Method for adjusting response waveform of superconducting nano-wire photodetectors by utilizing buffer networks

Abstract

The invention relates to a method for adjusting response waveform of superconducting nano-wire photodetectors by utilizing buffer networks, which is characterized in that original pulse signals are divided into two parts by utilizing a coaxial-line tee joint; the signals of one part are connected to a buffer network, and the signals of the other part are connected to a detecting instrument; the buffer network consists of a coaxial cable in certain length and a termination adjustable resistor; the intensity and time delay of reflected pulse signals are adjusted by adjusting the length L of the coaxial cable and the magnitude Rt of the adjustable resistor so as to adjust pulse waveform finally detected; and Rt is more than or equal to 0 and less than the impedance of the coaxial cable. The impedance of the coaxial cable is 50 ohms, so the Rt of the termination adjustable resistor is more than or equal to 0 and less than 50 ohms. The resistance of the resistor determines the reflection coefficient of the buffer network, and the utilization of the buffer network is actually to realize superimposed pulse formed by response pulse and time-delay reflected pulse of the response pulse. By adjusting the resistance of the termination adjustable resistor and the length of a coaxial line of the buffer network, the time to fall edges is effectively reduced so as to reduce pulse width and improve counting capacity and counting rate.

Description

technical field [0001] The invention relates to a method for adjusting the response waveform of a superconducting nanowire photodetector by using a buffer network. Background technique [0002] Superconducting Nanowire Optical Detector (SNOD: Superconducting Nanowire Optical Detector) is a novel light detection method, which can be used for single photon detection with extreme sensitivity in the visible light to infrared band. SNOD devices mainly use low-temperature superconducting ultra-thin film materials, such as NbN, Nb, NbTiN, etc. The typical thickness is about 5 nanometers, and the device structure is usually a meandering nanowire structure with a width of about 100 nanometers [US2005051726A1]. [0003] Theoretically, the response time of a superconducting nanowire photodetector is determined by the thermal relaxation time of the material. For example, for a 3.5nm thick NbN film grown on a sapphire substrate, the thermal relaxation time is ~10 ps. [K.S.Ilin et al, ...

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Problems solved by technology

However, increasing the line width or reducing the length of the nanowire to reduce the dynamic inductance will lead to a decrease in the detection efficiency of the device, so it is not advisable.

At present, there are some reports that the structure of parallel nanowires can effectively reduce the dynamic inductance, but this method increases the complexity of the device fabrication process [M.Ejrnaes et al, Appl.Phys.Lett.91, (2007) 262509]

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