Harmonic Content and Relaxation Resonant Frequency of a Modulated Laser Diode


1 Department of Electrical Engineering,Sharif University of Technology

2 Department of Electrical & Computer Engineering,Georgia Institute of Technology

3 School of Electrical and Computer Engineering,Georgia Institute of Technology


In this paper, an analysis of the harmonic contents of the optical output power for an
in-plane single mode laser diode is performed, and the results are described in detail. In the rst step, the
absolute value of power for each harmonic is obtained in terms of various laser diode parameters, and the
variations of external parameters, such as modulation current, bias current and frequency, are discussed.
The analysis is done by direct solution of the rate equations of an arbitrary laser diode for carrier and
photon densities. It is known that the optical power has a nonlinear dependence on frequency, and the
maximum optical power of each harmonic is attained in its resonance frequency. The resonant frequency is
shown to be tunable by the bias current; thus we obtain exact expressions for the output power of various
harmonics, allowing better optimization to gain improved results. We extend the approach to higher
harmonics, and numerically calculate the Total Harmonic Distortion (THD) versus major parameters,
such as frequency, bias current and modulation current. Furthermore, we nd optimal operation points
in which the desired characteristics of the laser diode can be achieved. It is also possible for the sequence
for every arbitrary single-mode laser structure to be developed by the approach presented in this work.