Optical spectroscopic imaging has long served as a cornerstone of biophotonics and medical photonics, enabling molecularly specific contrast through various mechanisms: mid-infrared fingerprint vibrations, near-infrared overtone and combination bands, spontaneous and stimulated Raman scattering, and electronic absorption. While many of these modalities offer strong absorption cross-sections in theory, their practical implementation is limited by signal strength and background interference in real-world biological contexts. Photothermal detection circumvents these limitations by measuring thermally induced changes such as refractive index variation, expansion, or cantilever deflection. Since its first demonstrations in the 1970s for detection of overtone transition, photothermal spectroscopy has evolved significantly-spanning gas-phase sensing, mirage-effect tomography, single-particle optical imaging, and nanoscale AFM-based infrared spectroscopy. Most recently, vibrational photothermal imaging technologies have catalyzed a dramatic expansion of life science and material applications. This book, Photothermal Spectroscopy and Microscopy: Theory, Instrumentation, and Applications, serves as a comprehensive reference for researchers entering or advancing in this rapidly growing field. It is organized into four major sections-Theory, Instrumentation, Sensitivity Enhancement, and Applications-and includes 33 chapters written by leading experts worldwide.

Dr. Ji-Xin Cheng is the William Fairfield Warren Distinguished Professor and Theodore Moustakas Chair Professor in Photonics and Optoelectronics at Boston University. As a pioneer of chemical imaging, Professor Cheng is an author of 380 peer-reviewed publications with an h-index of 114 (Google Scholar), editor of three books, and holder of >30 patents. In 2014, Cheng co-founded Vibronix Inc devoted to label-free imaging technologies and medical devices. Cheng is also the co-founder and Scientific Advisor of Photothermal Spectroscopy Corp in Santa Barbara. Chemical microscopes based on his innovations (e.g., mIRage and Ultraview) are used worldwide. Cheng is a fellow of NAI, AIMBE, and Optica.

Dr. Craig Prater co-founded Photothermal Spectroscopy Corp. (PSC), where he served as Chief Technology Officer and led the development and commercialization of Optical Photothermal Infrared (O-PTIR) spectroscopy, culminating in the introduction of the mIRage® infrared microscope. Previously, he served as CTO of Anasys Instruments, where he played a leading role in the development and commercialization of AFM-based infrared spectroscopy (AFM-IR), enabling chemical imaging at ~10 nm spatial resolution, and was co-inventor on numerous patents advancing the technology. Earlier, he spent 15 years at Digital Instruments/Veeco (now Bruker), where he helped pioneer advances in atomic force microscopy (AFM) and was named the company's first Technology Fellow. He has served as Principal Investigator on multiple federally funded research projects (NIH, DOE, NSF, NIST) focused on developing and commercializing nanoscale and microscale spectroscopic techniques. Dr. Prater earned his PhD in Physics from the University of California, Santa Barbara, and has authored over 140 scientific publications and patents, with nearly 12,000 citations. He received the 2023 Williams-Wright Award for significant contributions to vibrational spectroscopy in industry.

Dr. Subhasis Adhikari is currently a research associate at the University of Cambridge. He obtained his Ph.D. in Physics from Leipzig University under the supervision of Prof. Frank Cichos. During his postdoctoral stay in Prof. Michel Orrit’s group at Leiden University, he co-developed photothermal circular dichroism microscopy and photothermal magnetic circular dichroism microscopy. His research focuses on photothermal spectroscopy, plasmonics, ultrafast nonlinear optics, single-molecule fluorescence spectroscopy and chirality. He served as the lead organizer and chair of the webinar series “Photothermal Microscopy and Spectroscopy” and as a guest editor for the Journal of Physical Chemistry C special issue titled “Photothermal and Non-Fluorescent Imaging in Microscopy and Spectroscopy.