Ultra-High Performance All-Silicon TM Polarizer Covering O-U Optical Communication Bands

Polarizers are the essential components to purify the polarization in the system demanding for the single polarization propagation. Polarizers with broad working bandwidth, low excess loss (EL) and large polarization extinction ratio (PER) are usually preferred. TE polarizers with ultrahigh performance have been demonstrated. However, the bandwidth of the previously reported transverse magnetic (TM) integrated polarizers is still limited to be < ∼160 nm when the EL < 1 dB and PER > 20 dB are simultaneously satisfied. In this paper, an all-silicon integrated TM polarizer with > 415 nm working bandwidth from 1260 nm to 1675 nm is experimentally demonstrated. The device consists of a double slot structure with 180° Euler bending on silicon waveguides. The effective refractive index (ERI) for TE polarization in the double slot structure is lower than that of the silica buffer/cladding while ERI for TM polarization is much larger than that of the silica buffer/cladding. Thus, TE polarization will leak into the substrate while TM polarization can propagate through the device with low loss. The measured transmission spectra for the fabricated polarizer show low EL < 0.9 dB and large PER > 25 dB over an ultrabroad band beyond the O-, E-, S-, C-, L-and U- bands.