Squeeze effect and coherent coupling behaviour in photonic crystal vertical-cavity surface-emitting lasers

The impact of air holes on the field profile in photonic crystal vertical-cavity surface-emitting lasers (PC-VCSELs) is investigated theoretically and experimentally. The three-dimensional finite-difference time-domain method is used to demonstrate the squeeze effect induced by air holes on the field profile at small etching depths and the diffraction caused by air holes in PC-VCSELs. In far field patterns (FFPs) of single-mode PC-VCSELs, there are six sidelobes surrounding the main lobe due to the coherent coupling between the diffractive light from air holes and the light from the central defect. In the experiments, the light from air holes has the same spectrum as that from the central defect. The measured FFPs are the same as the calculated FFPs. Both the measured spectra and the measured FFPs show that the light from air holes has the same wavelength and polarization as the light from the central defect, which confirms that the light from air holes is the diffractive light caused by air holes.