Spectrum modulation-based field of view extension in Airy-beam tomographic microscopy.

We reveal the self-accelerating performance of an Airy beam under space-variable spectrum modulation, which corresponds to the extension of the field of view (FOV) and imaging depth in Airy-beam tomographic microscopy (ATM), resulting in the decline of fidelity and resolution of a reconstructed image with an increased FOV and depth of field (DOF). A strategy of spectrum modulation is proposed, and high-fidelity, high-resolution 3D imaging is realized in a 150 µm × 50 µm × 12 µm volume. This study offers a paradigm to improve the quality of reconstructed 3D images based on spectrum modulation for other light fields.

Characterizing spatial uniformity of tensile deformation with an elastic polymer based holographic sensor.

Tensile deformation uniformity of material has been studied with a stretchable polymer based holographic sensor. The diffraction spectrum distribution of a holographic grating with a large area as a main response parameter is scanned. A linear spatial distribution of peak wavelength provides an important foundation for exploring the tensile uniformity. The same ratio of wavelength to position confirms that the tensile deformation of the material is uniform in a small spot size. Over the entire length of the materials, gradually increasing deformation accumulation is the main uniformity feature of tensile deformation. The uniformity response is expected to apply in sensing the deformation and stress fluctuation distribution in the middle of the thin surface. The non-uniform distribution of stress can be expressed by the nonlinear distribution of the grating diffraction spectrum. The optical measurement of tensile deformation uniformity further validates the applicability of a stretchable polymer based holographic sensor.

Micro-deformation response of a holographic sensor in highly stretchable polymer hydrogel.

A volume grating-based holographic sensor in highly stretchable PVA/AA polymer for sensing its micro-deformation and, hence, the displacement has been studied. One-dimensional micro-displacement induced by tensile stress is analyzed using a diffraction spectrum in two kinds of sensor construction methods, i.e., transmission and reflection. The dependence of the peak wavelength on the displacement presents a good linear relationship which provides a quantitative sensing strategy for hydrogel micro-deformation. The available sensitivity is better than 4 µm/0.5 nm (displacement/wavelength shift) using a commercial spectrometer with a resolution of 0.5 nm. Finally, the reversible deformation response further validates the practical applicability of a holographic sensor constructed by photosensitive hydrogel. The optical measurement of micro-displacement as a novel sensing strategy can accelerate the development of the holographic optical element.

Improvement of temperature-induced spectrum characterization in a holographic sensor based on N-isopropylacrylamide photopolymer hydrogel: publisher's note.

This publisher's note amends the funding section in Appl. Opt.56, 9006 (2017)APOPAI0003-693510.1364/AO.56.009006.

Improvement of temperature-induced spectrum characterization in a holographic sensor based on N-isopropylacrylamide photopolymer hydrogel.

A novel thermo-sensitive N-isopropylacrylamide photopolymer was developed for improving the temperature and humidity responses of holographic sensors. Diffraction spectra of holographic volume gratings recorded in the materials were characterized to explore the sensing response capacity. A dependence of peak wavelength on the temperature was observed and provided a quantitative strategy for holographic sensing applications. Expansion of the humidity range induced a strong extension of wavelength shift. Finally, the temperature response reversibility was demonstrated experimentally. Our sensing results were completely different from the reported typical acrylamide polymer system. Compared with the former, we obtained a more sensitive temperature response and an evident shift expansion (>200 nm) at a relative humidity of 70% or higher. These results can obviously improve the thermo-sensitivity of a holographic sensor and expand the practical application area of the holographic sensing strategy.

Diffusional enhancement of volume gratings as an optimized strategy for holographic memory in PQ-PMMA photopolymer.

The dark enhancements of diffraction efficiency in single and multiple gratings are investigated theoretically and experimentally in phenanthrenequinone doped poly-(methyl methacrylate) materials. It is demonstrated a possibility to improve holographic characteristics of the material via the enhancement. Nearly 17-fold increment of diffraction efficiency is observed after exposure. The dependences of PQ's concentration on the rate and increment of dark enhancement are achieved quantitatively. And the enhancement in multiplexing is presented as a simple and efficient method to improve response of the material and homogeneity of diffraction efficiency. PQ's diffusion and enhancement process of refractive index modulation are simulated by a diffusion model for describing enhancement dynamics qualitatively and quantitatively. This study provides a significant foundation for the application of dark enhancement in holographic storage.

Synthesis and low-temperature photoluminescence properties of SnO2 nanowires and nanobelts.

Ultra-long rutile tin dioxide nanowires and nanobelts are synthesized by thermal oxidation of tin powder using gold film as the catalyst. Nanowire or nanobelts can be selectively produced by tuning the reaction temperature. The vapour-liquid-solid growth mechanism is proposed. The band gaps of the nanowires and nanobelts are 3.74 and 3.81 eV respectively, determined from UV/visible absorption spectral results. The SnO2 nanowires show stable photoluminescence with two emission peaks centred at around 470 and 560 nm. Their wavelengths stay almost fixed while their intensities depend sensitively on the temperatures within the examination ranges from 10 to 300 K. The SnO2 nanobelts show similar photoluminescence behaviours and the origin of the luminescence is discussed.