以提高共焦差动并行激光直写中光束刻写质量为目标, 分析设计了调平聚焦伺服控制系统。采用柱面镜作为像散元件, 与四象限光电探测器结合, 利用差动像散检测方法和比例积分微分(PID)反馈算法减少光源和外部干扰的误差, 获得高灵敏度、高精度、高稳定性的探测曲线。通过优化光学设计参数, 本系统能获得具有高灵敏性与一致稳定性的探测曲线, 探测范围为3 μm, 静态聚焦误差可达 ±5.0 nm; 动态聚焦压电陶瓷(PZT)伸长量可保证在焦深范围内, 焦点位置辨别精度可达纳米量级, 可探测调平台的倾斜角和俯仰角在0.01 mrad左右。利用该系统可实现光栅的刻写, 进一步为更大尺寸、更高密度的光栅刻写提供依据。

Scanning Dammann lithography (SDL) is proposed and implemented, which uses a Dammann grating to generate multiple beams with sharp step boundary for writing large-sized gratings efficiently. One of the most attractive advantages is that this technique can accelerate the writing speed, e.g. 1 \times 32 Dammann grating can be 32 times faster than the single laser scanning system. More importantly, the uniformity of the multi-beams-written lines is much better than the single laser beam scanning system in consideration of the environmental effects such as air turbulence, thermal instability, etc. Using the SDL system, a three-port high-efficiency beam splitter at visible wavelengths is fabricated quickly, and the theoretical and experimental diffraction efficiencies are both higher than 90%. Therefore, SDL should be a useful tool for fabrication of large-sized gratings.

The low divergent Dammann grating is researched for the potential applications in aerospace. A laser-beam writing system is developed for writing the low divergent Dammann grating. The uniformity and efficiency of the Dammann grating are presented in this letter. The novelty of this letter is to demonstrate a low-cost and effective method to fabricate low divergent Dammann 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.

A guided-mode resonance (GMR) filter with the same material (Ta2O5) for both the grating layer and the waveguide layer is designed and fabricated. This simple structure is easy to fabricate and can avoid the defects at the grating/waveguide interface using different materials. The spectral response measured with a Lambda 900 spectrophotometer under normal incidence for TE waves exhibits a peak reflectance exceeding 80% at the wavelength of 1040 nm with a full-width half-maximum (FWHM) linewidth of 23 nm. We evaluate the deviations of the fabricated structure from the designed parameters.

采用电子束蒸发(EBE)和离子束溅射(IBS)制备了不同的Ta2O5薄膜,同时对电子束蒸发制备的薄膜进行了退火处理。研究了制备的Ta2O5薄膜的光学性能、激光损伤阈值(LIDT)、吸收、散射、粗糙度、微缺陷密度和杂质含量。结果表明,退火可使电子束蒸发制备的薄膜的光学性能得到改善,接近离子束溅射的薄膜的光学性能。电子束蒸发制备的薄膜的损伤阈值较低的主要原因在于吸收大,微缺陷密度和杂质含量高,而与薄膜的散射和粗糙度关系不大。退火后薄膜的吸收和微缺陷密度都明显降低,损伤阈值得到提高。退火后的薄膜损伤阈值仍然低于溅射得到的薄膜损伤阈值是因为退火并不能降低膜内的杂质含量,因此选用高纯度的蒸发膜料和减少电子束蒸发过程中的污染有可能进一步提高薄膜的损伤阈值。

Ta2O5 films are prepared on BK7 substrates with conventional electron beam evaporation deposition. The effects of SiO2 protective layers and annealing on the laser-induced damage threshold (LIDT) of the films are investigated. The results show that SiO2 protective layers exert little influence on the electric field intensity (EFI) distribution, microstructure and microdefect density but increase the absorption slightly. Annealing is effective on decreasing the microdefect density and the absorption of the films. Both SiO2 protective layers and annealing are beneficial to the damage resistance of the films and the latter is more effective to improve the LIDT. Moreover, the maximal LIDT of Ta2O5 films is achieved by the combination of SiO2 protective layers and annealing.

Ta2O5 films were prepared with conventional electron beam evaporation and annealed in O2 at 673 K for 12 h. Laser-induced damage thresholds (LIDTs) of the films were performed at 532 and 1064 nm in 1-on-1 regime firstly, and then were performed at 532, 800, and 1064 nm in n-on-1 regime, respectively. The results showed that the LIDTs in n-on-1 regime were higher than that in 1-on-1 regime at 532 and 1064 nm. In addition, in n-on-1 regime, the LIDT increased with the increase of wavelength. Furthermore, both the optical property and LIDT of Ta2O5 films were influenced by annealing in O2.