The fundamental quasi-TE and quasi-TM modes of a sub-wavelength strip silicon waveguide are not purely TE or TM as the plane waves in free space. We investigate theoretically and experimentally the far-field polarization compositions of the two waveguide modes after they emanate from the waveguide facet. The measured polarization extinction ratios (PERs) of 31 dB for the quasi-TM mode and 26 dB for quasi-TE mode using free-space polarizers are consistent with our numerical analysis. Moreover, our far-field simulations show that the free-space measurement of PERs is influenced, and in many cases limited, by the sizes of various apertures in the experimental setup. This suggests a potential trade-off between achievable PERs and overall power detection/collection efficiency.
© 2013 Optical Society of America
Original Manuscript: September 16, 2013
Manuscript Accepted: October 2, 2013
Published: November 12, 2013
Jian Wang, Justin C. Wirth, Yi Xuan, Daniel E. Leaird, Andrew M. Weiner, and Minghao Qi, "Far-field polarization characterization of the fundamental modes of a strip silicon waveguide," Opt. Lett. 38, 4785-4788 (2013)