Optical pulses

Optical pulses

Bursts of electromagnetic radiation of finite duration. Optical pulses are used to transmit information or to record the chronology of physical events. The simplest example is the photographic flash. This was probably first developed by early photographers who used flash powder that, when ignited, produced a short burst of intense light. This was followed by the flash lamp, in which a tube filled with an inert gas such as xenon is excited by a brief electrical pulse. A great advance in the creation of short optical pulses came with the invention of the laser. Lasers are now the most common and effective way of generating a variety of short optical pulses, of different durations, energies, and wavelengths. See Laser

Pulses of millisecond (10-3 s) duration are very simply generated by mechanically modulating a constant light source such as a lamp or a continuous-wave laser. This can be done, for example, by placing a rotating disk with holes in it in front of the light source. Shorter laser pulses, of microsecond (10-6 s) or nanosecond (10-9 s) duration, are generated by using a technique known as Q-switching. A modulating device is incorporated inside the laser cavity that allows the buildup of the laser radiation inside the cavity and then switches it out in an instant. The modulating device is usually controlled by external electrical pulses. Semiconductor diode lasers, which are used to transmit information (voice or data) over a fiber-optic cable, are pumped by electricity and can be directly pulsed by applying to them a pulsed electrical signal. See Optical fibers

Ultrashort laser pulses, with durations of the order of picoseconds (1 ps = 10-12 s) or femtoseconds (1 fs = 10-15 s), are generated by using a general principle known as mode locking, whereby several frequency modes of the laser structure are made to resonate simultaneously and with a well-orchestrated relationship so as to form a short-duration pulse at the laser output.

Pulses as short as 11 fs have been produced directly by a passively mode-locked titanium:sapphire laser. The titanium:sapphire laser has also allowed the extension of ultrashort optical pulses to other wavelength ranges, such as the near-infrared (2–10 μm). Dye lasers, based on organic dyes in solution, have achieved durations as short as 27 fs. Ultrashort diode laser pulses have been obtained by active and passive mode locking and produce pulses as short as a few hundred femtoseconds. They are more commonly operated so as to give rise to pulses in the picosecond range, appropriate for optical communication systems.

The generation of ultrashort laser pulses has been motivated by the quest for ever better resolution in the study of the temporal evolution and dynamics of physical systems, events, and processes. Such laser pulses are capable of creating snapshots in time of many events that occur on the atomic or molecular scale, a technique known as time-resolved spectroscopy. This stroboscopic aspect of ultrashort laser pulses is their most important scientific application and is used in physics, engineering, chemistry, and biology. For example, ultrashort pulses can excite and take snapshots of molecular vibrations and deformations. They can track the passage of charge carriers through a microscopic semiconductor device. This ability to understand the dynamics of the more elemental building blocks of nature can in turn make it possible to build ever faster devices for use in information processing and information transmission, in addition to providing a better understanding of the physical world. See Laser spectroscopy

McGraw-Hill Concise Encyclopedia of Physics. © 2002 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
Existing computers store, process and transmit information by breaking it down into long streams of bits, which are typically electrical or optical pulses representing a zero or one.
Siemion also said that VERITAS could help astronomers detect fast optical pulses, which could possibly originate from alien tech. 
The VERITAS instrument has previously been used to scan for such short optical pulses from KIC 8462852, a star went through mysterious and periodic phases of dimming.
Independently of the input laser energy, duration, wavelength and power, FastLas compresses optical pulses by a factor up to 26, and generates pulses as short as a single-cycle.
Additionally, Dr Gerard Mourou and Dr Donna Strickland were awarded the Nobel Prize for his method to generate high-intensity ultrashort optical pulses. Their invention of so-called chirped pulse amplification is essential to generate the ultrashort laser pulses of the ZEISS VisuMax femtosecond laser system.
The two scientistsDonna Strickland, who earned her doctorate from UR in 1989, and Gerard Mourou, a former optics professor and scientist at the laser labare being honored "for their method of generating high-intensity, ultra-short optical pulses," according to the Nobel Committee on Physics.
Meanwhile, Gerard Mourou from Ecole Polytechnique, France, and the University of Michigan, Ann Arbor, USA together with Donna Strickland from the University of Waterloo, Canada were appreciated for their method of generating high-intensity, ultra-short optical pulses.
Meanwhile, Gerard Mourou from EaAecole Polytechnique, France, and the University of Michigan, Ann Arbor, USA together with Donna Strickland from the University of Waterloo, Canada were appreciated for their method of generating high-intensity, ultra-short optical pulses.
BRUSSELS, Oct 2 (KUNA) -- The Royal Swedish Academy of Sciences in Stockholm decided Tuesday to award the Nobel Prize in Physics 2018 to three scientists "for groundbreaking inventions in the field of laser physics." One half of the prize goes to Arthur Ashkin of the US "for the optical tweezers and their application to biological systems" and the other half jointly to Gerard Mourou of France and and Donna Strickland of Canada "for their method of generating high-intensity, ultra-short optical pulses", said the Academy in a press release.
Transmission of Stationary Nonlinear Optical Pulses in the Dispersive Dielectric Fibers.
Mourou, "Compression of amplified chirped optical pulses," Optics Communications, vol.