Large tolerance for incidence angle in Terahertz parametric detection

Abstract In the THz parametric detection method, which detects terahertz (THz) waves by upconverting them to a near-infrared beam in a LiNbO3 crystal, it has been widely assumed that the THz waves and the pump beam must satisfy the non-collinear phase-matching condition, dictated by the law of momen...

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Main Authors: Hyuga Inoue, Sota Mine, Kodo Kawase, Kosuke Murate
Format: Article
Language:English
Published: Nature Portfolio 2025-07-01
Series:Scientific Reports
Online Access:https://doi.org/10.1038/s41598-025-06264-7
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author Hyuga Inoue
Sota Mine
Kodo Kawase
Kosuke Murate
author_facet Hyuga Inoue
Sota Mine
Kodo Kawase
Kosuke Murate
author_sort Hyuga Inoue
collection DOAJ
description Abstract In the THz parametric detection method, which detects terahertz (THz) waves by upconverting them to a near-infrared beam in a LiNbO3 crystal, it has been widely assumed that the THz waves and the pump beam must satisfy the non-collinear phase-matching condition, dictated by the law of momentum conservation, and that the incidence angle of the THz waves to the crystal must be precisely controlled. However, in this study, we discovered that THz waves can be detected even at various incidence angles to the LiNbO3 crystal that do not satisfy the non-collinear phase-matching condition. While the incidence angle tolerance for the near-infrared injection beam during THz wave generation is as narrow as 0.058 degrees, a remarkably large tolerance of approximately 116 degrees was achieved for terahertz detection. This finding also indicates that the Si prism coupler, previously considered essential for satisfying the phase-matching condition, is not necessarily required. The large incidence-angle tolerance significantly simplifies the optical setup and opens up possibilities for a wider range of application measurements.
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spelling doaj-art-36b128aff4b749f098d7425f41332f362025-08-20T03:03:42ZengNature PortfolioScientific Reports2045-23222025-07-011511810.1038/s41598-025-06264-7Large tolerance for incidence angle in Terahertz parametric detectionHyuga Inoue0Sota Mine1Kodo Kawase2Kosuke Murate3Department of Electronics, Graduate school of Engineering, Nagoya UniversityDepartment of Electronics, Graduate school of Engineering, Nagoya UniversityDepartment of Electronics, Graduate school of Engineering, Nagoya UniversityDepartment of Electronics, Graduate school of Engineering, Nagoya UniversityAbstract In the THz parametric detection method, which detects terahertz (THz) waves by upconverting them to a near-infrared beam in a LiNbO3 crystal, it has been widely assumed that the THz waves and the pump beam must satisfy the non-collinear phase-matching condition, dictated by the law of momentum conservation, and that the incidence angle of the THz waves to the crystal must be precisely controlled. However, in this study, we discovered that THz waves can be detected even at various incidence angles to the LiNbO3 crystal that do not satisfy the non-collinear phase-matching condition. While the incidence angle tolerance for the near-infrared injection beam during THz wave generation is as narrow as 0.058 degrees, a remarkably large tolerance of approximately 116 degrees was achieved for terahertz detection. This finding also indicates that the Si prism coupler, previously considered essential for satisfying the phase-matching condition, is not necessarily required. The large incidence-angle tolerance significantly simplifies the optical setup and opens up possibilities for a wider range of application measurements.https://doi.org/10.1038/s41598-025-06264-7
spellingShingle Hyuga Inoue
Sota Mine
Kodo Kawase
Kosuke Murate
Large tolerance for incidence angle in Terahertz parametric detection
Scientific Reports
title Large tolerance for incidence angle in Terahertz parametric detection
title_full Large tolerance for incidence angle in Terahertz parametric detection
title_fullStr Large tolerance for incidence angle in Terahertz parametric detection
title_full_unstemmed Large tolerance for incidence angle in Terahertz parametric detection
title_short Large tolerance for incidence angle in Terahertz parametric detection
title_sort large tolerance for incidence angle in terahertz parametric detection
url https://doi.org/10.1038/s41598-025-06264-7
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AT kodokawase largetoleranceforincidenceangleinterahertzparametricdetection
AT kosukemurate largetoleranceforincidenceangleinterahertzparametricdetection