Tunable Nanoporous Anodic Alumina Photonic Crystals by Gaussian Pulse Anodization

Abstract

This study presents a Gaussian pulse anodization approach to generate nanoporous photonic crystals with highly tunable and controllable optical properties across the visible−NIR spectrum. Nanoporous anodic alumina Gaussian photonic crystals (NAA-GPCs) are fabricated in oxalic acid electrolyte by Gaussian pulse anodization, a novel form of pulse-like anodization. The effect of the Gaussian pulse width in the anodization profile on the optical properties of these photonic crystals is assessed by systematically varying this fabrication parameter from 5 to 60 s. The optical features of the characteristic photonic stopband (PSB) of NAA-GPCsthe position of the central wavelength, full width at halfmaximum, and intensityare found to be highly dependent on the Gaussian pulse width, the angle of incidence of incoming photons, and the nanopore diameter of NAA-GPCs. The effective medium of NAA-GPCs is assessed by monitoring spectral shifts in their characteristic PSB upon infiltration of their nanoporous structure with analytical solutions of D-glucose of varying concentration (0.0125−1 M). Experimental results are validated and mechanistically described by theoretical simulations, using the Looyenga− Landau−Lifshitz effective medium approximation model. Our findings demonstrate that Gaussian pulse anodization is an effective nanofabrication approach to producing highly sensitive NAA-based PC structures with versatile and tunable PSBs across the spectral regions. The findings provide new exiting opportunities to integrate these unique PC structures into photonic sensors and other platform materials for light-based technologies.

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

“…Infiltration of D-glucose into the pores results in a spectral shift of PSBs and the possibility of a quan-titative detection based on the shift. In other work, Gaussian pulse anodization with different time gaps between the pulses has been examined [149]. The PSB optical features of the structure such as the position of the central wavelength, the width at half-maximum, and the intensity could be adjusted by altering the time gaps-with the incidence angle of photons and the porosity of the structure being relevant as well.…”

“…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 […”

“…The precise control of the optical properties across the visible-NIR spectrum with pulse-anodized oxalic-fabricated NAA was demonstrated by Acosta et al [149]. In addition, there are other types of structures as well.…”

Charge Density-Versus Time-Controlled Pulse Anodization in the Production of PAA-Based DBRs for MIR Spectral Region

“…The thickness of layers can be controlled by the duration of the U L and U H pulses. The refractive index profile in PAA-based PCs follows the shift of voltage (or current density) pulse profiles such as sinusoidal [16], pseudo-sinusoidal [13], sawtooth [17] or Gaussian [18]. The precise tailoring of the refractive index and thickness of porous layers allows to design photonic stop-band (PSB) across the spectral regions from ultraviolet to infrared wavelengths [19].…”

Real-Time Monitoring of Doxorubicin Release from Hybrid Nanoporous Anodic Alumina Structures

“…The optical properties of NAA can be modulated by varying its refractive index in several ways to obtain advanced structures capable of undergoing optical phenomenon’s (absorption, reflection, emission, and transmission). Numerous anodization strategies such as sinusoidal [ 19 ], saw-tooth [ 20 ], step-wise [ 4 ], and gaussian [ 21 ] have been performed in the past, leading to the generation of advanced photonic structures such as microcavities [ 4 ], gradient-index filters (GIFs) [ 2 , 22 ], distributed Bragg reflectors [ 23 ], and bandpass filters [ 24 ], etc. Amongst the structures mentioned above, GIFs display a unique class of photonic structures wherein the periodic variation of the effective refractive index occurs due to the sinusoidal anodization process.…”