Transmission spectra of one-dimensional porous alumina photonic crystals

Law

Lim

et al. 2021

Nanoporous anodic alumina optical microcavities (NAA−μQVs) with spectrally tunable resonance band and surface chemistry are used as model light-confining photonic crystal (PC) platforms to elucidate the combined effect of spectral light confinement features and surface chemistry on optical sensitivity. These model nanoporous PCs show well-resolved, spectrally tunable resonance bands (RBs), the central wavelength of which is engineered from ∼400 to 800 nm by the period of the input anodization profile. The optical sensitivity of the as-produced (hydrophilic) and dichlorodimethylsilane-functionalized (hydrophobic) NAA−μQVs is studied by monitoring dynamic spectral shifts of their RB upon infiltration with organic-and aqueous-based analytical solutions of equally varying refractive index, from 1.333 to 1.345 RIU. Our findings demonstrate that hydrophilic NAA−μQVs show ∼81 and 35% superior sensitivity to their hydrophobic counterparts for organic-and aqueous-based analytical solutions, respectively. Interestingly, the sensitivity of hydrophilic NAA−μQVs per unit of spectral shift is more than 3-fold higher in organic than in aqueous matrices upon equal change of refractive index, with values of 0.347 ± 0.002 and 0.109 ± 0.001 (nm RIU −1 ) nm −1 , respectively. Conversely, hydrophobic NAA−μQVs are found to be slightly more sensitive toward changes of refractive index in aqueous medium, with sensitivities of 0.072 ± 0.002 and 0.066 ± 0.006 (nm RIU −1 ) nm −1 in water-and organicbased analytical solutions, respectively. Our advances provide insights into critical factors determining optical sensitivity in lightconfining nanoporous PC structures, with implications across optical sensing applications, and other photonic technologies.

Section: Experimental Sectionmentioning

confidence: 99%

Role of Spectral Resonance Features and Surface Chemistry in the Optical Sensitivity of Light-Confining Nanoporous Photonic Crystals

Law

Lim

et al. 2021

“…Photonic crystals (PCs) are dielectric optical structures with specifically engineered photonic bands to modify the group velocity of photons when these flow through the PC. Light–matter interactions in PCs can be tuned with precision by engineering the PC architecture so that regions with high and low refractive indexes are periodically and spatially distributed. − Distinct forms of PCs based on a wide range of materials can be produced to harness versatile control over electromagnetic waves across the broad spectrum, from UV to IR. PCs have found multiple applications, including photonic encoding, chemical sensing and biosensing, − lasing, and photocatalysis. , Since the pioneering works by Masuda and co-workers, nanoporous anodic alumina (NAA) has been an ideal base material for generating nanoporous PCs − due to its cylindrical nanopores with well-defined and highly controllable geometric features.…”

Section: Introductionmentioning

confidence: 99%

Tunable Nanoporous Anodic Alumina Photonic Crystals by Gaussian Pulse Anodization

Berto-Rosello

Xifré-Pérez

et al. 2020

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.

“…Photonic crystals (PCs) are a class of optical nanostructures with allowed and forbidden photonic bands that modify the movement of photons by altering the dispersion of electromagnetic waves when photons travel across the structure of PCs. These light–matter interactions can be tuned with accuracy by engineering the PCs’ structure, which features regularly distributed regions of high and low refractive index in one, two, or three dimensions. − PCs can be produced with different architectures and materials to attain light modulation across the broad range of spectral regions (from UV to IR), depending on the application needs. − …”

Section: Introductionmentioning

confidence: 99%

“…PCs modulate the flow of light when photons travel across the material. These light-matter interactions can be tuned with accuracy by engineering the PC´s structure, which features regularly distributed regions of high and low refractive index in one, two or three dimensions [8][9][10][11][12][13][14][15][16] . PCs can be produced with different architectures and materials to attain light modulation across the broad range of spectral regions (from UV to IR), depending on the application needs [17][18][19][20][21][22] .…”

mentioning

confidence: 99%

Stacked Nanoporous Anodic Alumina Gradient-Index Filters with Tunable Multispectral Photonic Stopbands as Sensing Platforms

Bertó-Roselló

Xifré-Pérez

et al. 2018

The new agreement specifically addresses what authors can do with different versions of their manuscripte.g. use in theses and collections, teaching and training, conference presentations, sharing with colleagues, and posting on websites and repositories. The terms under which these uses can occur are clearly identified to prevent misunderstandings that could jeopardize final publication of a manuscript (Section II, Permitted Uses by Authors).