Semiconductor Optical Amplifiers

Semiconductor optical amplifiers (booster optical amplifiers) are amplifiers which use a semiconductor to provide the gain medium. They have a similar structure to Fabry–Perot laser diodes but with anti-reflection design elements at the end faces. Recent designs include anti-reflective coatings and tilted waveguide and window regions which can reduce end face reflection to less than 0.001%. Since this creates a loss of power from the cavity which is greater than the gain, it prevents the amplifier from acting as a laser.

Optical coherence tomography (OCT) is a low coherence interferometry technique that generates backscattering profiles of tissue. OCT has been very successful in ophthalmology in diagnosing eye diseases and it is widely applied in other areas such as dentistry, endoscopy and dermatology. Light sources are a crucial component in the design of OCT systems as they decide the resolution along the optical axis as well the depth penetration of infrared light in tissue. Swept-source lasers (SSL) are the light source of choice for Fourier domain optical coherence tomography (FDOCT). The gain medium in SSL is most often a semiconductor optical amplifier (SOA). Their main advantage is fast carrier dynamics which ensures fast buildup of lasing within the cavity. Furthermore, a wider tuning range can be achieved by employing several SOAs in parallel.