Solar-Blind Photodetector with Lower Dark Current and Higher Ilight/Idark Ratio Based on Mg0.38Zn0.62O Film Deposited by Pulsed Laser Deposition Method.

In this study, pulsed laser deposition method (PLD) was employed to grow MgxZn1-xO films on quartz substrates. The optimal deposition temperature of 300 °C for MgxZn1-xO film was decided and Mg0.38Zn0.62O, Mg0.56Zn0.44O and Mg0.69Zn0.31O films were grown respectively using MgxZn1-xO targets with different Mg contents (x = 0.3, 0.5 and 0.7). As-deposited Mg0.38Zn0.62O film possessed the mixed-phase (hexagonal and cubic phase) structure, appropriate band gap of 4.68 eV and smaller surface roughness of 1.72 nm, and the solar-blind photodetector (PD) based on it was fabricated. The key features of our PD are the cutoff wavelength of 265 nm lying in solar-blind band, lower dark current (Idark) of 88 pA, higher peak responsivity of 0.10 A/W and bigger Ilight/Idark ratio of 1688, which provide the new idea for the application of solar-blind PDs based on MgxZn1-xO films.

Electric field controlled near-infrared high-speed electro-optic switching modulator integrated with 2D MgO.

The electro-optic effect in two-dimensional (2D) MgO nanoflakes synthesized by a microwave-assisted process is demonstrated using a designed optical fiber modulator. The guiding properties of intense core modes excited by the material cavity are modulated by the external electric field. The feasibility of 2D MgO nanoflakes as an effective electro-optic modulator and switching are experimentally verified for the first time, to the best of our knowledge. The proposed optical-fiber-based electro-optic modulator achieves a linear wavelength shift with a high sensitivity of 12.87 pm/V(77.22 nm/kV/mm, in the electric field). The results show that MgO, as a metal oxide 2D material, is a very promising material for electro-optic modulators and switching.

Solar-Blind Photodetector with Lower Dark Current and Higher Ilight/Idark Ratio Based on Mg0.38Zn0.62O Film Deposited by Pulsed Laser Deposition Method.

In this study, pulsed laser deposition method (PLD) was employed to grow MgxZn1-xO films on quartz substrates. The optimal deposition temperature of 300 °C for MgxZn1-xO film was decided and Mg0.38Zn0.62O, Mg0.56Zn0.44O and Mg0.69Zn0.31O films were grown respectively using MgxZn1-xO targets with different Mg contents (x = 0.3, 0.5 and 0.7). As-deposited Mg0.38Zn0.62O film possessed the mixed-phase (hexagonal and cubic phase) structure, appropriate band gap of 4.68 eV and smaller surface roughness of 1.72 nm, and the solar-blind photodetector (PD) based on it was fabricated. The key features of our PD are the cutoff wavelength of 265 nm lying in solar-blind band, lower dark current (Idark) of 88 pA, higher peak responsivity of 0.10 A/W and bigger Ilight/Idark ratio of 1688, which provide the new idea for the application of solar-blind PDs based on MgxZn1-xO films.

High Sensitivity NO2 Gas Sensor Based on 3D WO3 Microflowers Assembled by Numerous Nanoplates.

Tungsten oxide microflowers (WO3 MFs) were fabricated by a simple hydrothermal process through adjusting the pH of the solution by HCl. These MFs possess the outer diameters of about 2 µm and are composed of numerous nanoplates with the average pore size of 10.9 nm. Chemiresistive activity of as-fabricated WO3 MFs sensor was attempted towards oxidizing and reducing target gases, revealing a superior selectivity to NO2 with a maximum response of 22.95 (2 ppm NO2) @105 °C compared to other target gases. One of the key features of as-fabricatedWO3 MFs sensor is the lower detection limit of 125 ppb and operating temperature of 105 °C to NO2 with better reproducibility, signifying commercial prospective of the developed sensor materials. Finally, the gas sensing mechanism of WO3 MFs sensor has been proposed.

Field Emission Properties of Molybdenum Nanoparticles Decorated ZnO Nanorod Arrays.

Precisely controlled dimensions of heterostructured ZnO nanorod arrays were grown on micropatterned Au films supported by Si substrate using chemical vapor deposition (CVD). The field emission properties were attributed to pointed nanorods, thickness of catalyst, preferential growth, density, morphology of ZnO and Molybdenum (Mo) decorated ZnO nanorod arrays (Mo/ZnO). The selective restrained heterostructure approach resulted in excellent control over periodicity, location and density of ZnO nanorod arrays. Overall, field emission properties of bare ZnO nanorod arrays showed a low turn-on field of ~4.7 V/µm and a high field enhancement factor (ß) ~1686 to 7.3 V/µm and (ß) ~807 for Mo/ZnO. It was also found that the field emission properties were significantly influenced by densely decorated Mo nanoparticles on as-grown ZnO nanorod arrays.

Direct measurement of the Goos-Hänchen shift using a scanning quadrant detector and a polarization maintaining fiber.

High precision measurements of optical beam shifts are important in various fields including sensing, atomic force microscopy, and measuring beam shifts at interfaces. Sub-micron shifts are generally measured by indirect techniques such as weak measurements. We demonstrate a straightforward and robust measurement scheme for the shift, based on a scanning quadrant photodiode (QPD) that is biased using a low noise electronic circuit. The shift is measured with respect to a reference beam that is co-propagating with the signal beam. Thus, the shift of the signal beam is readout directly as the difference between the x-intercepts of the QPD scan plot of the signal and reference beams versus the position of the detector. To measure the beam shift, we use polarization multiplexing scheme where the p-polarized signal and s-polarized reference beams are modulated at two different frequencies and co-launched into a polarization-maintaining fiber. Both the signal and reference beam positions are readout by two lock-in amplifiers simultaneously. In order to demonstrate the utility of this method, we perform a direct measurement of Goos-Hänchen shift of a beam that is reflected from a plane gold surface. Accuracy of 150 nm is achieved using this technique.

Lithium niobate nanoparticle-coated Y-coupler optical fiber for enhanced electro-optic sensitivity.

Single crystals of lithium niobate (LiNbO3), possessing high birefringence and anisotropic properties have been explored, for a long time, to harness their excellent electro-optic properties. However, their nanoforms are comparatively less explored. In this context, dielectric constant and polarization (P) versus electric-field (E) characteristics of LiNbO3 nanomaterials have been studied. A nonideal P-E loop and a dielectric constant of 20 at the onset of 1 kHz were seen. The electro-optic sensitivity was found to be 4 times as compared to the bulk LiNbO3 crystals. The results are attributed to oxygen vacancies, antisite defects, and grain boundary effects in an already congruent structural matrix of LiNbO3.