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Due to the advantages of narrow energy distribution of plasmonic hot-electrons in Ag and the high density of states in the TiO2 conduction band, an Ag/TiO2 composite is considered to be an ideal combination to construct a plasmonic hot-electron photodetector with high detectivity and a high response speed. In this work, we fabricate a porous Ag/TiO2-Schottky-diode based plasmonic hot-electron photodetector. This detector shows a high detectivity of 9.8 × 1010 cmHz1/2/W and a fast response speed, with a rise and fall time of 112 μs and 24 μs, respectively, under 450 nm light illumination at zero bias voltage. In addition, the height of the Ag/TiO2 Schottky barrier can be decreased by removing the chemisorbed oxygen from the surface of TiO2 with ultraviolet light illumination, and as a result, the responsivity of the Ag/TiO2 plasmonic hot-electron photodetector at 450 nm can increase from 3.4 mA/W to 7.4 mA/W.

This paper presents a systematic study of Raman spectra of nanocomposite photonic crystals produced using opal matrices or anodic aluminum oxide and filled with various inorganic compounds. We compare Raman spectra of the starting inorganic compounds (K2Cr2O7, CrO3, and KIO3) and nanocomposite photonic crystals whose pores are filled with the inorganic substances. Our results open up the possibility of producing high-performance sensors of inorganic substances introduced into the pores of photonic crystals, based on analysis of enhanced Raman scattering in a nanocomposite photonic crystal.

The optical properties of a one-dimensional photonic crystal based on porous alumina with a crystal lattice constant of 460 nm were studied. The experimentally measured transmission spectrum of a one-dimensional photonic crystal film was compared with the theoretical spectrum in the spectral regions corresponding to the first, second, and third stop bands. The potential for using one-dimensional porous alumina photonic crystals as selective narrow-band filters and sensors was analyzed. Embedding a Raman-active medium into the voids of porous photonic crystal should provide an essential increase of spontaneous Raman scattering signal and low-threshold stimulated Raman scattering. The amount of substance needed for recording Raman spectra may be substantially decreased.

In this article, pure and tungsten-doped (W-doped) highly ordered two-dimensional (2D) vanadium dioxide (VO2) nanowire arrays were successfully prepared by a hydrothermal treatment, followed by a self-assembly progress and the in-situ high temperature treatment. The infrared photodetector devices based on monoclinic VO2 (VO2(M)) and W-doped VO2(M) nanowires were comparatively studied . It was found that the device based on W-doped VO2(M) nanowires exhibits a rapid infrared response and an enhanced photoelectric responsivity of 21.4 mA/W under the incident infrared light intensity of 280 mW/cm2, which is nearly two orders of magnitude superior to pure VO2(M) nanowire array. Our experimental results provided a direct and convenient path for design of future high-performance photodetector devices.

The angular dependences of the transmission of a one-dimensional photonic crystal based on porous anodic aluminum oxide are studied in the wavelength range of 320–1200 nm. The possibility of using porous one-dimensional photonic crystals based on aluminum oxide as selective narrowband optical filters and mirrors is studied.

Tb3+-doped TiO2 (TiO2:Tb3+) films are synthesized by a facile sol-gel method. The hot-electron current of Au/TiO2:Tb3+ Schottky diodes was enhanced by UV light decreasing the height of Schottky barrier. Compared with pure TiO2, doping Tb3+ can reduce the background current originating from the internal photoelectric effect in TiO2, and improve the on/off ratio. This is due to the energy and charge transfer mechanism from TiO2 to Tb3+. Photogenerated electrons in TiO2:Tb3+ films excited by UV light can be consumed by radiative electron transitions from the level 5D4 to the 7Fj (j=6, 5, 4, 3) for Tb3+. This is beneficial and effective to regulate the electronic state of optoelectronic materials.

Herein, we report an enhanced tunable broadband wavelength-selective lead sulfide (PbS) film detector integrated with Au-nanorod arrays that were obtained by using an ultrathin open-ended porous titanium dioxide membrane (UOP-TM) as a mask. The responsivity of the PbS films with periodic Au-nanorods exhibits a drastic enhancement by up to 125%–175% due to the enhancement of the localized electromagnetic fields around the gold nanorods. Notably, the location of the strongest enhancement peak of photocurrent shifted from 450 to 980 nm as the height of the Au-nanorods increased from 30 to 120 nm. In addition, the responsivity and detectivity of the hybrid PbS film modified with 90 nm Au-nanorod arrays under laser illumination of 980 nm are as high as 944 mA W−1 and 1.72 × 1010 cm Hz1/2 W−1, respectively. These excellent figures-of-merit of the tunable broadband plasma-enhanced PbS films could be a promising candidate in future wavelength-selective photodetector applications.

Designing and fabrication of the infrared antireflection coatings are quite important for the application of infrared optical elements. Herein, double-layer two wavelength infrared antireflective (AR) coating was prepared on CdSe substrate by sol-gel method, in which the bottom layer is porous TiO2 film and the top layer is SiO2 nanoparticle film containing a small amount of TiO2 (molar ratio of Si/Ti is 7.7). The reflectivity of the coated sample is about 2.1% at 2000 nm and 2.8% at 2500 nm, respectively, and the average reflectivity of the whole wide band from 1800 nm to 2600 nm is about 2.6%, which is about 27% lower than that of uncoated CdSe substrate. By adding reasonable additives and designing the film structure, the problem that thick infrared film is not resistant to high temperature annealing was solved. Moreover, the AR coating shows a super hydrophilicity, which can avoid the influence of water mist condensation on the transmittance. Importantly, this AR coating exhibits a good thermal shock resistance, and the reflection spectrum of the film did not change after ten thermal shock cycles at 400 °C, which meaning this film can be expected to meet the requirements of high temperature irradiation environment. This work provides important guidance for the preparation of infrared AR film with high thermal stability.

High-quality Sn2+-sensitized PbS films were deposited via a cost‐effective chemical route. The results demonstrate that the Sn2+-sensitized PbS thin films have better crystallinity and larger grain size. Photoelectric performance of Sn2+-sensitized PbS films has been improved greatly in the visible and near-infrared range. With Sn2+ sensibilization, photoresponsivity is more than 9 times higher, and detectivity is as high as ~1010 cm2 Hz1/2 W−1. Notably, the response speed of the Sn2+-sensitized PbS films reaches a magnitude of microseconds, which is over 105 times improvements compared with the pure PbS film devices. Additionally, high-frequency switching behavior at 4 kHz shows excellent stability. Based on the feasible method and excellent photoelectric performance of the devices, it has been demonstrated that Sn2+ sensibilization is of viability to improve the detection performance of commercial photodetectors.

In this paper, we fabricate ordered pore array (OPA) Ag film coated glass with the aid of polystyrene sphere (PS) array templates. This kind of OPA Ag coated glass has optical advantages of visible transparency, blue and near-infrared resistance. The average visible transmittance is 68%, including a transmission peak of 78% located at 570 nm, and low average transmittance of 48% in the blue light region that is not damaging to the eyes. The near-infrared light blocking rate is 67%, among which 40% light is reflected directly, indicating the reflection domination.

A highly transparent and super-hydrophilic double-layer anti-reflection coating was prepared by a simple and economical sol-gel method based on the glass substrate. The bottom and top layer were respectively made with SiO2–TiO2 sol and SiO2–TiO2-PEG300 sol. The average transmittance of the substrate coated with the double-layer coating is increased by 7% up to 97.4% in the visible light band, and the peak transmittance reaches 99% at about 550 nm. In addition, double-layer anti-reflection coating shows a good super-hydrophilic self-cleaning performance, and the transmittance of the coating can be restored by simple washing with water. Furthermore, due to the existence of anatase TiO2, the composite coating can restore the super-hydrophilicity damaged by dust under UV light.

Anodic aluminum oxide based photonic crystals with periodic porous structure have been prepared using voltage compensation method. The as-prepared sample showed an ultra-narrow photonic bandgap. Asymmetric line-shape profiles of the photonic bandgaps have been observed, which is attributed to Fano resonance between the photonic bandgap state of photonic crystal and continuum scattering state of porous structure. And the exhibited Fano resonance shows more clearly when the sample is saturated ethanol gas than air-filled. Further theoretical analysis by transfer matrix method verified these results. These findings provide a better understanding on the nature of photonic bandgaps of photonic crystals made up of porous materials, in which the porous structures not only exist as layers of effective-refractive-index material providing Bragg scattering, but also provide a continuum light scattering state to interact with Bragg scattering state to show an asymmetric line-shape profile.

The phenomenon of extraordinary and multi-broadband optical transmission through sub-wavelength metallic grating with symmetry breaking has been theoretically investigated. Under normal incident light, the radiative and dark modes appear in adjacent slits of the grating with asymmetric heights. Through the destructive interference of alternative radiative and dark modes, multiple broadband transmission and enhanced light propagation is realized. The counter-propagating light circulation results in sharp dips in the transmission spectrum. These characteristics of the asymmetric grating could provide highly controllable ways to design novel devices.

In this work, we demonstrated the use of a promising sensor based on alumina Photonic Crystals (PC) which can be applied in the field of gas detection owing to the well structured PC with an ultra-narrow Photonic Bandgap (PBG), of which the full width at half maximum is only 30 nm. This type of PC was prepared successfully by using a compensation voltage mode method, which can effectively compensate for the chemical corrosion and the slowing down of ion exchange, resulting in a uniform diameter of the pores in the anodic alumina oxidation (AAO) from beginning to end. The as-prepared sample was applied to detect the concentration of organic vapor, such as ethanol, in this experiment. A large PBG shift is achieved when the concentration of ethanol changes, and the mechanism was also discussed theoretically. This sensor had a good repeatability due to the chemical and physical stability of the matrix material (alumina). These results indicate the potential applications of the as-prepared AAO based PC in the sensing field.