Optoelectronics embodies a broad range of scientific and technological knowledge and enables the design and application of devices with both optical and electronic inputs and outputs. Accordingly, optoelectronic devices operate in a greater variety of modes and are more functional than their purely electronic counterparts. This rich variety of operational modes has had an enormous positive influence on lightwave communication systems, on devices for light-to-electric energy conversion, and on optoelectronics-based switching and logic elements. These devices also underlie many innovations such as bar-code pricing, laser printers, laser readers, etc. Optoelectronic devices have unique abilities to monitor the amplitudes and temporal characteristics of radiation in the ultraviolet (UV), visible, and infrared (IR) regions of the electromagnetic spectrum. Moreover, optoelectronic devices are capable of producing radiation spanning the UV, visible, and IR spectra at ever-increasing power levels and with temporal characteristics that may be controlled with sub-nanosecond precision. These novel capabilities and expanded levels of functionality will continue to open many avenues for biomedical applications, thereby expanding the list of current applications such as laser surgery. In many cases, the optical properties of these devices are determined by the electronic properties of the materials used in the construction of the active components of an optoelectronic device or system. Optoelectronic devices span the range from simple devices, such as a detector of light based on the photoelectric effect discovered by Albert Einstein (1879–1955) in 1905, to modern monolithically integrated semiconductor heterostructure devices incorporating miniature lasers, photodiodes, and electronic components, such as amplifiers, all grown on the same semiconductor substrate. These devices generally function for the purpose of or by employing techniques for the processing of optical and electronic signals. The variety of optoelectronic devices has increased enormously in the last few decades because of advances in the materials science underlying the growth, fabrication, and production of components for optoelectronic devices and systems. The rich and growing diversity of optoelectronic devices is making possible continuously expanding applications of optoelectronics in biomedical engineering.