400-million-pixel superconducting delay-line camera with 30-ps readout circuit

A research team from Osaka Metropolitan University proposed using a current-biased kinetic inductance detector with submicron 400 megapixels to image hot spots induced by a localized external stimulus over a 15 × 15 mm² area. The team utilized a delay-line technique to trace the propagation of internal signals for a pair of signals arising from each hot spot. Further, they used the timestamps of signal arrivals at the electrodes to determine the position of each hot spot (x, y). Because the signal velocity inside the detector is ultrafast at about 20% the speed of light, a readout circuit with a temporal resolution faster than 250 ps is necessary to resolve the position of a hot spot with a precision of 1.5 μm, which is the size of a meander pitch.

In the researchers’ earlier work, they developed a 1-ns CB-KID readout circuit, but it was not fast enough to resolve each segment as a unit tick step of the hot-spot position. In this work, they developed a new Kalliope-II readout circuit equipped with a front-end main circuit for a continuous readout data acquisition system (AMANEQ) and a high-resolution time-to-digital converter that works at a temporal resolution of 30 ps. This allowed them to resolve images with smaller pixels down to 1.5 × 1.5 μm².

Therefore, the CB-KID sensor can detect various stimuli, such as photons and neutrons. As a superconducting detector, the CB-KID realized a 100,000,000-pixel camera with a 15 × 15 mm² sensitive area. Occasionally, the size of the hot spot in the CB-KID is larger than the meander pitch, enabling one to determine the center-of-gravity position of the hot spots in units of half pitch (0.75 μm). This could enable a superconducting camera with up to 400,000,000 submicron pixels over a 15 × 15 mm² area. This development could open upgreat possibilities when CB-KID is applied to photonic measurements. 

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