Magnetic-field sensing using a magnetostrictively coupled multimode whispering-gallery-mode microlaser.

Area of Science:

• Photonics
• Materials Science
• Sensor Technology

Background:

• Whispering-gallery-mode (WGM) microlasers offer high sensitivity for sensing applications.
• Magnetostrictive materials like Terfenol-D can convert magnetic fields into mechanical strain.

Purpose of the Study:

• To develop an ultrasensitive active magnetic sensor.
• To leverage heterodyne beat-frequency readout for enhanced detection capabilities.

Main Methods:

• A magnetostrictively actuated WGM microlaser was fabricated by coupling a Terfenol-D rod to an erbium-doped stretchable microcavity.
• Differential frequency shifts between simultaneously lasing modes were measured to generate a radio-frequency beat signal.
• Heterodyne detection was employed to suppress common-mode perturbations.

Main Results:

• The sensor achieved a magnetic field sensitivity of 6.02 MHz/mT.
• A microtesla-level detection limit was demonstrated, representing a two-orders-of-magnitude improvement over direct spectral interrogation.
• The system effectively suppressed thermo-optic common-mode noise.

Conclusions:

• The developed sensor demonstrates a highly sensitive and robust method for magnetic field detection.
• The heterodyne detection scheme offers a versatile platform for ultrasensitive sensing using multimode WGM microlasers.
• This technology has potential applications beyond magnetic sensing.