Periodic surface structures on gallium phosphide after irradiation with 150 fs-7 ns laser pulses at 800 nm

Gallium phosphide is irradiated with 150 fs-7 ns duration laser pulses at a wavelength of 800 nm. After irradiation with 150 fs pulses, periodic surface structures (ripples) are observed on the GaP surface, exhibiting near-wavelength and substantially subwavelength spatial periods depending on irradiation conditions. As the pulse duration increases, near-wavelength ripples become a more dominant feature, completely replacing subwavelength ripples for pulse lengths beyond 80-130 ps. Overall the results show that subwavelength ripples can be generated for a wide range of pulse durations, and their formation is quite insensitive to pulse intensity.