Swept-source optical coherence tomography based on a backward terahertz-wave parametric oscillator achieving depth...

Area of Science:

• Terahertz (THz) Photonics
• Optical Coherence Tomography
• Nonlinear Optics

Background:

• Terahertz (THz) wave generation and applications are rapidly advancing.
• Optical Coherence Tomography (OCT) is a powerful imaging technique.
• Existing THz-OCT systems face limitations in tuning range and resolution.

Purpose of the Study:

• To develop a wide and continuously frequency tunable THz wave source.
• To apply this source to a THz-wave swept-source OCT (THz-SS-OCT) system.
• To enhance the depth resolution of THz-SS-OCT for material analysis.

Main Methods:

• Utilized quasi-collinear phase-matching (QCPM) control in a backward THz-wave parametric oscillator (BW-TPO).
• Integrated the BW-TPO source into a THz-SS-OCT system.
• Employed an annihilating filter method for super-resolution depth enhancement.

Main Results:

• Achieved a continuously tunable THz wave source with a narrow linewidth (<6 GHz).
• Demonstrated THz-SS-OCT system with a tuning range of 0.26-0.80 THz.
• Obtained a record depth resolution of 0.013 mm, surpassing conventional THz-SS-OCT.

Conclusions:

• The developed BW-TPO based THz-SS-OCT system offers superior performance.
• This technology enables precise semiconductor thickness measurement and depth-profiling.
• Represents the first demonstration of BW-TPO applied to THz-SS-OCT.