1ST AND 2ND HARMONICS OF THE LASER RESPONSE TO CURRENT MODULATION

The nonsteady-state generalization of the laser current-voltage and po wer characteristic model is obtained and used to derive the small-sign al systems of equations for first- and second-order laser distortion t o current modulation. The model takes into account the heating of the electron-hole gas in the active region and intrinsic leakage current a ssociated with escape, of the particles through the heterojunctions. T he intrinsic diode capacitances and general form impedance are include d in the small-signal equations. The quantitative analysis of the lase r response to the current modulation is carried out on the specific ex ample of the 1.3 mum laser based on an InGaAsP compound. A dependence of the light first and second harmonics on the thickness of the claddi ng layer (due to change of the leakage current) is demonstrated. It is shown that for thicknesses larger than several microns the influence of the leakage is negligible. It is found that modulation of the elect ron-hole gas temperature (due to heating effect) dramatically increase s the second harmonic just in the range of frequencies (<500 MHz) impo rtant for laser applications in the transmission of the analog video s ignals in cable television systems.