In this work, we present a family of direct tomography protocols that can characterize various types of high-dimensional photon states. In specific, we show direct tomography approaches that can measure high-dimensional spatial modes, spatial vector modes and partially-coherent modes. In direct tomography methods, the measurement readouts directly correspond to the complex-valued state vector or other quantities that describe the quantum system to be measured, and therefore can significantly reduce the complexity of tomography procedures for high-dimensional states. Moreover, we show that it is possible to design the tomography protocol such that all the information needed to describe the photon states can be acquired in a single experimental setup without any need of scanning. This is particularly interesting for real-time metrology of both quantum and classical photon states. The unique single-shot, direct characterization capability provide powerful real-time metrology tools that can boost fundamental studies and applications of high-dimensional photon states.
Lithographic patterning at the 7 and 5 nm nodes will likely require EUV (λ=13.5 nm) lithography for many of the critical
levels. All optical elements in an EUV scanner are reflective which requires the EUV photomask to be illuminated at an
angle to its normal. Current scanners have an incidence of 6 degree, but future designs will be <6 degrees for high-NA
systems. Non-telecentricity has been shown to cause H-V bias due to shadowing, pattern shift through focus, and image
contrast lost due to apodization by the reflective mask coating. A thinner EUV absorber can dramatically reduce these
issues. Ni offers better EUV absorption than Ta-based materials, which hold promise as a thinner absorber candidate.
Unfortunately, the challenge of etching Ni has prevented its adoption into manufacturing. We propose a new absorber
material that infuses Ni nanoparticles into the TaN host medium, allowing for the use of established Ta etching chemistry.
A thinner is absorber is created due to the enhanced absorption properties of the Ni-Ta nano-composite material. Finite
integral method and effective medium theory-based transfer matrix method have been independently developed to analyze
the performance of the nano-composite absorption layer. We show that inserting 15% volume fraction Ni nanoparticles
into 40-nm of TaN absorber material can reduce the reflection below 2% over the EUV range. Numerical simulations
confirm that the reduced reflectivity is due to the increased absorption of Ni, while scattering only contributes to
approximately 0.2% of the reduction in reflectivity.
The mechanism by which light is slowed through ruby has been the subject of great debate. To distinguish between the two main proposed mechanisms, we investigate the problem in the time domain by modulating a laser beam with a chopper to create a clean square wave. By exploring the trailing edge of the pulsed laser beam propagating through ruby, we can determine whether energy is delayed beyond the input pulse. The effects of a time-varying absorber alone cannot delay energy into the trailing edge of the pulse, as a time-varying absorber can only attenuate a coherent pulse. Therefore, our observation of an increase in intensity at the trailing edge of the pulse provides evidence for a complicated model of slow light in ruby that requires more than just pulse reshaping. In addition, investigating the Fourier components of the modulated square wave shows that harmonic components with different frequencies are delayed by different amounts, regardless of the intensity of the component itself. Understanding the difference in delays of the individual Fourier components of the modulated beam reveals the cause of the distortion the pulse undergoes as it propagates through the ruby.
Results are presented here towards robust room-temperature SPSs based on fluorescence in nanocrystals: colloidal
quantum dots, color-center diamonds and doped with trivalent rare-earth ions (TR<sup>3+</sup>). We used cholesteric chiral
photonic bandgap and Bragg-reflector microcavities for single emitter fluorescence enhancement. We also developed
plasmonic bowtie nanoantennas and 2D-Si-photonic bandgap microcavities. The paper also provides short outlines of
other technologies for room-temperature single-photon sources.
A high-intensity laser pulse can lead to a change of the group index of a material, so that the pulse within that
material is slowed to only hundreds of meters per second. This kind of slow-light phenomenon scales with the
optical intensity of the pulse. While previous experiments have produced this effect with an elliptical beam
passing through a spinning ruby window, a question remains as to whether the effect would be present in a
circular beam. Here we use two different methods of producing slow light in a round beam, showing that, while
less pronounced than the effect with an elliptical beam, a slow-light effect can be seen in a round beam.
We discuss the design and development of a slow-light spectrometer on a chip with the particular example of an
arrayed waveguide grating based spectrometer. We investigate designs for slow-light elements based on photonic
crystal waveguides and grating structures. The designs will be fabricated using electron-beam lithography and UV
photolithography on a silicon-on-insulator platform. We optimize the geometry of these structures by numerical
simulations to achieve a uniform and large group index over the largest possible wavelength range.
We propose using slow light structures to greatly enhance the spectral performance of on-chip spectrometers.
We design a calzone photonic crystal line-defect waveguide which can have large group index over a certain
wavelength range. An arrayed waveguide gratings (AWGs) is studied as an example, and the performance of
such a slow-light AWG is analyzed numerically.
Practical applications of slow light methods require that one be able to controllably delay a pulse of light by many pulse lengths. In this contribution we analyze the possible limitations to the maximum achievable time delay and suggest methods for overcoming these limits.
Higher NA optical pick-ups (OPUs) are being applied in optical storage system for high capacity. As the vector characteristics of the laser beam in high NA OPU play an important role in the interaction between the disc information layer and laser beam, simulations based on both vector diffraction theory and rigorous calculation of Maxell’s equations are becoming more and more important. They not only provide accurate and reliable simulation results, but also make it possible to investigate many other interesting topics e.g. the feasibility of using polarized light to increase storage density of optical discs. In this paper, a software package based on three-dimensional finite-difference time domain algorithm (3D-FDTD) is introduced to simulate readout signals. It can be used to simulate the reflection pattern for three dimension geometrical pits accurately. Moreover, because it can interface with optical design program ZEMAX, the simulation can be done for different light paths and in the presence of surface defects, which is very useful for analyzing and evaluating a practical OPU. The features of this software are expected to help explore new disc formats, understanding signals in servo path and data path, and furthermore designing a new optical pick-up etc.