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Herein, we investigated the performance of a Si waveguide-integrated superconducting nanowire single-photon detector (SNSPD) with an arrayed waveguide grating (AWG) comprising SiN/SiON. The system detection efficiency of SNSPD with AWG was unchanged whether the AWG is at a room or cryogenic temperature because the insertion loss was unchanged while the passband shifts 1.7-nm lower at cryogenic temperature. On the other hand, the dark count rate of the SNSPD with AWG decreased by approximately 20 dB when the AWG was at cryogenic temperature. The AWG at the cryogenic temperature functioned as a cold optical bandpass filter, which suppressed the dark count rate due to the background room-temperature blackbody radiation through fiber optics. The noise equivalent power (NEP) of the SNSPD with AWG improved from 4.8 × 10-17 W/Hz-1/2 for the room-temperature AWG to 2.2 × 10-18 W/Hz-1/2 for the cryogenic-temperature AWG. Results demonstrated that the integration of photonic circuits with SNSPD at the cryogenic temperature benefited not only scalability but also performance.

A 68-year-old woman with an 11-day history of sudden abdominal pain and severe watery diarrhea was transferred to our hospital due to an exacerbation of renal function despite hydration. After treatment for dehydration and acidemia was provided in our intensive care unit, patient's renal function improved. Contrast-enhanced abdominal computed tomography was finally performed, revealing a hypervascular pancreatic mass with multiple hepatic masses. This imaging finding along with her clinical symptoms indicated watery diarrhea hypokalemia achlorhydria (WDHA) syndrome caused by a pancreatic VIPoma. Somatostatin analog was administered immediately leading to the improvement of her diarrhea and her general condition. As a result, endoscopic ultrasonography-guided fine-needle aspiration could be performed. Consequently, she was diagnosed with a pancreatic neuroendocrine tumor. She then underwent surgical resection of the pancreatic tumor and liver metastasis. As revealed in the immunohistochemical analysis of the excised tumor tissue, VIP was highly expressed, resulting in the final diagnosis of pancreatic VIPoma. Therefore, the immediate use of a somatostatin analog is crucial for improving the patient's general condition and achieving a definitive diagnosis pathologically when a patient is suspected of having a pancreatic VIPoma.