A theoretical and experimental analysis of modulated laser fields and power spectra

A general theory for derivation of the intensity modulation (IM) and frequency modulation (FM) function for an injection laser field is presented, with attention given to sinusoidal, sawtooth, and square wave modulation. The power spectra for a current modulated single-mode laser is derived, noting the necessity of knowing the modulus and the phase of the current-to-frequency modulation transfer function of the laser used. The various waveforms are considered in terms of broadband and narrow band FM situations with varying amounts of IM. The IM is found to make the FM spectrum asymmetrical with an alteration of the relative sideband level. Experimental confirmation of the theory is demonstrated with results of Fabry-Perot interferometric measurements in the low and high frequency regions performed on a temperature stabilized coder sequential pulse laser emitting at 832 nm.