratings.     

基于超精密激光直写系统制作二维光栅

二维光栅是光刻机光栅尺系统的核心元件。搭建了超精密激光直写系统,基于二维超精密工件台,通过旋转基片90°进行两次曝光,制作出栅线密度为1200 line/mm的二维光栅掩模。原子力显微镜和扫描电镜结果表明,所制作的掩模轮廓清晰,空间分布均匀。实验结果证明了超精密激光直写系统能够制作出二维光栅掩模,在制作大尺寸、高精度二维计量光栅方面有着广阔的应用前景。     

Narrow-wavelength-spread spectral combining laser with a reflector for a double pass with a single grating

We proposed a novel wavelength-spread compression technique for spectral beam combining of a diode laser array. A reflector, which is parallel to the grating, is introduced to achieve a double pass with a single grating.This facilitated the reduction of the wavelength spread by half and doubled the number of combined elements in the gain range of the diode laser. We achieved a power of 26.1 W under continuous wave operation using a19 element single bar with a wavelength spread of 6.3 nm, which is nearly half of the original wavelength spread of 14.2 nm, demonstrating the double-compressed spectrum capability of this structure. The spectral beam combining efficiency was 63.7%. The grating efficiency and reflector reflectance were both over 95%; hence, the efficiency loss of the double-pass grating with a reflector is acceptable. In contrast to double-grating methods,the proposed method introduces a reflector that efficiently uses the single grating and shows significant potential for a more efficient spectral beam combining of diode laser arrays.     

基于达曼光栅的动态光耦合器

提出了一种基于达曼光栅的动态光耦合器,通过控制装置中达曼光栅位移参量,可实现入射光束的分束或合束以及两者之间的动态转换。适当选择达曼光栅类型可实现任意N×M的动态光耦合。实验中以1550 nm光波长为例,对1×8达曼动态光耦合器进行测量,测得其实现光开关功能时插入损耗为0.43 dB,实现光分束功能时均匀性达到0.03,单路插入损耗均值为10.5 dB。该实验装置易于调节、体积小、能耗低,且关键元件达曼光栅制作工艺成熟,易于批量化生产。特别是在实现中大规模光交换阵列时,该方案就具有更明显的优越性,有实用意义。     

Optically fixed photorefractive correlator

An optically fixed photorefractive correlator is presented,where two-centre non-volatile holographic recording is employed to write and fix the matched filter in doubly doped LiNbO3 crystals.This correlator shows good correlation characteristics and insensitivity to the writing beam during readout.It can be used in cased requiring stability and not requiring modification for a long period,and it is refreshed optically when new information needs to be registered.     

光折变晶体中全息相位栅的包迹

联立稳态带传输方各程和波方程,基于Kukhtarev模型和Moharam的场函数,以光强调制度为主要变量,求得了适用于任意干涉光强调制度及光激发效率为任意常数时的光折变晶体中全息相位栅包迹的解析解。在此基础上,分析了非破坏性读出情况罡的衍射效率。     

Femtosecond laser induced microripple on PDMS surface

We find the femtosecond laser induced microripple beside the focused femtosecond laser spot and along the movement direction of the laser spot on polydimethylsiloxane （PDMS） surface. The microripple may be due to the melting of PDMS induced by femtosecond laser pulses and the subsequent cool-down solidification of the melting PDMS along with the movement of the femtosecond laser spot. This result will be helpful to understand the interaction between the femtosecond laser and the polymer.     

Wide band polarizer with suspended germanium resonant grating

An ultra broad band polarizer that operates in the telecommunication wavelength band is proposed.This device,which consists of a single suspended germanium resonant grating layer,is designed using the inverse mathematical method and the rigorous vector diffraction theory.Calculated results indicate that the ultra broad band polarizer exhibits extremely high reflection(R > 99%) for TE polarization light and high transmission(T > 99%) for TM polarization at the wavelength range greater than 300 nm,and it has an extinction ratio of approximately 1 000 at the 1 550-nm central wavelength.The results of the rigorous coupled wave analysis indicate that the extremely wide band property of the TE polarization is caused by the excitation of strong modulation guided modes in the design wavelength range.