In-fiber Rayleigh peak suppression for Brillouin spectroscopy.

Area of Science:

• Photonics and Spectroscopy
• Biomedical Optics
• Materials Science

Background:

• Brillouin spectroscopy offers significant biomedical potential but faces limitations due to complex, costly, and bulky instrumentation.
• A key challenge is detecting weak Brillouin signals near the intense Rayleigh peak.

Purpose of the Study:

• To develop and evaluate an ultra-narrow notch filter for suppressing Rayleigh light in Brillouin spectroscopy.
• To create a compact, cost-effective, and tunable module for enhanced Brillouin measurements.

Main Methods:

• Design and fabrication of a fiber Bragg grating Fabry-Perot filter in reflection.
• Preparation of devices in the L-band and at 785 nm.
• Characterization of filter performance, including suppression ratio and insertion loss.
• Acquisition of Brillouin spectra from various samples using the developed filter.

Main Results:

• The fabricated filter demonstrated good agreement with theoretical predictions and simulations.
• Achieved a suppression of 31 dB at 785 nm with an intrinsic insertion loss of 2 dB.
• Strain tuning allowed for precise adjustment of the filter's characteristics.
• Successful suppression of Rayleigh light enabled improved Brillouin spectral acquisition.

Conclusions:

• The proposed fiber-based notch filter effectively suppresses Rayleigh scattering, enhancing Brillouin spectroscopy capabilities.
• The device is simple, alignment-free, compact, tunable, and cost-effective, paving the way for broader adoption.
• This technology holds promise for democratizing Brillouin spectroscopy and enabling field-deployable systems for biomedical applications.