All-optical nonlinear phase modulation in open semiconductor microcavities

TL;DR

This work demonstrates ultra-low-power all-optical phase modulation between probe and control beams in an open-access semiconductor microcavity operating in the strong light-matter coupling regime, achieving a record per-polariton phase shift of $247\pm 17$ mrad and an absolute phase shift of $500$ mrad with as few as 10 control polaritons. The authors engineer a tightly confined polariton mode in a 17 nm InGaAs QW within a GaAs-based open cavity, attaining a vacuum Rabi splitting of $2.87\ \mathrm{meV}$ and a polariton linewidth near $50\ \mu\mathrm{eV}$ at high exciton content $|X|^2\approx0.54$. Using timed, polarization-resolved TCSPC measurements, they map phase shifts across detunings, polarizations, and intra-cavity energies, and identify a rapid frequency dependence potentially linked to biexciton resonances, while finding negligible reservoir effects on sub-300 ps timescales. This establishes a new benchmark for polariton-based cross-phase modulation on scalable semiconductor platforms and points toward practical quantum information processing devices using solid-state light-matter strongly coupled systems.

Abstract

We report a significant advancement in ultra low power light-by-light phase modulation using open semiconductor microcavities in the strong light-matter coupling regime. We achieve cross-phase modulation of up to 247$\pm$17 mrad per particle between laser beams attenuated to single-photon average intensities. This breakthrough extends the potential for quantum information processing and nonlinear quantum optics in strongly coupled light-matter systems, setting a new benchmark in the field without relying on atom-like emitters. Our findings suggest promising new avenues for scalable quantum optical technologies.

Figures (4)

• Figure 1: (a) Simplified schematic of the experimental setup. (b) White light transmission spectra as a function of the detuning between bare cavity mode ($C_{ph}$) and exciton ($X^0$) plotted in logarithmic colour scale. (c) Polariton linewidth extracted from the white light transmission measurements, as a function of the detunings of the cavity mode from the exciton resonance (blue curve) and calculated from the simulation (orange curve).
• Figure 2: (a) Example TCSPC traces recorded during a phase-shift measurement. The control-beam background has been subtracted. A and D denote the avalanche-photodiode detection channels measuring the two orthogonal polarisation components. $\sigma^{+}$ and $\sigma^{-}$ indicate the control-beam polarisation state. (b–d) Measured phase shift as a function of the control beam’s mean polariton number for different cavity–exciton detunings.
• Figure 3: (a) Phase shift per 1 polariton as a function of cavity–exciton detuning. (b) Dependence of phase shift on applied voltage of the EO amplitude modulator. The experimental data (black squares) are fitted with a sine function (orange line).
• Figure 4: (a) Phase shift dependence on time delay between probe and control pulses. (b) Control pulse (blue) and probe pulse for three different delays. Note that the pulse shapes are convolved with the timing jitter of the SPADs.