Terahertz all-optical modulation in a silicon-polymer hybrid system

Area of Science:

• Photonics
• Materials Science
• Optical Engineering

Background:

• Silicon photonics has achieved gigahertz (GHz)-scale modulators, but terahertz (THz) speeds remain elusive due to silicon's limited ultrafast nonlinearity.
• Existing silicon-based intensity modulators are significantly slower than the THz range.

Purpose of the Study:

• To demonstrate intensity modulation of light with light at THz speeds in a silicon-based device.
• To enhance the effective nonlinearity of silicon waveguides for ultrafast optical applications.
• To pave the way for large-scale integrated ultrafast optical logic in silicon.

Main Methods:

• Fabrication of a silicon-polymer waveguide device utilizing evanescent coupling.
• Exploitation of the all-optical Kerr effect for light-by-light modulation.
• Experimental measurement of time-domain intensity modulation at 10 GHz and spectral analysis for THz capability.

Main Results:

• Demonstrated intensity modulation of light with light at 10 GHz speeds.
• Experimentally confirmed the ultrafast nature of the modulation mechanism via spectral measurements.
• Indicated the potential for intensity modulation exceeding 1 THz.
• Achieved a significant increase in effective nonlinearity by integrating optical polymers with silicon waveguides.
• Operated the device at continuous-wave power levels compatible with telecommunication systems.

Conclusions:

• The developed silicon-polymer waveguide device enables intensity modulation at speeds up to and exceeding 1 THz.
• This approach significantly enhances silicon's nonlinear optical properties, overcoming previous limitations.
• The technology represents a crucial advancement towards integrated ultrafast optical logic circuits, offering speeds two orders of magnitude greater than prior silicon devices.