Geração e propagação de pulsos em laser a fibra dopada com Érbio com cavidades ultralongas

• Autor(a) principal: Saito, Lúcia Akemi Miyazato
• Data de Publicação: 2012
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: Biblioteca Digital de Teses e Dissertações do Mackenzie
• Texto Completo: http://dspace.mackenzie.br/handle/10899/24257
• topic: laser à fibra dopada com Érbio; cavidade ultralonga; laser em anel; acoplamento de modos ativo; propagação de pulso; efeito solitônico; rede KyaTera; Erbium fiber laser; ultralong cavity; ring laser; actively modelocking; pulse propagation; soliton effect; KyaTera network; CNPQ::ENGENHARIAS::ENGENHARIA ELETRICA

We investigated the mechanisms responsible for pulse formation and evolution in Erbium-doped fiber lasers with cavity lengths varying from 16.4 m to 100.8 km that were actively mode-locked at repetition rate of 1 GHz. The variation of pulse widths and the peak powers in these lasers defined three regimes of propagation inside the cavities and we identified the mechanisms responsible for the pulse formation and evolution in each one of these regimes depending on the ratio between the cavity length (Lcav) and the dispersion length (LD) and nonlinear length (LNL). When Lcav is shorter than LD and LNL, there is neither dispersive nor nonlinear effect during pulse evolution (pulse has a duration of approximately 30 ps). In this regime, its final duration is determined by the standard theory of active modelocking. For Lcav shorter than LD but ~ LNL, the pulse evolution is in the nonlinearity-dominant regime where the self-phase modulation leads to spectral broadening. In addition, for cavities longer than 12.6 km, Lcav ~ LD and also longer then LNL. The pulse evolution is in the dispersion-dominant regime with its duration depending on the accumulated dispersion. In this regime the soliton effect takes place and the final pulse duration depends on the cavity length. Also, we present a comparison between an in-field and in-laboratory 50 km ultralong Erbium fiber lasers actively mode-locked with repetition rate varying from 1 to 10 GHz generating pulses from 35.2 to 68.7 ps. The pulse widths generated at higher frequencies are in agreement with Kuizenga-Siegman theory. However, for lower frequencies the pulses have higher intracavity peak power which allows the soliton effect to take place. Depending on the pump power level, the repetition rate and the cavity length, both lasers can operate in active mode-locking or under the influence of the soliton regime that locks the pulse duration according to the dispersion and cavity length. Due to the soliton robustness, this condition eliminates most of the environmental influence in the in-field mode-locking regime and makes both lasers very similar.