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approached the maximum possible level, the introduced loss mechanism (often an electro- or acousto-optical element) is rapidly removed (or that occurs by itself in a passive device), allowing lasing to begin which rapidly obtains the stored energy in the gain medium. This results in a short pulse incorporating that energy, and thus a high peak power.
193:, producing an intense flash. Pulsed pumping is also required for three-level lasers in which the lower energy level rapidly becomes highly populated preventing further lasing until those atoms relax to the ground state. These lasers, such as the excimer laser and the copper vapor laser, can never be operated in CW mode.
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for example, a small volume of material at the surface of a work piece can be evaporated if it is heated in a very short time, whereas supplying the energy gradually would allow for the heat to be absorbed into the bulk of the piece, never attaining a sufficiently high temperature at a particular
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Another method of achieving pulsed laser operation is to pump the laser material with a source that is itself pulsed, either through electronic charging in the case of flash lamps, or another laser which is already pulsed. Pulsed pumping was historically used with dye lasers where the inverted
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In a Q-switched laser, the population inversion is allowed to build up by introducing loss inside the resonator which exceeds the gain of the medium; this can also be described as a reduction of the quality factor or 'Q' of the cavity. Then, after the pump energy stored in the laser medium has
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cannot be narrower than the reciprocal of the pulse width. In the case of extremely short pulses, that implies lasing over a considerable bandwidth, quite contrary to the very narrow bandwidths typical of
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and the like) due to the large peak power, and in ablation applications. Again, because of the extremely short pulse duration, such a laser will produce pulses which achieve an extremely high peak power.
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is equal to the average power divided by the repetition rate, this goal can sometimes be satisfied by lowering the rate of pulses so that more energy can be built up in between pulses. In
124:. These pulses will repeat at the round trip time, that is, the time that it takes light to complete one round trip between the mirrors comprising the resonator. Due to the
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population lifetime of a dye molecule was so short that a high energy, fast pump was needed. The way to overcome this problem was to charge up large
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Such mode-locked lasers are a most versatile tool for researching processes occurring on extremely short time scales (known as femtosecond physics,
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can be prevented. Laser pulses must be spaced out to allow for efficient tissue cooling (thermal relaxation time) between pulses.
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effects. For a given pulse energy, this requires creating pulses of the shortest possible duration utilizing techniques such as
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surgery. When a laser beam comes into contact with soft-tissue, one important factor is to not overheat surrounding tissue, so
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produces optical gain over a wide bandwidth, making a laser possible which can thus generate pulses of light as short as a few
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In other cases the application requires the production of pulses having as large an energy as possible. Since the pulse
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Other applications rely on the peak pulse power (rather than the energy in the pulse), especially in order to obtain
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must have a gain bandwidth sufficiently broad to amplify those frequencies. An example of a suitable material is
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Choi, B.; Welch, A. J. (2001-01-01). "Analysis of thermal relaxation during laser irradiation of tissue".
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189:which are then switched to discharge through
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73:(CW) lasers. The lasing medium in some
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220:Pulsed lasers are also used in
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373:Lasers in Surgery and Medicine
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173:optical parametric oscillators
163:in optical materials (e.g. in
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273:, University Science Books.
269:Siegman, Anthony E. (1986).
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140:-doped, artificially grown
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81:vibronic solid-state lasers
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217:among other applications.
169:parametric down-conversion
165:second-harmonic generation
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20:Pulsed operation of lasers
258:Soft-tissue laser surgery
335:Paschotta, Dr Rüdiger.
283:Svelto, Orazio (1998).
243:Pulsed laser deposition
238:Ultrashort pulse laser
153:femtosecond chemistry
120:down to less than 10
341:www.rp-photonics.com
312:Silfvast, William T.
285:Principles of Lasers
337:"Q-switched lasers"
215:laser range finders
316:Laser Fundamentals
209:are used in laser
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157:ultrafast science
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264:Bibliography
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197:Applications
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161:nonlinearity
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122:femtoseconds
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112:Mode-locking
106:Mode-locking
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85:femtoseconds
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60:The optical
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413:Laser types
222:soft-tissue
146:Ti:sapphire
134:gain medium
130:uncertainty
118:picoseconds
97:Q-switching
91:Q-switching
55:Q-switching
407:Categories
354:2024-05-01
299:References
191:flashlamps
187:capacitors
76:dye lasers
385:0196-8092
62:bandwidth
393:11746113
314:(1996).
232:See also
226:necrosis
142:sapphire
138:titanium
201:Pulsed
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418:Lasers
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271:Lasers
203:Nd:YAG
39:energy
66:pulse
64:of a
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389:PMID
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