In order to improve the purity, compactness and uniformity of magnetron sputtering deposited films at a lower cost, a dual-chamber DC heating filament auxiliary ion source was designed which can activate oxygen. The working parameters of the auxiliary ion source were changed in the experiment to explore their influence on the optical parameters of the films deposited by magnetron sputtering coater. By comparing the transmittance, refractive index and relative thickness of the films which was deposited under different processing conditions, it is finally proved that the auxiliary ion source designed in this work can improve the transmittance, compactness and uniformity of the single-layer films of Ta205 and SiO2 which was coated in this experiment. Thus, the coating quality and effective coating area of the original magnetron sputtering coating machine are improved, and it does have certain practical significance for improving the efficiency of the coating.
Using the discrete dipole approximation (DDA) method, we propose a sandwiched nano-film system that consists of a continuous metal film and two two-dimensional (2D) nanoparticle arrays separated by two layers of glass substrates. Varying the thickness of the glass substrate layers, the localized and propagating surface plasmon polaritions (SPPs) can interact constructively to enhance the transmission of the continuous metal film. The transmission efficiency can be as high as 80% for a continuous silver film with a thickness of 50 nm, which is a 16-fold increase in comparison to that of an isolated metal film only. The FWHM of the transmission peak can also be controlled through changing the interparticle distances and other parameters of the nanoparticles. The significantly enhanced transmission provides us a new approach for the study the optical properties of a continuous metal film and the design of novel devices with enhanced transmission based on nanostructures.
The CMOS single photon avalanche photodiode (SPAD) image sensor, as the third-generation solid-state imaging device, features single photon response capability, picosecond magnitude time resolution and micron-scale spatial resolution. The device is currently the mainstream ideal device for single-photon, picosecond time-resolved transient imaging, and is gradually applied to time-resolved spectral measurement, 3D ranging and imaging, fluorescence lifetime imaging, quantum imaging sensing and such low light or even single photon ultrafast imaging. In this paper, we introduce the research progress of the CMOS SPAD image sensor, and the challenges and solutions of the device are analyzed. In the past years, the mainstream CMOS SPAD image sensor features front-illuminated SPAD and the planar-structure pixel. However, for the planar-structure pixel, in order to make the SPAD with higher fill factor, reducing the duty cycle of the readout electronics within the pixel is the usual method, which to some extent sacrifices the function of reading electronics. In addition, the lower process node was used to improve the integration of electronics, but the high dark count rate was easily caused; The integration of micro-lens array in pixels was also used, but limits the flexibility of pixel size and increases the costs. Compared with planar-structure pixel, the pixel scheme of the three dimensional (3D) stacked structure, integrates the SPAD device and the readout electronics in the pixel correspondingly on the vertically coupled two wafers, which eliminates the problem of duty cycle of the readout electronics within the pixel and would be the development direction in the future.
In this work, we investigated how the blinking statistics and the photon antibunching behavior of single CdSe/CdS
core/shell quantum dots(QDs) get modified in the presence of gold nanoparticles(Au NPs) overcoated with a silica shell
of varying thickness.(Au@SiO2). The Au@SiO2 NPs have distinct plasmon resonance peaks which overlap with the
absorption and emission of QDs, thereby effectively increasing the mutual plasmon-exciton interactions between them.
From the second-order photoluminescence intensity cross-correlation measurements, we observed that in the regime of
low excitation power, the relative ratio of the biexciton/exciton (BX/X) quantum yield (QY) and lifetimes of the single
QDs in presence of the plasmonic substrates get significantly modified as compared to the QDs on glass. An
electrodynamics model was developed to further quantify the effect of plasmons on the emission intensity, QY and
lifetimes of X and BX of single QDs. The theoretical studies also indicated that the relative position of the QDs and
orientation of the electric field are the critical factors regulating the emission properties of Xs and BXs.
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