ABSTRACT
Since the first hair-removal laser system was cleared by the US Food and Drug Administration (FDA) in 1995, many technological advances have been made in this field. Today, photoepilation is one of the most effective methods of achieving long-term hair reduction. This procedure has rapidly become an integral part of dermatology. In order to understand this procedure, one must have knowledge of hair biology, lasers, and light sources. In this chapter, the basics of photoepilation are reviewed. LASER is an acronym for light amplification by the stimulated
emission of radiation. The four major components of a laser system are a power source, an active medium, an optical resonator, and a delivery system. The power source supplies energy to excite the molecules within the medium. A population inversion occurs when a majority of the molecules within a medium are in the excited state. This is an essential step for the production of laser light. The medium can be a gas, liquid, solid or a semiconductor. Lasers are often named after their medium, which also determines the primary emission wavelength. The optical resonator provides a feedback mechanism in which laser energy can return to the medium and stimulate more excited molecules to emission. Its main function is to multiply the number of passes through the medium, generating a highly directional and intense light beam. Finally, the delivery system guides the light energy from the laser onto the skin (Figure 18.1). As a result of this amplification process, light energy emitted by lasers has three unique properties: it is identical in wavelength (monochromaticity), phase (coherence), and direction (collimation).1 These qualities are ideal for targeting specific chromophores within the skin. Intense pulsed light (IPL) has also been cleared by the FDA for
hair removal. In the past decade, this device has become increasingly popular due to its versatility in assuming the function of various lasers. IPL is a broad spectrum light source that contains many different wavelengths. Filters are used to narrow the spectrum
of light emitted and can be changed depending upon the clinical situation.
