Optical properties of injection molded subwavelength gratings

We have fabricated injection molded subwavelength gratings for anti-reflection purposes superimposed upon a blazed grating structure in polycarbonate. The gratings are initially formed by electron-beam lithography and subsequently replicated using injection molding. There are several problems when trying to optically characterize a component such as a blazed transmittance grating. Standard spectrophotometers are not well suited for measuring transmittance in the different diffraction orders individually. Our sample size of 0.8x0.8 mm(2) is also a problem for standard instruments. First order transmittance has been measured for blazed gratings with single and double-sided AR-treatment and is transmittance is compared with with higher diffraction orders. Double-sided AR-treatment not only increase the total transmittance but also widens the wavelength range with high effectiveness of the first order diffraction.