An optical amplifier is a device which receives some input optical signal and generates an output optical signal with higher power without the conversion to an electrical signal during the intermediate stages. The amplification process takes place in a so-called gain medium. Most optical amplifiers are laser amplifiers. Their gain media are either insulators doped with some laser-active ions or semiconductors. The amplification process in such amplifiers is based on stimulated emission. Moreover, various types of optical non-linearities can be used for optical amplification in addition to stimulated emission. This book presents leading edge research on optical amplifiers from researchers spanning the globe.

In the recent decades, laser cooling or optical refrigeration-a physical process by which a system loses its thermal energy as a result of interaction with laser light-has garnered a great deal of scientific interest due to the importance of its applications. Optical solid-state coolers are one such application. They are free from liquids as well as moving parts that generate vibrations and introduce noise to sensors and other devices. They are based on reliable laser diode pump systems. Laser cooling can also be used to mitigate heat generation in high-power lasers. This book compiles and details cutting-edge research in laser cooling done by various scientific teams all over the world that are currently revolutionizing optical refrigerating technology. It includes recent results on laser cooling by redistribution of radiation in dense gas mixtures, three conceptually different approaches to laser cooling of solids such as cooling with anti-Stokes fluorescence, Brillouin cooling, and Raman cooling. It also discusses crystal growth and glass production for laser cooling applications. This book will appeal to anyone involved in laser physics, solid-state physics, low-temperature physics or cryogenics, materials research, development of temperature sensors, or infrared detectors.