Editing Microtome (section)

===Laser ===
{{See also|Laser microtome}}
[[File:Laser-microtome-schematic.png|thumb|A conceptual diagram of laser microtome operation]]

The [[laser]] microtome is an instrument for contact-free slicing.<ref name="Lasermicrotome">Holger Lubatschowski 2007: ''Laser Microtomy'', WILEY-VCH Verlag GmbH, Biophotonics, S. 49–51 ([http://www.photonicnet.de/Aktuelles/partner/2007/06/laser_microtomy_optik-photonik_juni_2007.pdf PDF] {{webarchive|url=https://web.archive.org/web/20110719072556/http://www.photonicnet.de/Aktuelles/partner/2007/06/laser_microtomy_optik-photonik_juni_2007.pdf |date=19 July 2011 }}). {{doi|10.1002/opph.201190252}} {{free access}}</ref> Prior preparation of the sample through embedding, freezing or chemical [[fixation (histology)|fixation]] is not required, thereby minimizing the artifacts from preparation methods. Alternately this design of microtome can also be used for very hard materials, such as bones or teeth, as well as some ceramics. Dependent upon the properties of the sample material, the thickness achievable is between 10 and 100&nbsp;μm.

The device operates using a cutting action of an infrared laser. As the laser emits a radiation in the near infrared, in this wavelength regime the laser can interact with biological materials. Through sharp focusing of the probe within the sample, a focal point of very high intensity, up to [[Terawatt|TW]]/cm<sup>2</sup>, can be achieved.  Through the non-linear interaction of the optical penetration in the focal region a material separation in a process known as photo-disruption is introduced. By limiting the laser pulse durations to the femtoseconds range, the energy expended at the target region is precisely controlled, thereby limiting the interaction zone of the cut to under a micrometre. External to this zone the ultra-short beam application time introduces minimal to no thermal damage to the remainder of the sample.

The laser radiation is directed onto a fast scanning mirror-based optical system, which allows three-dimensional positioning of the beam crossover, whilst allowing beam traversal to the desired region of interest. The combination of high power with a high raster rate allows the scanner to cut large areas of sample in a short time. In the laser microtome the laser-microdissection of internal areas in tissues, cellular structures, and other types of small features is also possible.