Coherent Phononic Control: Scope & Applications

• Coherent phononic control is a collection of techniques that actively generates, manipulates, and reads out phonons with precise phase relationships in both classical and quantum regimes.
• It employs advanced photonic, electronic, and optomechanical interactions to achieve functionalities such as high-Q filtering, coherent memory storage, and quantum state transfer in diverse architectures.
• Recent implementations in on-chip silicon photonic circuits and optomechanical cavities demonstrate scalable, multifunctional control over phononic and hybrid solid-state systems.

Coherent phononic control encompasses a suite of techniques and architectures for the active, phase-stable generation, manipulation, and readout of mechanical vibrations (phonons) in the classical and quantum regimes. This field leverages intricate photonic, electronic, and optomechanical interactions to realize tasks such as precision filtering, quantum state transfer, dynamical symmetry breaking, nonlinear lattice control, and ultrafast switching in photonic, phononic, and hybrid solid-state platforms. Theoretical foundations rely on driven coupled-mode equations, Brillouin and Raman scattering, anharmonic oscillator models, and topologically protected transport. Recent research has demonstrated that such control can be implemented on-chip in silicon photonic circuits, in optical fibers, in engineered quantum materials, and for single spins in diamond, with applications spanning telecommunications, information processing, quantum networks, ultrafast phase control, and new states of matter.

1. Fundamental Mechanisms of Coherent Phononic Control

Coherent phononic control fundamentally exploits the ability to generate, manipulate, and detect phonons with precise phase relationships over relevant temporal and spatial domains. Several principal schemes have been established:

• Traveling-wave photon–phonon transduction: In nanophotonic waveguides embedded in silicon phononic crystals, two spatially separated optical channels (emitter and receiver) are linked via traveling GHz phonons generated by optical modulation (forward-SBS), shaped and directed by engineered phononic crystals, and reconverted to optical signals at a remote site. The dynamics are captured by coupled-mode equations,

$$\frac{dC_{a}}{dt} = ( -i\Omega_0 - \frac{1}{\tau_\text{net}} )C_a + i\mu C_b + \eta(t), \quad \frac{dC_{b}}{dt} = ( -i\Omega_0 - \frac{1}{\tau_\text{net}} )C_b + i\mu C_a,$$

where $\Omega_0$ is the bare phononic frequency and $\mu$ the coupling rate (Shin et al., 2014).

• Stimulated Brillouin Scattering Memory: In planar waveguides, optical pulses coherently transfer both amplitude and phase information to hypersound phonons, where the group-velocity mismatch between light and sound enables long-term storage and multi-wavelength operation (Merklein et al., 2016).
• Phase-controlled phonon lasers: Coupled optomechanical cavities with embedded OPAs utilize controllable phase differences in external parametric drives to exponentially amplify photon–phonon interactions. The phase parameter $\Delta \Phi$ enables switching between radiation-pressure and three-mode coupling regimes, facilitating ultralow threshold phonon lasing (1706.02097).
• Coherent pumping and anharmonic control: Double-pulse excitations, as well as THz, optical, or feedback-based pulse trains, can prepare and coherently modulate large-amplitude phonon modes, pushing systems beyond the linear regime and unlocking nonlinear, amplitude-dependent dynamics in crystals (Scharf et al., 13 Mar 2025, Horstmann et al., 22 Aug 2025).

2. Device Architectures and Material Platforms

Device-level realization of coherent phononic control employs a variety of advanced structures:

Architecture Type	Key Features	Example Reference
Nanophotonic waveguides + phononic crystals	Spatially separated "emitter" and "receiver" waveguides; phononic crystal confinement; traveling-wave transduction	(Shin et al., 2014)
Planar chalcogenide waveguides	GHz Brillouin storage, negligible cross-talk, high Brillouin gain	(Merklein et al., 2016)
Fiber-based dual-nanoweb systems	Phase-tuned SRLS driving, uniform vibrational control	(Koehler et al., 2017)
Topologically protected phononic circuits	Monolithic plates with perforated holes, robust edge modes	(Yu et al., 2017)
Optomechanical cavities (OMCs)	Co-localized optical/mechanical modes; optical phonon switches	(Maire et al., 2018)
Photonic metasurfaces	Polarization-sensitive generation, acousto-plasmonic coupling	(Lanzillotti-Kimura et al., 2018)
Silicon phononic/photonic waveguides (CMOS)	Slot-waveguide optomechanics, 2D phononic crystal	(Madiot et al., 2022)
Levitated nanoparticles	Optical tweezer phonon lasers, coupled-mode Rabi dynamics	(Zhang et al., 15 Apr 2024)

Materials choices are tailored to bring out large optomechanical, piezoelectric, or strain-coupling coefficients. For memory/storage, high Brillouin gain is achieved in chalcogenide glasses (e.g. As₂S₃). Mechanical and optomechanical oscillators in Si, Si₃N₄, and diamond enable strong photon/phonon/spin interactions. Heavy-fermion materials (CeBi), van der Waals crystals (WTe₂, FePS₃), and quantum materials are selected for their strong coupling between lattice and electronic/magnetic order.

3. Applications in Information Processing, Sensing, and Signal Control

Coherent phononic control enables a diverse set of functionalities:

• RF-photonic filtering: Optical signals are transduced to phonons and back to realize wavelength-insensitive, high-power, narrow-linewidth filters with sharp roll-off (e.g., ~20 dB per 3.5 MHz), high Q-factors (~930), and deep stopband attenuation (~70 dB) in silicon (Shin et al., 2014).
• Coherent memory and delay: GHz-bandwidth storage of optical information is achieved in waveguide phononic memories, with phase and amplitude stored for durations set by acoustic lifetimes (∼10 ns) (Merklein et al., 2016). The process supports simultaneous multi-wavelength operation with negligible channel cross-talk.
• Quantum state transfer and phononic networks: In graphene mechanical resonator arrays, coherent Rabi oscillations and Ramsey interference between spatially separated nodes allow information to be transferred or stored via vibrational modes. Linear scaling of Rabi frequency with drive enables tunable, high-coherence information processing (Zhang et al., 2019).
• Switchable and addressable architectures: Phonon "switches" operating on MHz timescales, harmonic-to-chaos switching, and pixel-level selectivity in integrated OM networks allow dynamic information routing (Maire et al., 2018).
• Topological transport: Robust, low-loss phonon guiding and isolation from disorder (defect and bend immunity) are realized in topologically protected phononic waveguides—key for massive integration and high-fidelity signal processing (Yu et al., 2017).
• Thermal management: Coherent engineering of phonon band structure in 2D and 3D phononic crystals enables tuning of sub-Kelvin thermal conductance and thermal transport, with optimal suppression governed by the interplay of band flattening and surface scattering (Tian et al., 2019, Heiskanen et al., 2021).

4. Ultrafast and Nonlinear Phononic Control

Ultrafast optical and THz excitation provides dynamic control far from equilibrium:

• Anharmonic frequency modulation: Double pump–probe spectroscopy directly tracks amplitude-dependent phonon frequency shifts, resolving softening effects associated with bond extension and disentangling electronic, lattice, and anharmonic contributions in real time (Scharf et al., 13 Mar 2025).
• Overcoming amplitude saturation: Sequential in-phase optical excitation (double pulse) overcomes the amplitude bottleneck imposed by band-specific electron–phonon coupling, achieving higher lattice displacements for the same energy input and revealing strongly nonequilibrium anharmonic phonon–phonon coupling (Horstmann et al., 22 Aug 2025).
• Terahertz phase control of magnetization: Time-delayed THz pulses drive coherent IR-active phonons, which, through anharmonic coupling, induce Raman-active mode displacements that dynamically modulate metastable magnetization in FePS₃. Delay tuning enables constructive or destructive interference, switching the order parameter on picosecond timescales (Ilyas et al., 19 Oct 2025).

5. Quantum Control, Coherence Protection, and Hybrid Interfaces

Phonons serve as natural bridges between disparate quantum systems:

• All-mechanical dressed-state protection: Continuous acoustic driving generates strong spin dressing in a SiV center, yielding qubits largely immune to environmental magnetic noise. Quantum gates utilizing Rabi frequencies up to 800 MHz are demonstrated, and the dressed basis can be directly optically initialized and read out, enabling robust, cavity-compatible quantum operations (Cornell et al., 18 Aug 2025).
• Spin-phonon hybrid logic: Strain-sensitive solid-state spins coherently controlled by surface acoustic waves, with acoustically driven Ramsey sequences, allow pulse-level access to the phononic quantum interface (Maity et al., 2019).
• Multimode coherence sharing: In levitated nanoparticle tweezer phonon lasers, active feedback and dynamic coupling (via polarization modulation) transfer coherence between orthogonal vibrational modes, evolving initially thermal modes into coherent phonon lasers, foundational for quantum information storage and enhanced measurement (Zhang et al., 15 Apr 2024).

6. Current Challenges and Future Directions

• Bandwidth and loss engineering: Acoustic lifetimes, phononic crystal quality, and disorder must be controlled to maximize storage, filtering, and robust transmission. In memory devices, the current limit is set by acoustic decay times; in phononic crystals, diffusive scattering at boundaries sets the ultimate conduction limit.
• Scalability and integration: While architectures are compatible with CMOS processing and scalable nanofabrication, challenges remain for thermal management, cross-talk minimization, efficient input/output coupling, and high-fidelity scaling to large node or circuit counts.
• Nonlinear and nonequilibrium control: Exploiting anharmonicity enables access to nontrivial phase transitions, high-amplitude vibrational spectroscopy, and dynamic control of emergent quantum orders, but requires careful disentangling of various contributions and the development of novel excitation protocols.
• Quantum networking: Implementing high-fidelity, all-mechanical dynamical decoupling, enabling tunable spin–phonon interfaces, and realizing large-scale phonon-mediated quantum networks are active areas of research.
• Multifunctionality and hybridization: Coherent phononic control enables wavelength conversion, frequency multiplexing, quantum transduction between photons, spins, and electronics, and controlled switching in logic and memory elements.

In summary, coherent phononic control leverages interdisciplinary advances in photonics, mechanics, electronics, and materials science to manipulate lattice vibrations with precision and in real time. The results reported across multiple platforms demonstrate that both classical and quantum information can be encoded, transferred, and processed by coherent phonons, and offer new opportunities for functional devices, quantum technologies, and the dynamic engineering of matter well beyond equilibrium.