Diode-Pumped Gigahertz Repetition Rate Femtosecond Cr:Lisaf Laser Citation

We report a low-cost, 1 GHz repetition-rate, diode-pumped, saturable Bragg reflectors modelocked Cr:LiSAF laser, which generates nearly transform-limited 103-fs long pulses around 866 nm, with a record high peak power of 1.45 kW. 2010 Optical Society of America OCIS codes: (140.3460) Lasers; (140.3480) Lasers, diode pumped; (140.4050) Mode-locked lasers High repetition-rate femtosecond (fs) laser pulses are important in many applications such as optical frequency combs generation [1], low noise microwave source development [2], and high-speed optical sampling [3]. Presently, most of them rely on Ti:Sapphire technology to obtain high peak-power, femtosecond laser pulses with repetition rates in the 1-10 GHz range. Higher repetition rates up to 100 GHz have been recently demonstrated with diodepumped fundamentally mode-locked Er:Yb:glass lasers [4]. However, most high repetition-rate lasers of this kind can only produce pulses in the picosecond regime with peak powers limited to several watts. In addition, a major drawback of the femtosecond Ti:Sapphire technology is the requirement for frequency-doubled neodymium pump lasers which make the overall system bulky and expensive. In contrast, Cr:Colquiriite gain media such as Cr:LiSAF offer the possibility of direct diode pumping, combined with a broad emission band that can support down to 10-fs pulses [5]. Direct diode pumping facilitates the construction of highly-efficient, compact and low-cost laser systems [5]. Moreover, Cr:Colquiriites can be passively mode-locked with saturable Bragg reflectors (SBR) [6] (also known as semiconductor saturable absorber mirrors (SESAM) [7]), enabling self-starting and robust mode-locked operation. A GHz repetition-rate femtosecond Cr:LiSAF laser was first reported in [8], but had low peak power (∼20 W), due to the limited availability of efficient red laser diodes at that time, and limitations in SBR/SESAM design. In this paper, we present a low-cost, single-mode diode pumped, SBR/SESAM mode-locked, Cr:LiSAF laser at 1 GHz repetition rate. In continuous-wave (cw) mode-locked operation, nearly transform-limited 103-fs long pulses, with 170 pJ of pulse energy and 1.45 kW peak power are obtained around 866 nm. This represents a factor of ∼70 increase in attainable peak powers from GHz Cr:Colquiriite lasers [8].