Investigation of multilayer domains in large-scale CVD monolayer graphene by optical imaging

CVD graphene is a promising candidate for optoelectronic applications due to its high quality and high yield.However,multi-layer domains could inevitably form at the nucleation centers during the growth.Here,we propose an optical imaging technique to precisely identify the multilayer domains and also the ratio of their coverage in large-scale CVD monolayer graphene.We have also shown that the stacking disorder in twisted bilayer graphene as well as the impurities on the graphene surface could be distinguished by optical imaging.Finally,we investigated the effects of bilayer domains on the optical and electrical properties of CVD graphene,and found that the carrier mobility of CVD graphene is seriously limited by scattering from bilayer domains.Our results could be useful for guiding future optoelectronic applications of large-scale CVD graphene.

Femtosecond laser-induced breakdown of multilayers and gold film

We report single-shot damage threshold as a function of pulse duration (50-900 fs) for MgF2/ZnS 800-nm omnidirectional-reflection film, interference filter, and gold film. The results indicate that the damage with ultrashort pulse is nonthermal, which is different from that with long pulse. Additionally, the ablation crater depths of 45° high-reflection film and interference filter are presented. A logarithmic relation between the ablation depth and pulse fluence, which is similar to that of transparent materials, is found.

Multi-energy four-channel Kirkpatrick–Baez microscope for X-ray imaging diagnostics at the Shenguang-II laser facility

A four-channel Kirkpatrick Baez microscope working at multiple energy bands is developed for multiframe X-ray imaging diagnostics at the Shenguang-II laser facility. The response to the multiple energy bands is realized by coating the double-periodic multilayers on the reflected surfaces of the microscope. Because of the limited size of the microstrips in the X-ray framing camera, the image separation is controlled by the coni- cal angle of the reference cores during microscope assembly. This study describes the optical and multilayer design, assembly, and aligmnent of the developed microscope. The microscope achieves a spatial resolution of 4 5 gin in the laboratory and 10 20 ~tm at Shenguang-II laser facility within a 300 tim field of view. The versatile nature of the developed microscope enables the multiple microscopes currently installed in the laser facility to be replaced with a single, multipurpose microscope.

Laser induced damage of multi-layer dielectric used in pulse compressor gratings

Laser induced damage threshold (LIDT) of multi-layer dielectric used in pulse compressor gratings (PCG) was investigated. The sample was prepared by e-beam evaporation (EBE). LIDT was detected following ISO standard 11254-1.2. It was found that LIDTs of normal and 51.2° incidence (transverse electric (TE) mode) were 14.14 and 9.31 J/cm2, respectively. A Nomarski microscope was employed to map the damage morphology, and it was found that the damage behavior was pit-concave-plat structure for normal incidence, while it was pit structure for 51.2° incidence with TE mode. The electric field distribution was calculated to illuminate the difference of LIDT between the two incident cases.

Analysis and combined optimization of the cladding layer in out coupling-improved top emitting OLEDs

Within the associated framework of metal-dielectric films optics and the dual-metal-mirror microcavity structure, the effect of a cladding dielectric layer on the light outcoupling efficiency of the top emitting orgainic light-emitting devices (OLEDs) is analyzed. A combined evaluation followed by detailed design and optimization is proposed and described in detail. The analysis shows that this cladding layer affects the device’s outcoupling efficiency with three different extents as the thickness of the metal layer in the multilayer cathode varying. The simulation results give a reasonable agreement with former experiment results.