Value Of Modulation Depth Research Articles

Realization of all-optical logic gates using MIM waveguides and a rectangular ring resonator

In this study, all-optical OR, exclusive OR (XOR), NOR, XNOR, AND, NAND, and NOT logic gates using metal-insulator-metal (MIM) waveguides with a rectangular ring resonator are designed and analyzed. The structure has a silver plate with three input waveguides, one output waveguide, and a rectangular ring resonator. One of the input ports is used as a control port. The finite-difference time-domain (FDTD) method is utilized to obtain the optical spectrum of the proposed structures. To realize all-optical logic gate properties of the designed structures, optical signals with the same phase or different phases are passed through the waveguides. Transmission spectrum (T), contrast ratio (CR), and modulation depth (MD) parameters are obtained to determine the performances of all-optical logic gates. To determine the logic 1 (ON) and logic 0 (OFF) states of the output ports, the threshold transmission value is accepted as 0.23 for all-optical logic gates. For the proposed designs, the highest transmission, contrast ratio, and modulation depth values are 217%, 6.75 dB, and 100%, respectively. The structure also supports a data rate of 24 Tb/s. The designed optical logic gates have valuable features for developing high-performance optical devices.

3985Utilizing EllipticalRingIMI-Plasmonic Waveguides, Nanomaterials in Nanophotonic Structure for All-Optical 2 × 1 Demultiplexer

In many industries, particularly electronics, photonic devices are indispensable. However, the diffraction limit and miniaturization are the two problems that have hampered the development of photonics devices. These problems are resolved by plasmonic devices, which enable nanophononics and nanodevices. One of the primary all-optical demultiplexer components utilized in an all-optical Athematic Logic Unit (ALU), which is regarded as the basic building block for all-optical computers, is a plasmonic demultiplexerThis paper provides a new design for an elliptical ring insulator-metal-insulator (IMI) plasmonic waveguide-based all-optical demultiplexer (Demux). The suggested device has a small footprint (300 nm × 250 nm) and works at a 1550 nm wavelength. Demux has a 0.5 transmission threshold between logic zero and logic one states. Transmission (T), extinction ratio (contrast ratio (CR)), modulation depth (MD), and insertion loss (IL) are the four metrics that best explain the performance of the plasmonic Demux. The suggested structural dimensions are outstanding and optimal based on the values of MD for Demux which is (95.87%). The device's maximum transmission efficiency is 56.84%. The suggested plasmonic Demux structure makes a substantial contribution to all-optical signal processing Nano-circuits and nano-photonics integrated circuits. Using COMSOL Multiphysics, wesimulate the proposed plasmonic Demux using the Finite Element Method (FEM).

Design of an IMI optical 2 × 4 decoder circuit based on square disk resonators.

This paper presents the design of a 2×4 decoder that was developed by using the finite element method (FEM) in conjunction with the COMSOL version 5.5 software. Insulator-metal-insulator (IMI) waveguides with four substructures were used in the fabrication of the plasmonic decoder. Gold is used as a conducting material. Thisis a challenge for us, while Teflon is used as a dielectric material in the fabrication process. The dimensions of thispart are 1090nm by 400nm. At an operating wavelength of 1550nm, the transmission threshold (T t h r e s h o l d ) of this scheme has been determined to be 10%. In order to assess the effectiveness of the plasmonic decoder, it is recommended that the modulation depth (MD), contrast ratio (CR), and insertion loss (IL) parameters be carried out. Both the highest values of CR and MD are 12.33 decibels, and the maximum value of MD is 99.96%. It is because of these qualities that this work is distinguished from earlier works.

A Dual-Polarization Scattering Probe for Modulated Scatterer Technique Measurements

A scattering probe for use in the modulated scatterer technique (MST) measurements was proposed. The proposed probe has dual-polarization capability and a high modulation depth (MD) for both polarizations. The high MD values are made possible by loading shorted transmission lines (STLs) at the center of dipoles, such that the integration of the dipole currents vanishes, resulting in an electrically invisible state for broadside observations. For the actual implementation of the dual-polarization MST probes, the scattering geometry on an FR-4 substrate was considered and the effects of the substrates, particularly in the invisible states, were studied. The dual-polarization scattering probes (DPSPs) were implemented on FR-4 substrates using 4 PIN diode switches, low-frequency blocking capacitors, and biasing structures to provide bias voltages to the PIN diode switches. The biasing structures were implemented using inductors and resistive wires. The locations of the blocking capacitors were offset from the ends of the dipoles to compensate for the nonideal characteristics of the PIN diodes and other parts. The performance of the implemented DPSPs was measured and demonstrated to have high MDs for both polarizations over a wide bandwidth indicating that the proposed probe may increase the sensitivity of the MST system.

Tunable modulators based on single and double graphene-based resonator systems in the mid-infrared spectrum

Tunable modulators based on single and double graphene-based resonator systems are studied numerically in the mid-infrared spectrum. Employing 3D-FDTD (3D Finite-Difference Time-Domain) simulations, multiple factors are discussed, including the geometrical parameters on the resonance wavelengths of single resonator systems, modulation depth calculations, and especially negative, positive and linear amplitude modulation are discussed for first time in current research. Furthermore, plasmon-induced transparency (PIT) windows are revealed for double resonator systems, and modulation depth as well as the negative and positive amplitude modulation are examined for two different wavelengths. The maximum value of modulation depth is 74 %, and linear modulation depth is 65 %. Moreover, for double resonator systems, a slow light capability is realized. The maximum tg equals 0.2 ps which coincides with 60 µm of light traveling in a vacuum.

Double toroidal switches based on the different multipole responses in the all-dielectric metasurface

We design and numerically investigate an all-dielectric metasurface, constructed of four open resonant rings described by the group Cs and located with a cross-shaped resonator between them, that realizes double toroidal switching, in which switching from a toroidal dipole to a quadrupole response occurs in two separate frequency regimes. It is shown that the toroidal dipole can be dynamically switched on, whereas the pronounced toroidal quadrupole can be switched off simultaneously at orthogonal orientations from same metasurface, and vice versa, through changing the polarization of the incident light. The maximum value of modulation depth for the toroidal dipole and quadrupole responses reached 76% and 83%, respectively. Active switching of a toroidal dipole into a quadrupole has potential applications in designing efficient filters and modulators.

Dark hollow lasers may be better candidates for holography

Gaussian laser beams have been very successful in various fields including holography where two lasers with frequency difference have been used, but good quality holograms could be produced only for small frequency detuning. The present proposal proves that the Dark-hollow laser beams (DHBs) may be better than the Gaussian lasers for larger frequency difference. DHBs with smaller dark spot generate new regions of frequency detuning with very significant value of modulation depth. It also enables the flexibility of both fixing the pulse duration and varying the frequency difference or vice-versa for obtaining the best possible quality holograms.

Improvement of Concentration Inversion Model Based on Second Harmonic Valley Spacing in Wavelength Modulation Spectroscopy

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 $5.468\times 10^{-5}$ ) is reduced by nearly one order of magnitude compared to the traditional model without calibration of the modulation depth (relative error $2.178\times 10^{-4}$ ). 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.

Large optical nonlinearity of ITO/Ag/ITO sandwiches based on Z-scan measurement.

Indium tin oxide (ITO)-based sandwich structures with the insertion of silver (ITO/Ag/ITO) show large nonlinear optical enhancement of both nonlinear refraction and saturable absorption. Here optical nonlinearity is measured using a Z-scan experiment with a 1310nm pulsed laser at normal incidence. The nonlinear refractive index (n2=15.43×10-16 m2/W) for an ITO/Ag/ITO sandwich with a 14nm silver interlayer and the nonlinear absorption coefficient (β=-648×10-11 m/W) for an ITO/Ag/ITO sandwich with a 10nm silver interlayer are about 18 and 16 times greater than that of a single-layer ITO, respectively. Meanwhile, a large figure of merit and modulation depth values hinted that ITO/Ag/ITO sandwiches are promising saturable absorber materials to switch continuous laser waves into laser pulses. These novel nonlinear optical properties make ITO/Ag/ITO sandwiches a promising candidate for all-optical modulation devices at optical communication wavelengths.

Transition metal dichalcogenide (WS2 and MoS2) saturable absorbers for Q-switched Er-doped fiber lasers

This report demonstrates a stable Q-switched Er-doped fiber laser with MoS2 (WS2)-based saturable absorber (SA) in the net normal dispersion regime. The SA is obtained by mixing MoS2 (WS2) nanosheets with polyvinyl alcohol (PVA) into polystyrene cells, and then evaporating them to form MoS2 (WS2)/PVA film. The modulation depth values for MoS2/PVA and WS2/PVA are measured to be 2.7% and 2.1% respectively. Employing the MoS2 (WS2)/PVA film in the Er-doped fiber laser cavity, stable Q-switching operation is achieved with central wavelength of 1560 nm. The shortest pulse durations of the two Q-switched fiber lasers are, respectively, 3.97 and 3.71 µs, and their maximum single pulse energies are measured to be 131.52 and 126.96 nJ. The experimental results clearly show that MoS2 (WS2) is a promising nonlinear material, and that improvements in Q-switching performance due to two SAs in the net normal dispersion regime might be helpful in the design of fiber lasers.

A new autostabilization mechanism in the Bennet doubler circuit-based electrostatic vibrational energy harvester

In this work, the theoretical and experimental study of the electric circuit is carried out for the electrostatic microgenerators based on the Bennet doubler with a power source in a variable capacitor branch. It is established that the circuit is able to operate at different capacitance modulation depth values. For the circuit with one variable capacitor, when the maximal-to-minimal capacitance ratio is less than 2, one can observe a saturation of the storage capacitor voltage (voltage autostabilization process). The equation for the saturation voltage evaluation is derived. As it is revealed for a maximal-to-minimal capacitance ratio more than 1.5, the saturation voltage is higher than power source voltage V0. When the maximal-to-minimal capacitance ratio is greater than 2, one can observe a continuous growth of the capacitor voltages as for the basic Bennet doubler conditioning circuit. A similar change of the regimes in the same circuit, but with two variable capacitors, takes place when a maximal-to-minimal capacitance ratio is about 1.618. The employment of the considered Bennet doubler conditioning circuit enables solving two main problems: operation only for a capacitance modulation depth above 2 (1.618) and the uncontrolled capacitors voltages growth. The circuit under study can be also used for electret microgenerators and for microgenerators based on using electrodes with materials having different work functions.

Maximum modulation of plasmon-guided modes by graphene gating

The potential of graphene in plasmonic electro-optical waveguide modulators has been investigated in detail by finite-element method modelling of various widely used plasmonic waveguiding configurations. We estimated the maximum possible modulation depth values one can achieve with plasmonic devices operating at telecom wavelengths and exploiting the optical Pauli blocking effect in graphene. Conclusions and guidelines for optimization of modulation/intrinsic loss trade-off have been provided and generalized for any graphene-based plasmonic waveguide modulators, which should help in consideration and design of novel active-plasmonic devices.

Supercontinuum and rogue soliton generation by induced modulational instability in photonic crystal fibre

We present an approach that enables active control of supercontinuum (SC) and rogue soliton (RS) generation through the modulation of a 500 fs input pulse by numerical simulations. The induced modulational instability contributes to the initial comb-like SC generation, which is fundamentally different from SC initiated by high-order soliton fission. The output spectrum shows great dependence on modulation frequencies and depths. It is interesting that we can manipulate the RS generation by adjusting the modulation parameters. And we also demonstrate the conditions which can be beneficial to RS generation: (i) very weak or large values of modulation depth; (ii) seeding in the vicinity of the peak of the modulational instability gain spectrum. Although RS degrades the smoothness of the SC, it is of great significance in the generation of tailored SC.

Analysis of lorentzian line shape function broadened by non-sinusoidal wavelength modulation

In the present work, the Fourier analysis of Lorentzian line shape broadened by non-sinusoidal wavelength modulation was investigated, in which the third order and above harmonic items were ignored. The analytical expression of n-order Fourier coefficient was brought out, where a variable K named harmonic distortion to characterize the ratio of the second harmonic to the first harmonic was introduced. Numerical simulations based on the cases of K > 0.01 and K < 0.01 were carried out, and the result shows: non-sinusoidal modulation has little effect compared with the sinusoidal modulation when K value is less than 0.01, however, if K value is about 0.1 or higher, the center of the Fourier amplitude curve would deviate from the origin of coordinates. With the increase in the harmonic distortion, the deviation of the curve grows, and high order harmonics are more sensitive to the non-sinusoidal modulation compared with the low order harmonics. In addition, when harmonic distortion cannot be ignored, for example K > 0.01, the effect of different depths of modulation on the odd and even order harmonic amplitude curve is significant. And the numerical simulation shows there exists an optimum value of modulation depth which could minimize the impact of the harmonic distortion, and both large K value and small K value would cause a great error. The conclusion of this work could be applied in error analysis of wavelength modulation spectroscopy system And the results are helpful to deepening understanding of WMS and would be the important reference for some kind of frequency stabilization technology in laser instrument.

Cascaded Modulation Scheme and Its Application to Optical Multi-Channel Signal Transmission Systems

This paper starts by describing the advantages of cascaded modulation, i.e., using multiple concatenated external modulators to modulate CW (Continuous Wave) light. Next, the paper examines computer simulations of the resulting modulated light waveform shapes and intermodulation distortion values to elucidate the basic modulation characteristics of a cascaded modulation scheme. Examples of applying cascaded modulation to a multi-channel optical signal transmission system are shown, and the characteristics are clarified by optical transmission experiments. For example, the dependency of the signal quality on the modulation depth values of each external modulator is clarified. Moreover, experiments show that cascaded modulation permits the remote insertion of local broadcast programs into wide area broadcast programs. Last, the paper shows that cascaded modulation offers better modulation properties than the conventional single modulation approach.

Human subjective response to steering wheel vibration caused by diesel engine idle

This study investigated the human subjective response to steering wheel vibration of the type caused by a four-cylinder diesel engine idle in passenger cars. Vibrotactile perception was assessed using sinusoidal amplitude-modulated vibratory stimuli of constant energy level (r.m.s. acceleration, 0.41 m/s2) having a carrier frequency of 26 Hz (i.e. engine firing frequency) and modulation frequency of 6.5 Hz (half-order engine harmonic). Evaluations of seven levels of modulation depth parameter m(0.0, 0.1, 0.2, 0.4, 0.6, 0.8, and 1.0) were performed in order to define the growth function of human perceived disturbance as a function of amplitude modulation depth. Two semantic descriptors were used (unpleasantness and roughness) and two test methods (the Thurstone paired-comparison method and the Borg CR-10 direct evaluation scale) for a total of four tests. Each test was performed using an independent group of 25 individuals. The results suggest that there is a critical value of modulation depth m = 0.2 below which human subjects do not perceive differences in amplitude modulation and above which the stimulus-response relationship increases monotonically with a power function. The Stevens power exponents suggest that the perceived unpleasantness is non-linearly dependent on modulation depth m with an exponent greater than 1 and that the perceived roughness is dependent with an exponent close to unity.

Spectrum investigation of pulse-interval modulation

An expression for the frequency spectrum of pulse-interval modulation (PIM) is derived using the pseudo-static approach. The theoretical results predict the presence of modulating frequency harmonics caused by higher values of modulation depth. Experimental results obtained from a hardware model confirm the validity of the proposed method of analysis.