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Formation of broadband antireflective and superhydrophilic subwavelength structures on fused silica using one-step self-masking reactive ion etching.

Ye X, Jiang X, Huang J, Geng F, Sun L, Zu X, Wu W, Zheng W - Sci Rep (2015)

Bottom Line: The measured antireflection properties are consistent with the results of theoretical analysis using a finite-difference time-domain (FDTD) method.This method is also applicable to diffraction grating fabrication.Moreover, the surface of the subwavelength structures exhibits significant superhydrophilic properties.

View Article: PubMed Central - PubMed

Affiliation: Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang, 621900 (P.R. China).

ABSTRACT
Fused silica subwavelength structures (SWSs) with an average period of ~100 nm were fabricated using an efficient approach based on one-step self-masking reactive ion etching. The subwavelength structures exhibited excellent broadband antireflection properties from the ultraviolet to near-infrared wavelength range. These properties are attributable to the graded refractive index for the transition from air to the fused silica substrate that is produced by the ideal nanocone subwavelength structures. The transmittance in the 400-700 nm range increased from approximately 93% for the polished fused silica to greater than 99% for the subwavelength structure layer on fused silica. Achieving broadband antireflection in the visible and near-infrared wavelength range by appropriate matching of the SWS heights on the front and back sides of the fused silica is a novel strategy. The measured antireflection properties are consistent with the results of theoretical analysis using a finite-difference time-domain (FDTD) method. This method is also applicable to diffraction grating fabrication. Moreover, the surface of the subwavelength structures exhibits significant superhydrophilic properties.

No MeSH data available.


Related in: MedlinePlus

(A) Transmittance of the fused silica double-sided SWS and the bare fused silica. (B) Reflectance of the fused silica double-sided SWS and the bare fused silica. (C) The sum of the measured transmittance and reflectance of the fused silica double-sided SWS. (D) The angle-dependent transmission spectra for the SWS and bare fused silica at 15°, 30° and 45°. Note the OH− absorption at approximately 1380 nm and the detector change at approximately 860 nm. (E) Photograph of the SWS under sun light illumination. The boundary between the coated (bottom of the substrate) and uncoated (top of the substrate) area of the SWS is indicated by the blue arrow. (F) Photograph of a fluorescent light reflected on the SWS surface that was fabricated on one half of the fused silica substrate. Figures (E,F) were obtained by X. Ye and L. Sun.
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f4: (A) Transmittance of the fused silica double-sided SWS and the bare fused silica. (B) Reflectance of the fused silica double-sided SWS and the bare fused silica. (C) The sum of the measured transmittance and reflectance of the fused silica double-sided SWS. (D) The angle-dependent transmission spectra for the SWS and bare fused silica at 15°, 30° and 45°. Note the OH− absorption at approximately 1380 nm and the detector change at approximately 860 nm. (E) Photograph of the SWS under sun light illumination. The boundary between the coated (bottom of the substrate) and uncoated (top of the substrate) area of the SWS is indicated by the blue arrow. (F) Photograph of a fluorescent light reflected on the SWS surface that was fabricated on one half of the fused silica substrate. Figures (E,F) were obtained by X. Ye and L. Sun.

Mentions: Using the RIE procedure described above, a double-sided SWS was fabricated using the S3 condition from the broadband AR performance study. In the double-sided SWS, the morphologies of the two sides were nearly identical because the fabrication process was identical for both sides (Supplementary Information Figure S2). Figure 4(A) presents the optical transmission spectra of the fused silica with the double-sided SWS (red line) and the bare fused silica (black line) with a normal incident source. The transmittance of the SWS sample was significantly improved for a wide range of wavelengths (300–1400 nm) compared with the bare fused silica. The maximum transmittance of the double-sided surfaces of the SWS at 500 nm was approximately 99.5%, ~6% higher than the transmittance of the bare fused silica. Moreover, the double-sided surfaces of the SWS exhibited transmittance of greater than 99% for the 400–700 nm wavelength range. The hemispherical total reflectance (diffuse + specular) as a function of wavelength for the fused silica with the double-sided SWS (black line) and without the SWS (red line) using the integrating sphere is presented in Fig. 4B. The average hemispherical total reflectance decreased to <1% for the 300–700 nm wavelength range, with an average hemispherical total reflectance of <0.5% for the 410–550 nm wavelength range. The specular and diffused scattering components are presented in Figure S3 (A). As shown in Fig. 4(C), the sum of the transmittance and reflectance was less than 100% in the short wavelength region for the fused silica SWS and approximately 100% at all measured wavelengths for the bare fused silica substrate. This observation will be discussed later. The angle-dependent transmittance of the surfaces of the SWS was evaluated at different incident angles from 15° to 45°. As shown in Fig. 4(D), the fused silica SWS had a nearly constant average transmittance of approximately 99% for an incidence angle up to 30°. The maximum transmittance of the double-sided surfaces of the SWS was approximately 98.4% for an incidence angle up to 45°. However, the transmittance of the fused silica with the double-sided SWS was less dependent on the incidence angle of light than was the bare fused silica substrate. The fused silica with the double-sided SWS exhibited a ~1% decrease in the transmittance value for incidence angles of 0° to 45°, a smaller decrease than that observed for the bare fused silica (>2%). This difference occurs because the effective refractive index profile from air to the fused silica substrate changes slowly with an increase in the incidence angles. As indicated by the black line in Fig. 4D, all the transmittance data for the double-sided SWS were larger than those of the bare fused silica substrate, confirming the excellent large field of view AR characteristics of the double-sided SWS.


Formation of broadband antireflective and superhydrophilic subwavelength structures on fused silica using one-step self-masking reactive ion etching.

Ye X, Jiang X, Huang J, Geng F, Sun L, Zu X, Wu W, Zheng W - Sci Rep (2015)

(A) Transmittance of the fused silica double-sided SWS and the bare fused silica. (B) Reflectance of the fused silica double-sided SWS and the bare fused silica. (C) The sum of the measured transmittance and reflectance of the fused silica double-sided SWS. (D) The angle-dependent transmission spectra for the SWS and bare fused silica at 15°, 30° and 45°. Note the OH− absorption at approximately 1380 nm and the detector change at approximately 860 nm. (E) Photograph of the SWS under sun light illumination. The boundary between the coated (bottom of the substrate) and uncoated (top of the substrate) area of the SWS is indicated by the blue arrow. (F) Photograph of a fluorescent light reflected on the SWS surface that was fabricated on one half of the fused silica substrate. Figures (E,F) were obtained by X. Ye and L. Sun.
© Copyright Policy - open-access
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4542686&req=5

f4: (A) Transmittance of the fused silica double-sided SWS and the bare fused silica. (B) Reflectance of the fused silica double-sided SWS and the bare fused silica. (C) The sum of the measured transmittance and reflectance of the fused silica double-sided SWS. (D) The angle-dependent transmission spectra for the SWS and bare fused silica at 15°, 30° and 45°. Note the OH− absorption at approximately 1380 nm and the detector change at approximately 860 nm. (E) Photograph of the SWS under sun light illumination. The boundary between the coated (bottom of the substrate) and uncoated (top of the substrate) area of the SWS is indicated by the blue arrow. (F) Photograph of a fluorescent light reflected on the SWS surface that was fabricated on one half of the fused silica substrate. Figures (E,F) were obtained by X. Ye and L. Sun.
Mentions: Using the RIE procedure described above, a double-sided SWS was fabricated using the S3 condition from the broadband AR performance study. In the double-sided SWS, the morphologies of the two sides were nearly identical because the fabrication process was identical for both sides (Supplementary Information Figure S2). Figure 4(A) presents the optical transmission spectra of the fused silica with the double-sided SWS (red line) and the bare fused silica (black line) with a normal incident source. The transmittance of the SWS sample was significantly improved for a wide range of wavelengths (300–1400 nm) compared with the bare fused silica. The maximum transmittance of the double-sided surfaces of the SWS at 500 nm was approximately 99.5%, ~6% higher than the transmittance of the bare fused silica. Moreover, the double-sided surfaces of the SWS exhibited transmittance of greater than 99% for the 400–700 nm wavelength range. The hemispherical total reflectance (diffuse + specular) as a function of wavelength for the fused silica with the double-sided SWS (black line) and without the SWS (red line) using the integrating sphere is presented in Fig. 4B. The average hemispherical total reflectance decreased to <1% for the 300–700 nm wavelength range, with an average hemispherical total reflectance of <0.5% for the 410–550 nm wavelength range. The specular and diffused scattering components are presented in Figure S3 (A). As shown in Fig. 4(C), the sum of the transmittance and reflectance was less than 100% in the short wavelength region for the fused silica SWS and approximately 100% at all measured wavelengths for the bare fused silica substrate. This observation will be discussed later. The angle-dependent transmittance of the surfaces of the SWS was evaluated at different incident angles from 15° to 45°. As shown in Fig. 4(D), the fused silica SWS had a nearly constant average transmittance of approximately 99% for an incidence angle up to 30°. The maximum transmittance of the double-sided surfaces of the SWS was approximately 98.4% for an incidence angle up to 45°. However, the transmittance of the fused silica with the double-sided SWS was less dependent on the incidence angle of light than was the bare fused silica substrate. The fused silica with the double-sided SWS exhibited a ~1% decrease in the transmittance value for incidence angles of 0° to 45°, a smaller decrease than that observed for the bare fused silica (>2%). This difference occurs because the effective refractive index profile from air to the fused silica substrate changes slowly with an increase in the incidence angles. As indicated by the black line in Fig. 4D, all the transmittance data for the double-sided SWS were larger than those of the bare fused silica substrate, confirming the excellent large field of view AR characteristics of the double-sided SWS.

Bottom Line: The measured antireflection properties are consistent with the results of theoretical analysis using a finite-difference time-domain (FDTD) method.This method is also applicable to diffraction grating fabrication.Moreover, the surface of the subwavelength structures exhibits significant superhydrophilic properties.

View Article: PubMed Central - PubMed

Affiliation: Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang, 621900 (P.R. China).

ABSTRACT
Fused silica subwavelength structures (SWSs) with an average period of ~100 nm were fabricated using an efficient approach based on one-step self-masking reactive ion etching. The subwavelength structures exhibited excellent broadband antireflection properties from the ultraviolet to near-infrared wavelength range. These properties are attributable to the graded refractive index for the transition from air to the fused silica substrate that is produced by the ideal nanocone subwavelength structures. The transmittance in the 400-700 nm range increased from approximately 93% for the polished fused silica to greater than 99% for the subwavelength structure layer on fused silica. Achieving broadband antireflection in the visible and near-infrared wavelength range by appropriate matching of the SWS heights on the front and back sides of the fused silica is a novel strategy. The measured antireflection properties are consistent with the results of theoretical analysis using a finite-difference time-domain (FDTD) method. This method is also applicable to diffraction grating fabrication. Moreover, the surface of the subwavelength structures exhibits significant superhydrophilic properties.

No MeSH data available.


Related in: MedlinePlus