Quasi-phase-matching with Spontaneous Domain Inversion in an Integrated Lithium Niobate Micro-racetrack Resonator

Quasi-phase-matching (QPM) technology is the most popular and significant method to achieve efficient nonlinear frequency conversion. The realization of periodically poling to achieve QPM in photonic integrated circuits (PICs) is a challenging issue for the requirement of CMOS compatible and large-scale fabrication. Here we realize a spontaneous periodical domain inversion without poling but by dispersion engineering and designing the orientation of the crystal due to the circular propagation of light waves in an integrated lithium niobate micro-racetrack resonator (MRR). The QPM second harmonic generation (SHG) with a normalized conversion efficiency of 2.25$\%$/W (169th-order QPM) has been achieved in the high-quality factor resonator of $\sim 10^{8}$ with the straight waveguide (TE$_{00}$ mode) of ultra-low propagation loss of 0.0022dB/cm. The efficiency can be further enhanced by using a first-order QPM, and the bandwidth can be made broader by employing a shorter interaction length for photonics and quantum optics. The configurable spontaneous quasi-phase-matching lithium niobate MRR on X-cut thin-film lithium niobate on insulator (LNOI) provides a significant on-chip integrated platform for other optical parametric processes

Along the Giant’s Footprints: Bama China

When McDonald’s entered Chinese market in 1989, Bama Company, a key supplier of McDonald’s deserts, followed to explore this potential high-volume bakery goods kingdom in Asia. Having been influenced by western culture since the economic reform in the 1980s, Chinese people, especially the young generation, love to enrich their daily diet with western food. Along with American fast food booming in China, bakery products, such as cakes, cookies, and other deserts are also well accepted by consumers. This case introduces how Bama grows its international market by following its giant client. While maintaining its long term partnership with McDonald’s, Bama also develops other clients in the fast food chain in this unfamiliar yet exciting world. Bama China further seeks more expansion and explores larger growth in the Asian-Pacific region to develop bakery markets. This case study discusses several options for the future of Bama China

Experimental study on the application of air-source heat pump in a warm-temperate extreme-arid-desert climate zone

Clean and low-carbon heating methods are vigorously promoted in China under a carbon peak and carbon neutrality background. The application of air-source heat pump system (ASHP) technology has become a research hotspot as a clean and low-carbon heating method. This paper investigated the performance of an ASHP applied in Hotan, Xinjiang, China, categorized as a warm-temperate extreme-arid-desert climate (WT-EADC) zone. The actual performance of an air-source heat pump heating system with radiant floor heating (ASHP-RF) was tested experimentally using a WT-EADC zone. The system performance of the low-temperature and high-humidity climate (LTHHC), typical climate (TC), and high-temperature and low-humidity climate (HTLHC) was thoroughly examined. Results show that the system performances of the LTHHC, TC, and, HTLHC differ significantly. The average coefficient of performance (COP) values of the system under these conditions were 2.13, 2.24, and 2.46, respectively. The COP of the system increased initially with increasing ambient temperature and decreased with increasing ambient relative humidity. During the operation of the ASHP-RF, there was an ambient relative humidity corresponding to the optimal efficiency. The experimental results demonstrated that the ASHP-RF completely met the heating demand of buildings under a warm-temperate extreme-arid-desert climate, demonstrating the advantages of high efficiency and exhibiting broad-application prospects