Fig. 1. Refractive index of Al_xGaAs versus x at 940 nm wavelength

Fig. 2. Transmission matrix model of DBR multilayer dielectric film

Fig. 3. Transmission angle model of each layer in DBR structure

Fig. 4. Gradient DBR structures. (a) A pair of gradient DBR structures; (b) multilayer dissection equivalent model of Alx1-x2GaAs gradient layer

Fig. 5. Influence of different stacking methods on DBR reflectance spectrum

Fig. 6. Reflectivity versus period for DBR structure

Fig. 7. Relationship between reflection spectrum of DBR and incident angle

Fig. 8. Reflectance of DBR versus incident angle at center wavelength of 940 nm

Fig. 9. Reflectance spectra of different gradient DBR structures

Fig. 10. Maximum reflectances of DBRs under different gradient layer thicknesses