Fundamental Cavity Mode Research Articles

Numerical modeling of hydromagnetic wave coupling in the magnetosphere

We have developed a simple computer code that simulates the electromagnetic response of a simplified magnetosphere with respect to pressure variations at the magnetopause. The dependence of the magnetospheric response on the azimuthal wave number of the magnetopause perturbation and possible effects of a kinetic correction to the Alfvén wave dispersion are investigated. We find that the coupling of the cavity mode to Alfvén oscillations is most efficient for wave numbers m = 1 … 3. With increasing wave number, the fundamental cavity mode may lower its eigenfrequency, opposed to the behavior of the higher‐order modes. Kinetic effects cause a propagation of Alfvén wave energy away from the resonant field line.

Observation of step structures on the resistive branches of long Josephson tunnel junctions

Abstract We have observed well defined current steps superimposed on the resistive branches associated with non-resonant vortex propagation in a long Sn-oxide-Sn junction. Experimental data suggest that these step structures are due to the interaction between the traveling vortex and the cavity modes whose frequencies are given by νn = nνc, where νc is the frequency of the fundamental cavity mode and n is an integer. The voltage-frequency relation for those steps are found to be 2eV = (n/m)hνc, where m is an integer greater than n. This is different from that of the Fiske steps and the zero field steps of a short junction for which the fraction n/m is replaced by an integer equal to or greater than unity.

Cavity-mode excitation in a Josephson tunnel junction

Using Takanaka's theory of the zero-field dc-current steps of a Josephson tunnel junction, we have studied the effect of the junction $Q$ factor on the shape of the current step near the first even-order resonant voltage $V=h\frac{{\ensuremath{\nu}}_{c}}{e}$, where ${\ensuremath{\nu}}_{c}$ is the frequency of the fundamental cavity mode. In addition, we have found that the effect of a magnetic field on the step height can be qualitatively explained by modifying Takanaka's theory to include a magnetic-field-dependent term.

Pulsed chemical lasers initiated by laser photolysis

Use of laser photolysis for initiation of pulsed chemical lasers is described. In laser-initiated chemical lasers, the transient photochemical state evolves from a well-defined initial state without obscurant time variation of photolysis products. Spatial confinement of the initiating radiation reduces undesired effects of reflections from the enclosure walls and permits near coincidence between the reactant volume and that of the fundamental cavity mode. Application of the laser-initiation technique to an HF laser pumped by H <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> + F <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> chain reactions is discussed. Two distinct time regimes are found in the HF laser transient. The laser intensity in the initial regime exhibits large amphtude pulses characteristic of unsteady oscillations in high-gain media, whereas the relatively low-levels intensity in the second regime exhibits long-term variations characteristic of quasi-steady changes induced by reaction-deactivation processes. Variation of intensity features in both time regimes with physical parameters governing the photochemical state of the reactant media is described.

Design of a Microwave-Frequency Light Modulator

A device is described which intensity modulates a light beam at modulating frequencies in the microwave region. A high-Q re-entrant capacity-loaded coaxial-line resonator employing a properly oriented slab of uniaxial crystal of the dihydrogen phosphate variety as its dielectric medium is coupled to a microwave-frequency generator tuned to the fundamental cavity mode. A light path is provided through the resonator so that a beam of plane polarized light can pass through the crystal into a suitably oriented analyzer. The intensity of the light beam emerging from the latter varies at the same rate as the cavity frequency.