The Abdus Salam International Centre for Theoretical Physics Development of Mode-locked Femtosecond Erbium Doped Fiber Laser and Its Second Harmonic Generation

An Erbium doped fiber laser oscillator emitting at 1560nm is developed. The laser is mode-locked with saturable absorber based on nonlinear polarization rotation. The measured cw threshold power is about 70mW and the power scaling efficiency is 13%. The maximum output power obtained is 40mW. The mode-locking is self starting and the stability is verified in millisecond, microsecond and nanosecond time scale of an analogue oscilloscope. The repetition rate is measured to be 80MHz. The pulse spectra have the characteristic side lobes of soliton mode-locking with a central lobe of width19nm. The temporal width of the pulse is measured by SHG intensity autocorrelation. The pulse width depends on the pump power. The width is about 130fs for the pump current of 800mA. The mode-locked pulse is not bandwidth limited, as is evident from the time bandwidth product. Extra-cavity second harmonic is generated in a BIBO crystal with efficiency of 1%. The intra-cavity second harmonic could not be generated as the SHG crystal disturbs mode-locking because of its birefringence properly. MIRAMARE – TRIESTE August 2009 Regular Associate of ICTP. Corresponding author: [email protected]; [email protected]