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Lett."],"published-print":{"date-parts":[[2026,10,1]]},"abstract":"<jats:p>Germanium waveguide photodetectors are a fundamental building block for high-speed silicon photonic transceivers. While the responsivity is normally proportional to the area of the absorbing germanium layer, too large an active region increases the dark current and sacrifices the bandwidth. It is thus essential to improve the responsivity per unit area to achieve an overall optimal performance. Here, we demonstrate a vertical germanium photodetector with Si\/Ge dual corner reflectors that recycle unabsorbed light in both the Si and Ge layers. The active region occupies a compact chip area of only 4.8\u2009\u03bcm\u2009\u00d7\u20093.7\u2009\u03bcm. It achieves a high responsivity of 0.93\u2009A\/W at 1550\u2009nm and a low dark current of 1.7\u2009nA at \u20132\u2009V. This corresponds to a significantly high responsivity per unit area. Owing to the small active region, the measured 3\u2009dB bandwidth reaches 77\u2009GHz, supporting reception of 112 Gbps non-return-to-zero and 224 Gbps 4-level pulse-amplitude signals.<\/jats:p>","DOI":"10.1364\/ol.611498","type":"journal-article","created":{"date-parts":[[2026,9,1]],"date-time":"2026-09-01T18:00:06Z","timestamp":1788285606000},"page":"5345","update-policy":"https:\/\/doi.org\/10.1364\/crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["High-responsivity germanium photodetector enabled by dual corner reflectors"],"prefix":"10.1364","volume":"51","author":[{"given":"Bingyan","family":"Zhang","sequence":"first","affiliation":[{"id":[{"id":"https:\/\/ror.org\/01yqg2h08","id-type":"ROR","asserted-by":"publisher"}]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yuxiang","family":"Yin","sequence":"additional","affiliation":[{"name":"Hong Kong University of Science and Technology (Guangzhou)"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yihang","family":"Li","sequence":"additional","affiliation":[{"id":[{"id":"https:\/\/ror.org\/01yqg2h08","id-type":"ROR","asserted-by":"publisher"}]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yi","family":"Wang","sequence":"additional","affiliation":[{"id":[{"id":"https:\/\/ror.org\/01yqg2h08","id-type":"ROR","asserted-by":"publisher"}]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7867-1918","authenticated-orcid":true,"given":"Yeyu","family":"Tong","sequence":"additional","affiliation":[{"name":"Hong Kong University of Science and Technology (Guangzhou)"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1935-8910","authenticated-orcid":true,"given":"Ke","family":"Xu","sequence":"additional","affiliation":[{"id":[{"id":"https:\/\/ror.org\/01yqg2h08","id-type":"ROR","asserted-by":"publisher"}]}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"285","published-online":{"date-parts":[[2026,9,18]]},"reference":[{"key":"ol-51-19-5345-R1","doi-asserted-by":"publisher","first-page":"457","DOI":"10.1038\/s41586-022-04579-3","type":"journal-article","volume":"605","author":"Shu","year":"2022","journal-title":"Nature"},{"key":"ol-51-19-5345-R2","doi-asserted-by":"publisher","first-page":"534","DOI":"10.1038\/nature16454","type":"journal-article","volume":"528","author":"Sun","year":"2015","journal-title":"Nature"},{"key":"ol-51-19-5345-R3","doi-asserted-by":"publisher","first-page":"A106","DOI":"10.1364\/PRJ.456772","type":"journal-article","volume":"10","author":"Shi","year":"2022","journal-title":"Photonics Res."},{"key":"ol-51-19-5345-R4","doi-asserted-by":"publisher","first-page":"1301","DOI":"10.1038\/s41566-025-01784-0","type":"journal-article","volume":"19","author":"Li","year":"2025","journal-title":"Nat. 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All rights, including for text and data mining (TDM), Artificial Intelligence (AI) training, and similar technologies, are reserved.","name":"copyright","label":"Copyright"}]}}