Targeted transfer of self-assembled CdSe nanoplatelet film onto WS_(2) flakes to construct hybrid heterostructures

Colloidal CdSe nanoplatelets are thin semiconductor materials with atomic flatness surfaces and one-dimensional strong quantum confinement,and hence they own very narrow and anisotropic emission.Here,we present a polydimethylsiloxane(PDMS)assisted transferring method that can pick up single layer CdSe nanoplatelet films self-assembled on a liquid surface and then precisely transfer to a target.By layer-by-layer picking up and transferring,multiple layers of CdSe films can be built up to form CdSe stacks with each single layer having dominant in-plane transition dipole distribution,which both material and energic structures are analogous to traditional multiple quantum wells grown by molecular-beam epitaxy.Additionally,with the great flexibility of colloidal nanoplatelets and this transferring method,CdSe nanoplatelets films can be combined with other materials to form hybrid heterostructures.We transferred a single-layer CdSe film onto WS_(2) flakes,and precisely studied the fast energy transfer rate with controlled CdSe nanoplatelet orientation and by using a streak camera with a ps time resolution.

Detour-phased perovskite ultrathin planar lens using direct femtosecond laser writing

Perovskite-enabled optical devices have drawn intensive interest and have been considered promising candidates for integrated optoelectronic systems.As one of the important photonic functions,optical phase modulation previously was demonstrated with perovskite substrate and complex refractive index engineering with laser scribing.Here we report on the new scheme of achieving efficient phase modulation by combining detour phase design with 40 nm ultrathin perovskite films composed of nanosized crystalline particles.Phase modulation was realized by binary amplitude patterning,which significantly simplifies the fabrication process.Perovskite nanocrystal films exhibit significantly weak ion migration effects under femtosecond laser writing,resulting in smooth edges along the laser ablated area and high diffractive optical quality.Fabrication of a detour-phased perovskite ultrathin planar lens with a diameter of 150μm using femtosecond laser scribing was experimentally demonstrated.A high-performance 3D focus was observed,and the fabrication showed a high tolerance with different laser writing powers.Furthermore,the high-quality imaging capability of perovskite ultrathin planar lenses with a suppressed background was also demonstrated.