A low-loss hybrid plasmonic transverse magnetic (TM)-pass polarizer has been demonstrated utilizing polarization-dependent mode conversion. Taking advantage of the silicon hybrid plasmonic slot waveguide (HPSW), the unwanted transverse electric (TE) fundamental mode can be efficiently converted first to a TM higher-order mode and then suppressed by a power combiner, while the retained TM fundamental mode can pass through with negligible influence. Since the HPSW feature both strong structural asymmetry and a small interaction area in the cross-section between the metal and optical field, the optimized insertion loss of the device is as low as 0.4 dB. At the wavelength of 1550 nm, the extinction ratio is 28.3 dB with a moderate footprint of 2.38μm×10μm. For the entire C band, the average reflection of the TE mode is suppressed below ?14dB, and the extinction ratio is over 18.6 dB. This work provides another more efficient and effective approach for better on-chip polarizers.

An on-chip, high extinction ratio transverse electric (TE)-pass polarizer using a silicon hybrid plasmonic grating is proposed and experimentally demonstrated. Utilizing plasmonics to manipulate the effective index and mode distribution, the transverse magnetic mode is reflected and absorbed, while the TE mode passes through with relatively low propagation loss. For a 6-μm-long device, the measurement result shows that the extinction ratio in the wavelength range of 1.52 to 1.58 μm varies from 24 to 33.7 dB and the insertion loss is 2.8–4.9 dB. Moreover, the structure exhibits large alignment tolerance and is compatible with silicon-on-insulator fabrication technology.

The optical saturation characteristics in the germanium-on-silicon (Ge-on-Si) photodetector are studied for the first time, to the best of our knowledge. The relationship between the optical saturation characteristics and the optical field distribution in the Ge layer is illustrated by the simulation. This theory is verified by comparative experiments with single-injection and dual-injection structures. The dual-injection photodetector with a more balanced and uniform optical field distribution has a 13% higher responsivity at low optical power and 74.4% higher saturation current at 1550 nm. At higher optical power, the bandwidth of the dual-injection photodetector is five times larger than that of the single-injection photodetector.