Direct f-3f self-referencing using an integrated silicon-nitride waveguide

Area of Science:

• Photonics and Optical Engineering
• Materials Science

Background:

• Supercontinuum (SC) generation is crucial for various optical applications.
• Carrier-envelope-offset (CEO) locking is essential for frequency comb stabilization.
• Existing methods often require complex setups and multiple nonlinear elements.

Purpose of the Study:

• To achieve simultaneous SC generation and third-harmonic light production.
• To demonstrate a simplified and compact CEO locking technique.
• To enhance the visible component intensity of the SC spectrum.

Main Methods:

• Fabrication of low-loss, deuterated silicon nitride waveguides (SiNWs) with spot-size converters.
• Utilizing a dispersion-controlled SiNW for simultaneous SC and third-harmonic generation.
• Implementing an f-3f self-referencing scheme solely within the SiNW.

Main Results:

• Generation of a 2.6-octave-wide SC spectrum (400-2500 nm) and third-harmonic light.
• Successful measurement of the CEO signal with a high signal-to-noise ratio (34 dB).
• Demonstration of stable CEO locking at telecommunications wavelengths without external nonlinear media.

Conclusions:

• The developed SiNW platform offers a simple, compact, and stable method for CEO locking.
• This approach eliminates the need for highly nonlinear fibers and additional nonlinear crystals.
• The enhanced visible SC component intensity and stable CEO locking pave the way for advanced photonic applications.