A dual-mode variable optical power splitter using a Digital Spatial Light Modulator and a variable focus lens

Abstract

This paper describes the design of a variable optical power splitter which splits input optical signal power into variable ratios between two output ports. The proposed design is a hybrid scheme which uses a conventional Digital Spatial Light Modulator (DSLM) and a tunable focus Electrically Tunable Lens (ETL). The proposed splitter has an inherent dual-mode of operation and is capable of operating in a DSLM-only, ETL-only or a hybrid DSLM/ETL mode depending on the desired accuracy of the power split ratio. We show that the improved power splitter design can potentially offer a fine split ratio control through additional ETL focal length control. Moreover, it eliminates the need of ascertaining an exact random image pattern through hit-and-trial for an exact split ratio in a DSLM-only splitter mode. The DSLM is used to obtain the closest value to the desired split ratio using a fixed circular pattern with a variable radius while the ETL is tuned for further fine-tuning the split ratio in order to get closer to the required value. We also show that a dual-mode control delivers multiple possible solutions for any desired split ratio. Experimental results validate the working of the proposed splitter design.