GaInAsP Microdisk Injection Laser with Benzocyclobutene Polymer Cladding and Its Athermal Effect

Abstract

We fabricated a GaInAsP microdisk laser using a benzocyclobutene (BCB) polymer cladding, which decreased the fragility and the thermal resistance of the conventional air cladding device and simplified the current injection using the metal pad electrode. The threshold current for a 7-µm-diameter device was 0.4 mA at room temperature, which was almost the same as that for the air cladding device. The red shift of the resonant spectrum against the continuous wave current was reduced by 54% in the BCB cladding device. Nearly 90% of this reduction is attributed to the reduction in thermal resistance. The remaining 10% is due to the reduction in temperature dependence (athermal effect) by the BCB cladding which has a negative temperature dependence of the refractive index. An analysis shows that the microdisk laser with a polymer cladding can function as an athermal laser when the disk thickness is reduced to 50–80 nm.