{
  "abstract": "Mid-infrared photothermal microscopy combines the chemical specificity of infrared absorption with the spatial resolution of visible light detection, but practical implementations face a persistent trade-off between forward-scattering (FWS) and backward-scattering (BWS) detection geometries. FWS provides quantitative, shape-independent phase contrast but requires two-sided optical access, which is difficult to achieve in aqueous or thick samples. BWS offers convenient single-sided access, but its signals are strongly distorted by depth-dependent interference for micrometer-scale objects. Here, we present a bidirectional femtosecond mid-infrared pump-probe holographic microscope capable of switching between FWS and BWS geometries within a single instrument and use it to introduce and validate a new imaging modality, internal forward scattering (IFS). IFS exploits the back reflection generated at the top surface of the mid-infrared-transparent sample substrate as an internally generated forward-scattering illumination wave, isolated from the directly backscattered field via temporal coherence gating. Using polystyrene beads on CaF2 substrates in air, water, and a refractive-index-matched glycerol-water mixture, we show that IFS reproduces the signal magnitudes and temporal dynamics of true FWS measurements while retaining the mechanical simplicity and single-sided accessibility of BWS. These results establish IFS as a practical, quantitative alternative to conventional FWS and BWS geometries for photothermal and, more broadly, quantitative phase imaging, with direct relevance to single-sided imaging of biological or solvent-contained specimens.",
  "abstract_shown": true,
  "affiliations": [
    "Department of Physics and Astronomy, Vrije Universiteit Amsterdam, De Boelelaan 1100, Amsterdam 1081 HZ, The Netherlands."
  ],
  "article_type": "research article",
  "arxiv": null,
  "author_total": 3,
  "authors": [
    {
      "affs": [
        0
      ],
      "name": "Emmanuel Kotu Robertson",
      "orcid": "0009-0007-0603-7495"
    },
    {
      "affs": [
        0
      ],
      "name": "Dennis van de Lockand"
    },
    {
      "affs": [
        0
      ],
      "name": "Matz Liebel",
      "orcid": "0000-0001-6220-3143"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/a1mcnz93smq5m.bib",
  "cited_by": 0,
  "doi": "10.1021/acsphotonics.6c01684",
  "fulltext_url": "https://europepmc.org/articles/PMC13742288",
  "id": "a1mcnz93smq5m",
  "issns": [
    "2330-4022"
  ],
  "landing_url": "https://europepmc.org/article/MED/42997715",
  "language": "eng",
  "licence": "CC-BY",
  "licence_label": "CC BY",
  "licence_source": "article",
  "licence_url": "https://creativecommons.org/licenses/by/4.0/",
  "metadata_licence": null,
  "native_subjects": [
    [
      "openalex",
      "3107|Digital Holography and Microscopy"
    ]
  ],
  "openalex": "W7167576139",
  "pdf_url": "https://europepmc.org/articles/PMC13742288?pdf=render",
  "pmcid": "PMC13742288",
  "pmid": "42997715",
  "published": "2026-10-15",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/a1mcnz93smq5m.ris",
  "sources": [
    {
      "first_seen": "2026-11-09T15:20:41Z",
      "native_id": "MED:42997715",
      "source": "europepmc",
      "url": "https://europepmc.org/article/MED/42997715"
    }
  ],
  "subjects": [
    {
      "field": "physics",
      "origin": "openalex:3107|Digital Holography and Microscopy",
      "subfield": "amo"
    }
  ],
  "title": "Bidirectional Phase Sensitivity in Holographic Phototransient Microscopy.",
  "title_text": "Bidirectional Phase Sensitivity in Holographic Phototransient Microscopy.",
  "type": "peer-reviewed",
  "updated_at": "2026-11-09T15:20:41Z",
  "url": "https://research.draconitic.com/paper/a1mcnz93smq5m",
  "venue": "ACS photonics",
  "versions": []
}