Subwavelength diffraction gratings in the visible spectral range

We report the results of computer calculations and measurements of subwavelength diffraction gratings in the visible range of the radiation spectrum. The influence of various grating parameters (duty cycle, microrelief shape and depth, material, angle of incidence, wavelength, and radiation polarisation) on the diffraction efficiency is studied. A distinctive feature of the subwavelength gratings in question is that the entire diffracted energy of the beam is redistributed into the zero and –1st orders. It is found that the zero order can be suppressed by choosing the depth and shape of the grating relief. The subwavelength gratings with a period of 400 nm are fabricated and measurements are performed using lasers and laser diodes emitting in the visible wavelength range. High diffraction efficiency into the –1st order (more than 70%) is observed in a wide spectral range of 450–650 nm with an increase in the grating relief depth (at a depth of h = 80 nm). It is experimentally demonstrated that under certain conditions, the plasmon resonance effect arises, in which total absorption of incident radiation takes place. The optical elements considered can be used in image processing systems, projection displays, in the development of various sensors, etc.