EFFECT OF GAIN SWITCHING FREQUENCY ON ULTRASHORT-PULSE GENERATION FROM LASER-DIODES

In this work, the effects of gain switching frequency on ultrashort pu lse generation are investigated using a model based on the multi-mode rate equations. In addition to the commonly used laser diode parameter s, the key parameters corresponding to the different laser diode mater ials and structures are included in the model. Effects of some laser d iode parameters, and d.c, and RF drive conditions on the full width at half-maximum (FWHM) of gain switched pulses are investigated for the 1-15 GHz gain switching frequency range. Multi-pulse generation and th e cut-off frequency of gain switching are also determined for this fre quency range. It is found that the FWHM of pulses decrease as the RF c urrent is increased, at a constant frequency. However, the FWHM of pul ses either decrease or increase as the d.c. bias is increased, dependi ng especially on the gain compression and gain peak. As the frequency is increased, pulse widths start to decrease or increase depending on the laser diode parameters. The FWHM of pulses for shorter cavity lase rs are found to be almost insensitive to the frequency. Among the para meters affecting the multi-pulse generation and cut-off, gain compress ion, gain constant, and d.c. and RF current amplitudes are found to be the most effective. All calculations are also carried out using singl e-mode rate equations and results of multi-mode and single-mode soluti ons are compared.