A raman cell comprising an enclosed cell containing a raman medium with an axicon being located on the cell's optical axis at each end of the cell, one axicon having an input window for a laser pump beam and a second axicon at the cell's other end being provided with an output coupler for raman radiation, each axicon being shaped to direct energy from the laser pump beam towards an extended line focus along said optical axis, the extended line focus for each axicon being substantially collinear with each other forming an extended raman gain region.