Ultra-high sensitivity surface plasmon U-channel photonic crystal fiber for hemoglobin sensing

In order to increase the wavelength response range of the U-channel sensor, a numerical study has been conducted and then the sensing structure has been optimized. A sensor in photonic crystal fiber (PCF) is proposed in which a layer of titanium dioxide is coated on the surface of the U-channel and then coated with a gold film. These two different metal films are mainly used to control the Surface plasmon resonance (SPR) peak and the corresponding resonance wavelength, thus changing the sensor performance. Just below the metal layer are two special air holes on either side. They form a leakage window in the center. In the following sections, the effects of these variables on the sensor will be studied in detail by COMSOL. The modal transmission characteristics of this fiber optic sensor are analyzed in this paper. By analyzing the obtained loss spectrum, the energy variation in the surface plasmon polariton (SPP) mode and the influence of the core mode on the sensing performance of the fiber optic sensor presented, the general rule of the optimized PCF-SPR sensor is deduced. In addition, we can make subtle adjustments to the sensor to improve its sensitivity. We found with the refractive index (RI) ranging from 1.26 to 1.42, the maximum wavelength sensitivity is 7500 nm/RIU, which corresponds to a full width at half maximum (FWHM) of 11.83 nm,a figure of merit (FOM) of 634.1 RIU−1. In addition, we also have discussed the sensor and different concentrations of hemoglobin aqueous solution to detect its RI. It is evident from the results that the sensor demonstrates excellent sensitivity and a wide detection range, which is highly desirable for practical diagnostic purposes. The potential of this sensor for clinical trials and its application to medical diagnostics is promising. Compared with complex traditional methods, the PCF has obvious advantages such as clear structure, simple manufacture, high sensitivity and strong environmental adaptability. Moreover, it has the advantage of wide wavelength response range and has a clear development prospect in the field of biochemical sensing. It has foreseeable potential practical value.