Supplies readers with the basic knowledge and guidance for the application of new lasers and light-emitting devices. The first part of the book discusses the generation of sub-shot-noise light in macroscopic pn junction light emitting devices, the second part is on the application of squeezed light in high-precision measurement, the third part concerns the Coulomb blockade effect in a mesoscopic pn junction and generation of single photon states, and the last part is on the detection of single photons using a visible light photon counter.