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

Abstract

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.

Microwave antenna properties of an optically triggered superconducting ring

“…Signals in figure 7(a) were captured in the z-direction. As has been previously reported, we do not observe a change in spectral energy distribution due to laser intensity or current level [31]. A dominant peak is observed in the energy spectrum for each ring size.…”

“…Emission from inductively charged centimeter scale YBCO thin film rings on sapphire in the microwave portion of the spectrum have also been investigated [28][29][30][31]. The experiment was designed such that rings were isolated from the power supply, wires, and other electronics to avoid electromagnetic coupling.…”

Electromagnetic Radiation Under Phase Symmetry Breaking in Quantum Systems

“…The radiation could be tuned by varying the pattern of laser illumination. It could be argued that laser excitation resulted in spatial phase symmetry breaking of the cooper pairs, which resulted in radiation [22]. Such observations can be used to design further experiments to investigate related physical effects in radiation from Josephson junctions.…”

The Noether current in Maxwell's equations and radiation under symmetry breaking

“…The concept of explicit symmetry breaking has also been applied in experiments on generation of tunable broadband radiation from a superconducting ring where a pulse of laser light breaks the symmetry of cooper pairs, resulting in electromagnetic radiation [38]. Under explicit symmetry breaking, the momentum current associated with the test charge loses its conserved value within a localized region of space and time as the corresponding Noether current is the driver of electromagnetic radiation.…”

“…Earlier, it was pointed out by Sinha & Amaratunga that the assumptions by Long et al violate the foundational aspects of radiating systems as a time varying excitation fed to a dielectric material generates oscillations of bound charges which is essentially oscillation of electrical dipoles which are inversely proportional to the cube of distance [35,38]. The electric field E, associated with a Hertzian dipole in spherical coordinates along the dimensions r, θ and φ, is expressed by [49] E r = η IL cos θ 2π r 2 Here, I is the current in the antenna, L is its length, η is the intrinsic impedance of space, k is the wavenumber associated with the wave and j = √ −1.…”