Partially coherent laser beam shaping in a zoom homogenizer.

This paper proposes a synthesis method including wave optics and geometric optics to design the zoom homogenizer for partially coherent laser beams and discusses the effects of the spatial coherence and system parameters on the beam performance. Based on the principles of pseudo-mode representation and matrix optics, a numerical model for fast simulation has been built and the parameter constraints for avoiding beamlet crosstalk have been presented. The relation of the size and the divergence angle of the highly uniform beams formed in the defocused plane with system parameters has been developed.

Designing diffractive optical elements for shaping partially coherent beams by proximity correction.

We propose a new method to design diffractive optical elements (DOE) for shaping partially coherent beams. The diffraction patterns of a DOE under a certain partially coherent beam can be modeled by the convolution of the coherent diffraction pattern and the inherent degree of coherent function. Two basic types of diffraction anomalies induced by partially coherent beams are discussed, including line-end shortening and corner rounding.

Photoacoustic identification of laser-induced microbubbles as light scattering centers for optical limiting in a liquid suspension of graphene nanosheets.

Liquid suspensions of carbon nanotubes, graphene and transition metal dichalcogenides have exhibited excellent performance in optical limiting. However, the underlying mechanism has remained elusive and is generally ascribed to their superior nonlinear optical properties such as nonlinear absorption or nonlinear scattering. Using graphene as an example, we show that photo-thermal microbubbles are responsible for optical limiting as strong light scattering centers: graphene sheets absorb incident light and become heated up above the boiling point of water, resulting in vapor and microbubble generation.

Extrinsic Green Photoluminescence from the Edges of 2D Cesium Lead Halides.

Since the first report of the green emission of 2D all-inorganic CsPb Br , its bandgap and photoluminescence (PL) origin have generated intense debate and remained controversial. After the discovery that PL centers occupy only specific morphological structures in CsPb Br , a two-step highly sensitive and noninvasive optical technique is employed to resolve the controversy. Same-spot Raman-PL as a static property-structure probe reveals that CsPbBr nanocrystals are contributing to the green emission of CsPb Br ; pressure-dependent Raman-PL with a diamond anvil cell as a dynamic probe further rules out point defects such as Br vacancies as an alternative mechanism.

4.24 μm mid-infrared laser based on a single Fe-doped ZnSe microcrystal.

In this Letter, we report for the first time, to the best of our knowledge, a micron-sized mid-infrared Fe:ZnSe laser based on a single microcrystal. Typical laser emissions centering at 4.24 μm are observed from a selected Fe-doped ZnSe microcrystal under 2.