Enhancement of Luminous Intensity Emission from Incoherent LED Light Sources within the Detection Angle of 10° Using Metalenses

In this work, we present metalenses (MLs) designed to enhance the luminous intensity of incoherent light-emitting diodes (LEDs) within the detection angles of 0° and 10°. The detection angle of 0° refers to the center of the LED. Because the light emitted from LEDs is incoherent and expressed as a surface light source, they are numerically described as a set of point sources and calculated using incoherent summation. The titanium dioxide (TiO2) and amorphous silicon (a-Si) nanohole meta-atoms are designed; however, the full 2π phase coverage is not reached. Nevertheless, because the phase modulation at the edge of the ML is important, an ML is successfully designed. The typical phase profile of the ML enhances the luminous intensity at the center, and the phase profile is modified to increase the luminous intensity in the target detection angle region. Far field simulations are conducted to calculate the luminous intensity after 25 m of propagation. We demonstrate an enhancement of the luminous intensity at the center by 8551% and 2115% using TiO2 and a-Si MLs, respectively. Meanwhile, the TiO2 and a-Si MLs with the modified phase profiles enhance the luminous intensity within the detection angle of 10° by 263% and 30%, respectively.

Fully differentiable optimization protocols for non-equilibrium steady states

In the case of quantum systems interacting with multiple environments, the time-evolution of the reduced density matrix is described by the Liouvillian. For a variety of physical observables, the long-time limit or steady state solution is needed for the computation of desired physical observables. For inverse design or optimal control of such systems, the common approaches are based on brute-force search strategies. Here, we present a novel methodology, based on automatic differentiation, capable of differentiating the steady state solution with respect to any parameter of the Liouvillian. Our approach has a low memory cost, and is agnostic to the exact algorithm for computing the steady state. We illustrate the advantage of this method by inverse designing the parameters of a quantum heat transfer device that maximizes the heat current and the rectification coefficient. Additionally, we optimize the parameters of various Lindblad operators used in the simulation of energy transfer under natural incoherent light. We also present a sensitivity analysis of the steady state for energy transfer under natural incoherent light as a function of the incoherent- light pumping rate.

Ultrathin Picoscale White Light Interferometer

White light interferometry is a well established technique with diverse precision applications, however, the conventional interferometers such as Michelson, Mach-Zehnder or Linnik are large in size, demand tedious alignment for obtaining white light fringes, require noise-isolation to achieve sub-nanometric stability and importantly, exhibit unbalanced dispersion causing uncertainty in absolute zero delay reference. Here, we demonstrate an ultrathin white light interferometer enabling picometer resolution by exploiting the wavefront division of a broadband incoherent light beam after transmission through a pair of micrometer thin identical glass plates. Spatial overlap between the two diffracted split wavefronts readily produce high-contrast and stable white light fringes, with unambiguous reference to absolute zero path-delay position. The colored fringes evolve when one of the ultrathin plates is rotated to tune the interferometer with picometric precision over tens of µm range. Our theoretical analysis validates formation of fringes and highlights self-calibration of the interferometer for picoscale measurements. We demonstrate measurement of coherence lengths of several broadband incoherent sources as small as a few micrometer with picoscale precision. Furthermore, we propose a versatile double-pass configuration using the ultrathin interferometer enabling a sample cavity for additional applications in probing dynamical properties of matter.

The state of systemic immunity under the influence of polarized light and an immunomodulator in patients with HPV-associated cervicitis

Background. According to current epidemiological studies, 94.9% of women suffering from sexually transmitted infections are diagnosed with the presence of human papillomavirus (HPV) DNA during the examination. Aims. The aim of the study was to study the effect of combined exposure to blue monochromatic polarized incoherent light and polychromatic visible and infrared polarized light in combination with imihimod 5% cream for external use on the state of systemic immunity in patients with HPV-associated cervicitis. Materials and methods. The study included 60 patients aged 2035 years with an HPV-associated cervicitis with a history of at least 1 year, who were randomly divided into 3 groups: in the main group (n=20), course effects of blue monochromatic polarized incoherent light on the projection of the carotid arteries and polychromatic visible and infrared polarized light on the cervix in combination with imihimod 5% cream for external use (complex 1); in the comparison group (n=20) exposure to polychromatic visible and infrared polarized light on the cervix in combination with imihimod cream for external use 5% (complex 2); in the control group (n=20) a course of local exposure to the cervix with imihimod cream 5%. The data of the survey of 20 healthy women of the same age were taken as the values of the norm. The state of systemic immunity in patients with HPV-associated cervicitis before treatment and after the course was evaluated by the indicators of mature T-lymphocytes (CD3+), CD4+, CD8+, immunoregulatory index (IRI = CD4+/CD8+), CD16+ (natural killer cells) and CD20+ (B-mature lymphocytes) in peripheral blood. Results. Before the start of treatment, the patients showed low levels of CD3+-lymphocytes and a decrease in the immunoregulatory index, which is the ratio of CD4+/CD8+ against the background of an increase in the relative content of CD16+ and CD20+, which indicates an imbalance in the cellular immunity. After the course of treatment, the most pronounced results were obtained under the influence of complex 1: a significant increase in the relative content of CD3+ and normalization of IRI against the background of a decrease to the reference values of the initially elevated levels of CD16 (%) and CD20 (%) in both the percentage and absolute ratio of these populations in peripheral blood. Patients treated with complex 2 also showed a positive, but less pronounced, trend towards an increase in CD3+ and IRI and a decrease in elevated CD16+ levels after the course of treatment. In the control group, there was no statistically significant difference between the indicators before and after treatment, and only a slight positive trend was observed for some of them. Conclusion. The combined use of blue monochromatic polarized incoherent light on the projection of the carotid arteries in combination with polychromatic visible and infrared polarized light and imihimod 5% cream for external use on the cervix in patients with chronic cervicitis associated with papillomavirus infection, to a greater extent than the local use of polarized light in combination with imihimod 5%, has a pronounced immunocorrective effect on the cellular link of immunity.

The Effect of Noise-Induced Quantum Coherence in the Intermediate Band Solar Cells

It has been shown that quantum coherence induced by incoherent light can increase the efficiency of solar cells. Here we evaluate the effect of such coherence in the intermediate band solar cells. We first examine a six-level quantum IBSC model and demonstrate by simulation that the maximum of output power in a solar cell with quantum structure increases more than 16 percent in the case of coherence existence. We then propose an IBSC model which can absorb continuous spectra of sunlight and show that the quantum coherence can increase the output power of the cell. For instance, calculations indicate that the coherence makes an increase of about 31% in the maximum output power of a cell that the width of the conduction and intermediate bands are 100 and 10 meV, respectively. Also, our calculations show that the quantum coherence effect is still observed in increasing the solar cell power by expanding the width of the conduction band, although the output power is reduced due to increase in the thermalization loss. However, expanding the width of the intermediate band reduces the coherence effect.

Photon bubble turbulence in cold atom gases

Turbulent radiation flow is commonplace in systems with strong, incoherent, light-matter interactions. In astrophysical contexts, photon bubble turbulence is considered a key mechanism behind enhanced radiation transport, and its importance has been widely asserted for a variety of high energy objects such as accretion disks and massive stars. Here, we show that analogous conditions to those of dense astrophysical objects can be obtained in large clouds of cold atoms, prepared in a laser-cooling experiment, driven close to a sharp electronic resonance. By accessing the spatially-resolved atom density, we are able to identify a photon bubble instability and the resulting regime of photon bubble turbulence. We also develop a theoretical model describing the coupled dynamics of both photon and atom gases, which accurately describes the statistical properties of the turbulent regime. This study thus opens the possibility of simulating radiation-dominated astrophysical systems in cold atom experiments.

Optical Communications: The Beginning

The first efforts by Alexander Graham Bell at optical communications by incoherent light are discussed. Those were very inefficient at the time but after the invention of the laser it was only a question of time when coherent optical communication will dominate the communications scene The beginning was slow because propagation both in air and in fibre waveguide was too large. Enormous efforts by the Corning Glass Works brought down the attenuation to a figure as low as a few dbs per kilometre making some further applications feasible. The next break-through was the invention of the fibre amplifier enabling the erection of long relay-free lines (maybe up to 10,000 km) possible range of applications was greatly extended by the invention of the fibre amplifier. Coherent light propagation in thin, single-mode fibres is discussed a very thin fibre is discussed. It is shown that an optical fibre can carry an enormous number of communication channels. The laser was invented just in time to help produce the signals, and it also became possible to produce pure enough glass fibres in which an optical signal could propagate with low attenuation. The invention of erbium-doped fibre amplifiers allowed them to be spread all over the world, including large number of lines under the oceans.

Performance of Vehicular Visible Light Communications under the Effects of Atmospheric Turbulence with Aperture Averaging

In this paper, we investigate the performance of a vehicular visible light communications (VVLC) link with a non-collimated and incoherent light source (a light-emitting diode) as the transmitter (Tx), and two different optical receiver (Rx) types (a camera and photodiode (PD)) under atmospheric turbulence (AT) conditions with aperture averaging (AA). First, we present simulation results indicating performance improvements in the signal-to-noise ratio (SNR) under AT with AA with increasing size of the optical concentrator. Experimental investigations demonstrate the potency of AA in mitigating the induced signal fading due to the weak to moderate AT regimes in a VVLC system. The experimental results obtained with AA show that the link’s performance was stable in terms of the average SNR and the peak SNR for the PD and camera-based Rx links, respectively with <1 dB SNR penalty for both Rxs, as the strength of AT increases compared with the link with no AT.