Chip-scale non-magnetic ITO heating device for SERF atomic magnetometers

Recent years have seen rapid development on the miniaturization of atomic magnetometers, driven by the demand of high-spatial resolution Magnetoencephalography (MEG) and Magnetocardiogram (MCG). Devices of this kind rely heavily on chip-scale temperature control devices for alkali vapor cell, while conventional approaches namely flexible printed circuits (FPC) present drawbacks including integration difficulties and large magnetic noise. In this study, a novel indium tin oxide (ITO) heating chip is demonstrated, which can be integrated directly into the surface of miniaturized vapor cell. The transparent nature of the resistance wire material allows for flexibility in the coil structure design, as it is not constrained by light transmittance requirements. The device is fabricated on borosilicate glass wafer, which ensures the light transmittance and compatibility with integration. The flaky configuration heating chip shows the magnetic noise with residual magnetic flux density of only 1.949 nT/mA, -0.096 nT/mA and 1.643 nT/mA in the x,y, and z directions, respectively. In addition, the temperature stability of the ITO heating chip was assessed, revealing temperature fluctuations confined to below 0.2 °C. Finally, the experiment achieved comparable sensitivities of 20.38 fT/Hz^1/2 and 20.92 fT/Hz^1/2 for the alkali vapor cell heated by the ITO chip and the FPC method, respectively. This result also proves that the ITO heating chip can achieve practical temperature control of the vapor cell. This work offers an alternative heating method in miniaturized atomic magnetometer for high-resolution biomedical imaging.