Product Code: ICA13_N208

Development of the Variable Pulsewidth Mode-Locked Femtosecond Laser Using Coherent Coupling
Authors:
Yasuhiro Nishiyama, Kinki University; Higashiosaka Osaka Japan
Minoru Yoshida, Kinki University; Higashiosaka Osaka Japan
Hiraku Yabuno, Kinki University; Higashiosaka Osaka Japan
Presented at ICALEO 2013

Passive mode-locked pulse lasers applying erbium-doped fiber have about 100 fs pulsewidth that is near the Fourier-limited pulse. However, femtosecond pulses are often demanded for more longer pulsewidth, because high energy pulses are useful in processing. In this study we develop a continuously variable pulsewidth laser using novel method applying coherent coupling, different from conventional technology with optical band-pass filter. In our novel variable pulsewidth system, two laser cavities share single output coupler to combine emissions within the cavity. The coupled longitudinal modes are emitted by corresponding longitudinal modes of the respective laser modules. Generally, the coherent coupling technology applies corresponded initial longitudinal modes and that is used as power increasing technology. However in this study, the one longitudinal-mode-space is changed arbitrary by tuning the cavity length to restrict coupled longitudinal modes. Therefore, envelope of the longitudinal modes, i.e. spectrum bandwidth is operated to control the pulsewidth. In experiment, the laser modules of our system generate about 150 fs pulsewidth and around 30 nm spectrum bandwidth respectively. The result of the coupling, the pulsewidth is changed with the length deviation of the variable cavity tuned 950 µm and we have succeeded in widening the pulse to 1 ps at maximum.