Photonics West Keynotes Highlight Advances in Vibrational Circular Dichroism, Quantum Cascade Lasers, and More

The SPIE Photonics West conference was held from January 25–30, 2025 in San Francisco, California. This conference, drawing attendees from all over the world, highlights cutting-edge research in fields like biomedical optics, quantum technologies, and more. Plenary speakers during the event highlighted their research and discuss the latest advancements in their fields of study. During the first half of the conference, this involved presenters from TU Wien (Austria), the Washington University in St. Louis (United States), ETH Zurich (Switzerland), and University of Bari Aldo Moro (Italy).

City of San Francisco Ca. Downtown business district seen through the north tower of the Golden Gate Bridge | Image Credit: © Larry D Crain - stock.adobe.com

The conference started with a keynote presentation on January 25 by Georg Ramer, Daniel-Ralph Hermann, and Bernhard Lendl from TU Wien in Austria (1). The focus of the talk was vibrational circular dichroism (VCD), a mid-infrared spectroscopic technique that, in addition to enabling enantiomer identification, is highly sensitive to protein folding and protein secondary structures.

Until recently, VCD’s growth was limited by low-intensity light sources, which caused long measurement times and low sensitivity. Ramer and his team found that VCD instrumentation based on novel external cavity quantum cascade lasers yielded significantly improved sensitivity and throughput. According to Ramer’s research, when recording VCD spectra of the amide I and II spectral region is enabled, as little as 2 mg mL^-1 of protein can be tracked within 5 seconds. During his presentation, Ramer discussed his team’s findings and what that may mean for the future of VCD spectroscopy.

Later that day, Christine M. O’Brien of the Washington University in St. Louis presented her findings on new technology to detect postpartum hemorrhage (PPH) (2). A condition where a woman has heavy bleeding after giving birth, about 1–5 in 100 women who have a baby get afflicted with PPH (3). Moreover, according to O’Brien, PPH is the globally leading, yet most preventable cause of maternal mortality. Leading factors that cause preventable PPH are delays in diagnosis and treatment.

There is a need for an early and accurate PPH alert system that can be successfully used at the point of care. O’Brien and her team developed a low-cost (<$150), wearable optical device that uses a laser speckle flow index (LSFI) to continuously monitor peripheral perfusion on the wrist, allowing for detection of hemorrhage-induced peripheral vasoconstriction. The team was able to develop a framework for novel low-cost and noninvasive technology that rapidly identifies ongoing blood loss; with this, O’Brien hopes to reduce the “unacceptably high” rates of global maternal morbidity and mortality caused by hemorrhaging (2).

The presentations continued throughout the convention weekend, with Jérôme Faist of ETH Zurich in Switzerland leading the day’s discussions (4). Quantum cascade lasers (QCLs) are semiconductor lasers that offer peak emission in the mid-IR range (4–10 µm), offering excellent light sources for mid-IR applications, like molecular gas analysis and absorption spectroscopy (5). According to Faist, a key feature of these devices is that through quantum engineering, emission can be achieved throughout the mid-infrared from the same active region material. In this presentation, he discussed important novel developments in this technology, and how it can enable further evolution.

Another January 26 opening workshop was a keynote presentation led by Matteo Piscitelli of University of Bari Aldo Moro in Italy (6). Alongside his colleagues, Piscitelli developed a novel graphene-based biosensor designed for the label-free detection of immunoglobulin M (IgM), which is produced by plasma cells as part of the body’s adaptive immune response against foreign pathogens (7). This sensor, which showed a limit of detection (LOD) of 100 zepto-molar (10^-19 M), features a two-terminal device with a millimetric gold sensing surface, bio-functionalized with a densely packed monolayer of anti-immunoglobulin M (anti-IgMs) capturing sites and capacitively coupled to a bare graphene electrode through a water-soaked paper strip. Further, a Raman spectrometer allowed for in situ monitoring of the graphene phonon frequency shifts, triggered by the incubation with few analyte molecules. With this presentation, this new system was explained in detail, along with what its existence could help further.

These presentations are only some of the many held at Photonics West 2025. You can view all of our Photonics West coverage here.

References

(1) External Cavity Quantum Cascade Laser Vibrational Circular Dichroism Spectroscopy for Fast and Sensitive Analysis of Proteins at Low Concentrations. SPIE Photonics West 2024. https://spie.org/photonics-west/presentation/External-cavity-quantum-cascade-laser-vibrational-circular-dichroism-spectroscopy-for/13310-8 (accessed 2025-1-29)

(2) Development and Testing of a Wearable Laser Speckle Device for Detection of Postpartum Hemorrhage. SPIE Photonics West 2024. https://spie.org/photonics-west/presentation/Development-and-testing-of-a-wearable-laser-speckle-device-for/13313-33 (accessed 2025-1-29)

(3) Postpartum Hemorrhage. March of Dimes 2020. https://www.marchofdimes.org/find-support/topics/postpartum/postpartum-hemorrhage (accessed 2025-1-29)

(4) Quantum Cascade Lasers for Sensing. SPIE Photonics West 2024. https://spie.org/photonics-west/presentation/Quantum-Cascade-lasers-for-sensing/13310-29 (accessed 2025-1-29)

(5) Quantum Cascade Lasers (QCL). Hamamatsu 2025. https://www.hamamatsu.com/jp/en/product/lasers/semiconductor-lasers/qcls.html (accessed 2025-1-29)

(6) Raman Spectroscopy of Graphene for Ultrasensitive Protein Detection. SPIE Photonics West 2024. https://spie.org/photonics-west/presentation/Raman-spectroscopy-of-graphene-for-ultrasensitive-protein-detection/13376-4 (accessed 2025-1-29)

(7) Sathe, A.; Cusick, J. K. Biochemistry, Immunoglobulin M. National Library of Medicine 2022. https://www.ncbi.nlm.nih.gov/books/NBK555995/ (accessed 2025-1-29)