Multiple resonances in microdisk lasers of π-conjugated polymers

We have fabricated microdisk lasers from pi-conjugated polymers that show multiline emission spectrum upon optical excitation. Using Fourier transform analysis, each emission line is assigned integer to an interger Bessel function that helps to estimate the field distribution inside the photoexcited polymer microdisk. We found that the microdisk can sustain two different laser modes with different, though complementary, field distributions and that the index of refraction decreases with increasing excitation intensity. (C) 2002 American Institute of Physics.