Resonator Configuration Research Articles

High peak power side diode-pumped pulsed Nd:YAG laser with concave–concave stable resonator

In this paper, design and analysis of a side diode-pumped pulsed Nd:YAG laser oscillator has been presented by applying LASCAD software. Laser output energy is stabilized by using special configuration of an optical resonator. In this design, unsymmetrical concave–concave resonator is selected and this structure helps the mode volume to be nearly fixed when pulse repetition rate is increased. We also experimentally study and compare the performance of the Nd:YAG laser oscillator in the free-running and Q-switched operation under different pulse repetition rate from 1 to 100Hz. The structure of cavity head has a symmetrical three side configuration for uniform pumping of active medium. Each side consists of 6 Quasi-CW diode bars. The total pumping energy at 808nm is 400mJ. According to experimental results, for the free-running operation, the slope efficiency is 35% and the optical to optical efficiency is 22.25% at 100Hz. Also in the Q-switched operation, laser output energy obtained is nearly constant around 70mJ with 7ns of the FWHM pulse width at 100Hz. The optical to optical conversion efficiency of the Q-switched regime is about 17.5%. Output energies and spot sizes are obtained from experiments and compared with the LASCAD results.

Tidal resonance in icy satellites with subsurface oceans

AbstractTidal dissipation is a major heat source for the icy satellites of the giant planets. Several icy satellites likely possess a subsurface ocean underneath an ice shell. Previous studies of tidal dissipation on icy satellites, however, have either assumed a static ocean or ignored the effect of the ice lid on subsurface ocean dynamics. In this study, we examine inertial effects on tidal deformation of satellites with a dynamic ocean overlain by an ice lid based on viscoelasto‐gravitational theory. Although ocean dynamics is treated in a simplified fashion, we find a resonant configuration when the phase velocity of ocean gravity waves is similar to that of the tidal bulge. This condition is achieved when a subsurface ocean is thin (<1 km). The enhanced deformation (increased h2 and k2 Love numbers) near the resonant configuration would lead to enhanced tidal heating in the solid lid. A static ocean formulation gives an accurate result only if the ocean thickness is much larger than the resonant thickness. The resonant configuration strongly depends on the properties of the shell, demonstrating the importance of the presence of a shell on tidal dissipation.

On the migration of two planets in a disc and the formation of mean motion resonances

We study the dynamics of a system of two super-Earths embedded in a protoplanetary disc. We build a simple model of an irradiated viscous disc and use analytical prescriptions for the planet-disc interactions which lead to migration. We show that depending on the disc parameters, planets' masses and their positions in the disc, the migration of each planet can be inward or outward and the migration of a two-planet system can be convergent (which may lead to formation of a first order mean motion resonance, MMR) or divergent (a system moves away from MMR). We performed $3500$ simulations of the migration of two-planet systems with various masses and initial orbits. Almost all of them end up as resonant configurations, although the period ratios may be very distant from the nominal values of a given MMR. We found that almost all the systems resulting from the migration are periodic configurations.

Efficient scheme for mid-infrared generation using simultaneous optical parametric oscillators and DFG processes in a double-pass pump configuration.

We present numerical results of an efficient scheme for mid-infrared generation using simultaneous quasi-phase matched optical parametric oscillators (OPO) and difference-frequency generation (DFG) processes in a singly resonant cavity with double-pass pump configuration. Considering an appropriately poled grating structure in MgO doped congruent lithium niobate, we have shown that it is possible to realize the double-pass pump singly resonant (DPSR) cavity configuration for the simultaneous OPO+DFG process, unlike the cascaded interaction scheme, leading to efficient mid-IR generation. Our numerical results are in agreement with the recently reported experimental results. We also present optimum parameters for the DPSR cavity configuration that could provide maximum conversion efficiency.

Intracavity CH 4 Raman laser using negative-branch unstable resonator

An intracavity Q-switched Nd:YAG/CH4 Raman laser is realized based on the configuration of a negative-branch confocal unstable resonator. A numerical model of the bare resonator was introduced to simulate the fundamental transverse mode and calculate the loss of the fundamental resonator. With different magnifications of the fundamental resonator, the first Stokes output energy was presented as a function of the discharge voltage. The influence of the Stokes resonator on Raman conversion was analyzed. With a fundamental resonator magnification of 1.1, a maximum output energy of 58 mJ was obtained, and the corresponding photon conversion efficiency was 48%.

Numerical simulation of 30-kW class liquid-cooled Nd:YAG multi-slab resonator.

A numerical modeling is developed for 30-kW class liquid-convection-cooled elastically-mounted Nd:YAG multi-slab laser resonator configuration. The modeling exhibits the thermal effects and resultant wavefront aberration of the gain module under flow cooling and CW pumping at 100-kW level, the self-reproducing oscillating mode within the large-aperture cavity, as well as the beam quality enhancement by adaptive optics. The simulation results predict a CW output power of 31 kW with the optical-optical efficiency of 26.1% obtained from a modified resonator configuration with dual gain modules that have opposite flow directions, while the beam quality can be improved to β<2 after the correction of a deformable mirror.

Quantum Effects in Charge Transfer Plasmons

Metallic nanoparticles placed in close proximity support strong localized surface plasmon resonances. One such resonance, known as the charge transfer plasmon, involves the physical transfer of electrons between the nanoparticles and, thus, exists only in dimers bridged with conductive junctions. Here we analyze the quantum effects associated with these type of plasmon modes by studying the optical response of a metallic dimer bridged with a two-level system. We find that the charge transfer plasmons are observed in the absorption spectrum only when one of the energy levels of the two-level system is resonant with the Fermi level of the nanoparticles. Furthermore, we explicitly show that, for the resonant configuration, the conductance of the junction reaches a value equal to one quantum of conductance, 2e2/h. Our results establish a connection between the optical response of plasmonic nanostructures and quantum transport phenomena, thus bringing a new perspective to quantum plasmonics.

Stability of resonant configurations during the migration of planets and constraints on disk-planet interactions

We study the stability of mean-motion resonances (MMR) between two planets during their migration in a protoplanetary disk. We use an analytical model of resonances, and describe the effect of the disk by a migration timescale (T_{m,i}) and an eccentricity damping timescale (T_{e,i}) for each planet (i=1,2 respectively for the inner and outer planet). We show that the resonant configuration is stable if T_{e,1}/T_{e,2} > (e_1/e_2)^2. This general result can be used to put constraints on specific models of disk-planet interactions. For instance, using classical prescriptions for type I migration, we show that when the angular momentum deficit (AMD) of the inner orbit is larger than the outer's orbit AMD, resonant systems must have a locally inverted disk density profile to stay locked in resonance during the migration. This inversion is very untypical of type I migration and our criterion can thus provide an evidence against classical type I migration. That is indeed the case for the Jupiter-mass resonant systems HD 60532b, c (3:1 MMR), GJ 876b, c (2:1 MMR), and HD 45364b, c (3:2 MMR). This result may be an evidence for type II migration (gap opening planets), which is compatible with the large masses of these planets.

XeCl excimer laser with new prism resonator configurations and its performance characteristics.

New resonator cavity configurations, namely, the prism resonator and unstable prism resonator, are demonstrated for the first time in an excimer (XeCl) laser with interesting and novel results. High misalignment tolerance ∼50 mrad is achieved with considerably reduced beam divergence of less than ∼1 mrad without reduction in output power capabilities of the laser. The misalignment tolerance of ∼50 mrad is a dramatic improvement of ∼25 times compared to ∼2 mrad normally observed in standard excimer laser with plane-plane cavity. Increase in depth of focus from 3 mm to 5.5 mm was also achieved in case of prism resonator configuration with an improvement of about 60%. Unstable prism resonator configuration is demonstrated here in this paper with further reduction in beam divergence to about 0.5 mrad using plano-convex lens as output coupler. The misalignment tolerance in case of unstable prism resonator was retained at about 30 mrad which is a high value compared to standard unstable resonators. The output beam spot was completely filled with flat-top profile with prism resonator configurations, which is desired for various material processing applications. Focusing properties and beam divergence in case of prism resonator have been investigated using SEM (scanning electron microscope) images. SEM images of the focused spot size (∼20 μm holes) on metal sheet indicate beam divergence of about 0.05 mrad which is about 1.5 times diffraction limit. Energy contained in this angle is thus sufficient for micro-machining applications. Clean and sharp edges of the micro-holes show high pointing stability with multiple shot exposures. Such characteristics of the excimer laser system will be extremely useful in micro-machining and other field applications.

Quantifying charge resonance and multiexciton character in coupled chromophores by charge and spin cumulant analysis.

We extend excited-state structural analysis to quantify the charge-resonance and multi-exciton character in wave functions of weakly interacting chromophores such as molecular dimers. The approach employs charge and spin cumulants which describe inter-fragment electronic correlations in molecular complexes. We introduce indexes corresponding to the weights of local, charge resonance, and biexciton (with different spin structure) configurations that can be computed for general wave functions thus allowing one to quantify the character of doubly excited states. The utility of the approach is illustrated by applications to several small dimers, e.g., He-H2, (H2)2, and (C2H4)2, using full and restricted configuration interaction schemes. In addition, we present calculations for several systems relevant to singlet fission, such as tetracene, 1,6-diphenyl-1,3,5-hexatriene, and 1,3-diphenylisobenzofuran dimers.

DYNAMICAL STABILITY OF IMAGED PLANETARY SYSTEMS IN FORMATION: APPLICATION TO HL TAU

A recent ALMA image revealed several concentric gaps in the protoplanetary disk surrounding the young star HL Tau. We consider the hypothesis that these gaps are carved by planets, and present a general framework for understanding the dynamical stability of such systems over typical disk lifetimes, providing estimates for the maximum planetary masses. We collect these easily evaluated constraints into a workflow that can help guide the design and interpretation of new observational campaigns and numerical simulations of gap opening in such systems. We argue that the locations of resonances should be significantly shifted in massive disks like HL Tau, and that theoretical uncertainties in the exact offset, together with observational errors, imply a large uncertainty in the dynamical state and stability in such disks. This presents an important barrier to using systems like HL Tau as a proxy for the initial conditions following planet formation. An important observational avenue to breaking this degeneracy is to search for eccentric gaps, which could implicate resonantly interacting planets. Unfortunately, massive disks like HL Tau should induce swift pericenter precession that would smear out any such eccentric features of planetary origin. This motivates pushing toward more typical, less massive disks. For a nominal non-resonant model of the HL Tau system with five planets, we find a maximum mass for the outer three bodies of approximately 2 Neptune masses. In a resonant configuration, these planets can reach at least the mass of Saturn. The inner two planets' masses are unconstrained by dynamical stability arguments.

Dynamics in many-body localized quantum systems without disorder

We study the relaxation dynamics of strongly interacting quantum systems that display a kind of many-body localization in spite of their translation-invariant Hamiltonian. We show that dynamics starting from a random initial configuration is nonperturbatively slow in the hopping strength, and potentially genuinely nonergodic in the thermodynamic limit. In finite systems with periodic boundary conditions, density relaxation takes place in two stages, which are separated by a long out-of-equilibrium plateau whose duration diverges exponentially with the system size. We estimate the phase boundary of this quantum glass phase, and discuss the role of local resonant configurations. We suggest experimental realizations and methods to observe the discussed nonergodic dynamics.

Peformance Analysis of LLC-LC Resonant Converter Fed PMDC Motor

In this paper, a modified form of the most efficient resonant LLC series parallel converter configuration (SPRC) is proposed. The proposed system comprises of an additional LC circuit synchronized along with the existing resonant tank of LLC configuration (LLC-LC configuration). With the development of power electronics devices, resonant converters have been proved to be more efficient than conventional converters as they employ soft switching technique. Among the three basic configurations of resonant converter, Series Resonant Converter (SRC), Parallel Resonant Converter (PRC) and Series Parallel Resonant Converter, the LLC configuration under SPRC is proved to be most efficient providing narrow switching frequency range for wide range of load variation, improved efficiency and providing ZVS capability even at no load. The modified LLC configuration i.e., LLC-LC configuration offers better efficiency as well as better output voltage and gain. The efficiency tends to increase with increase in input voltage and hence these are suitable for high input voltage operation. In this paper, LLC topology of SPRC and a modified LLC topology (LLC-LC) of SPRC for the closed loop control of a BLDC motor are simulated and their performances are compared and analyzed.

Sensitivity and figure-of-merit enhancements of liquid-prism SPR sensor in the angular interrogation

We use a glass slide covered with metal film as the sensing chip and the liquid over the glass slide as the prism (also called liquid prism) to excite the surface plasmon between the metal and the sample in a Kretschmann–Raether surface plasmon resonance (SPR) configuration. In this work, we demonstrate theoretically and experimentally that the lower refractive index of the liquid prism can enhance the angular sensitivity and the figure of merit (FOM) of SPR sensor. Meanwhile, the adjustment of the refractive index of the liquid prism is easier than the solid prism, and the more suitable refractive index of the liquid prism can be obtained for the specific sample to enhance the sensitivity and the FOM. The proposed liquid prism SPR configuration provided a new chemical and biological SPR sensing application with highly sensitive and high FOM.

Modeling of acoustic resonators and resonator arrays for use in passive noise control

Acoustic resonators, such as the Helmholtz and quarter-wave resonator, can be used to attenuate unwanted noise in a space. Classic formulations can be used to approximate resonator performance for a given resonator configuration, but may lack sufficient accuracy for some applications. This research aims to improve the analytical characterization of resonators to provide better correlation to experimental results. Using higher order approximations and proper end corrections, more accuracy can be obtained in calculating the impedance and resonance frequency of a single resonator, which will then carry over into the overall configuration of the model. The impedance of a system of resonators in parallel is also considered, where the effects of acoustic coupling can be observed. Resonators with complex, non-ideal geometries are explored for applications where space is limited.

Orbital instability of close-in exomoons in non-coplanar systems

This work shows the dynamical instability that can happen to close-in satellites when planet oblateness is not accounted for in non-coplanar multiplanet systems. Simulations include two secularly interacting Jupiter-mass planets mutually inclined by 10 degrees, with the host planet either oblate or spherical. With a spherical host planet, moons within a critical planetocentric distance experience high inclinations and in some cases high eccentricities, while more distant moons orbit stably with low inclinations and eccentricities, as expected. These counter-intuitive dynamical phenomena disappear with an oblate host planet, in which case the moons' Laplace plane transitions from the host planet's equatorial plane to the host planet's precessing orbital plane as their semi-major axes increase, and all moons are dynamically stable with very mild changes in orbits. Direct perturbation from the perturbing planet has been investigated and ruled out as an explanation for the behavior of the innermost satellites, therefore leaving the central star's perturbation as the cause. Instability occurs while the nodal precession of the satellite and the central star (as seen from the host planet's frame) approaches the 1:1 secular resonance. In non-coplanar systems, around a non-oblate planet, the nodal precession of the moon becomes slow and comparable to that of the planet, giving rise to resonant configurations. The above effect needs to be taken into account in setting up numerical simulations.

Arbitrary frequency tunable radio frequency bandpass filter based on nano-patterned Permalloy coplanar waveguide (invited)

A well designed coplanar waveguide (CPW) based center frequency tunable bandpass filter (BPF) at 4 GHz enabled with patterned Permalloy (Py) thin film has been implemented. The operating frequency of BPF is tunable with only DC current without the use of any external magnetic field. Electromagnetic bandgap resonators structure is adopted in the BPF and thus external DC current can be applied between the input and output of the filter for tuning of Py permeability. Special configurations of resonators with multiple narrow parallel sections have been considered for larger inductance tenability; the tunability of CPW transmission lines of different widths with patterned Py thin film on the top of the signal lines is compared and measured. Py thin film patterned as bars is deposited on the top of the multiple narrow parallel sections of the designed filter. No extra area is required for the designed filter configuration. Filter is measured and results show that its center frequency could be tuned from 4 GHz to 4.02 GHz when the DC current is applied from 0 mA to 400 mA.

Optical resonators based on Bloch surface waves

A few recent works suggest the possibility of controlling light propagation at the interface of periodic multilayers supporting Bloch surface waves (BSWs), but optical resonators based on BSWs are yet to be demonstrated. Here we discuss the feasibility of exploiting guided BSWs in a ring resonator configuration. In particular, we investigate the main issues related to the design of these structures, and we discuss their limitations in terms of quality factors and dimensions. We believe these results might be useful for the development of a complete BSW-based platform for applications ranging from optical sensing to the study of the light&#x2013;matter interaction in micro and nano structures.

Imaging AOTFs with Low RF Power in Deep-UV and Mid-IR

Acousto-Optic Tunable Filters (AOTFs) are commonly used for applications where high speed tuning and narrow spectral resolu- tion are required. The RF drive power for peak diffraction efficiency increases as λ2 and depends on the acousto-optic figure of merit (M2), which is material dependent. In the VIS-IR region between 450nm and 4.5μm tellurium dioxide (TeO2) is the common material of choice due to the high M2. At longer wavelengths (up to about 12μm) the mercurous halides and single crystal tellurium show promise. In both cases the λ2 dependency dominates the RF power consumption and for wavelengths beyond 3.5μm the RF power consumption is above the practical limit (>5W) for larger aperture AOTF(> 10mm × 10mm). In the UV range (200nm – 400nm) the λ2 dependency is no longer dominant and the power consumption depends mainly on the M2,however, for most materials transparent in the UV the M2 is poor and thus the drive power will again be excessive (>5W). In order to reduce the RF power requirement to reach peak diffraction efficiency, a resonant configuration in crystal quartz shows promise, especially in the UV range due to its low acoustic attenuation. We describe an AOTF operating in resonance made of crystal quartz, where the reduction of RF power consumption will be reduced by a factor between 15 and 20 compared to a conventional AOTF, thus reducing the power consumption to be within the practical limit (<5W).

Formation and evolution of the two 4/3 resonant giants planets in HD 200964

It has been suggested that HD 200964 is the first exoplanetary system with two Jovian planets evolving in the 4/3 mean- motion resonance. Previous scenarios to simulate the formation of two giant planets in the stable 4/3 resonance configuration have failed. Moreover, the orbital parameters available in the literature point out an unstable configuration of the planetary pair. The purpose of this paper is i) to determine the orbits of the planets from the RV measurements and update the value of the stellar mass (1.57 M), ii) to analyse the stability of the planetary evolution in the vicinity and inside the 4/3 MMR, and iii) to elaborate a possible scenario for the formation of systems in the 4/3 MMR. The results of the formation simulations are able to very closely reproduce the 4/3 resonant dynamics of the best-fit config- uration obtained in this paper. Moreover, the confidence interval of the fit matches well with the very narrow stable region of the 4/3 mean-motion resonance. The formation process of the HD 200964 system is very sensitive to the planetary masses and protoplanetary disk parameters. Only a thin, flat disk allows the embryo-sized planets to reach the 4/3 resonant configuration. The stable evolution of the resonant planets is also sensitive to the mass of the central star, because of overlapping high-order resonances inside the 4/3 resonance. Regardless of the very narrow domain of stable motion, the confidence interval of our fit closely matches the stability area.