Broadband monolithic acousto-optic tunable filter

Area of Science:

• Photonics
• Materials Science
• Electrical Engineering

Background:

• Investigates broadband monolithic acousto-optic tunable filters (AOTFs).
• Combines piezoelectric transducer array and acousto-optic interaction medium in a single crystal.
• Focuses on devices fabricated using domain inversion in Lithium Niobate (LiNbO3).

Purpose of the Study:

• To explore the performance of AOTFs with a linearly chirped acoustic superlattice.
• To achieve a wide optical tuning range for AOTFs.
• To characterize spectral bandwidths and conversion efficiencies.

Main Methods:

• Fabrication of a linearly chirped acoustic superlattice via domain inversion in LiNbO3.
• Excitation of X-propagating longitudinal acoustic waves using a crossed-field scheme with an RF E(y) field.
• Coupling of collinearly propagating e- and o-polarized optical modes.

Main Results:

• Achieved an optical tuning range of lambda = 1.3-1.6 µm.
• Measured spectral bandwidths (FWHM) of 1.54 nm at 1.319 µm and 2.3 nm at 1.55 µm.
• Obtained a relative conversion efficiency of 43%/W and a maximum conversion efficiency of 51% at 1.319 µm.

Conclusions:

• Demonstrated the feasibility of broadband monolithic AOTFs with a chirped superlattice structure.
• Highlighted the potential of LiNbO3 for creating tunable filters with significant optical bandwidth.
• Confirmed efficient acousto-optic mode conversion across the investigated wavelength range.