Coherent field transients below 15  THz from phase-matched difference frequency generation in 4H-SiC.

Area of Science:

• Nonlinear optics
• Terahertz (THz) science and technology
• Materials science

Background:

• 4H-Silicon Carbide (4H-SiC) possesses a non-centrosymmetric lattice, strong birefringence, and broadband transparency at low optical frequencies.
• These properties make it a promising material for nonlinear optical applications in the THz spectral range.

Purpose of the Study:

• To experimentally demonstrate tunable, phase-matched difference frequency generation (DFG) below 15 THz using 4H-SiC.
• To measure the refractive index of 4H-SiC in the THz range for phase-matching calculations.
• To explore the use of 4H-SiC as a detector crystal for electro-optic sampling and estimate its nonlinear coefficient.

Main Methods:

• Difference Frequency Generation (DFG) experiments were conducted using 4H-SiC as the nonlinear medium.
• Refractive index measurements were performed across the THz spectral range.
• Phase-matching conditions were calculated for various near-infrared pump laser sources.
• 4H-SiC was utilized as a detector crystal for electro-optic sampling.

Main Results:

• Tunable DFG was successfully demonstrated, covering the spectral region below 15 THz.
• Comprehensive refractive index data for 4H-SiC in the THz range was obtained.
• Phase-matching conditions were determined, enabling the selection of appropriate pump lasers.
• The effective second-order nonlinear coefficient of 4H-SiC was estimated.

Conclusions:

• 4H-Silicon Carbide is a viable nonlinear crystal for generating tunable THz radiation.
• The material's properties facilitate efficient phase matching for DFG in the THz region.
• 4H-SiC shows potential for both THz generation and detection, advancing THz spectroscopy and imaging.