method and apparatus for laser texturing symmetrically and simultaneously both sides of a glass containing substrate , such as a magnetic disk . there are two or more acousto - optic modulators arranged in series to obtain equal laser pulses from a first beam from a laser , apparatus for capturing a first order diffracted beam from each acousto - optic modulator ; monitoring the wavelength of the laser source , providing a visible indicator or diagnostic beam for each first order diffracted beam , and combining each first order diffracted beam with its respective indicator beam to form a texturing beam for texturing each side of the substrate .