Microscopy is the technical field of using microscopes to view objects and areas of objects that cannot be seen with the naked eye. There are three well-known branches of microscopy: optical, electron, and scanning probe microscopy, along with the emerging field of X-ray microscopy.
Ti:sapphire lasers (also known as Ti:Al2O3 lasers, titanium-sapphire lasers, or Ti:sapphs) are tunable lasers which emit red and near-infrared light in the range from 650 to 1100 nanometers. These lasers are mainly used in scientific research because of their tunability and their ability to generate ultrashort pulses thanks to its broad light emission spectrum. Lasers based on Ti:sapphire were first constructed and invented in June 1982 by Peter Moulton at the MIT Lincoln Laboratory.
In optics, an ultrashort pulse, also known as an ultrafast event, is an electromagnetic pulse whose time duration is of the order of a picosecond or less. Such pulses have a broadband optical spectrum, and can be created by mode-locked oscillators. Amplification of ultrashort pulses almost always requires the technique of chirped pulse amplification, in order to avoid damage to the gain medium of the amplifier.
Chirped pulse amplification (CPA) is a technique for amplifying an ultrashort laser pulse up to the petawatt level, with the laser pulse being stretched out temporally and spectrally, then amplified, and then compressed again. The stretching and compression uses devices that ensure that the different color components of the pulse travel different distances.
Laser pumping is the act of energy transfer from an external source into the gain medium of a laser. The energy is absorbed in the medium, producing excited states in its atoms. When for a period of time the number of particles in one excited state exceeds the number of particles in the ground state or a less-excited state, population inversion is achieved. In this condition, the mechanism of stimulated emission can take place and the medium can act as a laser or an optical amplifier. The pump power must be higher than the lasing threshold of the laser.
Ultrafast laser spectroscopy is a category of spectroscopic techniques using ultrashort pulse lasers for the study of dynamics on extremely short time scales. Different methods are used to examine the dynamics of charge carriers, atoms, and molecules. Many different procedures have been developed spanning different time scales and photon energy ranges; some common methods are listed below.
High-harmonic generation (HHG) is a non-linear process during which a target is illuminated by an intense laser pulse. Under such conditions, the sample will emit the high harmonics of the generation beam. Due to the coherent nature of the process, high-harmonics generation is a prerequisite of attosecond physics.
An ultrashort pulse laser is a laser that emits ultrashort pulses of light, generally of the order of femtoseconds to one picosecond. They are also known as ultrafast lasers owing to the speed at which pulses "turn on" and "off"—not to be confused with the speed at which light propagates, which is determined by the properties of the medium, particularly its index of refraction, and can vary as a function of field intensity and wavelength.
The European X-Ray Free-Electron Laser Facility is an X-ray research laser facility commissioned during 2017. The first laser pulses were produced in May 2017 and the facility started user operation in September 2017. The international project with twelve participating countries; nine shareholders at the time of commissioning, later joined by three other partners, is located in the German federal states of Hamburg and Schleswig-Holstein. A free-electron laser generates high-intensity electromagnetic radiation by accelerating electrons to relativistic speeds and directing them through special magnetic structures. The European XFEL is constructed such that the electrons produce X-ray light in synchronisation, resulting in high-intensity X-ray pulses with the properties of laser light and at intensities much brighter than those produced by conventional synchrotron light sources.
An X-ray laser can be created by several methods either in hot, dense plasmas or as a free-electron laser in an accelerator. This article describes the x-ray lasers in plasmas, only.
Erich P. Ippen is a principal investigator in the Research Laboratory of Electronics (RLE) at the Massachusetts Institute of Technology (MIT). He holds appointments as the Elihu Thomson Professor of Electrical Engineering Emeritus and Professor of Physics Emeritus. He is one of the leaders of RLE’s Optics and Quantum Electronics Group.
Fritz Peter Schäfer was a German physicist, born in Hersfeld, Hesse-Nassau. He is the co-inventor of the organic dye laser. His book, Dye Lasers, is considered a classic in the field of tunable lasers. In this book the chapter written by Schäfer gives an ample and insightful exposition on organic laser dye molecules in addition to a description on the physics of telescopic, and multiple-prism, tunable narrow-linewidth laser oscillators.
William Thomas Silfvast is an American physicist well known for his contributions to gas discharge lasers, soft x-ray lasers, and as the author of the influential textbook Laser Fundamentals. and also several thriller novels. Silfvast received his PhD in physics from the University of Utah and a postdoctoral fellowship at the University of Oxford. He then spent much of his career at Bell Laboratories in Holmdel, New Jersey, with a Guggenheim Fellowship at Stanford in 1982–83. Later he became a professor and chairman of the Physics Department at the University of Central Florida's Center for Research in Electro-Optics and Lasers (CREOL). Silfvast remains a Professor Emeritus at UCF, and is now retired and living in Oregon. He is a Fellow of the Optical Society of America, the American Physical Society, and the IEEE. In 2010 Silfvast was selected as one of 27 'Laser Luminaries' during the celebration of the 50th Anniversary of the discovery of the laser.
Martin Aeschlimann is a Swiss physicist and professor in the physics department of the University of Kaiserslautern. Since 2008 he is the spokesman of the State Research Center for Optics and Material Sciences (OPTIMAS).
Wolfgang Sandner was a German physicist who was employed in atomic and laser physics. From 2010 to 2012 he was president of the German Physical Society. Until his death, he was director general of the ELI Delivery Consortium International Association (AISBL) located in Brussels.
Gattamraju Ravindra Kumar is an Indian laser physicist and a senior professor of Nuclear and Atomic Physics at Tata Institute of Fundamental Research. Known for his research on Ultrashort pulse and Warm dense matter, Kumar is an elected fellow of the Indian Academy of Sciences and the Indian National Science Academy. The Council of Scientific and Industrial Research, the apex agency of the Government of India for scientific research, awarded him the Shanti Swarup Bhatnagar Prize for Science and Technology, one of the highest Indian science awards, for his contributions to physical sciences in 2003. He is also a recipient of the B. M. Birla Science Prize and Infosys Prize.
High Harmonic Generation (HHG) is a non-perturbative and extremely nonlinear optical process taking place when a highly intense ultrashort laser pulse undergoes an interaction with a nonlinear media. A typical high order harmonic spectra contains frequency combs separated by twice the laser frequency. HHG is an excellent table top source of highly coherent extreme ultraviolet and soft X-ray laser pulses.
Donna Theo Strickland is a Canadian optical physicist and pioneer in the field of pulsed lasers. She was awarded the Nobel Prize in Physics in 2018, together with Gérard Mourou, for the practical implementation of chirped pulse amplification. She is a professor at the University of Waterloo in Ontario, Canada.
David Attwood is an American physicist and professor emeritus at the University of California, Berkeley, where he worked in the field of synchrotron radiation and free-electron lasers, developing X-ray microscopy techniques for research and for the industry. He is the author of a reference book on soft X-rays and extreme ultraviolet radiation.
Richard R. Freeman is an American physicist, academic and researcher. He is an affiliated professor of physics at the University of Washington, a distinguished emeritus professor of mathematical and physical science at Ohio State University, and an emeritus Edward Teller Professor of Applied Science at University of California, Davis.
