Ultrafast Processes
Ultrafast optical phenomena refer to dynamical processes that occur in various forms of matter on the time scale of picoseconds or femtosecond. These phenomena have been relegated to the optical domain primarily because only lasers have been fast enough to probe many of these processes. This field of ukrtiast optical phenomena continues to be a highly prolific field of fundamental and applied research. One of the prime driving forces for the continued growth is the seemingly unending appearance of new and exotic sources of ultra short pulses and the concomitant proliferation of commercially available sources. Today, one can literally buy the pro-verbial “black-box” with the attached label – “femtosecond pulses exit here.”Driven by unprecedented levels of coherence, bandwidth, spectral diversity, high power, and small size, ultra short pulses of light have been utilized in fundamental studies of disciplines as diverse as semiconductor physics, plasma physics, Light wave transmission systems, and biological systems. In 1987, the Bell Labs group headed by Shank and Fork generated 6 fs du-ration optical pulse by coupling 30 fs, 2 TW/cm2 pulses (TW=Terawatt=l 012Watts) from an amplified colliding pulse mode locked (CPM) dye laser into a1-cm single-mode optical fibre and prism-grating compressor. After a decade of intense activity, tis 6 fs world record was finally broken by Wiersma’s group in The Netherlands – 5 fs via the fibre-prism-grating compression of in-tense 13 fs pulses fi-om a cavity-dumped Kerr-lens mode locked (KLM) Ti: sapphire laser. Limitations on the simultaneous control of the intracavity bandwidth and dispersion of KLM Ti:sapphire lasers has thus fw prevented the generation of pulses shorter than 7.5 fs directly from the laser oscillator –despite the fact that one can generate enough bandwidth in this laser system to support a 4 fs pulse!
SOME EXAMPLES OF ULTRAFAST PROCESSES
VIBRATION OF SMALL MOLECULES
FRAGMENTATION OF MOLECULES
ATOM-ATOM COLLISION
SOME OF THE OTHER ULTRA FAST PROCESSES
PROBING OF ULTRAFAST PROCESSES
The processes that occur in picoseconds and femtosecond time domain are called as ultrafast processes. So in order to study the dynamics of these fast processes we have to have a probing system in the same time domain. Ultrafast femtosecond pulses are used for the direct observation in the time scale for monitoring the physical and biological systems.
Ultra short laser pulses are considered to be those whose pulse duration is less than a few picoseconds (10-12 s) long. Recent research has led to techniques such as Kerr-lens mode locking to enable pulse duration down to around 5 femtoseconds (10-15 s) and chirped pulse amplification giving pulses peak powers of several terawatts.
Infra-red spectroscopy was first used in 1950's by Wilbur Kaye. He designed a machine that tested the near-infrared spectrum and was able to provide the theory to describe the results. There have been many advances in the field of IR Spec, the most applicable was the application of Fourier Transformations. ”The Fourier Transform is a tool that breaks a waveform (a function or signal) into an alternate representation, characterized by sine an...
Berger, E., Fox, D. B., Price, P. A., Nakar, E., Gal‐Yam, A., Holz, D. E., & Songaila, A. (2007). A New Population of High‐Redshift Short‐Duration Gamma‐Ray Bursts. The Astrophysical Journal.
Summary of Clock Speed: Winning Industry Control in the Age of Temporary Advantage by Charles H. Fine
to be done. This was to find out what amount of each liquid would be
In September 1959 DiVita asked 2nd Lt. Richard Sturzebecher if he knew of a way to produce a strong glass fiber that would be capable of carrying a light signal. Sturzebecher had melted 3 triaxil glass systems together for his senior exam at Alfred University. In his exam, Sturzebecher had used SiO2, a glass powder produced by Corning. Whenever he had tried to look at the substance through a microscope he would end up with headache. Sturzebecher realized that these headaches came from the high amounts of white light produced from the microscopes light that was reflected through the eyepiece via the SiO2. SiO2 would be an ideal substance for transmitting strong light signals if it could be developed into a strong fibre.
After excitation various relaxation processes typically occur in which other photons are once again radiated. The time periods between absorption and emission may vary: ranging from short femto seconds to milliseconds for phosphorescent processes in molecular systems .Delay of emission may sometimes even last for minutes or hours.
Throughout different experiments, scientists have discovered that light behaves as both a wave and a particle in different circumstances. The only way that all of the properties of light can be explained is through the idea of a wave-particle duality.
Serway, Raymond A, and Robert J Beichner. Physics: For Scientists and Engineers. United States of
American Institute of Physics. Vol. 1051 Issue 1 (2008). Academic Search Premier.> 224. http://login.ezproxy1.lib.asu.edu/login?url=http://search.ebscohost.com.ezproxy1.lib.asu.edu/login.aspx?direct=true&db=aph&AN=34874307&site=ehost-live.
states strikes an excited atom, the atom is stimulated, as it falls back to a
I am writing to inform you of a recent economic opportunity that could leave you rich if you choose to invest. The prospect of wealth relies on superconductors- the system of the future and present. You could earn millions by contributing to the research of superconductors.
Nanotechnology is science, technology and engineering that is conducted at the nanoscale. The nanoscale is about 1 to 100 nanometres.
A processor is the chip inside a computer which carries out of the functions of the computer at various speeds. There are many processors on the market today. The two most well known companies that make processors are Intel and AMD. Intel produces the Pentium chip, with the most recent version of the Pentium chip being the Pentium 3. Intel also produces the Celeron processor (Intel processors). AMD produces the Athlon processor and the Duron processor (AMD presents).
Refraction is a process that occurs when light travels between media of different optical density. Light travels at a speed of roughly 3.0 × 108ms-1 in a vacuum. A vacuum has a refractive index n=1.00. The speed at which the light is travelling will decrease as it moves into differently optically
Fiber optics is a new technology that uses rays of light instead of electricity to transmit information over optical fibers at very high speeds. The optical fibers are usually thin strands of glass that are combined into cables and used to send information and computer data in the form of pulses of light. The optical fibers provide much clearer transmission than conventional copper cable and satellite links. The world market for optical fiber continues to grow rapidly, with shipments increasing 14 percent from an estimated 7.0 million kilometers of fiber in 1990 to approximately 8.0 million in 1991. The demand for multimode fiber is predicted to continue to expand through the mid-1990s, with some market analysts indicating that 15 to 20 percent annual growth over the next three years is reasonable. Strong demand is expected for singlemode and multimode fiber to be used in cables for local area networks, telecommunications, cable television (CATV), and transoceanic fiber-optic systems.