Resonant Transmission Peak Research Articles

Enhanced optical transmission by V-shaped nanoslit in metal film

In this paper, we reveal that the enhanced transmission through a perforated metal film can be further boosted up by a V-shaped nanoslit, which consists of two connected oblique slits. The maximum transmission at resonance can be enhanced significantly by 71.5% in comparison with the corresponding vertical slit with the same exit width. The value and position of transmission resonance peak strongly depend on the apex angle of the V-shaped slit. The optimum apex angle, at which the transmission is maximal, is sensitive to the slit width. Such phenomena can be well explained by a concrete picture in which the incident wave drives free electrons on the slit walls. Moreover, we also simply analyze the splitting of the transmission peak in the symmetry broken V-shaped slit, originating from the resonances of different parts of the V-shaped slit. We expect that our findings will be used to design the nanoscale light sources based on the metal nanoslit structures.

Ballistic thermal transport in a cylindrical quantum structure modulated with double quantum dots

Ballistic thermal transport properties in a cylindrical quantum structure modulated with double quantum dots (DQDs) are investigated. Results show that the transmission coefficients exhibit the irregular oscillation. Some resonant transmission peaks and stop-frequency gaps can be observed, and the number and positions of these peaks and gaps are sensitive to the sizes of DQDs. With increasing the temperature, the thermal conductance undergoes a transition from the decrease to increase, and can be efficiently tuned by modulating the radius, length of DQDs as well as the interval between DQDs. In addition, at low temperatures, the enhancement of the thermal conductance can be also observed in this case. Some similarities and differences between the cylindrical and rectangular structures are identified.

Optical bistability in a photonic crystal with a liquid-crystal defect

We investigate experimentally the nonlinear transmission of a photonic crystal with a nematic liquid-crystal defect upon reorientation of the director in a field of cw laser radiation propagating at a certain angle to the sample. At different detunings, we observed the regimes of bistability, differential gain, and optical limiting. The resonance transmission peaks were detuned from the laser radiation wavelength by changing the angle of light incidence onto the sample. The value of nematic nonlinear constant n 2 determined from the experimental data is in good agreement with the theoretical estimate.

One-dimensional spin-orbit interferometer

We demonstrate that the combination of an external magnetic field and the intrinsic spin-orbit interaction results in nonadiabatic precession of the electron spin after transmission through a quantum point contact (QPC). We suggest that this precession may be observed in a device consisting of two QPCs situated in series. The pattern of resonant peaks in the transmission is strongly influenced by the non-Abelian phase resulting from this precession. Moreover, an unusual type of resonance which is associated with suppressed, rather than enhanced, transmission (i.e., antiresonance) emerges in the strongly nonadiabatic regime. The shift in the resonant transmission peaks is dependent on the spin-orbit interaction and therefore offers a way to directly measure these interactions in a ballistic one-dimensional system.

A low-cost, FPGA-based servo controller with lock-in amplifier

We describe the design and implementation of a low-cost, FPGA-based servo controller with an integrated waveform synthesizer and lock-in amplifier. This system has been designed with the specific application of laser frequency locking in mind but should be adaptable to a variety of other purposes as well. The system incorporates an onboard waveform synthesizer, a lock-in amplifier, two channels of proportional-integral (PI) servo control, and a ramp generator on a single FPGA chip. The system is based on an inexpensive, off-the-shelf FPGA evaluation board with a wide variety of available accessories, allowing the system to interface with standard laser controllers and detectors while minimizing the use of custom hardware and electronics. Gains, filter constants, and other relevant parameters are adjustable via onboard knobs and switches. These parameters and other information are displayed to the user via an integrated LCD, allowing full operation of the device without an accompanying computer. We demonstrate the performance of the system in a test setup, in which the frequency of a tunable external-cavity diode laser (ECDL) is locked to a resonant optical transmission peak of a Fabry-Perot cavity. In this setup, we achieve a total servo-loop bandwidth of ∼ 7 kHz and achieve locking of the ECDL to the cavity with a full-width-at-half-maximum (FWHM) linewidth of ∼ 200 kHz.

Split and Merge of Left–Right Circular Polarized Light through Coupled Magnetic Resonators

In order to obtain the means to control light polarization, we designed a structure of coupled magnetic resonators and studied its transmission properties by the 4x4 transfer matrix method. The incidence of linearly polarized light results in two transmission resonant peaks of left-handed circular polarization at shorter wavelengths and two transmission resonant peaks of right-handed circular polarization at longer wavelengths, respectively. Through adjusting the magnetizations, the inner left-handed circular polarization and right-handed circular polarization can be merged into one linear polarization, while the two outside resonant peaks keep their circular polarization. The polarized direction of the output linearly polarized light can be controlled by the polarized direction of incidence light. The incidence light with one polarization can output light with three kinds of polarizations through the designed structure.

DFT-NEGF study of transport properties and NDR behavior in fused furan and thiophene dimmers

Abstract The nonequilibrium Green's function approach in combination with density-functional theory is used to perform quantum mechanical calculations of the electron transport properties of furan and thiophene dimmers. Both the molecular systems have two S-linker and translated into the Gold junction with (1 1 1) surfaces. The studied molecular junctions at zero bias voltage are HOMO-based junctions and currents through these systems are driven by hole transport. The current–voltage characteristics of the both studied molecular junctions illustrate that negative differential resistance (NDR) feature is observed over the bias voltage of 2.0 V. Higher conductivity of fused furan dimmer and NDR character have been explained by the monitoring of the transmission resonance peak across the bias window against varying bias voltages.

Experimental demonstration of plasmonic Brewster angle extraordinary transmission through extreme subwavelength slit arrays in the microwave

We experimentally demonstrate the existence of a Brewster-like broadband extraordinary optical transmission band, in a very thick metal plate with an array of slits as narrow as $\ensuremath{\lambda}$/750 in the 8- to 40-GHz regime, by measuring the transmission from normal incidence to near grazing angles and mapping out the entire angular transmission spectrum. In the case of very narrow slits, an order of magnitude larger transmission is obtained at the Brewster angle when compared to the normal-incidence Fabry-P\'erot resonance transmission peaks. Full-wave numerical simulations are in excellent agreement with the measurements, paving the way for the observation of this phenomenon in the optical regime.

Infrared Tunable Multichannel Filter in a Doped Semiconductor-Dielectric Photonic Crystal Heterostructure

A design of near- to mid-infrared tunable multichannel filter (MCF) based on the doped semiconductor-dielectric photonic crystal (PC) heterostructure is proposed. Here, a strongly extrinsic semiconductor, <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> -type germanium ( <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> -Ge), is used as one of the constituent layers. The occurrence of multichannel feature originates from the negative-permittivity in the highly doped <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> -Ge. The existence of tunable feature is due to its concentration-dependent permittivity. It is of interest to find that, in such MCFs, the number of channels, i.e., the number of resonant transmission peaks, is directly related to the stack number, and these peaks are located within the pass band of the ideal host PC. The multiple channels are blueshifted as the impurity concentration increases. This design suggests an alternative of engineering the pass band for realizing an MCF instead of engineering photonic band gap in a PC containing photonic quantum well structure as a defect. Our analysis is made based on the transfer matrix method together with the Bloch theorem.

Transmission resonances in rectangular hole trimer arrays: the role of unit configuration

We fabricated trimer arrays consisting of three identical rectangular holes in each unit in silver films and measured the transmission spectra in the near-infrared region. Both the simulation using the finite difference time domain method and the experiment measurement show that the unit configuration plays a crucial role in the degeneracy of the transmission peak, which arises from the scattering of electromagnetic wave between adjacent units and electromagnetic coupling among holes in each unit. The field distribution suggests that the role an individual hole plays in the transmission resonance depends on the position of each hole and the surface plasmon polaritons' propagation direction. The results provide an additional way to tune the degeneracy of the transmission resonance peak in subwavelength metallic structures, which may find applications such as in filter devices, sensing, and the related nanophotonic components.

Electric quadrupole excitation in surface plasmon resonance of metallic composite nanohole arrays

We present an experimental and theoretical study on the composite nanostructures composed of the LT-shaped metallic nanohole arrays. Multiple resonance transmission peaks are observed in the optical transmission spectra. By analyzing their electric field distributions on the interface, we infer the electric dipole and the electric quadrupole plasmonic resonances contribute to these transmission peaks. The electric quadrupole is a subradiant mode, which cannot be directly excited by the incident light. Here, we demonstrate that the surface plasmon polaritons can excite the electric quadrupole plasmonic resonance mode through the near-field interaction.

A mid-infrared tunable filter in a semiconductor–dielectric photonic crystal containing doped semiconductor defect

In this work, we theoretically analyze tunable filtering properties in a semiconductor–dielectric photonic crystal (SDPC) containing doped semiconductor defect in the mid-infrared frequency region. We consider two possible configurations of filter structures, the symmetric and asymmetric ones. With a defect of the doped n-type semiconductor, n-Si, the resonant transmission peak can be tuned by varying the doping concentration, that is, the peak wavelength will be shifted to the position of lower wavelength for both structures. Additionally, by increasing the defect thickness, it is also possible to have a filter with multiple resonant peaks, leading to a multichannel filter. The results provide another type of tunable filter in the defective SDPC that could be of technical use for semiconductor applications in optical electronics.

Sub-wavelength phononic crystal liquid sensor

We introduce an acoustic liquid sensor based on phononic crystals consisting of steel plate with an array of holes filled with liquid. We both theoretically and experimentally demonstrate sensor properties considering the mechanism of the extraordinary acoustic transmission as underlying phenomenon. The frequency of this resonant transmission peak is shown to rely on the speed of sound of the liquid, and the resonant frequency can be used as a measure of speed of sound and related properties, like concentration of a component in the liquid mixture. The finite-difference time domain method has been applied for sensor design. Ultrasonic transmission experiments are performed. Good consistency of the resonant frequency shift has been found between theoretical results and experiments. The proposed scheme offers a platform for an acoustic liquid sensor.

Electronic transport in oligo-para-phenylene junctions attached to carbon nanotube electrodes: Transition-voltage spectroscopy and chirality

We have investigated, by means of a nonequilibrium Green's function method coupled to density functional theory, the electronic transport properties of molecular junctions composed of oligo-$\mathit{para}$-phenylene (with two, three, four, and five phenyl rings) covalently bridging the gap between metallic carbon nanotubes electrodes. We have found that the current is strongly correlated to a purely geometrical chiral parameter, both on-resonance and off-resonance. The Fowler-Nordheim plot exhibits minima, ${V}_{\mathrm{min}}$, that occur whenever the tail of a resonant transmission peak enters in the bias window. This result corroborates the scenario in which the coherent transport model gives the correct interpretation to transition voltage spectroscopy (TVS). We have shown that ${V}_{\mathrm{min}}$ corresponds to voltages where a negative differential resistance (NDR) occurs. The finding that ${V}_{\mathrm{min}}$ corresponds to voltages that exhibit NDR, which can be explained only in single-molecule junctions within the coherent transport model, further confirms the applicability of such models to adequately interpret TVS. The fact that the electrodes are organic is at the origin of differences in the behavior of ${V}_{\mathrm{min}}$ if compared to the case of molecular junctions with nonorganic contacts treated so far.

Voltage-controlled active mid-infrared plasmonic devices

We demonstrate active voltage-controlled spectral tuning of mid-infrared plasmonic structures. Extraordinary optical transmission gratings were fabricated on n-doped GaAs epilayers with a HfO2 gate dielectric between the grating and the doped semiconductor. The permittivity of the GaAs was tuned by depleting charge carriers below the top grating gate upon the application of a reverse bias to the gate. Devices were characterized both electrically and optically, and resonant transmission peak spectral and transmitted intensity shifts were achieved. Possible applications for, as well as the limitations of, the demonstrated technology are discussed.

Sound transmission through plates perforated with two periodic subwavelength hole arrays

Theoretical results on sound transmission through plates perforated with compoundperiodic hole arrays are presented. Calculations are obtained by means of a model underthe rigid-solid assumption, which is thoroughly derived. A complex interplaybetween resonant transmission peaks, resonance interference, and Wood anomalyminima is observed. At high frequencies the resonant peaks overcome the Woodanomaly dips, leading to a different behaviour when compared with simple holearrays.

衬底对外延生长的F-P滤波器传输性能的影响

The influence of GaAs substrate on the transmission performance of a multi-film Fabry-Peerot filter (FPF), fabricated by metalorganic chemical vapor deposition epitaxial growth on GaAs substrate, is investigated using the transfer matrix method. On the basis of the theoretical simulation, we determine that the quality of the resonant transmission peak of this epitaxially grown FPF (EG-FPF) deteriorates through splitting when the substrate is taken into account. Rapid periodic oscillation of peak-transmittivity along with the alteration of substrate thickness is also observed in the simulation results. Finally, a remarkably improved transmission performance of the EG-FPF is obtained by thinning the substrate down to a suitable thickness range through well-controlled grinding and polishing.

An &lt;i&gt;Ab Initio&lt;/i&gt; Study on Negative Differential Resistance in Pyrrole Trimer Molecular Device

The electronic transport properties of pyrrole trimer sandwiched between two electrodes are investigated by using nonequilibrium Green’s function formalism combined first-principles density functional theory. Theoretical results show that the system manifests negative differential resistance (NDR) behavior. A detailed analysis of the origin of negative differential resistance has been given by observing the shift in transmission resonance peak across the bias window with varying bias voltage.

Left handed transmission properties of planar metamaterials based on complementary double-ring resonators

We investigate the transmission properties of planar metamaterials based on complementary double-ring resonators, and a left-handed resonant transmission peak has been verified by both simulation and experimental results. The theoretical analysis and numerical simulation on the electromagnetic fields inside the metamaterial are provided to explain the physical origin of both electric and magnetic resonances. In addition, the backward wave propagation from the phase changes in the moving picture of electric field distribution is shown to confirm the left-handed behavior of the transmission line.

Enhanced optical transmission through double-layer gold slit arrays

We investigate the relationship between the transmission and the layer distance of double-layer gold slit arrays by using the finite-difference time-domain method. The results show that the transmission properties can be influenced strongly by layer distance. We attribute the two types of resonant modes to surface plasmon resonance and the localised waveguide resonance. We find that the localised waveguide transmission peak redshifts and becomes broader with increasing layer distance D. We also describe and explain the splitting, shift, and degeneration of the surface plasmon resonant transmission peak theoretically. In addition, to clarify the physical mechanism of the transmission behaviours, we analyse the distributions of electric field and total energy for the three transmission peaks with distance D = 45 nm for the double-layer system. Light transporting behaviours are mostly concentrated in the region of the slits as well as the interspaces of the two layers, and for different resonant wavelengths the electric field and energy distributions are different. It is expected that the results obtained here will be helpful for designing subwavelength metallic grating devices.