Abstract

High-repetition-rate Cr⁴⁺:YAG femtosecond lasers operating at nearly 1.5 μm have potential applications in optical communications. So far, repetition rates of 1.2 and 2.6 GHz have been achieved with three- and two-element cavities, respectively.^1–3 A repetition rate of 10 GHz has been demonstrated with a microchip structure although it showed Q-switched mode locking.⁴ While lasers operating at a 1.2-GHz repetition rate generate a stable and sufficiently short pulse (width of 55 fs), those operating at 2.6 GHz generate a rather unstable and insufficiently short pulse (width of 115 fs), and a cw component is often included. This is because the two-element cavitie generating a 2.6-GHz repetition rate is not well optimized. Because a three-element cavity has many adjustable parts, it can be optimized experimentally even if the design is not complete. However, a two-element cavity is difficult to optimize by experiment if the design is not complete because it has only a few adjustable parts. To obtain an optimized cavity operating at a 2.6-GHz repetition rate, we must determine the best cavity parameters. In this study, we experimentally find these parameters using a three-element cavity.

© 2002 Optical Society of America