Laser-processed diffractive lenses for the frequency range of 4.7 THz
Optics Letters
|March 2, 2019
Summary
Direct laser ablation (DLA) technology successfully fabricated diffractive lenses for terahertz (THz) frequencies. These lenses show high focusing gain and tolerance to misalignment, enabling new THz applications.
Area of Science:
- Optics and Photonics
- Terahertz (THz) Technology
- Laser Material Processing
Background:
- Terahertz (THz) frequencies (above 1 THz) present unique challenges for optical component development.
- Diffractive lenses offer potential for THz beam manipulation but require advanced fabrication methods.
- Direct Laser Ablation (DLA) is an emerging technology for precise material processing.
Purpose of the Study:
- To demonstrate the fabrication of diffractive lenses for the upper THz frequency range using DLA.
- To evaluate the focusing performance and characteristics of fabricated THz lenses.
- To assess the tolerance of these lenses to oblique incidence and misalignment.
Main Methods:
- Fabrication of Soret zone plate and multi-level Fresnel lenses using DLA on metal foil and crystalline silicon.
- Characterization of focusing performance using a 4.745 THz quantum cascade laser and a microbolometric camera.
- Analysis of focusing gain, beam size, and power drop under varying incidence angles.
Main Results:
- Successful fabrication of diffractive lenses for THz frequencies above 1 THz.
- Achieved focusing gain up to 25 dB for binary-phase lenses and 29 dB for eight-level phase lenses.
- Demonstrated excellent tolerance to misalignment, with <10% power drop at 10° incidence.
Conclusions:
- DLA technology is a viable method for producing high-performance diffractive lenses in the THz range.
- The fabricated lenses exhibit significant focusing capabilities and robustness.
- These advancements open new avenues for THz applications in various industries.
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