A High-Efficiency, Single Port h-BN Sensor Chip with Easy Integration and High Optical Readout

The past decade has witnessed several demonstrations on quantum sensing using solid-state spin-active boron vacancies in hexagonal boron nitride (h-BN).^[1] Some of the primary figures of merit for a functional sensor device include the easy chip integration of h-BN, energy efficiency and a high signal to noise ratio (SNR), which remains challenging. Due to the inherently low brightness of defects, a conventional optically detected magnetic resonance (ODMR) experimental setup requires a high laser flux and/or microwave power to achieve sufficiently high contrast. Hence, this introduces a significant risk of diminished resolution owing to heating effects, increased noise levels, and potential damage to the sample. Additionally, for ODMR experiments, the commonly employed cavity resonators,^[2] and two-port coplanar waveguides or striplines ^{[1] [2] [3] [4]} are not feasible for incorporation into compact sensor designs.<br/>This work presents a novel quantum sensor chip utilizing h-BN on a compact gold shorted co-planar waveguide on a transparent sapphire substrate. The chip integrated with h-BN enables on-chip optical and microwave excitation, enhancing quantum magnetometry's practicality and sensitivity. Compared to conventional chips, our device offers improved impedance stability and radio frequency (RF) magnetic field concentration.^[1] As a result, our quantum sensor chip demonstrates an exceptionally high ODMR contrast of ~28% in response to the microwave (MW) power of 200 mW, and a high optical readout (several thousand PL counts/msec). This miniaturized chip reduces device size, enhances performance efficiency, and facilitates sensor performance with reduced power loss and signal reflection. Overall, our integrated quantum sensor chip design presents a significant advancement in scalable, efficient quantum sensors applicable to various fields, including external magnetic field sensing and ion detection. The work on improving the quantum sensitivity of hBN quantum sensor is ongoing.<br/><br/><b>References</b><br/>[1]<br/>X. Gao, B. Jiang, A. E. Llacsahuanga Allcca, K. Shen, M. A. Sadi, A. B. Solanki, P. Ju, Z. Xu, P. Upadhyaya, Y. P. Chen, S. A. Bhave and T. Li, "High-Contrast Plasmonic-Enhanced Shallow Spin Defects in Hexagonal Boron Nitride for Quantum Sensing," <i>Nano Letters, </i>vol. 21, p. 7708–7714, September 2021.<br/><br/>[2]<br/>A. Gottscholl, M. Diez, V. Soltamov, C. Kasper, D. Krauße, A. Sperlich, M. Kianinia, C. Bradac, I. Aharonovich and V. Dyakonov, "Spin defects in hBN as promising temperature, pressure and magnetic field quantum sensors," <i>Nature Communications, </i>vol. 12, July 2021.<br/><br/>[3]<br/>J. S. Colton and L. R. Wienkes, "Resonant microwave cavity for 8.5–12 GHz optically detected electron spin resonance with simultaneous nuclear magnetic resonance," <i>Review of Scientific Instruments, </i>vol. 80, March 2009.<br/><br/>[4]<br/>A. Gottscholl, M. Kianinia, V. Soltamov, S. Orlinskii, G. Mamin, C. Bradac, C. Kasper, K. Krambrock, A. Sperlich, M. Toth, I. Aharonovich and V. Dyakonov, "Initialization and read-out of intrinsic spin defects in a van der Waals crystal at room temperature," <i>Nature Materials, </i>vol. 19, p. 540–545, February 2020.