ABSTRACT
Coherent light has existed virtually since 1960, when laser oscillation was demonstrated for the first time using a ruby crystal in a Fabry-Perot resonator. This innovation spurred many people to create various innovations in lasers using various media. These innovations include semiconductor lasers, which have undergone much development since the laser oscillation was achieved at room temperature using doubleheterojunction structures. These semiconductor lasers are very small and operate under low-driving power conditions and, hence, show great potential for a wide variety of applications in various fields including information, measurement, communications, etc. In this chapter, the fundamentals of such semiconductor lasers are briefly explained, and then several practical applications are described.
