Paths for New Urbanization in Chongqing, China: Study on Overall Design and Strategic Framework

Based on introspection about disadvantages of the traditional urbanization, the new urbanization is on the transformation and innovation of strategies with reference to the relevant successful experience all over the world. Through analyses on the consequent strategic opportunity of Chongqing pilot zone for overall reform to balance the urban and rural development, the paper expounds an overall idea on paths for new urbanization in Chongqing. And then the paper constructs a strategic framework of the paths aiming to provide a scientific and clear direction to the choice of paths for new urbanization in Chongqing.

Ultra-high vibrational and rotational motion of the HF molecule via Infrared (IR) laser excitation

Our goals this summer were to build on previous work in our group modeling ultra-high vibrational and rotational excitation in small molecules via unique pulse sequencing of an infrared (IR) laser. The system was modeled both using Fortran and Mathematica as programming languages. We were able to demonstrate that different numerical techniques for propagating coupled differential equations forward in time led to equivalent levels of vibrational excitation and allowed for identical visualization of molecular state probabilities as a function of time. Work including the rotational motion progressed to the point of being able to see both significant excitation when rotations are included as well as leaking into neighboring rotational states as expected. Much work remains to be done before a full analysis of the rotational excitation can be completed

Lithium niobate photonic-crystal electro-optic modulator

Modern advanced photonic integrated circuits require dense integration of high-speed electro-optic functional elements on a compact chip that consumes only moderate power. Energy efficiency, operation speed, and device dimension are thus crucial metrics underlying almost all current developments of photonic signal processing units. Recently, thin-film lithium niobate (LN) emerges as a promising platform for photonic integrated circuits. Here we make an important step towards miniaturizing functional components on this platform, reporting probably the smallest high-speed LN electro-optic modulators, based upon photonic crystal nanobeam resonators. The devices exhibit a significant tuning efficiency up to 1.98 GHz/V, a broad modulation bandwidth of 17.5 GHz, while with a tiny electro-optic modal volume of only 0.58 $\mu {\rm m}^3$. The modulators enable efficient electro-optic driving of high-Q photonic cavity modes in both adiabatic and non-adiabatic regimes, and allow us to achieve electro-optic switching at 11 Gb/s with a bit-switching energy as low as 22 fJ. The demonstration of energy efficient and high-speed electro-optic modulation at the wavelength scale paves a crucial foundation for realizing large-scale LN photonic integrated circuits that are of immense importance for broad applications in data communication, microwave photonics, and quantum photonics

Chip-scale Simulations in a Quantum-correlated Synthetic Space

An efficient simulator for quantum systems is one of the original goals for the efforts to develop a quantum computer [1]. In recent years, synthetic dimension in photonics [2] have emerged as a potentially powerful approach for simulation that is free from the constraint of geometric dimensionality. Here we demonstrate a quantum-correlated synthetic crystal, based upon a coherently-controlled broadband quantum frequency comb produced in a chip-scale dynamically modulated lithium niobate microresonator. The time-frequency entanglement inherent with the comb modes significantly extends the dimensionality of the synthetic space, creating a massive nearly 400 x 400 synthetic lattice with electrically-controlled tunability. With such a system, we are able to utilize the evolution of quantum correlations between entangled photons to perform a series of simulations, demonstrating quantum random walks, Bloch oscillations, and multi-level Rabi oscillations in the time and frequency correlation space. The device combines the simplicity of monolithic nanophotonic architecture, high dimensionality of a quantum-correlated synthetic space, and on-chip coherent control, which opens up an avenue towards chip-scale implementation of large-scale analog quantum simulation and computation [1,3,4] in the time-frequency domain.Comment: 21 pages, 14 figures (including supplementary materials

A self-starting bi-chromatic LiNbO_3 soliton microcomb

The wide range of functions that are possible with lithium niobate (LN) waveguide devices, including phase and intensity modulation, second-harmonic generation, and difference-frequency generation, makes it attractive as a potential microcomb material. LN microcombs would combine essential comb self-referencing and control functions with the pulse generation process in a single microresonator device. Here, we demonstrate a soliton microcomb in a monolithic high-Q LN resonator. Direct frequency doubling of the soliton spectrum is observed inside the same cavity. The LN soliton mode-locking process also self-starts and allows bi-directional switching of soliton states, effects that are shown to result from the LN photorefractive effect. The Kerr solitons exhibit a self-frequency shift resulting from the Raman effect of LN. This microcomb platform can dramatically simplify miniature time keeping, frequency synthesis/division, and spectroscopy systems. Moreover, direct generation of femtosecond timescale pulses within LN microresonators can benefit quantum photonics and signal processing systems