Study of whispering-gallery mode of InGaP microdisks by using scanning near-field optical microscopy

Microcavity shows the growing importance of the intensity enhancement, inhibition and spectral narrowing of spontaneous emission. The advantages of microcavity lasers are the very low threshold and small size. We have fabricated InGaP microdisks with radius of about 5 mu m. The photoluminescence of our InGaP microdisks in far-field and near-field observation are compared. A strong enhancement of the photoluminescence intensity in the microdisks with respect to that of the un-patterned sample of the same epitaxial wafer is obtained. Far-field fluorescence imaging shows a bright red emission of fluorescence around the circumference of the microdisk. Simultaneous acquisition of near-field image and topography gives the correlation of the sample surface and light distribution. The optical disk mode pattern in our InGaP microdisks can be interpreted as whispering-gallery mode and the mixture of other modes.