Abstract

Stretched-pulse additive-pulse mode-locked (SP-APM) fiber lasers generate ultra-short pulses (100 fsec) with energies comparable to those of color-center lasers [1]. By using the APM rejection port as the output port, pulse energies of over 2 nJ have been achieved with average powers of > 90 mW [2]. Here we report that frequency-doubling of these pulses results in high conversion efficiencies and transform-limited pulses of up to 200 pJ at 775 nm. When operating the SP-APM laser to optimize the frequency-doubled power, the fundamental pulses tend to have excess energy in the pulse wings and larger time-bandwidth products than when the SP-APM laser is optimized for fundamental pulse width. In order to better characterize both the fundamental and frequency-doubled pulses, we used frequency-resolved optical gating (FROG) which allows the direct determination of the intensity and phase of an ultrashort pulse [3,4]. Results indicate that the frequency-doubled SP-APM laser is a possible, inexpensive and compact, replacement for the argon-pumped Ti:Sapphire laser as a seeding source for regenerative amplifiers.

© 1996 Optical Society of America