Femtosecond laser processing for a high sensitivity fiber MZI microcavity

Area of Science:

• Optoelectronics and Photonics
• Fiber Optic Sensing Technology
• Nanofabrication and Micromachining

Background:

• Development of compact and highly sensitive optical sensors is crucial for various applications.
• Fiber inline Mach-Zehnder interferometers (MZI) offer a promising platform for sensing.
• Femtosecond laser micromachining enables precise fabrication of microstructures in optical fibers.

Purpose of the Study:

• To demonstrate an ultra-compact fiber inline Mach-Zehnder interferometer sensor.
• To investigate the refractive index and temperature sensing characteristics of the fabricated sensor.
• To evaluate the sensor's robustness and potential for practical applications.

Main Methods:

• Fabrication of an inline Mach-Zehnder interferometer using femtosecond laser micromachining.
• Selective removal of upper cladding and part of the core in a standard single-mode fiber.
• Characterization of the sensor's response to changes in refractive index and temperature.
• Coating the microcavity with a low-refractive-index ultraviolet adhesive for enhanced robustness.

Main Results:

• Achieved an ultra-high refractive index sensitivity of 16660 nm/RIU.
• Observed a temperature sensitivity of 7.934 nm/°C after coating the microcavity.
• Demonstrated excellent robustness of the sensor with the ultraviolet adhesive coating.

Conclusions:

• The femtosecond laser-fabricated fiber inline MZI sensor exhibits exceptional refractive index sensitivity.
• The sensor maintains practical temperature sensitivity and shows enhanced robustness with a protective coating.
• This technology offers a promising solution for developing advanced optical sensing devices.