Direct electron-beam writing of continuous spiral phase plates in negative resist with high power efficiency for optical manipulation

Laser beams propagating in Laguerre-Gaussian (LG) modes are of considerable interest due to their widespread applications in the areas of optical manipulation of microparticles, quantum entanglement of photons, nonlinear optics, optical vortex interactions, and atomic studies. However, the proliferation of LG beams has been hampered due to the absence of reliable and reproducible fabrication technologies in producing the required optical elements for their generation. In this letter, we describe a simple, reliable, and reproducible fabrication technique for a micron-sized spiral phase plate with high power efficiency (80%-90%) and good beam uniformity. This facilitates the widespread use of LG beams in various applications: as an example the fabricated elements can easily and readily be incorporated into an existing optical trapping system with minimum modification.