|
Charles H Townes
Charles Hard Townes (July 28, 1915 – January 27, 2015) was an American physicist. Townes worked on the theory and application of the maser, for which he obtained the fundamental patent, and other work in quantum electronics associated with both maser and laser devices. He shared the 1964 Nobel Prize in Physics with Nikolay Basov and Alexander Prokhorov. Townes was an adviser to the United States Government, meeting every US president from Harry S. Truman (1945) to Bill Clinton (1999). He directed the US government's Science and Technology Advisory Committee for the Apollo lunar landing program. After becoming a professor of the University of California, Berkeley in 1967, he began an astrophysical program that produced several important discoveries, for example, the black hole at the center of the Milky Way galaxy. Townes was religious and believed that science and religion are converging to provide a greater understanding of the nature and purpose of the universe. Earl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Greenville, South Carolina
Greenville (; locally ) is a city in and the seat of Greenville County, South Carolina, United States. With a population of 70,720 at the 2020 census, it is the sixth-largest city in the state. Greenville is located approximately halfway between Atlanta, Georgia, and Charlotte, North Carolina, along Interstate 85. Its metropolitan area also includes Interstates 185 and 385. Greenville is the anchor city of the Upstate, a combined statistical area with a population of 1,487,610 at the 2020 census. Greenville was the fourth fastest-growing city in the United States between 2015 and 2016, according to the U.S. Census Bureau. Greenville is the center of the Upstate region of South Carolina. Numerous large companies are located within the city, such as Michelin, Prisma Health, Bon Secours, and Duke Energy. Greenville County Schools is another large employer and is the largest school district in South Carolina. Having seen rapid development over the past two decades, Greenvil ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Elsa M
Elsa may refer to: ELSA (acronym) *ELSA Technology, a manufacturer of computer hardware *English Language Skills Assessment *English Longitudinal Study of Ageing *Ethical, Legal and Social Aspects research *European Law Students' Association The European Law Students' Association (ELSA) is an international, independent, non-political, non-profit, non-governmental organisation run by and for law students. ELSA-activities comprise a large variety of academic and professional events t ... *European League of Stuttering Associations *Evangelical Lutheran Synod of Australia, a group in the history of the Lutheran Church of Australia *Experimental light-sport aircraft (E-LSA) People * Elsa (given name), a female given name * Pedro Elsa (1901–unknown), Argentine Olympic athlete Characters * Elsa of Brabant, a character in the 1850 Richard Wagner opera ''Lohengrin'' * Elsa (Frozen), Elsa (''Frozen''), fictional character from the Disney animated franchise, ''Frozen'' Places * Elsa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Comstock Prize In Physics
The Comstock Prize in Physics is awarded by the U.S. National Academy of Sciences "for recent innovative discovery or investigation in electricity, magnetism, or radiant energy, broadly interpreted." Honorees must be residents of North America. Named after Cyrus B. Comstock, it has been awarded about every five years since 1913. List of Comstock Prize winners See also * List of physics awards * Prizes named after people A prize is an award to be given to a person or a group of people (such as sporting teams and organizations) to recognize and reward their actions and achievements. References {{National Academy of Sciences, state= collapsed Awards established in 1913[...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Autler–Townes Effect
In spectroscopy, the Autler–Townes effect (also known as AC Stark effect), is a dynamical Stark effect corresponding to the case when an oscillating electric field (e.g., that of a laser) is tuned in resonance (or close) to the transition frequency of a given spectral line, and resulting in a change of the shape of the absorption/ emission spectra of that spectral line. The AC Stark effect was discovered in 1955 by American physicists Stanley Autler and Charles Townes. It is the AC equivalent of the static Stark effect which splits the spectral lines of atoms and molecules in a constant electric field. Compared to its DC counterpart, the AC Stark effect is computationally more complex. While generally referring to atomic spectral shifts due to AC fields at any (single) frequency, the effect is more pronounced when the field frequency is close to that of a natural atomic or molecular dipole transition. In this case, the alternating field has the effect of splitting the two bar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spatial Solitons
In optics, the term soliton is used to refer to any optical field that does not change during propagation because of a delicate balance between nonlinear and linear effects in the medium. There are two main kinds of solitons: * spatial solitons: the nonlinear effect can balance the diffraction. The electromagnetic field can change the refractive index of the medium while propagating, thus creating a structure similar to a graded-index fiber. If the field is also a propagating mode of the guide it has created, then it will remain confined and it will propagate without changing its shape * temporal solitons: if the electromagnetic field is already spatially confined, it is possible to send pulses that will not change their shape because the nonlinear effects will balance the dispersion. Those solitons were discovered first and they are often simply referred as "solitons" in optics. Spatial solitons In order to understand how a spatial soliton can exist, we have to make some consider ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Schawlow-Townes Approximation
Laser linewidth is the spectral linewidth of a laser beam. Two of the most distinctive characteristics of laser emission are spatial coherence and spectral coherence. While spatial coherence is related to the beam divergence of the laser, spectral coherence is evaluated by measuring the linewidth of laser radiation. Theory History: First derivation of the laser linewidth The first human-made coherent light source was a maser. The acronym MASER stands for "Microwave Amplification by Stimulated Emission of Radiation". More precisely, it was the ammonia maser operating at 12.5 mm wavelength that was demonstrated by Gordon, Zeiger, and Townes in 1954. One year later the same authors derived theoretically the linewidth of their device by making the reasonable approximations that their ammonia maser Notably, their derivation was entirely semi-classical, describing the ammonia molecules as quantum emitters and assuming classical electromagnetic fields (but no quantized fields ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stimulated Brillouin Scattering
Brillouin scattering (also known as Brillouin light scattering or BLS), named after Léon Brillouin, refers to the interaction of light with the material waves in a medium (e.g. electrostriction and magnetostriction). It is mediated by the refractive index dependence on the material properties of the medium; as described in optics, the ''index of refraction'' of a transparent material changes under deformation (compression-distension or shear-skewing). The result of the interaction between the light-wave and the carrier-deformation wave is that a fraction of the transmitted light-wave changes its momentum (thus its frequency and energy) in preferential directions, as if by diffraction caused by an oscillating 3-dimensional diffraction grating. If the medium is a solid crystal, a macromolecular chain condensate or a viscous liquid or gas, then the low frequency atomic-chain-deformation waves within the transmitting medium (not the transmitted electro-magnetic wave) in the carrier (re ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Infrared Spatial Interferometer
The Infrared Spatial Interferometer (ISI) is an astronomical interferometer array of three telescopes operating in the mid-infrared. The telescopes are fully mobile and their current site on Mount Wilson allows for placements as far as apart, giving the resolution of a telescope of that diameter. The signals are converted to radio frequencies through heterodyne circuits and then combined electronically using techniques copied from radio astronomy. ISI is run by the University of California, Berkeley Space Sciences Laboratory. The longest () baseline provides a resolution of 0.003 arcsecond at a wavelength of 11 micrometres. On 9 July 2003, ISI recorded the first closure phase aperture synthesis Aperture synthesis or synthesis imaging is a type of interferometry that mixes signals from a collection of telescopes to produce images having the same angular resolution as an instrument the size of the entire collection. At each separation and ... measurements in the mid infrare ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Astrophysical Maser
An astrophysical maser is a naturally occurring source of stimulated spectral line emission, typically in the microwave portion of the electromagnetic spectrum. This emission may arise in molecular clouds, comets, planetary atmospheres, stellar atmospheres, or various other conditions in interstellar space. Background Discrete transition energy Like a laser, the emission from a maser is stimulated (or ''seeded'') and monochromatic, having the frequency corresponding to the energy difference between two quantum-mechanical energy levels of the species in the gain medium which have been pumped into a non-thermal population distribution. However, naturally occurring masers lack the resonant cavity engineered for terrestrial laboratory masers. The emission from an astrophysical maser is due to a single pass through the gain medium and therefore generally lacks the spatial coherence and mode purity expected from a laboratory maser. Nomenclature Due to the differences between en ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Laser
A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The word "laser" is an acronym for "light amplification by stimulated emission of radiation". The first laser was built in 1960 by Theodore H. Maiman at Hughes Research Laboratories, based on theoretical work by Charles Hard Townes and Arthur Leonard Schawlow. A laser differs from other sources of light in that it emits light which is ''coherent''. Spatial coherence allows a laser to be focused to a tight spot, enabling applications such as laser cutting and lithography. Spatial coherence also allows a laser beam to stay narrow over great distances (collimation), enabling applications such as laser pointers and lidar (light detection and ranging). Lasers can also have high temporal coherence, which allows them to emit light with a very narrow spectrum. Alternatively, temporal coherence can be used to produce ultrashort pulses of ligh ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Maser
A maser (, an acronym for microwave amplification by stimulated emission of radiation) is a device that produces coherent electromagnetic waves through amplification by stimulated emission. The first maser was built by Charles H. Townes, James P. Gordon, and Herbert J. Zeiger at Columbia University in 1953. Townes, Nikolay Basov and Alexander Prokhorov were awarded the 1964 Nobel Prize in Physics for theoretical work leading to the maser. Masers are also used as the timekeeping device in atomic clocks, and as extremely low-noise microwave amplifiers in radio telescopes and deep-space spacecraft communication ground stations. Modern masers can be designed to generate electromagnetic waves at not only microwave frequencies but also radio and infrared frequencies. For this reason, Townes suggested replacing ''microwave'' with the word ''molecular'' as the first word in the acronym ''maser''. The laser works by the same principle as the maser but produces higher frequency ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Isaac Abella
Isaac David Abella (June 20, 1934 – October 23, 2016) was a Canadian physicist who was a professor at the University of Chicago."Isaac Abella" , Department of Physics, University of Chicago, 2008 He specialized in physics, quantum optics, and ."Marquis Who's Who in Science and Engineering" , |
