Efficiency improvement study of volume phase elements in fused silica toward applications

In this research, we detail the optimization of volume diffraction optical elements, focusing on blazed gratings and fraxicons. A recent study achieved a maximum diffraction efficiency of approximately 76% for the volume fraxicon. However, there is still potential for improvements in both mechanical design and recording strategy to enhance its competitiveness with conventional refractive elements. Our optimization approach was based on the recording of blazed gratings, which was then applied to the fraxicon. We recorded fraxicons with diameters exceeding 5 mm and tested them using a femtosecond laser to demonstrate their effectiveness in materials processing. The performance was then compared to that of a classical refractive axicon.