Highly sensitive refractive index sensor based on adiabatically tapered microfiber long period gratings

Area of Science:

• Photonics and optical sensing
• Fiber optic sensors
• Materials science for optical devices

Background:

• Long Period Gratings (LPGs) are widely used in optical sensing.
• Standard LPGs can be limited by fabrication complexity and sensitivity.
• Developing novel fiber structures is crucial for enhancing sensor performance.

Purpose of the Study:

• To demonstrate a novel refractive index sensor.
• To utilize a unique photosensitive microfiber with a double-clad profile.
• To achieve a high refractive index detection limit.

Main Methods:

• Inscribing a long period grating (LPG) in a specially designed photosensitive microfiber.
• Employing a gradual tapering technique to ensure adiabaticity and minimize insertion loss.
• Utilizing boron and germanium co-doped inner cladding for grating inscription.

Main Results:

• Successfully fabricated a refractive index sensor based on the specialized microfiber LPG.
• Observed a distinct wavelength shift behavior for refractive indices compared to conventional LPGs.
• Achieved a refractive index detection limit as low as 1.67 × 10⁻⁵.

Conclusions:

• The developed microfiber LPG sensor offers a new approach for high-sensitivity refractive index measurements.
• The unique fiber design and grating inscription method enable enhanced sensor performance.
• This technology holds potential for various applications requiring precise refractive index sensing.