Pump-Enhanced Continuous-Wave Magnetometry Using Nitrogen-Vacancy Ensembles

Abstract

Ensembles of nitrogen-vacancy centers in diamond are a highly promising platform for high-sensitivity magnetometry, whose efficacy is often based on efficiently generating and monitoring magneticfield-dependent infrared fluorescence. Here, we report on an increased sensing efficiency with the use of a 532-nm resonant confocal cavity and a microwave resonator antenna for measuring the local magnetic noise density using the intrinsic nitrogen-vacancy concentration of a chemical-vapor deposited singlecrystal diamond. We measure a near-shot-noise-limited magnetic noise floor of 200 pT= ffiffiffiffiffiffi Hz p spanning a bandwidth up to 159 Hz, and an extracted sensitivity of approximately 3 nT= ffiffiffiffiffiffi Hz p , with further enhancement limited by the noise floor of the lock-in amplifier and the laser damage threshold of the optical components. Exploration of the microwave and optical pump-rate parameter space demonstrates a linewidth-narrowing regime reached by virtue of using the optical cavity, allowing an enhanced sensitivity to be achieved, despite an unoptimized collection efficiency of < 2%, and a low nitrogen-vacancy concentration of about 0.2 ppb.

Sensitivity optimization for NV-diamond magnetometry

“…Observed magnitudes of C absorb in the literature are lower than C fluor by ∼3 times (Bauch, 2010; Le Sage and Arai, 2011) or more. For example, (Ahmadi et al (2017(Ahmadi et al ( , 2018a(Ahmadi et al ( , 2018b) used a cw-ODMR-based magnetometer employing a resonant optical cavity to recycle the green excitation light through the diamond multiple times, and observed C fluor ∼ 0.01 (which is typical) while measuring C absorb ∼ 10 −6 . Ahmadi et al (2018a) performed magnetometry with the same experimental setup simultaneously using both green absorption and red fluorescence, as shown in , about 250 times better.…”

Continuous microwave hole burning and population oscillations in a diamond spin ensemble

“…Although this model represents the dynamics of a single N-V − spin, it successfully reproduces the measured spectrum of homogeneous low density N-V − ensembles [28,29]. In the case of inhomogeneity and the presence of significant impurity coupling, evident by the measurable P1 electron spin resonances in Fig.…”

“…[17], the shape and features of these oscillations across both dimensions (time and ∆ ω ) is set by both the measurement parameters and the intrinsic coherence times for the subensemble targeted by the probe field. These features and their relationships may be understood by attempting to reproduce the trends using a typical five-level model of the N-V − system [24,[27][28][29], while accounting for two coherent drives for the single ground state spin transition:…”

Colloquium : Quantum limits to the energy resolution of magnetic field sensors

“…We can then use (aa † + a † a)/2 = a † a + 1/2 = n + 1/2, which for the thermal state of the field at temperature T B has a value 1/2 (Muessel et al, 2014) BEC 2.5 × 10 −4 1.5 × 10 −6 1.5 × 10 −6 9.0 × 10 −17 · 1.9 × 10 −9 · 46 (Ahmadi et al, 2017) NVD 1.8 × 10 −5 1.8 × 10 −5 3.1 × 10 −3 3.5 × 10 −11 · 3.0 × 10 −9 · 47 (Kirtley, 2010) SQUID 6.5 × 10 −7 6.5 × 10 −7 · · 4.2 × 10 −13 · 1.8 × 10 −21 48 (Vasyukov et al, 2013) SQUID 1.6 × 10 −7 1.6 × 10 −7 · · 2.0 × 10 −14 · 1.0 × 10 −22 49 BEC 2.0 × 10 −6 2.0 × 10 −6 · · 4.0 × 10 −12 6.0 × 10 −9 · 50 (Wildermuth et al, 2004(Wildermuth et al, , 2005 BEC 3.0 × 10 −6 3.0 × 10 −6 3.0 × 10 −6 · · 2.2 × 10 −8 · 51 RFNVD 5.0 × 10 −7 5.0 × 10 −7 5.0 × 10 −7 · · 3.8 × 10 −8 · 52 (Vasyukov et al, 2013) SQUID 5.6 × 10 −8 5.6 × 10 −8 · · 2.5 × 10 −15 · 1.0 × 10 −22 53 RFNVD 4.0 × 10 −9 4.0 × 10 −9 · · 5.0 × 10 −17 · · 54 (Vasyukov et al, 2013) SQUID 4.6 × 10 −8 4.6 × 10 −8 · · 1.7 × 10 −15 · 1.0 × 10 −22 55 (Huang et al, 2014) GRA 1.6 × 10 −4 1.6 × 10 −4 · · · 1.0 × 10 −7 · 56 HALL 2.0 × 10 −7 2.0 × 10 −7 · · 4.0 × 10 −14 1.0 × 10 −7 · 57 RFNVD 3.0 × 10 −9 3.0 × 10 −9 · · 2.8 × 10 −17 · · 58 RFNVD 5.0 × 10 −9 5.0 × 10 −9 · · 7.9 × 10 −17 · · 59 (Forstner et al, 2014) WGM 4.0 × 10 −5 4.0 × 10 −5 4.0 × 10 −5 6.5 × 10 −14 · 1.4 × 10 −7 · 60 (Lima et al, 2014) MTJ 7.0 × 10 −6 7.0 × 10 −6 · · · 1.5 × 10 −7 · 61 RFNVD 5.0 × 10 −8 5.0 × 10 −8 5.0 × 10 −8 · · 2.9 × 10 −7 · 62 (Chenaud et al, 2016) HALL 1.0 × 10 −6 1.0 × 10 −6 · · · 3.0 × 10 −7 · 63 (Oral et al, 2002) HALL 1.5 × 10 −6 1.5 × 10 −6 · · · 6.0 × 10 −7 · 64 (Maletinsky et al, 2012) RFNVD 3.0 × 10 −9 3.0 × 10 −9 · · · 6.0 × 10 −6 · 65 (Kirtley, 2010) HALL 1.1 × 10 −7 1.1 × 10 −7 · · 1.2 × 10 −14 · 6.2 × 10 −18 66 (Kirtley, 2010) MFM 1.0 × 10 −8 1.0 × 10 −8 · · 1.0 × 10 −16 · 7.0 × 10 − 20 TABLE II Continuation of Table I.…”