Luminescent Cavity Design for High Ambient Contrast Ratio, High Efficiency Displays

A key display characteristic is its efficiency (emitted light power divided by input power). While display efficiencies are being improved through emissive (e.g., quantum dot and organic light emitting display (OLED) designs1,2, which remove the highly inefficient color filters found in traditional liquid crystal displays (LCDs)3,4, polarization filters, which block about 50% of the light, remain required to inhibit ambient light reflection. We introduce a luminescent cavity design to replace both the color and polarization filters. Narrow-band, large Stokes shift, CdSe/CdS quantum dot emitters are embedded in a reflective cavity pixel element with a small top aperture. The remainder of the top surface is coated black reducing ambient light reflection. A single pixel demonstrates an extraction efficiency of 40.9% from a cavity with an 11% aperture opening. A simple proof-of-concept multi-pixel array is demonstrated.

INTEGRATION OF DAYLIGHT WITH ELECTRIC LIGHTING IN COMMERCIAL BUILDINGS: A CASE STUDY FROM NEPAL

Daylight attributes to the aggregate of direct and indirect lights originating from the sun during the daytime. Integrating daylight with electrical lighting can serve as a means to lessen electricity costs for buildings. Geographic location and weather conditions facilitate most of the areas of Nepal to receive on average 12 hours of daylight and have huge energy-saving potential. However, the integration of daylight has not been admitted in the building code of Nepal. Moreover, contemporary architectural design lacks employment of techniques illustrated by illumination engineering to integrate daylight. This study analyses the plausibility and benefits of integrating daylight with electric light for a typical commercial building of Nepal employing the DIALux model and simulation. Simulation integrating energy-efficient electric light and daylight was done to observe illumination levels and light power density. For daylight performance, year-round conditions were observed for three different sky types. Modification of building architecture to integrate daylighting components was also studied. In the later part of the study, analysis was done to observe energy-saving potential and financial benefits. Results designated the plausibility of blending daylight with electrical lighting in the building for all-sky conditions. Extensive energy thrift was observed and was higher with added daylight components. Recommendations of the study to blend light sources and incorporation of daylight components are attainable with current technology and trend in Nepal with accompanying benefits of energy-saving, reduced operation, and reduced maintenance cost.

The importance of doping TiO2 into polypyrrol nanofibers to improve their optical sensitivity

In this study Electrochemical polymerization was used to make polypyrrol nanofiber. The in situ chemical oxidative polymerization approach was used to create a nanocomposite of polypyrrole PPy-TiO2. To achieve homogeneous dispersion inside the PPy matrix, the TiO2 was dissolved and ultrasonically dispersed. The surface morphology of polypyrrol and PPy/TiO2 nanocomposites was studied using field emission scanning electron microscopy (FE-SEM), which revealed of a polypyrrol nanofibre network and showed that the TiO2 nanoparticles was well incorporated. The produced PPy/TiO2 nanocomposite was characterized using XRD (X-Ray diffraction) and FT-IR (Fourier Transform Infrared). The formation of TiO2 nanoparticales on a PPy layer matrix was discovered, as well as homogeneous dispersion of TiO2 inside the PPy matrix and considerable interaction between PPy and TiO2. The produced PPy/TiO2 nanocomposite sensors’ response was investigated towards of light-power sensitivity. The PPy/TiO2 synergistic effects improve the light sensitivity qualities of the photodetector. The maximium sensitivity of PPy/TiO2 was around (188 %) at 20% TiO2 concentration at a light power of 30 mW for a laser diode 720 nm, while the rise time and fall time was ≈ 2.5sec.

MORPHOLOGICAL AND OPTICAL STUDIES OF PZN-4.5PT NANOPARTICLES THIN FILMS ON NANOSTRUCTURED SILICON SUBSTRATE

The development of renewable energies is today essential to be able to respond in a sustainably way to the growing energy needs on a global scale, as well as to reduce the greenhouse gas emissions responsible for global warming. Among these energies, photovoltaic technology, which converts light power of the sun (renewable source) into electric power, is a major player in the energy transition. However, there is now a need to develop efficient, competitive and less polluting photovoltaic technologies, allowing more energy to be produced at a lower cost. The Pb (Zn_1/3 Nb_2/3) O₃ (PZN) relaxor and its solid solutions with ferroelectric PbTiO₃ (PT) are of considerable interest both from the applications point of view and from the scientific point of view. In the past, numerous attempts have been made to prepare and study the properties of these materials in the form of thin layers for photovoltaic applications. However, due to the difficulties in preparing pure phase films with a high PZN content, there is very little knowledge of the properties of these materials. The objective of this work is to prepare PZN-4.5PT nanoparticle thin films, to study in detail their morphological and optical properties. The studies were carried out in three main directions: preparation of thin layers (PZN-PT) by deposit of spin coating, and characterize for optical and morphological properties (SEM). UV-visible measurements allowed us to have reflectance of less than 30% after deposit a thin layer PZN-4.5PT doped 1% Mn and undoped for a 70 at 80% absorption in UV-Visible-NIR.

Cantilever enhanced based photoacoustic detection of SF6 decomposition component SO2 using UV LED

Purpose This paper aims to establish a photoacoustic detection system for SO2 using UV-LED and testify its feasibility for sensitive measurement. The work in this paper can avoid potential crossover interference in infrared (IR) range and also balance the capability and cost of feasible excitation for photoacoustic detection system. Design/methodology/approach In this experimental work, a cantilever-enhanced–based photoacoustic SO2 detection system using an ultraviolet (UV) LED light source with a light power of 4 mW as the excitation was established. Findings A feasible photoacoustic detection system for SO2 using UV-LED was established. Experimental results demonstrate that the detection limit of the system can reach the level of 0.667 ppm, which can serve as a reference for the application of PAS in insulation fault diagnosis. Originality/value This work investigated the potential of using ultraviolet photoacoustic spectroscopy to detect trace SO2, which provided an ideal replacement of infrared-laser-based detection system. In this paper, a photoacoustic detection system using LED with a low light power was established. Low light power requirement can expand the options of light sources accordingly. In this paper, the absorption characteristics of SO2 in the presented detection system and ultraviolet range were studied. And the detection limit of the presented system was given. Both of which can provide reference to SO2 detection in ambient SF6.

Experimental demonstration of confidential communication with quantum security monitoring

Security issues and attack management of optical communication have come increasingly important. Quantum techniques are explored to secure or protect classical communication. In this paper, we present a method for in-service optical physical layer security monitoring that has vacuum-noise level sensitivity without classical security loopholes. This quantum-based method of eavesdropping detection, similar to that used in conventional pilot tone systems, is achieved by sending quantum signals, here comprised of continuous variable quantum states, i.e. weak coherent states modulated at the quantum level. An experimental demonstration of attack detection using the technique was presented for an ideal fibre tapping attack that taps 1% of the ongoing light in a 10 dB channel, and also an ideal correlated jamming attack in the same channel that maintains the light power with excess noise increased by 0.5 shot noise unit. The quantum monitoring system monitors suspicious changes in the quantum signal with the help of advanced data processing algorithms. In addition, unlike the CV-QKD system which is very sensitive to channel excess noise and receiver system noise, the quantum monitoring is potentially more compatible with current optical infrastructure, as it lowers the system requirements and potentially allows much higher classical data rate communication with links length up to 100 s km.

In situ laser manipulation of root tissues in transparent soil

Aims Laser micromanipulation such as dissection or optical trapping enables remote physical modification of the activity of tissues, cells and organelles. To date, applications of laser manipulation to plant roots grown in soil have been limited. Here, we show laser manipulation can be applied in situ when plant roots are grown in transparent soil. Methods We have developed a Q-switched laser manipulation and imaging instrument to perform controlled dissection of roots and to study light-induced root growth responses. We performed a detailed characterisation of the properties of the cutting beams through the soil, studying dissection and optical ablation. Furthermore, we also studied the use of low light doses to control the root elongation rate of lettuce seedlings (Lactuca sativa) in air, agar, gel and transparent soil. Results We show that whilst soil inhomogeneities affect the thickness and circularity of the beam, those distortions are not inherently limiting. The ability to induce changes in root elongation or complete dissection of microscopic regions of the root is robust to substrate heterogeneity and microscopy set up and is maintained following the limited distortions induced by the transparent soil environment. Conclusions Our findings show that controlled in situ laser dissection of root tissues is possible with a simple and low-cost optical set-up. We also show that, in the absence of dissection, a reduced laser light power density can provide reversible control of root growth, achieving a precise “point and shoot” method for root manipulation.

Ion transport activity and optogenetics capability of light-driven Na+-pump KR2

KR2 from marine bacteria Krokinobacter eikastus is a light-driven Na+ pumping rhodopsin family (NaRs) member that actively transports Na+ and/or H+ depending on the ionic state. We here report electrophysiological studies on KR2 to address ion-transport properties under various electrochemical potentials of Δ[Na+], ΔpH, membrane voltage and light quality, because the contributions of these on the pumping activity were less understood so far. After transient expression of KR2 in mammalian cultured cells (ND7/23 cells), photocurrents were measured by whole-cell patch clamp under various intracellular Na+ and pH conditions. When KR2 was continuously illuminated with LED light, two distinct time constants were obtained depending on the Na+ concentration. KR2 exhibited slow ion transport (τoff of 28 ms) below 1.1 mM NaCl and rapid transport (τoff of 11 ms) above 11 mM NaCl. This indicates distinct transporting kinetics of H+ and Na+. Photocurrent amplitude (current density) depends on the intracellular Na+ concentration, as is expected for a Na+ pump. The M-intermediate in the photocycle of KR2 could be transferred into the dark state without net ion transport by blue light illumination on top of green light. The M intermediate was stabilized by higher membrane voltage. Furthermore, we assessed the optogenetic silencing effect of rat cortical neurons after expressing KR2. Light power dependency revealed that action potential was profoundly inhibited by 1.5 mW/mm2 green light illumination, confirming the ability to apply KR2 as an optogenetics silencer.