Fast one-dimensional photonic crystal modulators for the terahertz range

Area of Science:

• Optics and Photonics
• Condensed Matter Physics
• Terahertz (THz) Science and Technology

Background:

• Photonic crystals offer unique light manipulation properties.
• Controlling terahertz (THz) beams is crucial for advanced applications.
• Semiconductor defect layers can interact strongly with electromagnetic fields.

Purpose of the Study:

• To investigate optically controlled one-dimensional photonic crystal structures for THz applications.
• To explore the modulation of THz beams using photoexcited semiconductor defects.
• To optimize resonant structures for enhanced THz light-matter interaction.

Main Methods:

• Theoretical modeling and experimental fabrication of one-dimensional photonic crystals.
• Utilizing a chromium-doped gallium arsenide (GaAs:Cr) layer as a defect.
• Photoexcitation of the defect layer with 800 nm optical femtosecond pulses.
• Measurement of THz beam modulation and dynamical response.

Main Results:

• Appreciable modulation of the THz output beam achieved even at low optical pump fluences.
• Localization of the THz field within the photoexcited defect layer enhances light-carrier interaction.
• Identification and experimental study of optimum resonant structures.
• Dynamical response is governed by THz photon lifetime and free carrier lifetime.

Conclusions:

• Optically controlled photonic crystals provide an effective method for THz beam modulation.
• The GaAs:Cr defect layer enables efficient interaction with THz fields upon photoexcitation.
• The demonstrated structures exhibit fast time responses, shorter than 330 ps.