With the aim to lower the surface roughnesses of etched samples and the etching threshold fluence of a direct laser irradiation source and to raise the yield of micro-optical elements, a laser induced backside dry etching technique with the assistance of a solid medium as the absorbed layer was proposed to fabricate transparent dielectric materials by direct laser irradiation. By using an alumina ceramic wafer (Al2O3 in 95%, surface roughness less than 500 nm) as the absorber, a 2D transmittance grating in a micro size binary Diffractive Optical Element (DOE) was fabricated on the fused silica with a thickness of 3.2 mm by the 1 064 nm Ytterbium Doped Fiber (YDF) laser. And then, the etching parameter curves were fitted and the effect of laser energy density on the parameters was discussed. Finally, the diffraction patterns of micro structure were observed to examine the features of binary DOE. According to the measured results, the binary transmittance grating shows its grating constant in 25 μm,the depth of trench in 4.2 μm, and the RMS roughness of the trench bottom below 40 nm. Furthermore, the etching threshold influence is estimated below 7.66 J/cm2. These results are much lower than those of the etching without any absorbers.