Resonance-Free Fabry-Perot Cavity via Orbital Angular Momentum Ladder-Up

Altering the multiple longitudinal modes in a FabryPérot (FP) cavity to an unbounded expansion in orthogonal modal orders disrupts coherent field interference and ultimately eliminates the resonant response. In this work, we demonstrate an optical cavity which transforms an incoming broadband fundamental Gaussian mode into a superposition of numerous broadband LG modes with fixed parity, while making the cavity non-resonant and therefore preserving the spectral characteristics of the input beam. This is achieved by placing a single holographic phase mask (HPM) of the first Laguerre-Gaussian (LG) mode, which functions as an optical angular momentum (OAM) mode converter, inside the compact FP cavity. Consequently, a resonant free FP cavity was created, due to the orthogonality of the LG modes and the dynamic phase evolution.