Optical microscopy and laser sources for life sciences imaging

Optical microscopy is an essential observation method in many life science disciplines. It is the only imaging technique that offers a minimally invasive protocol involving light-matter interactions, minimizing the risk of damage or destruction to the target being imaged, while offering sub-cellular resolution. It is therefore an essential technique in many life science disciplines, for observing dynamic biological phenomena or living structures on ever smaller scales. In some cases, nanoscale methods such as electron microscopy or atomic force microscopy are irreplaceable for the imaging of living organisms; this topic is beyond the scope of this article. In the remainder of this article, the terms microscopy and optical microscopy will be used interchangeably.

Four companies mainly share the market for optical microscopy for life sciences: Olympus, Nikon, Leica and Zeiss. The microscopy systems offered for sale most often include the latest advances in microscopy technology, mainly concerning excitation sources, detection and image acquisition or processing systems, and scanning systems. Solutions tailored to specific needs can also be proposed. This is the case, for example, with certain super-resolved optical microscopy methods.

Against this backdrop, where the need for laser excitation has grown in parallel with technological advances, the importance of laser sources in optical microscopy has taken on a new dimension since the 2000s. This article begins with an overview of optical microscopy methods currently in routine use, particularly in biology laboratories and on life imaging platforms. The aim is then to establish a link between the need for optical microscopy in the life sciences and recent laser innovations. Indeed, the physics concepts involved in these innovations may be based on sometimes sophisticated principles, not always easy to conceptualize experimentally in the context of the need for microscopy applications in the life sciences. The optical processes involved in these microscopy methods are presented theoretically. Finally, the role and importance of certain physical parameters of laser sources in optimizing the processes involved in MMP for the life sciences are detailed. A non-exhaustive list of laser sources that have been specially developed for MMP applications concludes this article, which also offers a sketch of an ideal laser source for life science microscopy.

At the end of the article, readers will find a glossary and a table of symbols used.