UWB radiation from superconductor undergoing fast superconducting to normal transition

Supercond. Sci. Technol.

Murphy

et al. 2019

We examine the microwave radiation emitted from inductively charged centimeter-scale YBCO (YBa2Cu3O7-δ) annular rings illuminated with a 45 fs, 790 nm laser pulse. The electromagnetic radiation from the rings shows the following behavior. (1) Radiation emitted perpendicular to the plane of the ring is polarized parallel to the plane of the ring and across the point of illumination. (2) The in-plane radiation pattern resembles that of a loop antenna with the orientation of the pattern determined by the location of the illumination point. (3) The dominant frequency of the emitted radiation shows an inverse dependence on the ring diameter. (4) The emitted energy is proportional to energy stored in the ring for a number of different geometries, with thinner films displaying a higher efficiency. Finally, (5) the emitted energy grows exponentially with small laser pulse energy values and approaches saturation for higher energies. These results indicate that optically induced electromagnetic radiation from superconducting structures holds promise for a versatile, compact, self-contained superconducting microwave emitter platform.

Section: Introductionmentioning

confidence: 99%

Microwave antenna properties of an optically triggered superconducting ring

Bullard

Supercond. Sci. Technol.

Murphy

et al. 2019

“…Fast transients in direct current (DC) circuits is an active area of research, not addressed by lumped parameter models or antenna theory, where radiation and near-field effects may become significant to the circuit’s energy balance and must be fully taken into account. The general result of recent theoretical analysis derives an oscillatory circuit current that departs from lumped parameter behavior as it interacts with the reactive near field, potentially with higher radiation efficiency1011. Another important aspect of the device is that it demonstrates radiation from explicit symmetry breaking.…”

mentioning

confidence: 99%

Tunable Broadband Radiation Generated Via Ultrafast Laser Illumination of an Inductively Charged Superconducting Ring

Bullard

Dolasinski

et al. 2015

Sci Rep

An electromagnetic transmitter typically consists of individual components such as a waveguide, antenna, power supply, and an oscillator. In this communication we circumvent complications associated with connecting these individual components and instead combine them into a non-traditional, photonic enabled, compact transmitter device for tunable, ultrawide band (UWB) radiation. This device is a centimeter scale, continuous, thin film superconducting ring supporting a persistent super-current. An ultrafast laser pulse (required) illuminates the ring (either at a point or uniformly around the ring) and perturbs the super-current by the de-pairing and recombination of Cooper pairs. This generates a microwave pulse where both ring and laser pulse geometry dictates the radiated spectrum’s shape. The transmitting device is self contained and completely isolated from conductive components that are observed to interfere with the generated signal. A rich spectrum is observed that extends beyond 30 GHz (equipment limited) and illustrates the complex super-current dynamics bridging optical, THz, and microwave wavelengths.

Radiation and near field in resistance-inductor circuit transients

Latypov

Journal of Applied Physics

2012

A full wave solution to the classical problem of a transient response in an RL circuit is analyzed. We show that when radiation effects are rigorously taken into account, the response differs from a familiar exponential decay. The circuit behaves more like an RLC circuit and can exhibit an underdamped response. As a result of a two way energy transfer between the circuit and the near field in the underdamped regime, despite the radiation losses, current decay may be slower than predicted by the standard RL circuit model. During a transient, when retardation effects become important, inductance can no longer be defined as a coefficient of proportionality between the magnetic flux through the circuit and the current in the circuit. If rate of current decay is nearly constant, one can define a time-dependent generalized inductance which turns into conventional inductance after time D/c, where D is the diameter of the current loop. Connection of this generalized inductance with the radiation damping problem is discussed. The theory developed in this paper has been used to analyze ultra wide band radiation observed during a fast laser triggered superconducting to normal transition of a superconducting switch.