A Power-Efficient Coplanar Waveguide Design for Enhanced Optical Readout in h-BN Quantum Sensors

) defects in hexagonal boron nitride (hBN). While hBN enables easy chip integration, current quantum sensing devices suffer from low optical readout and noisy signals due to inefficient waveguide designs that limit microwave absorption, resulting in reduced optically detected magnetic resonance (ODMR) contrast. This study advances hBN-integrated quantum sensors through three generations, culminating in a compact single-port coplanar waveguide (CPW). Unlike conventional two-port waveguides, our design allows on-chip optical and microwave excitation, ensuring improved impedance stability and high radio frequency (RF) magnetic field concentration without altering spin properties. As a result, we achieve a high ODMR contrast of ∼28% at low microwave power (MW) of 400 mW. This miniaturized sensor enhances efficiency three times, reduces the use of RF power to five times, and supports robust performance at lower MW power, making it ideal for scalable quantum sensing applications such as magnetic field detection.