Simple and compact reflective refractometer based on tilted fiber Bragg grating inscribed in thin-core fiber

Area of Science:

• Optoelectronics
• Fiber Optic Sensors
• Photonics

Background:

• Refractive index (RI) sensing is crucial in various scientific and industrial fields.
• Existing refractometers often face limitations in compactness, sensitivity, or temperature stability.
• Fiber Bragg gratings (FBGs) offer a versatile platform for optical sensing applications.

Purpose of the Study:

• To propose and demonstrate a simple, compact reflective refractometer.
• To achieve high refractive index sensitivity with simultaneous temperature referencing.
• To leverage the unique properties of tilted fiber Bragg gratings (TFBGs) in thin-core fiber.

Main Methods:

• Fabrication of a TFBG within an ultra-high photon-sensitive thin-core fiber.
• Utilizing the recoupling of cladding modes to a single TFBG for sensing.
• Analyzing reflection spectra in two distinct wavelength bands: core mode and cladding modes.

Main Results:

• The power of collected cladding modes exhibited a direct correlation with external refractive index changes.
• The Bragg core mode remained unaffected by external RI, serving as a stable temperature reference.
• High refractive index sensitivity and excellent temperature immunity were experimentally validated.

Conclusions:

• The proposed TFBG-based reflective refractometer is a simple and compact sensing device.
• It offers a dual-functionality for simultaneous RI sensing and temperature referencing.
• The device shows significant promise for applications requiring precise and stable optical measurements.