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An ultrathin-film microring laser was fabricated using inkjet printing and a simple lift-off technique. Whispering-gallery-mode lasing was observed under optically pumped conditions in the film. The freestanding laser can be transferred to arbitrary surfaces for multifunctional applications, such as acoustic and relative humidity sensing. Using the first eigenmode of a membrane vibration, an acoustic sensor with a 0.15 Pa limit of detection was demonstrated via laser bandwidth broadening. A relative humidity sensor with a 1.1% limit of detection via wavelength shifts was demonstrated by placing the device on an optical fiber facet. These cost-effective, transferrable, multifunctional laser sensors will have many additional applications.

Chaotic cryptography as an important means for digital image encryption has become a great cryptographic project in the current information age. As a novel microcavity laser, a random laser (RL) has a natural advantage for a chaotic system, relying on its spectral randomness. Nevertheless, this encrypted image generally suffers from outline exposition when an unsuitable key from a single RL spectrum is employed. Herein, to realize reliable dual chaotic encryption, an internally integrated hybrid microcavity in random and whispering-gallery-mode (WGM) is reported. Within this coupled microcavity, the rhodamine-6G-doped inner-wall of the fiber serves as the gain medium and the optical cavities for WGM lasing; an RL mode is enabled by scattered particles and the gain medium (Rh6G). Interestingly, the smooth inner wall of the fiber with a high-quality (

Microlasers hold great promise for the development of photonics and optoelectronics. At present, tunable microcavity lasers, especially regarding in situ dynamic tuning, are still the focus of research. In this study, we combined a 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 (PMN-PT) piezoelectric crystal with a Poly [9,9-dioctylfluorenyl-2,7-diyl] (PFO) microring cavity to realize a high-quality, electrically tunable, whispering-gallery-mode (WGM) laser. The dependence of the laser properties on the diameter of the microrings, including the laser spectrum and quality (Q) value, was investigated. It was found that with an increase in microring diameter, the laser emission redshifted, and the Q value increased. In addition, the device effectively achieved a blueshift under an applied electric field, and the wavelength tuning range was 0.71 nm. This work provides a method for in situ dynamic spectral modulation of microcavity lasers, and is expected to provide inspiration for the application of integrated photonics technology.

Because of its limited light field mode and high Q value, the whispering-gallery-mode (WGM) cavity has been widely studied. In this study, we propose a simple, rapid, low-cost and no-manufacturing technology method that we call the drip-coating method to obtain an irregular cavity with arbitrary boundaries. By using polyvinyl alcohol (PVA) solution doped with rhodamine 6G, the irregular cavity with arbitrary boundaries was drip-coated on a high-reflection mirror, forming a WGM laser. The sample was pumped with a 532 nm pulsed laser, and the single-mode WGM and multi-WGM lasing were obtained. All WGMs are the vertical oscillation modes, which originate from both the total internal reflection of the PVA/air interface and vertical reflection of the PVA/mirror interface. The other boundaries of the cavity were not involved in the reflection and could have any shape. The mechanism of producing single-mode lasing is due to the action of the loss-gain cavity. Multi-WGM lasing is attributed to at least two groups of different WGMs existing in an irregular cavity. This can be confirmed by using a microsphere model and intensity correlation method. These results may provide an alternative for the design of WGM lasers.

Hybrid lead halide perovskites have made great strides in next-generation photovoltaic and optoelectronic devices. Random lasers based on perovskite materials have been intensively investigated, but the miniaturization of perovskite random lasers has not been achieved up to now. Here, we report the fabrication of perovskite random lasers based on perovskite films deposited on the optical fiber facets using a dip-coating method. Under optical pumping conditions, random lasing was observed with minimum threshold energy of 32.3 μJ/cm2 at ~550 nm; also, the lasing threshold decreased with increasing diameter of the optical fiber. The results show that the random lasing emission originates from the scattering between the perovskite crystal grains, and the decreased threshold is attributed to the increased active area of the perovskite film. The directionality of perovskite random lasers indicates that the divergence angle of the laser beam is less than 60°. We also demonstrate that the perovskite random laser on the fiber facet can prevent speckle formation and improve image quality. These results may promote the applications of random lasers in compact sources and integrated optoelectronic devices.

A hybrid membrane is employed as a high-order plasmonic distributed feedback (DFB) cavity to reduce the lasing threshold of polymer lasers. The hybrid membrane consists of an anodic aluminum oxide (AAO) membrane, a 25 nm thick silver layer and a free-standing polymer membrane. The AAO membrane is fabricated by a low-cost, single chemical etching method. Then, a layer of silver with a thickness of 25 nm is sputtered on the surface of the AAO. Subsequently, a polymer membrane is directly attached to the silver-plated AAO membrane, forming an AAO/silver/polymer hybrid membrane. Under optical pumping conditions, low-threshold, three-order DFB lasing is observed. The proposed laser device exhibited a dual-threshold characteristic because of the evolution from amplified spontaneous emission to DFB lasing. And a significant shift from omnidirectional emission to directional emission lasing can be observed while the pump energy density is beyond the second threshold. Furthermore, the plasmonic enhancement sourced from silver corrugation reveals important improvement effects to the DFB lasing of AAO/silver/polymer hybrid membrane for decreasing threshold, narrowing full width at half maximum (FWHM), and an increasing Q factor. This work may promote the design and production of low-cost and large-area high-order plasmonic DFB polymer lasers.

Miniaturized lasing with dynamic manipulation is critical to the performance of compact and versatile photonic devices. However, it is still a challenge to manipulate the whispering gallery mode lasing modes dynamically. Here, we design the quasi-three-dimensional coupled cavity by a micromanipulation technique. The coupled cavity consists of two intersection polymer microfibers. The mode selection mechanism is demonstrated experimentally and theoretically in the coupled microfiber cavity. Dynamic manipulation from multiple modes to single-mode lasing is achieved by controlling the coupling strength, which can be quantitatively controlled by changing the coupling angle or the coupling distance. Our work provides a flexible alternative for the lasing mode modulation in the on-chip photonic integration.

A dual-color plasmonic random laser under single-excitation is achieved in an ultrathin membrane doped with binary quantum dots and gold nanorods. The gold nanorods tune the luminescence lifetime and emission efficiency of quantum dots. Under single excitation, low-threshold random lasing is observed. Green random lasing at 547 nm is 'turned on' and red random lasing at 630 nm is greatly enhanced by the transversal and longitudinal surface plasmon resonance of the gold nanorods, respectively. Speckle-free color imaging is achieved by using the proposed dual-color random laser source. These properties would facilitate the development of random lasers in fields of illumination and imaging.

The elastostatic stiffness performance of a 2PUR-PSR (S: spherical joint; U: universal joint; R: revolute joint; P: prismatic pair) overconstrained parallel mechanism with two rotational and one translational (2R1T) degrees of freedom was studied based on screw theory and strain energy. First, the actuator and constraint wrenches of the mechanism were obtained based on screw theory. Second, by considering the space composite elastic deformation of the rod (including axial tension, and shear, torsional and bending deformation), compact limb stiffness matrixes were obtained in terms of strain energy and Castigliano’s second theorem. Finally, analytic expressions for the overall stiffness matrix of the mechanism and the amplitudes of the actuator and constrained wrenches were obtained based on the virtual-work principle and the balance equation for a moving platform. The relative error between results from the analytical model and the Workbench finite element model is approximately 1.3%, which validates the effectiveness of the proposed elastostatic stiffness model. Unlike traditional stiffness evaluation index, a regional stiffness index was proposed to measure the mechanism’s stiffness performance at various working heights. Using the index, it is possible to determine the optimum stiffness region of a moving platform with known external wrenches.

The color and/or chromaticity controllability of random lasing is a key factor to promote practical applications of random lasers as high luminance sources for speckle-free imaging. Here, white coherent random lasing with tunable chromaticity is obtained by using broadband enhancement Au-Ag nanowires as scatterers and the resonance energy transfer process between different dyes in the capillary microfluidic channel. Red, green and blue random lasers are separately fabricated with low thresholds, benefiting from the plasmonic resonance of the nanogaps and/or nanotips with random distribution and sizes within Au-Ag nanowires and positive optical feedback provided by the capillary wall. A white random laser system is then designed through reorganizing the three random lasers. And, the chromaticity of the white random laser is flexibly tunable by adjusting pump power density. In addition, the white random laser has anisotropic spectra due to the coupling role between the lasers. This characteristic is then utilized to obtain different random lasing with different chromaticity over a broad visible range. The results may provide a basis for applying random laser in the field of high brightness illumination, biomedical imaging, and sensors.

Asymmetric construction of β,β-diaryl substituted glycine bearing two contiguous chiral centers remains a significant challenge. Herein, the application of the para-quinone methides (p-QMs) and Ni(II)- complex of glycine via 1,6-conjugate addition to achieve asymmetric synthesis of β,β-diaryl substituted glycine has been explored successfully. This protocol features operational simplicity, high diastereoselectivity, and recyclable chiral ligand, which provides a versatile approach to the synthesis of highly enantiopure β,β-diaryl substituted glycine.

A dual-wavelength random laser of polymer film is fabricated by a spincoating method, and the dual cavities of step type are prepared on a silica substrate. The random microstructure forms due to the phase separation in the fabrication process, and provides a multiscattering mechanism for random lasing. The wavelength of output emission alters from 450 nm to 467 nm, when the pump spot totally shifts from cavity A to Cavity B. The output intensities can be adjusted by the ratio of illuminate areas on the dual cavities. The design of step cavities provides simple approach of a dual-wavelength random lasing emission, demonstrating potentials for compact laser devices.

A new 2R1T (R: rotation, T: translation) parallel manipulator (PM), called Tex3, is proposed. The Tex3 PM is a 2PUR-PRU PM consisting of 9 joints with 12 DOFs (degrees of freedom), and can be actuated by fixed linear actuators. Mobility analysis shows that it is an RPR-equivalent PM whose finite motion is the product of a rotation (R) followed by a translation (P) and another rotation (R). Inverse position and velocity analyses are discussed. Furthermore, the local transmission index and good transmission workspace are used to evaluate the motion/force transmissibility of the proposed PM. The singularity loci of the proposed PM are obtained according to the motion/force transmissibility, corresponding to the inverse, forward and combined kinematic singularity. The constraint singularity is also discussed. Finally, link parameters are optimized to obtain an improved good transmission workspace. Because of its minimum DOF of joints and fixed linear actuators, the Tex3 PM has good kinematic performance and is suited to the high-speed machining of workpieces with curved surfaces.

An operationally convenient, asymmetric synthesis of chiral trifluoromethyl containing heterocyclic amino acids has been developed via Michael addition reaction of chiral equivalent of Ni(II)-complex of glycine and β-trifluoromethylated-α,β-unsaturated ketones. The simplicity of the experimental procedures and high stereochemical outcome of the presented method render these heterocyclic amino acids readily available for systematic medicinal chemistry studies and de novo peptide design.

The working threshold is an important parameter to assess the performance of cavity-free random lasers. Here, the temporal profile measurement is proposed as an alternative method to determine the thresholds of the surface plasmon based random lasers pumped by ns pulses based on analyzing the delay time (tDelay) and rising time (tR) of the emission signal. The obvious and slight inflection points of the curves of tDelay and tR varying with the pump power density are observed as indicators for the thresholds of random lasing and for the transition of lasing mode, respectively. The proposed method supplies consistent values to those supplied by traditional methods in frequency-domain for the random systems with different gain length. The demonstrated temporal profile approaches are free from the spectrometers and may be as a candidate for measuring the threshold of random lasers in ultrafast optics, nonlinear optics and bio-compatible optoelectronic probes.

Multicolor random lasing has broad potential applications in the fields of imaging, sensing, and optoelectronics. Here, silver nanoflowers (Ag NF) with abundant nanogaps are fabricated by a rapid one-step solution-phase synthesis method and are first proposed as effective broadband plasmonic scatterers to achieve different color random lasing. With abundant nanogaps and spiky tips near the surface and the interparticle coupling effect, Ag NFs greatly enhance the local electromagnetic field and induce broadband plasmonic scattering spectra over the whole visible range. The extremely low working threshold and the high-quality factor for Ag NF-based random lasers are thus demonstrated as 0.24 MW cm−2 and 11,851, respectively. Further, coherent colorful random lasing covering the visible range is realized using the dye molecules oxazine (red), Coumarin 440 (blue), and Coumarin 153 (green), showing high-quality factor of more than 10,000. All these features show that Ag NF are highly efficient scatterers for high-performance coherent random lasing and colorful random lasers.

Continuously tunable polymer lasing was achieved in one-dimensional, two-dimensional, and compound chirped cavities. The chirped cavity was simply fabricated by using interference lithography and spin coating. Two-dimensional and compound chirped cavities were obtained by employing oblique exposure and double exposure, respectively. The tunability range of two-dimensional chirped cavities was much wider than that of one-dimensional chirped cavities, which varied from 557 nm to 582 nm. The interaction between lasing modes was studied in the compound cavity by introducing an additional nanostructure into the two-dimensional chirped cavities. The threshold of the compound chirped cavities changed with the coupling strength between lasing modes. These results may be helpful for designing compact polymer laser sources.

A compound cavity was proposed to achieve both whispering gallery mode (WGM) lasing and random lasing. The WGM-random compound cavity consisted of a random structure with an annular boundary, which was fabricated by a method combining both inkjet printing and metal-assisted chemical etching methods. An ultrathin polymer membrane was attached to the WGM-random compound cavity, forming a polymer laser device. A transformation from WGM lasing to random lasing was observed under optical pumping conditions. The laser performance could be easily tailored by changing the parameter of the WGM-random compound cavity. These results provide a new avenue for the design of integrated light sources for sensing applications.

Low-cost and miniaturized biosensors are key factors leading to the possibility of portable and integrated biomedical system, which play an important role in clinical medicine and life sciences. Random lasers with simple structures provide opportunities for detecting biomolecules. Here, a low-cost biosensors on fiber facet for label-free detecting biomolecules is demonstrated resorting to plasmonic random laser. The random laser is achieved resorting to a random plasmonic scattering structure of Ag nanoparticles and polymer film on fiber facet. Refractive index sensitivity and near-surface sensitivity of the biosensor are systematically studied. Furthermore, the biosensor is used to detect lgG through specific binding to protein A , exhibiting the detecting limit of 0.68 nM. It is believed that this work may promote the applications of plasmonic random laser bio-probe in portable or integrated medical diagnostic platforms, and provide fundamental understanding for the life science.

The operation effectiveness of multi-bar transplanting mechanisms is low, and the specific changing law of the transmission ratio (the curve of the transmission ratio has twice unequal amplitude [TUA] fluctuation.), which is needed in vegetable pot seedling transplanting, is difficult to fulfill using a planetary gear train with noncircular gears and a single-planet carrier. To address this problem, we propose a noncircular gear pair that comprises an incomplete noncircular gear, rack, partial noncircular gear, and elliptical gear. The structural characteristics and the working principle of the TUA gear pair were analyzed. The pitch curve equation of the noncircular TUA gears was derived from the relationship of the angular displacement of the corresponding pitch curves. The influence of central angle α and eccentricity k on the shape of the pitch curve, angular displacement, and transmission ratio of the TUA gear pair was analyzed. The TUA gear pair was applied to a proposed vegetable seedling pickup mechanism (SPM) considering the design requirements. Finally, the feasibility of the new noncircular TUA gear transmission mechanism was verified by an SPM test.

The polarization and threshold of distributed feedback (DFB) polymer lasers were controlled by adjusting the cavity coupling. The cavity of DFB polymer lasers consisted of two gratings, which was fabricated by a two-beam multi-exposure holographic technique. The coupling strength of the cavity modes was tuned by changing the angle between the two gratings. The threshold of the polymer lasers decreased with reducing the coupling strength of the cavity modes. A minimum threshold was observed at the lowest coupling strength. Moreover, the azimuthally polarized output of the polymer lasers was modified by changing the cavity coupling. These results may provide additional perspectives to improve the performance of DFB polymer lasers.

A random laser was achieved in a polymer membrane with silver nanoflowers on a flexible substrate. The strong confinement of the polymer waveguide and the localized field enhancement of silver nanoflowers were essential for the low-threshold random lasing action. The lasing wavelength can be tuned by bending the flexible substrate. The solution phase synthesis of the silver nanoflowers enables easy realization of this type of random lasers. The flexible and high-efficiency random lasers provide favorable factors for the development of imaging and sensing devices.

The amount ofsugarcane stubble left in field is a major contributor to the total sugarcane loss in mechanical harvesting. Thus, reducing stubble height is an effective way to improve sugarcane recovery. The purpose of this study was to investigate how harvester off-track errors affect sugarcane stubble height and stubble loss. In this study, stubbles were sampled after harvesting, off-track errors and stubble weight were measured, and regression methods were used to model their relationships. Results showed an average stubble height as low as 0.16 m could be achieved if the harvester could track the crop row accurately. Based on the analysis of 33 randomly selected cane stools in the field, as the off-track error (the offset of actual harvester position from ideal position) increased from 0 to 1.46 m, the average stubble height increased from 0.13 to 1.41 m, which resulted in the average amount of stubble left in the field increasing from 0.07 to 0.80 kg. The results showed a strong positive correlation between stubble height (R2=0.91) or stubble weight (R2=0.89) and off-track errors. There were whole canes being completely left in the field either being missed or pushed down by the harvester when the off-track error was more than 0.76 m. Results suggest that improving the tracking accuracy during mechanical harvesting could substantially reduce stubble loss, leading to higher feedstock harvesting efficiency when using the existing sugarcane harvester. Keywords: Actual stubble height, Feedstock harvesting efficiency, Off-track error, Stubble loss, Sugarcane harvesting.

Sugarcane stubble damage is affected by various factors related to crop production and harvesting operation. This study aimed at investigating how cane stool density and stubble height affected sugarcane stubble damage in typical Hawaii sugarcane fields. In the study, stubble damage was classified based on the damage length: lightly damaged (damage length 102 mm). The measured stubble damage levels were then plotted against cane stool density and stubble height to study the changes in stubble damage with the changes in these parameters. The results showed that cane stool density (range: 75 to 142 canes m -2 ) had a negative correlation (r 2 = 0.87) and stubble height (range: 0.12 to 0.59 m) had a positive correlation (r 2 = 0.79) with stubble damage level. Specifically, when stubble height increased from 0.12 to 0.59 m, the average damage length increased from 15 to 85 mm. Meanwhile, the percentage of severely damaged stubble increased from 0% to 53%. Understanding the relationship that stubble damage level has with cane stool density and stubble height could provide fundamental information for engineers to improve the design of sugarcane basecutting mechanisms by optimizing basecutter height control, which could lead to reduced harvest-induced damage of sugarcane stubble.

Flexible and effective manipulation of the distributed feedback (DFB) polymer lasers remained a challenge. Herein, the performance of the polymer laser was manipulating by integrating a one-dimension diffraction element into the DFB cavity. Gratings with different periods were employed as the DFB cavity and the diffraction element, respectively. The compound cavity with different gratings was fabricated by using a multi-exposure two-beam interference technique. One-to-many lasing beams were realized in the compound cavity. The azimuth and elevation angles of the laser beam were controlled by adjusting the period of the diffraction element. The threshold of the laser device was affected by the introduction of the diffraction element, which was explained by the coupled-mode theory. The manipulation method was also extended to the case of a two-dimension diffraction element. These features provide flexible control over the performance of the polymer lasers.