Date of Award
Doctor of Philosophy
Electrical and Computer Engineering
The goal of this research was to study the polarization effect on the achievability of mode locked laser signal in accordance to polarization dependency. Polarization characterization was studied in prior to mode locking to determine semiconductor optical amplifiers (SOA) polarization dependency. It was found that per SOA manufacturer a variation of dependency was recognized. Two setups were suggested based on dissipative soliton resonance (DSR) schemes, the external DSR with regenerative feedback and the total internal reflection (TIR) DSR. The laser operated at 1530nm for multiple SOA manufacturers and was capable of generating ultrashort pulses with different durations as listed in Table (3.2.3) and Table (3.3.2). For the external mode-lock, the maximum achieved average output power of 3.40mW corresponding to ~77.15fJ of output pulse energy through continuous pumping by gain modulation of an SOA used as the active medium. While the TIR mode-lock the maximum achieved average output power for mode-locked signal of 5.25mW corresponding to ~23.73fJ of output pulse energy.It was concluded that the output pulse of the external DSR setup showed polarization dependency for two SOAs A and C and provided mode locked signals with pulse width ranging between 1200ps and 1000ps with repetition rate approximately of 35MHz and 101MHz respectively. The TIR DSR had a variation in results also to be polarization related. While SOA D did not provide mode-locked signal output. The least polarization dependent SOAs E and X did not provide distinctive stable mode-locked signal. While increased sensitivity towards polarization however resulted in stronger mode locked signal for SOAs A and C with FWHM between 200ps and 350ps and a repetition rate of approximately 20MHz. For future work, it is recommended to adjust the setup length in addition to fine tuning polarizer and filters to improve pulse stability and eliminate the noise effect.
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