Characterization and mitigation of phase-modulation-dependent loss of liquid crystal on silicon

We characterize the phase-modulation-dependent loss (PMDL) arising from the commercial liquid crystal on silicon (LCOS) and find that it severely degrades the fidelity of mode-selective conversion and orbital-angular-momentum (OAM) generation, as well as the performance of LCOS-based wavelength-selective switch (WSS). For the LP₁₁ mode conversion, an offset-launch technique is proposed to mitigate such effect. For the LP_l,m (l>1) mode conversion, the superposition of OAMs with conjugation vortices is demonstrated to achieve perfect mode conversion. Experimental outcomes verify that both solutions are able to improve the fidelity quality factor by at least 15 dB.