Plasma mirrors generate high harmonics

For many researchers working with high-intensity lasers, plasma formation is often bad news. For others, it’s an enabling step for putting their laser systems to good use, in the form of so-called plasma mirrors. Now, collaborators at CEN Saclay (Gif-sur-Yvette, France), École Polytechnique (Palaiseau, France), and the University of Toronto (Toronto, Ont., Canada) have used a chain of plasma mirrors to create extreme-ultraviolet (EUV) pulses that they predict to be on the attosecond timescale, all with a tabletop laser.

In the highest intensity femtosecond-laser systems, a nanosecond-scale prepulse can be enough to ablate the surface of samples before most of the pulse energy arrives. Enter the plasma mirror, a simple but effective solution to increase the contrast between the prepulse and the main pulse. By placing a highly polished mirror blank in the beam at Brewster’s angle, the nanosecond-scale prepulse passes unchanged. The rising edge of the main pulse, however, converts the surface of the mirror into a highly reflective plasma, specularly reflecting only the main pulse. Once the prepulse is cleaned up by two plasma mirrors, a third forms the basis for high-order harmonic generation (HHG).

C. Thaury et al.,Nature Phys. doi:10.1038/nphys595 (2007).

Laser vision fuels energy future

Photonics.com reported:

The proposed European High Power laser Energy Research (HiPER) facility -- a device intended to demonstrate the feasibility of laser-driven fusion as an energy source -- is entering the preparation phase after completion of a two-year study by an international team of scientists.

Their conclusions have allowed the HiPER project to be selected as part of the European roadmap for future large-scale science facilities. The preparatory phase of the HiPER facility is expected to begin in January and to last for three years.

Achieving nuclear fusion using lasers is the goal of the National Ignition Facility, the latest in a series of high-power laser facilities used for research in inertial confinement fusion. Now under construction at the Lawrence Livermore National Laboratory, in Livermore, Calif., NIF is being built by the US Department of Energy as part of its Stockpile Stewardship program, and as such has a strong defense mission. "This is largely due to the fact that NIF converts its laser light to x-rays, and those x-rays are then used to implode the pellet (or perform other, classified experiments)," Dunne said. "This is meant to be analogous to the use of x-rays in thermonuclear weapons."

HiPER removes this link to defense science, Dunne said. "It uses the optical laser light directly to drive the implosion and initiate fusion. The physics associated with the interactions of lasers with matter have no relevance whatsoever to nuclear weapons, so we see this as very much a 'swords into ploughshares' undertaking."

Laser Fusion Facilities
LASER FACILITY	LOCATION	COMPRESSION ENERGY	IGNITION POWER	ESTIMATED START
National Ignition Facility	United States	1.8 MJ	NA	2009
Laser Mégajoule	France	2.0 MJ	NA	2011
FIREX-I + Gekko XII	Japan	10 kJ	1 PW (10 kJ)	2007
OMEGA EP	United States	30 kJ	2 PW (5 kJ)	2007
HiPER	Europe	200 kJ	10 PW (70 kJ)	proposed

For more information, visit: www.hiper-laser.org

Relativistic tennis with photons

Science daily news reported that a team from Advanced Photon Research Center at the Japan Atomic Energy Agency has demonstrated to generate an ultrashort and ultraintense x-ray pulse using the ordinary laser.

Sergei Bulanov of the Advanced Photon Research Center at the Japan Atomic Energy Agency in Kyoto and colleagues say they have a prototype that can generate pulses of x-ray laser light on the cheap. The researchers call their technique "relativistic tennis with photons," but a more violent analogy may better convey how it works. Suppose you throw a golf ball at a locomotive that is speeding toward you. The golf ball will bounce off it and come flying back at you with tremendous energy--just before you get run over.

The golf ball is a pulse of ordinary low-energy photons. With a tabletop setup, Bulanov and colleagues create the equivalent of a locomotive by firing a different laser into a cloud of plasma, where it creates a wake that travels at near-light speed. When the photons hit the wake, their energy increases 56-fold. They are also focused into an ultrashort, ultraintense blast by the wake, which is shaped like a miniature radar dish.

Improvement of the multipass amplifier

In order to protect the crystal, we tried many ways including decreasing the pump energy, walking away the focal point from crystal, reflecting back the pump beam, however the crystal still was burned sometimes. So this time we try to using the second beam to pump from the other side. The second was sent to dump before, now we added three mirrors to steer the beam into the crystal.

A good overview of plasma wakefield

Dr. Chan Joshi, the professor of University of California, Los Angeles, reviews recent progress in the development of plasma-based particle accelerators and considers the challenges still to be overcome to turn this concept into a practical technology for high-energy physics. This overview was published on recent CERN Courier Vol 47, No.5(2007).

(a) A simple 1D schematic of how wakefields are excited by a short-laser (top) or particle-beam (bottom) driver in a plasma. (b) 3D computer simulation of an extremely nonlinear wakefield excited by the drive beam in the "bubble" regime. The wakefield can accelerate an appropriately phased trailing beam at ultra-high gradients.

Who first observed the ponderomotive force?

In research field of high intensity laser, the ponderomotive force is the important concept. Most of us got the description from Kruer's book, in fact this phenomena was obtained at first time in 1957. From web site of Nature Physics looking back, it tells us:

In 1957, Boot and Harvie reported the observation of a force on charged particles in an inhomogeneous electric field, which originated from second-order terms of the equation for the Lorentz force on the particles. Almost immediately it was realized that this 'ponderomotive force' could be used to trap and control electrons. But the force is weak: only with the development of modern laser technology is the ponderomotive force being exploited in new particle-acceleration techniques and inertial confinement fusion.

Nature 180, 1187 (1957)

Laser-generated radiation for cancer therapy?

Will laser-generated radiation one day prove useful in cancer therapy? A UK collaboration aims to find out. Reported from oprtics.org:

A consortium of UK-based scientists has secured £5 million ($9.9 million) in research funding to turn the concept of laser-generated radiation into a robust, ready-to-go technology. The four-year project, involving researchers from nine separate institutions, could lead to cheaper, simpler solutions for proton and ion radiotherapy. Laser-energized radiation sources could also cut the cost of research into cosmic-radiation exposure from frequent air travel and manned space missions.

The project named LIBRA, which means Laser Induced Beams of Radiation and their Applications. Development of the technology will require access to a very high-powered laser with a rapid-fire repetition rate. One such system is the GEMINI laser, due to come on-line at the Rutherford Appleton Laboratory (RAL) near Oxford, UK, later this year. GEMINI is expected to deliver 1 PW (10^15 W) pulses every 20 seconds.

related links: LIBRA, GEMINI

Maintaining the cooling system for Quanta Ray - PRO

Quanta Ray lasers YAG #3 and YAG #4 could not be started, the fault signals were shown on their monitors. The possible reason is that the deionized water has not been circulated for a long time, the best way is to change the filters and refill the fresh water. We drained the water from YAG #3, and filled the vinegar for flushing the cooling system.

Theodore Maiman -- Laser Inventor Dies at 79

Theodore Maiman, PhD, inventor of the first operable laser and twice nominated for a Nobel Prize, died May 5 in Vancouver, British Columbia. His death was confirmed by his wife, Kathleen.

He had been called “the father of the electro-optics industry,” according to a biography at the IEEE virtual Museum, but Maiman considered himself "a scientist and an engineer, with research interests in electro-optics, lasers, displays and aerodynamics."

Source: Photonics.com

Low Evolution X output power

The Evolution -- the DPSS Q-switched green laser is used to pump the Ti:sapphire crystal for regeneration amplifier of 30 fs laser pulses. However its output power was dropped dramatically when we operated it this morning. The power could not be changed very much when we tuned two cavity mirrors. Later we adjusted the diodes temperature between 80F and 83F, the power just fluctuated from 22mW to 18mV when the output was set at 23%. In the normal way, the power should be around 600mW.

Ultrashort laser pulse around 100 attoseconds

Working at Italy's National Laboratory for Ultrafast and Ultraintense Optical Science in Milan (as well as laboratories in Padua and Naples), the researchers believe that their current technique will allow them to create even shorter pulses well below 100 attoseconds. Results will be presented in Baltimore at CLEO/QELS, May 6 – May 11.

Creating a single isolated attosecond pulse, rather than a train of them, is more complex. To do this, the researchers employ their previously developed technique for delivering intense short (5 femtoseconds, or millionths of a billionth of a second) laser pulses to an argon gas target. They use additional optical techniques (including ones borrowed from the research that won the 2005 Nobel Prize in Physics) for creating and shaping a single attosecond pulse. Light pulses lasting just 130 attoseconds offer possibilities for unlocking secrets of atoms and molecules.

Related Link: National Laboratory for Ultrafast and Ultraintense Optical Science
Source: PhysOrg.com

VORPAL: Versatile Plasma Simulation Code

VORPAL enables researchers to simulate complex physical phenomena in less time and at a much lower cost than empirically testing process changes for plasma and vapor deposition processes. VORPAL offers a unique combination of physical models to cover the entire range of plasma simulation problems. Laser wakefield accelerators, plasma thrusters, high-power microwave guides, and plasma processing chambers are only a few of the many applications benefiting from the powerful, parallel algorithms incorporated into the VORPAL framework. Ionization and neutral gas models enable VORPAL to bridge the gap between plasma and neutral flow physics. The software runs on a wide range of computing platforms, from desktop machines to massively parallel supercomputers with thousands of processors. The use of standard data formats allows data analysis at various levels of sophistication, including your own preferred data analysis tool.

Source: Tech-X Corporation

Dr. Eric Cornell: Searching for the Electron's Electric Dipole Moment in Trapped Molecular Ions

I joined the Physics Division Colloquium at Argonne this morning. Dr. Eric Cornell, 2001 Nobel Prize winner presented a great talking about his resent research on electron electric dipole moment (eEDM).

Searching for the Electron's Electric Dipole Moment in Trapped Molecular Ions

The current experimental upper bound on the electron electric dipole moment (eEDM) already cuts into the natural scale predicted by supersymmetry. I'll discuss an ongoing experiment in our lab to push experimental sensitivity down some two orders of magnitude. The effective electric fields inside a molecule can be thousands of times larger than in free space. A molecule with unpaired electron spin serves as our high-field lab for this benchtop particle physics experiment.

related link: Cornell Group

The crystal melting movie?

As Phy Org web reported, Stanford Synchrotron Radiation Laboratory (SSRL) researchers
have observed the atomic events involved in rapid crystal melting using an intense laser and ultra-fast x-rays.

Sub-Picosecond Pulse Source (SPPS) provides short bursts of x-rays (2 x 10^6 photons in an 80 fs FWHM pulse at 8.9 keV with a 1.5% bandwidth into a 200 um by 400 um spot). The laser pulse (50fs FWHM, 20 mJ @ 800 nm) at the sample, which convolved with the x-ray pulse yields a Gaussian cross correlation of 100 fs FWHM.

The data, published recently in Physical Review Letters, revealed that when their bonds destabilized, the atoms moved apart from each other quickly, as if repelling each other. The semiconductor material had visible melting damage after being struck by the laser.

A 32TW laser beam sending into the atmosphere

Recent paper published on APL reported the ultrahigh power laser pulses have been sent vertically into the atmosphere. Scientists from Switzerland and France sent 26J, 32TW laser pulses delivered by the Alise beamline of the CEA-CESTA into the sky. They found more than 400 self-guided filaments. The white light was observed when the laser beam propagating up to the air, beyond 20km.

If you are interested this phenomena, you may download the full text paper from the APL website.

EUV Tool Produces Images

This was just announced today on Photonics web.

The $65 million EUV ADT, developed by Netherlands-based ASML Holding NV, a supplier of advanced lithography tools, will be essential in development of the infrastructure for EUV lithography and is considered the most likely technology for insertion into manufacturing as early as the 32-nm computer chip device node, based on cost-effectiveness and ability to extend to future nodes, according to ASML.

I am very courious about this EUV source, how can they produce a 32 nm laser for lithography? There is no answer from the Photonicsweb report. I did not get answer from College of Nanoscale Science and Engineering at the University at Albany (UAlbany). Fortunately ASML tell us it's the plasma physics to produce this short wavelength:

The light source for EUV is a gas through which a high-voltage electrical charge (or high energy photons) is sent. This ionizes the gas, separating the nucleus of the atoms from the electrons, thereby creating a plasma, a very hot cloud of ions. As the electrons attempt to return to the nucleus, they emit a burst of light, which has a very short wavelength of 13.5 nm.

For more information visit: EUV Lithography: The next generation

Please visit new blog -- Femtosecond KrF Excimer Laser

I applied blog space for Femtosecond KrF Excimer Laser system at UIC. This blog will concern about the ultrafast high field laser and its applications. Every UIC laser lab member can post in the new blog, the URL is http://uicexcimer.blogspot.com/.

What Is an Energy Recovery Linac (ERL)?

An Energy Recovery Linac (ERL) x-ray source is a candidate next-generation x-ray source technology now under active development. ERLs are made possible by recent advances in superconducting linear accelerators and in high-brightness electron sources. ERLs have the potential to generate synchrotron radiation with brightness about 1000 times greater than that of today's storage rings, resulting in highly coherent x-radiation. ERL's are particularly well suited for the production of very fast x-ray pulses to examine the dynamics of materials on extremely rapid time scales and for intense x-ray nanoprobe beams to study nanoscopic matter. While both ERLs and XFELS will be able to produce very fast x-ray pulses, the two sources are quite distinct in the timing of these pulses: ERLs are being designed to produce pulses times up to a billion times a second whereas XFELs produce bigger pulses but at a far lower rate per second.

Image 1. Electrons are released from the injector at the lower left, and are accelerated in a long linear superconducting accelerator (main linac). After emerging from this linac, the electrons pass through undulators that wiggle the electron beam and produce the x-rays in the usual way. Electrons are continuously injected, make one trip around the ring, and return to the main linac where their energy is recovered. The spent beam is directed to the dump. (Courtesy: Cornell University)

PHOTONIC FRONTIERS: PETAWATT LASERS

Squeezing energetic laser pulses down to ultrashort durations can generate tremendous peak powers. A decade ago the Lawrence Livermore National Laboratory (LLNL; Livermore, CA) blazed the trail by modifying one arm of its Nova fusion laser to create the Petawatt Laser, which delivered pulses exceeding 1015 W (1 PW). Now some 20 petawatt lasers are in operation or development around the world, and European planners are aiming for an exowatt (1018 W) laser (see table).

Some major petawatt laser projects

Name	Site	Timetable	Parameters	Web site Link
Advanced Radiographic Capability	Livermore	2009	10 kJ, 10 ps
Extreme Light Infrastructure	Laboratoire d’Optique Appliquée, France	Proposal	10 kJ, 10 fs	ELI
Firex-1	ILE, Osaka, Japan	Under construction	10 kJ, 10 ps
GEKKO Petawatt Module	ILE, Osaka, Japan	In operation	500 J, 500 fs
Laser Megajoule	University of Bordeaux	Proposal	2 MJ, 300 ps-10 ns	lmj
LULI 2000	LULI, Paris	Under construction; completion 2006	200 J, 400 fs
Omega EP	University of Rochester	2007	2.6 kJ, 1 ps	omegaep
Petawatt Laser (original)	Livermore	1996-1999	1.3 kJ, 800 fs	MPerry
Phelix	GSI Darmstadt, Germany	Under construction, with heavy-ion beam	500 J, <500 fs	phelix
Polaris	University of Jena, Germany	Development	120 J, 120 fs	ultraphotonics
Texas Petawatt Laser	University of Texas, Austin	Late 2007	130 J, 150 fs	petawatt
Titan	Livermore	In operation	400 J, 400 fs or long-pulse	JLF
Vulcan Petawatt	Rutherford Appleton Lab, UK	In operation	400 J, 400 fs	vulcan
Z-beamlet	Sandia National Laboratory	Under construction	2 kJ, 1-10 ps ultimately	z-beamlet

The first petawatt laser

Livermore’s Petawatt Laser used a chain of Nd:glass lasers from one beam of the Nova fusion laser to amplify nanosecond pulses to the kilojoule range. Pulses were expanded and compressed with high-efficiency 75 cm gratings. Amplifier output of 1.3 kJ in an 800 ps pulse could be compressed down to a 430 fs pulse with peak power of 1.3 PW, which in turn could produce power density approaching 1021 W/cm2. The system generated its first petawatt pulse on May 23, 1996, and ran for three years until Nova was dissembled in 1999.

The Livermore experiments demonstrated the potential of petawatt lasers to concentrate tremendous energies into small volumes, opening a new regime of high-temperature and high-pressure matter for study. The intense fields could accelerate both electrons and positive ions to high velocities over short distances (see www.laserfocusworld.com/articles/252490). Experiments generated bright beams of high-energy x-rays and gamma rays. And Livermore also showed that firing petawatt lasers into a laser-heated fusion target produced a powerful shock wave that helped ignite the fusion fuel.

Second-generation petawatt lasers

The second generation of petawatt lasers is already operating. The Rutherford Appleton Laboratory (Didcot, England) uses a Ti:sapphire oscillator and an optical parametric amplifier to preamplify pulses which then pass through a beam of the lab’s Vulcan Nd:glass laser, and three additional 208 mm Nd:glass disks salvaged from Nova (see Fig. 2). Commissioned in 2002, it initially produced 800 fs pulses with peak power of 500 TW. Further refinements ramped up power, which reached the petawatt level in October 2004, delivering 423 J onto the target in a 410 fs pulse.

Livermore has built a second-generation petawatt laser called Titan around the old two-beam Janus Nd:glass laser used in fusion target experiments back in 1975, says Andrew Ng of Lawrence Livermore National Laboratory (LLNL). Overhauled with better glass, the system has two independent beam lines for chirped-pulse amplification and a new generation of pulse-compression gratings. The first experiments in June 2005 generated 400 J in 400 fs to reach petawatt peak power focusable onto an 8 µm spot. It also can operate in long-pulse mode, generating 1 kJ in less than 3 ns or 140 J in 250 ps. Titan can fire long and short pulses simultaneously from its two arms. Ng says that firing long pulses to create a plasma and short pulses to probe the plasma is a very effective way to study high-energy states.

Livermore is also planning a big step up in energy with a second long-pulse system for use with the National Ignition Facility. Called the Advanced Radiographic Capability, it initially will fire 1 kJ pulses to record multiframe x-ray movies of NIF targets, says lead scientist Chris Barty of LLNL. By combining four NIF beams, he hopes to generate 13.2 kJ in a 10 ps pulse. The first beamline is to be commissioned in spring 2009.

Most other systems in operation, construction, or planning stages are either long-pulse systems based on Nd:glass or Ti:sapphire systems generating pulses as short as 20 fs. The main exception is the $15 million Texas Petawatt Laser, which will use parametric amplification to raise the 1 J output of a Ti:sapphire oscillator to 250 J, which they hope to deliver in 150 fs pulses. Project director Todd Ditmire hopes to produce his first petawatt pulses late in 2007.

Laser Focus World August, 2006
Author: Jeff Hecht

Counterpropagating light opens door to tabletop X-ray laser

A team of researchers at the University of Colorado at Boulder has developed a new technique to generate laser-like X-ray beams, removing a major obstacle in the decades-long quest to build a tabletop X-ray laser that could be used for biological and medical imaging.

A paper on the subject by Murnane and Kapteyn, CU-Boulder graduate students Xiaoshi Zhang, Amy Lytle, Tenio Popmintchev, Xibin Zhou and Senior Research Associate Oren Cohen of JILA was published in the online version of the journal Nature Physics on Feb. 25.

Source: University of Colorado at Boulder