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Register a new userElectrically driven exciton-polariton optomechanics at super high frequencies
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Added by
Alexander Kuznetsov
Publication date
2020
fields
Physics
and research's language is
English
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Polaritons enable the resonant coupling of excitons and photons to vibrations in the application-relevant super high frequency (SHF, 3-30 GHz) domain. We introduce a novel platform for coherent optomechanics based on the coupling of exciton-polaritons and electrically driven SHF longitudinal acoustic phonons confined within the spacer region of a planar Bragg microcavity. An intrinsic property of the microcavity platform is the back-feeding of phonons via reflections at the sample boundaries, which enables frequency x quality factors products exceeding 10^14 Hz as well as huge modulation amplitudes of the optical transition energies (up to 8 meV). We show that the modulation is dominated by the phonon-induced energy shifts of the excitonic polariton component, thus leading to an oscillatory transition between the regimes of weak and strong light-matter coupling. These results open the way for polariton-based coherent optomechanics in the non-adiabatic, side-band-resolved regime of coherent control.
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Semiconducting transition-metal dichalcogenides (TMDCs) provide a fascinating discovery platform for strong light-matter interaction effects in the visible spectrum at ambient conditions. While most of the work has focused on hybridizing excitons with resonant photonic modes of external mirrors, cavities, or nanostructures, intriguingly, TMDC flakes of sub-wavelength thickness can themselves act as nanocavities. Here, we determine the optical response of such freestanding planar waveguides of WSe$_2$, by means of cathodoluminescence spectroscopy. We reveal strong exciton-photon interaction effects that foster long-range propagating exciton-polaritons and enable direct imaging of the energy transfer dynamics originating from cavity-like Fabry-Perot resonances. Furthermore, confinement effects due to discontinuities in the flakes are demonstrated as an efficient means to tailor the exciton-photon coupling strength, along the edges of natural flakes. Our combined experimental and theoretical results provide a deeper understanding of exciton-photon self-hybridization in semiconducting TMDCs and may pave the way to optoelectronic nanocircuits exploiting exciton-photon interaction.
We study the cavity mode frequencies of a Fabry-Perot cavity containing two vibrating dielectric membranes. We derive the equations for the mode resonances and provide approximate analytical solutions for them as a function of the membrane positions, which act as an excellent approximation when the relative and center-of-mass position of the two membranes are much smaller than the cavity length. With these analytical solutions, one finds that extremely large optomechanical coupling of the membrane relative motion can be achieved in the limit of highly reflective membranes when the two membranes are placed very close to a resonance of the inner cavity formed by them. We also study the cavity finesse of the system and verify that, under the conditions of large coupling, it is not appreciably affected by the presence of the two membranes. The achievable large values of the ratio between the optomechanical coupling and the cavity decay rate, $g/kappa$, make this two-membrane system the simplest promising platform for implementing cavity optomechanics in the strong coupling regime.
Polaritons formed by the coupling of light and material excitations such as plasmons, phonons, or excitons enable light-matter interactions at the nanoscale beyond what is currently possible with conventional optics. Recently, significant interest has been attracted by polaritons in van der Waals materials, which could lead to applications in sensing, integrated photonic circuits and detectors. However, novel techniques are required to control the propagation of polaritons at the nanoscale and to implement the first practical devices. Here we report the experimental realization of polariton refractive and meta-optics in the mid-infrared by exploiting the properties of low-loss phonon polaritons in isotopically pure hexagonal boron nitride (hBN), which allow it to interact with the surrounding dielectric environment comprising the low-loss phase change material, Ge$_3$Sb$_2$Te$_6$ (GST). We demonstrate waveguides which confine polaritons in a 1D geometry, and refractive optical elements such as lenses and prisms for phonon polaritons in hBN, which we characterize using scanning near field optical microscopy. Furthermore, we demonstrate metalenses, which allow for polariton wavefront engineering and sub-wavelength focusing. Our method, due to its sub-diffraction and planar nature, will enable the realization of programmable miniaturized integrated optoelectronic devices, and will lay the foundation for on-demand biosensors.
Nanophotonic structures in single--crystal diamond (SCD) that simultaneously confine and co-localize photons and phonons are highly desirable for applications in quantum information science and optomechanics. Here we describe an optimized process for etching SCD microdisk structures designed for optomechanics applications. This process allows the optical quality factor, $Q$, of these devices to be enhanced by a factor of 4 over previous demonstrations to $Q sim 335,000$, which is sufficient to enable sideband resolved coherent cavity optomechanical experiments. Through analysis of optical loss and backscattering rates we find that $Q$ remains limited by surface imperfections. We also describe a technique for altering microdisk pedestal geometry which could enable reductions in mechanical dissipation.
An infinite chain of driven-dissipative condensate spins with uniform nearest-neighbor coherent coupling is solved analytically and investigated numerically. Above a critical occupation threshold the condensates undergo spontaneous spin bifurcation (becoming magnetized) forming a binary chain of spin-up or spin-down states. Minimization of the bifurcation threshold determines the magnetic order as a function of the coupling strength. This allows control of multiple magnetic orders via adiabatic (slow ramping of) pumping. In addition to ferromagnetic and anti-ferromagnetic ordered states we show the formation of a paired-spin ordered state $left|dots uparrow uparrow downarrow downarrow dots right. rangle$ as a consequence of the phase degree of freedom between condensates.
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