Higher order mode propagation in ultrathin optical fibers for atom traps

We have demonstrated efficient propagation of the first excited TE01, TM01, and HE21 modes in a nanofiber with a radius of 400 nm. As we decrease the taper angle from 4 mrad to 1 mrad, the propagation becomes more adiabatic and the transmission improves from 20% to 85%. We have also demonstrated that the choice of drawn fiber can have a significant impact on the propagation characteristics.