Temporary storage of light, by means of its slowing down which leads to increase of the local intensity of slow light, has been the subject of intensive research, since many useful optical phenomena rely on strong interaction between light and matter1. Initial attempts to substantially reduce the speed of light were based on quantum effects such as electromagnetic induced transparency2 and optical coherent effects3, where restrictions like the usage of ultracold gases or the narrow operational bandwidth limited their practical implementations. More recently the on-chip realizations of slow light schemes have become possible, such as coupled resonator optical waveguides4, 5, which can lead to low group velocities with negligible distortion. However a fundamental limit, limiting such structures is the so-called delay-bandwidth product, which imposes a trade-off between the factor of slowing-down and the bandwidth in which the slowing, exists6. One way to alleviate this limitation is to adiabatically tune (or chirp) the structure, meaning that one or several structural parameters are gradually varied along the direction of propagation. In particular, it has been shown that in a tapered metamaterial heterostructure, light can be slowed down and trapped at specific locations depending on its frequency using negative Goos–Hänchen shift7. This phenomenon, termed as the “Trapped Rainbow” effect, can also be considered as the spatial separation of the frequency components of the propagating wave, and has been demonstrated in dielectric8 and plasmonic9–18 gratings or waveguides, in one-19 and two-dimensional20–22 photonic crystals (2D PhCs), in a hyperbolic metamaterial waveguide23, in sonic crystals24, and in a waveguide under a tapered magnetic field25. While significant steps have been taken towards the slowing down and “trapping” of the light, one still needs to cope with extrinsic losses while implementing such schemes. It has been debated whether material absorption that is reminiscent of metallic structures can give large propagation losses and prevent the light stopping mechanism in metamaterials26. Although it is possible to overcome the material losses in metamaterials by employing absorption-free dielectric 2D PhCs in their negative refraction regime27 instead of metallic components, it still remains unclear whether other extrinsic loss mechanisms such as out-of-plane radiation losses can be compensated and overcome in such structures. Yet some attempts to reduce the losses in 2D PhCs have been undertaken28, 29, the inevitable relation between the group velocity of the light and its interaction time with the medium still leads to considerable amount of scattering loss enhancement, as one approaches the band edge region (where most of the slow light behavior occurs)27, 30–33.