Design of GaN-Based PCSEL With Temperature-Insensitive Lasing Wavelength

Considering the compensation of thermo-optic coefficients (TOC) between GaN-based cavity and TiO2 photonic crystal (PhC) layer, we have theoretically designed a photonic crystal surface emitting laser (PCSEL) with temperature-insensitive wavelength. The structure includes a freestanding GaN membrane with embedded multiple InGaN/GaN quantum well (QW) layer and the top TiO2 PhC layer. The high refractive index (RI) of PhC and the freestanding membrane cavity structure cooperate to enable a stronger field-coupling in PhC, thus fulfill the athermal coupling condition. Interestingly, the wavelength temperature dependence is only 0.0015 nm/°C for such PCSEL with a 82% PhC confinement factor, and its athermal property is proportional to the field confinement factor in TiO2 PhC layer. To illustrate, a general formula has been developed after the investigations of thermo-optic effect and thermal expansion effect.