Tight focusing effect of annular obstructed incident beam in the focal region of high NA lens Gokulakrishnan, K. ; Suresh, P. ; Mariyal, C. ; Pillai, T. V. Sivasubramonia ; Rajesh, K. B. Abstract Publication: Optik Pub Date: September 2014 DOI: 10.1016/j.ijleo.2014.05.028 Bibcode: 2014Optik.125.4652G