Efficient broadband emission from condensed media irradiated by low-intensity, unfocused, ultrashort laser light

We report here measurements of the efficiencies of broadband emission in different optical media using an unfocused, ultrashort (~40 fs) laser beam. Two different measurements have been carried out by placing a wire mesh in the path of the incident laser radiation. The wire mesh introduces a periodic intensity distribution in the x-y plane and also in the direction of the laser beam propagation. We measure both on-axis and offaxis components of the broadband emission and also observe modulation in broadband generation as the distance between the mesh and the sample is varied. The experimentally measured locations of broadband emission maxima are in agreement with simulations based on Fresnel diffraction integrals. The off-axis emission efficiencies lie in the range of 16-87%.