Studies of polymer microring lasers subject to uniaxial stress

The emission spectra of microring lasers fabricated from ∏-conjugated polymer films casted on nylon microfibers with diameters in the range of 35-90 µm were studied upon application of uniaxial stress with strain up to ~12%. The laser emission spectra substantially change with the applied stress, showing enhanced sensitivity to stress over changes induced in the fiber diameter alone. This is explained as due to the induced change in the polymer refractive index spectrum upon stress, causing an unexpected increase in the refractive index dispersion and, consequently, also in the effective refraction index for lasing at emission wavelengths.