The polarization degree of vertical-cavity surface-emitting lasers (VCSELs) subjected to optical feedback with rotating polarization is investigated numerically. To compare the polarization properties of two VCSELs with different frequency splitting (i.e., VCSEL1/VCSEL2 with closely/widely spaced frequency splitting), we extend the spin-flip model by taking the controllable polarization into consideration. The degrees of polarization are quantified in terms of the defined fractional polarization (FP), and the evolutions of the polarization state are further described to explain the polarization switching process through the representation on the Poincaré sphere. As the polarizer angle is varied from 0° to 90°, the polarization switching and the competition between the linearly polarized and the elliptically polarized states are observed in both VCSELs. However, the switching processes are different: in VCSEL1 the polarization varies slowly from x-polarization (XP) mode to y-polarization (YP) mode along the linearly polarized state oriented between the two modes, while the switching is much sharper and the so-called critical angle corresponding to the minimum FP is found in VCSEL2. The effects of the initial conditions, spin-flip rate, and feedback strength are also taken into account.
© 2010 Optical Society of America
Original Manuscript: September 25, 2009
Revised Manuscript: January 3, 2010
Manuscript Accepted: January 4, 2010
Published: February 17, 2010
Shuiying Xiang, Wei Pan, Lianshan Yan, Bin Luo, Ning Jiang, Kunhua Wen, Xihua Zou, and Lei Yang, "Polarization degree of vertical-cavity surface-emitting lasers subject to optical feedback with controllable polarization," J. Opt. Soc. Am. B 27, 476-483 (2010)