Ultrafast modulation of vibrational polaritons for controlling the quantum field statistics at mid-infrared frequencies

Abstract

Controlling the quantum field statistics of confined light is a long-standing goal in integrated photonics. We show that by coupling molecular vibrations with a confined mid-infrared cavity vacuum, the photocount and quadrature field statistics of the cavity field can be reversibly manipulated over sub-picosecond timescales. The mechanism involves changing the cavity resonance frequency through a modulation of the dielectric response of the cavity materials using femtosecond UV pulses. For a single anharmonic molecular vibration in an infrared cavity under ultrastrong coupling conditions, the pulsed modulation of the cavity frequency can adiabatically produce mid- infrared light that is simultaneously sub-Poissonian and quadrature squeezed, depending on the dipolar behavior of the vibrational mode. For a vibration-cavity system in strong coupling, non-adiabatic polariton excitations can be produced after the frequency modulation pulse is over, when the system is initially prepared in the lower polariton state. We propose design principles for the generation of mid-infrared quantum light by analyzing the dependence of the cavity field statistics on the shape of the electric dipole function of the molecule, the cavity detuning at the modulation peak and the anharmonicity of the Morse potential. Feasible experimental implementations of the modulation scheme are suggested. This work paves the way for the development of molecule-based mid-infrared quantum optical devices at room temperature.

Cavity-Modified Unimolecular Dissociation Reactions via Intramolecular Vibrational Energy Redistribution

“…In the following, we will consider interactions with a single cavity mode c . The permanent dipole moment of the molecule, plotted in Figure 1 b, is defined as where , , , 48 θ is the angle between the x -axis and the in-plane molecular axis through the center of the molecule, σ = 1 bohr controls the envelope width, and A = 0.4 e is such that the equilibrium permanent dipole moment μ 0 in the x -direction when θ = 0 is 1 e·bohr, which is on the order of the permanent dipole moment for bent triatomic molecules such as ozone. 49 , 50 Importantly, the dipole moment μ approaches zero with increasing q 1 and q 2 , physically analogous to dissociation into neutral species or screening of ionic fragments by solvent, to obviate challenges with the dipole approximation after dissociation.…”

Self-Dissociation of Polar Molecules in a Confined Infrared Vacuum

“…(1) using the multi-configuration time-dependent Hartree (MCTDH) method [32], to propagate the polariton wave function in coordinate space. MCTDH and its extensions have been used successfully in strongly coupled systems to describe photochemistry in free space [33] and more recently for studying molecular polaritons [7,[34][35][36]. The MCTDH wavefunction ansatz for the molecular and photonic degrees of freedom is given by…”

“…3. The polariton GS is generally a superposition of uncoupled states |ν⟩|n⟩ with potentially high quantum numbers ν and n, depending on the value of λ g [7,36]. The GS energy is red-shifted relative to the uncoupled ground energy, and can be estimated directly in the polaron frame from the Bloch-Siegert shift of the ground vibrational level η 0 in Eq.…”

Ultrafast CO2 photodissociation in the energy region of the lowest Rydberg series

“…13 For instance, some of us recently used this code to solve ab initio polariton photodynamics of diatomic molecules. [34][35][36][37] In our grid-based calculations the degree of freedom R corresponding to the bond distance CO is represented with a sin-DVR primitive basis using 1061 grid points between R = 1.7 bohr and R = 7.0 bohr. We perform multistate calculations by including the set of six Fig.…”