{
  "abstract": "Maintaining precise beam coalignment is essential in laser interferometry, particularly for interspacecraft missions where angular misalignments introduce tilt-to-length coupling noise and risk complete link failure. This work presents a comprehensive theoretical and experimental framework for the beam angle-locked loop, which maintains coalignment between two interfering beams. Minute angular misalignments are detected via differential wavefront-sensing signals, which are used as the error signal for feedback control. A detailed linear control model incorporating an angle detector, a digital filter, a proportional-integral-double-integral servo, a digital-to-analog converter, and a beam-steering mechanism is developed. Using loop transfer functions, we establish a noise-propagation model that quantifies the contributions of individual components to both out-of-loop and in-loop angle errors. The analytical results are experimentally validated using a transponder-based interferometric link spanning two optical benches, with a hexapod simulating spacecraft attitude jitter. The measured transfer functions and coalignment performance agree well with theoretical predictions, yielding a pointing stability better than 10 urad$/\\sqrt{\\text{Hz}}$ between 0.2 mHz and 1 Hz. Furthermore, a loop-optimization strategy is demonstrated to minimize angle misalignment within a target frequency band by tuning the servo gain, without requiring hardware modifications. This validated framework provides a reliable architecture for designing and optimizing active beam alignment in laser interferometry.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2609.07985",
  "author_total": 5,
  "authors": [
    {
      "name": "Daikang Wei"
    },
    {
      "name": "Christoph Bode"
    },
    {
      "name": "Vitali Müller"
    },
    {
      "name": "Juan José Esteban Delgado"
    },
    {
      "name": "Gerhard Heinzel"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/5ssrn1n3wnv3v.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2609.07985",
  "fulltext_url": null,
  "id": "5ssrn1n3wnv3v",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2609.07985",
  "language": null,
  "licence": "LicenseRef-arXiv-nonexclusive-1.0",
  "licence_label": "arXiv licence",
  "licence_source": "article",
  "licence_url": "http://arxiv.org/licenses/nonexclusive-distrib/1.0/",
  "metadata_licence": "CC0-1.0",
  "native_subjects": [
    [
      "arxiv",
      "physics.optics"
    ],
    [
      "openalex",
      "3107|Adaptive optics and wavefront sensing"
    ]
  ],
  "openalex": "W7212000099",
  "pdf_url": "https://arxiv.org/pdf/2609.07985",
  "pmcid": null,
  "pmid": null,
  "published": "2026-09-07",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/5ssrn1n3wnv3v.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:19:49Z",
      "native_id": "2609.07985",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2609.07985"
    }
  ],
  "subjects": [
    {
      "field": "physics",
      "origin": "arxiv:physics.optics",
      "subfield": "optics-photonics"
    }
  ],
  "title": "Beam angle-locked loop in laser interferometry",
  "title_text": "Beam angle-locked loop in laser interferometry",
  "type": "preprint",
  "updated_at": "2026-10-30T12:19:49Z",
  "url": "https://research.draconitic.com/paper/5ssrn1n3wnv3v",
  "venue": "arXiv",
  "versions": []
}