page_title: Ruby laser
section_title: History
hierarchical_section_title: Ruby laser / History
caption_attribution_description: English: A homemade laser pistol that shoots a laser beam, constructed by Stanford University physics professor K. H. Sherwin in 1964, four years after the laser was invented, to demonstrate to his classes how lasers work. The body (left), recycled from a toy raygun, holds a pencil size ruby rod and two flashtubes.(right). It is attached by wire to a 200 watt-second high voltage power supply. When the trigger is pulled, the flashtubes go off, creating a pulse of red laser light from the rod. The coherent light pulse is powerful enough to pop a blue balloon (shown at left); but not a red one, since it reflects the red light. Alterations to image: cleaned up some dark areas around the circuit board on the left that looked to be artifacts from the page scan.
context_page_description: A ruby laser is a solid-state laser that uses a synthetic ruby crystal as its gain medium. The first working laser was a ruby laser made by Theodore H. "Ted" Maiman at Hughes Research Laboratories on May 16, 1960.
  Ruby lasers produce pulses of coherent visible light at a wavelength of 694.3 nm, which is a deep red color. Typical ruby laser pulse lengths are on the order of a millisecond.
context_section_description: The ruby laser was the first laser to be made functional. Built by Theodore Maiman in 1960, the device was created out of the concept of an "optical maser," a maser that could operate in the visual or infrared regions of the spectrum. 
  In 1958, after the inventor of the maser, Charles Townes, and his colleague, Arthur Schawlow, published an article in the Physical Review regarding the idea of optical masers, the race to build a working model began. Ruby had been used successfully in masers, so it was a first choice as a possible medium. While attending a conference in 1959, Maiman listened to a speech given by Schawlow, describing the use of ruby as a lasing medium. Schawlow stated that pink ruby, having a lowest energy-state that was too close to the ground-state, would require too much pumping energy for laser operation, suggesting red ruby as a possible alternative. Maiman, having worked with ruby for many years, and having written a paper on ruby fluorescence, felt that Schawlow was being "too pessimistic." His measurements indicated that the lowest energy level of pink ruby could at least be partially depleted by pumping with a very intense light source, and, since ruby was readily available, he decided to try it anyway.
  Also attending the conference was Gordon Gould. Gould suggested that, by pulsing the laser, peak outputs as high as a megawatt could be produced. 
  As time went on, many scientists began to doubt the usefulness of any color ruby as a laser medium. Maiman, too, felt his own doubts, but, being a very "single-minded person," he kept working on his project in secret. He searched to find a light source that would be intense enough to pump the rod, and an elliptical pumping cavity of high reflectivity, to direct the energy into the rod. He found his light source when a salesman from General Electric showed him a few xenon flashtubes, claiming that the largest could ignite steel wool if placed near the tube. Maiman realized that, with such intensity, he did not need such a highly reflective pumping cavity, and, with the helical lamp, would not need it to have an elliptical shape. Maiman constructed his ruby laser at Hughes Research Laboratories, in Malibu, California. He used a pink ruby rod, measuring 1 cm by 1.5 cm, and, on May 16, 1960, fired the device, producing the first beam of laser light. 
  Theodore Maiman's original ruby laser is still operational. It was demonstrated on May 15, 2010 at a symposium co-hosted in Vancouver, British Columbia by the Dr. Theodore Maiman Memorial Foundation and Simon Fraser University, where Dr. Maiman was Adjunct Professor at the School of Engineering Science. Maiman's original laser was fired at a projector screen in a darkened room. In the center of a white flash (leakage from the xenon flashtube), a red spot was briefly visible.
  The ruby lasers did not deliver a single pulse, but rather delivered a series of pulses, consisting of a series of irregular spikes within the pulse duration. In 1961, R.W. Hellwarth invented a method of q-switching, to concentrate the output into a single pulse.
  In 1962, Willard Boyle, working at Bell Labs, produced the first continuous output from a ruby laser. Unlike the usual side-pumping method, the light from a mercury arc lamp was pumped into the end of a very small rod, to achieve the necessary population inversion. The laser did not emit a continuous wave, but rather a continuous train of pulses, giving scientists the opportunity to study the spiked output of ruby. The continuous ruby laser was the first laser to be used in medicine. It was used by Leon Goldman, a pioneer in laser medicine, for treatments such as tattoo removal, scar treatments, and to induce healing.  Due to its limits in output power, tunability, and complications in operating and cooling the units, the continuous ruby laser was quickly replaced with more versatile dye, Nd:YAG, and argon lasers.
caption: Ruby laser pistol constructed by Stanford Univ. physics professor in 1964 to demonstrate the laser to his classes.  The plastic body recycled from a toy raygun contained a ruby rod between two flashtubes (right).  The pulse of coherent red light was strong enough to pop blue balloons (shown at left) but not red balloons which reflected the light.
exif: {}