Sideband Spectroscopy in the Strong Driving Regime: Volcano Transparency and Sideband Anomaly

TL;DR

This paper investigates the spectral response of spins under strong transverse and weak longitudinal magnetic fields, revealing unique phenomena like volcano-shaped spectra and sideband anomalies, supported by experimental data on diamond defects.

Contribution

It introduces a detailed analysis of sideband responses in the strong driving regime and uncovers novel spectral features and anomalies not previously characterized.

Findings

Identification of volcano lineshape with transparency region

Observation of sideband anomalies where resonances shift

Experimental validation with diamond defect emissions

Abstract

We study the response of a spin to two crossed magnetic fields: a strong and fast transverse field, and a weak and slow longitudinal field. We characterize the sideband response at the sum and the difference of driving frequencies over a broad range of parameters. In the strong transverse driving regime, the emission spectrum has a characteristic volcano lineshape with a narrow central transparency region surrounded by asymmetric peaks. Next, we couple the spin to a nonlinear cavity that both drives and measures it. In a sufficiently slow longitudinal field, the emission spectrum exhibits anomalous behavior, where the resonances in both the right and left sidebands lie on the same side of the central resonance. The theoretical results are compared to the experimental measurement of the emission of substitutional nitrogen P1 and nitrogen-vacancy NV$^-$ defects in diamond.