title: Hollow Gaussian beam generation through nonlinear interaction of photons with orbital angular momentum.
abstract: Hollow Gaussian beams (HGB) are a special class of doughnut shaped beams that do not carry orbital angular momentum (OAM). Such beams have a wide range of applications in many fields including atomic optics, bio-photonics, atmospheric science, and plasma physics. Till date, these beams have been generated using linear optical elements. Here, we show a new way of generating HGBs by three-wave mixing in a nonlinear crystal. Based on nonlinear interaction of photons having OAM and conservation of OAM in nonlinear processes, we experimentally generated ultrafast HGBs of order as high as 6 and power >180 mW at 355 nm. This generic concept can be extended to any wavelength, timescales (continuous-wave and ultrafast) and any orders. We show that the removal of azimuthal phase of vortices does not produce Gaussian beam. We also propose a new and only method to characterize the order of the HGBs.
authors: Photonic Sciences Lab., Physical Research Laboratory, Ahmedabad 380009, Gujarat, India.|Indian Institute of Technology-Gandhinagar, Ahmedabad 382424, Gujarat, India.
authors: N Apurv
authors: NA
authors: Chaitanya
authors: Photonic Sciences Lab., Physical Research Laboratory, Ahmedabad 380009, Gujarat, India.
authors: M V
authors: MV
authors: Jabir
authors: Photonic Sciences Lab., Physical Research Laboratory, Ahmedabad 380009, Gujarat, India.
authors: J
authors: J
authors: Banerji
authors: Photonic Sciences Lab., Physical Research Laboratory, Ahmedabad 380009, Gujarat, India.
authors: G K
authors: GK
authors: Samanta