Flex-PCB-Based Multilayered LED Quantum Sensor (FleQS) Utilizing NV Centers in Randomly Oriented Microdiamonds With Novel Orientation Determination

We present a quantum magnetometer based on a flexible printed circuit (FPC) board with a streamlined and automated assembly design. By employing a foldable design, the system achieves advanced miniaturization and integration, along with the capability to form a multilayered structure for direct optical path generation. The sensor head, measuring <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text {(}{3}.{4} \times {2}.{9} \times {2}\text {)} ~\text {mm}^{{3}}$ </tex-math></inline-formula>, is combined with sidearms and a FPC connector which can extend the length as required (here 32 mm). The device demonstrates a sensitivity of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$70~\text {nT}/\text {(}\text {Hz}\text {)}^{\text {1/2}}$ </tex-math></inline-formula> and a theoretical shot-noise-limited sensitivity (SNLS) of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${11}.{73}~\text {nT}/\text {(}\text {Hz}\text {)}^{\text {1/2}}$ </tex-math></inline-formula>. This design is fully compatible with automated production processes, facilitating efficient and cost-effective manufacturing. With a power consumption of approximately <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${0}.{1}~\text {W}$ </tex-math></inline-formula>, which is mainly caused by the light-emitting diode (LED), the foldable sensor is well-suited for a wide range of applications, from handheld devices to stationary systems. A novel approach for automated orientation determination facilitates the usage of randomly oriented, 150-<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu $ </tex-math></inline-formula>m sized, low-cost microdiamonds, further streamlining the fabrication process. Therefore, the sensor presented here offers a step further from the laboratory into the concrete application of quantum sensors based on nitrogen-vacancy (NV) centers.