Angled-MMI-based wavelength splitters on silicon nitride waveguide platforms for fluorescence sensing.

Area of Science:

• Photonics
• Optical Engineering
• Materials Science

Background:

• Fluorescence sensing requires precise separation of excitation and emission light.
• Existing wavelength splitters can be bulky or inefficient, limiting applications.
• Silicon nitride photonics offers low loss and high confinement for visible light applications.

Purpose of the Study:

• To design and demonstrate compact wavelength splitters for fluorescence sensing.
• To utilize angled multimode interferometers (AMMIs) on silicon nitride platforms.
• To achieve efficient spectral separation of fluorescence signals in the visible spectrum.

Main Methods:

• Design and fabrication of angled multimode interferometer (AMMI) based diplexers and triplexers.
• Experimental characterization of insertion loss and crosstalk at target wavelengths.
• Integration of termination structures and tapering waveguides for optimized performance.

Main Results:

• Demonstrated diplexer and triplexer with insertion losses of ~1.7 and ~2.7 dB/channel, respectively.
• Achieved crosstalk below -22 dB and -17 dB for the diplexer and triplexer.
• Successfully distinguished signals from two fluorescent dyes with different Stokes shifts.

Conclusions:

• AMMIs on silicon nitride are effective for compact visible light wavelength splitting.
• The demonstrated devices show high performance suitable for fluorescence sensing.
• The triplexer design offers additional functionality for monitoring excitation power and reducing interference.