This invention consists of an optical external cavity having specialized Brewster angle wedges. The external cavity apparatus utilizes several types of very high index of refraction wedges made from semiconductor and special glass materials. The apparatus limits the oscillation of the optical wavelength modes emitted by a diode laser. In addition, such cavities also simplify the motions of the moveable mirror that returns these selected laser photons to the cavity input beam path or fiber. The wedge also disperses the laser light to isolate the desired wavelength band better than the currently used grating systems. Wavelengths other than the desired wavelength band are dispersed, then reflected at angle away from the return fiber and thus not returned to the amplification cavity inside the laser. The apparatus then emits only the laser photon mode desired by the user.