Polarization Dependence of the Optical Modal Gain in ZnO

The modal gain spectrum due to the electron-hole plasma in ZnO was measured using a variable-stripe-length method. A modal gain contour map for energy and stripe length allowed the modal gain saturation to be analyzed in terms of the spectral and the stripe length dependences. The modal gain was observed to be more significant in the TE mode than in the TM mode due to the polarization asymmetry of the wurtzite structure. We also found that the degree of polarization are enhanced as the stripe length increased, despite of modal gain saturation.