研究目的
Investigating the noise power spectral density (NPSD) in time domain terahertz (THz) wave detection systems utilizing GaAs-based photoconductive antennas (PCAs) quantitatively.
研究成果
The noise power spectra in a THz wave detection system based on LTG GaAs PCAs were investigated quantitatively. The contributions of the PCA noise and the amplifier noises at the amplifier output depend strongly on the resistance of the PCA, the circuit parameters, and the frequency. A low noise range appears at the intermediate frequencies. The 1/f noise is suggested to be generated mostly in the contact region between the metal and the LTG GaAs.
研究不足
The absolute values of the resistance on the order of 100 MΩ cannot be discussed because of the limited precision of the equipment. The study focuses on the noise in the detection circuit including the PCA, not on the fluctuation of the THz pulses.
1：Experimental Design and Method Selection:
The study involved measuring the NPSD at the amplifier output as a function of frequency using a spectrum analyzer. The PCA was connected to a current amplifier with a coaxial cable.
2：Sample Selection and Data Sources:
PCAs made on low-temperature-grown (LTG) GaAs with two types of metal system: Ti/Au and Pd/Ge/Ti/Au were used.
3：List of Experimental Equipment and Materials:
Current amplifier (FEMTO LCA-400K-10M), coaxial cable, spectrum analyzer (HP E4401B), laser pulses at 800 nm (Spectra Physics, Maitai).
4：Experimental Procedures and Operational Workflow:
The NPSD was measured with or without an illumination of the PCA by laser pulses. The dc resistance and the noise were measured.
5：Data Analysis Methods:
The measured NPSDs were analyzed using a circuit model to separate the contributions of the PCA noise and the amplifier noises.
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