Full-field high-resolution terahertz imaging based on a high-resistance silicon solid immersion lens

Area of Science:

• Optics and Photonics
• Terahertz (THz) Imaging Technology
• Microscopy

Background:

• Spatial resolution in direct imaging systems is limited by wavelength and numerical aperture.
• Terahertz (THz) imaging faces challenges due to the relatively large wavelength.
• Solid immersion techniques offer a viable method to enhance numerical aperture and improve resolution.

Purpose of the Study:

• To design and fabricate a solid immersion hemisphere lens for high-resolution THz imaging.
• To analyze and compare direct refraction and secondary reflection imaging characteristics.
• To evaluate the imaging quality, including field curvature and spot diagrams.

Main Methods:

• Fabrication of a hemisphere lens using high-resistance silicon for solid immersion.
• Ray-tracing calculations to analyze imaging characteristics.
• Quantitative evaluation of field curvature and spot diagrams.
• Development of a blocking method for magnified imaging of gratings.

Main Results:

• The solid immersion lens enables full-field, high-resolution focal-plane imaging in the THz waveband.
• Secondary reflection imaging demonstrates reduced geometric distortion and superior imaging quality compared to direct refraction.
• A clear, magnified image of a 300 µm period two-dimensional grating was achieved using the proposed blocking method.

Conclusions:

• Solid immersion hemisphere lenses are effective for enhancing THz imaging resolution.
• Secondary reflection imaging offers improved geometric accuracy and image quality.
• The developed technique provides a powerful tool for THz full-field microscopic imaging of microstructures.