Fabry−Peŕot interference has been employed in optical fibers, sensors, electron optics, and so on. The photoluminescence (PL) spectra of a gallium nitride (GaN)-based light-emitting diode (LED), which were irradiated using various femtosecond (fs)-laser fluences, were studied. Notably, the interesting oscillation of PL was observed on the LED under irradiation with specific fs-laser fluence. The PL oscillation spectra were well fitted by the product of modulation and unperturbed luminescence. This may be attributed to surface cylinder-like nanostructures. The decrease of PL intensity was caused by the defect created through fs-laser irradiation. In addition, the film thickness and the refractive index could be calculated based on the data extracted from the PL oscillation spectra. Our report demonstrated that the optical properties of a GaNbased LED were engineered based on the surface morphology and modulated by Fabry−Peŕot interference.

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