laser

laser
Name	Laser
Invented	1960
Inventor	Theodore H. Maiman
Application	Spectroscopy; telecommunications; medicine; manufacturing
Related	Maser; Albert Einstein; Arthur Schawlow; Charles Townes

laser A laser is a device that emits coherent electromagnetic radiation through stimulated emission. It has roots in quantum mechanics, optical physics, and engineering and has transformed fields such as Telecommunications, Medicine, Manufacturing, Astronomy, and Military technology. Development involved contributors from institutions like Bell Labs, Columbia University, and Hughes Research Laboratories.

History

The conceptual foundation traces to Albert Einstein's 1917 work on stimulated emission and later theoretical developments by Niels Bohr, Erwin Schrödinger, and Max Planck. Practical steps included the maser by Charles Townes and collaborators at Columbia University and experimental demonstrations culminating in Theodore H. Maiman's 1960 device at Hughes Research Laboratories. Early milestones involved researchers such as Arthur Schawlow, Nikolay Basov, and Aleksandr Prokhorov, and recognition through awards like the Nobel Prize in Physics shared among Townes, Basov, and Prokhorov and later Schawlow and Townes in separate years. Cold War-era funding from agencies such as DARPA and laboratories like Bell Labs and MIT Lincoln Laboratory accelerated military and civilian applications, while conferences at institutions such as Optical Society of America and journals like Physical Review Letters disseminated advances.

Principles of operation

Lasers rely on population inversion in an active medium and optical feedback from a resonator such as a Fabry–Pérot cavity developed in optics work linked to Augustin-Jean Fresnel and Ludwig von Helmholtz. Stimulated emission, predicted by Albert Einstein, produces photons coherent in phase, frequency, and direction; spontaneous emission and absorption compete as described in quantum electrodynamics advanced by Richard Feynman. Gain media span atomic gases, molecular gases, solid-state crystals, doped fibers, and semiconductor junctions whose behavior is modeled using rate equations and Maxwell–Bloch formalisms that trace to theoretical contributions from Lev Landau and Felix Bloch. Mode selection and cavity design employ techniques influenced by John von Neumann-era linear algebra and control theory from researchers at Stanford University and Princeton University.

Types and technologies

Solid-state designs evolved from early ruby lasers to families like neodymium-doped yttrium aluminium garnet (Nd:YAG) used in industrial systems developed at General Electric and Coherent, Inc. Semiconductor lasers, including laser diodes by companies such as IBM and Sony, underpin fiber-optic communications pioneered by teams at Corning Incorporated and research groups at Bell Labs. Gas lasers (helium–neon, CO2) trace techniques refined at MIT and Lawrence Livermore National Laboratory; dye lasers emerged from chemical optics research at Caltech and Columbia University. Fiber lasers and ultrafast titanium-sapphire systems benefited from laser physics programs at University of Rochester and Max Planck Institute for Quantum Optics. Nonlinear optics enabling frequency doubling, parametric oscillation, and chirped pulse amplification relate to work by Gérard Mourou and others, with industrial implementations by companies like Thales Group and TRUMPF.

Applications

Industrial machining and materials processing adopted lasers for cutting and welding in factories of Siemens and Boeing; semiconductor photolithography advanced in fabs operated by Intel and TSMC. Telecommunications used erbium-doped fiber amplifiers and distributed feedback lasers developed in research at Bell Labs and firms such as Nokia and Ericsson. Medical procedures, including ophthalmic surgery and dermatology, drew on technologies commercialized by companies like Johnson & Johnson and Alcon following clinical trials at university hospitals such as Mayo Clinic and Massachusetts General Hospital. Scientific instruments employed lasers in spectroscopy, atomic clocks, and interferometry in projects at LIGO Scientific Collaboration, CERN, and observatories like Keck Observatory. Defense systems integrated high-energy lasers in programs run by US Department of Defense and contractors like Lockheed Martin for missile defense and directed-energy research.

Safety and regulation

Laser safety classifications and standards were developed by bodies including International Electrotechnical Commission, American National Standards Institute, and national agencies such as Food and Drug Administration for medical devices and Occupational Safety and Health Administration for workplace exposure. Hazard analysis uses concepts from occupational health studies at institutions like Johns Hopkins University and Harvard School of Public Health. Export controls and treaties addressing directed-energy weapons have been discussed within forums such as United Nations committees and national regulatory agencies, while industrial compliance often references guidance from Underwriters Laboratories and certification by regional standards organizations.

Research and future developments

Frontiers include high-power coherent combining pursued at laboratories like Lawrence Livermore National Laboratory and ultrafast attosecond pulse generation explored at Imperial College London and École Polytechnique. Quantum information science integrates lasers in trapped-ion and cold-atom platforms advanced at MIT, University of Oxford, and National Institute of Standards and Technology. Photonic integration and silicon photonics research spans Intel, IBM Research, and university consortia such as EPFL and University of California, Berkeley. Space-based applications are being developed by agencies including European Space Agency and NASA for communication and propulsion experiments. Emerging areas involve biomedical optogenetics work at Cold Spring Harbor Laboratory and materials processing innovations in startups spun out of Stanford University and University of Cambridge.

Category:Optical devices