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Thin films|30 Article(s)
Te-free SbBi thin film as a laser heat-mode photoresist
Kui Zhang, Zhengwei Wang, Guodong Chen, Yang Wang, Aijun Zeng, Jing Zhu, Syarhei Avakaw, and Heorgi Tsikhanchuk
A Te-free binary phase change material SbBi is proposed as a new inorganic photoresist for heat-mode lithography. It shows good film-forming ability (surface roughness <1 nm), low threshold power for crystallization (2 mW), and high etching selectivity (15:1). Line-type, dot-type, and complex pattern structures with the smallest feature size of 275 nm are fabricated on SbBi thin films using a 405 nm diode laser direct writing system. In addition, the excellent grating structures with a period of 0.8 μm demonstrate that thermal interference does not affect the adjacent microstructures obviously. These results indicate that SbBi is a promising laser heat-mode resist material for micro/nanostructure fabrication. A Te-free binary phase change material SbBi is proposed as a new inorganic photoresist for heat-mode lithography. It shows good film-forming ability (surface roughness <1 nm), low threshold power for crystallization (2 mW), and high etching selectivity (15:1). Line-type, dot-type, and complex pattern structures with the smallest feature size of 275 nm are fabricated on SbBi thin films using a 405 nm diode laser direct writing system. In addition, the excellent grating structures with a period of 0.8 μm demonstrate that thermal interference does not affect the adjacent microstructures obviously. These results indicate that SbBi is a promising laser heat-mode resist material for micro/nanostructure fabrication.
Chinese Optics Letters
- Publication Date: Sep. 10, 2019
- Vol. 17, Issue 9, 093102 (2019)
A reflecting-type highly efficient terahertz cross-polarization converter based on metamaterials
Xiaoqing Luo, Zhiyong Tan, Chang Wang, and Juncheng Cao
We propose and experimentally demonstrate a wideband linear polarization converter in a reflection mode operating from 2.4 to 4.2 THz with conversion efficiency of more than 80%. Our device can expand the applications to a higher frequency band. A numerical simulation is performed for this metamaterial converter, which shows a good agreement with experimental results. Importantly, a concise and intuitive calculating model is proposed for the Fabry–Pérot cavity. The theoretical results indicate that the underlying reason for the enhanced polarization conversion is the additional phase difference induced by the resonance of the meta-structure and multiple reflections within the Fabry–Pérot cavity. We propose and experimentally demonstrate a wideband linear polarization converter in a reflection mode operating from 2.4 to 4.2 THz with conversion efficiency of more than 80%. Our device can expand the applications to a higher frequency band. A numerical simulation is performed for this metamaterial converter, which shows a good agreement with experimental results. Importantly, a concise and intuitive calculating model is proposed for the Fabry–Pérot cavity. The theoretical results indicate that the underlying reason for the enhanced polarization conversion is the additional phase difference induced by the resonance of the meta-structure and multiple reflections within the Fabry–Pérot cavity.
Chinese Optics Letters
- Publication Date: Sep. 10, 2019
- Vol. 17, Issue 9, 093101 (2019)
An ORMOSIL porous double-layer broadband antireflective coating
Huai Xiong, Yongxing Tang, Lili Hu, and Haiyuan Li
A λ/4–λ/4 broadband antireflective (AR) coating is developed with a sol-gel dip-coating method. By adding SAR-5 organosilicon resin into a base-catalyzed silica sol top layer and treating at 300°C, a broadband AR coating used for blast shields with a high average transmission of 99.34% (450–950 nm) and good hydrophobicity (with a water-contact angle of 119°) was obtained. After being subjected to rubbing 50 times and being maintained at a relative humidity of around 95% for 50 days, the average transmission of the coating decreased by 0.29% and 0.04%, respectively. This indicates that the organically modified silica (ORMOSIL) broadband AR coating has good abrasion resistance and humidity stability. A λ/4–λ/4 broadband antireflective (AR) coating is developed with a sol-gel dip-coating method. By adding SAR-5 organosilicon resin into a base-catalyzed silica sol top layer and treating at 300°C, a broadband AR coating used for blast shields with a high average transmission of 99.34% (450–950 nm) and good hydrophobicity (with a water-contact angle of 119°) was obtained. After being subjected to rubbing 50 times and being maintained at a relative humidity of around 95% for 50 days, the average transmission of the coating decreased by 0.29% and 0.04%, respectively. This indicates that the organically modified silica (ORMOSIL) broadband AR coating has good abrasion resistance and humidity stability.
Chinese Optics Letters
- Publication Date: Mar. 10, 2019
- Vol. 17, Issue 3, 033101 (2019)
Effect of annealing on the damage threshold and optical properties of HfO2/Ta2O5/SiO2 high-reflection film
Jianing Dong, Jie Fan, Sida Mao, Yunping Lan, Yonggang Zou, Haizhu Wang, Jiabin Zhang, and Xiaohui Ma
The effect of thermal annealing on the optical properties, microstructure, and laser-induced damage threshold (LIDT) of HfO2/Ta2O5/SiO2 HR films has been investigated. The transmission spectra shift to a short wavelength and the X-ray diffraction peaks of monoclinic structure HfO2 are enhanced after thermal annealing. The calculated results of the m( 111) diffraction peak show that the HfO2 grain size is increased, which is conducive to increasing the thermal conductivity. Thermal annealing also reduces the laser absorption of high-reflection films. The improvement of thermal conductivity and the decrease of laser absorption both contribute to the improvement of LIDT. The experimental results show that the highest LIDT of 22.4 J/cm2 is obtained at 300°C annealing temperature. With the further increase of annealing temperature, the damage changes from thermal stress damage to thermal explosion damage, resulting in the decrease of LIDT. The effect of thermal annealing on the optical properties, microstructure, and laser-induced damage threshold (LIDT) of HfO2/Ta2O5/SiO2 HR films has been investigated. The transmission spectra shift to a short wavelength and the X-ray diffraction peaks of monoclinic structure HfO2 are enhanced after thermal annealing. The calculated results of the m( 111) diffraction peak show that the HfO2 grain size is increased, which is conducive to increasing the thermal conductivity. Thermal annealing also reduces the laser absorption of high-reflection films. The improvement of thermal conductivity and the decrease of laser absorption both contribute to the improvement of LIDT. The experimental results show that the highest LIDT of 22.4 J/cm2 is obtained at 300°C annealing temperature. With the further increase of annealing temperature, the damage changes from thermal stress damage to thermal explosion damage, resulting in the decrease of LIDT.
Chinese Optics Letters
- Publication Date: Nov. 10, 2019
- Vol. 17, Issue 11, 113101 (2019)
Simultaneous measurements of s - and p -polarization reflectivity with a cavity ring-down technique employing no polarization optics
Hao Cui, Bincheng Li, Yanling Han, Jing Wang, Chunming Gao, and Yafei Wang
The cavity ring-down (CRD) technique is adopted for simultaneously measuring s- and p-polarization reflectivity of highly reflective coatings without employing any polarization optics. As the s- and p-polarized light trapped in the ring-down cavity decay independently, with a randomly polarized light source the ring-down signal recorded by a photodetector presents a double-exponential waveform consisting of ring-down signals of both s- and p-polarized light. The s- and p-polarization reflectivity values of a test mirror are therefore simultaneously determined by fitting the recorded ring-down signal with a double-exponential function. The determined s- and p-polarization reflectivity of 30° and 45° angle of incidence mirrors are in good agreement with the reflectivity values measured with the conventional CRD technique employing a polarizer for polarization control. The cavity ring-down (CRD) technique is adopted for simultaneously measuring s- and p-polarization reflectivity of highly reflective coatings without employing any polarization optics. As the s- and p-polarized light trapped in the ring-down cavity decay independently, with a randomly polarized light source the ring-down signal recorded by a photodetector presents a double-exponential waveform consisting of ring-down signals of both s- and p-polarized light. The s- and p-polarization reflectivity values of a test mirror are therefore simultaneously determined by fitting the recorded ring-down signal with a double-exponential function. The determined s- and p-polarization reflectivity of 30° and 45° angle of incidence mirrors are in good agreement with the reflectivity values measured with the conventional CRD technique employing a polarizer for polarization control.
Chinese Optics Letters
- Publication Date: May. 10, 2017
- Vol. 15, Issue 5, 053101 (2017)
Temperature coefficient of the refractive index for PbTe film
Lingmao Xu, Hui Zhou, Yanchun He, Kaifeng Zhang, Shenghu Wu, and Yuqing Xiong
Specimens of PbTe single film are deposited on Ge substrates by vacuum thermal evaporation. During the temperature range of 80–300 K, the transmittance of a PbTe film within 2–15 μm is measured every 20 K by the PerkinElmer Fourier transform infrared spectroscopy cryogenic testing system. Then, the relationship between the refractive index and wavelength within 7–12 μm at different temperatures is received by the full spectrum inversion method fitting. It can be seen that the relationship conforms to the Cauchy formula, which can be fitted. Then, the relationship between the refractive index of the PbTe film and the temperature/wavelength can be expressed as n(λ,T)=5.82840 0.00304T+4.61458×10 6T2+8.00280/λ2+0.21544/λ4, which is obtained by the fitting method based on the Cauchy formula. Finally, the designed value obtained by the formula and the measured spectrum are compared to verify the accuracy of the formula. Specimens of PbTe single film are deposited on Ge substrates by vacuum thermal evaporation. During the temperature range of 80–300 K, the transmittance of a PbTe film within 2–15 μm is measured every 20 K by the PerkinElmer Fourier transform infrared spectroscopy cryogenic testing system. Then, the relationship between the refractive index and wavelength within 7–12 μm at different temperatures is received by the full spectrum inversion method fitting. It can be seen that the relationship conforms to the Cauchy formula, which can be fitted. Then, the relationship between the refractive index of the PbTe film and the temperature/wavelength can be expressed as n(λ,T)=5.82840 0.00304T+4.61458×10 6T2+8.00280/λ2+0.21544/λ4, which is obtained by the fitting method based on the Cauchy formula. Finally, the designed value obtained by the formula and the measured spectrum are compared to verify the accuracy of the formula.
Chinese Optics Letters
- Publication Date: Apr. 10, 2017
- Vol. 15, Issue 4, 043101 (2017)
Optical property of an antireflection coating fabricated by an optimal spin-coating method with a pH-modified SiO2 nanoparticle solution
Chyan-Chyi Wu, Cheng-Chih Hsu, Yu-Chian Lin, Chia-Wei Chiang, and Ching-Lian Dai
An antireflection (AR) coating is fabricated by applying an optimal spin-coating method and a pH-modified SiO2 nanoparticle solution on a cover glass. Because the pH value of the solution will affect the aggregation and dispersion of the SiO2 particles, the transmittance of the AR-treated cover glass will be enhanced under optimal fabricated conditions. The experimental results show that an AR coating fabricated by an SiO2 nanoparticle solution of pH 11 enhances the transmittance approximately by 3% and 5% under normal and oblique incident conditions, respectively. Furthermore, the AR-treated cover glass exhibits hydrophobicity and shows a 65% enhancement at a contact angle to bare glass. An antireflection (AR) coating is fabricated by applying an optimal spin-coating method and a pH-modified SiO2 nanoparticle solution on a cover glass. Because the pH value of the solution will affect the aggregation and dispersion of the SiO2 particles, the transmittance of the AR-treated cover glass will be enhanced under optimal fabricated conditions. The experimental results show that an AR coating fabricated by an SiO2 nanoparticle solution of pH 11 enhances the transmittance approximately by 3% and 5% under normal and oblique incident conditions, respectively. Furthermore, the AR-treated cover glass exhibits hydrophobicity and shows a 65% enhancement at a contact angle to bare glass.
Chinese Optics Letters
- Publication Date: Feb. 10, 2017
- Vol. 15, Issue 2, 023101 (2017)
Fabrication of multi-wavelength visible and infrared filter for solar atmosphere tomographic imaging
Mingdong Kong, Chun Guo, Bincheng Li, Wenyan He, and Ming Wei
To simultaneously obtain high-resolution multi-wavelength (from visible to near infrared) tomographic images of the solar atmosphere, a high-performance multi-wavelength optical filter has to be used in solar imaging telescopes. In this Letter, the fabrication of the multi-wavelength filter for solar tomographic imaging is described in detail. For this filter, Ta2O5 and SiO2 are used as high- and low-index materials, respectively, and the multilayer structure is optimized by commercial Optilayer software at a 7.5° angle of incidence. Experimentally, this multi-wavelength optical filter is prepared by a plasma ion-assisted deposition technique with optimized deposition parameters. High transmittance at 393.3, 396.8, 430.5, 525, 532.4, 656.8, 705.8, 854.2, 1083, and 1565.3 nm, as well as high reflectance at 500 and 589 nm are achieved. Excellent environmental durability, demonstrated via temperature and humidity tests, is also established. To simultaneously obtain high-resolution multi-wavelength (from visible to near infrared) tomographic images of the solar atmosphere, a high-performance multi-wavelength optical filter has to be used in solar imaging telescopes. In this Letter, the fabrication of the multi-wavelength filter for solar tomographic imaging is described in detail. For this filter, Ta2O5 and SiO2 are used as high- and low-index materials, respectively, and the multilayer structure is optimized by commercial Optilayer software at a 7.5° angle of incidence. Experimentally, this multi-wavelength optical filter is prepared by a plasma ion-assisted deposition technique with optimized deposition parameters. High transmittance at 393.3, 396.8, 430.5, 525, 532.4, 656.8, 705.8, 854.2, 1083, and 1565.3 nm, as well as high reflectance at 500 and 589 nm are achieved. Excellent environmental durability, demonstrated via temperature and humidity tests, is also established.
Chinese Optics Letters
- Publication Date: Dec. 10, 2017
- Vol. 15, Issue 12, 123101 (2017)
Optimization of the spectral performance of an antireflection coating on a micro-spherical substrate
Chun Guo, Mingdong Kong, and Wenyan He
To improve the optical performance of an antireflection (AR) coating on a micro-spherical substrate, the ray angle of the incidence distribution and the thickness profile are taken into consideration during the optical coating design. For a convex spherical substrate with a radius of curvature of 10 mm and a clear aperture of 10 mm, three strategies are used for the optimization of the spectral performance of a broadband AR coating in the spectral region from 480 to 720 nm. By comparing the calculated residual reflectance and spectral uniformity, the developed method demonstrates its superiority in spectral performance optimization of an AR coating on a micro-spherical substrate. To improve the optical performance of an antireflection (AR) coating on a micro-spherical substrate, the ray angle of the incidence distribution and the thickness profile are taken into consideration during the optical coating design. For a convex spherical substrate with a radius of curvature of 10 mm and a clear aperture of 10 mm, three strategies are used for the optimization of the spectral performance of a broadband AR coating in the spectral region from 480 to 720 nm. By comparing the calculated residual reflectance and spectral uniformity, the developed method demonstrates its superiority in spectral performance optimization of an AR coating on a micro-spherical substrate.
Chinese Optics Letters
- Publication Date: Sep. 10, 2016
- Vol. 14, Issue 9, 093101 (2016)
Design of Pd/B4C aperiodic multilayers for 8–12 nm region with flat reflectivity profile
Yiwen Wang, Qiushi Huang, Qiang Yi, Li Jiang, Zhong Zhang, and Zhanshan Wang
The Pd/B4C multilayer is a promising candidate for high reflectance mirrors operating in the 8–12 nm extreme ultraviolet wavelength region. To extend the working bandwidth beyond the L-edge of silcon, we theoretically design broadband Pd/B4C multilayers. We discuss the influence of the desired reflectance of the plateau, number of bilayers, and the real structural parameters, including the interface widths, layer density, and thickness deviation, on the reflectivity profile. Assuming the interface width to be 0.6 nm, we design aperiodic multilayers for broad wavebands of 9.0–10.0, 8.5–10.5, and 8.0–11.0 nm, with average reflectivities of 3.1%, 5.0%, and 9.5%, respectively. The Pd/B4C multilayer is a promising candidate for high reflectance mirrors operating in the 8–12 nm extreme ultraviolet wavelength region. To extend the working bandwidth beyond the L-edge of silcon, we theoretically design broadband Pd/B4C multilayers. We discuss the influence of the desired reflectance of the plateau, number of bilayers, and the real structural parameters, including the interface widths, layer density, and thickness deviation, on the reflectivity profile. Assuming the interface width to be 0.6 nm, we design aperiodic multilayers for broad wavebands of 9.0–10.0, 8.5–10.5, and 8.0–11.0 nm, with average reflectivities of 3.1%, 5.0%, and 9.5%, respectively.
Chinese Optics Letters
- Publication Date: Jul. 10, 2016
- Vol. 14, Issue 7, 073101 (2016)
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