## 3 Results
### Single Soliton Case. The Cavity Soliton  
To start with, in the analysis, we are going to focus on the simplest result obtained--the single soliton. The existence of CS in semiconductor microcavities has been predicted theoretically [18] and experimentally achieved in VCSEL's below lasing threshold and proposed as pixels in all-optical systems [19]. Our case of study corresponds to those solitons formed in a cavity (CS) with a frequency-selective feedback term obtained from a VBG as is described in the second section. It is important to note that although it is possible for localized states to exist at any position of a homogeneous device, a strong pinning at preferred locations--traps--is found [20]. This effect is depicted in Figure 2; the complex cluster that appears for the highest value of the current evolves to the single soliton when the current decreases, but this behavior is restricted to a specific area on the VCSEL's surface. The intensity distribution of the single-peaked spots is reasonably Gaussian, with sizes ranging from 4.8 \(\upmu\)m to 5.8 \(\upmu\)m radius at \(1/e^{2}\) point of intensity, as can be seen in the left column of Figure 3.  
Figure 3: The left column depicts the intensity profile and dimensions of the single soliton. The right column accounts for the shape of the ring distribution; in this case, the distance between peaks is about ten microns. The intensity pattern resembles the shape of an optical vortex, including the phase singularity at the center. In this situation, two possible directions for the polarization are found, mutually orthogonal. Both orientations are homogeneous across all the soliton area, therefore we can assign just a single value to represent it, as is shown in Figure 4.  
The aforementioned states are connected by a switch when the injection current makes a cycle for a particular range of values. The change between orthogonal polarization orientations in a VCSEL is a well-known topic [21]. In our work, this effect appears for the first time between CS through a hysteresis region, as can be seen in the right part of Figure 5, where this effect is analyzed for three different linear polarizer orientations. Another important element in this part of our experiment is the measurement of the frequency for both orientations. These data are taken out of the cavity by the BS and clearly exhibit the existence of two different modes, each one corresponding to the two polarizations observed, as is shown in the left part of Figure 5.  
The amount of circular light in the emission is also studied by the analysis of the S3 parameter; in all the cases measured, this quantity represents about one-tenth of the total emitted intensity. The origin of this component is explained in the framework of the spin-flip model [22] in recent experiments for VCSELs [14]. For the polarization case investigated here, a theoretical treatment is currently under development in our group. Also remarkable is the association between the linear polarization and the circular component, i.e., the circular component changes its sense of rotation when the linear  
Figure 4: Results obtained for the single soliton showing the existence of two orthogonal directions clearly represented by streamlines with constant orientation. Figure 5: Results obtained for the frequency spectrum (**left**), and the I-L diagram for a cycle centered in the zone where the change in the soliton polarization orientation happens (**right**) using a linear polarizer with different orientations as the analyzer. component flips, giving a complete vectorial character to both polarization states. This fact could be utilized in the aforementioned all-optical systems [19] to improve their performance by the use of the complete set of Stokes values as parameters in the information processing. In order to verify the accuracy of our results, the FP factor is measured for both polarization orthogonal states.