An all-fiber beam shaping using multimode fiber

A new beam shaping technique has been developed by inverse etching the end face of a multimode fiber to form a concave cone tip. Concave tip fiber can convert a Gaussian beam profile to a flat top beam with a uniform intensity distribution. A flat top beam with intensity variation of approximately 5% and flat top diameter to spot diameter ratio of 67% has been achieved. With this technique one can also change the beam shape from a Gaussian to a donut by moving the observation plane. A flat top multimode fiber beam delivery has been tested for stimulation of prostate nerves.