  The perfect absorption of light in subwavelength thickness layers generally
relies on exotic materials, metamaterials or thick metallic gratings. Here we
demonstrate that total light absorption can be achieved in ultra-thin gratings
composed of conventional materials, including relatively weakly-absorbing
semiconductors, which are compatible with optoelectronic applications such as
photodetectors and optical modulators. We fabricate a 41 nm thick antimony
sulphide grating structure that has a measured absorptance of A = 99.3% at a
visible wavelength of 591 nm, in excellent agreement with theory. We infer that
the absorption within the grating is A = 98.7%, with only A = 0.6% within the
silver mirror. A planar reference sample absorbs A = 7.7% at this wavelength.
