研究目的
Investigating the sensitivity and resolution of a fiber Bragg grating (FBG) based refractometer for refractive index (RI) measurement using femtosecond laser direct writing technique.
研究成果
The proposed FBG based refractometer demonstrates a highly linear sensitivity for RI measurement over a wide range, with an ultra-high sensitivity of 2924.3dB/RIU and a resolution of 3.4×10-7. The intensity demodulation method allows for high precision measurements, making the sensor attractive for bio-chemical sensing applications.
研究不足
The study focuses on the sensitivity and resolution of the FBG based refractometer but does not extensively discuss the potential challenges in practical applications, such as environmental stability and the robustness of the sensor in harsh conditions.
1：Experimental Design and Method Selection:
The study employs a point-by-point femtosecond laser direct writing technique to inscribe a highly localized fiber Bragg grating (FBG). The sensitivity and resolution of the FBG for RI measurement are investigated by monitoring the location of the cut-off wavelength and the 'peak-to-dip' intensity change near the cut-off wavelength.
2：Sample Selection and Data Sources:
A standard single-mode fiber (SMF) with coating removed is used. The FBG is immersed in a series of sucrose solutions with different concentrations for RI measurement.
3：List of Experimental Equipment and Materials:
The setup includes a femtosecond laser (520nm, 350fs, 200kHz repetition rate), an oil-immersion microscope objective (63X/
4：46, Zeiss), and an optical spectrum analyzer (OSA, YOKOGAWA, AQ6370C). Experimental Procedures and Operational Workflow:
The FBG is fabricated with specific laser pulse energy and translation speed. The transmission spectra under different surrounding RIs are recorded.
5：Data Analysis Methods:
The relationship between the cut-off wavelength location and the tested surrounding RI is analyzed for sensitivity. The 'peak-to-dip' intensity change near the cut-off wavelength is monitored for high precision RI measurement.
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