Measurement of the transmission spectrum

Measurement of the transmission spectrum of gyroid structures was performed using a home-made setup. A white light beam traveling through a broadband half waveplate was focused by a 40× 0.65 NA (numerical aperture) objective lens. The fabricated artificial gyroid samples were aligned to the position where the focal spot of the white light beam could travel through the structure center at a normal incident angle. This allowed light to transmit through the [001] axis of gyroid structures. Before traveling through the structure, the white light beam was designed to travel through a broadband quarter waveplate. The transmitted light was collected by a 100× 0.8 NA objective lens and sent to a spectrograph to obtain the spectrum of the white light beam. The broadband quarter waveplate was rotated relative to the half waveplate to achieve a left- or right-handed circular polarization beam entering the structure. The transmission spectra shown in Fig. 5 were normalized by the measured white light beam spectrum with the sample removed.