PHOTOCHEMICAL FABRICATION OF AMORPHOUS SEMICONDUCTOR BY FEMTOSECOND LASER EXPOSURE

飞秒激光曝光光化学制备非晶半导体

• 批准号: 13650790
• 负责人: SUZUKI Yoshiro
• 金额: $ 2.18万
• 依托单位: MIYAGI NATIONAL COLLEGE OF TECHNOLOGY
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 2001
• 资助国家: 日本
• 起止时间: 2001 至 2002
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-13650790/
• 关键词: As_2S_3; femtosecond laser; chalcogenide glasses; photo-expansion; glass fabrication; two-photon absorption; light exposure

The photo-expansion an volume increase by light exposure in chalcogenide glasses has received renewed interests from viewpoints of application to glass fabrication. The photo-expansion occurs through not thermal but photochemical processes, and the expansion is restricted to illuminated fractions of glasses. Utilizing these characteristics, formation of micro-optical devices was successfully demonstrated. However, since one-photon processes with cw-light were used for the electronic excitation in most previous studies, the wavelength matching of exposing light to the absorption coefficient of glasses restricts their performance applicable glass species, sizes, and fabrication times. To extend the applicability of photoexpension to glass fabrication, we have proposed in this study to use pulsed laser light with transparent wavelengths for exposure. The band to band excitation is expected through multi-photon processes with the pulsed laser light. Since the absorption coefficient for the multi-photon process depends on the photon density, the exposure time and the penetration depth can be controlled by the laser flux. Since the multiphoton processes enable band to band excitation only if their sum photon energy exceeds the optical gap of the glass, various species of glasses can be fabricated with an identical laser. We exposed As_2S_3 glasses with femtosecond Ti-sapphire laser light and observed the transformation of the glass surface with a laser microscope. Expansion as high as 0.9μm was detected after exposure with 0.41mW laser light for 128s. Laser power dependence of the growth rate of the expansion and the laser transmittance showed that the photo-expansion is induced mainly by a two-photon absorption process of the laser light.

从玻璃制造应用的角度来看，硫属化物玻璃中的光膨胀（即通过曝光引起的体积增加）重新引起了人们的兴趣。光膨胀不是通过热过程而是通过光化学过程发生的，并且膨胀仅限于玻璃的受照部分。利用这些特性，成功地展示了微型光学器件的形成。然而，由于在大多数先前的研究中，使用连续光的单光子过程用于电子激发，曝光光的波长与玻璃吸收系数的匹配限制了其性能、适用的玻璃种类、尺寸和制造时间。为了扩展光膨胀在玻璃制造中的适用性，我们在本研究中提出使用透明波长的脉冲激光进行曝光。预计通过脉冲激光的多光子过程可实现带间激发。由于多光子过程的吸收系数取决于光子密度，因此曝光时间和穿透深度可以通过激光通量来控制。由于多光子过程只有在光子能量总和超过玻璃的光学间隙时才能实现带间激发，因此可以使用相同的激光器制造各种玻璃。我们用飞秒钛蓝宝石激光对As_2S_3玻璃进行曝光，并用激光显微镜观察玻璃表面的变化。 0.41mW 激光照射 128 秒后，检测到膨胀高达 0.9μm。膨胀增长率和激光透射率的激光功率依赖性表明，光膨胀主要是由激光的双光子吸收过程引起的。