Optical physics

In this paper, we show numerically and experimentally that expectation maximization (EM) algorithm is a powerful tool in combating system impairments such as fibre nonlinearities, inphase and quadrature (I/Q) modulator imperfections and laser linewidth. The EM algorithm is an iterative algorithm that can be used to compensate for the impairments which have an imprint on a signal constellation, i.e. rotation and distortion of the constellation points. The EM is especially effective for combating non-linear phase noise (NLPN). It is because NLPN severely distorts the signal constellation and this can be tracked by the EM. The gain in the nonlinear system tolerance for the system under consideration is shown to be dependent on the transmission scenario. We show experimentally that for a dispersion managed polarization multiplexed 16-QAM system at 14 Gbaud a gain in the nonlinear system tolerance of up to 3 dB can be obtained. For, a dispersion unmanaged system this gain reduces to 0.5 dB.

Grating Coupled Interferometry (GCI) using high quality waveguides with two incoupling and one outcoupling grating areas is introduced to increase and precisely control the sensing length of the device; and to make the sensor design suitable for plate-based multiplexing. In contrast to other interferometric arrangements, the sensor chips are interrogated with a single expanded laser beam illuminating both incoupling gratings simultaneously. In order to obtain the interference signal, only half of the beam is phase modulated using a laterally divided two-cell liquid crystal modulator. The developed highly symmetrical arrangement of the interferometric arms increases the stability and at the same time offers straightforward integration of parallel sensing channels. The device characteristics are demonstrated for both TE and TM polarized modes.

An interferometric sensor based on gratings on a planar waveguide is introduced. The device combines the advantages of known interference-based waveguide sensors with the simplicity of grating couplers. In the presented configuration, two parallel and coherent light beams, laterally separated in the direction of mode propagation, are coupled into a planar waveguide through a grating. One of the coupled beams is phase modulated using a periodically relaxing liquid crystal modulator, resulting in a time varying intensity signal at the end face of the waveguide. Refractive index changes within the waveguide section between the two coupling regions are monitored by observing characteristic changes in the intensity signal. PACS 42.79 • 07.60 Ever since the first demonstration of integrated optical waveguide sensors, the field has been under intense research and development. Application areas range from refractometry, gas and humidity sensors to the real-time monitoring of molecular binding effects, bacteria and living cells in aqueous solutions . The basic working principle common to all waveguide sensors consists in detecting tiny variations of the refractive

Since atmospheric turbulence and pointing errors cause signal intensity fluctuations and the background radiation surrounding the free-space optical (FSO) receiver contributes an undesired noisy component, the receiver requires accurate channel state information (CSI) and background information to adjust the detection threshold. In most previous studies, for CSI acquisition, pilot symbols were employed, which leads to a reduction of spectral and energy efficiency; and an impractical assumption that the background radiation component is perfectly known was made. In this paper, we develop an efficient and robust sequence receiver, which acquires the CSI and the background information implicitly and requires no knowledge about the channel model information. It is robust since it can automatically estimate the CSI and background component and detect the data sequence accordingly. Its decision metric has a simple form and involves no integrals, and thus can be easily evaluated. A Viterbitype trellis-search algorithm is adopted to improve the search efficiency, and a selective-store strategy is adopted to overcome a potential error floor problem as well as to increase the memory efficiency. To further simplify the receiver, a decision-feedback symbol-by-symbol receiver is proposed as an approximation of the sequence receiver. By simulations and theoretical analysis, we show that the performance of both the sequence receiver and the symbol-by-symbol receiver, approach that of detection with perfect knowledge of the CSI and background radiation, as the length of the window for forming the decision metric increases.

We employed a vertical evaporation technique to fabricate saturable absorbers by embedding single wall carbon nanotubes (SWCNT) in polymer (vinylalcohol). Two fast recovery time constants, 250 fs and 1.13 ps, respectively, were measured for the absorbers using a transient absorption experimental setup. The saturation intensity of the absorber was found to be 300-400 μJ/cm 2 at 1060 nm, and a modulation depth as high as 3.5% was achieved.

Using the vertical evaporation technique we fabricated saturable absorbers by transferring the water soluble single wall carbon nanotubes (SWCNT) onto a hydrophilic quartz substrate. The fast recovery times of the absorber were measured to be 136 and 790 fs. The modulation depth of the absorber was about 2%. Passive mode locked Nd:GdVO 4 laser using such an absorber was demonstrated. The continuous wave mode locked pulses with the pulse duration of 12.4 ps and the repetition of 120 MHz were achieved. The maximum average output power of the mode locked laser is 2.4 W at the pump power of 13 W. Such kind of absorber has potential to be put into practical use for high power solid state laser mode locking.

This paper presents the experimental results on the low temperature absorption and dispersion properties for a variety of frequently used infrared filter substrate materials. Index of refraction ðnÞ and transmission spectra are presented for a range of temperatures 300-50 K for the Group IV materials silicon (Si) and germanium (Ge), and Group II-VI materials zinc selenide (ZnSe), zinc sulphide (ZnS) and cadmium telluride (CdTe).

We describe and characterize a 25 GHz laser frequency comb based on a cavity-filtered erbium fiber mode-locked laser. The comb provides a uniform array of optical frequencies spanning 1450 nm to 1700 nm, and is stabilized by use of a global positioning system referenced atomic clock. This comb was deployed at the 9.2 m Hobby-Eberly telescope at the McDonald Observatory where it was used as a radial velocity calibration source for the fiber-fed Pathfinder near-infrared spectrograph. Stellar targets were observed in three echelle orders over four nights, and radial velocity precision of ∼10 m/s (∼6 MHz) was achieved from the comb-calibrated spectra.

Non relativistic and relativistic transition rates were observed for the deep tunnel regime for the case of a linear polarized laser field. The contribution of the initial momentum of an ejected photoelectron, the ponderomotive potential and the linear Stark shift for the Ar atom and its ions were taken into account. It was shown that, in both regimes, these processes have an influence on the transition rate behavior. The curves obtained for the transition rate show that with increasing laser filed intensities and ion charge the influence of relativistic effects increases.

Nano-structured materials exhibit unique properties such as coulomb blockade, blue-shifted absorption edge, shape-dependent spectroscopic transitions, surface mediated transitions, and electronic energy levels [1-5]. ZnO nanocrystals were prepared using a modification of the wet-chemical procedure developed by Spanhel and Anderson and variations of the same [6, 7, 8, 9, 10]. Next, 6g PEO (m.w. 600,000 g/mol) was dissolved in 120 ml de-ionised water and mixed with the nanocrystals in ethanol twelve hours after its preparation. Solid films were prepared by drying the samples at 30 C for three days. Alternating Current (AC) and Direct Current (DC) measurements were carried out at room temperature under ambient lighting conditions. Direct current supply was from a 9 V battery, AC supply was 0 – 300 V at 50 Hz. For DC measurements, the sample was placed in between flat copper electrodes to form a “capacitor”. For AC measurements, the copper electrodes were placed 2 cm apart to form a “re...

The corrosion behaviour of the AlSi1MgMn laser-shock-processed aluminium alloy was investigated in 3.5% NaCl water solution at ph7 and 23°C. Potentiodynamic polarization tests were conducted at a scanning rate of 10mV/s, starting at 2000mV SCE . Corrosion plots showed pitting corrosion attack. Surface conditions after corrosion tests at different pulse density levels were evaluated with optical microscopy, scanning electron microscopy (SEM), EDS analysis and innovative non-destructive 3D surface metrology method. The SEM analysis showed a large presence of chloride and oxide products near the pits. The non-destructive 3D metrology method proved to be an extremely perspective method to determine surface conditions in a way the traditional microscopy could not. The results of the research confirm its use in detail analysis of the pits formed at the surface as a result of electrochemical corrosion attack. The tests confirm that a greater pulse density of the surface treated guarantees ...

Experimental characterization of an amplifier's nonlinear properties at 24 GHz is presented in single and dual-band operation using orthogonal frequency-division multiplex signals. A test system for characterizing an amplifier's nonlinear properties at millimeter-wave frequencies for single and dual-band excitation is presented. The use of standard instrument enables a feasible test system. Analytical expressions based on a statistical analysis of signals and hardware impairments were used to analyze the experimental data versus power level and found to describe well the experimental results, including inter-and cross-modulation distortion. Parameters are derived that could be used in system studies.

This letter presents a triple band coplanar waveguide antenna with dual polarization characteristics. The proposed antenna exhibits both linear polarization and circular polarization characteristics. Triple band nature is achieved by using a flared ground plane. Circular polarization is achieved by terminating the feed line by a g/4 length stub, as this result in excitation of even-odd modes in phase quadrature. Resonating frequency of higher band is tuned by embedding a narrow slit (ws) in the ground plane. The antenna has compact 0.78 g × 0.78 g × 0.03 g geometry with circular polarization characteristics extending from 2.7 GHz 3.42 GHz and linear polarized characteristics from 4.4 GHz 5.16 GHz and 6.2 GHz 6.9 GHz. The lower band is circular polarized while the middle and upper bands are linear polarized and can be applied for WiMAX and C-band broadcasting applications.

In this study, CuxTa2-xO5 compositions were investigated for advanced thermoelectric and optical applications using both simulations and experimental approaches. Density functional theory calculations were performed prior to experimental observations for predicting the trend of various parameters. The crystal structure analysis confirmed the presence of orthorhombic Ta2O5 phase in all compositions. The composition and morphology demonstrated the impurity free contents with uniform and crack-free surfaces. Thermoelectric analysis depicted a decrease in Seebeck coefficient from 3.66 to 1.91 µV/K and increase in the value of specific heat from 0.73 to 11.6 J/K•kg upon Cu incorporation in structure. The band gap was found to reduce from 2.61 eV to 1.38 eV with Cuinduced electronic states. The real epsilon and static refractive index increased from 3.75 to 4.57 and 1.93 to 2.11, respectively, with increment of Cu-content. The enhanced parameters focusing thermoelectric and optical response makes these compositions potential candidates for advanced optoelectronic applications.

We deal with the scattering phenomenon from an abruptly terminated asymmetrical slab waveguide for the case of transverse magnetic (TM) modes. The analysis uses both the integral equation method and the variational technique. The reflection coefficient of the dominant TM guided mode and the far-field radiation pattern are computed, and the discontinuity of the electric field distribution on the core-clad interface is exhibited. Numerical results are presented for several cases of abruptly ended waveguides, including the threelayer slab guide and the structure with variable profile of the refractive index.

The Butterworth low pass filter (LPF) with defected ground structure (DGS) is studied and simulated for WLAN Applications. Also an elliptical low pass filter with defected ground structure is simulated for WLAN Applications. Both the low pass filters design are simulated on FR4 substrate of relative permittivity is 4.3 and thickness 1.6mm. Calculation and comparison of the response of both low pass filters (LPF) with defected ground structure (DGS) was done. Results are simulated using computer simulation technology software (CST).

Several different compositions of tellurium-thallium oxide glasses were fabricated and tested for their Raman gain performance. The addition of PbO to the glass matrix increased the surface optical damage threshold by 60-230%. The maximum material Raman gain coefficient experimentally obtained was (58 ± 3) times higher than the peak Raman gain of a 3.18 mm thick Corning 7980-2F fused silica sample (∆ν = 13.2 THz). The highest peak in the Raman gain spectrum of the tellurium-thallium glass is attributed to the presence of TeO 3 and TeO 3+1 structural units with thallium ions in the vicinity at a frequency shift near 21.3 THz.

The Raman gain spectra of millimeter thick As 2 S 3 and As 24 S 38 Se 38 glasses and Ge (23 -x) Ga x Sb 7 S (70 -y) Se y with x = 0 and 5 and y = 0, 2, 5 have been measured using a direct nonlinear optics technique. The pump light originated from a picosecond Nd:YAG laser operating at 1064 nm and a tunable optical parametric generator and amplifier (OPG/OPA) was used as a source for the probe light. A peak material Raman gain coefficient of (155 ± 11) x 10 -13 m/W has been measured for the As 24 S 38 Se 38 glass. A reversible photodarkening effect which responds to picosecond pulses is also reported. Finally, surface optical damage threshold measurements were found to be less than 9 GW/cm 2 for the reported samples, values which are comparable to some TeO 2 -based glasses with lower nonlinearities.

Single shot diffraction imaging experiments via X-ray freeelectron lasers can generate as many as hundreds of thousands of diffraction patterns of scattering objects. Recovering the real space contrast of a scattering object from these patterns currently requires a reconstruction process with user guidance in a number of steps, introducing severe bottlenecks in data processing. We present a series of measures that replace user guidance with algorithms that reconstruct contrasts in an unsupervised fashion. We demonstrate the feasibility of automating the reconstruction process by generating hundreds of contrasts obtained from soot particle diffraction experiments.

Characterizing intense, focused x-ray free electron laser (FEL) pulses is crucial for their use in diffractive imaging. We describe how the distribution of average phase tilts and intensities on hard x-ray pulses with peak intensities of 10 21 W/m 2 can be retrieved from an ensemble of diffraction patterns produced by 70 nm-radius polystyrene spheres, in a manner that mimics wavefront sensors. Besides showing that an adaptive geometric correction may be necessary for diffraction data from randomly injected sample sources, our paper demonstrates the possibility of collecting statistics on structured pulses using only the diffraction patterns they generate and highlights the imperative to study its impact on single-particle diffractive imaging.

For ultrathin (~10 nm) nanocomposite films of plasmonic materials and semiconductors, the absorptance of normal incident light is typically limited to about 50%. However, through addition of a nonabsorbing spacer with a highly reflective backside to such films, close to 100% absorptance can be achieved at a targeted wavelength. Here, a simple analytic model useful in the long wavelength limit is presented. It shows that the spectral response can largely be characterized in terms of two wavelengths, associated with the absorber layer itself and the reflective support, respectively. These parameters influence both absorptance peak position and shape. The model is employed to optimize the system towards broadband solar energy conversion, with the spectrally integrated plasmon induced semiconductor absorptance as a figure of merit. Geometries optimized in this regard are then evaluated in full finite element calculations which demonstrate conversion efficiencies of up to 64% of the Shockley-Queisser limit. This is achieved using only the equivalence of about 10 nanometer composite material, comprising Ag and a thin film solar cell layer of a-Si, CuInSe 2 or the organic semiconductor MDMO-PPV. A potential for very resource efficient solar energy conversion based on plasmonics is thus demonstrated.

We investigate the interplay of shape changes and localized surface plasmons in small metal particles with the potential of a large enhancement of the Raman signal from the particles own vibrations. The framework is a geometrical one where we study the change in geometric factors during the vibrational movement. The resulting cross-section is found to be of a detectable order of magnitude however much smaller than the elastic cross-section.

We derive a simple rule to determine surface plasmon energies, based on the geometrical properties of the surface of the metal. We apply this concept to obtain the surface plasmon energies in wedges, corners and conical tips. The results presented here provide simple and straightforward rules to design the energy of surface plasmons in severals situations of experimental interest such as in plasmon wave guiding and in tip-enhanced spectroscopies.

Long-distance electron tunneling is a fundamental process which is involved in energy generation in cells. The tunneling occurs between the metal centers in the respiratory enzymes, typically over distances up to 20 or 30 Å. For such distances, the tunneling time-i.e., the time during which an electron passes through the body of the protein molecule from one metal center to another-is of the order of 10 fs. Here the process of electron tunneling in proteins is reviewed, and a possibility of experimental observation of real-time electron tunneling in a single protein molecule is discussed. 1 The article is published in the original.

Cervical cancer is a major public health challenge. Further mitigation of cervical cancer can greatly benefit from development of innovative and disruptive technologies for its rapid screening and early detection. The primary objective of this study is to contribute to this aim through large scale screening by development of Artificial Intelligence enabled Intelligent Systems as they can support human cancer experts in making more precise and timely diagnosis. Our current study is focused on development of a robust and interactive algorithm for analysis of colposcope-derived images analysis and a diagnostic tool/scale namely the OM- The Onco-Meter. This tool was trained and tested on 300 In-dian subjects/patients yielding 77% accuracy with a sensitivity of 83.56% and a specicity of 59.25%. OM-The Oncometer is capable of classifying cervigrams into cervical dysplasia, carcinoma in situ (CIS) and invasive cancer(IC). Pro- gramming language - R has been used to implement and compute ea...

The effect of absorbed gamma dose of the optical glass containing B 2 O 3 and BaO was examined at nine different dose levels, ranging between $1 and 36 kGy, in order to explain dose depth and penetration of light dependence. The specific light absorbance per unit area was examined to determine the changes in penetration ability of light photons into the irradiated glass structure due to the absorbed dose. Determining the increase in the absorbance of light photons is proposed as an approach to create the equivalent dose estimation. Examination of the penetration of light photon for the visible range presented an importance to evaluate absorbed dose depth in optical glass. The variations of light absorbance in the standardisation concept were controlled by the absorbed dose in a practical way. A calibration curve was determined depending on the variations of absorbed dose depth and optical density at 620 nm in the visible range. The effect of neutron and mixed gamma/neutron radiation in the tangential beam tube and the central thimble of the nuclear reactor, respectively were evaluated by means of equivalent gamma dose in order to explain the light absorbance in the irradiated glass.

Underwater visible light communication (UVLC) has become a promising wireless signaling approach towards the 5G and 5G beyond (5GB) wireless networks. The depth-dependent photophysical characteristics of water such as pressure, density, temperature, and salinity fluctuations lead to the changes in the refraction index and turbulence of water. The channel turbulence is a bottleneck for optical signaling in aqueous mediums, especially in oceans; it also causes malfunctions in transceivers because of signal bias or pointing error. The paper examines the performance of the reflecting node as part of underwater optical communication system operating in visible light. Based on the experimental data obtained in the Southern Indian Ocean, the outage outcomes and bit-error-rate (BER) performances are considered. The performance metrics for the proposed system model are obtained under weakturbulence channel conditions within Pulse-Amplitude Modulation (PAM) scheme. Additionally, the authors analytically present the closed-form expression for outage probability and a tight asymptotic expression for BER performance at high signal-to-noise (SNR) ratio that offers helpful insights into the influence of the medium on channel parameters and the system as a whole. The simulation results demonstrate operational capacity of the underwater communication system model.

Wildfires are one of the most devastating natural disasters in the world. This study proposes an innovative optical wildfire communication system (OWC) that leverages advanced optical technologies for wildfire monitoring and seamless communication towards the 5G and beyond (5GB) wireless networks. The multi-input-multi-output (MIMO) optical link among communication nodes is designed by gamma-gamma (GG) distribution under consideration of intensity modulation and direct-detection (IM/DD) following an on-off-keying (OOK) scheme. In this study, the performance metrics of the proposed MIMO link that enables unmanned aerial vehicles (UAVs) are analytically derived. The end-to-end (E2E) performance metrics and the novel closed-form expressions for the average BER (ABER) and outage probability (P out) are investigated for the proposed system models. Furthermore, the simulation results are obtained based on the real experimental data. The obtained results in this study are improved spatial resolution and accuracy, enabling the detection by communication of even small-scale wildfires at their inception stages. In the further perspective of this research, the development of the proposed system holds the potential to revolutionize wildfire prevention and control efforts, making a substantial impact on safeguarding ecosystems, communities, and economies from the devastating effects of fires.

This research endeavors to investigate the end-to-end performance metrics of a submerged AUV within the Single-Input-Multi-Output underwater visible-light communication (UVLC) system operating in moderate-to-strong turbulence channel conditions while accounting for pointing errors. In this study, the closed-form expressions of analytical work are derived by using the probability density function and cumulative density function with a specific focus on Gamma-Gamma distribution channel. The analytical framework is used to gain insight into the performance of developed UVLC system within the mixed waters. To validate the accuracy of the analytical approach under the Monte Carlo simulation methodology is used to improve the quality of service. The designed system aims to improve the reliability, practical applicability, and efficiency of the UVLC system, which is the paramount importance in emerging communication technologies.

Crystallization and phase separation are severe degradation mechanisms of photorefractive (PR) guest-host systems. Additionally, the response time of PR guest-host systems is in some cases limited by a large contribution of slow chromophore reorientation to the PR effect. The synthesis of fully functionalized systems with glass transition temperatures well above room temperature is a way to restrict these degradation mechanisms and to reduce the PR effect to a pure charge generation and transport phenomenon. We present novel, fully functionalized PR polymers based on polyester. Permanent poling of the systems is demonstrated and quantitatively investigated. The PR properties are measured by degenerate four-wave mixing and two-beam coupling experiments as a function of the external electric field and the degree of permanent poling. One of the systems shows response times of approximately 200 ms with ⌬n Ϸ 1 ϫ 10 Ϫ3 . To our knowledge, this work presents the first characterization of PR efficiencies for fully functionalized polymers as a function of the permanent Pockels coefficient (2) (Ϫ;, 0).

We present a computational study of the plasmonic response of a split nanoring dimer resonator which supports multiple plasmonic Fano-like resonances that arises by the coupling and interference of the dimer plasmon modes. For the generation of Fano resonances with large modulation depths, numerous configurations of the dimer resonator are analyzed which are observed to be highly dependent on the polarization of incident light. Moreover, the influence of dimension of the split nanoring structure on the spectral positions and intensities of the higher order Fano resonances are also investigated, and it is found that the asymmetric Fano line shapes can be flexibly tuned in the spectrum by varying various geometrical parameters. Such Fano resonators are also discovered to offer high values of figure of merit and contrast ratio due to which they are suitable for high-performance biological sensors.

The presence of plasmonic Fano-like resonances in the optical response of isolated and dimer metal-dielectricmetal nanostructures are investigated theoretically. The nanostructures are engineered in such a way to support multiple Fano-like resonances that are induced by the interference of bright and dark plasmon modes. It is found that the dimer resonators exhibit different types of Fano resonances for both the transverse and longitudinal polarizations unlike conventional nanodimers. Several configurations of the dimer Fano resonator are analyzed with special emphasis on the Fano spectral line shape. Breaking the symmetry of the dimer nanostructure in various directions control the asymmetric line shape and provides different kinds of unique Fano resonances. In certain cases, the Fano resonators exhibit multiple Fano resonances that are particularly significant for plasmon line shaping and can serve as platforms for multi-wavelength sensing applications.

We study an effect of quenching of antihydrogen quantum states near material surface in the gravitational field of the Earth by local charges randomly distributed along the mirror surface. The quenching mechanism reduces the quantum reflection probability because of additional atom-charge interaction and nonadiabatic transitions to excited gravitational states. Our approach is suitable for accounting for quenching caused by any kind of additional interaction with the characteristic range much smaller than the typical gravitational state wave-length.

Laser cooled and trapped cesium atoms have been used as a non-linear medium in a nearly resonant cavity. A study of the semi-classical dynamics of the system was performed, showing bistability and instabilities. In the quantum domain, squeezing in a probe beam having interacted with this system was demonstrated.

Resonances of simple tuning circuits up to 1 THz coupled to SIS tunnel junctions were obtained by means of FTS measurements and compared with calculations based on the Mattis-Bardeen theory. We developed a new sort of devices for frequencies above 700 GHz using gold instead of Nb for the if-parts. First measurements of the video and heterodyne response of all-Nb SIS receivers have been made at frequencies between 720 and 890 GHz. We measured a possible heterodyne response of 1.1 dB due to a hot/cold load at 830 GHz. The video response of the unpumped junction was 0.3 dB due to the hot/cold load.

A new simple method to measure the influence on the laser beam propagation by a turbid medium is proposed. This measurement is based on the inscription of a surface relief grating (SRG) on an azopolymer thin film. The grating obtained with a single laser beam after propagation into a turbulent medium is perturbed and directly analysed by a CCD camera through its diffraction pattern. Latter, by scanning the surface pattern with an AFM, the inscribed SRG is analysed with the Radon transform. This method has the advantage of using a single beam to remotely inscribe a grating detecting perturbations during the beam path. A method to evaluate the refractive index constant structure is developed.

Background: Diabetes mellitus (DM) is associated with microvascular complications, such as diabetic retinopathy (DR). DR is one of the main causes of visual loss in individuals aged 20-64 years old. This study aims to investigate the independent associations between the stage of DR and a variety of possible risk factors, including years since DM diagnosis, HbA 1c levels, the coexistence of hypertension, age and gender.

Turbidity provides one of many challenges to underwater robotic vision. This paper studies and presents a method for extracting high quality scene geometry in short range underwater applications that is robust to high turbidity conditions. The hardware of the vision system used only requires two cameras acting as a stereo pair and a projector and can be assembled with off the shelf components. Accuracy of the reconstruction in turbid conditions is improved through partial illumination of the scene by projecting individual stripes across the environment. Using individual stripes allows for the amount of projected light to decrease, reducing the amount of backscattered light. In addition, the stripe of light provides a distinct feature in the image which additionally improves the stereo reconstruction. Our experiments show that the images taken with individual stripes allow for easier stereo matching, resulting in reconstructions with greater coverage and smaller RMS error in highly t...

We analyze whether the numerical-scale relation h 2 = e 0 t 0 (1) interpreted as an approximate proportionality between the square of Planck's constant and the product of a hypothetical fundamental energy quantum e 0 ("joulino") and a fundamental time quantum t 0 ("secondino"), can be ruled out by current experiments. Treated numerically rather than dimensionally, this relation links characteristic magnitudes of action, energy, and time in a discrete-graph picture of spacetime. We show that for e 0 ≲ 10-37-10-38 J and t 0 ≲ 10-29-10-30 s, no existing laboratory or astrophysical data contradict Eq. (1). Hence, the relation remains experimentally untested but not excluded.

Surprising things happen when information processing is generalised to quantum, rather than classical systems. This paper reviews some recent results about the nature of information stored in quantum bits (qbits). An'informational equivalence'between'sameness' and'oppositeness' in classical information fails to hold when those notions are generalised to quantum information. This has consequences for the sharing and flow of information within quantum networks.

The influence of emission parameters in low-level-light therapy on cellular responses is not yet fully understood. This study assessed the impact of various light delivery modes on collagen production in human primary fibroblast cultured in monolayers after three treatments with red light-emitting diode illumination ͑630 nm, 8 J/cm 2 ͒. Human type I collagen was measured in cell culture supernatants with procollagen type I C-peptide enzyme immunoassay. Results demonstrated that, 72 h post-baseline, specific microsecond pulsing patterns had a more favorable impact on the ability of fibroblasts to produce collagen de novo than comparative conditions of continuous wave, pulsed 50% duty cycle, and millisecond pulsing domains. The cascade of events leading to collagen production by red illumination may be explained by the photodissociation of nitric oxide from cytochrome c oxidase. Short and intermittent light delivery might enhance this cellular event.

A detailed theoretical analysis of the hybrid surface plasmon mode generation and propagation at a chiral graphene metal (CGM) interface for a cylindrical structure is presented. The conductivity of graphene is modeled using the Kubo formalism and the dispersion relation for the hybrid surface waves is computed on the basis of the Kubo formalism and impedance matching boundary conditions. The hybrid mode consisting of lower and upper plasmon modes is witnessed due to the presence of the chiral medium. The frequency band gap between the lower and upper plasmon modes is found to be sensitive and tunable with respect to the chiral strength, radial distance of the waveguide, and chemical potential of graphene. The propagation length and effective refractive index can also be modulated by varying the chiral strength and chemical potential. For very high values of chirality and biasing voltage, the Goos-Hänchen effect is observed at the CGM interface. The cutoff values of chiral strength as a function of normalized frequency make the proposed structure applicable for chiroptical and chemical sensing and enantiomeric detection in the THz frequency regime. Key Word: Surface Plasmon Polaritons, Chiral, Graphene, Waveguide 1 2 in Eq. 15). The graph exhibits the sensitive behavior of plasmon modes toward optical and chemical changes in the chiral medium. The cutoff chiral values follow a linear and distinct relation for variation in refractive index values within a narrow frequency range. The frequency-dependent cutoff values for chiral media having different refractive indices enrich the sensitivity of the proposed design toward chiroptical and chemical sensing.

This letter proposes and experimentally demonstrates a simple scheme for generating 40-GBaud carriersuppressed return-to-zero differential quadrature phase shift keying (CSRZ-DQPSK) modulation signals with tunable pulsewidths using two dual-parallel Mach-Zehnder modulators (DPMZMs). The duty cycle of the generated 40-GHz CSRZ-DQPSK pulse train is continuously tuned from 31% to 62%, with the full-width at half-maximum tuned from 7.8 to 15.5 ps, by electrically tuning the delay between the two sine-clock signals in one of the DPMZMs. Error-free performance is achieved after 320-km transmission.