Robust frequency calibration of a large-area high-Q resonator in magnetic imaging with spin ensembles in diamond

Abstract

High-Q resonators with a large uniform field are widely used in magnetic imaging, but the microwave (MW) frequency shifts differently because of the near-field coupling. In this study, the major factors influencing of the frequency shifts were analyzed in a confocal system with nitrogen vacancy centers. We demonstrated a frequency calibration method involving adjustments of the applied magnetic field. This technique maintained the uniformity of the MW field with robustness to system noise, without changing the MW power. The effective imaging region reached 1.3 × 1.3 mm2 with a uniformity of 92.7%. This method preserves the stable operation of spin ensembles in magnetic imaging systems.

Microstrip-line resonator with broadband, circularly polarized, uniform microwave field for nitrogen vacancy center ensembles in diamond

“…4,5 The NVcenter ensemble is promising for magnetic measuring and temperature measuring devices 6,7 according to its extraordinary properties, such as long spin coherence time, 8 visible initialization and read-out 9 and microwave (MW) manipulation. 10,11 State manipulation 12 of the NVcenter ensembles through the MW field 13,14 provides strong technical support for measurement of the magnetic field. 14,15 However, the manipulation of the spin state relies on an applied bias magnetic field provided by Helmholtz coils in general, which is difficult to reduce the device volume.…”

Design of a High-Bandwidth Uniform Radiation Antenna for Wide-Field Imaging with Ensemble NV Color Centers in Diamond

“…The coordinates of the other four points are 2 (x = 0, y = −2.2), 4 (x = −2.2, y = 0), 6 (x = 0, y = 2.2), 8 (x = 2.2, y = 0), and these points to be simulated are in a uniform area. The calculation method of microwave field uniformity is equal to the standard deviation of microwave field intensity divided by the average value of microwave field intensity [ 29 , 31 ]. Clearly, the change of magnetic field intensity is about 5.86% in the area of 4.8 × 4.8 mm 2 , which is calculated with 625 pionts, and the data of 49 pionts on the x -axis and y -axis in the area are shown in Figure 2 b.…”

“…N. Zhang designed a square split ring resonator, where the microwave field uniformity in the effective imaging area of the resonator was 92.7%. However, its uniform area was only 1.3 × 1.3 mm 2 [ 29 ]. E. R. Eisenach proposed a loop gap resonator, which provides a 96.8% uniform MW drive for NV ensembles in a 32 mm 2 area, but the bandwidth is only 80 MHz [ 30 ].…”

System for the remote control and imaging of MW fields for spin manipulation in NV centers in diamond

“…For these applications, a precise spatial control of the MW field distribution is required to coherently drive single or ensembles of spins. In imaging and sensing applications, the commonly employed MW antennas have a large bandwidth and can generate uniform MW fields in a wide area 11,12 or in a 3D volume 13,14 . For quantum information, the area of interest is limited to few or single centers, for which high and more localized MW magnetic fields are preferred to drive the spin in an efficient way.…”