Photon Phonon Research Articles

Anisotropic Laser Performance in an Optically Isotropic Crystal by Phonon Engineering

Symmetry is an eternal motif in understanding the characteristics of nearly all the laws and courses of science. The symmetry‐breaking in the optical crystal will generate a rich variety of unprecedented physical phenomena and create new functional properties. Herein, the symmetry‐breaking in a photon–phonon collaboratively pumped laser, dominated by the anisotropic lattice vibrations is investigated. Using an optically isotropic Nd:YAG crystal as an example, the phonon‐assisted electronic transitions accompanied by anisotropic fluorescence emission are observed, beyond the intrinsic structural symmetry ruled by Neumann's principle. For the first time, the phonon‐assisted new‐wavelength lasers at 1151 and 1166 nm are achieved in Nd:YAG with divergent light polarization, determined by the vibrational direction of involved phonons. These results provide a flexible degree of freedom for photonics by phonon engineering and pave the way to new frontiers in the field of laser generation and manipulation.

Nonreciprocal Photon Transport in a Chiral Optomechanical System

AbstractChiral interaction between light and quantum emitters leads to emergence development of chiral quantum optics and stimulates a wide range of practical applications in quantum regime, such as single‐photon isolation and photon unidirectional emission. Cavity optomechanics studying the interaction between optical and mechanical resonators plays an important role in the field of quantum optics. However, how to achieve the chiral interaction between light and mechanical oscillators and explore the applications of the chiral optomechanical systems are still difficult encountered in cavity optomechanics. Here, a method is proposed to achieve chiral optomechanical interaction by exploiting directional squeezed light in a multimode optomechanical system. Based on the chiral interaction between photon and phonon, the nonreciprocal photon transport at a single‐photon level can be realized. An isolation ratio of and a negligible insertion loss for the photonic isolator are obtained. This method paves the way to realize chiral optomechanical interaction for conducting chiral optomechanics and opens up the prospect of exploring and utilizing chiral photon–phonon manipulation in the quantum regime.

Electron–photon–phonon interactions in Dirac semimetals: Magneto-optical absorption and mobility analysis

We study the magneto-optical properties of Dirac semimetal (DSM) slabs with particular emphasis on Cd3As2 through electron–photon–phonon interactions, focusing on the magneto-optical absorption coefficient (MOAC) and full-width at half maximum (FWHM). Studying the Landau level (LL) energy of DSMs in the (xy) plane and the z-direction revealed a unique deviation from the square root dependence on the magnetic field, distinguishing DSMs from other semiconductors. At high magnetic fields, the electron–hole symmetry in the LL spectrum is broken, indicating a topological phase in DSMs. For undoped DSMs, MOAC is driven by interband transitions, with peaks from one-photon absorption being smaller and positioned to the left of two-photon ones. Increasing the magnetic field increases peak values. FWHM for one- and two-photon processes increases with the magnetic field and follows a T dependence on temperature. In doped DSMs, both intraband and interband transitions occur, with new interband peaks emerging at higher temperatures near the Fermi energy. Increased electron density shifts the peak position slightly toward higher energy. Peaks from optical phonon emission are consistently higher and located to the right of those from optical phonon absorption, indicating a stronger emission process. The FWHM data allow for the estimation of electron mobilities, and using a reasonable broadening parameter, our predicted mobility values agree with experimental results.

Unveiling vacuum fluctuations and nonclassical states with cavity-enhanced tripartite interactions

Enhancing and tailoring light–matter interactions offer remarkable nonlinear resources with wide-ranging applications in various scientific disciplines. In this study, strong and deterministic tripartite “beamsplitter” (“squeeze”) interactions are constructed by utilizing cavity-enhanced nonlinear anti-Stokes (Stokes) scattering within spin–photon–phonon degrees of freedom. We explore exotic dynamical and steady-state properties associated with the confined motion of a single atom within a high-finesse optical cavity. Notably, we demonstrate the direct extraction of vacuum fluctuations of photons and phonons, which are inherent in Heisenberg’s uncertainty principle, without requiring any free parameters. Moreover, our approach enables the realization of high-quality single-quanta sources with large average photon (phonon) occupancies. The underlying physical mechanisms responsible for generating the nonclassical quantum emitters are attributed to the decay-enhanced single-quanta blockade and long-lived motional phonons, resulting in strong nonlinearity. This work unveils significant opportunities for hitherto studying unexplored physical phenomena and provides novel perspectives on fundamental physics dominated by strong tripartite interactions.

Efficient methane oxidation to formaldehyde via photon–phonon cascade catalysis

The oxidation of methane to value-added chemicals provides an opportunity to use this abundant feedstock for sustainable petrochemistry. Unfortunately, such technologies remain insufficiently competitive due to a poor selectivity and a low yield rate for target products. Here we show a photon–phonon-driven cascade reaction that allows for methane conversion to formaldehyde with an unprecedented productivity of 401.5 μmol h−1 (or 40,150 μmol g−1 h−1) and a high selectivity of 90.4% at 150 °C. Specifically, with a ZnO catalyst decorated with single Ru atoms, methane first reacts with water to selectively produce methyl hydroperoxide via photocatalysis, followed by a thermodecomposition step yielding formaldehyde. Single Ru atoms, serving as electron acceptors, improve charge separation and promote oxygen reduction in photocatalysis. This reaction route with minimized energy consumption and high efficiency suggests a promising pathway for the sustainable transformation of light alkanes.

Signal, detection and estimation using a hybrid quantum circuit

We investigate a hybrid device allowing a photon–phonon coupling of a transmission line radiation (TLR) and a nanoeletromechanical system (NEMS), mediated by a superconducting qubit population imbalance. We demonstrate the derivation of an effective Hamiltonian for the strongly dispersive regime for this system. The qubit works as a quantum switch, allowing a conditioned transfer of excitations between the TLR and NEMS. We show that this regime allows the system to be employed for signal processing and force estimation. Additionally, we explore the ability of the quantum switch to generate non-classical states.

Atomic-like Autler–Townes splitting controlled by destructive and constructive natural non-Hermitian quantization in Eu3+: BiPO4

We report atomic-like Autler–Townes splitting controlled by destructive and constructive natural non-Hermitian quantization in Eu3+: BiPO4. For the first time, we explored destructive and constructive AT splitting in different regions. Fluorescence (FL), spontaneous four-wave mixing (SFWM), and shot noise signals exhibit different kinds of AT splitting. FL signal exhibits three level dip AT splitting through destructive quantization, SFWM signals exhibit peak and multi-dip AT splitting through constructive quantization, and shot noise signals exhibit a two-level dip AT splitting. These kinds of AT splitting originate through single photon dressing and double photon–phonon dressing, which can be controlled by adjusting experimental parameters. Our atomic-like Autler–Townes-splitting technique is useful for making a spectral router.

Photon–phonon entanglement and spin squeezing via dynamically strain-mediated Kerr nonlinearity in dressed nitrogen–vacancy centers

We propose a scheme to generate photon–phonon entanglement and spin squeezing in a hybrid system which is composed of the nitrogen–vacancy (NV) centers, nanomechanical resonator (NMR), and optical cavity. The triplet ground states of the NV centers which have been embedded in the middle of the clamped–clamped NMR are dressed by two strong microwave fields. Kerr nonlinearity is established by an applied microwave field and the vibrational modes of NMR coupling to the dressed-state transitions. The quantum correlations of the applied microwave field, vibrational mode, and NV centers are realized based on the parametric down-conversion-like and beam-splitter-like interactions in the hybrid system, which generate the photon–phonon entanglement and spin squeezing. In this nonlinear processes, the dynamically mediated strain of NMR, as a nonlinear switch, plays the central role in the establishment of such quantum correlations. Our scheme can be applied to quantum nondemolition measurement, quantum sensing, and quantum metrology.

Photo-thermo-optical modulation of Raman scattering from Mie-resonant silicon nanostructures

Abstract Raman scattering is sensitive to local temperature and thus offers a convenient tool for non-contact and non-destructive optical thermometry at the nanoscale. In turn, all-dielectric nanostructures, such as silicon particles, exhibit strongly enhanced photothermal heating due to Mie resonances, which leads to the strong modulation of elastic Rayleigh scattering intensity through subsequent thermo-optical effects. However, the influence of the complex photo-thermo-optical effect on inelastic Raman scattering has yet to be explored for resonant dielectric nanostructures. In this work, we experimentally demonstrate that the strong photo-thermo-optical interaction results in the nonlinear dependence of the Raman scattering signal intensity from a crystalline silicon nanoparticle via the thermal reconfiguration of the resonant response. Our results reveal a crucial role of the Mie resonance spectral sensitivity to temperature, which modifies not only the conversion of the incident light into heat but also Raman scattering efficiency. The developed comprehensive model provides the mechanism for thermal modulation of Raman scattering, shedding light on the photon–phonon interaction physics of resonant material, which is essential for the validation of Raman nanothermometry in resonant silicon structures under a strong laser field.

Enhanced Photon-Phonon Interaction in WSe2 Acoustic Nanocavities.

Acoustic nanocavities (ANCs) with resonance frequencies much above 1 GHz are prospective to be exploited in sensors and quantum operating devices. Nowadays, acoustic nanocavities fabricated from van der Waals (vdW) nanolayers allow them to exhibit resonance frequencies of the breathing acoustic mode up to f ∼ 1 THz and quality factors up to Q ∼ 103. For such high acoustic frequencies, electrical methods fail, and optical techniques are used for the generation and detection of coherent phonons. Here, we study experimentally acoustic nanocavities fabricated from WSe2 layers with thicknesses from 8 up to 130 nm deposited onto silica colloidal crystals. The substrate provides a strong mechanical support for the layers while keeping their acoustic properties the same as in membranes. We concentrate on experimental and theoretical studies of the amplitude of the optically measured acoustic signal from the breathing mode, which is the most important characteristic for acousto-optical devices. We probe the acoustic signal optically with a single wavelength in the vicinity of the exciton resonance and measure the relative changes in the reflectivity induced by coherent phonons up to 3 × 10-4 for f ∼ 100 GHz. We reveal the enhancement of photon-phonon interaction for a wide range of acoustic frequencies and show high sensitivity of the signal amplitude to the photoelastic constants governed by the deformation potential and dielectric function for photon energies near the exciton resonance. We also reveal a resonance in the photoelastic response (we call it photoelastic resonance) in the nanolayers with thickness close to the Bragg condition. The estimates show the capability of acoustic nanocavities with an exciton resonance for operations with high-frequency single phonons at an elevated temperature.

Thermal transport and optical anisotropy in CVD grown large area few-layer MoS2 over an FTO substrate

Atomically thin MoS2 is a promising candidate for its integration into devices due to its strikingly unique electronic, optical, and thermal properties. Here, we report the fabrication of a few-layer MoS2 thin film over a conducting fluorine-doped tin oxide-coated glass substrate via a one-step chemical vapor deposition method. We have quantitatively analyzed the nonlinear temperature-dependent Raman shift using a physical model that includes thermal expansion and three- and four-phonon anharmonic effects, which exhibits that the main origin of nonlinearity in both the phonon modes primarily arises from the three-phonon anharmonic process. We have also measured the interfacial thermal conductance (g) and thermal conductivity (ks) of the synthesized film using the optothermal Raman spectroscopy technique. The obtained values of g and ks are ∼7.218 ± 0.023 MW m−2 K−1 and ∼40 ± 2 W m−1 K−1, respectively, suggesting the suitability of thermal dissipation in MoS2 based electronic and optoelectronic devices. Furthermore, we performed a polarization study using the angle resolved polarized Raman spectroscopy technique under non-resonance and resonance excitations to reveal the electron–photon–phonon interaction in the prepared MoS2, based on the semi-classical theory that includes deformation potential and Fröhlich interaction. Our study provides much needed experimental information about thermal conductivity and polarization response in a few-layer MoS2 grown over the conducting substrate, which is relevant for applications in low power thermoelectric and optoelectronic devices.

Surface acoustic wave confinement inside uncorrelated distributions of subwavelength scatterers

We report an experimental study of surface acoustic wave (SAW) localization and propagation in random metasurfaces composed of Al scatters using pump–probe spectroscopy. Thanks to this technique, wideband high frequency acoustic modes are generated, and their dynamical propagation directly from inside of the media with a high (micrometric) spatial resolution is enabled. During SAW propagation, part of the acoustic wavefront energy is trapped within free areas between the scatterers, acting as cavities. The spectral content of the localized modes of a few GHz is found to depend on the shape and size of the cavities but also on the landscape seen by the wave during its propagation before arriving inside them. The experimental results are supported by numerical simulations using the finite element method. This study is the phononic part of a more global research on the co-localization of elastic and optical waves on random metasurfaces, with the main objective of enhancing the photon–phonon interaction. Applications could range from the design of acousto-optic modulators to ultrasensitive sensors.

Photothermal catalytic conversion of water and inert nitriles to amide activated by in-situ formed transition-metal-complex nanodots

Photothermal catalytic N-acetylation of aniline has been a promising strategy to synthesize amides, which combined the advantages of thermal catalysis and photocatalysis. Herein, we demonstrate a high-performance strategy to synthesize amides catalyzed by the in-situ formed first-row transition-metal (Fe, Co, Ni, Mn et al.) complexes nanodots (TMC NDs) under solar light excitation without using noble metals or strong acids. The dual-functional nitriles substrates acted as the ligands to coordinate with transition-metal salts affording photosensitive TMC NDs with high solar-to-thermal energy conversion efficiency. Intramolecular charge transitions reduced the energy barrier of nitriles activation by weakening CN bond and triggered near-field temperature rise via the electron–phonon scattering non-radiative pathway. The reaction system exhibited good tolerance to different functional groups, affording a series of amide derivatives. Such a dynamic coordination reaction mode and the in-situ formed TMC NDs opens new avenues toward solar-heat conversion via photon–phonon coupling in the field of chemical synthesis.

Generalized Rotating‐Wave Approximation for the Quantum Rabi Model with Optomechanical Interaction

AbstractThe spectrum of energy and eigenstates of an hybrid cavity optomechanical system, where a cavity field mode interacts with a mechanical mode of a vibrating end mirror via radiation pressure and with a two level atom via electric dipole interaction are investigated. In the spirit of approximations developed for the quantum Rabi model beyond rotating‐wave approximation (RWA), the so‐called generalized RWA (GRWA) to diagonalize the tripartite Hamiltonian for arbitrary large couplings is implemented. Notably, the GRWA approach still allows to rewrite the hybrid Hamiltonian in a bipartite form, like a Rabi model with dressed atom‐field states (polaritons) coupled to mechanical modes through reparametrized coupling strength and Rabi frequency. A more accurate energy spectrum for a wide range of values of the atom‐photon and photon–phonon couplings, when compared to the RWA results is found. The fidelity between the numerical eigenstates and its approximated counterparts is also calculated. The degree of polariton‐phonon entanglement of the eigenstates presents a non‐monotonic behavior as the atom‐photon coupling varies, in contrast to the characteristic monotonic increase in the RWA treatment.

Revealing the buildup of dynamic mode-switchable frequency-shifted feedback laser based on photon–phonon interaction

Photon-phonon interaction (PPI) is an intriguing physical phenomenon in which the dynamic photon-phonon energy transfer allows the manipulation of acousto-optic properties in the media. Recently, there has been significant interest of PPI as it accompanies the conservations of energy and momentum processes. Mode-locking is a process in which temporal and spatial resonant modes establish stable synchronization through non-linear interactions. Here, we propose and reveal the buildup of a dynamic mode-switchable frequency-shifted feedback laser in which frequency shift and mode conversion are achieved based on PPI. Moreover, dynamic switching between LP11a/b mode and stable donut mode output is achieved and precisely controlled by PPI. Finally, by using the time-stretch dispersive Fourier transform (TS-DFT) detective system, we observe the transient dynamics established in frequency-shifted feedback (FSF) fiber laser, such as the direct evolution from continuous wave (CW) state to mode-locked state, CW state to multipulse state and subsequently to stable mode-locked state. All these findings would unveil the buildup of mode-locking mechanisms of dynamic mode-switchable FSF fiber lasers based on PPI with more degrees of freedom and unlock new possibilities in ultrafast laser-based technology, optical communication and light control.

Optical Router and 4 × 1 Multiplexer of Coexisting Crystal Field and Non‐Hermitian Autler‐Townes Splitting Controlled by Photon–Phonon Dressing in Eu3+: BiPO4

AbstractFor the first time, the Autler Townes‐splitting dependency on parity‐time symmetry breaking is investigated. The first‐, second‐, and third‐order splitting in spectral domain outputs obtained through different phase transitions of Eu3+: BiPO4 are explored. First‐order splitting corresponds to pure crystal field splitting attributed to the shifting of energy levels and the inherent effect of the crystal field. Second/third‐order splitting results from the coexistence of crystal field and non‐Hermitian spectral Autler Townes (SAT)‐splitting caused by single‐photon dressing coupled with the interaction of phonon and double photon–phonon dressing. It is further explored the relationship between spectral and temporal‐domain splitting obtained through the different phases of Eu3+: BiPO4 by changing the laser detuning. It is authenticated that the contributions of crystal field, photon, and phonon dressing interactions can only be individually distinguished in the spectral domain. Moreover, the experiment results suggest the analogy of an optical 4 × 1 multiplexer with a channel spacing contrast of ≈91% and an optical router with a channel equalization ratio of ≈93%.

Heterogeneous optomechanical crystal cavity coupled by a wavelength-scale mechanical waveguide

Integrated optomechanical crystal (OMC) cavities provide a vital device prototype for highly efficient microwave to optical conversion in quantum information processing. In this work, we propose a novel heterogeneous OMC cavity consisting of a thin-film lithium niobate (TFLN) slab and chalcogenide (ChG) photonic crystal nanobeam coupled by a wavelength-scale mechanical waveguide. The optomechanical coupling rate of the heterogeneous OMC cavity is optimized up to 340 kHz at 1.1197 GHz. Combined with phononic band and power decomposition, 17.38% energy from the loaded RF power is converted into dominant fundamental horizontal shear mode (SH0) in the narrow LN mechanical waveguide. Based on this fraction, as a result, 3.51% power relative to the loaded RF energy is scattered into the fundamental longitudinal mode (L0) facing the TFLN-ChG heterogeneous waveguide. The acoustic breathing mode of the heterogeneous OMC is successfully excited under the driving of the propagating L0 mode in the heterogeneous waveguide, demonstrating the great potentials of the heterogeneous piezo-optomechanical transducer in high-performance photon–phonon interaction fields.

Efficient ultrafast photoacoustic transduction on Tantalum thin films

Nano-acoustic strain generation in thin metallic films via ultrafast laser excitation is widely used in material science, imaging and medical applications. Recently, it was shown that transition metals, such as titanium, exhibit enhanced photoacoustic transduction properties compared to noble metals, such as silver. This work presents experimental results and simulations that demonstrate that among transition metals tantalum exhibits superior photoacoustic properties. Experiments of nano-acoustic strain generation by femtosecond laser pulses focused on thin tantalum films deposited on Silicon substrates are presented. The nano-acoustic strains are measured via pump-probe transient reflectivity that captures the Brillouin oscillations produced by photon–phonon interactions. The observed Brillouin oscillations are correlated to the photoacoustic transduction efficiency of the tantalum thin film and compared to the performance of titanium thin films, clearly demonstrating the superior photoacoustic transduction efficiency of tantalum. The findings are supported by computational results on the laser-induced strains and their propagation in these thin metal film/substrate systems using a two-temperature model in combination with thermo-mechanical finite element analysis. Finally, the role of the metal transducer-substrate acoustic impedance matching is discussed and the possibility to generate appropriately modulated acoustic pulse trains inside the crystalline substrate structures for the development of crystalline undulators used for γ-ray generation is presented.

Enhanced entanglement via magnon squeezing in a two-cavity magnomechanical system

The present study is based on a theoretically feasible scheme for the enhancement of entanglement between different bipartitions due to magnon squeezing in a two-cavity magnomechanical system, having two microwave cavity mode photons, a magnon mode, and phonon mode. The nonlinearity in the system is well enhanced owing to magnon squeezing, which is responsible for the enhancement of different bipartitions’ entanglement. By employing the standard Langevin approach, we found that the magnon squeezing parameter not only enhances the entanglement between directly coupled modes, but also has a considerable impact on indirectly coupled modes’ entanglement. In addition, we find the negative impact of the thermal bath for the mechanical mode on the generation of photon–phonon and magnon–phonon entanglements. Furthermore, magnon squeezing has shown a significant role in the entanglement robustness against thermal effects. Moreover, the tripartite entanglement among photon, magnon, and phonon is also considerably enhanced in the presence of magnon squeezing. This two-cavity magnomechanical system might be used in quantum tasks that require the enhancement of entanglement of indirectly coupled modes.

Reservoir Engineering Strong Magnomechanical Entanglement via Dual‐Mode Cooling

AbstractA hybrid cavity magnomechanical system to transfer the bipartite entanglements and achieve the strong microwave photon–phonon entanglement based on the reservoir engineering approach is constructed. The magnon mode is coupled to the microwave cavity mode via magnetic dipole interaction and to the phonon mode via magnetostrictive force (optomechanical‐like). It is shown that the initial magnon‐phonon entanglement can be transferred to the photon‐phonon subspace in the case of these two interactions cooperating. In the reservoir‐engineering parameter regime, the initial entanglement is directionally transferred to the photon‐phonon subsystem, so a strong bipartite entanglement in which the magnon mode acts as the cold reservoir to effectively cool the Bogoliubov mode delocalized over the cavity and the mechanical deformation mode is obtained. Moreover, dual‐mode cooling is realized by engineering the dissipation of photon and phonon modes within the target mode, which allows entanglement to be further enhanced. The results indicate that the steady‐state entanglement is robust against temperature. The dual‐mode cooling reservoir engineering scheme can potentially be extended to other three‐mode quantum systems.