David J. Goldberg (editor) - Laser Dermatology

Department of Dermatology, Mohs and Dermatologic Surgery at College Park Family Care Specialty Center, University of Kansas Medical Center, Overland Park, KS, USA

Consultant in Mohs and Laser Surgery, Tuscon, AZ, USA

Holly H. Hare (Corresponding author)

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Ronald G. Wheeland

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Light is a very complex system of radiant energy that is composed of waves and energy packets known as photons. It is arranged into the electromagnetic spectrum (EMS) according to the length of those waves. The distance between two successive troughs or crests of these waves, measured in meters, determines the wavelength . For the visible portion of the EMS, the wavelength determines the color of the laser light. The number of wave crests (or troughs) that pass a given point in a second determines the frequency for each source of EMS energy. The wavelength and frequency of light are inversely related to one another. Thus, shorter wavelengths of light have higher frequencies and more energenic photons than longer wavelengths of light which have lower frequencies and less energenic photons.

One must go back to about 4000 B.C. in ancient Egypt to find the earliest recorded use of light. At that time sunlight was coupled with a topical photosensitizer, like parsley or other herbs containing psoralen, to help repigment the skin of individuals suffering from vitiligo, a disorder in which the skin becomes depigmented through a presumed autoimmune reaction. In Europe in the nineteenth century, sunlight was used as a treatment for cutaneous tuberculosis. However, it wasnt until 1961 that Dr. Leon Goldman, a dermatologist at the University of Cincinnati, first employed a ruby laser for the removal of tattoos and other pigmented cutaneous lesions. For his continuous efforts in promoting the use of lasers for medical purposes and for co-founding the American Society for Laser Medicine and Surgery, Dr. Goldman (Goldman et al. ).

Professor Albert Einstein (Einstein) published all of the necessary formulas and theoretical concepts to build a laser in his 1917 treatise called The Quantum Theory of Radiation. In this treatise, he described the interaction of atoms and molecules with electromagnetic energy in terms of the spontaneous absorption and emission of energy. By applying the principles of thermodynamics he concluded that stimulated emission of energy was also possible. However, it wasnt until 1959 that Drs. Charles H. Townes and Arthur L. Schawlow (Schawlow) developed the first instrument based on those concepts, known as the MASER ( M icrowave A mplification through the S timulated E mission of R adiation). In 1960, the first true laser, a ruby laser, was operated by Dr. Theodore H. Maiman (Maiman). Rapidly the development of additional lasers occurred with the helium-neon laser appearing in 1961, the argon laser in 1962, the carbon dioxide and Nd:YAG laser in 1964, the tunable dye laser in 1966, the excimer laser in 1975, the copper vapor laser in 1981, the gold vapor laser in 1982, and many others since then including the alexandrite laser, pulsed dye laser, erbium laser, holmium laser, diode laser, and titanium:sapphire laser. In addition, modifications to existing lasers have occurred, including Q-switching of the ruby, Nd:YAG and alexandrite lasers; fractionating the carbon dioxide laser; and adding dynamic cooling to the pulsed dye laser.

The word LASER is an acronym that stands for L ight A mplification by the S timulated E mission of R adiation. For this reason, a laser is not just an instrument but also a physical process of amplification (Table ). The last word in the acronym, radiation, is a common source of patient anxiety since it can be associated with the high energy ionizing radiation often used for cancer radiotherapy. However, in the case of lasers, the word is employed to describe how the laser light is propagated through space as radiant waves. Patients should be assured that all currently approved medical lasers are incapable of ionizing tissue and have none of the risks associated with the radiation used in cancer therapy.