Experimental implementation of a large scale multipost re-entrant array

Abstract

We demonstrate possibilities of a large scale multi-post re-entrant cavity with two case studies implemented with the same physical structure. The first demonstration implements two discrete Fabry-Pérot cavities crossing at the centre. The configuration allows the control not only of the resonance frequencies, but also a whole band gap and transmission band of frequencies between the directly excited diagonal and a higher frequency band. The second experiment demonstrates appearance of discrete Whispering Gallery Modes on a circle of re-entrant post. With the introduction of an artificial "scatterer", we demonstrate control over the doublet mode splitting.Single post re-entrant cavities 1,2 have found numerous applications in many areas of engineering and physics. Among engineering applications, one may also consider material science and chemistry applications where these structures have been used to probe dielectric and magnetic properties of gases, liquids and solids 3-6 .Re-entrant cavities have become a de-facto standard component in accelerator physics 7,8 . Other applications include microwave transducers for gravity wave detectors 9-11 and dark matter detection 12,13 , hybrid quantum systems 6,14-17 , plasma-assisted combustion 18,19 , microwave-enhanced chemistry 5 , fluid-gas sensing 20-22 , microfluidics 23,24 , tuneable filters 25 etc. More recently, higher order reentrant single-post cavity modes have been studied and considered for axion Dark matter experiments 26 . Performance of these types of cavities in all of these applications, as well as the list of applications itself may be enriched by further generalising the concept to multiple post re-entrant cavities. Although large scale multi-post multi-resonance structures have been analysed in detail with Finite Element Modeling (FEM), their physical implementation has not been demonstrated. In this work, we close this gap by investigating a 49 element mechanically controlled re-entrant cavity array and demonstrating it performance.A single post re-entrant cavity is a closed conducting structure with a metallic rod protruding from one cavity wall and leaving a small gap with the opposite one. The rod makes an equivalent inductance and the gap creates an equivalent capacitance. The resonance of these two quantities is highly tuneable with the gap size 1,2 . This can be done either mechanically through modifying the distance between the post and the opposite wall, for example with a piezoelectric device 27,28 , or electrically through changing electrical distance. A very large tuning range (over 1GHz or 19% of the resonance frequency) has been demonstrated in a re-entrant cavity a) Electronic

Macroscopic entanglement of two magnon modes via quantum correlated microwave fields

“…The system of two YIG spheres has been used to study magnon dark modes [29], high-order exceptional points [30], and entanglement properties between two magnon modes [25][26][27]. In each cavity, the magnon mode couples to the cavity mode via the magnetic dipole interaction, and this coupling can be very strong [1][2][3][4][5][6][7][8] thanks to the high spin density of YIG. The two cavities are driven by a two-mode squeezed vacuum microwave field.…”

“…In recent years, ferrimagnetic systems, like yttrium iron garnet (YIG), become an active and important platform for the study of strong interaction between light and matter, owing to their high spin density and low damping rate. Magnons, as collective excitations of a large number of spins, can strongly couple to cavity microwave photons [1][2][3][4][5][6][7][8] leading to cavity-magnon polaritons. The strong coherent interaction allows one to observe many interesting phenomena in cavity-magnon systems, such as the exceptional point [9], remote manipulation of spin currents [10], bistability [11], etc.…”

Magnon-Photon-Phonon Entanglement in Cavity Magnomechanics

“…In recent years ferrimagnetic systems, especially the yttrium iron garnet (YIG) sphere, have attracted considerable interest from the perspective of cavity quantum electrodynamics (QED). It is found that the Kittel mode [1] in the YIG sphere can realize strong coupling with the microwave photons in a high-quality cavity, leading to cavity polaritons [2][3][4][5][6] and the vacuum Rabi splitting. Thus many ideas originally developed in cavity QED can be applied to magnon cavity QED [7][8][9][10][11].…”

Squeezed states of magnons and phonons in cavity magnomechanics

“…Recent years have witnessed a significant progress of realizing strong light-matter interaction using collective excitations of spin ensembles in ferrimagnetic systems, for example in yttrium iron garnet (YIG), thanks to their very high spin density and low damping rate. The Kittel mode [1] (uniformly precessing mode) in the YIG sphere can strongly couple to the microwave cavity photons leading to cavity polaritons [2][3][4][5][6][7]. Many other interesting phenomena have been studied in the system of cavity-magnon polaritons, such as the observation of magnon dark modes [8], the exceptional point [9], manipulation of distant spin currents [10], and bistability [11].…”