MEMS-based wavelength and orbital angular momentum demultiplexer for on-chip applications

We demonstrate a new tunable MEMS-based WDM&OAM Fabry-Perot filter for simultaneous wavelength (WDM) and Orbital Angular Momentum (OAM) (de)multiplexing. The WDM&OAM filter is suitable for dense on-chip integration and dedicated for the next generation of optical interconnects utilizing all three degrees of freedom of the electromagnetic waves: wavelength, polarization, and OAM. The WDM&OAM filter consists of two Distributed Bragg Reflectors (DBRs), (see Fig. 1a, b): a bottom one fixed to the substrate and a movable top MEMS DBR. An applied tuning current, changing the resonator length, extends the top DBR and hence selects the central filter wavelength. A spiral phase mask on the top switches the OAM order by ±1, ±2, etc. For a detailed description of the structure and fabrication of the device, please refer to [1, 2]. The MEMS filter shows a full-width at half-maximum (FWHM) bandwidth of about 0.2 nm and a free spectral range (FSR) of about 126 nm. The phase mask provides sufficient OAM state purity in a 35 nm window around 1550 nm, covering well the whole C-band.