Aiming at the problems of large waveguide loss and low optical confinement factor of long-wavelength infrared quantum cascade laser (QCL),this paper studies in detail the effects of the three-dimensional optical structure of 8.3 μm long-wavelength infrared QCL chip on the optical waveguide and the electrical performance.In the direction of epitaxial growth,the effects of material thickness,doping concentration and other factors on the optical waveguide performance of "InP+InGaAs" and "All-InP" waveguide structures are investigated and compared.The results confirm that the "All-InP" waveguide structure can achieve lower waveguide loss and mode overlap coefficient.In the direction of ridge waveguide sides,the effect of ridge width on the optical waveguide performance is investigated.It is found that the mode overlap coefficient of the chip with ridge width less than 10 μm can be reduced by using InP∶Fe buried heterostructure (BH) on both sides of the ridge.In the direction of the cavity surface film,the optimization of the mirror loss is accomplished by studying the relationship between the film thickness and reflectivity.The results show that when the thickness of the Y2O3 antireflection (AR) coating is 990 nm,the reflectivity of the antireflection and the mirror loss are 3.43% and 3.37 cm-1,respectively,and which then lead to the maximum wall plug efficiency (WPE) of 12.91%.