3D Uniform Manipulation of NV Centers in Diamond Using a Dielectric Resonator Antenna

Ensembles of nitrogen-vacancy color centers in diamond hold promise for ultra-precise magnetometry, competing with superconducting quantum interference device detectors. By utilizing the advantages of dielectric materials, such as very low losses for electromagnetic field, with the potential for creating high Q-factor resonators with strong concentration of the field within it, we implemented a dielectric resonator antenna for coherent manipulation of a large ensemble of nitrogen-vacancy centers in diamond. We reached average Rabi frequency of 10 MHz in a volume of 7 mm³ with a standard deviation of less than 1% at a moderate pump power. The obtained result enables use of large volume low nitrogen-vacancy concentration diamond plates in modern nitrogen-vacancy magnetometers thus improving sensitivity via larger coherence time and higher optical detected magnetic resonance contrast.     

Combined dielectric and plasmon resonance for giant enhancement of Raman scattering

Combined dielectric/metal resonators for colossal enhancement of inelastic light scattering are developed and their properties are investigated. It is shown that a record enhancement factor of 2 × 10⁸ can be obtained using these structures. The dielectric resonators are fabricated on Si/SiO₂ substrates where periodic arrays of square 10- to 200-nm-high dielectric pillars are produced via electron-beam lithography and plasma etching. The lateral size a of the pillars varies between 50 and 1500 nm, and their period in the array is 2a. To make a combined dielectric/metal resonator, a nanostructured layer of silver is deposited onto the fabricated periodic dielectric structure by thermal evaporation. It is established that, for a fixed height of the dielectric pillars, the Raman scattering enhancement factor experiences pronounced oscillations as a function of the period (and size) of the pillars. It is shown that these oscillations are determined by the modes of the dielectric resonator and governed by the relation between the excitation laser wavelength and the planar size of the dielectric pillars.     

Effect of modifying a methyl siloxane-based dielectric by a polymer thin film for pentacene thin-film transistors

We report on the fabrication of pentacene thin-film transistors (TFTs) utilizing a spun methyl siloxane-based spin-on-glass (SOG) dielectric and show that these devices can give a similar electrical performance as achieved by using pentacene TFTs with a silicon dioxide (SiO₂) dielectric. To improve the electrical performance of pentacene TFTs with the SOG dielectric, we employed a hybrid dielectric of an SOG/cross-linked poly-4-vinylphenol (PVP) polymer. The PVP film was deposited onto the spun SOG dielectric prior to pentacene evaporation, resulting in an improvement of the saturation field effect mobility (μ_sat) from 0.01 cm²/(V s) to 0.76 cm²/(V s). The good surface morphology and the matching surface energy of the SOG dielectric that was modified with the polymer thin film allow the optimized growth of crystalline pentacene domains whose nuclei are embedded in an amorphous phase.     

Room-temperature fabrication of ultra-thin ZrOx dielectric for high-performance InTiZnO thin-film transistors

In this letter, indium–titanium–zinc–oxide thin-film transistors with zirconium oxide (ZrO_x) gate dielectric were fabricated at room temperature. In the devices, an ultra-thin ZrO_x layer was formed as the gate dielectric by sol–gel process followed by ultraviolet (UV) irradiation. The devices can be operated under a voltage of 4 V. Enhancement mode operations with a high field-effect mobility of 48.9 cm²/V s, a threshold voltage of 1.4 V, a subthreshold swing of 0.2 V/decade, and an on/off current ratio of 10⁶ were realized. Our results demonstrate that UV-irradiated ZrO_x dielectric is a promising gate dielectric candidate for high-performance oxide devices.     

Material tensor parameters of LiNbO3 relevant for electro- and elasto-optics

The complete set of self-consistent parameters of nominally undoped LiNbO₃ crystals of congruent composition that describe the electro-optic, piezoelectric, elasto-optic, elastic, and dielectric response has been determined by numerically evaluating available measurements. The parameters were determined at room temperature and consist of the low-frequency clamped dielectric constants ε^S _ij, elastic stiffness constants at constant electric field C^E _ijkl, piezoelectric stress coefficients e_ijk, elasto-optic constants at constant electric field p^E _ijkl, and clamped electro-optic coefficients r^S _ijk. It is shown that the complete set is required for calculating the effective electro-optic coefficients and dielectric constants in photorefractive applications of LiNbO₃. Received: 4 January 2002 / Revised version: 1 February 2002 / Published online: 14 March 2002     

The Evaluation of Dielectric Resonators Containing H2O or D2O as RF Coils for High-Field MR Imaging and Spectroscopy

Electromagnetic resonators consisting of low-loss dielectric material and/or metallic boundaries are widely used in microwave technologies. These dielectric resonators usually have high Q factors and well-defined field distributions. Magnetic resonance imaging was shown as a way of visualizing the magnetic field distribution of the resonant modes of these resonators, if the dielectric body contains NMR sensitive nuclei. Dielectric resonators have also been proposed as RF coils for magnetic resonance experiments. The feasibility of this idea in high-field MR is discussed here. Specifically, the dielectric resonances of cylindrical water columns were characterized at 170.7 MHz (4 T¹H Larmor frequency), and evaluated as NMR transmit and receive coils. The dielectric resonance of a cylindrical volume of D₂O was used to image a hand at 170.7 MHz. This study demonstrated that MRI is an effective way of visualizing the magnetic field in dielectric structures such as a water cylinder, and can potentially be generalized to solid-state dielectric devices. The possible applications of dielectric resonators other than simple cylindrical volumes in MRI and MR solution spectroscopy at high field strengths are also discussed.     

Simulation of dielectric resonator for high-Tc radio frequency superconducting quantum interference device

Nowadays, the high-critical-temperature radio frequency superconducting quantum interference device (high-$T_{\rm c }$ rf SQUID) is usually coupled to a dielectric resonator that is a standard $10\times 10\times 1$~mm³ SrTiO$₃ (STO) substrate with a YBa₂Cu$₃O$_{7 - \delta }$ (YBCO) thin-film flux focuser deposited on it. Recently, we have simulated a dielectric resonator for the high-$T_{\rm c }$ rf SQUID by using the ANSOFT High Frequency Structure Simulator (ANSOFT HFSS). We simulate the resonant frequency and the quality factor of our dielectric resonator when it is unloaded or matches a 50-$\Omega$ impedance. The simulation results are quite close to the practical measurements. Our study shows that ANSOFT HFSS is quite suitable for simulating the dielectric resonator used for the high-$T_c rf SQUID. Therefore, we think the ANSOFT HFSS can be very helpful for investigating the characteristics of dielectric resonators for high-$T_c rf SQUIDs.     

Solvation energy of multiply charged anions and dielectric constant for finite system: a microscopic theory based bottom-up and top-down approach

This is the first time a microscopic theory-based bottom-up approach has been implemented to derive an analytical expression for the solvation energy for a finite (N) system, including the bulk. This bottom-up approach provides the information on solvation energies of anionic solutes in finite-size clusters, including the bulk (N = ∞), from the knowledge of the detachment energies for the system containing a few numbers of solvent molecules. However, in the case of dielectric constant, a microscopic theory-based top-down approach has been prescribed to derive an analytical expression for the static dielectric constant for the finite system. In this approach, the knowledge of the dielectric constant for the bulk provides a scheme to obtain the same quantity for a wide numbers of solvent molecules. As an illustrative example, the hydrated doubly charged anions, SO^?2 ₄.NH₂O and C₂O^?2 ₄.NH₂O, have been considered, and the calculated bulk solvation energy for the SO^?2 ₄.NH₂O system is found to be in very good agreement (within 5%) with the available experimental result. However, the same quantity calculated based on the Born model is found to be largely deviating (32%) from the experimental result. The calculated results of the dielectric constant for these two systems support the linear theory of dielectric constant.     

The SSA+ for scattering from dielectric surfaces at very low grazing angles

Previously we developed a practical model for scattering from randomly-rough surfaces at very low grazing angles for the Dirichlet problem which was found to give good numerical results. In this paper, we derive the expression for the bistatic scattering cross-section for the non-local small slope approximation for dielectric interfaces. We then extend our practical model to dielectric surfaces based on this result. We discuss numerical results for scattering at low forward grazing angles for a Gaussian roughness spectrum with an angle of incidence of 80^○.     

A two-fraction model for the calculation of the resonance spectra of the complex permittivity of ice in the far infrared

A two-fraction model that makes it possible to calculate analytically the complex dielectric permittivity of ice in the far infrared and submillimeter wavelength ranges is proposed. The librational and vibrational fractions are considered. The first fraction, consisting of rigid dipoles executing anharmonic reorientations in defects of the structure, gives rise to the librational band of ice at 800 cm^?1. The second fraction consists of elastically vibrating oppositely charged H-bonded molecules. This fraction describes two bands of ice in the range 100–300 cm^?1, and the nonresonant background of dielectric losses in the submillimeter wavelength range. The dielectric permittivity spectra of ice calculated for the temperature of ?7°C are consistent with the experimental spectra. The spectra of ice at the temperature ?30°C are predicted.     

Effects of the dielectric discontinuity on the photodetachment of H− ion

Using the closed orbit theory, we studied the effects of dielectric discontinuity on the photodetachment of H^? ions. The photodetachment cross-section of H^? in a medium with dielectric discontinuity was derived and calculated. The results have shown that the relative dielectric constants of the medium have a significant influence on the photodetachment of H^?. If H^? is kept in a medium with a relative small dielectric constant, the photodetachment cross-section of H^? becomes oscillating only in a small region above the ionization threshold. However, if H^? is kept in a medium with a relative large dielectric constant, the oscillation in the photodetachment cross-section becomes much stronger. Besides, the distance between H^? and the dielectric dividing interface also influences the photodetachment of H^?. For a given dielectric medium, the oscillation in the cross-section decreased with increasing distance between H^? and the dielectric dividing interface. Therefore, we can control the photodetachment of a negative ion by changing the dielectric constant and the ion–interface distance. This study provides a new understanding of the photodetachment process of negative ions in the presence of a dielectric medium.     

Open resonators for low dielectric loss measurements

Open resonators are studied based on the scattering theory. In particular, a theory of open resonators with a dielectric plate is constructed. This theory is used to develop a technique for measuring small dielectric loss. Measurements of the loss tangent in diamond plates show that the volume absorption in the best samples is ≈7×10^?6 in the high-frequency part of the millimeter-wave range. A significant absorption in thin surface layers that is caused by surface treatment techniques (polishing, vacuum soldering, etc.) is revealed.     

Local-field enhancement of spontaneous decay in nanosystems: some estimations for dielectric particles

Enhancement of the spontaneous decay rate due to local-field effects is estimated for a luminous dipole inside a small dielectric particle. To do this, we make use of an idea on multiplicativity of the local-field factor. Elongated particles are shown to be promising in respect of the local-field enhancement of the spontaneous emission. Computations are carried out within the framework of modern theory of the spontaneous decay of excited atoms in absorbing media for both the virtual-cavity and real-cavity models. Particular emphasis is placed on dielectric/semiconductor particles in the vicinity of the optical phonon frequencies. PACS 32.80.-t; 33.50.-j; 78.55.-m; 78.67.-nThis revised version was published in October 2004 with a new Figure 5.     

High-k Mg-doped ZST for microwave applications

The (Zr_0.8Sn_0.2)TiO₄ material (ZST), has been prepared by solid state reaction and characterized. The samples were sintered in the temperature range of 1260-1320 °C for 2 h. The effects of sintering parameters like sintering temperature (T_s) and MgO addition (0.2 wt.%) on structural and dielectric properties were investigated. Bulk density increases from 4900 to 5050 kg/m³ with the increase of sintering temperature. The effect of MgO addition is to lower the sintering temperature in order to obtain well sintered samples with high value of bulk density. The material exhibits a dielectric constant ?_r ∼ 37 and high values of the Q × f product, greater than 45,000, at microwave frequencies. The dielectric properties make the ZST material very attractive for microwave applications such as dielectric resonators, filters, dielectric antennas, substrates for hybrid microwave integrated circuits, etc.     

The anomalous relation of dielectric parameters to temperature for liquid nitrobenzene

Dielectric parameters are reported for pure nitrobenzene and dilute solutions in the microwave and radio-frequency ranges, together with the refractive index as a function of temperature at 6–45 °C. The dielectric parameters show marked anomalies at 11.28 and 34 °C on account of changes in the configuration of molecular assemblies. The most probable relaxation time is found to be 2.3 · 10^–11 sec and the critical wavelength 4.3 cm, the dielectric loss ⁿ then being maximal.     

Dielectric properties of pyridine N-oxide aqueous solution under the static electric field and microwave field

Molecular dynamics simulations of the pyridine N-oxide aqueous solution have been performed in the canonical ensemble macroscopic canonical ensemble (NVT) both in the absence and presence of an external electromagnetic field. It extracts the radial distribution function for each concentration solution, dielectric constant and other information on dielectric properties. Analysing the microscopic dielectric information of the aqueous solution under the static electric field (0–3×10⁹ V/m) and microwave frequencies (2.45G, 0–3×10⁹ V/m), and comparing the dielectric information between the different concentrations and different field strengths, we can get the dielectric properties of two kinds of polar aqueous solution under microwave irradiation. Thus, this project can provide the data of the sample to other correlation studies.     

Validity of the Makinson-Landau argument for surface electromagnetic fields

In 1937 Makinson introduced the first model for a space dependent dielectric function; this model was local. From this very simple form, he concluded that electric fields are enhanced near the surface of a metal. This argument was then rediscovered again and again by many people, in particular Landau. We analyze the validity of this argument with the hydrodynamic approximation to a non local space varying di-electric function, and find that it is relevant for quite reasonable values of the ratio of Z_o (which characterizes the spatial extent of the surface region) to k_so^-1 (the screening length of the dielectric function).     

Synthesis, magnetic and dielectric properties of Er-Ni doped Sr-hexaferrite nanomaterials for applications in High density recording media and microwave devices

A sol-gel combustion method has been successfully employed for the synthesis of Sr-hexaferrite nanomaterials doped with Er³⁺ and Ni²⁺ at strontium and iron sites, respectively. The X-ray diffraction analysis confirmed the single magnetoplumbite phase and the crystallite size was found to be in the range of 14-16 nm, suitable for obtaining signal-to-noise ratio in the high density recording media. The magnetic properties such as saturation magnetization (M_s), remanence (M_r) and coercivity (H_c) were calculated from hysteresis loops. M_s, M_r and H_c are observed to increase with the Er-Ni content. The dielectric constant (ε´) and dielectric loss (tan δ) is found to decrease with the increase in frequency and is explained on the basis of Maxwell-Wagner and Koops theory. The decrease in dielectric constant and dielectric loss but increase in saturation magnetization and remanence with Er-Ni content suggests that the materials are suitable for applications in microwave devices and high density recording media .     

Beam delivery characteristics of optical fibres for carbon monoxide lasers

An experimental investigation has been conducted of the propagation characteristics of several types of optical fibres which are candidates for use in optical beam delivery systems for carbon monoxide lasers. Both solid core (chalcogenide) fibres and hollow core (with dielectric or dielectric coated metal) waveguides have been investigated. Such experiments have included an assessment of both the power transmission characteristics, and the effects of waveguide transmission on the optical quality of the beam at the exit of the fibre. The experiments indicated lowest loss for the chalcogenide solid core fibre with a value of 0.4 dB m⁻¹.     

Ellipsometric studies of porous silicon

Multiple-angle-of-incidence (MAI) ellipsometry at 632.8 nm is used to characterize P and P⁺ porous silicon of high porosity. Complex dielectric constants are obtained, from which the porosity can be estimated qualitatively. The properties of the imaginary part of the dielectric constants are studied and the possible causes are discussed. Two dielectric constants, perpendicular and parallel to the interface, respectively, are measured based on a semi-infinite anisotropic model. Ellipsometric studies demonstrate a larger difference between the two dielectric constants in P⁺ porous silicon, but both P and P⁺ samples only show weak anisotropy, i.e., a network-like structure, which tends towards isotropy, is more suitable for porous silicon than a column-like one, which shows strong anisotropy.