Current sensor based on an integrated micro-ring resonator and superparamagnetic nanoparticles

An ultra-small integrated photonic current sensor based on a silicon micro-ring resonator (MRR) with a cladding layer of Fe₃O₄ superparamagnetic nanoparticles (SPNPs) is demonstrated. In the magnetic field generated by an alternating current, the Fe₃O₄ SPNPs lose energy and change the MRR temperature, which leads to a spectral shift in the MRR transmission. The sensor was demonstrated with good linearity in the frequency range 0-60 kHz and current amplitudes from 0 to 0.5 A. This work provides a basis for integrated micro-current sensors, and promotes the development of photoelectric sensors on silicon substrates.