An optical pickup and an optical recording and/or reproducing apparatus employing the optical pickup, wherein the optical pickup includes: a light source (11); an objective lens (17) to collect and focus an incident beam on an information storage medium (10); a holographic grating (13) to split light emitted by the light source (11) into a main beam and first and second sub-beams by diffraction and to provide, or create, a continuously changing wavefront in the first and second sub-beams to reduce the amplitude of an AC component of a sub-push-pull (SPP) signal of the first and second sub-beams; and a photodetector (19) to receive the main beam and the first and second sub-beams that are focused on and reflected from the information storage medium (10) and to obtain a main push-pull (MPP) signal of the main beam and a SPP signal of the first and second sub-beams.