We describe the design and operation of a compact femtosecond Ti:Al2O3 laser based on a novel multipass cavity (MPC) design. The laser is all solid state, has prismless dispersion compensation with double-chirped mirrors, and uses a tight-focusing geometry to facilitate efficient low-threshold operation. We increase output pulse energies by extending the resonator length with a compact, scalable MPC, which preserves the characteristics of the Gaussian beam for the short cavity. Although the effective cavity length is ~5 m, an extremely compact laser that measures only 30 cm×45 cm is achieved. With only 1.5 W of pump power, the laser generates 23-fs pulses at a repetition rate of 31.25 MHz and with 88 mW of average output power, corresponding to 2.8 nJ of pulse energy.
© 2003 Optical Society of AmericaPDF Article