Polarization selective ultra-broadband wavelength conversion in silicon nitride waveguides

Area of Science:

• Photonics and Optical Engineering
• Materials Science

Background:

• Broadband four-wave mixing (FWM) is crucial for optical signal processing and frequency conversion.
• Achieving high bandwidth and efficiency in FWM typically requires short waveguides, limiting interaction length.
• Dispersion engineering in waveguides is critical for optimizing FWM performance.

Purpose of the Study:

• To experimentally demonstrate broadband degenerate continuous-wave four-wave mixing in long silicon nitride (Si3N4) waveguides.
• To leverage polarization dependence of waveguide dispersion for operation in the L-band and thulium band.
• To explore switchable, distant phase-matching using higher-order dispersion for versatile light conversion.

Main Methods:

• Utilizing long (0.5 m) silicon nitride waveguides.
• Leveraging polarization dependence (transverse magnetic and transverse electric modes) of waveguide dispersion.
• Employing degenerate continuous-wave four-wave mixing.
• Investigating higher-order dispersion for switchable phase-matching.

Main Results:

• Demonstrated conversion bandwidths >150 nm in the L-band (TM mode) and >120 nm near 2 µm (TE mode).
• Achieved broadband conversion despite using significantly longer waveguides than conventional methods.
• Showcased extreme polarization selectivity for switchable phase-matching.
• Successfully converted telecom band light to O-band (TM) and mid-infrared light up to 2.5 µm (TE).

Conclusions:

• Long silicon nitride waveguides are highly effective for broadband and distant four-wave mixing.
• Polarization control offers a powerful method for tuning dispersion and achieving switchable phase-matching.
• This platform holds significant potential for applications in optical communications and mid-infrared photonics.