(AL,GA)SB LONG-WAVELENGTH DISTRIBUTED BRAGG REFLECTORS

We have grown and measured long-wavelength distributed Bragg reflector s by using alternating layers of the semiconductors AlSb and (Al,Ga)Sb . The large refractive index ratio available with these materials allo ws for high-reflectivity mirrors with relatively few mirror pairs. A s imple 10-period AlSb/GaSb DBR had a maximum reflectivity of over 98% a t a wavelength of 1.92 mu m. Also, a 12-period Al0.2Ga0.8Sb/AlSb DBR e xhibited reflectance greater than 99% at 1.38 mu m. These structures a re easily grown by molecular beam epitaxy and are suitable for use in surface-normal photonic devices operating at long wavelengths.