Wideband Subwavelength Deeply Etched Multilayer Silicon Mirrors for Tunable Optical Filters and SS-OCT Applications

In this paper, we report subwavelength deeply etched 1000-nm-thick silicon layers using deep etching on an SOI substrate. The subwavelength silicon layers are used to construct wideband multilayer Bragg mirrors showing more than 220-nm 3-dB bandwidth. The mirror reflectivity and effect of silicon layers etching errors are estimated using optical measurements. The deeply etched mirrors are used to realize a 125-nm-tuning range Fabry-Perot tunable with a free spectral range of 130 nm enabled by the MEMS technology. The filter has input/output fibers inserted into micromachined grooves with in-plane axis aligned with the filter mirrors. The filter is utilized in a ring laser swept source configuration with a semiconductor optical amplifier. The swept source has 100-nm tuning range and 0.13-nm 3-dB linewidth.