Three-dimensional waveguides fabricated in poly(methyl methacrylate) by a femtosecond laser

Three-dimensional waveguides are fabricated in poly(methyl methacrylate) (PMMA) by use of femtosecond pulses from a Ti: sapphire amplifier. Waveguides can be fabricated at depths of similar to 1 nun inside a bulk PMMA, demonstrating the capability of micromachining in three-dimension. The realization of three-dimensional directional couplers is demonstrated. Observations of time-lapse cross-sectional images show the distribution of refractive index change gradually vary after irradiation of laser pulses. After the fabrication of the waveguide, refractive index in central region of the waveguide decreased. After 20 min, the symmetrical waveguide with positive refractive index change was formed.