The CsPbBr3 microwires with unique isosceles right triangle cross-sections are commonly observed via chemical vapor deposition method. In this work, we study the correlations between measured multi-mode lasing behaviors and the simulation of the mode patterns inside the triangular-rod microcavity. We confirm that lasing action with higher-order transverse modes can well sustain, even when these modes experience large optical loss due to the isosceles triangle cross-section. By comparing the experimental and simulation results, the higher-order transverse modes tend to show up prior to the fundamental transverse modes for wider microwires. We attribute this behavior to the nonuniform field distribution caused by the high absorption efficiency of CsPbBr3. We also elaborate on the difficulties to sustain the whispering gallery mode in the CsPbBr3 triangular-rod microcavity, which implies that the lateral dimension and geometry of the cavity should be considered carefully for the future design of low threshold wire-based laser devices.

No abstract

In this study, the method of low-temperature atomic layer deposition (ALD), which is applied on the soft photo-resist (PR) substrate forming hafnium dioxide (HfO2) at 40 o C to 85 o C, is reported for the first time. This reveals the potential application in the TEM sample preparation. The thickness, refractive index, band gap, and depth profiling chemical state of the thin film are analyzed by ellipsometry, X-ray diffraction, and photoelectron spectroscopy respectively. Our TEM image shows a clear boundary between the photo-resist and hafnium dioxide deposited on PR, which indicates the low-temperature atomic layer deposition (ALD) may lead a new way for TEM sample preparation in advanced technology node.

No abstract

No abstract

No abstract

In recent years, metamaterial has gained tremendous attention for its extraordinary properties and applications in both microwave and optical regime. It is categorized as a material with negative permittivity or permeability. At high THz frequency (such as optical communication band), metals possess negative epsilon as metamaterials. Due to the rapid growth of nanotechnology, sub-micron metal waveguides can confine optical fields at nano-scale (much smaller than signal wavelength) that cannot be achieved by pure dielectric. This kind of waveguide is also called plasmonic waveguide that guides wave in the form of surface plasmons, which is known as electron oscillation on metal surfaces.Finite-Difference-Time-Domain (FDTD) method is widely used for the electromagnetic wave propagation in microwave and optical devices/systems for its intuitive algorithm and fast broad band simulation. However, for plasmonic devices, fields are confined around the metal-dielectric interface with regions that are much smaller than the signal wavelength; therefore in order to precisely describe the field behavior, the number of grids in the simulation has to be increased greatly. In the mean time, the stair casing error caused by the index contrast between the metal with negative real permittivity and dielectric with positive real permittivity will affect the numerical stability significantly. Under this situation, some sub-pixel smoothing techniques such as contour-path integral or effective permittivity method have to be imposed at material interfaces to obtain the numerical stability.Currently, the powerful open-source FDTD package, Meep, developed by MIT has no sub-pixel smoothing function enabled for dispersive materials that can be utilized to model metals for plasmonic related problems. This somehow prevents users to simulate structures with large index contrast.In this work, we will demonstrate the use of effective permittivity at metaldielectric tilt interface in Meep without modifying the source code itself to reduce the stair-casing error for the simulation of plasmonic devices, which will help front-end users to utilize it to deal with more complex problems. 75

No abstract