Realization of high-quality optical nanoporous gradient-index filters by optimal combination of anodization conditions

Abstract

High-quality nanoporous anodic alumina gradient-index filters are realized by sinusoidal pulse anodization under optimized anodization conditions.

Enhancing Forbidden Light Propagation in Nanoporous Anodic Alumina Gradient-Index Filters by Alcohol Additives

“…The characteristic PSB of NAA-GIFs is the optical feature that determines the quality of forbidden light propagation across these NAA-PCs. Assessment of the features of NAA-GIFs’ PSB (i.e., λ PSB , FWHM PSB , I PSB , and Q PSB ) produced with varying type and concentration of alcohol additive (i.e., MetOH, EtOH, IPA, and EGOH, from 10 to 70 vol % with Δ­[alcohol] = 10 vol %) can serve as an indicator to characterize the impact of electrochemical conditions on the structural and optical properties of these model NAA-PCs . Therefore, key optical parameters were quantified from Gaussian fittings applied to the PSB in the optical transmission spectra of NAA-GIFs (Figures S8–S11Supporting Information).…”

“…NAA-GIFs are a class of NAA-PCs with smooth, periodic modulation of refractive index, which is optically translated into a characteristically well-resolved and narrow PSB. The narrow linewidth of NAA-GIFs’ PSB with suppressed higher-order harmonics and sidelobes makes them suitable components for various high-precision light-filtering applications. , This optical feature also provides NAA-GIFs with high sensitivity and responsiveness to changes in their effective medium, making them ideal optical transducers for sensing and biosensing technologies. − To date, various sinusoidal pulse anodization strategies under mild conditions have been devised to achieve high-quality control of light in NAA-GIFs, including apodization of anodization profiles, implementation of voltage-period compensation modes, − and optimization of anodization conditions. − Despite these advances, fabrication of high-quality NAA-PCs by mild pulse anodization remains challenging. NAA-PCs suffer from two main intrinsic constraints: (i) a low refractive index contrast air–alumina ( n air ∼ 1.0 RIU and n alumina ∼ 1.5–2.3 RIU) and (ii) progressive chemical etching of NAA during anodization, which leads to an unbalanced distribution of optical thickness (OT) along NAA stacks comprising the structure of NAA-PCs.…”

Recent Advances in Nanoporous Anodic Alumina: Principles, Engineering, and Applications

“…To provide overview of many functionalities discussed in Sections 4.1-4.7, they are gathered in the Table 2. [190] Gradient-index filters [191] Distributed Bragg reflectors [192] Optical bandpass filters [193] Human protein heavy ions real-time interaction monitoring [194] Tailoring of optical properties with pulse anodization [149] Design of phase shift defect in effective refractive index [195] Hybrid distributed DBRs and apodized GIF photonic structure [196] Characterization of thermotropic ferroelectric liquid crystals confined in the NAA [197][198][199] Glass transition of discotic liquid crystals in one-dimensional fluid [200] Adjustable optical anisotropy by self-assembly of liquid crystals confined in porous structure [201] Sensors NAA template-assisted fabrication of chromium substrate for SERS detection of heavy ions in aqueous solutions [202] Au NPs array on NAA for SERS detection of hemoglobin [203] Controlled fabrication of periodic plasmonic dimer arrays for SERS [204] Graphene-NAA composite for SERS sensing [205] Label-free optical sensor based on interferometric reflectance spectroscopy for TNF-α detection [206] NAA-based interferometer for copper sensing [207] In vivo nanotubes nanotoxicity study on murine model […”

“…Propagation of light can be adjusted through a change in the geometry. The most common PC structures made this way are Fabry-Perót interferometers [190], gradient-index filters [191], distributed Bragg reflectors [192], and optical bandpass filters [193]. Their major utilization is as optical sensors.…”

Advances in Optical Biosensors and Sensors Using Nanoporous Anodic Alumina

“…Self-ordered porous metal oxides (SOPMOs) are three-dimensional nanostructure platforms that are made with an electrochemical anodization method, such as tantalum [ 4 , 5 , 6 , 7 , 8 , 9 ], titanium [ 10 , 11 , 12 , 13 ], niobium [ 14 , 15 , 16 , 17 ], iron [ 18 , 19 , 20 ], stainless steel [ 21 , 22 , 23 ], silicon [ 24 , 25 , 26 , 27 ], aluminium [ 28 , 29 , 30 , 31 ], in acidic solutions. Among them, the self-ordered nanoporous aluminium oxide called nanoporous anodic alumina (NAA) has many advantages such as a durable platform, easy functional ability, high surface area, biocompatibility, and low-cost [ 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 ].…”