1
|
López-Reyes P, Gutiérrez-Luna N, Honrado-Benítez C, Ríos-Fernández Á, Enríquez-Pérez E, Chavero-Royán J, Espinosa-Yáñez L, Rodríguez-de Marcos LV, Larruquert JI. Far UV narrowband mirrors tuned at H Lyman α. OPTICS EXPRESS 2023; 31:15392-15408. [PMID: 37157642 DOI: 10.1364/oe.487328] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Imaging at H Ly-α (121.6 nm), among other spectral lines in the short far UV (FUV), is of high interest for astrophysics, solar, and atmosphere physics, since this spectral line is ubiquitously present in space observations. However, the lack of efficient narrowband coatings has mostly prevented such observations. Present and future space observatories like GLIDE and the IR/O/UV NASA concept, among other applications, can benefit from the development of efficient narrowband coatings at Ly-α. The current state of the art of narrowband FUV coatings lacks performance and stability for coatings that peak at wavelengths shorter than ∼135 nm. We report highly reflective AlF3/LaF3 narrowband mirrors at Ly-α prepared by thermal evaporation, with, to our knowledge, the highest reflectance (over 80%) of a narrowband multilayer at such a short wavelength obtained so far. We also report a remarkable reflectance after several months of storage in different environments, including relative humidity levels above 50%. For astrophysics targets in which Ly-α may mask a close spectral line, such as in the search for biomarkers, we present the first coating in the short FUV for imaging at the OI doublet (130.4 and 135.6 nm), with the additional requirement of rejecting the intense Ly-α, which might mask the OI observations. Additionally, we present coatings with the symmetric design, aimed to observe at Ly-α, and reject the strong OI geocoronal emission, that could be of interest for atmosphere observations.
Collapse
|
2
|
Wang X, Zhou P, Ren S, Li X, Wang H, Zheng X, Chen B. Far ultraviolet mirrors for aurora imaging: design and fabrication. APPLIED OPTICS 2023; 62:2629-2635. [PMID: 37132812 DOI: 10.1364/ao.482763] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
The emission lines of 140-180 nm are auroral bands of N 2 Lyman-Birge-Hopfield, and they have been imaging targets of many satellites that need reflective mirrors. To obtain good imaging quality, the mirrors also should have excellent out-of-band reflection suppression as well as high reflectance at working wavelengths. We designed and fabricated non-periodic multilayer L a F 3/M g F 2 mirrors with working wave bands of 140-160 nm and 160-180 nm, respectively. We used a match design method and deep search method to design the multilayer. Our work has been utilized in the new wide-field auroral imager of China, and the application of these notch mirrors with excellent out-of-band suppression reduces the utilization of corresponding transmissive filters in the optical system of space payload. Furthermore, our work provides new routes for the design of other reflective mirrors in the far ultraviolet region.
Collapse
|
3
|
Schmitt P, Stempfhuber S, Felde N, Szeghalmi AV, Kaiser N, Tünnermann A, Schwinde S. Influence of seed layers on the reflectance of sputtered aluminum thin films. OPTICS EXPRESS 2021; 29:19472-19485. [PMID: 34266056 DOI: 10.1364/oe.428343] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/20/2021] [Accepted: 05/18/2021] [Indexed: 06/13/2023]
Abstract
The fabrication of highly reflective aluminum coatings is still an important part of current research due to their high intrinsic reflectivity in a broad spectral range. By using thin seed layers of Cu, CuOx, Cr, CrOx, Au, and Ag, the morphology of sputtered (unprotected) aluminum layers and, consequently, their reflectance can be influenced. In this long-term study, the reflectance behavior was measured continuously using spectrophotometry. Particular seed layer materials enhance the reflectance of aluminum coatings significantly and reduce their long-term degradation. Combining such seed layers with evaporation processes and suitable protective layers could further increase the reflectance of aluminum coatings.
Collapse
|
4
|
Abstract
More efficient and stable far ultraviolet (FUV) mirrors will enable future space observatories. Traditional FUV mirrors are based on MgF2-protected Al. AlF3 has been identified as a promising substitute for MgF2 to prevent Al oxidation. Hence, the reflectivity, stability, and morphology of AlF3-protected Al mirrors have been investigated as a function of deposition temperature of the AlF3 film. In this work, it is shown how AlF3 deposition temperature is an important parameter whose optimization ultimately yields valuable throughput enhancement and improved endurance to large storage periods. Al films were deposited at room temperature (RT) and AlF3 protective layers were deposited at temperatures ranging from RT to 350 °C. It was found that the optimum AlF3 deposition temperature was between 200 and 250 °C, yielding the largest FUV reflectance and a better stability of the mirrors, which had been stored in a desiccator environment. Increasing AlF3 deposition temperature resulted in an increase in film density, approaching bulk density at 250 °C. The morphology of Al and AlF3 films as a function of AlF3 deposition temperature was also investigated. The increase in the AlF3 deposition temperature resulted in a decrease of both Al and AlF3 surface roughness and in the growth of the grain width at the AlF3 outer surface. It also resulted in a trend for the prevalent (111) planes of Al nanocrystals to orient parallel to the coating surface.
Collapse
|
5
|
De Marcos LVR, Larruquert JI, Méndez JA, Gutiérrez-Luna N, Espinosa-Yáñez L, Honrado-Benítez C, Chavero-Royán J, Perea-Abarca B. Optimization of MgF 2-deposition temperature for far UV Al mirrors. OPTICS EXPRESS 2018; 26:9363-9372. [PMID: 29715889 DOI: 10.1364/oe.26.009363] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2018] [Accepted: 03/21/2018] [Indexed: 06/08/2023]
Abstract
Progress towards far UV (FUV) coatings with enhanced reflectance is invaluable for future space missions, such as LUVOIR. This research starts with the procedure developed to enhance MgF2-protected Al reflectance through depositing MgF2 on a heated aluminized substrate [Quijada et al., Proc. SPIE 8450, 84502H (2012)] and it establishes the optimum deposition temperature of the MgF2 protective film for Al mirrors with a reflectance as high as ~90% at 121.6 nm. Al films were deposited at room temperature and protected with a MgF2 film deposited at various temperatures ranging from room temperature to 350°C. It has been found that mirror reflectance in the short FUV range continuously increases with MgF2 deposition temperature up to 250°C, whereas reflectance decreases at temperatures of 300°C and up. The short-FUV reflectance of mirrors deposited at 250°C only slightly decreased over time by less than 1%, compared to a larger decay for standard coatings prepared at room temperature. Al mirrors protected with MgF2 deposited at room temperature that were later annealed displayed a similar reflectance enhancement that mirrors protected at high temperatures. MgF2 and Al roughness as well as MgF2 density were analyzed by x-ray grazing incidence reflectometry. A noticeable reduction in both Al and MgF2 roughness, as well as an increase of MgF2 density, were measured for films deposited at high temperatures. On the other hand, it was found a strong correlation between the protective-layer deposition temperature (or post-deposition annealing temperature) and the pinhole open area in Al films, which could be prevented with a somewhat thicker Al film.
Collapse
|
6
|
Wilbrandt S, Stenzel O, Nakamura H, Wulff-Molder D, Duparré A, Kaiser N. Protected and enhanced aluminum mirrors for the VUV. APPLIED OPTICS 2014; 53:A125-A130. [PMID: 24514204 DOI: 10.1364/ao.53.00a125] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/22/2013] [Accepted: 10/16/2013] [Indexed: 06/03/2023]
Abstract
Aluminum layers protected with fluoride coatings have been deposited by evaporation and characterized with respect to their suitability as vacuum ultraviolet (VUV) mirrors. Optical characterization has been performed by spectrophotometry, while the surface quality of the layers has been judged by means of x ray reflection, scanning electron microscopy, and atomic force microscopy. In particular, protection with aluminum fluoride results in superior VUV reflection properties. VUV reflectance values between 80% and nearly 90% have been verified even two years after deposition and exposure to the atmosphere.
Collapse
|
7
|
Liu MC, Lee CC, Kaneko M, Nakahira K, Takano Y. Influence of ion assistance on LaF3 films deposited by molybdenum boat evaporation. APPLIED OPTICS 2012; 51:2865-2869. [PMID: 22614587 DOI: 10.1364/ao.51.002865] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/20/2012] [Accepted: 03/14/2012] [Indexed: 06/01/2023]
Abstract
LaF3 thin films at 193 nm were deposited by the molybdenum boat evaporation with ion-assisted deposition (IAD). Various optical characteristics, stress, and microstructures that formed under different ion-beam voltages of IAD deposition were investigated. The relation between these properties is also discussed. LaF3 films deposited with IAD exhibited small rough surfaces and large optical loss at 193 nm. The largest value of optical loss for films at 193 nm, which were prepared at an ion-beam voltage of 400 V, was 1.55% and the extinction coefficient was smaller than 0.0015. Microstructures and crystalline structures of films were influenced and changed by the ion-assisted deposition process. Tensile stress value of films increased as the ion-beam voltage rose. Refractive index, related to the packing density and microstructures, also increased as the ion-beam voltage rose.
Collapse
Affiliation(s)
- Ming-Chung Liu
- Green Energy and Environment Research Laboratories, Industrial Technology Research Institute, Taiwan.
| | | | | | | | | |
Collapse
|
8
|
Lee CC, Liao BH, Liu MC. Developing new manufacturing methods for the improvement of AlF3 thin films. OPTICS EXPRESS 2008; 16:6904-6909. [PMID: 18545394 DOI: 10.1364/oe.16.006904] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
In this research, the plasma etching mechanism which is applied to deposit AlF(3) thin films has been discussed in detail. Different ratios of O(2) gas were injected in the sputtering process and then the optical properties and microstructure of the thin films were examined. The best optical quality and smallest surface roughness was obtained when the AlF(3) thin films were coated with O(2):CF(4) (12 sccm:60 sccm) at 30 W sputtering power. To increase the deposition rate for industrial application, the sputtering power was increased to 200 W with the best ratio of O(2)/CF(4) gas. The results show that the deposition rate at 200W sputtering power was 7.43 times faster than that at 30 W sputtering power and the extinction coefficients deposited at 200 W are less than 6.8 x 10(-4) at the wavelength range from 190 nm to 700 nm. To compare the deposition with only CF(4) gas at 200 W sputtering power, the extinction coefficient of the thin films improve from 4.4 x 10(-3) to 6 x 10(-4) at the wavelength of 193 nm. In addition, the structure of the film deposited at 200W was amorphous-like with a surface roughness of 0.8 nm.
Collapse
Affiliation(s)
- Cheng-Chung Lee
- Department of Optics and Photonics, Thin Film Technology Center, National Central University 320, Taiwan.
| | | | | |
Collapse
|
9
|
Liao BH, Liu MC, Lee CC. Process for deposition of AlF3 thin films. APPLIED OPTICS 2008; 47:C41-C45. [PMID: 18449269 DOI: 10.1364/ao.47.000c41] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
We fabricated aluminum fluoride (AlF(3)) thin films by pulsed DC magnetron sputtering with various CF(4) flow rates and sputtering powers. Our method is distinct from the conventional deposition process in that we used inexpensive Al (99.99% purity) as the target instead of an expensive fluoride compound. The optical properties and microstructure of the thin films were examined. The optical quality of AlF(3) thin films deposited at a 20 W sputtering power and injected 110 SCCM (SCCM denotes cubic centimeters per minute at standard temperature and pressure) CF(4) flow at room temperature showed improvement with an extinction coefficient of less than 7 x 10(-4) at 193 nm. The deposition of AlF(3) thin films at different substrate temperatures and annealed by UV light was also investigated.
Collapse
Affiliation(s)
- Bo-Huei Liao
- Department of Optics and Photonics, Thin Film Technology Center, National Central University, Chung-Li 320, Taiwan
| | | | | |
Collapse
|
10
|
Liu MC, Lee CC, Liao BH, Kaneko M, Nakahira K, Takano Y. Fluoride antireflection coatings deposited at 193 nm. APPLIED OPTICS 2008; 47:C214-C218. [PMID: 18449249 DOI: 10.1364/ao.47.00c214] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Antireflection coatings for 193 nm composed of low-index (MgF(2) and AlF(3)) and high-index (LaF(3) and GdF(3)) materials are deposited by the resistive heating boat method at a substrate temperature of 300 degrees C. The optical characteristics (reflectance and optical loss), microstructure (morphology and surface roughness), stress, and laser-induced damage threshold (LIDT) of the coatings are investigated and discussed. The related reflection at 193 nm of the four kinds of antireflection coatings is smaller than 0.2% and the optical loss is less than 0.15%. Of the fluoride antireflection coatings, AlF(3)/GdF(3) had the lowest stress value. Antireflection coatings with AlF(3) as the low-index material had higher LIDT values than when MgF(2) was used.
Collapse
Affiliation(s)
- Ming-Chung Liu
- Thin Film Technology Center, Department of Optics and Photonics, National Central University, Chung-Li, Taiwan 32001.
| | | | | | | | | | | |
Collapse
|
11
|
Liu MC, Lee CC, Kaneko M, Nakahira K, Takano Y. Microstructure of magnesium fluoride films deposited by boat evaporation at 193 nm. APPLIED OPTICS 2006; 45:7319-24. [PMID: 16983421 DOI: 10.1364/ao.45.007319] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Single layer magnesium fluoride (MgF2) was deposited on fused-silica substrates by a molybdenum boat evaporation process at 193 nm. The formation of various microstructures in relation to the different substrate temperatures and deposition rates were investigated. The relation between these microstructures (including cross-sectional morphology, surface roughness, and crystalline structures), the optical properties (including refractive index and optical loss) and stress, were all investigated. It was found that the laser-induced damage threshold (LIDT) would be affected by the microstructure, optical loss, and stress of the thin film. To obtain a larger LIDT value and better optical characteristics, MgF2 films should be deposited at a high substrate temperature (300 degrees C) and at a low deposition rate (0.05 nm s(-1)).
Collapse
Affiliation(s)
- Ming-Chung Liu
- Thin Film Technology Center, Institute of Optical Sciences, National Central University, Chung-Li, Taiwan.
| | | | | | | | | |
Collapse
|
12
|
Lee CC, Liu MC, Kaneko M, Nakahira K, Takano Y. Influence of thermal annealing and ultraviolet light irradiation on LaF3 thin films at 193 nm. APPLIED OPTICS 2005; 44:6921-6. [PMID: 16294967 DOI: 10.1364/ao.44.006921] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Lanthanum fluoride (LaF3) thin films were prepared by resistive heating evaporation and electron-beam gun evaporation under the same deposition rate, deposition substrate temperature, and vacuum pressure. The coated LaF3 films were then treated by heat annealing and UV light irradiation. The optical properties, microstructures, stress, and laser-induced damage threshold (LIDT) at a wavelength of 193 nm were investigated. The surface roughness, optical loss, stress, and LIDT of the films were improved after the annealing. The films had better properties when irradiated by UV light as compared with heat annealing.
Collapse
Affiliation(s)
- Cheng-Chung Lee
- Thin Film Technology Center, National Central University, Chung-Li 320, Taiwan.
| | | | | | | | | |
Collapse
|
13
|
|
14
|
Zukic M, Torr DG, Spann JF, Torr MR. Vacuum ultraviolet thin films. 1: Optical constants of BaF(2), CaF(2), LaF(3), MgF(2), Al(2)O(3), HfO(2), and SiO(2) thin films. APPLIED OPTICS 1990; 29:4284-4292. [PMID: 20577378 DOI: 10.1364/ao.29.004284] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
The optical constants of MgF(2) (bulk) and BaF(2), CaF(2), LaF(3), MgF(2), Al(2)O(3), HfO(2), and SiO(2) films deposited on MgF(2) substrates are determined from photometric measurements through an iteration process of matching calculated and measured values of the reflectance and transmittance in the 120-230-nm vacuum ultraviolet wavelength region. The potential use of the listed fluorides and oxides as vacuum ultraviolet coating materials is discussed in part 2 of this paper.
Collapse
|
15
|
Martin PJ, Sainty WG, Netterfield RP, McKenzie DR, Cockayne DJ, Sie SH, Wood OR, Craighead HG. Influence of ion assistance on the optical properties of MgF(2). APPLIED OPTICS 1987; 26:1235-1239. [PMID: 20454308 DOI: 10.1364/ao.26.001235] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
The optical properties of MgF(2) films prepared by evaporation and ion-assisted deposition have been determined from transmittance and near-normal incidence reflectance measurements and also from electron-energy loss spectroscopy (EELS). The results show that oxygen-ion assistance leads to higher extinction coefficients for wavelengths <180 nm. Transmission electron microscopy studies show that the crystal grain size of MgF(2) films is not strongly affected by oxygen or argon-ion bombardment. The presence of MgO in the films is inferred from RBS measurements and proposed to be the major factor influencing VUV losses. EELS is also demonstrated to be a valuable technique for determination of optical properties from the near-infrared to x-ray regions of the spectrum.
Collapse
|