Red diode-pumped SESAM and Kerr-Lens modelocked femtosecond alexandrite lasers

We report the first red diode-pumped SESAM modelocked alexandrite laser with sufficiently high pulse energy for various applications, including multiphoton imaging. We developed a SESAM-modelocked oscillator with chirped mirror dispersion compensation, generating near transform-limited pulses with 97 fs duration and a pulse energy of 3.8 nJ at 84 MHz pulse repetition rate. The laser emitted at 747 nm with a spectral width of 6.1 nm FWHM and excellent beam quality (M2<1.1). An average power of 315 mW was achieved using 1% output-coupling and 5.3 W of pump power from a fiber-coupled diode laser module with 105 µm core diameter and 0.22 numerical aperture emitting at 635 nm.