Four-wave mixing-based photonic crystal fiber microfluid sensor with embedded U-shape microslits.

Area of Science:

• Photonics
• Optical Sensing
• Microfluidics

Background:

• Photonic crystal fibers (PCFs) offer unique light-confining properties for sensing applications.
• Microfluidic integration enables precise control and analysis of small liquid volumes.
• Four-wave mixing (FWM) provides a sensitive mechanism for optical signal generation and detection.

Purpose of the Study:

• To propose and demonstrate a novel FWM-based PCF microfluid sensor.
• To investigate the sensor's sensitivity to the refractive index (RI) and dispersion of liquid samples.
• To evaluate the sensor's performance metrics, including sensitivity, resolution, and figure of merit (FOM).

Main Methods:

• Fabrication of a PCF with embedded U-shape microslits using femtosecond laser ablation.
• Integration of the PCF into a microfluidic system for real-time sample delivery.
• Utilizing four-wave mixing for signal generation and wavelength shift measurement.
• Experimental characterization of sensor response to varying liquid RI and concentration.

Main Results:

• The signal wavelength demonstrated high sensitivity to both RI and material dispersion of liquid samples.
• Achieved a refractive index sensitivity of approximately 881.36 nm/RIU.
• Obtained a sensing resolution of around 1.6 × 10^-4 RIU.
• Reported a figure of merit (FOM) of 313.65 RIU^-1, outperforming fiber SPR sensors.
• Observed distinct wavelength responses for different aqueous concentrations due to dispersion characteristics.

Conclusions:

• The proposed FWM-based PCF microfluid sensor enables sensitive and real-time measurement of liquid RI and dispersion.
• The sensor exhibits excellent performance metrics, making it suitable for detecting low concentrations of aqueous samples.
• Potential for future development into a wavelength-coded sensor array for discriminating various liquid samples based on their dispersion properties.