Diode Lasers: A Versatile Clinical Tool International Journal of Laser Dentistry, September-December 2011;1(1):9-15 9 IJOLD Diode Lasers: A Versatile Clinical Tool (A Technical and Clinical Review) M Alex Mathews Professor, Department of Prosthodontics, PMS College of Dental Sciences and Research, Thiruvananthapuram, Kerala, India Correspondence: M Alex Mathews, Professor, Department of Prosthodontics, PMS College of Dental Sciences and Research Thiruvananthapuram, Kerala, India, e-mail: alexmuruppel@gmail.com REVIEW ARTICLE INTRODUCTION Diode lasers have been a singular innovation and invention that has transformed scenarios in optical fiber based telecommunications, information technology and inevitably augmented and enhanced medical and dental practice. Theodore Maiman in 1960 (at Hughes research laboratory) heralded the birth of modern laser science with the epoch breakthrough of the Ruby laser (694 nm), but the first successful operation of diode laser was reported only in 1962 by several research groups (one of them being GE). Albeit the first emission of light by a semiconductor was by HJ Round in 1907 (Elect World 1907, 19:309) using the compound silicon carbide by the phenomenon of electroluminescence, Basov et al had suggested in 1961 that stimulated emission could occur in a semiconductor by the recombination of charge carriers across a p-n junction or homojunction diodes (Chow and Koch, semiconductor-laser fundamentals: Physics of the gain materials, Springer). Subsequent innovations saw the advent of the heterostructure/ heterojunction diode laser in 1969 from the combined research of Herbert Kroemer and Zhores Alferov (Nobel Prize in 2000). 1 SYNONYMS AND ADVANTAGES As with any popular and universally accepted instrument or technology, the diode laser may be also termed variously as semiconductor lasers or laser diodes or injection lasers as opposed to the other solid state lasers which are termed pumping lasers as they have to be externally stimulated by a strobe lamp or a diode laser itself. They may also be termed as homojunction or heterojunction diodes depending on the type of semiconductor chip that serves as the lasing ‘active’ medium. The semiconductor chip itself could be surface emitting or edge emitting and could be termed likewise. Double heterostructure lasers, quantum well lasers, quantum cascade lasers, distributed feedback lasers, VCSEL (vertical-cavity surface-emitting laser) and VECSEL (vertical-external-cavity surface-emitting laser) are the more modern and latest versions of the diode laser. 1 The diode lasers are semiconductor devices which operate from a standard AC electrical outlet with a relatively high power output. The external electrical power supply delivers the excitation required to facilitate stimulated emission and thus lasing. They have high electrical to optical efficiency, are small, lightweight and compact, hence, portable and are quiet devices as compared to the other solid-state and gas lasers (such as Nd YAG, KTP.YAG, Ho YAG, Argon, Erbium family and CO 2 ) which are bulky and difficult to transport, may have a warm- up time of several minutes and require a cooling system as well as requiring regular maintenance. 2 The diode lasers on the other hand are relatively maintenance free, reliability studies have shown a mean time to failure of 25,000 hours at maximum output power. 2 DIVERSITY AND VARIATION High power diode lasers are available over a wide range of wavelengths from 600 to 1060 nm. The wavelength of a diode laser is determined by the active compound used in the semiconductor. There are small but significant differences in the effects on tissue across these wavelengths due to the differing absorption properties of blood and the peak in the water absorption spectrum being at 975 nm. Diode lasers are fast becoming part of contemporary clinical practice and have since opened up vistas of unprecedented patient care. However, the nuances of their functioning and mechanisms of tissue interaction have not been widely discussed or clearly elucidated. This paper assimilates the facts in literature and throws light on the basics and essentials of this technological advancement that indeed has become a boon to all walks and branches of science. Keywords: Diode lasers, Isosbestic point, Hemostasis, LLLT. ABSTRACT Wavelength range Semiconductor alloy Periodic group (μm) 0.65-0.69 InGaAlP/AlGaAs — 0.76-0.82 AlGaAs III-V (NIR) 0.97-1.1 InGaAs III-V (NIR) 1.1-1.8 InGaAsP III-V (NIR) 2-4.5 AIGaAsSb/PbCdS III-V (MIR) 3-30 PbTeSn IV-VI (MIR) 10.5005/jp-journals-10022-1002