Figure 1
From: Optomechanically induced gain using a trapped interacting Bose-Einstein condensate

(Color online) A Fabry-Perot cavity containing a trapped BEC is driven by a strong coupling laser along its axis from the left mirror of the cavity where a weak input signal is also entered. The system behaves as an optical transistor that can amplify the input signal in the output which emanates from the left side of the cavity.