Modified Ring Resonator Research Articles

Two-dimensional photonic crystal hexagonal waveguide ring laser

Hexagonal ring-type resonators defined by two-dimensional photonic crystal waveguides are proposed and demonstrated. Lasing actions are observed from the photonic crystal ring resonator patterned on a free-standing slab with InGaAsP active layers emitting near 1.55 μm. For a ring resonator with 8-μm diameter, the threshold peak pump power is ∼3 mW. The quality factor of the ring resonator mode estimated from below-threshold linewidth shows that the sum of the propagation loss and the bending loss of the photonic crystal ring resonator is less than ∼260 cm−1. The photonic crystal ring resonators can be used for the characterization of the optical losses in photonic crystal waveguides.

A new coupling structure for dual mode dielectric resonators

A novel method for realizing coupling between two orthogonal HEM/sub 11/ resonant modes in dielectric ring resonators is described. The coupling is obtained by means of a metallic strip located on the inner or on the outer boundary of the dielectric ring; a strong coupling is obtained, even with a small width of the strip, in particular when the strip is on the inner boundary. The dual-mode resonator is then suitable for filtering applications, with normalized bandwidth requirements exceeding 1% (as in base station units for mobile communications), allowing a relevant reduction of the overall volume, at the expense of a small reduction of the unloaded Q. The novel coupling mechanism and the Q degradation produced have been studied both numerically (by using finite elements simulations) and experimentally (measurements from a prototype two-resonators filter are reported).

Performance of superconducting dual mode resonators with different input/output feedline angles

High-temperature superconducting (HTS) dual mode ring resonators have been fabricated using YBa/sub 2/Cu/sub 3/O/sub 7-x/ films on MgO substrates. Epitaxial YBCO superconducting thin films were deposited on MgO substrates by pulsed laser deposition (PLD). The transition temperature of YBCO thin films were 85-88 K. Dual mode ring resonators are patterned using YBCO superconducting films by conventional photolithography and wet-etching process. The opposite side of the substrate has been made up the ground plane with two layer metal films (Ti/Ag) deposited by e-beam and thermal evaporation. Two types of dual mode ring resonators were fabricated with different input and output feedline angles of 60/spl deg/ and 100/spl deg/. The frequency response shows the resonant center frequency of about 8.5 GHz and stringent narrow bandwidths. These types of dual mode ring resonators could be utilized for dual mode resonator based filters for satellite communications.

Split modes in asymmetric microstrip ring resonator by flexible perturbation

Split modes in asymmetric microstrip ring resonator by flexible perturbation

Split modes in asymmetric microstrip ring resonator by flexible perturbation

The microwave microstrip ring resonator (MRR) is perturbed by a flexible, nondestructive method of keeping cross and partial overlays of Al2O3 strips. The splitting of the resonance curve is observed with amplitude variations as expected theoretically, but is not observed below a critial perturbation. Further empirical relations are reported for the first time, for the odd-mode frequency (fro) and even-mode frequency (fre) variations, giving fre changes proportional to the perturbation, but fro being independent of the same. © 1998 John Wiley & Sons, Inc. Microwave Opt Technol Lett 19: 168–171, 1998

Role of perturbations for dual mode superconducting microstrip resonators fabricated by laser ablation

The comparison of frequency response characteristics between various types of superconducting dual mode resonators has been performed. Epitaxial superconducting YBa/sub 2/Cu/sub 3/O/sub 7-x/ (YBCO) thin films have been have been grown on MgO substrates by laser ablation. Perturbed disk and ring types of superconducting dual mode resonators were patterned by photolithography and a wet-etch process. Unlike the unperturbed case, dual mode resonators have different resonant properties for the perturbed case depending on the position of the perturbation. We observed the same resonant peak splitting properties at the fundamental resonances of the perturbed dual mode disk and ring resonators. Peak properties caused by perturbation in the dual mode resonators could be used in implementing a two pole bandpass filter by itself. >

Suppression of even modes in microstrip ring resonators

Unwanted even order modes in tunable microstrip ring resonators can be suppressed by providing a low resistance path to ground at an appropriate point on the ring. This suppression method is simple to implement, and has minimal effect on the Q factor and the resonance frequency of the wanted modes.

Self-modulated stimulated emission from solid-state ring lasers with nonplanar resonators

A new approach is developed for the description of self-modulated operation of solid-state ring lasers. This type of operation is considered as a superposition of two normal modes of a ring resonator with retroreflectors. The normal modes of ring resonators with retroreflectors are found using the 4 × 4 matrix formalism. The frequency characteristics of rotating nonplanar ring lasers, including monolithic chip lasers, are calculated.

Microwave Impedance Studies on High Temperature Superconductors Using a Dielectric Sapphire Resonator in High Magnetic Fields

ABSTRACTThe vortex dissipation in an Nd-Ce-Cu-Ol epitaxial film is measured at microwave frequencies using the high-Q modes of a sapphire ring resonator, over a large range of temperatures and external DC magnetic fields. The results are qualitatively consistent with a generalized thermally-activated flux-flow (TAFF) model.

Resonant frequency analysis of dielectric ring resonators

The mode-matching technique is applied to guided and continuous spectra to derive the resonant frequencies of the high-order azimuthal modes of dielectric ring resonators. The numerical results of this field theory analysis are in close agreement with the measurements in the X-band.

Calculations of fields in resonators with wavefront-reversing mirrors

It is shown rigorously that the problem of determining the oscillation modes of ring resonators with wavefront-reversing mirrors can be reduced to the determination of the oscillation modes of a certain equivalent resonator with ordinary mirrors. Methods of determining the parameters of an equivalent resonator are described and it is established that this can be both stable and unstable. The advantages of ring resonators with wavefront-reversing mirrors are noted.

Selection of the principal transverse mode in a ring resonator

It is shown that the caustic surface which forms the boundary of a transverse mode with indices q and r has a rectangular cross section if the resonator is of the ring type. Expressions are derived for the determination of the dimensions of a rectangular-aperture diaphragm which can be used to select the principal mode and suppress higher modes in various ring resonators.