研究目的
To demonstrate a broadband extractor/collimator for terahertz quantum cascade lasers that improves far-field properties over octave-spanning spectral bandwidths without affecting laser performance.
研究成果
The antipodal Vivaldi antenna significantly improves the far-field properties of broadband terahertz quantum cascade lasers, producing a single-lobed beam with a FWHM of (23° × 19°). It also acts as a wave retarder, rotating the polarization by a frequency-dependent angle. The antenna does not affect the laser's emission spectrum or current-voltage characteristics and is suitable for broadband applications.
研究不足
The study mentions a slight decrease in total power due to Fresnel reflection and propagation losses in the polymer and gold in the Vivaldi antenna. Additionally, an estimated gap of 25 μm between the waveguide and the antenna was observed, which could affect the end facet reflectivity.
1：Experimental Design and Method Selection:
The study involved designing an antipodal Vivaldi antenna for broadband double metal waveguide terahertz quantum cascade lasers. The design was optimized through full-wave 3D numerical simulations using CST Microwave Studio.
2：Sample Selection and Data Sources:
The antenna was fabricated on a cyclic olefin copolymer (TOPAS COC) using standard photolithography, metalization, and lift-off techniques.
3：List of Experimental Equipment and Materials:
The antenna was mounted in front of a double metal waveguide THz QCL, and its performance was evaluated using a pyroelectric detector and a linear wire-grid polarizer.
4：Experimental Procedures and Operational Workflow:
The far-field patterns were measured with and without the antenna, and the polarization properties were evaluated.
5：Data Analysis Methods:
The far-field measurements were compared with numerical simulations, and the emission spectrum and current-voltage characteristics were analyzed.
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