Analysis of band-gap and photoluminescence performance of low-symmetry InGaAsP photonic crystal

In two-dimensional photonic crystals, the photonic bandgap can modulate electromagnetic waves with corresponding wavelengths. Photonic crystal surface-emitting laser (PCSEL) realizes the vertical emission of laser beam through the inplane resonance and optical feedback, and significantly overcomes typical problems of the traditional semiconductor laser, such as large divergence angle, elliptical beam and susceptibility to higher-order modes. Therefore, by designing the lattice structure and materials of photonic crystal appropriately, the photonic bandgap in different polarization states can be regulated to produce high performance laser beams. Therefore, to obtain a deeper understanding of the impact of photonic crystal structure on the output properties, we demonstrate that by simulating the energy band structure near the Γ2 point, mode B has a wavelength closer to the emission wavelength. Subsequently, we analyze the influence of lattice structure, number of air holes and symmetry degree on the photon energy band distribution of TE mode. At last, two types of lattice structures with different symmetry degrees, i.e., rhombic lattice and bullet-like lattice, respectively, were prepared using electron beam lithography. The full widths at half maximum (FWHMs) of photoluminescence spectra of these two photonic crystals were detected to be 73 nm and 53 nm, respectively, which verified that the reducing lattice symmetry is beneficial for decreasing the FWHM. In addition, the symmetry reduction is favorable to eliminate the photon energy band degeneracy, leading to a blueshift in wavelength. Our research provides theoretical design insights for achieving high-performance PCSEL lasers.