High-contrast absorption magnetometry in the visible to near-infrared range with nitrogen-vacancy ensembles

TL;DR

This paper demonstrates broadband optical absorption in NV centers from visible to near-infrared, enabling high-contrast magnetometry with improved sensitivity and opening new wavelength regimes for NV-based magnetic sensing.

Contribution

It introduces broadband absorption detection in NV centers using a high-finesse cavity, significantly enhancing ODMR contrast and sensitivity compared to traditional emission-based methods.

Findings

Achieved ODMR contrast up to 42% in the infrared range.

Reaching a sensitivity of 7.5 pT/√Hz with probe wavelength optimization.

Demonstrated broadband absorption extending from emission wavelength to 1000 nm.

Abstract

Magnetometry with nitrogen-vacancy (NV) centers has so far been measured via emission of light from NV centers or via absorption at the singlet transition at 1042 nm. Here, we demonstrate a phenomenon of broadband optical absorption by the NV centers starting in the emission wavelength and reaching up to 1000 nm. The measurements are enabled by a high-finesse cavity, which is used for room temperature continuous wave pump-probe experiments. The red to infrared probe beam shows the typical optically detected magnetic resonance (ODMR) signal of the NV spin with contrasts up to 42 %. This broadband optical absorption is not yet reported in terms of NV magnetometry. We argue that the lower level of the absorbing transition could be the energetically lower NV singlet state, based on the increased optical absorption for a resonant microwave field and the spectral behavior. Investigations of the photon-shot-noise-limited sensitivity show improvements with increasing probe wavelength, reaching an optimum of 7.5 pT/$\sqrt{\mathrm{Hz}}$. The results show significantly improved ODMR contrast compared to emission-based magnetometry. This opens a new detection wavelength regime with coherent laser signal detection for high-sensitivity NV magnetometry.