High-contrast optical bistability using a subwavelength epsilon-near-zero material.

Area of Science:

• Photonics and optical engineering
• Materials science
• Nonlinear optics

Background:

• Optical bistability is crucial for developing optical nonlinear functions like switches and logic gates.
• Free-space bistable devices offer integration advantages but often suffer from low contrast, slow speeds, or large sizes.
• Epsilon-near-zero (ENZ) materials exhibit ultrafast, giant optical nonlinearity at the subwavelength scale, presenting a potential solution.

Purpose of the Study:

• To demonstrate efficient, high-contrast optical bistability in a deep subwavelength scale using ENZ materials.
• To overcome the limitations of existing free-space optical bistability schemes.
• To explore the potential of ENZ materials for compact and ultrafast all-optical signal processing.

Main Methods:

• Numerical demonstration of two schemes for optical bistability.
• Utilizing large-mobility indium-doped cadmium oxide (CdO) as the ENZ material.
• Leveraging the ENZ mode and the Berreman mode for bistability.

Main Results:

• Achieved high-contrast optical bistability within a deep subwavelength size.
• Demonstrated optically tunable ENZ wavelength on a sub-picosecond timescale.
• Showcased switchable bistability between near-zero and high-reflection states.

Conclusions:

• Indium-doped cadmium oxide as an ENZ material enables efficient, compact, and ultrafast optical bistability.
• The proposed schemes offer a promising pathway for advanced all-optical signal processing.
• This work advances the development of subwavelength-scale optical nonlinear devices.