May 12 2010
Researchers from around the world will present the latest breakthroughs in electro-optics, innovative developments in laser science, and commercial applications in photonics at the 2010 Conference on Lasers and Electro-Optics/Quantum Electronics and Laser Science Conference (CLEO/QELS) May 16 to 21 at the San Jose McEnery Convention Center in San Jose, California.
Research Highlights of the Meeting:
- Brightest X-ray Machine in World Probes Molecules
- Single-Cycle Infrared Light Pulses
- Using Light to Inscribe Tiny Nanoscale Plastic Parts
- Laser Cooling of Solids for Sensitive Sensors
- Tunable Terahertz Wire Laser
- Speeding-Up Broadband Spectroscopy
- CLEO/QELS Plenary Sessions
BRIGHTEST X-RAY MACHINE IN WORLD PROBES MOLECULES
The Stanford Linear Accelerator Center (SLAC), long the preserve of particle physics, is also a major laboratory for conducting experiments in fields like biology and medicine. The electron acceleration equipment has been adapted over the past few years to create something known as the Linac Coherent Light Source (LCLS), which produces short X-ray pulses millions of times brighter than those currently created by other instruments.
The LCLS is the brightest X-ray machine in the world for the energies at which it operates -- with photon energies in the "hard X-ray" region and very high beam intensities of 10^18 watts per square centimeter. At these energies, the LCLS machine can serve as an excellent microscope for viewing matter at the scale of atoms, and biologists, chemists, and physicists have been eager to do exactly that. It also acts like a knife since it can pare electrons away from the parent atoms and molecules, even those huddling very close to the nucleus.
Becoming operational last fall, the first experimental results from the LCLS are starting to appear at scientific meetings. In San Jose, Li Fang of Western Michigan University will report on how the powerful LCLS X-rays can be used to strip electrons away from a nitrogen molecule. He says that in the extreme case, nitrogen atoms were detected from which all of the electrons had been removed. This causes the molecule to quickly dissociate. The plucked electrons, which nearby detectors can spot and measure, allow researchers to calculate the binding energy within the original molecule. In future experiments, more and more such measurements will give experimenters a more accurate assessment of large molecules, especially bio-molecules.
Presentation JFA5, "Nonlinear Processes in N2 Using LCLS Short X-Ray Pulses," by Li Fang et al. is at 9:15 a.m. Friday, May 21.
SINGLE-CYCLE INFRARED LIGHT PULSES
A pulse of light normally has many cycles of smoothly varying electric and magnetic fields. Through the use of special fibers, prisms, and optical materials, a pulse of light can be compressed down to very short temporal durations, even as short as a single cycle (only one complete wavelength of radiation).
A major reason for wanting shorter light pulses is that more data can be encoded within a signal lasting a certain interval of time. Shorter pulses would allow more data to be sent down an optical fiber, for example. Another important scientific use of very short pulses is that they can serve as a stroboscopic illumination for making movies of very short-lived phenomena, such as the movement and interactions of molecules.
Scientists at the University of Konstanz in Germany are the first to report creating a single-cycle pulse as short as 4.3 femtoseconds in the infrared region of light (which is the crucial type of light for communications applications) around 1.3 microns in wavelength. Guenther Krauss, who works with Alfred Leitenstorfer in the Department of Physics, says that another distinction of the light is that it has the highest frequency ever achieved for single-cycle pulses.
With such short light pulses, the data transmission rate for applications like the Internet might reach rates of 100 terabits per second, says Krauss. Furthermore, the femtosecond (10^-15 seconds) pulses created in the current experiments might serve as the seed for making even shorter pulses in the attosecond (10^-18 seconds) domain.
Presentation CWJ1, "Single-Cycle Light Pulses from a Compact Er: Fiber Laser," by Guenther Krauss et al is at 4:45 p.m. Wednesday, May 19.
USING LIGHT TO INSCRIBE TINY NANOSCALE PLASTIC PARTS
One of the biggest obstacles in microscopy and in micro-fabrication is the so-called diffraction limit. This basic law says that the resolution (or sharpness) of an image cannot be better than approximately half the wavelength of the light waves being used to make it. Similarly, when light is used to inscribe patterns on microchips -- a standard process known as lithography -- these features can't get much more narrow than about a quarter the wavelength of the light.
Now scientists at the University of Maryland have pushed this limit, achieving pattern features with a size as small as one-twentieth of the wavelength.
They do this by a clever use of two laser beams racing through a polymer solution. One beam triggers polymerization (long molecules start to link up into even longer molecules) while the other beam turns the process off. Polymerization of very narrow pillars -- much narrower than the wavelength of the light -- occurs in a tiny overlap region between the beams.
The leader of this effort, John Fourkas, says that the size of the tiny polymer structures probably represents the smallest fraction of the incoming radiation wavelength ever realized in the laboratory.
One of the structures made in the Maryland lab is a sphere-like post only 40 nanometers tall (about a million times shorter than the length of a 12-point hyphen "-"). If the polymer structures could be made conducting, then they could possibly be used in making microchips. More likely, Fourkas says, are applications in the area of biochemistry. Since the polymer structures are much smaller than typical cells, they might be used to study cell function. For example, cells could be made to "walk over" the structures, which could be used to trigger a chemical or biological response from the cell.
Additionally, the tiny polymer structures might be useful in adhesives or as channels on microfluidic chips -- little platforms on which chemical reactions can be carried out with nano-liter batches of fluids.
Presentation JTuA1, "High Resolution 3-D Laser Direct-Write Patterning" by John T. Fourkas et al. is at 8 a.m. Tuesday, May 18.
Source: http://www.osa.org/