More Like this

1. Shaping nonlinear optical response using nonlocal forward Brillouin interactions

   https://doi.org/10.1088/1367-2630/ab73c8  

   Gertler, Shai ; Kharel, Prashanta ; Kittlaus, Eric A. ; Otterstrom, Nils T. ; Rakich, Peter T. ( April 2020 , New Journal of Physics)

   In most practical scenarios, optical susceptibilities can be treated as a local property of a medium. For example, in the context of nonlinear optics we can typically treat the Kerr and Raman response as local, such that optical fields at one location do not produce a nonlinear response at distinct locations in space. This is because the electronic and vibrational disturbances produced within the material are confined to a region that is smaller than an optical wavelength. By comparison, Brillouin interactions, mediated by traveling-wave acoustic phonons, can result in a highly nonlocal nonlinear response as the elastic waves generated in the process can occupy a region in space much larger than an optical wavelength. The unique properties of these interactions can be exploited to engineer new types of processes, where highly delocalized phonon modes serve as an engineerable channel that mediates scattering processes between light waves propagating in distinct optical waveguides. These types of nonlocal optomechanical responses have recently been demonstrated as the basis for information transduction, however the nontrivial dynamics of such systems has yet to be explored. In this work, we show that the third-order nonlinear process resulting from spatially extended Brillouin-active phonon modes involves mixing products from spatially separated, optically decoupled waveguides, yielding a nonlocal susceptibility. Building on these concepts, we illustrate how nontrivial multi-mode acoustic interference can produce a nonlocal susceptibility with a multi-pole frequency response, as the basis for new optical and microwave signal processing schemes within traveling wave systems.

    

   more » « less
2. Influence of Mode Structure on the Generation of Phononic Frequency Combs

   Zhen Qi, Curtis R. ( March 2020 , ArXivorg)

   The mechanical analog of optical frequency combs, phononic frequency combs, has recently been demonstrated in mechanical resonators and has been attributed to coupling between multiple phonon modes. This paper investigates the influence of mode structure on comb generation using a model of two nonlinearly coupled phonon modes. The model predicts that there is only one region within the amplitude-frequency space where combs exist, and this region is a subset of the Arnold tongue that describes a 2:1 autoparametric resonance between the two modes. In addition, the location and shape of the comb region are analytically defined by the resonance frequencies, quality factors, mode coupling strength, and detuning of the driving force frequency from the mechanical resonances, providing clear conditions for comb generation. These results enable comb structure engineering for applications in areas as broad as sensing, communications, and quantum information science. 

   more » « less
3. Coherent helicity-dependent spin-phonon oscillations in the ferromagnetic van der Waals crystal CrI3

   https://doi.org/10.1038/s41467-022-31786-3  

   Padmanabhan, P. ; Buessen, F. L. ; Tutchton, R. ; Kwock, K. W. C. ; Gilinsky, S. ; Lee, M. C. ; McGuire, M. A. ; Singamaneni, S. R. ; Yarotski, D. A. ; Paramekanti, A. ; et al ( August 2022 , Nature Communications)

   The discovery of two-dimensional systems hosting intrinsic magnetic order represents a seminal addition to the rich landscape of van der Waals materials. CrI₃is an archetypal example, where the interdependence of structure and magnetism, along with strong light-matter interactions, provides a new platform to explore the optical control of magnetic and vibrational degrees of freedom at the nanoscale. However, the nature of magneto-structural coupling on its intrinsic ultrafast timescale remains a crucial open question. Here, we probe magnetic and vibrational dynamics in bulk CrI₃using ultrafast optical spectroscopy, revealing spin-flip scattering-driven demagnetization and strong transient exchange-mediated interactions between lattice vibrations and spin oscillations. The latter yields a coherent spin-coupled phonon mode that is highly sensitive to the driving pulse’s helicity in the magnetically ordered phase. Our results elucidate the nature of ultrafast spin-lattice coupling in CrI₃and highlight its potential for applications requiring high-speed control of magnetism at the nanoscale.

    

   more » « less
4. Coherently Coupled Mechanical Oscillators in the Quantum Regime

   https://doi.org/10.21203/rs.3.rs-1774123/v1  

   Hou, P-Y. ; Wu, J.J. ; Erickson, S.D. ; Cole, D.C. ; Zarantonello, G. ; Brandt, A.D. ; Wilson, A.C. ; Slichter, D.H. ; Leibfried, D. ( July 2022 , ArXivorg)

   Coupled harmonic oscillators are ubiquitous in physics and play a prominent role in quantum science. They are a cornerstone of quantum mechanics and quantum field theory, where second quantization relies on harmonic oscillator operators to create and annihilate particles. Descriptions of quantum tunneling, beamsplitters, coupled potential wells, "hopping terms", decoherence and many other phenomena rely on coupled harmonic oscillators. Despite their prominence, only a few experimental systems have demonstrated direct coupling between separate harmonic oscillators; these demonstrations lacked the capability for high-fidelity quantum control. Here, we realize coherent exchange of single motional quanta between harmonic oscillators -- in this case, spectrally separated harmonic modes of motion of a trapped ion crystal where the timing, strength, and phase of the coupling are controlled through the application of an oscillating electric field with suitable spatial variation. We demonstrate high-fidelity quantum state transfer, entanglement of motional modes, and Hong-Ou-Mandel-type interference. We also project a harmonic oscillator into its ground state by measurement and preserve that state during repetitions of the projective measurement, an important prerequisite for non-destructive syndrome measurement in continuous-variable quantum error correction. Controllable coupling between harmonic oscillators has potential applications in quantum information processing with continuous variables, quantum simulation, and precision measurements. It can also enable cooling and quantum logic spectroscopy involving motional modes of trapped ions that are not directly accessible. 

   more » « less
5. Electronic-vibrational density evolution in a perylene bisimide dimer: mechanistic insights into excitation energy transfer

   https://doi.org/10.1039/D1CP02135D  

   Kundu, Sohang ; Makri, Nancy ( July 2021 , Physical Chemistry Chemical Physics)

   null (Ed.)

   The process of excitation energy transfer (EET) in molecular aggregates is etched with the signatures of a multitude of electronic and vibrational time scales that often are extremely difficult to resolve. The effect of the motion associated with one molecular vibration on that of another is fundamental to the dynamics of EET. In this paper we present simple theoretical ideas along with fully quantum mechanical calculations to develop a comprehensive mechanistic picture of EET in terms of the time evolution of electronic-vibrational densities (EVD) in a perylene bisimide (PBI) dimer, where 28 intramolecular normal modes couple to the ground and excited electronic states of each molecule. The EVD motion exhibits a plethora of dynamical features, which impart physical justification for the composite effects observed in the EET dynamics. Weakly coupled vibrations lead to classical-like motion of the EVD center on each electronic state, while highly nontrivial EVD characteristics develop under moderate or strong exciton–vibration interaction, leading to the formation of split or crescent-shaped densities, as well as density retention that slows down energy transfer and creates new peaks in the electronic populations. Pronounced correlation effects are observed in two-mode projections of the EVD, as a consequence of indirect vibrational coupling between uncoupled normal modes induced by the electronic coupling. Such indirect coupling depends on the strength of exciton–vibration interactions as well as the frequency mismatch between the two modes and leaves nontrivial signatures in the electronic population dynamics. The collective effects of many vibrational modes cause a partial smearing of these features through dephasing. 

   more » « less