Fiber-optic surface plasmon resonant sensor with low-index anti-oxidation coating

Abstract

A multimode fiber-optic surface plasmon resonance (SPR) sensor with a MgF2 film as a modulated layer is studied. The fiber-optic SPR sensor is investigated theoretically, specifically the influence of the dielectric protecting layer, using a four-layer model. The sensor is then fabricated with the optimal parameters suggested by the theoretical simulation. The sensor has a high sensitivity in the analyte refractive index (RI) range of 1.33-1.40. The best sensitivity of 4 464 nm/RIU is achieved in the experiment. The use of dielectric film (MgF2) can not only modulate the resonance wavelength of the sensor, but also protect the silver film from oxidation.

Surface plasmon resonance‐based fiber optic sensor utilizing tin oxide and zinc sulfide: An experimental analysis

“…However, the larger shifts in resonance wavelength are found only for 40 nm Ag‐10 nm SnO 2 layers and 40 nm Ag‐10 nm ZnS layers‐based sensors. Further, during the fabrication of fiber optic sensing probes, Ag layer thickness has been kept 40 nm because the optimal thickness of Ag layer is 40 nm 17,40–42 . It can be clearly seen that for each refractive index, there is a minimum in the SPR curve at a specific wavelength known as resonance wavelength.…”

“…The vacuum coating machine is maintained at a pressure of 10 −5 mbar 39 . It is to be noted here that the initial coating of probes with 40 nm thick Ag layer is done because 40 nm thickness is the optimized thickness of Ag layer 40–42 . Measurement of thicknesses of layers is done by the quartz crystal thickness monitor (accuracy ~0.1 nm), fitted in the thermal coating unit.…”

“…39 It is to be noted here that the initial coating of probes with 40 nm thick Ag layer is done because 40 nm thickness is the optimized thickness of Ag layer. [40][41][42] Measurement of thicknesses of layers is done by the quartz crystal thickness monitor (accuracy $0.1 nm), fitted in the thermal coating unit. By following this method, numerous sensing probes with 40 nm thick Ag layer, 40 nm Ag-10 nm SnO 2 layers, 40 nm Ag-20 nm SnO 2 layers, 40 nm Ag-30 nm SnO 2 layers, 40 nm Ag-10 nm ZnS layers, 40 nm Ag-20 nm ZnS layers, and 40 nm Ag-30 nm ZnS layers are prepared.…”

“…40 nm because the optimal thickness of Ag layer is 40 nm. 17,[40][41][42] It can be clearly seen that for each refractive index, there is a minimum in the SPR curve at a specific wavelength known as resonance wavelength. Also, resonance wavelengths shift towards higher side with increasing refractive indices of the surrounding mediums.…”

Optical Wave Guiding and Spectral Properties of Micro/Nanofibers Used for Quantum Sensing and Quantum Light Generation

“…Optical micro/nanofibers (MNFs) are usually referred to one-dimensional optical waveguide with the diameter close to or smaller than the wavelength of guided light, which confines and guides the beam by the total internal reflection at the silica(SiO 2 )-air interface [1][2][3][4]. Recently, MNFs have been extensively studied for quantum optics and photonic quantum information because of their extraordinary properties which include low transmission loss, high-nonlinearity, large evanescent fields, and small bending radius [5][6][7][8]. The strong radial confinement much longer than the Rayleigh range of a focused Gaussian beam has made it possible to efficiently couple atoms to the fiber mode via the evanescent field [9][10][11][12][13].…”