Terahertz microscopy using laser feedback interferometry based on a generalised phase-stepping algorithm

Area of Science:

• Optics and Photonics
• Laser Physics
• Nanotechnology

Background:

• Laser Feedback Interferometry (LFI) is a technique used for sensing applications.
• Extracting magnitude and phase information from interferometric fringes is crucial for LFI.
• Complex models are often required for post-processing laser feedback data.

Purpose of the Study:

• To develop an improved method for coherent sensing using LFI.
• To reduce optical sampling and acquisition times in LFI.
• To eliminate the need for complex laser feedback models in post-processing.

Main Methods:

• Utilized a generalized phase-stepping algorithm for fringe analysis.
• Investigated the method's applicability under varying optical feedback levels and laser parameters.
• Experimentally validated the approach using a terahertz (THz)-frequency laser.

Main Results:

• Achieved fully coherent sensing with as few as 4 sampling points per pixel.
• Demonstrated reliable performance across different feedback levels and sampling conditions.
• Successfully performed 2D nanoscale imaging of out-of-plane fields at THz frequencies.

Conclusions:

• The generalized phase-stepping algorithm offers a significant improvement for coherent sensing with LFI.
• This method enables fast and reliable sensing with reduced data requirements.
• The approach has broad applicability for sensing across THz, visible, and infra-red spectra.