Bandwidth control in a hybrid fiber acousto-optic filter

Area of Science:

• Photonics and Waveguide Technology
• Acousto-Optics
• Optical Fiber Communications

Background:

• Acousto-optic filters are crucial for wavelength selection in optical systems.
• Controlling the bandwidth of acousto-optic filters is essential for advanced applications.
• Hybrid waveguides offer unique properties for manipulating light and acoustic waves.

Purpose of the Study:

• To develop a novel bandwidth variation technique for acousto-optic filters.
• To design and characterize a hybrid waveguide combining single-mode fiber (SMF) and hollow optical fiber (HOF).
• To investigate the acousto-optic coupling in the hybrid structure for tunable spectral response.

Main Methods:

• Fabrication of a hybrid waveguide by serial concatenation of SMF and HOF.
• Utilizing adiabatic conversion in optical and acoustic modes for mode coupling.
• Experimental measurement of resonant band Full Width at Half Maximum (FWHM).
• Theoretical analysis of acousto-optic coupling among guided modes in HOF.

Main Results:

• Achieved tunable FWHM of resonant bands from 3.8 nm to 190 nm within a single device.
• Demonstrated a novel hybrid waveguide structure for acousto-optic filtering near the 1.5-microm region.
• Observed good agreement between theoretical predictions and experimental results for acousto-optic coupling.

Conclusions:

• The proposed hybrid waveguide offers a versatile platform for acousto-optic filters with tunable bandwidth.
• The technique effectively utilizes dissimilar phase-matching conditions and beat-length dispersion in SMF and HOF.
• This advancement holds potential for applications requiring flexible spectral control in optical communication and sensing.