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Graphene, a two-dimensional nanomaterial, possess unique photoelectric properties that have potential application in designing optoelectronic devices. The tunable optical absorption is one of the most exciting properties that can be used to improve the performance of silicon modulators. However, the weak light–matter interaction caused by the size mismatch between the optical mode fields and graphene makes the graphene-on-silicon modulator (GOSM) has large footprint and high energy consumption, limiting the enhancement of modulation efficiency. Here, we propose a broadband GOSM with orthogonal hybrid plasmonic waveguides (HPWs) at near-infrared wavelengths. The orthogonal HPWs are designed to compress the interaction region of optical fields and enhance the light-graphene interaction. The results show that the GOSM has a modulation depth of 26.20 dB/μm, a footprint of 0.33 μm2, a 3 dB modulation bandwidth of 462.77 GHz, and energy consumption of 2.82 fJ/bit at 1.55 μm. Even working at a broad wavelength band ranging from 1.3 to 2 μm, the GOSM also has a modulation depth of over 8.58 dB/μm and energy consumption of below 4.97 fJ/bit. It is anticipated that with the excellent modulation performance, this GOSM may have great potential in broadband integrated modulators, on-chip optical communications and interconnects, etc.

In tunable diode laser absorption spectroscopy (TDLAS), the wavelength modulation spectroscopy (WMS) is widely employed. However, when measuring the gas concentration with the second harmonic signal, errors will occur and the inversion accuracy will be reduced, because the change of the modulation depth will lead to the change of the second harmonic peak value, and the value of modulation depth cannot be calculated directly in the absence of gas component. To improve the inversion accuracy of WMS technology, we calibrate the modulation depth and take it as a parameter to the concentration inversion model. In this article, the relationship between the modulation depth and the valley spacing of the second harmonic is first derived, and used to calibrate the modulation depth in the measurement; then, an improved concentration inversion model is established by adding the calibrated modulation depth to the traditional model. Through simulations in Simulink and gas concentration measurement experiments with carbon monoxide (CO), the effectiveness of modulation depth calibration using valley spacing and the accuracy of the improved model are verified. The gas concentration measurement error of the improved model (relative error -5) is reduced by nearly one order of magnitude compared to the traditional model without calibration of the modulation depth (relative error -4). The correction method of modulation depth in this article does not need the priori information of the gas component, and the improved model produces a better determination of gas concentration immune to the variations of modulation depth, which is important for field measurements especially those with large environmental variations.

Background: The temporal envelope (ENV) plays a vital role in conveying inter-aural time difference (ITD) in many clinical populations. However, the presence of background noise and electronic features, such as compression, reduces the modulation depth of ENV to a different degree in both ears. The effect of ENV modulation depth differences between the ears on ITD thresholds is unknown; therefore, this was the aim of the current study’s investigation. Methods: Six normally hearing young adults (age range 20-30 years) participated in the current study. Six vowel-consonant-vowel (VCV) (/aka/, /aga/, /apa/, /aba/, /ata/, /ada/) tokens were used as the probe stimuli. ENV depth of VCV tokens was smeared by 0%, 29%, and 50%, which results in 100%, 71%, and 50% of the original modulation depth. ITD thresholds were estimated as a function of the difference in temporal ENV depth between the ears, wherein in one ear the modulation depth was retained at 100% and in the other ear, the modulation depth was changed to 100%, 71%, and 50%. Results: Repeated measures of ANOVA revealed a significant main effect of interaural modulation depth differences on the ITD threshold (F(2,10)= 9.04, p= 0.006). ITD thresholds increased with an increase in the inter-aural modulation depth difference. Conclusion: Inter-aural ENV depth is critical for ITD perception.

Structured illumination microscopy (SIM) is a promising super-resolution technique for imaging subcellular structures and dynamics due to its compatibility with most commonly used fluorescent labeling methods. Structured illumination can be obtained by either laser interference or projection of fringe patterns. Here, we proposed a fringe projector composed of a compact multi-wavelength LEDs module and a digital micromirror device (DMD) which can be directly attached to most commercial inverted fluorescent microscopes and update it into a SIM system. The effects of the period and duty cycle of fringe patterns on the modulation depth of the structured light field were studied. With the optimized fringe pattern, [Formula: see text] resolution improvement could be obtained with high-end oil objectives. Multicolor imaging and dynamics of subcellular organelles in live cells were also demonstrated. Our method provides a low-cost solution for SIM setup to expand its wide range of applications to most research labs in the field of life science and medicine.

International audience; The increasing use of light emitting diodes in traffic lights offer excellent opportunities for implementation of visible light communications (VLC) based wireless technology as part of intelligent transport systems in smart environments. In this paper, we experimentally demonstrate vehicle to infrastructure (V2I) communications based on the VLC technology using a real traffic light and a camera over a link span of up to 80 m. We show a reduction in the modulation depth of the signal from 100% to 50% in order to track the light source when sending '0' symbols. Also presented is the effect of operating the camera in the focused and defocused modes. The results show transmission success rates of 100% and 90% over link spans of 70 m and 80 m, respectively under specific test conditions.

ResumenEste artículo presenta un estudio comparativo de técnicas de generación de señales para el transporte de información en sistemas de Radio sobre Fibra (RoF) usando técnicas de combinación óptica. En estos sistemas las portadoras de radiofrecuencia se transportan como subportadoras de canal óptico sobre un enlace en conexiones punto-punto o punto-multipunto. Este estudio se centra en tres diferentes técnicas de generación: brazo doble, generación en paralelo y generación serial. Para cada una de ellas se define un modelo analítico con el fin de describir los elementos, la configuración y los procesos involucrados en la generación de señales RoF. Posteriormente se modelan las funciones de campo eléctrico obtenidas con el fin de evaluar la calidad de las señales generadas en función de los índices de modulación establecidos. Los resultados obtenidos muestran que los índices de modulación para los esquemas de brazo doble y serial presentan una fuerte dependencia entre sí, mientras la configuración de generación en paralelo permite una mayor flexibilidad en el establecimiento de los índices de modulación. Para cada esquema se obtiene el valor óptimo de índices de modulación a fin de garantizar una buena calidad para ambas señales a la salida del transmisor RoF.AbstractThis paper presents a comparative study of the signal generation techniques for the transport of information in Radio over Fiber (RoF) systems by using optical combination techniques. In these systems, the radio frequency carriers are conveyed as optical subcarriers over a link in a point-to-point or point-to-multipoint connectivity paradigm. This study is focused on three different generation techniques: double arm, parallel and serial generation. An analytical model to describe the elements, the configuration and the processes involved in the RoF signal generation is defined for each one of them. Subsequently, a modeling of the obtained electrical field functions allows assessing the quality of the generated signals based on the modulation depth. Results show that while there is a trade-off between the modulation depths of both signals for the double arm and serial configuration, the parallel technique relaxes the establishment of different modulation depths. An optimum configuration that guarantees a good quality for the generated signals is found for each generation technique.

This paper presents the first printed organic 13-MHz RFID on flexible substrate. The proposed solution includes a planar near field antenna bonded to an RFID tag, which is printed on flexible foil using an organic complementary TFT technology. Thanks to an active envelope detector, ASK modulation with modulation depth as low as 20% can be adopted to increase the available input power for the rectifier. The RFID functionality is demonstrated at the internally generated supply voltage of 24 V, for a reading range of 2-5 cm and a bit-rate up to 50 bit/s. With more than 250 transistors on the same foil, this work represents the most complex circuit ever published in a printed organic complementary TFT technology.

Graphene has emerged as a promising optoelectronic material because its optical properties can be rapidly and dramatically changed using electric gating Graphene's weak optical response especially in the infrared part of the spectrum, remains the key challenge to developing practical graphene-based optical devices such as modulators, infrared detectors, and tunable reflect-arrays Here it is experimentally and theoretically demonstrated that a plasmonic metasurface with two Fano resonances can dramatically enhance the interaction of infrared light with single layer graphene: Graphene's plasmonic response in the Pauli blocking regime is shown to cause strong spectral shifts of the Fano resonances without inducing additional nonradiative losses. It is shown that such electrically controllable spectral shift, combined with the narrow spectral width of the metasurface's Fano resonances, enables reflectivity modulation by nearly an order of magnitude. We also demonstrate that metasurface-based enhancement of the interaction between graphene and infrared light can be utilized to extract one of the key optical parameters of graphene: the free carrier scattering rate. Numerical simulations demonstrate the,possibility of strong active modulation of the phase of the reflected light while keeping the reflectivity nearly constant, thereby paving the way to tunable infrared lenses and beam steering devices based on electrically controlled graphene integrated with resonant metasurfaces.

This study sought to quantify the temporal properties of the human visual system by measuring forced-choice reaction times for discriminating the drift direction of first-order motion (luminance-modulated noise) and a variety of second-order motion patterns (modulations of either the contrast, polarity, orientation or spatial length of a noise carrier) over a range of stimulus modulation depths. In general, reaction times for all types of second-order motion were slower than those for first-order motion. Specifically, reaction times were similar for modulations of image contrast, polarity and orientation but were markedly slower for modulations of spatial length. There was also a tendency for reaction times to decrease as stimulus modulation depth increased. The rate of this decrease was shallowest for first-order, luminance-defined patterns. For second-order motion reaction times decreased at a similar rate for contrast, polarity and orientation but this decrease was steepest for spatial length. However, when equated in terms of visibility (multiples of direction-discrimination threshold), the rate at which reaction times decreased as modulation depth increased became comparable for patterns defined by luminance, contrast, polarity and orientation. For patterns defined by spatial length, performance could not be equated in this manner. These findings demonstrate that the time taken to encode the direction of each pattern is not an invariant response metric. The results are consistent with psychophysical and electrophysiological evidence for longer response latencies for second-order motion and may reflect the additional processing stages (e.g. filter–rectify–filter) required for its extraction.

We demonstrate a terahertz intensity modulator using a graphene supercapacitor which consists of two large-area graphene electrodes and an electrolyte medium. The mutual electrolyte gating between the graphene electrodes provides very efficient electrostatic doping with Fermi energies of 1 eV and a charge density of 8 x 10(13) cm(-2). We show that the graphene supercapacitor yields more than 50% modulation between 0.1 and 1.4 THz with operation voltages less than 3 V. The low insertion losses, high modulation depth over a broad spectrum, and the simplicity of the device structure are the key attributes of graphene supercapacitors for THz applications. (C) 2015 Optical Society of America

Power modulated visible lasers are interesting for a number of applications within areas such as laser displays and medical laser treatments. In this paper, we present a system for modulating the second-harmonic light generated by single-pass frequency doubling of a distributed feedback (DFB) master oscillator power amplifier (MOPA) laser diode with separate electrical contacts for the MO and the PA. A modulation depth in excess of 97% from 0.1 Hz to 10 kHz is demonstrated. This is done by wavelength tuning of the laser diode using only a 40 mA adjustment of the current through the MO. The bandwidth of the modulation is limited by the electronics. This method has the potential to decrease the size as well as cost of modulated visible lasers. The achievable optical powers will increase as DFB MOPAs are further developed. (C) 2017 Optical Society of America

The diffractive efficiency of Liquid Crystal on Silicon (LCoS) displays can be greatly diminished by the appearance of temporal phase fluctuations in the reflected beam, depolarization effects and also because of phase modulation depths smaller than 2π. In order to maximize the efficiency of the Diffractive Optical Elements (DOEs) implemented in the LCoS device, the Minimum Euclidean Distance principle can be applied. However, not all the diffractive elements can be corrected in the same way due to the anamorphic and spatial frequency dependent phenomenon, which is related to the LCoS response, largely depending on the period and the spatial orientation of the generated DOE. Experimental evidence for the anamorphic and spatial frequency dependent phenomenon is provided in this paper, as well as a comparative study between the LCoS display response for binary gratings of different periods. Fil: Lobato, L.. Universitat Autònoma de Barcelona; España Fil: Lizana, A.. Universitat Autònoma de Barcelona; España Fil: Marquez, A.. Universidad de Alicante; España Fil: Moreno, I.. Universidad de Miguel Hernández; España Fil: Iemmi, Claudio César. Universidad de Buenos Aires; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria; Argentina Fil: Campos, J.. Universitat Autònoma de Barcelona; España Fil: Yzuel, María J.. Universitat Autònoma de Barcelona; España

Date of Conference: 21–24 June 2010 Conference name: Nonlinear Photonics 2010 We report the experimental generation of two-soliton molecules in an ytterbium-doped fiber laser. These molecules exhibit an independently evolving phase and are characterized by a regular spectral modulation pattern with a modulation depth of 80%. © 2010 Optical Society of America.

We report fast modulation (>30 GHz) in a SOI resonant cavity using integrated Bragg mirrors and a gate-all-around transistor as active element. Modulation depth >90% can be obtained in 12.5 μm long devices.