Diode-Pumped Femtosecond Alexandrite Oscillators and Towards Regenerative Amplification

Ultrafast lasers in the 700–800 nm wavelength range with sub-100 femtosecond pulse duration are desired for applications such as micromachining [1], pump-probe experiments [2], and multiphoton microscopy [3]. Due to the low quantum defect of red diode-pumped alexandrite lasers, high efficiency with minimal thermal impact is achieved. The availability of high-power diodes and the excellent thermo-mechanical properties of alexandrite have enabled power scaling up to >26 W in CW, thus exceeding the output power of Ti:sapphire lasers [4]. We have developed the first SESAM modelocked alexandrite laser pumped by red diodes and achieved the shortest pulse duration from a Kerr-Lens modelocked alexandrite laser with nJ pulse energy. The SESAM modelocked laser emits near-transform-limited 95 fs pulses with a pulse energy of 3.8 nJ at 84 MHz pulse repetition. The Kerr-Lens modelocked laser emits 44 fs pulses with 1.1 nJ pulse energy at 100 MHz pulse repetition rate. Figures 1 & 2 show the spectrum and intensity autocorrelation of the SESAM and Kerr-Lens modelocked lasers, respectively. [5]