Etching of quartz crystals in liquid phase environment:A review

Quartz crystals are the most widely used material in resonant sensors,owing to their excellent piezoelectric and mechanical properties.With the development of portable and wearable devices,higher processing efficiency and geometrical precision are required.Wet etching has been proven to be the most efficient etching method for large-scale production of quartz devices,and many wet etching approaches have been developed over the years.However,until now,there has been no systematic review of quartz crystal etching in liquid phase environments.Therefore,this article provides a comprehensive review of the development of wet etching processes and the achievements of the latest research in thisfield,covering conventional wet etching,additive etching,laser-induced backside wet etching,electrochemical etching,and electrochemical discharge machining.For each technique,a brief overview of its characteristics is provided,associated problems are described,and possible solutions are discussed.This review should provide an essential reference and guidance for the future development of processing strategies for the manufacture of quartz crystal devices.

High-intensity spatial-mode steerable frequency up-converter toward on-chip integration

Integrated photonic devices are essential for on-chip optical communication,optical-electronic systems,and quantum information sciences.To develop a high-fidelity interface between photonics in various frequency domains without disturbing their quantum properties,nonlinear frequency conversion,typically steered with the quadratic(χ2)process,should be considered.Furthermore,another degree of freedom in steering the spatial modes during theχ2 process,with unprecedent mode intensity is proposed here by modulating the lithium niobate(LN)waveguide-based inter-mode quasi-phasematching conditions with both temperature and wavelength parameters.Under high incident light intensities(25 and 27.8 dBm for the pump and the signal lights,respectively),mode conversion at the sum-frequency wavelength with sufficient high output power(−7–8 dBm)among the TM01,TM10,and TM00 modes is realized automatically with characterized broad temperature(ΔT≥8°C)and wavelength windows(Δλ≥1 nm),avoiding the previous efforts in carefully preparing the signal or pump modes.The results prove that high-intensity spatial modes can be prepared at arbitrary transparent wavelength of theχ2 media toward on-chip integration,which facilitates the development of chip-based communication and quantum information systems because spatial correlations can be applied to generate hyperentangled states and provide additional robustness in quantum error correction with the extended Hilbert space.

Passively Q-switched Tm/Ho composite laser

We explored Q-switching mechanism for the newly proposed Tm/Ho composite laser via developing a hybrid resonator for separating the intra-cavity Tm laser modulated by the saturable absorber(SA).With a Cr:ZnSe SA,successful passively Q-switching process with the maximum average output power of 474 mW and the shortest pulse width of 145 ns were obtained at the pulse repetition frequency of 7.14 kHz,where dual wavelength oscillation in both 2090 nm and 2097 nm was observed.This work provides an effective way for a direct laser diode(LD)pumped Q-switched Ho laser,which is compact and accessible.Furthermore,the current SA could be replaced by the 2D materials with broadband saturable absorption such as topological insulators or transition-metal dichalcogenides for seeking novel PQS lasers.

A highly linear stretchable MXene-based biocompatible hydrogel-elastomer hybrid with tissue-level softness

Maintaining low modulus while endowing the wide-range linear stretchability to wearable or implantable devices is crucial for these devices to reduce the mechanical mismatch between the devices and human skin/tissue interfaces.However,improving linear stretchability often results in an increased modulus of stretchable electronic materials,which hinders their conformability in long-term quantifiable monitoring of organs.Herein,we develop a hybrid structure involving interlocking low-modulus porous elastomers(Ecoflex-0030)and MXene-based hydrogels with crosslinking networks of polyvinyl alcohol,sodium alginate,and MXene.This hydrogel–elastomer structure exhibits superior performance compared with previous reports,with a wide linear stretchability strain range from 0 to 1000%and maintaining a low modulus of 6.4 kPa.Moreover,the hydrogel–elastomer hybrids can be utilized as highly sensitive strain sensors with remarkable characteristics,including high sensitivity(gauge factor~3.52),a linear correlation between the resistance and strain(0–200%),rapid response(0.18 s)and recovery times(0.21 s),and excellent electrical reproducibility(1000 loading–unloading cycles).Those electrical and mechanical properties allow the sensor to act as a suitable quantifiable equipment in organ monitoring,human activities detecting,and human–machine interactions.

Electrode materials for brain-machine interface:A review

Brain-machine interface(BMI)is a device that translates neuronal information into commands,which is capable of controlling external software or hardware,such as a computer or robotic arm.In consequence,the electrodes with desirable electrical and mechanical properties for direct interacting between neural tissues and machines serves as the crucial and critical part of BMI technology.Nowadays,the development of material science provides many advanced electrodes for neural stimulating and recording.Particularly,the widespread applications of nanotechnologies have innovatively introduced biocompatible electrode that can have similar characteristics with neural tissue.This paper reviews the existing problems and discusses the latest development of electrode materials for BMI,including conducting polymers,silicon,carbon nanowires,graphene,and hybrid organic-inorganic nanomaterials.In addition,we will inspect at the technical and scientific challenges in the development of neural electrode for a broad application of BMI with focus on the biocompatibility,mechanical mismatch,and electrical performance of electrode materials.

Validation of spectrum method for improving efficiency of continuous-wave ＆ Q-switched Tm-doped yttrium aluminum garnet laser

Tm3＋-doped 2-μm lasers benefit many applications such as atmospheric sensing, medical treatment, and spec- troscopy [1-3]. Therefore, in the past two decades, both continuous-wave （CW） and pulse operations have been widely researched in Tm3＋-doped bulk materials and fibers [4-7].

Practical N-alkylation via homogeneous iridium-catalyzed direct reductive amination

Direct reductive amination(DRA)is one of the most efficient methods for amine synthesis.Herein we report a practical homogeneous DRA procedure utilizing iridium catalysis.Applying simple,readily available and inexpensive PPh_(3)and alike ligands along with iridium at a low loading,aldehydes and ketones reductively coupled with primary and secondary amines to efficiently form structurally and functionally diverse amine products,including a set of drugs and compounds from late-stage manipulation.The reaction conditions were exceptionally mild and additive-free,in which oxygen,moisture,polar protic groups and multiple other functional groups were tolerated.For targeted products,this methodology is especially versatile for offering multiple possible synthetic options.The 10 gram-scale synthesis further demonstrated the potential and promise of this procedure in practical amine synthesis.DFT studies reveal an“outer-sphere”H-addition pathway,in whichπ-πinteractions and H-bonding play important roles.