新型冠状病毒肺炎(Corona Virus Disease 2019, COVID-19)疫情大流行引起全球对此重大突发公共卫生事件的高度关注。新型冠状病毒(SARS-CoV-2)经过多次突变, 出现传染速度加快、免疫逃逸、隐匿性传播等特性, 令防控形势至今仍异常严峻。对患者的早发现、早隔离仍然是目前最有效的防控措施。因此, 迫切需要快速、高灵敏的检测手段来甄别此病毒, 以便及早识别感染者。本文简要介绍了SARS-CoV-2的一般特征, 并针对核酸、抗体、抗原及病原体作为检测靶标的不同检测手段及最新进展进行分类概述; 对一些光学、电学、磁学以及可视化的新型纳米传感器在SARS-CoV-2检测技术上的应用进行了分析。鉴于纳米技术的应用在提高检测灵敏度、特异性以及准确率上具有优势, 本文详细介绍了新型纳米传感器在SARS-CoV-2检测中的研究进展, 包括表面增强拉曼基生物传感器、电化学生物传感器、磁纳米生物传感器以及比色生物传感器等, 并探讨了纳米材料在新型生物传感器构建中的作用和挑战, 为纳米材料研究人员开发各种类型的冠状病毒传感技术提供思路。

We demonstrate an ultra-broadband high temporal contrast infrared laser source based on cascaded optical parametric amplification, hollow-core fiber (HCF) and second harmonic generation processes. In this setup, the spectrum of an approximately 1.8 μm laser pulse has near 1 μm full bandwidth by employing an argon gas-filled HCF. Subsequently, after frequency doubling with cascaded crystals and dispersion compensation by a fused silica wedge pair, 9.6 fs (~3 cycles) and 150 μJ pulses centered at 910 nm with full bandwidth of over 300 nm can be generated. The energy stability of the output laser pulse is excellent with 0.8% (root mean square) over 20 min, and the temporal contrast is >10¹² at –10 ps before the main pulse. The excellent temporal and spatial characteristics and stability make this laser able to be used as a good seed source for ultra-intense and ultrafast laser systems.

Temporal contrast directly affects the interaction between ultraintense and ultrashort pulse lasers with matter. Seed laser sources with broad bandwidth and high temporal contrast are significant for overall temporal contrast enhancement. The technique of cascaded nonlinear processes with optical parametric amplification and second-harmonic generation is demonstrated for high temporal contrast seed source generation. Within 40 ps before the main pulse, the temporal contrast reaches over 10¹¹. The pulse energy and duration of the high-contrast pulse are 112 μJ and 70 fs, respectively. Considering its high beam quality and stability, this laser source can serve as a high-quality seed for Nd:glass-based ultraintense and ultrashort pulse laser facilities.

Infrared femtosecond optical vortices open up many new research fields, such as optical micro–nano manipulation, time-resolved nonlocal spectroscopy in solids, vortex secondary radiation and particle generations. In this article, we demonstrate a femtosecond optical vortex laser system based on a two-stage optical parametric amplifier. In our experiment, 1.45 μm vortex signal pulses with energy of 190 μJ and 1.8 μm vortex idler pulses with energy of 158 μJ have been obtained, and the pulse durations are 51 and 48 fs, respectively. Both the energy fluctuations of the signal and idler pulses are less than 0.5% (root mean square), and the spectral fluctuations are less than 1.5% within 1 hour. This type of highly stable femtosecond optical vortex laser has a wide range of applications for vortex strong-field physics.

近年来，可调谐中红外新波段超强超短激光的出现与迅速发展，开辟了强场物理领域中迄今仍很少探索过的参量空间，为开拓超强超短激光与物质相互作用的新物理、新效应及新应用提供了新机遇。文中总结了中红外超强超短激光近年来的发展趋势与研究方向。针对光参量放大、光参量啁啾脉冲放大、中红外脉冲后压缩以及中红外新型光场调控技术4个研究方向，较全面地分析各自的国内外研究现状，并对未来中红外超强超短激光的发展趋势进行了展望。

The generation of high-peak-power, few-cycle mid-infrared (MIR) pulses using coherent beam combination and nonlinear pulse compression techniques simultaneously is demonstrated. The two pulses, with identical pulse energy of 2.8 mJ and pulse duration of 160 fs, are coherently combined at the input end of a krypton-filled hollow-core fiber (HCF), and then the bandwidth of the combined pulse is broadened to near an optical octave due to strong phase modulations, and the temporal width is compressed into a few-cycle regime. Finally, a 2.7 mJ, 22.9 fs, 20 Hz laser at 4 μm can be obtained, and the pulse peak power is greatly enhanced compared with that of conventional single-channel optical parametric chirped pulse-amplification systems. Furthermore, the peak power generated from this system has the prospect of further scaling up through use of more channels of coherent combination, which can pave a way to generate higher peak power ultra-intense MIR pulses for strong-field physics.

A femtosecond mid-infrared optical vortex laser can be used for high harmonic generation to extend cutoff energy to the kilo-electron-volt range with orbital angular momentum, as well as other secondary radiations. For these, we demonstrate a high-energy femtosecond 4 μm optical vortex laser based on optical parametric chirped pulse amplification (OPCPA) for the first time. The optical vortex seed is generated from a femtosecond 4 μm laser by a silicon spiral phase plate with the topological charge l of 1 before the stretcher. Through using a two-stage collinear OPCPA amplifier, the chirped vortex pulse is amplified to 12.4 mJ with 200 nm full width at half-maximum bandwidth. After compression, the vortex laser pulse with 9.53 mJ, 119 fs can be obtained. Furthermore, the vortex characteristics of the laser beam are investigated and evaluated. This demonstration can scale to generate a higher-peak-power vortex mid-IR laser and pave a new way for high field physics.