Lasers, applications and technologies

“Life holds one great but quite commonplace mystery. Though shared by each of us and known to all, it seldom rates a second thought. That mystery, which most of us take for granted and never think about twice, is time”. (Michael Ende, MOMO, 1973)

„Es gibt ein großes und doch ganz alltägliches Geheimnis. Alle Menschen haben daran teil, jeder kennt es, aber die wenigsten denken je darüber nach. Die meisten Leute nehmen es einfach so hin und wundern sich kein bisschen darüber. Dieses Geheimnis ist die Zeit…“ (Michael Ende, MOMO, 1973)

There are faster and slower phenomena and both of them can be examined by means of laser technologies. The fastest processes outside the atomic core can be investigated using attosecond pulses, i.e. the electrons vibrate to the beat of light waves in billionths of a billionth of a second. These electrons form an orchestra that makes waves that allow us to see the world around us and to observe the universe and the microcosm. At Attoworld [1], the website of the Laboratory for Attosecond Physics (LAP) at Ludwig Maximilians University Munich, you can discover the research, headed by Prof. Ferenc Krausz (Max Planck Institute of Quantum Optics, Division of Attosecond Physics, Garching, Germany), by observing the motion of electrons in inconceivably small dimensions.

“The symbiosis of electrons and light forms the basis of life: the motion of electrons creates light, supplying our globe with life-giving energy, and transforming light into biological energy during photosynthesis, as well as into biological signals endowing us with the capability of vision. Electrons emit light and carry and process information in living creatures as well as in man-made devices, thus modifying molecules and thereby affecting biological function. Consequently, they are key players in the physical, chemical, and life sciences and information, industrial, and medical technologies” [2].

While in the microcosm, the focus is on electronic phenomena relevant to technology and life, its exploration is aiming to get insight into the microscopic origin of diseases and into ways of combating them. A major goal in the macrocosm is the design of cost-effective instrumentation not only for the early diagnosis of diseases, including early cancer detection by developing methods, such as phase contrast imaging [3], [4], [5], [6], but also for cancer therapy with particle beams before the emergence of metastases [7]. Laser-driven ion acceleration is a promising approach building compact particle treatment units for therapeutic applications in medicine. By replacing large installations of conventional particle therapy systems, this technology could in the future make the favorable properties of particle beams available to a greater number of cancer patients [8], [9].

Microscopic modalities with high optical resolution became public knowledge when Eric Betzig, Stefan W. Hell, and William E. Moerner were awarded the Nobel Prize in Chemistry in 2014 [10]. They were honored for having circumvented the physical limit of the traditional optical microscopy’s maximum resolution, which – the microscopist Ernst Abbe stipulated in 1873 – would never exceed 0.2 µm. Thanks to their achievements, the world of optical microscopy is now able to peer into the nanoworld. Using nanoscopic techniques, scientists can visualize the pathways of individual molecules inside living cells.

The review by Kalinina and Rück [11] in this issue describes time-resolved spectroscopy techniques used to measure the lifetime of fluorophores with high-resolution in cells and tissues. Laser pulses in the femtosecond regime are used to achieve a high time resolution which corresponds to the high spatial resolution. The development of two-photon excitation microscopic techniques in overall profit from the spatially confined, non-linear excitation effect and from deeper optical penetration depths brought about by using near-infrared excitation wavelengths [12], [13], [14], [15]. Time-correlated single photon counting methods are available in conjunction with specific point scanning techniques. These techniques allow both fluorescence lifetime imaging microscopy (FLIM) and phosphorescence lifetime imaging microscopy (PLIM) methods to be used to identify the fluorescence or phosphorescence of specific target molecules. Kalinina and Rück [11] describe an interesting family of microscopic techniques for combined use in up-to-date biomedical research, with particular attention to the simultaneous application of FLIM and PLIM techniques, providing correlative imaging of both the fluorescence lifetime of metabolic coenzymes and pO₂-sensitive phosphorescence lifetime.

In addition to FLIM and PLIM technologies, super-resolution imaging, multiphoton imaging, Raman microscopy, optical coherence tomography and other advanced optical imaging techniques, optical detection and monitoring technologies, and their application in biomedicine are topics during the 7th Advanced Optical Methods Workshop (AOMW2016) in Shenzhen, China, which will take place in October 2016. The AOMW2016, which includes the 2nd Sino-German Workshop on Biomedical Photonics on FLIM/PLIM technologies, is also part of the International Conference on Laser Application in Life Sciences (LALS 2016) [16].

These kinds of bilateral workshops, supported by the German Research Foundation (Deutsche Forschungsgemeinschaft, DFG), are becoming increasingly popular in the field of biophotonics and laser medicine, as scientists and users can share and discuss the most recent research results in relatively small groups. By using this workshop structure, the awareness of the potential of intercultural competence is becoming a stronger focus of current communication, thus functioning as a connection between different worlds, as was experienced during the First Sino-German Symposium on “Singlet molecular oxygen and photodynamic effects”, held from 23rd to 28th March 2015 in Fuzhou, China [17].

The congress abstracts of the International Conference on Lasers, Applications and Technologies (LAT2016), held in Minsk, Belarus, from 26th to 30th September 2016, presented in this issue [18], show a growing interest, especially of graduates and students, to use the conference platform in the presence of well-known scientists of this field. The conference chairs, Victor B. Loschenov (A. M. Prokhorov General Physics Institute of Russian Academy of Sciences, Moscow, Russia), Rudolf Steiner (Institut für Lasertechnologien in der Medizin und Meßtechnik an der Universität Ulm, Ulm, Germany) and Boris Dzhagarov (B. I. Stepanov Institute of Physics, National Academy of Sciences of Belarus, Minsk, Belarus), made the effort to organize this important meeting in which investigations in the fields of nanobiophotonics, clinical technologies and systems, phototheranostics and neurophotonics were presented.

Obviously, daily science in an interdisciplinary field represents its own universe that can promote the understanding of nature and cultures from various specific points of view. During the last few decades, the world of photonics, biophotonics and laser medicine has changed considerably, especially in terms of the influence of light technologies for everyday applications. There are still new visions to be realized, many challenges to overcome, unmet needs to be identified and gaps to bridge, especially concerning clinical applications.

The presented reports [11], [18] will hopefully encourage you to take part of the still growing fields of Photonics & Lasers in Medicine.