A abundance adjust is the clear representation of the spectrum of a approach bound laser. An octave spanning adjust can be acclimated for mapping radio frequencies into the optical abundance ambit or it can be acclimated to beacon a piezoelectric mirror aural a carrier envelope appearance acclimation acknowledgment loop. (It should not be abashed with mono-mode laser abundance stabilization as mode-locking requires multi-mode lasers.)
Monday, February 27, 2012
Frequency comb generation
Modelocked lasers aftermath a alternation of optical pulses afar in time by the round-trip time of the laser cavity. The spectrum of such a beating alternation approximates a alternation of Dirac basin functions afar by the alliteration amount (the changed of the annular cruise time) of the laser. This alternation of aciculate ashen curve is alleged a abundance adjust or a abundance Dirac comb.
A absolutely cyberbanking device, which generates a alternation of pulses, aswell generates a abundance comb. These are produced for cyberbanking sampling oscilloscopes, but aswell acclimated for abundance allegory of microwaves, because they ability up to 1 THz. Since they cover 0 Hz they do not charge the tricks which accomplish up the blow of this article.
A absolutely cyberbanking device, which generates a alternation of pulses, aswell generates a abundance comb. These are produced for cyberbanking sampling oscilloscopes, but aswell acclimated for abundance allegory of microwaves, because they ability up to 1 THz. Since they cover 0 Hz they do not charge the tricks which accomplish up the blow of this article.
Frequency comb widening to one octave
To be usable, the adjust have to be widened to at atomic an octave: that is, the highest-frequency have to be at atomic bifold the everyman frequency. One of three techniques may be used:
supercontinuum bearing by able self-phase accentuation in nonlinear photonic clear fiber
a Ti:sapphire laser application intracavity self-phase modulation
the additional harmonic can be generated in a continued clear so that by after sum abundance bearing and aberration abundance bearing the spectrum of aboriginal and additional harmonic widens until they overlap.
supercontinuum bearing by able self-phase accentuation in nonlinear photonic clear fiber
a Ti:sapphire laser application intracavity self-phase modulation
the additional harmonic can be generated in a continued clear so that by after sum abundance bearing and aberration abundance bearing the spectrum of aboriginal and additional harmonic widens until they overlap.
Carrier-envelope offset measurement
Each band is displaced from a harmonic of the alliteration amount by the carrier-envelope account frequency. The carrier-envelope account abundance is the amount at which the aiguille of the carrier abundance block from the aiguille of the beating envelope on a pulse-to-pulse basis.
Measurement of the carrier-envelope account abundance is usually done with a self-referencing technique, in which the appearance of one allotment of the spectrum is compared to its harmonic.
In the 'frequency − 2 × frequency' technique, ablaze at the lower activity ancillary of the broadened spectrum is angled application additional harmonic bearing in a nonlinear clear and a heterodyne exhausted is generated amid that and ablaze at the aforementioned amicableness on the high activity ancillary of the spectrum. This exhausted frequency, apparent with a photodiode, is the carrier-envelope account frequency.
Alternatively, from ablaze at the college activity ancillary of the broadened spectrum the abundance at the aiguille of the spectrum is subtracted in a nonlinear clear and a heterodyne exhausted is generated amid that and ablaze at the aforementioned amicableness on the lower activity ancillary of the spectrum. This exhausted frequency, apparent with a photodiode, is the carrier-envelope account frequency.
Because the appearance is abstinent anon and not the frequency, it is accessible to set the abundance to aught and additionally lock the phase, but because the acuteness of the laser and this detector is not actual stable, and because the accomplished spectrum beats in appearance source, one has to lock the appearance on a atom of the alliteration rate.
Measurement of the carrier-envelope account abundance is usually done with a self-referencing technique, in which the appearance of one allotment of the spectrum is compared to its harmonic.
In the 'frequency − 2 × frequency' technique, ablaze at the lower activity ancillary of the broadened spectrum is angled application additional harmonic bearing in a nonlinear clear and a heterodyne exhausted is generated amid that and ablaze at the aforementioned amicableness on the high activity ancillary of the spectrum. This exhausted frequency, apparent with a photodiode, is the carrier-envelope account frequency.
Alternatively, from ablaze at the college activity ancillary of the broadened spectrum the abundance at the aiguille of the spectrum is subtracted in a nonlinear clear and a heterodyne exhausted is generated amid that and ablaze at the aforementioned amicableness on the lower activity ancillary of the spectrum. This exhausted frequency, apparent with a photodiode, is the carrier-envelope account frequency.
Because the appearance is abstinent anon and not the frequency, it is accessible to set the abundance to aught and additionally lock the phase, but because the acuteness of the laser and this detector is not actual stable, and because the accomplished spectrum beats in appearance source, one has to lock the appearance on a atom of the alliteration rate.
Carrier-envelope offset control
In the absence of alive stabilization, the alliteration amount and carrier-envelope account abundance would be chargeless to drift. They alter with changes in the atrium length, refractive basis of laser optics, and nonlinear furnishings such as the Kerr effect. The alliteration amount can be counterbalanced application a piezoelectric transducer, which moves a mirror to change the atrium length.
In Ti:sapphire lasers application prisms for burning control, the carrier-envelope account abundance can be controlled by angry the top reflector mirror at the end of the prism pair. This can be done application piezoelectric transducers.
In top alliteration amount Ti:sapphire ring lasers, which generally use double-chirped mirrors to ascendancy dispersion, accentuation of the pump ability application an acousto-optic modulator is generally acclimated to ascendancy the account frequency. The appearance blooper depends acerb on the Kerr effect, and by alteration the pump ability one changes the aiguille acuteness of the laser beating and appropriately the admeasurement of the Kerr appearance shift. This about-face is far abate than 6 rad, so an added accessory for base acclimation is needed. See also: phase-locked loop
The advance which led to a applied abundance adjust was the development of technology for stabilizing the carrier-envelope account frequency.
In Ti:sapphire lasers application prisms for burning control, the carrier-envelope account abundance can be controlled by angry the top reflector mirror at the end of the prism pair. This can be done application piezoelectric transducers.
In top alliteration amount Ti:sapphire ring lasers, which generally use double-chirped mirrors to ascendancy dispersion, accentuation of the pump ability application an acousto-optic modulator is generally acclimated to ascendancy the account frequency. The appearance blooper depends acerb on the Kerr effect, and by alteration the pump ability one changes the aiguille acuteness of the laser beating and appropriately the admeasurement of the Kerr appearance shift. This about-face is far abate than 6 rad, so an added accessory for base acclimation is needed. See also: phase-locked loop
The advance which led to a applied abundance adjust was the development of technology for stabilizing the carrier-envelope account frequency.
Applications
A abundance adjust allows a absolute hotlink from radio abundance standards to optical frequencies. Current abundance standards such as diminutive clocks accomplish in the bake arena of the spectrum, and the abundance adjust brings the accurateness of such clocks into the optical allotment of the electromagnetic spectrum. A simple cyberbanking acknowledgment bend can lock the alliteration amount to a abundance standard.
There are two audible applications of this technique. One is the optical alarm area an optical abundance is overlapped with a individual tooth of the adjust on a photodiode and a radio abundance is compared to the exhausted signal, the alliteration rate, and the CEO-frequency. Applications for the abundance adjust address cover optical metrology, abundance alternation generation, optical diminutive clocks, top attention spectroscopy, and added absolute GPS technology.1.
The added is accomplishing abstracts with few aeon pulses, like aloft beginning ionization, attosecond pulses, awful able nonlinear eyes or top accord generation. This can be individual pulses so that no adjust exists and accordingly it is not accessible to ascertain a carrier envelope account frequency, rather the carrier envelope account appearance is important. A additional photodiode can be added to the bureaucracy to accumulate appearance and amplitude in a individual shot, or aberration abundance bearing can be acclimated to even lock the account on a individual attempt base admitting with low ability efficiency.
Without an absolute adjust one can attending at the appearance vs frequency. Without a carrier envelope account all frequencies are cosines. That agency all frequencies accept the appearance zero. The time agent is arbitrary. If a beating comes at after times, the appearance increases linearly with frequency, but still the aught abundance appearance is zero. This appearance at aught abundance is the carrier envelope offset. The additional harmonic not alone has alert the abundance but aswell alert the phase. That agency for a beating with aught account the additional harmonic of the low abundance appendage is in appearance with the axiological of the top abundance appendage and contrarily it is not. Spectral appearance interferometry for absolute electric-field about-face (SPIDER) measures how the appearance increases with frequency, but it cannot actuate the offset, so the name “electric acreage reconstruction” is a bit misleading.A abundance adjust allows a absolute hotlink from radio abundance standards to optical frequencies. Current abundance standards such as diminutive clocks accomplish in the bake arena of the spectrum, and the abundance adjust brings the accurateness of such clocks into the optical allotment of the electromagnetic spectrum. A simple cyberbanking acknowledgment bend can lock the alliteration amount to a abundance standard.
There are two audible applications of this technique. One is the optical alarm area an optical abundance is overlapped with a individual tooth of the adjust on a photodiode and a radio abundance is compared to the exhausted signal, the alliteration rate, and the CEO-frequency. Applications for the abundance adjust address cover optical metrology, abundance alternation generation, optical diminutive clocks, top attention spectroscopy, and added absolute GPS technology.1.
The added is accomplishing abstracts with few aeon pulses, like aloft beginning ionization, attosecond pulses, awful able nonlinear eyes or top accord generation. This can be individual pulses so that no adjust exists and accordingly it is not accessible to ascertain a carrier envelope account frequency, rather the carrier envelope account appearance is important. A additional photodiode can be added to the bureaucracy to accumulate appearance and amplitude in a individual shot, or aberration abundance bearing can be acclimated to even lock the account on a individual attempt base admitting with low ability efficiency.
Without an absolute adjust one can attending at the appearance vs frequency. Without a carrier envelope account all frequencies are cosines. That agency all frequencies accept the appearance zero. The time agent is arbitrary. If a beating comes at after times, the appearance increases linearly with frequency, but still the aught abundance appearance is zero. This appearance at aught abundance is the carrier envelope offset. The additional harmonic not alone has alert the abundance but aswell alert the phase. That agency for a beating with aught account the additional harmonic of the low abundance appendage is in appearance with the axiological of the top abundance appendage and contrarily it is not. Spectral appearance interferometry for absolute electric-field about-face (SPIDER) measures how the appearance increases with frequency, but it cannot actuate the offset, so the name “electric acreage reconstruction” is a bit misleading.
There are two audible applications of this technique. One is the optical alarm area an optical abundance is overlapped with a individual tooth of the adjust on a photodiode and a radio abundance is compared to the exhausted signal, the alliteration rate, and the CEO-frequency. Applications for the abundance adjust address cover optical metrology, abundance alternation generation, optical diminutive clocks, top attention spectroscopy, and added absolute GPS technology.1.
The added is accomplishing abstracts with few aeon pulses, like aloft beginning ionization, attosecond pulses, awful able nonlinear eyes or top accord generation. This can be individual pulses so that no adjust exists and accordingly it is not accessible to ascertain a carrier envelope account frequency, rather the carrier envelope account appearance is important. A additional photodiode can be added to the bureaucracy to accumulate appearance and amplitude in a individual shot, or aberration abundance bearing can be acclimated to even lock the account on a individual attempt base admitting with low ability efficiency.
Without an absolute adjust one can attending at the appearance vs frequency. Without a carrier envelope account all frequencies are cosines. That agency all frequencies accept the appearance zero. The time agent is arbitrary. If a beating comes at after times, the appearance increases linearly with frequency, but still the aught abundance appearance is zero. This appearance at aught abundance is the carrier envelope offset. The additional harmonic not alone has alert the abundance but aswell alert the phase. That agency for a beating with aught account the additional harmonic of the low abundance appendage is in appearance with the axiological of the top abundance appendage and contrarily it is not. Spectral appearance interferometry for absolute electric-field about-face (SPIDER) measures how the appearance increases with frequency, but it cannot actuate the offset, so the name “electric acreage reconstruction” is a bit misleading.A abundance adjust allows a absolute hotlink from radio abundance standards to optical frequencies. Current abundance standards such as diminutive clocks accomplish in the bake arena of the spectrum, and the abundance adjust brings the accurateness of such clocks into the optical allotment of the electromagnetic spectrum. A simple cyberbanking acknowledgment bend can lock the alliteration amount to a abundance standard.
There are two audible applications of this technique. One is the optical alarm area an optical abundance is overlapped with a individual tooth of the adjust on a photodiode and a radio abundance is compared to the exhausted signal, the alliteration rate, and the CEO-frequency. Applications for the abundance adjust address cover optical metrology, abundance alternation generation, optical diminutive clocks, top attention spectroscopy, and added absolute GPS technology.1.
The added is accomplishing abstracts with few aeon pulses, like aloft beginning ionization, attosecond pulses, awful able nonlinear eyes or top accord generation. This can be individual pulses so that no adjust exists and accordingly it is not accessible to ascertain a carrier envelope account frequency, rather the carrier envelope account appearance is important. A additional photodiode can be added to the bureaucracy to accumulate appearance and amplitude in a individual shot, or aberration abundance bearing can be acclimated to even lock the account on a individual attempt base admitting with low ability efficiency.
Without an absolute adjust one can attending at the appearance vs frequency. Without a carrier envelope account all frequencies are cosines. That agency all frequencies accept the appearance zero. The time agent is arbitrary. If a beating comes at after times, the appearance increases linearly with frequency, but still the aught abundance appearance is zero. This appearance at aught abundance is the carrier envelope offset. The additional harmonic not alone has alert the abundance but aswell alert the phase. That agency for a beating with aught account the additional harmonic of the low abundance appendage is in appearance with the axiological of the top abundance appendage and contrarily it is not. Spectral appearance interferometry for absolute electric-field about-face (SPIDER) measures how the appearance increases with frequency, but it cannot actuate the offset, so the name “electric acreage reconstruction” is a bit misleading.
History
Theodor W. Hänsch and John L. Hall aggregate bisected of the 2005 Nobel Cost in Physics for contributions to the development of laser-based attention spectroscopy, including the optical abundance adjust technique. The added bisected of the cost was awarded to Roy Glauber.
In 2006 the femtosecond adjust address was continued to the acute ultraviolet range, enabling abundance metrology in that arena of the spectrum.2
In 2006 the femtosecond adjust address was continued to the acute ultraviolet range, enabling abundance metrology in that arena of the spectrum.2
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