As a major step forward in quantum theory and its applications, the laser, a novel light source, was invented in 1960 [1]. The use of lasers has dramatically changed optical science and technology, and it is considered to be one of the biggest scientific achievements of the 20th century, on a par with the invention of transistors. Lasers have a variety of applications because of the high controllability of their amplitude, phase, frequency, and polarization. Their industrial applications are known as photonics or optoelectronics, with examples including optical disk memory, optical fiber communication systems, and optical fabrication, including photolithography.