Reduction of nonlinear distortion in semiconductor lasers with external light injection

Abstract

It is demonstrated analytically that the static light-current characteristic of an injection-locked laser is highly linear away from threshold and is suitable for direct intensity modulation. By using a small signal perturbative approach, expressions for second order harmonic distortion and two-carrier third order intermodulation distortion are evaluated. At microwave frequencies, it is demonstrated that these distortions can be significantly reduced using injection locking. This is attributed to additional coupling effects between optical phase and photons under injection locking, in addition to the photon - electron interactions seen in free-running lasers.