1：Experimental Design and Method Selection:

The study utilizes fs-laser micromachining to fabricate a Fabry-Pérot interferometer with integrated optical waveguides and microfluidic channels in fused silica. The sensor's operation is based on wave interference, with the phase difference between reflected light beams being influenced by the magnetic field-dependent refractive index of a ferrofluid.

2：Sample Selection and Data Sources:

A fused silica substrate (Suprasil 1) was used for the fabrication. A water-based ferrofluid (EMG507, Ferrotec Inc.) was injected into the microfluidic channel.

3：List of Experimental Equipment and Materials:

A fiber amplified fs-laser system, a 0.55 numerical aperture aspherical lens, X-Y air-bearing linear stages, a 10% hydrofluoric acid solution, and a PDMS layer for sealing were used.

4：55 numerical aperture aspherical lens, X-Y air-bearing linear stages, a 10% hydrofluoric acid solution, and a PDMS layer for sealing were used. Experimental Procedures and Operational Workflow:

4. Experimental Procedures and Operational Workflow: The optical waveguide and microfluidic channel were written sequentially in the fused silica substrate, followed by etching in an ultrasonic bath. The device was then sealed, and the ferrofluid was injected. Magnetic field measurements were conducted using an optical spectrum analyser.

5：Data Analysis Methods:

The reflected spectrum was analyzed to determine the peak wavelength shift in response to magnetic field variations, from which the sensitivity was calculated.