67-attosecond extreme ultraviolet laser pulse is the world's shortest

Sep 04, 2012
A photo of Dr. Chang, who accomplished his work at the Florida Atto Science &Technology (FAST) lab in UCF’s Physical Sciences building. Credit: University of Central Florida

A University of Central Florida research team has created the world's shortest laser pulse and in the process may have given scientists a new tool to watch quantum mechanics in action – something that has been hidden from view until now.

UCF Professor Zenghu Chang from the Department of Physics and the College of Optics and Photonics, led the effort that generated a 67-attosecond pulse of . The results of his research are published online under Early Posting in the journal .

An attosecond is an incomprehensible quintillionith of a second. In other words it would take 15 million billion pulses of the size Chang's team achieved to equal one second. The accomplishment is even more remarkable because the team did it without the use of specialized equipment including a mile-long or a Superdome-sized synchrotron.

"Dr. Chang's success in making ever-shorter helps open a new door to a previously hidden world, where we can watch electrons move in atoms and molecules, and follow as they take place," said Michael Johnson, the dean of the UCF College of Sciences and a physicist. "It is astounding to imagine that we may now be able to watch in process."

Quantum mechanics is the study of physics at the , specifically looking at energy and matter on this miniscule scale.

There is much excitement about the accomplishment and the promise Chang's work holds for helping scientists understand how the world's smallest building blocks actually work. The technique could lead scientists to understand how energy can be harnessed to transport data, deliver targeted cancer therapies or diagnose disease. The finding marks the first significant breakthrough in the laser pulse field in four years.

In 2001, attosecond pulses were demonstrated for the first time. Since then scientists around the world have been trying to make ever-shorter pulse durations because of the door they could open to understanding the subatomic world. The previous record of an 80- pulse was set in 2008 at the Max Planck Institute in Garching, Germany. This is the first time an American-led team has set the record.

"The quest for generating shorter and shorter pulses of light has been ongoing since the invention of the laser more than five decades ago," said Bahaa Saleh, dean of CREOL, the College of Optics and Photonics. "Dr. Chang's recent advance brings UCF to the forefront of this Olympic race and opens up new frontiers for seeing and recording ultrafast dynamic atomic phenomena."

Chang's team was able to accomplish the work at the Florida Atto Science &Technology (FAST) lab in UCF's Physical Sciences building.

Using the unprecedented power of laser light enables Chang and his peers to conduct their high-level research in much smaller spaces. Chang's group created a technique called Double Optical Grating that allows extreme ultraviolet light to be cut off in a manner that concentrates the maximum amount of energy in the shortest possible pulse of light. With the affinity for acronyms shared by many ultrafast laser physicists, Chang named the technique DOG. In addition to creating the light pulse, he created an even faster camera to measure it, which is the Phase Retrieval by Omega Oscillation Filtering (PROOF).

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User comments : 17

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Glen_Lincoln
1 / 5 (2) Sep 04, 2012
Another way to consider the brevity of such a short pulse of light: That pulse is so quick the beam would travel a very short distance as well, perhaps only a few microns, or less than the width of a very fine hair. Wait, no, that would be nanosecond pulses. Maybe 1,000 x's shorter, say, the distance of a cell membrane.
DocB
not rated yet Sep 04, 2012
Well, no, the beam will travel continuously until absorbed by matter. But the last photon to leave the laser would trail the first by only the thickness of a cell wall membrane...
sirchick
not rated yet Sep 04, 2012
Is there a theoretical limit to how short it can be (not including technological obstacles).
gwrede
not rated yet Sep 04, 2012
The absolutely ultimate limit would be one wavelength. But in reality, the soliton would be the shortest pulse. Depending on who you ask, it would be a few wavelenghts long.
dschlink
not rated yet Sep 04, 2012
Somewhere around 200 atoms in thickness.
Pressure2
not rated yet Sep 04, 2012
The highest frequencies in the ultraviolet range have a wavelength of between 90 and 190 nanometers. It would appear that these attosecond pulses are much shorter than the wavelength of the ultraviolet light. Even shorter than the wavelengths of the much higher frequencies of x-rays.

X-radiation (composed of X-rays) is a form of electromagnetic radiation. X-rays have a wavelength in the range of 0.01 to 10 nanometers,

http://en.wikiped...ki/X-ray
nkalanaga
5 / 5 (1) Sep 05, 2012
The shortest possible pulse is a single photon. In that case, instead of measuring the wavelength, the energy of the photon would determine the type of radiation. In theory, one could make a multiple photon pulse that short by arranging all of the photons in the same plane perpendicular to the direction of travel.
Pressure2
not rated yet Sep 05, 2012
The shortest possible pulse is a single photon. In that case, instead of measuring the wavelength, the energy of the photon would determine the type of radiation. In theory, one could make a multiple photon pulse that short by arranging all of the photons in the same plane perpendicular to the direction of travel.

How short is a single photon? Is it shorter than the wavelength?
nkalanaga
not rated yet Sep 06, 2012
I'm not sure there's any way to measure it, as a photon has no rest mass. Thus, it either moves at the speed of light or doesn't exist, and either way, it would be hard to measure.
Pressure2
1 / 5 (1) Sep 06, 2012
I'm not sure there's any way to measure it, as a photon has no rest mass. Thus, it either moves at the speed of light or doesn't exist, and either way, it would be hard to measure.

True, the photon has no dimension, it is a measurement of electromagnetic energy. It does not even exist as a fundamental particle or even a fundamental unit of electromagnetic energy. It has more in common with a watt, foot pound or horsepower than it does with a particle.
nkalanaga
not rated yet Sep 06, 2012
But it does have measurable momentum, which a watt doesn't. It has more in common with gluons, in that both are "particles" that transfer a fundamental force.
Pressure2
1 / 5 (1) Sep 06, 2012
So can a baseball transfer a fundamental force of nature but that does not make it a fundamental particle in nature.

But there is an even more basic reason a photon cannot be a fundamental particle. The energy and momentum it transfers is based on an arbitrary unit of time, the second by way of its frequency. The second is an man-made unit of time that has no basis in nature.
TheGhostofOtto1923
1 / 5 (4) Sep 06, 2012
I'm not sure there's any way to measure it, as a photon has no rest mass. Thus, it either moves at the speed of light or doesn't exist, and either way, it would be hard to measure.

True, the photon has no dimension, it is a measurement of electromagnetic energy. It does not even exist as a fundamental particle or even a fundamental unit of electromagnetic energy. It has more in common with a watt, foot pound or horsepower than it does with a particle.
Here is a discussion in the forum:
http://www.physic...102.html

-But a pulse one photon in depth would be as short as a pulse could get.
Pressure2
1 / 5 (1) Sep 06, 2012
The discussion referred to a photon as a point particle. But how can it have less depth than its wavelength? The attosecond pulses mentioned in this article appear to have much less depth than the wavelength.

A photon is not a basic unit or particle in nature. It really has no definable size. Telescopes gather photon units of energy and momentum by the square meters.

Planck's Constant is the fundamental energy unit in measuring electomagnetic radiation. The individual wave also carries a fundamental unit of momentum.

A pulse of EMR can be much shorter than it wavelength because EMR is really a wave of fundamental particles smaller (with less depth) than the highest frequency of gamma-rays possible.
baudrunner
2.3 / 5 (3) Sep 08, 2012
An electron is described as a "point particle". As Nkalanaga pointed out, the photon is a force carrier "particle", not a matter particle, and there is no reason to assume that the shortest pulse that can be achieved should be of the dimensions of a single photon, since a single cycle of an electro-magnetic wave can be further broken down into half-waves, quarter-waves, and so on down the asymptote of possibilities, ie. infinitely short.
JaySolis
not rated yet Oct 02, 2012
Basically, the width of the pulse is only limited by Heisenberg uncertainty principle which states that the uncertainty of time (pulse width) times the uncertainty of energy (spectrum) must be greater or equal to Planck's constant over 4 Pi. This means that shorter is the pulse, broader is the frequency spectrum. I don't think there is a limit of time's uncertainty (pulse width), but I could be wrong.
gwrede
not rated yet Oct 09, 2012
According to what most here have written, then we should be able to create an attosecond pulse of, say, long-wave radio waves of 300kHz, which are 1 kilometer long.

I don't think that's possible.