Group contributions at IONS KOALA and AIP

Ending 2022 with few conferences!

James, Shiro and Thomas are presenting their work at the IONS KOALA conference in Adelaide:

  • Shiromal Kumara, Michael J. Steel and Mikolaj K. Schmidt: Ensembles of quantum optical emitters,
  • James Bainbridge, Michael J. Steel and Mikolaj K. Schmidt: Quantum control of acoustic waves,
  • Thomas Dinter, Mikolaj K. Schmidt, Michael J. Steel: Anti-Resonant Reflecting Acoustic Rib Waveguides for opto-acoustics.

The following week, on top of these contributions, we’ll present a few more talks at the AIP Congree in Adelaide:

  • Álvaro Nodar, Ruben Esteban, Unai Muniain, Michael J. Steel, Javier Aizpurua and Mikolaj K. Schmidt: Statistics of light emitted from ultra-strongly coupled quantum systems, invited talk, (see blog entry on the recent preprint),
  • Mikolaj K. Schmidt, Daniel Burgarth, Gavin Brennen, Christopher G. Poulton, and Michael J. Steel, How to engineer optomechanical coupling using NV defects,
  • Oscar A. Nieves, Matthew D. Arnold, Mikolaj K. Schmidt, Michael J. Steel and Christopher G. Poulton, Modelling of noise in Brillouin-based storage and retrieval, (see blog entry on the recent papers),

and a poster from our recent graduate:

  • Saurabh Bhardwaj, Mikolaj K. Schmidt, Michael J. Withford and Michael J. Steel, Accurate modelling of femtosecond-laser direct written fibre Bragg gratings.

New prepring on the intensity correlations in ultra-strongly coupled systems

Spectrum of light emitted from a quantum system can tell us a lot about its dynamics, but to gain insight into its classical, or nonclassical nature, we need to measure other properties of the emission, like its intensity correlations.

In our new preprint Identifying unbound strong bunching and the breakdown of the Rotating Wave Approximation in the quantum Rabi model, in a work led by Alvaro Nodar from the Theory of Nanophotonics group in San Sebastian, we used the intensity correlations of light emitted from a quantum emitter-cavity system, to learn something about the breakdown of the Jaynes-Cummings model. Among other things, we learned that the intensity correlations are an extremely sensitive probe of this breakdown!

MQ Faculty of Science and Engineering ECR Retreat!

Together with Amy Cain adn Vera Horigue, we’ve organised a one-day retreat for about 45 of the ECRs (Early Career Researchers) from the Faculty of Science and Engineering at Macquarie University, in a lovely Quarantine Station in Sydney.

James and Shiro thesis submissions!

My two MRes (Master of Research) students have submitted their theses:

  • James Bainbridge worked on “Quantum control of acoustic waves”; he worked on the idea of using strain-coupled transitions in NV centres in diamond to control the dissipation and dispersion of propagating acoustic modes and cavity modes.
  • Shiromal Kumara’s thesis is on “The emergence of subradiance in ensembles of quantum optical emitter”; Shiro developed a nifty little code to calculate the dissipation from specific states of small ensembles of two-level systems.

Both Shiro and James were co-supervised by Prof. Michael J. Steel.

Fingers crossed!

Chapter “The convergence of cavity optomechanics and Brillouin scattering” is published!

Our chapter on the convergence of fields of Brillouin scattering and cavity optomechanics with Christopher Baker, and Raphael Van Laer is finally out in Semiconductors and Semimetals:

This will be published in a collection edited by Michael J. Steel, Christopher G. Poulton, and Benjamin Eggleton, celebrating a century of Brillouin and Mandelstam discoveries.

Discovery Early Career Researcher Award (DECRA) ’22-’25!

I was awarded a highly competitive Discovery Early Career Researcher Award (DECRA) by the Australian Research Council!

The project, set to begin in late 2022 and last for 3 years, will be focused on developing quantum acoustic devices and protocols for quantum communication, novel acoustic sources, and sensing.

Probing the optical response of nanoantennas by vortex electron beams

A new result from a long-standing collaboration with my colleagues from Donostia-San Sebastian: Andrea Konecna (now at Brno University of Technology in Czech Republic), Rainer Hillenbrand, and Javier Aizpurua: in arXiv:2111.08810 we looked at the possiblity of near-field probing of electric and magnetic resonant modes in high-refractive-index nanoantennas with focused electron beams.

Electron microscopy forms a versatile set of tools for interrogating the physical, and chemical properties of nanosystems. In particular, in Electron Energy Loss Spectroscopy (EELS), electron beams are used as broadband sources of electromagnetic waves to map out the optical response of the surroundings (see Fig. 1(a)) – specifically, the electric component of the Local Density of States (e-LDOS).

Over the last decade, the ultra-high spatial resolution offered by EELS was complemented by increasing its spectral resolution, and efficient coupling to electron‑beam‑forming optics [Phys. Rev. Lett. 126, 123901 (2021)]. Another recent innovation in electron microscopy was the introduction of Vortex Electron Beams (VEBs) made up of electrons with large Orbital Angular Momentum [Nature 467, 301 (2010); Rev. Mod. Phys. 89, 035004 (2017)]. In VEBs, the circulating electrons create an effective magnetic current Jm, which can probe the magnetic LDOS, complementing the capabilities of the standard EELS (see Fig. 1(b)).

In this work we introduce a full quantum‑mechanical description of the magnetic EELS. This treatment allows us to account for the considerable spatial extension of the electrons, or the interference between the electric and magnetic currents [Phys. Rev. Lett. 113, 066102 (2014); Opt. Express 20, 15024 (2012)]. We then identify the semi‑classical limit of this problem to build a complete analogy with the EELS technique. Finally, we show how the magnetic EELS can interrogate the magnetic response of several 2D and 3D systems of interest in nanophotonics: dielectric nanoantennas, waveguides, and simple chiral structures.

Addressing picosecond and noisy Brillouin scattering

A few students-led projects investigating the effects of noise and (very) short pulse lengths finally bore fruits, with 3 papers on SBS published:

In Noise and pulse dynamics in backward stimulated Brillouin scattering Optics Express 29 (3), 3132-3146 (2021), and Numerical simulation of noise in pulsed Brillouin scattering J. Opt. Soc. Am. B 38 (8), 2343-2352 (2021), we (in a collaboration led by the University of Technology Sydney) considered the general problem of thermal and laser phase noise in SBS, and devised analytical and numerical methods to calculate how they impact the resulting signal.

In Picosecond acoustic dynamics in stimulated Brillouin scattering Optics Letters 46 (12), 2972-2975 (2021), we (in a collaboration with the University of Technology Sydney and Max-Planck Institute for Light) analyzed the limits of SBS induced by optical pulses of length comparable to the period of acoustic oscillations. We found that when two short optical pulses collide in a waveguide, they can excite an acoustic wave with a well-defined momentum, but no frequency info i.e. no hint on which way to propagate!

Intensity correlations in optomechanics in Quantum Science and Technology

UPDATE (13/6/2021): The paper’s now published in Quantum Science and Technology 6, 034005 (2021)

Measuring intensity correlation (g(2)) of light emitted from a quantum system is Quantum Optics 101.

But what if you want to measure intensity correlations within a specific spectral window? Say, to consider correlations between particular transitions within your quantum system?

And what if that quantum system was a nontrivial and nonlinear one, like an optomechanical cavity, which can exhibit both optical Kerr nonlinearity and mutli-phonon transitions?

We try to answer, or at least approach all of this questions in the new manuscript: “Frequency-resolved photon correlations in cavity optomechanics”, arXiv:2009.06216 (2020), co-authored with people who taught me everything I know about classical and quantum nanooptics – Ruben Esteban, Javier Aizpurua, Geza Giedke and Alejandro Gonzalez-Tudela.

“Acoustic diamond resonators with ultra-small mode volumes” in Physical Review Research!

New manuscript on (deeply!) subwavelength acoustic GHz cavities for C>1 coupling with NVs with@magneticlemur and @cg_poulton is finally published by Physical Review Research (Phys. Rev. Research 2, 033153 (2020))! It is also available on arXiv

In this project we wanted to learn if one can acoustic mode into a subwavelength cavity, as we would in plasmonics. Or, recently, dielectric PC cavities – check these gems out here: (Weiss group @VandyPhysics), (@Dirk_Englund group). Inspired by these ideas, and the late-night reading of Landau&Lifschitz we played around with an acoustic analogue of the lightning rod effect. Wrapping it into a phononic crystal, we found modes with non-resonant reduction of mode volumes towards 1e-4 lambda^3!

Putting an NV in the centre of the structure (check out this awesome review from A. Jayich group @UCSBPhysics:, we arrived as > 1 MHz orbit-phonon couplings, and cooperativities > 1. We also compare our results to an awesome (and underplayed?) result on resonant localization in the flapping modes highlighted by Meesala et al. from @MeteAtature and Loncar lab @harvardphysics

What are the limits of this effect? Are there other, more efficient mechanisms for non-resonant localization? How does Veff scale against the Q of acoustic resonators? I’m eager to find out, and will keep you posted.