Sub-GHz optical pulsing using a thermally generated heterostructure with strong optomechanical coupling.

Area of Science:

• Photonics
• Optomechanics
• Thermal Engineering

Background:

• Phonon lasing requires specific conditions like unity cooperativity and sideband-resolved operation.
• Silicon optical cavities are promising for optomechanical applications.
• Achieving phonon lasing in weakly confined cavities is challenging.

Purpose of the Study:

• To demonstrate phonon lasing and optical pulsing in a silicon optical cavity using thermal engineering.
• To overcome the limitations of achieving phonon lasing in edge defect photonic crystal cavities.
• To explore the use of dynamically formed heterostructures for optomechanical applications.

Main Methods:

• Shaping the steady-state heat profile generated by absorption in a silicon optical cavity.
• Creating a dynamic heterostructure by modifying the cavity's refractive index using generated heat.
• Utilizing an edge defect photonic crystal optomechanical cavity to couple the compressed optical mode to a thermo-optical/free-carrier-dispersion limit cycle.

Main Results:

• Achieved phonon lasing and sub-GHz optical pulsing (30 MHz) with a photon-phonon cooperativity of 0.088.
• The thermal heterostructure compressed the optical mode volume, relaxing constraints on cavity parameters.
• Successfully initiated phonon lasing by dynamically forming a heterostructure, overcoming insufficient mode confinement.

Conclusions:

• Thermal engineering is a novel approach to initiate phonon lasing in silicon optical cavities.
• The developed method dynamically forms a heterostructure, enabling optomechanical resonance and phonon lasing.
• Further advancements could lead to fully integrated, sub-GHz optical frequency combs.