Maximum Output Signal Research Articles

Integrated erbium-doped waveguide amplifier on lithium niobate on insulator

The erbium-doped lithium niobate on insulator (Er:LNOI) has garnered significant attention as it combines outstanding gain property with integration capabilities, making it a promising solution for active devices on the versatile LNOI platform. This also paves a way for the development of appealing erbium-doped waveguide amplifiers. Here, we demonstrate an efficient integrated Er:LNOI micro-waveguide amplifier directly compatible with the lens fiber. In a 5.6-cm-long Er:LNOI micro-waveguide, we demonstrate a maximum internal net gain of 18.8 dB for 1531-nm signal light with 1460-nm pumping. Moreover, the maximum output signal power surpasses 20 mW, thereby confirming the practicality of the Er:LNOI micro-waveguide amplifier.

Brightness enhancement on random-distributed-feedback Raman fiber lasers pumped by multimode diodes

Abstract The power scaling on short wavelength (SW) fiber lasers operating around 1 μm are in significant demand for applications in energy, environment and industry. The challenge for performance scalability of high-power SW lasers based on rare-earth-doped fiber primarily lies in the physical limitations, including reabsorption, amplified spontaneous emission and parasitic laser oscillation. Here, we demonstrate an all-fiberized, purely passive SW (1018 nm) random-distributed-feedback Raman fiber laser (RRFL) to validate the capability of achieving high-power output at SWs based on multimode laser diodes (LDs) direct pumping. Directly pumped by multimode LDs, the high-brightness RRFL delivers over 656 W, with an electro-optical efficiency of 20% relative to the power. The slope efficiency is 94%. The beam quality M2 factor is 2.9 (which is ~20 times that of the pump) at the maximum output signal power, achieving the highest brightness enhancement of 14.9 in RRFLs. To the best of our knowledge, this achievement also represents the highest power record of RRFLs utilizing multimode diodes for direct pumping. This work may not only provide a new insight into the realization of high-power, high-brightness RRFLs but also is a promising contender in the power scaling of SWs below 1 μm.

Active disturbance rejection control: an application to continuous microalgae photobioreactors

AbstractBACKGROUNDMathematical modelling is a widely employed approach for investigating the growth behaviour of microalgae. As a result, the development of model‐based controllers to regulate process variables has garnered increasing attention. However, despite the significant efforts invested in this area, control performance can be adversely affected by unmodelled dynamics and disturbances.RESULTSTwo active disturbance rejection controllers (ADRC) were designed to enable robust tracking of biomass concentration in continuous microalgae photobioreactors, with reduced reliance on the mathematical model of the system. The controllers were tuned to achieve a nonovershoot response and minimize settling time based on the culture's characteristics. Simulations were performed using optimal setpoints specific to each model. The results showcased a maximum output signal deviation of ±2.2%, ±7.8% and ± 7.62% for the Dunaliella tertiolecta, Isochrysis affinis galbana and Chlorella vulgaris models, respectively, regardless of the presence of simulated disturbances.CONCLUSIONSThe findings of this study significantly contribute to the advancement of the field of sustainable microalgae production. By introducing less dependent model‐based controllers, this research enhances the feasibility of implementing robust control strategies. These controllers require only knowledge of the equation system's order and the control gain function, simplifying the design process. This approach effectively addresses control performance degradation arising from unmodelled dynamics and disturbances. The ability to maintain desired process variables through ADRC controllers not only ensures improved control performance, but also supports the cultivation of specific microalgal species, when an accurate model is not available, thus promoting the overall progress and viability of microalgae biomass production. © 2023 Society of Chemical Industry.

Backward pumped distributed Raman amplifier: enhanced gain

The backward Raman amplifier (RA) can considered as one of the best solutions for optical communication, especially in Wavelength Division Multiplexing technology. They reduce the nonlinear effects, have low noise figure and a wide frequency range. The work in this paper aims to reduce the attenuation of optical signal due to its propagation optical fiber and increase both amplifier gain and output signal power. Two backward Raman models are proposed. Proposal one model consists of two cascaded RAs and the other (proposal two) consists of three cascaded RAs. Three backward pump power levels 200, 400, and 600 mW are used to simulate the models with the three types of fibers: single-mode fiber, Truewave, and Freelight, at an amplifier length of 100 km. Proposal two achieves a maximum gain of 31 dB at 600 mW pump power 600 mW using Truewave optical fiber, with 27.7 dBm maximum output signal power. This proposal is evaluated showing 11.15% gain enhancement and 200 mW saved power when compared to previously published work.

Stress analysis of circular membrane-type MEMS microphones with piezoelectric read-out

In this study, the impact of residual tensile stress on a membrane-type piezoelectric MEMS (Micro Electromechanical Systems) microphone is investigated both theoretically by FEM (finite element method) simulations and experimentally by stress measurements, by manufacturing devices and by recording the acoustic performance. Based on these findings, a design is proposed composing of segmented electrodes which are arranged close to the silicon frame as well as on the inner part of the membrane. The MEMS microphone features an aluminum nitride layer which allows a piezoelectric read-out, and multiple metal bottom and top electrodes distributed radially and azimuthally. FEM simulations were done over a large range of different layer thicknesses, membrane radii, and tensile stress levels, which indicate the existence of a sweet-spot when targeting a maximum output signal. The data showed, that thicker membranes perform better under tensile stress than thinner membranes. Furthermore, a relation between output signal and residual stress level was established, which showed that the FEM predictions agree well with the measurement results of piezoelectric microphones. • Thicker MEMS membranes preferred over thinner counterparts when tensely pre-stressed • Finite element analyses revealed sweet spot for maximizing piezoelectric output • Design propositions for stressed closed membranes without stress relaxing measures • Microphone measurements and finite element methods results agree well

Spin polarization characteristics of hybrid optically pumped comagnetometers with different density ratios.

We investigate the effects of the density ratio of K-Rb hybrid cells on the alkali metal-noble gas comagnetometers. Bloch equations simplified with the density ratio and average-pumping-rate model are presented for numerical simulation, which simplifies equations of complete hybrid spin ensemble and problem of polarization gradient. The spin polarizations of electron and nucleon, total electronic relaxation rates, and the spin-exchange efficiencies are measured with cells of different density ratios. The results are in good agreement with our equivalent model. Based on our theoretical analysis, the K-Rb-21Ne comagnetometer achieves maximum output signal by optimizing the combination of density ratio and optical power density. The density ratio is critical to the homogeneity of spin polarization and efficiency of hyperpolarization. The method in this work finds a way to optimize the sensitivity of comagnetometers, which is significant for angular-rotation sensors and new physics research.

A Novel Prototype Biosensor Array Electrode System for Detecting the Bacterial Pathogen Salmonella typhimurium.

Salmonellosis caused by Salmonella sp. has long been reported all over the world. Despite the availability of various diagnostic methods, easy and effective detection systems are still required. This report describes a dialysis membrane electrode interface disc with immobilized specific antibodies to capture antigenic Salmonella cells. The interaction of a specific Salmonella antigen with a mouse anti-Salmonella monoclonal antibody complexed to rabbit anti-mouse secondary antibody conjugated with HRP and the substrate o-aminophenol resulted in a response signal output current measured using two electrode systems (cadmium reference electrode and glassy carbon working electrode) and an agilent HP34401A 6.5 digital multimeter without a potentiostat or applied potential input. A maximum response signal output current was recorded for various concentrations of Salmonella viz., 3, 30, 300, 3000, 30,000 and 300,000 cells. The biosensor has a detection limit of three cells, which is very sensitive when compared with other detection sensors. Little non-specific response was observed using Streptococcus, Vibrio, and Pseudomonas sp. The maximum response signal output current for a dialysis membrane electrode interface disc was greater than that for gelatin, collagen, and agarose. The device and technique have a range of biological applications. This novel detection system has great potential for future development and application in surveillance for microbial pathogens.

Kinetics of a new porcine taste-bud tissue biosensor for the detection of umami substances and their synergistic effect

Umami substances are nutrients to humans, and their synergistic effect is associated with food acceptance. In this study, a new biosensor was developed to detect umami substances, their synergistic effect, and detection kinetics. Porcine taste-bud tissues were used as the sensing element, and the umami substance signals were characterized using an electrochemical workstation. The responses of taste-bud tissue sensors to monosodium L-glutamate (MSG) were compared based on different tongue sites. The interaction law between MSG and receptors in the taste-bud tissues of the three sensors conforms to enzymatic-reaction kinetics, where rectangular hyperbola curves in the Michaelis–Menten equation were followed with fitting coefficients (>0.91). However, the taste-bud sensors respond differently to MSG stimuli, with those based on a tip and mediolateral tongue, producing the lowest detection limit of 10−16 mol/L. The number of receptors required for a single cell to achieve maximum output signal is 3.68, 30.42, and 7.27, respectively. Moreover, the taste-bud tissue sensors identified the synergistic effect of umami substances. In addition, they were sensitive to umami variations in soy sauce and mandarin fish. The developed porcine taste-bud tissue biosensor revealed the interaction law between umami substances and receptors, providing a new idea for umami evaluation.

Rational Design and Characterization of Nitric Oxide Biosensors in E. coli Nissle 1917 and Mini SimCells.

Nitric oxide (NO) is an important disease biomarker found in many chronic inflammatory diseases and cancers. A well-characterized nitric sensing system is useful to aid the rapid development of bacteria therapy and synthetic biology. In this work, we engineered a set of NO-responsive biosensors based on the PnorV promoter and its NorR regulator in the norRVW operon; the circuits were characterized and optimized in probiotic Escherichia coli Nissle 1917 and mini SimCells (minicells containing designed gene circuits for specific tasks). Interestingly, the expression level of NorR displayed an inverse correlation to the PnorV promoter activation, as a strong expression of the NorR regulator resulted in a low amplitude of NO-inducible gene expression. This could be explained by a competitive binding mechanism where the activated and inactivated NorR competitively bind to the same site on the PnorV promoter. To overcome such issues, the NO induction performance was further improved by making a positive feedback loop that fine-tuned the level of NorR. In addition, by examining two integration host factor (IHF) binding sites of the PnorV promoter, we demonstrated that the deletion of the second IHF site increased the maximum signal output by 25% (500 μM DETA/NO) with no notable increase in the basal expression level. The optimized NO-sensing gene circuit in anucleate mini SimCells exhibited increased robustness against external fluctuation in medium composition. The NO detection limit of the optimized gene circuit pPnorVβ was also improved from 25.6 to 1.3 nM in mini SimCells. Moreover, lyophilized mini SimCells can maintain function for over 2 months. Hence, SimCell-based NO biosensors could be used as safe sensor chassis for synthetic biology.

Development of a Wireless Telemetry Sensor Device to Measure Load and Deformation in Orthopaedic Applications.

Due to sensor size and supporting circuitry, in-vivo load and deformation measurements are currently restricted to applications within larger orthopaedic implants. The objective of this study is to repurpose a commercially available low-power, miniature, wireless, telemetric, tire-pressure sensor (FXTH87) to measure load and deformation for future use in orthopaedic and biomedical applications. The capacitive transducer membrane was modified, and compressive deformation was applied to the transducer to determine the sensor signal value and the internal resistive force. The sensor package was embedded within a deformable enclosure to illustrate potential applications of the sensor for monitoring load. To reach the maximum output signal value, sensors required compressive deformation of 350 ± 24 µm. The output signal value of the sensor was an effective predictor of the applied load on a calibrated plastic strain member, over a range of 35 N. The FXTH87 sensor can effectively sense and transmit load-induced deformations. The sensor does not have a limit on loads it can measure, as long as deformation resulting from the applied load does not exceed 350 µm. The proposed device presents a sensitive and precise means to monitor deformation and load within small-scale, deformable enclosures.

Dual-mode and two-signal-wavelength femtosecond optical parametric oscillator based on LiB3O5.

We demonstrate a tunable femtosecond dual-beam-mode (cylindrical vector beam [CVB] and Gaussian beam [GB]), dual-signal-wavelength optical parametric oscillator based on a temperature-tuned lithium triborate crystal, synchronously pumped by a frequency-doubled mode-locked Yb-doped fiber laser. When fixing the CVB wavelength at 780 nm, the central wavelength of the GB signal could be continuously tuned from 664 to 722 nm. The maximum total signal output power is 515 mW at a 4 W pump with dual-wavelength operation (664 and 780 nm). All the measured signal pulse durations are around 150 fs. Moreover, sum-frequency-generation with Gaussian mode tuning from 548 to 588 nm is obtained, with the maximum power of 52 mW at 548 nm. Thanks to the dual-channel configuration, the wavelengths of a CVB and GB can be tuned independently. Such a flexible and versatile configuration makes it a practical tool for many applications such as high-resolution microscopy and high-capacity optical communication.

Geosynchronous Spaceborne-Airborne Bistatic Moving Target Indication System: Performance Analysis and Configuration Design

Geosynchronous spaceborne-airborne bistatic synthetic aperture radar (GEO SA-BSAR), consisting of GEO transmitter and airborne receiver, has stable coverage for a long time and benefits moving target detection. However, the performance of GEO SA-BSAR moving target indication (MTI) system varies widely between bistatic configurations. The traditional configuration design for GEO SA-BSAR system only considers the imaging performance, which may cause the poor MTI performance. In this paper, we propose a bistatic configuration design method to jointly optimize the MTI and SAR imaging performance for GEO SA-BSAR MTI system. The relationship between the MTI performance and bistatic configuration parameters is derived analytically and analyzed based on the maximum output signal to clutter and noise ratio (SCNR) criterion. Then, the MTI performance and SAR imaging performance are jointly considered to model the configuration design problem as a multi-objective optimization problem under the constrained condition. Finally, the optimal configuration for GEO SA-BSAR MTI system is given.

Configurations of Pump Injection and Reinjection for Improved Amplification Efficiency of Turbo Cladding Pumped MC-EDFA

Configurations of cladding pumped MC-EDFA with pump recycling have been researched to improve optical amplification efficiency. The difference between the four researched configurations is the pump injection and re-injection method. The optical amplification performance was compared experimentally by evaluating the optical gain, noise figure, and the maximum output signal power. The results show the spatial injection and the fiber re-injection with spatial splitting configuration improved the pump recycling efficiency the most, and the configuration offered an additional 3.5 dB of optical gain and boosted the maximum output signal power by 4.0 dB compared to the standard cladding pumping without pump recycling. The improvement in the optical gain due to the pump recycling was constant at 1.0 dB in the fixed experimental set-up even if the input optical signal power was changed. The effect of the spatial intensity distribution widening due to the fiber pump combiner is considered to be effective in improving the pump recycling efficiency. An additional 0.2 dB improvement (1.2 dB in total) in the optical gain was achieved by modifying the free-space lens optics design of the spatial pump splitter.

Development of High-Performance Whole Cell Biosensors Aided by Statistical Modeling.

Whole cell biosensors are genetic systems that link the presence of a chemical, or other stimulus, to a user-defined gene expression output for applications in sensing and control. However, the gene expression level of biosensor regulatory components required for optimal performance is nonintuitive, and classical iterative approaches do not efficiently explore multidimensional experimental space. To overcome these challenges, we used a design of experiments (DoE) methodology to efficiently map gene expression levels and provide biosensors with enhanced performance. This methodology was applied to two biosensors that respond to catabolic breakdown products of lignin biomass, protocatechuic acid and ferulic acid. Utilizing DoE we systematically modified biosensor dose–response behavior by increasing the maximum signal output (up to 30-fold increase), improving dynamic range (>500-fold), expanding the sensing range (∼4-orders of magnitude), increasing sensitivity (by >1500-fold), and modulated the slope of the curve to afford biosensors designs with both digital and analogue dose–response behavior. This DoE method shows promise for the optimization of regulatory systems and metabolic pathways constructed from novel, poorly characterized parts.

Generation of coupled orbital angular momentum modes from an optical vortex parametric laser source.

We report on the generation of flower (wheel) modes, which manifest coupled orbital angular momentum (OAM) modes, from a vortex pumped optical parametric oscillator simply by employing a pump source with a short temporal coherence time. This vortex oscillator was also developed to generate a further higher-order vortex signal output with ℓs=2-4 by replacement of the pump source with a longer coherence time. The signal and idler outputs were tuned within wavelength ranges of 745-955 nm and 1200-1855 nm, respectively. The maximum signal output energy of 1.2 mJ was measured with an optical efficiency of 15.6%.

515 nm pumped femtosecond optical parametric oscillator at 755 MHz based on BiB3O6

We report a high-power femtosecond optical parametric oscillator (OPO) based on BiB3O6 crystal with a repetition rate of 755 MHz, which is 10 times that of the pump laser. With 3.75 W pump power from a 90 fs frequency-doubled mode-locked Yb:KGW oscillator, the OPO can provide signal pulses tunable over a spectral range from 693 to 1000 nm and idler pulses tunable from 1100 to 2000 nm. The maximum signal output power is 1.34 W centered at 746 nm and the corresponding idler output power is 0.408 W at 1663 nm. Laser pulse as short as 67 fs is obtained at the central wavelength of 722 nm. This work is promising for a variety of applications in optical communications and pump-probe spectroscopy.

Study on Bombykol Receptor Self-Assembly and Universality of G Protein Cellular Signal Amplification System.

The G protein cascade amplification system couples with several receptors to sense/amplify the cellular signal, implying universal application. In order to explore whether GPCRs can trigger G protein signal amplification in tissues/cells from different species, bombykol receptor was isolated and purified from antennas of male Bombyx mori, which subsequently self-assembled on the cell membrane in rat taste buds/rat vomeronasa/catfish tentacles/taste bud tissues of rabbits/pig/cattle in those lacking endogenous bombykol receptor, followed by immobilization between two sheets of nucleopore membranes fixed by sodium alginate-starch gel, forming the sandwich-type sensing membrane, which in turn was immobilized on the glass-carbon electrode. Thus, bombykol receptor sensors were established with different tissues. The response current of bombykol receptor sensor toward bombykol was measured with an electrochemical workstation. Every bombykol receptor sensor could sense bombykol based on enzyme-substrate kinetics. The double reciprocal plot and the activation constant values of bombykol receptor sensors assembled with rat taste buds, rat vomeronasa, catfish tentacles, rabbit taste buds, pig taste buds, and cattle taste buds were calculated. Approximately 2-3 receptors could trigger the G protein cascade amplification system and achieve the maximum signal output. Moreover, the detection lower limit indicated that the bombykol receptor self-assembled on the cell membranes of different tissues that transmitted and amplified the bombykol signal with hypersensitivity. Also, cattle taste bud tissues served as an ideal system for heterogeneous GPCRs self-assembly and signal sensing/amplification. This sensing technique and method had promising potential in studies of biological pest control, sex pheromone detection, and receptor structure and function.

330-500 GHz Graphene-Based Single-Stage High-Order Subharmonic Mixer

In this work, a graphene-based single-stage high-order subharmonic mixer is presented. The device is able to up- and downconvert a signal in the 330-500 GHz frequency range, using a local oscillator signal with frequency located in the 26-40 GHz band. It exploits the strong nonlinear electromagnetic behavior exhibited by macroscopic graphene sheets when they are exposed to an incident electromagnetic wave to generate the output signal as a mixing product between the input signal and a high-order harmonic component of the local oscillator, which is internally generated without requiring additional circuitry. A prototype was implemented and its performance was experimentally characterized considering several different local oscillator multiplication orders. The maximum measured downconversion gain is around -50 dB, whereas the maximum output signal reached when working as upconverter is -43 dBm at 340 GHz and -63 dBm at 480 GHz. These values are good enough to be used in practical short-range applications. Furthermore, the measurement results are in good agreement with the theoretical predictions about graphene behavior.

Efficient intra-cavity continuous-wave periodically poled lithium niobate-doped MgO optical parametric oscillator with compact V-type cavity

A compact efficient intra-cavity singly resonant optical parametric oscillator (OPO) based on periodically poled lithium niobate-doped MgO (MgO:PPLN) was investigated. A concave–concave fundamental cavity was used for focusing the fundamental beam waist on MgO:PPLN crystal, which enables more compact setup and less insertion loss than traditional insertion of a focusing lens. Two V-type OPO cavities with single and double outputs were used for comparison with idler light outputting from one and both end mirrors, respectively. The results show that the double outputs configuration achieved higher output power for its advantage of reducing the reversed OPO process and diffraction loss of the idler light. Under an incident pump power of 12.4 W, a maximum signal output power of 2.89 W at 1549 nm and total idler output power of 1.44 W at 3394 nm were obtained with a total conversion efficiency up to 34.9%.

Best candidate integrated technology for low‐noise, high‐speed, and wide bandwidth‐based transimpedance amplifiers in optical computing systems and optical fiber applications

SummaryThis paper presents the best candidate integrated technology for achieving low‐noise, high‐speed, and wide bandwidth transimpedance amplifiers in optical computing and communication systems. Different complementary metal oxide semiconductor (CMOS) technology sizes are employed in addition to high electron mobility transistor (HEMT), bipolar CMOS (BiCMOS), and gallium arsenide technologies‐based transimpedance amplifiers to achieve high‐speed capability with low noise. These different technologies are applied on two proposed models to test the performance parameters. Maximum output signal voltage, maximum RF power spectrum, received output power, maximum Q‐factor, and minimum bit error rate are the tradeoff parameters for two proposed models at high transmission bit rates up to 400 Gb/s. It is observed that 600‐nm CMOS technology has presented the best candidate to deal with high transmission bit rates because of its superior performances in either the first proposed model or the second proposed model compared with other technologies under study. Figure of merit is applied on two proposed models and previous works to show the high‐speed performance operation of transimpedance amplifiers in our proposed models. The signal is tested before and after transimpedance amplifiers in different technologies.