Abstract
A 2 × 2 terahertz photoconductive antenna (PCA) array detector with high efficiency synthesis characteristic that improves the signal-to-noise ratio (SNR) of the detected signals has been reported in this paper. By processing the substrate material through a special micromachining process, the current signal generated by the adjacent antenna elements as opposed to that generated by the antenna gap is eliminated. Experiments show that the amplitude of the current signal output by the PCA array detector is consistent with the amplitude of the synchronous superposition of the current signals output by antenna elements, and the synthesis efficiency of the device achieves 93.7%. At the same time, the antenna array detector has low current noise, and its highest SNR is 62 dB under the excitation of different light energy, which is related to the number of antenna array elements.
Highlights
There are mainly two ways to detect terahertz (THz) time-domain waveforms: electro-optic (EO) crystal and photoconductive antenna
The photo-generated carriers generated in the substrate materials between adjacent antennas move directionally under the action of the terahertz electric field, forming a current opposite to the current generated in the antenna gap, the reverse current will reduce the generation efficiency of THz
In order to explain that photo-generated carriers move freely throughout the semiconductor, an unmicromachined antenna array, which is similar to the interdigitated photoconductive antenna (PCA) detectors, was used for the verification experiment, we focused the laser with a power of 800 mW laser on the gap of one antenna element, and the diameter of the focus is 93 μm, the dark state resistance of the antenna was reduced from 1.1 GΩ to several MΩ
Summary
There are mainly two ways to detect terahertz (THz) time-domain waveforms: electro-optic (EO) crystal and photoconductive antenna. The principle of the former is based on the Pockels effect of crystals [1, 2]. Compared with the photoconductive antennas, the EO detection requires more optical elements, higher cost and larger system size. A single THz PCA has been widely used in THz time-domain spectroscopy systems, it still has shortcomings in detecting weak terahertz signals and improving the SNR. In theory, connecting multiple PCAs in parallel to form a PCA array detector can make use of the THz electric field as much as possible to improve the SNR and detection sensitivity of the PCA array detector.
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