Femtosecond laser comb driven perpendicular standing spin waves

We study femtosecond laser comb driven sustained and coherent spin wave (SW) generation in permalloy (Py) films over a thickness range of $d=$ 40–100 nm. A simple rapid demagnetization model describes the dependence of the observed SW intensity on laser power for all film thicknesses. In the thicker films we observe laser comb excited perpendicular standing spin waves up to third order and to 18 multiples of the 1 GHz laser repetition rate. Our results demonstrate the versatility of femtosecond combs as contact-less SW point sources over a wide range of film thickness and type of SW modes.