Nitrogen-vacancy (NV) centers in diamond are a promising platform for high-precision magnetometry. In contrast to the use of spontaneous emission in a number of NV-magnetometers, laser threshold magnetometry (LTM) exploits stimulated emission of NV centers by placing an NV-doped diamond inside an optical cavity. The NV laser system is predicted to reach a high magnetic-field-dependent contrast and coherent signal strength, leading to an improved magnetic field sensitivity combined with a high linearity. Here, we consider a two-media setup where the cavity additionally includes a vertical external cavity surface emitting laser. This optically active material compensates cavity losses at \SI{750}{nm} while still allowing for magnetic-field-dependent effects from the NV-diamond. We demonstrate a magnetic-field-dependent laser threshold and investigate the effects of pump laser induced absorption of the diamond. The experimental data is supported by an analytical simulation based on a rate model. Furthermore, we derive a generalized formula to compute the shot-noise-limited magnetic field sensitivity in the regime of high contrast yielding 49.07(33) pT/Hz for the present setup. Simulations with an optimized NV-diamond suggest that values down to 4.9 ft/Hz are possible.
@article{arxiv.2504.08466,
title = {Two-media laser threshold magnetometry: A magnetic-field-dependent laser threshold},
author = {Yves Rottstaedt and Lukas Lindner and Florian Schall and Felix A. Hahl and Tingpeng Luo and Florentin Reiter and Takeshi Ohshima and Alexander M. Zaitsev and Roman Bek and Marcel Rattunde and Jan Jeske and Rüdiger Quay},
journal= {arXiv preprint arXiv:2504.08466},
year = {2025}
}