Ultracompact transverse magnetic mode-pass filter based on one-dimensional photonic crystals with subwavelength structures

We propose and experimentally demonstrate an ultracompact transverse magnetic (TM) mode pass filter based on a rectangularly-shaped one-dimensional (1-D) photonic crystal silicon waveguide with an extremely high polarization extinction ratio (PER) of >30 dB and a low insertion loss (IL) of ~1 dB. The device structure of the TM mode-pass filter is numerically simulated using a three-dimensional (3-D) finite difference time domain (FDTD) method. The proposed device supports its fundamental TM mode only, whereas the transverse electric (TE) mode is reflected by the 1-D photonic crystals (PhCs). The measured PER of the fabricated TM mode-pass filter is ~34 dB, and the IL is about 1 dB. The entire device length is about 4 μm. Our simulation results predict that the device bandwidth of 30 dB PER is about 200 nm.