Published January 07, 2001
The briefest events ever created by man may be the longest lasting effects for mankind. If you blink, you’ll certainly miss it.
Ultra short laser pulses surpass ordinary laser light for their phenomenal characteristics. The process being developed will benefit medicine, chemistry, biology, music, communications, and manufacturing.
Researchers Wayne Knox, Martin Nuss and their team at Lucent Technology’s Bell Laboratories, are pursuing the futuristic dream of fiber-optic lines for communications to everyone’s home. First step is to devise a means for sharing one strand of the light cable, kind of a private, infinite party line.
A technique being expanded is combining many high-speed data streams, a process called Wavelength Division Multiplexing (WDM). Each person’s data, for telephone, television and Internet, will stream along the strand of glass on specific and separate frequencies of light called wavelengths.
All the beams combine along the way and are separated at the end point. The serious problem with this existing technology is that it requires about 100 lasers and modulators providing only 1,021 distinct color frequencies.
The theoretical maximum personal channels with the new pulse lasers is well more than 16 million on each hair-sized strand of fiber. A huge economic plus is that this new process needs only one pulse laser.
Mr. Knox envisions the first generation of these new lasers will handle 15,000 different channels, each at 1,000 million bits of data per second. Compare that to your dialup modem today of less than 56,000 bits per second. Expect the first delivery of these in about 2004 when you’ll be issued your own wavelength.
These incredibly fast laser pulses illuminate tiny things in a series of fast snapshots by doing violence to them. Information from this segment of research alone is worth millions of dollars in producing new drugs.
They’re called femtosecond titanium sapphire lasers. The duration of their pulses is only 25 quadrillionth of a second (10-16). Think of it as the division of a second into slivers of time equal to approximately the same number of letters in 224 million Bibles. That is very small, indeed!
Ukrainian emigrant Victor Yanofsky at the University of Michigan in Ann Arbor is working on a very powerful femtosecond laser. When completed in June for astrological study, his will generate 100-terawatts of power, or 33 times greater than all the generating capacity on Earth. However, since this massive energy is only a very brief pulse, the total heat would only raise the temperature of a cup of coffee six thousandth of one degree.
The scientists inform us that pulse lasers are significant for a number of reasons. Yanofsky says, “This is like a bridge from conventional optics to nuclear physics.”
Physicists at the University of Osaka, Japan, have used a femtosecond laser to energy-boost the yield of a laser-fusion experiment. University of Texas at Austin representative emphasizes that it’s too soon to verify practical results, but this could have an enormous impact on fusion power generation research.
A femtosecond is to the blink of an eye what the blink of an eye is to two million years. The record for the shortest laser pulses is 4.5-femtosecond by the University of Groningen, Netherlands, in 1999. Researchers are attempting a 2-femtosecond pulse which is a single cycle at the frequency of light.
The garden-variety femtosecond lasers, for other laboratory experiments, are sufficiently strong to focus themselves in air, ripping electrons off molecules and producing a lightning-like effect.
Complex chemical reactions are studied that transpire too rapidly to otherwise observe. A laser pulse striking a molecule breaks it apart, illuminating new microscopic fragments in a sequence of images like a movie. Scientists revel at understanding the transformations that could not be intuited from the final outcome.
In industry, femtosecond lasers will very accurately cut and drill materials without melting the edges, as typical lasers do now. The pulsing blasts converts the hairline slice into gas under such high pressure that the energy is evacuated away at supersonic speeds.
Auto-makers are testing femtosecond lasers to drill precise microscopic holes in fuel injector nozzles for better atomization, cleaner burn and fuel economy.
Similarly, dentists drills would be painless: No heat, no pain! In biomedicine, safer and smoother shaped stents, the small cylindrical tubes that hold blood vessels open, are being investigated.
In music, these same pulse lasers can be adapted to analyze musical notes for the multiple complexity of overtones and harmonic reverberations present. The objective would be to accurately compare instruments or synthetically create music from a computer that sounds absolutely real.
Calibrated femtosecond pulses direct their energy below the surface, leaving the surface unaltered. Only tiny volumes of material are zapped from inside a piece of ornamental glass or even the cornea of the eye.
Yes, ophthalmologists performing conventional LASIK “flap and zap” corrective-vision eye surgery may soon eliminate cutting the outer cornea layer. Because nothing but the laser light touches the eye, complications such as infections and ingrowths are greatly reduced.
Intralase has pioneered the use of femtosecond lasers, replacing the excimer laser, to minutely reshape the eye’s cornea. Tiny amounts of tissue are removed below the surface. Although the company has USDA approval and prototypes are at two centers, in San Diego and Houston, more research is needed.
Meanwhile, others researchers are experimenting with X-rays which suggest the possibility of attosecond pulses, a thousand times shorter than femtosecond. Yes, there are still smaller units of measure: zepto- and yocto-, respectively.
Back in 1958, Arthur Schawlow and Charles Townes published the basic principals of the laser. They were amused that it was “a solution looking for a problem.” No one could have envisioned the far-reaching adapation of their most significant scientific contribution.