Optical Signal Amplification Research Articles

Fiber-optic radio frequency transfer with enhanced frequency stability using fiber Brillouin amplifiers

The frequency stability of long-distance two-way fiber-optic radio frequency (RF) transfer is directly affected by the optical signal-to-noise ratio (OSNR) of optical amplifiers. In this paper, we have proposed a stimulated Brillouin scattering (SBS)-based optical amplification scheme with high OSNR for two-way fiber-optic RF frequency transfer over single mode fibers (SMF). At the remote and local site, the modulated carrier transferred from the opposite was amplified and then frequency upshifted by Brillouin frequency shift (BFS) for pump generation. This approach can avoid the use of additional pump lasers and phase-locked loops for wavelength stabilization of the pump. The pump was injected into the fiber link and counter-propagated with the signal to amplify the modulated carrier. A 2.2 GHz RF signal transfer with the proposed SBS-based optical amplification schemes was demonstrated over a 100 km fiber link. The experimental results illustrated that the OSNR was increased by 35 dB and 32 dB at the local site and the remote site, respectively, compared to the results obtained with erbium-doped fiber amplifiers (EDFA)-based optical amplification. Benefiting from improved OSNR, the frequency stability was increased by more than one order of magnitude below 1000 s averaging time, and the phase noise was reduced to the noise floor below 0.1 Hz offset frequency. The proposed optical signal amplification approach has a potential application for transferring atomic clocks over long-haul fiber links.

Advancing large-scale thin-film PPLN nonlinear photonics with segmented tunable micro-heaters

Thin-film periodically poled lithium niobate (TF-PPLN) devices have recently gained prominence for efficient wavelength conversion processes in both classical and quantum applications. However, the patterning and poling of TF-PPLN devices today are mostly performed at chip scales, presenting a significant bottleneck for future large-scale nonlinear photonic systems that require the integration of multiple nonlinear components with consistent performance and low cost. Here, we take a pivotal step towards this goal by developing a wafer-scale TF-PPLN nonlinear photonic platform, leveraging ultraviolet stepper lithography and an automated poling process. To address the inhomogeneous broadening of the quasi-phase matching (QPM) spectrum induced by film thickness variations across the wafer, we propose and demonstrate segmented thermal optic tuning modules that can precisely adjust and align the QPM peak wavelengths in each section. Using the segmented micro-heaters, we show the successful realignment of inhomogeneously broadened multi-peak QPM spectra with up to 57% enhancement of conversion efficiency. We achieve a high normalized conversion efficiency of 3802% W−1 cm−2 in a 6 mm long PPLN waveguide, recovering 84% of the theoretically predicted efficiency in this device. The advanced fabrication techniques and segmented tuning architectures presented herein pave the way for wafer-scale integration of complex functional nonlinear photonic circuits with applications in quantum information processing, precision sensing and metrology, and low-noise-figure optical signal amplification.

Efficient Fabrication of Plasmonic Nanostructures Using Chloroform‐Mediated Heterogeneous Bonding

AbstractPlasmonic nanostructures (PNs) have transformed nanophotonics by offering control over electromagnetic waves. Although innovative structural designs have demonstrated PNs' potential, significant fabrication challenges, including the precise alignment of heterogeneous materials, remain. Using chloroform and pre‐UV exposure (PUVE) to enhance adhesion at the metal‐dielectric interface (MDI) addresses these challenges. PUVE preserves plasmon resonance in the MDI, ensuring high performance without compromising structural integrity. Through an annealing process, PUVE strengthens van der Waals bonds, ensuring chloroform molecules remain on the Ag surface during chloroform residue removal, allowing: i) stable preservation of the Ag thin film on the PNs during stripping; and ii) the formation of chloroform‐mediated heterogeneous bonding (CMHB) using energy supplied by UV‐nanoimprint lithography (UV‐NIL). This approach enables PNs' scalable fabrication with enhanced adhesion properties, while CMHB increases adhesion between the UV‐curable resin and Ag, offering scalability to large‐area applications with UV‐NIL. The structural morphology and chemical properties of the fabricated PNs are analyzed using scanning electron microscopy, atomic force microscopy, energy‐dispersive spectroscopy, and X‐ray photoelectron spectroscopy. These PNs demonstrate potential in CCD filters, enhancing optical signal amplification for real‐time imaging at the 785 nm band. This robust fabrication method advances PNs' performance and scalability, advancing nanophotonics and related applications.

Total losses and dispersion effects management and upgrading fiber reach in ultra-high optical transmission system based on hybrid amplification system

Abstract This work demonstrated the total losses and dispersion effects management and upgrading the fiber reach in ultra-high optical transmission system based on hybrid amplification system. Based on the requirements of the system, a number of trade-offs must be made between the numerous interconnected performance characteristics of each component in the design of a high quality transmission link. The transmission distance is the greatest distance that an optical signal has to travel. It affects the choice of optical component, fiber type, and signal amplification techniques. Fiber amplifiers or signal regeneration may be required to compensate for signal loss over greater distances. Reviewing these crucial aspects helps when selecting the best optical components and system layout. This ensures the optical link performs as expected. Hybrid amplification system unit (EDFA/Raman/EDFA), (EDFA/Raman), (BFA/PDFA) and (Raman/EDFA) is employed in the transmission system to strength the signal and upgrade the system performance operation efficiency. Space division multiplexing scheme is also employed with the propagation scheme in order to upgrade and control of the total losses and dispersion effects. The optimum total losses/dispersion/repeater spacing are studied with the variations of the total number of links per fiber core channel.

Control of temperature dependent viscosity for manufacturing of Bi-doped active fiber

Bi-activated photonic materials are promising for various applications in high-capacity telecommunication, tunable laser, and advanced bioimaging and sensing. Although various Bi-doped material candidates have been explored, manufacturing of Bi heavily doped fiber with excellent optical activity remains a long-standing challenge. Herein, a novel viscosity evolutional behavior mediated strategy for manufacturing of Bi-doped active fiber with high dopant solubility is proposed. The intrinsic relation among the evolution of Bi, reaction temperature and viscosity of the glass system is established. Importantly, the effective avenue to prevent the undesired deactivation of Bi during fiber drawing by tuning the temperature dependent viscosity evolution is built. By applying the strategy, for the first time we demonstrate the success in fabrication of heavily doped Bi active fiber. Furthermore, the principal fiber amplifier device is constructed and broadband optical signal amplification is realized. Our findings indicate the effectiveness of the proposed temperature dependent viscosity mediated strategy for developing novel photonic active fiber, and they also demonstrate the great potential for application in the next-generation high-capacity telecommunication system.

Fluid Multivalent Recognition Accelerating and Boosting Upconversion Luminescence-Activated DNA Nanomachines for Rapid and Sensitive In Vivo Imaging.

By integrating near-infrared (NIR) light-dependent optical control and DNA walkers-based signal amplification, upconversion luminescence-activated DNA nanomachines hold great potential in conducting an in vivo analysis. For the typical DNA nanomachines, the immobile multivalent recognition interface greatly compromised the reaction kinetics and amplification efficiency due to the cleavage-dependent response mode. In this work, novel upconversion luminescence-activated DNA nanomachines with a fluid multivalent recognition interface were reported for rapid and sensitive in vivo imaging. As a proof-of-concept study, the photolocked DNAzyme-based walker system was anchored on the surface of phospholipid membrane-coated upconversion nanoparticles through the cholesterol-phospholipid interaction to acquire a fluid multivalent recognition interface. Upon sequential inputs of NIR light and metal ions, the formed DNA nanomachines were autonomously initiated and generated a cascade of amplified signal. Relative to the typical DNA nanomachines, the proposed ones possess an accelerated reaction rate and an improved amplification capability owing to a higher local concentration by the lateral mobility. The present work provides a versatile alternative for performing precise and highly efficient in vivo analysis.

Raman/EDFA Hybrid System to Enhance the Optical Signal in the Optical Network

In this paper, a hybrid optical signal amplification system that includes Raman scattering and Erbium-doped fiber amplifier (EDFA) was simulated to take advantage of the amplification properties of the optical signal transmitted through the optical fiber network that connects the first and third campuses of the University of Mosul. The two types of optical signal amplifiers were studied individually and together, and the effect was observed in each case on the optical signal parameters such as the Q-factor, noise figure, signal-to-noise ratio, and gain. Optisystem ver.7.0 software was used to simulate the proposed system. The results showed that the Raman scattering and EDFA hybrid systems functioned effectively. The output signal power level is higher than the input signal power level that increased from (16 microwatts) to (83 mill watts). For each frequency, the gain is positive and the noise figure is relatively high. Although, this indicates that some noise introduced into the system. The output signal to noise ratio (OSNR) is high (55 dB). Moreover, the system is still able to maintain a high signal-to-noise ratio. The obtained results showed that the Raman scattering and EDFA hybrid system is a worthwhile technique for amplifying optical signals for the optical network connecting the first and third campuses of the University of Mosul.

Responsive Janus droplets as modular sensory layers for the optical detection of bacteria

The field of biosensor development is fueled by innovations in new functional transduction materials and technologies. Material innovations promise to extend current sensor hardware limitations, reduce analysis costs, and ensure broad application of sensor methods. Optical sensors are particularly attractive because they enable sensitive and noninvasive analyte detection in near real-time. Optical transducers convert physical, chemical, or biological events into detectable changes in fluorescence, refractive index, or spectroscopic shifts. Thus, in addition to sophisticated biochemical selector designs, smart transducers can improve signal transmission and amplification, thereby greatly facilitating the practical applicability of biosensors, which, to date, is often hampered by complications such as difficult replication of reproducible selector-analyte interactions within a uniform and consistent sensing area. In this context, stimuli-responsive and optically active Janus emulsions, which are dispersions of kinetically stabilized biphasic fluid droplets, have emerged as a novel triggerable material platform that provides as a versatile and cost-effective alternative for the generation of reproducible, highly sensitive, and modular optical sensing layers. The intrinsic and unprecedented chemical-morphological-optical coupling inside Janus droplets has facilitated optical signal transduction and amplification in various chemo- and biosensor paradigms, which include examples for the rapid and cost-effective detection of major foodborne pathogens. These initial demonstrations resulted in detection limits that rival the capabilities of current commercial platforms. This trend article aims to present a conceptual summary of these initial efforts and to provide a concise and comprehensive overview of the pivotal kinetic and thermodynamic principles that govern the ability of Janus droplets to sensitively and selectively respond to and interact with bacteria.Graphical abstract

Clustering engineering in tellurium-doped glass fiber for broadband optical amplification

Dense wavelength division multiplexing (DWDM) is recognized as one of the leading technologies for resolving the internet data traffic capacity issue. Although the successful development of rare-earth doped fiber amplifiers enables to achieve optical signal amplification in various telecommunication wavebands, their bandwidth is limited by the inherent sharp 4f electronic transition. Here, we propose the clustering engineering strategy in tellurium (Te)-doped glass fiber for broadband optical amplification. The correlation among the glass system, chemical state of Te and the optical response are systematically studied. The active Te-doped phosphate glass with intense and broadband luminescence is successfully achieved by control of the cluster state of the Te atoms. Subsequently, Te-activated phosphate fiber is successfully drawn and the optical response is transferred smoothly. Importantly, the amplified spontaneous emission and broadband optical amplification are achieved for the first time in Te-doped glass fiber. A small signal on-off gain covering an ultra-wide range of O + E + S + C + L bands is observed under excitation at 808 nm. Our results establish a critical step toward advancing Te-based photonic materials for novel broadband fiber amplifiers serviced in telecommunication system.

Optical Processes behind Plasmonic Applications.

Plasmonics is a revolutionary concept in nanophotonics that combines the properties of both photonics and electronics by confining light energy to a nanometer-scale oscillating field of free electrons, known as a surface plasmon. Generation, processing, routing, and amplification of optical signals at the nanoscale hold promise for optical communications, biophotonics, sensing, chemistry, and medical applications. Surface plasmons manifest themselves as confined oscillations, allowing for optical nanoantennas, ultra-compact optical detectors, state-of-the-art sensors, data storage, and energy harvesting designs. Surface plasmons facilitate both resonant characteristics of nanostructures and guiding and controlling light at the nanoscale. Plasmonics and metamaterials enable the advancement of many photonic designs with unparalleled capabilities, including subwavelength waveguides, optical nanoresonators, super- and hyper-lenses, and light concentrators. Alternative plasmonic materials have been developed to be incorporated in the nanostructures for low losses and controlled optical characteristics along with semiconductor-process compatibility. This review describes optical processes behind a range of plasmonic applications. It pays special attention to the topics of field enhancement and collective effects in nanostructures. The advances in these research topics are expected to transform the domain of nanoscale photonics, optical metamaterials, and their various applications.

One-Pot Synthesis of Silica-Coated Gold Nanostructures Loaded with Cyanine 5.5 for Cell Imaging by SERS Spectroscopy

Anisotropic gold nanoparticles have been recognized as promising agents for medical diagnostics and cancer therapy due to their wide functionality, photothermal effect, and ability for optical signal amplification in the near-infrared range. In this work, a simple and rapid method for the preparation of bone-shaped gold nanoparticles coated with a dye-impregnated silica shell with an aminated surface is proposed. The possibility of further functionalization the nanostructures with a delivery vector using folic acid as an example is demonstrated. The average size of the resulting tags does not exceed 70 nm, meeting the criteria of cell endocytosis. The prepared tags exhibit surface-enhanced Raman scattering (SERS) spectra at excitation with lasers of 632.8 and 785 nm. Cell imaging is performed on HeLa cells based on the most pronounced SERS bands as a tracking signal. The obtained images, along with scanning electron microscopy of cell samples, revealed the tendency of tags to agglomerate during endocytosis followed by the "hot spots" effect. To evaluate the toxic and proliferative effect of the nanotags, an MTT assay was performed with two HeLa and HEP G2 cell lines. The results revealed higher viability for HEP G2 cells.

Signal amplification strategies for optical biodetection at the liquid crystal–solid interface

ABSTRACTLiquid crystals (LCs) are reliable signal transducers for biosensors with chemical and biological sensing potentials demonstrated on the basis of their anisotropy. Thanks to the high sensitivity and fast response to analytes, the LC–solid, LC–aqueous and LC droplet interfaces facilitate sensing platforms to be established without the requirement of sophisticated and costly analytical instruments. In this mini-review, we summarise strategies of optical signal amplification to improve the detection limit of biological analytes at the LC–solid interface. Because approaches towards signal amplification for a single target analyte are seldom compared by discussing various LC-based biosensing platforms, this mini-review may provide implications for integrating current technologies to promote the development of multiplex platforms based on the LC–solid interface.

Passive Amplification and Noise Mitigation of Optical Signals Through Talbot Processing

Noise is one of the rare aspects of experimental work that crosses all boundaries. It is present from scientific fields like ultrafast optical signal detection to applied fields such as image processing, or even in our day-to-day lives when we are simply trying to have a conversation in a loud room. In all these cases, incoherent, stochastic noise tends to drown a signal we aim to detect, and various techniques may need to be employed to improve the clarity of the waveform, which is characterized by the signal-to-noise ratio (SNR). Yet, considering the ubiquity of noise in scientific and technology fields, it may be surprising how few methods there exists for denoising a signal. Active amplification techniques alone cannot be employed for weak, noisy signals, since the SNR is inevitably degraded due to fundamental laws of physics, while bandpass filtering schemes necessarily lead to an attenuation of the signal. In this article, we review recent advances on the concept of passive amplification techniques based on the Talbot effect to enhance the noise properties of signals through coherent energy redistribution. We demonstrate the basic framework starting from pulse repetition rate multiplication with the Talbot effect. We then extend this theory to show the principle behind passive amplification of periodic waveforms, and then how this idea can be extended to arbitrary (generally, aperiodic) signals. Methods for passive amplification of both the time-domain and the frequency-domain representations of the signal of interest are reviewed. While here we focus on the application of the technique for optical signals in the standard telecommunication band (near wavelengths of 1550 nm), the proposed denoising scheme relies on widely available wave manipulations, such that it may offer exciting opportunities for any kind of physical wave support, such as acoustics, plasmonics and other regimes of the electromagnetic spectrum, like microwaves or X-rays.

Plasmon-Exciton Coupling Effect in Nanostructured Arrays for Optical Signal Amplification and SARS-CoV-2 DNA Sensing.

A surface plasmon resonance (SPR)-enhanced optical signal using a nanoslit array and acridine orange (AO) dye system at a flexible poly(dimethylsiloxane) (PDMS) substrate was achieved in this work and demonstrated a simple sensing scheme to directly detect SARS-CoV-2 nucleic acid via DNA hybridization. A simple nanoimprinting pattern transfer technique was introduced to form uniform reproducible nanoslit arrays where the dimensions of the slit array were controlled by the thickness of the gold film. The plasmon-exciton coupling effect on the optical enhancement of different dye molecules, i.e., AO, propidium iodide (PI), or dihydroethidium (DHE) attached to the nanoslit surfaces, was examined thoroughly by measuring the surface reflection and fluorescence imaging. The results indicate that the best overlap of the plasmon resonance wavelength to the excitation spectrum of AO presented the largest optical enhancement (∼57×) compared to the signal at flat gold surfaces. Based on this finding, a sensitive assay for detecting DNA hybridization was generated using the interaction of the selected SARS-CoV-2 ssDNA and dsDNA with AO to trigger the metachromatic behavior of the dye at the nanoarray surfaces. We found strong optical signal amplification on the formation of acridine-ssDNA complexes and a quenched signal upon hybridization to the complementary target DNA (ct-DNA) along with a blue shift in the fluorescence of AO-dsDNAs. A quantitative evaluation of the ct-DNA concentration in a range of 100-0.08 nM using both the reflection and emission imaging signals demonstrated two linear regimes with a lowest detection limit of 0.21 nM. The sensing method showed high sensitivity and distinguished signals from 1-, 2-, and 3-base mismatched DNA targets, as well as high stability and reusability. This approach toward enhancing optical signal for DNA sensing offers promise in a general, rapid, and direct vision detection method for nucleic acid analytes.

МОДЕЛЮВАННЯ РОЗПОДІЛЕНОГО НЕЛІНІЙНО-ОПТИЧНОГО ПІДСИЛЕННЯ У ТЕЛЕКОМУНІКАЦІЙНИХ ВОЛОКНАХ TRUEWAVERS ТА G.652

Common techniques for modeling of the nonlinear optical amplifiers, specifically based on the effect Raman effect, despite the simplicity of its technical implementation, are quite complex and cumbersome due to the necessity of theoretically describing the nonlinear interaction of many pump and signal optical waves using the corresponding systems of high-order differential equation. The fundamental limitations of such methodologies lie not only in the number of equations but also in the existence of special points in each equation describing the dynamics of signal waves (these points correspond to threshold values of pump power). Under these conditions, the solutions instabilities of the differential equations and their ambiguity sometimes have a detrimental impact on modeling results. An alternative modeling approach using the specified pump approximation requires particular investigations of its practical applicability to the analysis of distributed optical amplification in telecommunications fibers. Therefore, there is a need to determine the criterion for the applicability of the specified pump approximation for the development of a simplified model of nonlinear optical signal amplification under the conditions of their propagation along standard silica fibers. Among the undeniable advantages of analytical solutions obtained based on the simplified model there is the elimination of the mentioned constraints of solving systems of many differential equations. This article is devoted to modeling the dynamics of distributed Raman amplification, as function the length of standard single-mode optical fiber (SMF) and pump power. In justifying the proposed modeling methodology, it is shown that the parameters of active fibers and fiber Raman amplifier (hereinafter referred to as FRA) schemes correspond to the criterion for the applicability of the specified pump approximation. The paper presents an analytical expression for the criterion of the applicability of the specified pump approximation in the form of an upper limit of the signal power, which cannot exceed the amplified signal. Comparative analysis results of the distributed FRA parameters depending on the length of active fibers, such as G.652 and TrueWaveRS, are presented.

Modeling and numerical simulation of gain of Nd-doped fiber amplifier in 1. 7um~1. 8um

Fiber amplifier is an important piece of equipment to ensure the long-distance communication of optical fiber. The rare-earth ion-doped fiber amplifier is a hot issue studied in many articles. However, few articles investigate Neodymium-doped fiber amplifiers for 1.7μm optical signal amplification because of the low signal gain. Therefore, this paper establishes the system model of Neodymium ion to realize the optical signal amplification in the 1.7μm band. It establishes its mathematical model by using the equation of rate and power transmission equation and solves it numerically to realize the numerical simulation of Neodymium-doped fiber amplifier for 1.7μm optical signal amplification, and studies the simulation results, summarizes the amplifier properties, and fits the results to get the mathematical expressions. This paper finds that the plot of gain variation with fiber position contains a linear asymptote with a slope less than zero. The asymptote is related to the initial signal light and the optical power of the pump. Increasing the doping concentration will cause the optical signal to converge to this asymptote faster. The numerical fitting results in this paper can be applied to the estimation of gains as well as to generate insights into theoretical studies, such as considering the possibility of applying the Weber distribution commonly used for infinite optical communication in fiber models.

A Rainbow Structural Color by Stretchable Photonic Crystal for Saccharide Identification.

Photonic crystals (PCs) with fascinating structural color nanomaterials present effectively spontaneous emission modulation and selectively optical signal amplification. Stretchability or elasticity could enable the feasible tunability for structural colors. Aimed at the regulation of structural colors, we endeavored to achieve the PC nanomatrix evolution and optical property during stretching. In this work, a rainbow structural color by stretchable PCs was exploited to provide abundant optical information for multianalyte recognition. The finite element analysis proved the electric field distribution in the PC matrix, which completely matched with the phenomenon of the measured PC spectra. By simply employing analysis of the multistate PC during stretching, the mono PC matrix chip can differentially enhance fluorescence signals in broad spectral regions, resulting in diverse sensing information for high-efficiency multianalysis. The stretchable PC chip can facilely discriminate 14 similar structured saccharides with a minimum concentration of 10-7 M using only one fluorescence complex. Furthermore, saccharides in different concentrations, mixtures, and real samples (beverages and sweets) also can be successfully distinguished. The exploration on fluorescent stretch dependence behavior of the photonic crystal contributes the biomatching optical platform for wearable devices, dynamic environment, clinical, or health monitoring auxiliary.

Dual‐Functional Nonmetallic Plasmonic Hybrids with Three‐Order Enhanced Upconversion Emission and Photothermal Bio‐Therapy

AbstractPlasmonic semiconductor nanoparticles (NPs) with wide‐range tailorable localized surface plasmon resonance (LSPR) hold exciting prospects on optical signal amplification. In this work, by precisely controlling oxygen vacancies around W atoms, plasmonic bismuth tungstate Bi2WO6 (BWO) nanosheets are constructed to enhance emission of Yb3+/Er3+ co‐doped NaYF4 upconversion nanoparticles (UCNPs). In the optimal conditions, the UCNPs/BWO‐2 hybrids exhibit over three‐order (1260‐fold) enhancement selectively on the 520 nm emission owing to the strong LSPR‐induced electrical field and photothermal effect. Moreover, it is found that the highly efficient emission of UCNPs/BWO‐2 allows it to act as a thermometer to monitor the real‐time local temperature with high absolute sensitivity of 5.8 × 10−3 K−1 in wide temperature range (up to 990 K). For proof‐of‐concept, the dual functions of plasmonic UCNPs/BWO‐2 hybrids on bioimaging and photothermal therapy for cancer cells are demonstrated that can be completely killed within 5 min under 980 nm irradiation. As far as it is known, this work reaches a new level on UCNPs emission enhancement by plasmonic semiconductor, exceeding most plasmonic metals.

Optical signal amplification between pages for holographic data storage

This work proposes a page differential intensity amplification for optical signal amplification in the intensity multiplexing holographic data storage system. The proposed method detects the signals of four cameras and reconstructs the intensity difference between two pages. The reconstructed intensity difference is amplified by the ratio of the readout beam amplitude to the local oscillator beam amplitude. Experiments showed that the proposed method can achieve a more stable signal amplification than the conventional amplification technique. Moreover, signal detection is possible with one third the intensity of the readout beam compared to the conventional direct detection method. This corresponds to 1.8 times the recording capacity increase if the capacity is limited by M/#, or the reduction to one third the readout exposure time.

Flash Colloidal Gold Nanoparticle Assembly in a Milli Flow System: Implications for Thermoplasmonic and for the Amplification of Optical Signals

The assembly and stabilization of a finite number of nanocrystals in contact in water could maximize the optical absorption per unit of material. Some local plasmonic properties exploited in applications, such as photothermia and optical signal amplification, would also be maximized which is important in the perspective of mass producing nanostructures at a lower cost. The main lock is that bringing charged particles in close contact requires the charges to be screened/suppressed, which leads to the rapid formation of micrometric aggregates. In this article, we show that aggregates containing less than 60 particles in contact can be obtained with a milli-flow system composed of turbulent mixers and flow reactors. This process allows to stop a fast non-equilibrium colloidal aggregation process at millisecond times after the initiation of the aggregation process which allows to control the aggregation number. As a case study, we considered the rapid mixing of citrate coated gold nanoparticles (NP) and AlCl3 in water to initiate a fast aggregation controlled by diffusion. Injecting a solution of polycation using a second mixer allowed us to arrest the aggregation process after a reaction time by formation of overcharged cationic aggregates. We obtained within seconds stable dispersions of a few milliliters composed of particle aggregates. Our main result is to show that it is possible to master the average aggregation number between 2 and 60 NP per aggregate by varying the a reaction time between 10 ms and 1 s.