Graphene Based Materials for Non-Linear Optical Applications and Ultrafast Laser Applications at 2 Microns

A.A. Murray, W. Blau
Trinity College Dublin, IE

Keywords: two microns, ultrafast, laser, optics

Summary:

Graphene, prepared via liquid phase exfoliation in N-Methyl-2-pyrrolidone (NMP), was investigated for potential non-linear optical uses and in particular use as a passive mode-locker for ultrafast lasers operating at 2 microns. Graphene is a prime candidate for several reasons, including its intrinsic broadband operation capabilities due to the gapless linear dispersion of Dirac electrons. Non-linear saturable absorption is required for materials used as a mode locker in lasers to obtain light pulses of very short duration, in the order of femtoseconds. Nonlinear optical properties are routinely examined using the so-called z-scan method. This set up consists of a thin sample being moved through the focus of a laser beam to vary the light intensity on the sample. This allows for measurement of the non-linear index Kerr nonlinearity with the “closed” aperture method, and the non-linear absorption coefficient via the “open” aperture method. It can also act as a reliable indicator for mode-locking ability. From the z-scan results, the potential of passive mode-locking at a wavelength of 2 microns appears to be very promising.