Significant photoinduced Kerr rotation achieved in semiconductor microcavities

Giant Kerr rotation and ellipticity are observed and investigated in an asymmetric planar microcavity with a quantum well in the active region. Rotation angle of the polarization plane as well as ellipticity were determined from time- and frequency-resolved measurements of the Stokes vector components of reflected light. It was found that in a small range of the cavity mode detunings the polarized pump pulse creates a large splitting of the lower polariton branch while leaving its linewidth almost the same. This fact gives a possibility to observe at such detunings the Kerr rotation angle and ellipticity, close to their extremes. A theoretical analysis shows that the decisive role in reaching extreme polarization rotation angles is played by the structure asymmetry. Comprehensive analysis of the polarization state of the light in this regime shows that both renormalization of the exciton energy and the saturation of the excitonic resonance contribute to the observed optical nonlinearities.

Figure 1

Reflection spectrum of the structure as a function of position in the structure plane.

Figure 2

(a)–(f) Kinetics of the reflection spectra in six polarization of detection: vertical, diagonal, right circular, horizontal, antidiagonal, and left circular. Cavity detuning $\mathrm{\Delta }=-3$ meV, absorbed pump power 1 mW. (g) and (h) Kerr rotation angle $\phi$ and ellipticity angle $\mathrm{\Theta }$ calculated from (a)–(f) as a function of detection energy and pump-probe delay.

Figure 3

Reflectivity spectra of the probe for different detection polarizations. Cavity detuning $\mathrm{\Delta }=-3$ meV, ${\sigma }^{+}$-polarized pump power is $P\simeq 1$ mW. Spectra taken at $-100$ ps pump-probe delay (unperturbed system, green symbols) are compared with the photoinduced spectra measured at 10 ps pump-probe delay (orange symbols). Lines show the results of the modeling.

Figure 4

(a) Projection of the reflected probe Stocks vector spectrum on the equatorial plane of a Poincare sphere. Orange circles: $\mathrm{\Delta }=-5$ meV, $P=0.4$ mW, green triangles: $\mathrm{\Delta }=-3$ meV, $P=1$ mW. Lines : modeling. Energy range is the same as in Fig. 3. (b) The same in the vertical plane of the Poincare sphere (ellipticity angle). (c) Maximum rotation angle as a function of pump power for $\mathrm{\Delta }=-5$ meV and $\mathrm{\Delta }=-3$ meV. Symbols show the experimental data, dashed lines show modeling taking into account inhomogeneous broadening of the cavity mode, and dotted lines stand for the model without inhomogeneous broadening. (d) Calculated function $r\left(\omega \right)$ on the complex plane for co- (dashed line) and cross- (solid line) circular polarizations of detection for $\mathrm{\Delta }=-5$ meV (orange), $-3$ meV (green), and 0 meV (blue). The angle between two arrows indicates the maximum Kerr rotation angle at each detuning.

Figure 5

Photoinduced energy shifts of the upper and lower polariton branches in co- (black crosses) and cross- (red squares) circular polarization of detection. (a) and (c) $\mathrm{\Delta }=-5$ meV. (b) and (d) $\mathrm{\Delta }=-3$ meV. Lines are the corresponding energy shifts obtained by the fit.