Thanks for your reply. Actually, the taper i designed is nanotaper. One end has extremely small width and another end has a waveguide width. My goal is to do edge coupling from fiber to the smaller end of the taper. I used gaussian sourceĀ  to create mode profile coming out of the the fiber tip. With gaussian source my efficiency is extremely low. With mode source transmission efficiency is around 80%. So please guide correctly with existing examples for taper design