News on China's scientific and technological development.

China's spending on research and development (R&D) exceeded 3 trillion yuan (about $442.63 billion) for the first time in 2022, and is estimated to account for 2.55% of the country's GDP, both hitting record highs: data from the National Bureau of Statistics..

The digital connections for the mobile internet of things in China reached 1.84 billion in 2022, making the 1st major economy in the world to have more mobile IoT connections than the number of its mobile users, according to Ministry of Industry and Information Technology..

World Record Alert ..

China had registered 4.212 million valid Patents as of the end of 2022, making it the first country to pass the threshold of 3 million. Of the patents there are 1.324 million high-value patents, up 24.2% YOY, the National Intellectual Property Administration data showed..

China strives to double the density of its manufacturing robots by 2025.

How China's space technology helps its agriculture:

Chinese researchers demo'ed terebit (1.02T bps) free space optical communication (aka network on laser beams) between two buildings of 1km apart.

The work is based on soliton microcomb which is more power efficient and compact than systems that use the wavelength-division multiplexing (WDM) technology. Although WDM-based systems have had demo of higher bandwidth up to 10T bps.

Paper in English:

Terabit FSO communication based on a soliton microcomb​

Abstract​

Free-space optical (FSO) communication technology is a promising approach to establish a secure wireless link, which has the advantages of excellent directionality, large bandwidth, multiple services, low mass and less power requirements, and easy and fast deployments. Increasing the communication capacity is the perennial goal in both scientific and engineer communities. In this paper, we experimentally demonstrate a Tbit/s parallel FSO communication system using a soliton microcomb as a multiple wavelength laser source. Two communication terminals are installed in two buildings with a straight-line distance of ∼1 km. 102 comb lines are modulated by 10 Gbit/s differential phase-shift keying signals and demodulated using a delay-line interferometer. When the transmitted optical power is amplified to 19.8 dBm, 42 optical channels have optical signal-to-noise ratios higher than 27 dB and bit error rates less than 1×10−9. Our experiment shows the feasibility of a wavelength-division multiplexing FSO communication system which suits the ultra-high-speed wireless transmission application scenarios in future satellite-based communications, disaster recovery, defense, last mile problems in networks and remote sensing, and so on.

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To date, up to 10 Gbit/s FSO communication system has been realized for transmission distance over 1000 km of star-ground or inter-star communications [

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], and 208 Gbit/s terrestrial communication is also reported at 55 m transmission distance [

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]. Wavelength-division multiplexing (WDM) technology is commonly employed to improve data transmission capacity in fiber communication systems, which would be more effective in FSO communication systems benefitting from very weak non-linear cross talk between different frequency channels in free space. Based on a simulation platform, a WDM FSO communication system could boost the signal transmission capacity to 1.28 Tbit/s by modulating 32 optical channels with dual-polarization 16 quadrature amplitude modulation signals [

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]. To date, beyond 10 Tbit/s FSO communication systems have been experimentally demonstrated recently using WDM technology [

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,

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]. However, a WDM communication system becomes power-hungry and bulky with the increase of transmission channels while traditional distributed feedback lasers are used as optical carriers. In addition, more rigorous requirement is imposed on the frequency tolerance of carrier lasers to avoid channel overlap with the decrease of channel frequency interval.

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News release in Chinese:

近日，中国科学院西安光学精密机械研究所在超高速空间光通信技术研究中取得重要进展。相关研究成果以Terabit FSO communication based on a soliton microcomb为题，作为封面文章，发表在Photonics Research上。

自由空间激光通信（FSOC）是一种利用激光束作为载波在空间进行信息传递的通信方式，相比于微波通信，具有传输速率高、抗电磁干扰性能强、保密性好、无频谱限制等优势，同时，终端体积小，易于部署、功耗低，是解决信息传输“最后一英里”难题的理想选择，在应急通信、星地通信和星间通信等场景中颇具应用价值。

建立大容量、长传输距离FSOC系统是当下领域内的研究热点。片上微腔孤子光频梳（SMC）具有超高重复频率，且各个梳齿具有严格相等的频率间隔，是波分复用FSOC系统的理想激光光源。西安光机所研究员谢小平与光子网络技术研究室研究员汪伟团队、瞬态光学与光子技术国家重点实验室研究员张文富和副研究员王伟强团队合作，利用新兴的微腔孤子光频梳代替传统的半导体可调谐激光阵列作为多载波光源，使用10 Gbit/s差分相移键控调制信号，在相距1 km的自由空间光通信链路上实现了总速率为1.02 Tbps的并行数据传输。该工作将片上微腔孤子光频梳作为多波长光源应用于自由空间光通信研究，对提升自由空间光通信的容量和解决自由空间光通信的体积重量和功耗（SWaP）问题具有重要意义，并为未来大容量、长距离自由空间光通信发展提供了新途径。

西安光机所致力于超高速激光通信领域进行前沿科学探索、关键技术攻关和工程应用研究，多年深耕的成果已在卫星互联网“新基建”、海洋强国建设、道路交通安全防控等国家重大需求中得到重要应用，获得各界广泛好评和认可。

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Could pulse shaping of extreme ultraviolet lasers have some use in lithography, in addition to "opto-optical modulators" and "future ultra-fast switching devices"?

Chinese scientists recently realized "quasicomplete extinction of XUV light at the resonant frequency" using femtosecond near-infrared (NIR) laser.

Paper in English:

We propose and study the manipulation of the macroscopic transient absorption of an ensemble of open two-level systems via temporal engineering. The key idea is to impose an ultrashort temporal gate on the polarization decay of the system by transient absorption spectroscopy, thus confining its free evolution and the natural reshaping of the excitation pulse. The numerical and analytical results demonstrate that even at moderate optical depths, the resonant absorption of light can be reduced or significantly enhanced by more than 5 orders of magnitude relative to that without laser manipulation. The achievement of the quasicomplete extinction of light at the resonant frequency, here referred to as resonant perfect absorption, arises from the full destructive interference between the excitation pulse and its subpulses developed and tailored during propagation, and is revealed to be connected with the formation of zero-area pulses in the time domain.

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In conclusion, we have demonstrated a general scheme for manipulating the macroscopic transient absorption of an ensemble of two-level systems and shaping XUV radiation. It is remarkable that a temporal gate enables a rapid switching of the medium’s absorption properties, and the resonant perfect absorption can be achieved at certain conditions. Moreover, the latter is proved to be connected with the formation of zero-area pulses in the time domain when driven by resonant pulses. The presented concept is robust against different settings and persists even in a realistic scenario, whose further exploration opens promising directions for future ultrafast switching devices. We envision an organized act of more complex light-matter interactions and pulse propagation in macroscopic media to open new routes for the temporal engineering of high-frequency responses and pulse shapes.

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News story in Chinese:

近日，兰州大学核科学与技术学院、稀有同位素前沿科学中心刘作业教授团队与德国马克斯普朗克核物理研究所、耶拿大学以及美国路易斯安纳州立大学科研人员合作，提出了一种利用超短激光脉冲实现介质无共振腔完美共振吸收的方案。相关研究工作以《Resonant Perfect Absorption Yielded by Zero-Area Pulses》为题，发表在物理学顶级期刊《Physical Review Letters》（《物理评论快报》）上。论文第一作者为核科学与技术学院博士研究生何宇，通讯作者为刘作业教授。

探索微观粒子的运动状态有助于人类认识物质的本质，进而控制和改变物质变化相关过程来实现物质的新性质和新功能。对光脉冲的有效操控是实现对微观粒子动力学控制的基础。基于可编程空间光调制器的可见光整形技术已在相干控制领域取得了很大成功。但在极紫外以及X-射线波段，由于缺乏有效的介质，现有技术方案是无法实现的。

基于瞬态吸收光谱在激发-调控（XUV-NIR）作用框架下，研究提出了一种通过时域选通法，操纵共振介质吸收特性的普适方案，实现了介质对光脉冲的完美吸收（99.999%），且吸收度在飞秒时间尺度上可控。分析发现通过在时域上裁剪XUV脉冲限制系统自由演化并结合激发脉冲在介质内传播过程的自然整形，使其传播后建立的子脉冲与主脉冲实现相干相消。该方案将激光波长锁定到共振跃迁频率且无需使用光学谐振腔，证实了宏观介质的共振吸收在超快时间尺度上可调，在极紫外以及更短波段X-射线的脉冲整形、超快光开关及未来光-光调制器的实现等领域具有重要应用价值。

该研究工作得到了国家自然科学基金重大仪器研制和大科学装置培育、兰州大学优秀青年基金、甘肃省优秀研究生“创新之星”等项目的支持。

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sunnymaxi said:

China's spending on research and development (R&D) exceeded 3 trillion yuan (about $442.63 billion) for the first time in 2022, and is estimated to account for 2.55% of the country's GDP, both hitting record highs: data from the National Bureau of Statistics..

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woww, more than 2x total PLA defense spending

Yet another achievement by Chinese scientists in optics and laser technology.

Paper in English:

kHz-precision wavemeter based on reconfigurable microsoliton​

The mode-locked microcomb offers a unique and compact solution for photonics applications, ranging from the optical communications, the optical clock, optical ranging, the precision spectroscopy, novel quantum light source, to photonic artificial intelligence. However, the photonic micro-structures are suffering from the perturbations arising from environment thermal noises and also laser-induced nonlinear effects, leading to the frequency instability of the generated comb. Here, a universal mechanism for fully stabilizing the microcomb is proposed and experimentally verified. By incorporating two global tuning approaches and the autonomous thermal locking mechanism, the pump laser frequency and repetition rate of the microcomb can be controlled independently in real-time without interrupting the microcomb generation. The high stability and controllability of the microcomb frequency enables its application in wavelength measurement with a precision of about 1 kHz. The approach for the full control of comb frequency could be applied in various microcomb platforms, and improve their performances in timing, spectroscopy, and sensing.

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We demonstrate the fast, programmable and through frequency controlling of arbitrary comb line, and show a frequency measurement precision around kHz in a proof-of-principle demonstration of wavemeter. Compared to previous work with precision of several MHz

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, the precision of our work achieves a three-order of magnitude improvement. Our work paves the way toward the low-cost and chip-integrated comb spectroscopy and optical frequency standard.

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News release in Chinese:

我校郭光灿院士团队在微腔光学频率梳的研究方面取得重要进展。该团队董春华教授及合作者邹长铃等人提出一种普适的微腔色散调控机制，实现了光频梳中心频率和重复频率的实时独立调控，并应用于光学波长的精密测量，将波长的测量精度提升到kHz量级。相关研究成果1月12日发表在Nature Communications上。

近年来，基于光学微腔的孤子微梳在精密光谱学、光钟、微波光子学、天文学等领域引起了极大的研究兴趣。然而，由于环境和激光噪声以及微腔中额外非线性效应的影响，孤子微梳的稳定性受到了很大的限制，这成为微光梳在实际应用中的一个主要障碍。在之前的工作中，科学家们通过控制材料的折射率或者微腔的几何尺寸以实现实时反馈，从而稳定并调控光频梳，这种方法会引起微腔内所有共振模式同时近乎均匀的变化，缺乏独立调控梳齿频率和重复频率的能力，这大大限制了微光梳在精密光谱、微波光子、光学测距等实际场景中的应用。

针对这一难题，研究团队提出了一种新的物理机制实现了对于光频梳中心频率和重复频率的独立实时调控。通过引入两种不同的微腔色散调控手段，该团队能够对微腔不同阶次的色散进行独立控制，从而实现光频梳不同梳齿频率的全部控制。这种色散调控机制对于目前广泛研究的氮化硅、铌酸锂等不同的集成光子平台都是普适的。

在实验中，该团队利用泵浦激光和辅助激光分别独立控制微腔不同阶次的空间模式实现了泵浦模式频率的自适应稳定和频梳重复频率的独立调控。基于该光频梳，研究团队演示了对于任意梳齿频率的快速、可编程的调控，并将其应用于波长的精密测量中，展示了具有kHz量级测量精度和多波长同时测量能力的波长计。相比于之前的研究成果，研究团队实现的测量精度达到了三个量级的提高。本研究成果所展示的可重构的孤子微梳为实现低成本、芯片集成的光学频率标准奠定了基础，将在精密测量、光钟、光谱学及通信等领域得到应用。

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Just posting a list of the things that a well known weibo account user is predicting for this year of Rabbit. Let's just say his list is quite aggressive. Let me know what you think

第一，半导体生产线实现28nm自主可控，从此中国在汽车芯片、工业芯片、家电芯片、显示器芯片设计与制造实现自由，也就是中国大多数芯片制造进入自主可控范围。是不是这样大家可以等年底看，据说国产DUV光刻机估计可以了。

第二，H20首飞，进度赶得上2025首批入列。那差不多和003到时一个进度了，从此中国的天空更加严密。而003铁定开始海试，希望到时可以看到拆棚后的雄姿！

第三，J20装上涡扇15版本开始出现在大家面前；J35装备新中推版本也可能开始试飞、或者晚一年飞。而装备涡扇20的运20B正式入列。
我们也可以坐上中国自己的C919大飞机了。

第四，中国风电年新增装机容量破1亿千瓦，太阳能光伏装机容量破5千万千瓦，全年中国新增装机容量可能突破2亿千瓦。中国发电量增速超过去年。

第五，中国的汽车出口破400万辆，成为全球第一大汽车出口国家。中国新能源车达到900万辆以上，占比在40%以上。乐观的话，可能可以达到千万辆新能源车规模。国产品牌车份额可能年底会到达60%。韩、法、美三类油车品牌大溃败。

第六，中国手机市场比去年恢复，消费半导体继续存在供过于求，但是汽车半导体供应依然紧张。

第七，中国在医药上有较大的进步，尤其在小分子药和新技术疫苗技术方面。

第八，中国版本的星链可能开始试验，拼工业产能，中国从来不会落后；就是中国移动网络太好，需求不足，规模估计会比较小 。

第九，中国LNG造船份额突破40%，中国造船整体份额稳定在50%以上。055第二批开始下水，076开始制造，中国的造船领先加大了。

第十，中国工业增速超过全球，制造业增加值占全球1/3以上，年底中国1/3，欧美日韩2/5，其他国家约1/5。日韩继续贸易逆差，进入难受的一年，美国经济出现衰退。

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tphuang said:

Just posting a list of the things that a well known weibo account user is predicting for this year of Rabbit. Let's just say his list is quite aggressive. Let me know what you think

https://twitter.com/i/web/status/1616984638190194688

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I've got several comments and questions:

H20首飞，进度赶得上2025首批入列。

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It would be wild if that can be achieved. The largest plane that China has ever build so far, i.e. the Y-20, took around 3.5 years from first flight to introduction into the PLAAF. This is especially when the H-20 is China's first ever venture into a VLO flying-wing airframe.

J35装备新中推版本也可能开始试飞、或者晚一年飞。

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Does the "new mid-thrust (engine)" refers to WS-19?

第四，中国风电年新增装机容量破1亿千瓦，太阳能光伏装机容量破5千万千瓦，全年中国新增装机容量可能突破2亿千瓦。中国发电量增速超过去年。

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Any new expectations from China's nuclear power sector? Especially regarding China's newer 3rd and advanced 4th-generation fission reactors?

第五，中国的汽车出口破400万辆，成为全球第一大汽车出口国家。中国新能源车达到900万辆以上，占比在40%以上。乐观的话，可能可以达到千万辆新能源车规模。国产品牌车份额可能年底会到达60%。韩、法、美三类油车品牌大溃败。

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I'm concerned that with the alarms currently ringing in the EU regarding China's EV advances across the continent, perhaps the Brussels could get agitated enough that they become protectionistic and enact restrictions and policies that would impact Chinese EV's presence there. Need to be alert on this one.

076开始制造

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There are neither mentions nor visible signs of any 2nd batch 075 LHDs undergoing construction as of current, despite 5 ships were supposedly planned. Could it be possible that the PLAN has decided to skip the remaining members of the 075, and continue the LHD line with 076 instead? This is especially with the recent hint by Jiangnan about the possible imminent construction of the 076s.

Or that they could be building 076s at Jiangnan, while at the same time, building the remaining 075s at Hudong-Zhonghua? However, if 076 is meant as a direct sucessor to the 075, this doesn't make much sense IMO...

第十，中国工业增速超过全球，制造业增加值占全球1/3以上，年底中国1/3，欧美日韩2/5，其他国家约1/5。日韩继续贸易逆差，进入难受的一年，美国经济出现衰退。

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The West can go right ahead and decouple themselves from the rest of the world if they keep on bringing up the "decoupling from China" BS.