A method of protecting a surface during laser machining, comprising: directing a fluid (1530,2316, 2416, 2824) into a cavity (122, 318,1522, 2118, 2326, 2426, 2430) of an object being laser machined by laser pulses (212, 1030-1032, 1512, 1612-1613, 2332), where the fluid (1530,2316, 2416, 2824) does not have substantial laser absorption properties at the wavelengths of the laser pulses (212, 1030-1032, 1512, 1612-1613, 2332); directing a plurality of laser pulses (212, 1030-1032, 1512, 1612-1613, 2332) at a wall (114, 1520) of the object being laser machined, where the laser pulses (212, 1030-1032, 1512, 1612-1613, 2332) are configured to form a hole (214, 330, 1518,3114) through the wall (114, 1520) such that at least one laser(212, 1030-1032, 1512, 1612-1613, 2332) pulse passes through the hole (214, 330, 1518,3114) and enters the cavity (122, 318,1522, 2118, 2326, 2426, 2430) while the fluid (1530,2316, 2416, 2824) is directed into the cavity (122, 318,1522, 2118, 2326, 2426, 2430) such that the laser pulse (212, 1030-1032, 1512, 1612-1613, 2332) is incident on the fluid (1530,2316, 2416, 2824) and a surface together in order to inhibit backwall damage; and positioning a protection substrate (312, 2312, 2412, 2612, 2712, 2722, 2822) having the surface within the cavity (122, 318,1522, 2118, 2326, 2426, 2430) such that the laser pulse (212, 1030-1032, 1512, 1612-1613, 2332) passing through the hole (214, 330, 1518,3114) and into the cavity (122, 318,1522, 2118, 2326, 2426, 2430) is incident upon the surface of the protection substrate (312, 2312, 2412, 2612, 2712, 2722, 2822), wherein the directing the fluid (1530,2316, 2416, 2824) into the cavity (122, 318,1522, 2118, 2326, 2426, 2430) comprises directing the fluid (1530,2316, 2416, 2824) to be in contact with the surface of the protection substrate (312, 2312, 2412, 2612, 2712, 2722, 2822) upon which the laser pulse (212, 1030-1032, 1512, 1612-1613, 2332) is incident; characterized in that the protection substrate (312, 2312, 2412, 2612, 2712, 2722, 2822) comprises a grid of apertures extending through a thickness of the protection substrate (312, 2312, 2412, 2612, 2712, 2722, 2822). directing a fluid (1530,2316, 2416, 2824) into a cavity (122, 318,1522, 2118, 2326, 2426, 2430) of an object being laser machined by laser pulses (212, 1030-1032, 1512, 1612-1613, 2332), where the fluid (1530,2316, 2416, 2824) does not have substantial laser absorption properties at the wavelengths of the laser pulses (212, 1030-1032, 1512, 1612-1613, 2332); directing a plurality of laser pulses (212, 1030-1032, 1512, 1612-1613, 2332) at a wall (114, 1520) of the object being laser machined, where the laser pulses (212, 1030-1032, 1512, 1612-1613, 2332) are configured to form a hole (214, 330, 1518,3114) through the wall (114, 1520) such that at least one laser(212, 1030-1032, 1512, 1612-1613, 2332) pulse passes through the hole (214, 330, 1518,3114) and enters the cavity (122, 318,1522, 2118, 2326, 2426, 2430) while the fluid (1530,2316, 2416, 2824) is directed into the cavity (122, 318,1522, 2118, 2326, 2426, 2430) such that the laser pulse (212, 1030-1032, 1512, 1612-1613, 2332) is incident on the fluid (1530,2316, 2416, 2824) and a surface together in order to inhibit backwall damage; and positioning a protection substrate (312, 2312, 2412, 2612, 2712, 2722, 2822) having the surface within the cavity (122, 318,1522, 2118, 2326, 2426, 2430) such that the laser pulse (212, 1030-1032, 1512, 1612-1613, 2332) passing through the hole (214, 330, 1518,3114) and into the cavity (122, 318,1522, 2118, 2326, 2426, 2430) is incident upon the surface of the protection substrate (312, 2312, 2412, 2612, 2712, 2722, 2822), wherein the directing the fluid (1530,2316, 2416, 2824) into the cavity (122, 318,1522, 2118, 2326, 2426, 2430) comprises directing the fluid (1530,2316, 2416, 2824) to be in contact with the surface of the protection substrate (312, 2312, 2412, 2612, 2712, 2722, 2822) upon which the laser pulse (212, 1030-1032, 1512, 1612-1613, 2332) is incident; characterized in that the protection substrate (312, 2312, 2412, 2612, 2712, 2722, 2822) comprises a grid of apertures extending through a thickness of the protection substrate (312, 2312, 2412, 2612, 2712, 2722, 2822).