Twin-core fiber SPR sensor

Abstract

We propose and demonstrate a novel surface plasmon resonance (SPR)-sensing approach by using the fundamental mode beam based on a twin-core fiber (TCF). Although normally in a fiber SPR sensor, a multimode fiber (MMF) has often been used to improve the coupling efficiency; for improving fiber SPR sensor sensitivity, single-mode beam is optimal. We provide a novel method to employ the single (fundamental)-mode beam to SPR sense based on the TCF. We grind the TCF tip to be a frustum wedge shape, and plate a 50-nm sensing gold film on the end face, and two 500-nm reflected gold films on the side faces of the wedge tip. By using this new configuration, we reduce the mode noise effectively and get a high testing sensitivity (the testing highest sensitivity reaches to 6463 nm/RIU). This SPR probe can be applied in a microfluidic chip and monitors the refractive index (RI) charges of the flow liquid in the microfluidic channel in real-time. The probe successfully monitors the refractive index of liquid ranged from 1.3333 to 1.3706, and the average sensitivity reaches to 5213 nm/RIU in the solution, which is much higher than most multimode SPR systems.

Surface plasmon resonance biosensor based on gold-coated side-polished hexagonal structure photonic crystal fiber

“…Simulation results show that it is impossible to improve the wavelength sensitivity by changing the duty ratio, the lattice pitch of PCF, and the polishing depth. Compared to these design strategies of by the introduction of a small hollow core into MOF [1,11], optimizing air holes arrayed in MOF cladding [4][5][6][7][8][9][10], and sensitization processing at the polished surface [28,29], most noticeably, we proposed a more effective method for improving sensitivity in D-shaped fiber SPR sensor by making PCF or ordinary fiber with lower RI material. When the RI of PCF material is 1.36, the sensor has an extremely high sensitivity with a value of 21700 nm/RIU.…”

“…To our best knowledge, the theoretical value of the wavelength sensitivity (21700 nm/RIU) is highest sensitivity reported in D-shaped fiber SPR senor 25,26]. Compared to these design strategies of by the introduction of a small hollow core into MOF [1,11], optimizing air holes arrayed in MOF cladding [4][5][6][7][8][9][10], and sensitization processing at the polished surface [27], making PCF with lower RI material is a more effective method for improving sensitivity in D-shaped fiber SPR sensor.…”

“…In many of these later fiber SPR sensing configurations, the cladding of the fiber is removed (sensing area) to allow for the deposition of a thin metallic (mostly Au or Ag) layer that supports the excitation of SPR and their interaction with optical waveguide modes of the fiber [4,5]. These configurations include the modified fiber end [6][7][8], tapered fiber [9], Dshaped fiber [4,[10][11][12][13][14][15][16], fiber grating [17], and photonic crystal fiber [18]. According to the control ability of coupling between optical fiber core modes and surface plasmon waves, more and more attention is being paid to the surface plasmon resonance sensor based on Dshaped photonic crystal fiber recent years.…”

Effects of Incident Light Modes and Non-Uniform Sensing Layers on Fiber-Optic Sensors Based on Surface Plasmon Resonance

“…The sensor uses a single-mode beam to excite surface plasmons and obtains a high RI sensitivity of 5213 nm/RIU. It also reduces the mode noise effectively [9]. Nayak et al report on an optical fiber based localized SPR sensor by using graphene oxide encapsulated Au nanoparticles.…”

Distributed fiber surface plasmon resonance sensor based on the incident angle adjusting method

“…Fiber grinding: We grind the ECF to the designed angle and depth by using a fiber grinding machine [19]. We grind the fiber with 8000-grit grinding paper for 2 h, and then, we polish it with 12,000-grit polishing paper to make sure the grinded surface is completely flat.…”