Sensitivity Enhancement of Ultrahigh-Order Mode Based Magnetic Field Sensor via Vernier Effect and Coarse Wavelength Sampling

A methodology combining the asymmetrical metal-cladding waveguide (aSMCW) excited ultrahigh-order modes and coarse wavelength induced Vernier effect is theoretically proposed to enhance the sensitivity of the magnetic field sensor. In our aSMCW structure, a transparent glass SF11 with a sub-millimeter scale thickness is selected as the guiding layer, whose magnetically modulated refractive index leads to a variation of resonant wavelength. By controlling the sampling interval of tunable laser, the Vernier effect assisted resonant wavelength shift is more distinguishable and the sensitivity is enhanced about 20 times. Our sensitivity enhancement method is low cost since the optical spectrum analyzer (OSA) with a fine resolution is needless.