Miniaturized Laser Diode Driver and Microwave Source for Transportable Quantum Sensors

The nitrogen-Vacancy (NV) defect center is a promising tool to build magnetic sensors for space applications. This paper presents an ASIC solution of two key blocks in such a sensor: a laser diode driver (LDD) and a microwave (MW) source by a voltage-controlled oscillator (VCO) structure. This application requires that LDD has a wide driving current tuning range and enables a stable LD power insensitive to temperature changes. It also requires that the VCO can generate the MW frequency with three tunable parameters (carrier, modulation and deviation frequency) by a stand-alone design. Designed in a 65-nm technology, the LDD achieves a current tunable from 88.2 mA to 311.3 mA and shows only 0.17 mW deviation at 80 mW working power across a temperature range of $60^{\circ} \mathrm{C}$, and the VCO could reach a carrier frequency range of 2.37 GHz to 3.25 GHz with a modulation frequency of up to 5 MHz and a deviation frequency of up to 6 MHz, according to the post-layout simulation. The two blocks now only occupy an area of $0.79 \mathrm{~mm}^{2}$ and a power consumption of 4.8 mW, which paves the way for a compact, transportable NV magnetic sensor suitable for future space exploration.