This looks to be the case for the foreseeable future, owing to a favorable combination of output format, operating wavelength, relatively high efficiency, ruggedness, compact size, and reliability. Maiman, 1960, “Stimulated optical radiation in ruby” Nature 187(4736): 493.Įmploy either diode or solid-state lasers, with the latter often combined with nonlinear optics. At this point, with a few exceptions, sensors nowġ T.H. Since 1960, almost every type of laser has been employed in demonstrations of active EO sensors. 1 With the development of techniques to generate nanosecond-duration pulses, ruby lasers provided the first example of laser rangefinders. The use of lasers for active EO sensors started with the use of the first laser to be operated (1960), the solid-state ruby laser. These “diode lasers” are by far the most widely used form of semiconductor lasers, and have led to major advances in source technology for active EO sensors. While the lasers can be made to operate by optical pumping, if the semiconductor material can be fabricated in the form of an appropriate p-doped, n-doped (PN) junction, it is possible to pass electrical current through the junction and generate laser output directly. Solid-state lasers in turn are divided into two broad categories, bulk or fiber, with the latter having recently emerged as an important technology for generation of high average powers with high beam quality, as discussed below.Įven though they are also made from solid-state materials, semiconductor lasers are considered to be a separate laser category. Energy to excite the levels is provided by other sources of light, either conventional sources such as arc lamps or other lasers, a process called optical pumping. Solid-state lasers employ insulating solids (crystals, ceramics, or glasses) with elements added (dopants) that provide the energy levels needed for laser action. Solid materials are further categorized by their electrical characteristics. Lasers are typically categorized by the type and format of the medium used to generate their output, which at the highest level are gases, liquids, and solids. The sources can be based either on lasers or on nonlinear optical systems driven by lasers. This chapter discusses the variety of components currently used and some of the key technologies being developed for future systems.Īctive EO sensors employ coherent sources in the wavelength region from the long-wavelength infrared (around 10 µm) to the atmospheric transmission limit for UV light, around 200 nm. An important factor in the last ten years’ progress has been technological advances in each of the components of the active EO system: improved lasers, detectors, software, advances in robotics, and improved manufacturing technologies. For example, no particular laser or detector technology meets all the requirements of the various active EO sensing approaches. The specific requirements, complexity and sophistication of the components vary with the manner of implementation of the active EO sensing system and the usable information it is trying to extract. Other components may be required as well, depending on the implementation. All require components such as lasers, detectors, optics, and processing techniques to generate photons, bounce them off targets, and transform detected photons into usable information. Active Electro-Optical Component TechnologiesĪs has been described in Chapters 2 and 3, current and emerging active electro-optical (EO) sensing systems are implemented in many different modalities.
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