Temporal dissipative solitons have been widely studied in optical systems, which exhibit various localized structures and rich dynamics, and have shown great potential in applications including optical encoding and sensing. Yet, most of the soliton states, as well as the switching dynamics amongst, were fractionally captured or via self-evolution of the system, lacking of control on the soliton motion. While soliton motion control has been widely investigated in coherently seeded optical cavities, such as microresonator-based dissipative solitons, its implementation in decoherently seeded systems, typically the soliton mode-locked lasers, remains an outstanding challenge. Here, we report the universal dynamics and deterministic motion control of temporal dissipative solitons in a mode-locked fibre laser by introducing a scanned spectral filtering effect. We investigate rich switching dynamics corresponding to both the assembly and the disassembly of solitons, revealing a complete and reversible motion from chaotic states to soliton and soliton-molecule states. Significant hysteresis has been recognized in between the redshift and blueshift scan of the motorized optical filter, unveiling the nature of having state bifurcations in dissipative and nonlinear systems. The active soliton motion control enabled by filter scanning highlights the potential prospects of encoding and sensing using soliton molecules.

An ultrasound wave is a kind of acoustic signal with a frequency greater than 20 kHz, which is widely used in diverse fields such as medical imaging diagnosis, nondestructive testing and resource exploration. A variety of ultrasound sensors have been developed for ultrasound detection. Particularly for photoacoustic imaging, specialized ultrasound sensors with high sensitivity, small size, and broad bandwidth are needed. However, achieving such sensor performance still poses a great challenge to the current state-of-the-art in ultrasound sensor technology. A recent work published in Opto-Electronic Advances (DOI: 10.29026/oea.2022.200076) proposes a microfiber-based ultrasound sensor that breaks the limitations of existing ultrasound sensors. Benefiting from the large evanescent field characteristic of microfiber, combined with the coherent detection technology, the proposed sensor realized highly sensitive ultrasound detection and demonstrated excellent performance in high-resolution photoacoustic imaging. The highly sensitive and miniaturized microfiber ultrasound sensor provides a competitive alternative for various applications, such as endoscopic photoacoustic imaging of the intestinal tract and blood vessels in animals.

离轴四反系统是顺应多光合一机载观瞄系统未来发展的光机核心部件。该类型系统容易受到视场外部强杂散光的影响，系统杂散光的点源透射率（PST）一般要求不大于10⁻⁴量级，因此，对系统PST进行全方位扫描计算是分析和抑制其杂散光的关键。针对系统的非对称性，将PST作为随杂散光入射空间水平角和垂直角变化的二维函数，用以评价外部杂散光的影响，同时建立了水平角、垂直角与光机建模所需绕坐标轴旋转的过程量的对应转换关系，编制了仿真控制程序，通过调用LightTools软件实现杂散光的自动追迹和PST的二维扫描计算。对多光合一离轴四反系统，计算了整个入射半球空间内、所有方向的杂散光对应的PST分布情况，从而筛选出对机载观瞄应用影响较大的三路杂散光，寻找到其传输的路径和关键表面。基于此，设计了内部遮光罩和挡光环，优化系统内部的杂散光陷阱结构，使得系统的PST峰值由原来10⁻¹量级降低至10⁻⁴量级，在规避角范围以外小于10⁻⁷，可满足机载光电观瞄系统的使用要求。为离轴四反系统杂散光分析及抑制提供了依据。

A novel bidirectional remotely controlled device for static and dynamic compression/decompression using diamond anvil cells (DACs) has been developed that can control pressure in an accurate and consistent manner. Electromechanical piezoelectric actuators are applied to a conventional DAC, allowing applications under a variety of pressure conditions. Using this static and dynamic DAC (s-dDAC), it is possible to addresses the poorly studied experimental regime lying between purely static and purely dynamic studies. The s-dDAC, driven by three piezoelectric actuators, can be combined with a time-resolved spectral measurement system and high-speed imaging device to study the structural changes, chemical reactions, and properties of materials under extreme conditions. The maximum compression/decompression rate or pressure range highly depends on the culet size of the anvil, and a higher compression rate and wider pressure range can be realized in a DAC with smaller anvil culet. With our s-dDAC, we have been able to achieve the highest compression rate to date with a 300 μm culet anvil: 48 TPa/s. An overview of a variety of experimental measurements possible with our device is presented.

We experimentally demonstrated a type of tunable and switchable harmonic h-shaped pulse generation in a thulium-doped fiber (TDF) laser passively mode locked by using an ultralong nonlinear optical loop mirror. The total cavity length was ～3.03 km, the longest ever built for a TDF laser to our best knowledge, which resulted in an ultralarge anomalous dispersion over 200 ps2 around the emission wavelength. The produced h-shaped pulse can operate either in a fundamental or in a high-order harmonic mode-locking (HML) state depending on pump power and intra-cavity polarization state (PS). The pulse duration, no matter of the operation state, was tunable with pump power. However, pulse breaking and self-organizing occurred, resulting in high-order HML, when the pump power increased above a threshold. At a fixed pump power, the order of HML was switchable from one to another by manipulating the PS. Switching from the 8th up to the 48th order of HML was achieved with a fixed pump power of ～4.15 W. Our results revealed the detailed evolution and switching characteristics of the HML and individual pulse envelope with respect to both the pump power and PS. We have also discussed in detail the mechanisms of both the h-shaped pulse generation and the switching of its HML. This contribution would be helpful for further in-depth study on the underlying dynamics of long-duration particular-envelope pulses with ultralarge anomalous dispersion and ultralong roundtrip time.