Pump Profile Research Articles

Performance evaluation of a two-stage few-mode EDFA for high-capacity SDM systems

Space division multiplexing (SDM) systems using few-mode fibers (FMF) are essential for next-generation fiber optic communications. Optical amplifiers with low noise, minimal differential modal gain (DMG), and minimal differential spectral gain (DSG) are essential for these systems. In this work, we present a method to design and optimize a two-stage few-mode erbium-doped fiber amplifier (FM-EDFA) using a joint DMG-DSG minimization approach. This methodology involves the pumping profile design and the gain flattening filter design. Simulation results show the two-stage FM-EDFA achieves DMG and DSG below 2.8 dB and 0.42 dB, respectively, with an optical signal-to-noise ratio above 19 dB across the C-band, enabling a system capacity of 48.6 Tbps. This work reveals the effectiveness of this two-stage FM-EDFA for optical amplification in the context of SDM systems.

Silicon-Based Piezo Micropumps Enable Fully Flexible Drug Delivery Patterns

Drug release plays a crucial role in drug delivery. While current formulation approaches are capable of coarse-tuning the release profile, their precision and reproducibility are limited by the physicochemical properties of the excipients and active pharmaceutical ingredient (API). Innovative and advanced approaches are urgently needed, especially for site-specific targeting of drugs and to address their pharmacological requirements for optimal therapy. The 5 × 5 × 0.6 mm3 piezoelectric micropump developed by Fraunhofer EMFT was designed to enable precise drug delivery in a low volume format. In this study, we investigated the ability of the micropump to deliver solutions of highly soluble APIs using a wide range of customized pump profiles. Additionally, we examined the ability of the micropump to deliver suspensions containing various defined particle sizes. While results for suspensions indicate that pumping performance is highly dependent on the size and concentration of the suspended particles, results with API solutions demonstrate high precision and reproducibility of release, coupled with maximum flexibility in the release profile of the API. The piezoelectric micropump thus lays the cornerstone in the development of a wide range of innovative drug delivery profiles, enabling customized release profiles to be programmed and thus paving the way to fully personalized medicine.

Investigation of Temperature Cycling with Coupled Vessels for Efficient Deracemization of NMPA.

Chiral compounds can exist as pairs of nonsuperimposable stereoisomers (enantiomers) possessing the same physical properties but interacting differently with biological systems. This makes them interesting materials to be explored by the pharmaceutical and food industries. In this study, to obtain pure enantiomers from their conglomerates, a method that involves using a two-vessel system for deracemization of N-(2-methylbenzylidene) phenylglycine amide (NMPA) was developed. In this method, a suspension was transferred with a pulsating pumping profile between two inter-connected stirred vessels that were set at constant temperatures. As the suspension was exposed to more rapid changes in temperature, it resulted in the speeding up of the process and thus enhancing productivity in comparison to a single vessel system. The results confirmed successful deracemization of NMPA. A modified pumping profile and tubing design eliminated the issue of clogging of the transfer tubes and ensured effective suspension transfer for longer durations. Operating parameters, such as initial enantiomeric excess, vessel residence time, and suspension density were also investigated. In this method, optimization of residence time was necessary to enhance the efficiency of the process further. Results confirmed that this methodology has the potential to be more adaptable and scalable as it involved no mechanical attrition.

High-efficiency broad-linewidth widely-tunable mid-infrared OPO based on fan-out PPLT

We reported a high-efficiency, broad-linewidth, wide-tuning-range singly-resonated optical parametric oscillator (OPO) based on a fan-out PPLT crystal. When the PPLT crystal was operated at 120 °C and pumped by Q-switched 1064 nm laser at 14.17 W with a circular pump profile, the overall output power of OPO was 7.22 W (η = 50.4%) for both the signal and idler waves. The central wavelength and linewidth of the mid-infrared (MIR) laser were 3770 nm and ∼40 nm. A wavelength tuning range of 3538–3941 nm was accomplished by adjusting the crystal period through simple mechanical movement. Due to the larger coverage of gratings with an elliptical pump profile, the output linewidth of the MIR laser was further broadened to ∼100 nm, which is ten times more than other non-fan-out PPLT OPOs. Both pumping methods with different profiles were operated at 30 kHz, 49.2 ns for the 1064 nm laser, the power fluctuation of the obtained MIR laser was within 3.5%.

Spatial-spectral mapping to prepare frequency entangled qudits.

Entangled qudits, the high-dimensional entangled states, play an important role in the study of quantum information. How to prepare entangled qudits in an efficient and easy-to-operate manner is still a challenge in quantum technology. Here, we demonstrate a method to engineer frequency entangled qudits in a spontaneous parametric downconversion process. The proposal employs an angle-dependent phase-matching condition in a nonlinear crystal, which forms a classical-quantum mapping between the spatial (pump) and spectral (biphotons) degrees of freedom. In particular, the pump profile is separated into several bins in the spatial domain, and thus shapes the down-converted biphotons into discrete frequency modes in the joint spectral space. Our approach provides a feasible and efficient method to prepare a high-dimensional frequency entangled state. As an experimental demonstration, we generate a three-dimensional entangled state by using a homemade variable slit mask.

Sensitivity and spectral control of network lasers

Recently, random lasing in complex networks has shown efficient lasing over more than 50 localised modes, promoted by multiple scattering over the underlying graph. If controlled, these network lasers can lead to fast-switching multifunctional light sources with synthesised spectrum. Here, we observe both in experiment and theory high sensitivity of the network laser spectrum to the spatial shape of the pump profile, with some modes for example increasing in intensity by 280% when switching off 7% of the pump beam. We solve the nonlinear equations within the steady state ab-initio laser theory (SALT) approximation over a graph and we show selective lasing of around 90% of the strongest intensity modes, effectively programming the spectrum of the lasing networks. In our experiments with polymer networks, this high sensitivity enables control of the lasing spectrum through non-uniform pump patterns. We propose the underlying complexity of the network modes as the key element behind efficient spectral control opening the way for the development of optical devices with wide impact for on-chip photonics for communication, sensing, and computation.

Study of the Pulse of Peristaltic Pumps for Use in 3D Extrusion Bioprinting.

Peristaltic pumps are used in healthcare for their ability to aseptically displace various fluids, including medium-density gels and suspended solids. However, they have the undesirable characteristic of pulsing at their output. Three-dimensional printing is becoming a reality in tissue engineering, and it generally uses syringes to extrude hydrogels. One of the problems to be solved is the microdosing of biomaterials or bioinks when it is necessary to print large volumes. The use of peristaltic pumps in bioprinting is desirable as it does not limit the volume to the contents of a syringe while achieving dosage control. A peristaltic pump was designed and implemented to avoid pulsation errors and microliter dosing while allowing a large amount of fluid displacement. Two pumps with equal displacement were built. The first uses the conventional profile and is the baseline for comparisons, while the second presents the profile studied and proposed. The concepts demonstrated by Bernoulli were used, fixing the height of a column of water, while the two pumps provide flow to the system asynchronously, allowing the reading of pressure as a function of the speed variation created by the pulsation of each pump. An approximately 100 times reduction in pulsation was observed during fluid displacement with the variance reduced from 2.64 to 0.025 s2. The two pumps were also installed on a modified Ultimaker FDM 3D printer, and a standard for comparison was printed using a water-based hydrogel, corn starch, and corn-derived triglyceride, showing that the proposed pump improves the deposition quality of the material. Three-dimensional prints, tubes 20 mm in diameter by 8 mm in height and 0.7 mm in wall width, were also produced. Videos obtained show that the first pump was not able to print more than 4 mm in height, while the second prints the model with high quality and without deficiency. The results show that the new pump profile is able to provide a sufficiently constant volume for three-dimensional printing with excellent deposition control, building a simple object but difficult to obtain for a common peristaltic pump.

Uniform and Non-Uniform Pumping Effect on Ce:Nd:YAG Side-Pumped Solar Laser Output Performance

The Ce:Nd:YAG is a recent active medium in solar-pumped lasers with great potential. This study focuses on the influence of two secondary concentrators: a fused silica aspherical lens and a rectangular fused silica light guide; and consequent pump light distribution on the output performance of a Ce:Nd:YAG side-pumped solar laser. The solar laser head with the aspherical lens concentrated the incident pump light on the central region of the rod, producing the highest continuous-wave 1064 nm solar laser power of 19.6 W from the Ce:Nd:YAG medium. However, the non-uniformity of the absorbed pump profile produced by the aspherical lens led to the rod fracture because of the high thermal load, limiting the maximum laser power. Nevertheless, the solar laser head with the light guide uniformly spread the pump light along the laser rod, minimizing the thermal load issues and producing a maximum laser power of 17.4 W. Despite the slight decrease in laser power, the use of the light guide avoided the laser rod fracture, demonstrating its potential to scale to higher laser power. Therefore, the pumping distribution on the rod may play a fundamental role for Ce:Nd:YAG solar laser systems design.

Effects of pumping profiles on the temperature distributions in doubleend pumped solid-state lasers: A comparison study

In this work, the effects of pumping profiles on the temperature distributions in solid-state lasers pumped by laser diode from two different end faces were studied. With different pump spot radii of , various exponent factors were examined to evaluate the behavior of temperature distributions due to Gaussian and super-Gaussian profiles. For a Gaussian pumping (n=2), the maximum temperature difference on each rod face was calculated to be 295.5 K and 226 K, respectively, at a total pump power of 92.8 W (46.4 W per face). While at the same pumping power, the temperature decreased as the n exponent increased. A good match was obtained between the proposed model and the previous works listed in the literature.

Influence of transverse carrier diffusion on two-dimensional optical rogue waves in broad-area semiconductor lasers with a saturable absorber

The statistics and dynamics of two-dimensional rogue waves in a broad-area semiconductor laser with an intracavity saturable absorber are numerically investigated under the effect of transverse carrier diffusion. We show that lateral diffusion of carriers alters the statistics of rogue waves by enhancing their formation in smaller ratios of carrier lifetimes in active and passive materials while suppressing them when the ratio is larger. The temporal dynamics of the emitted rogue waves is also studied and show that the finite nonzero transverse carrier diffusion coefficient gives them a longer duration. To further approach a realistic experimental situation, we also investigate the statistics and dynamics of rogue waves by simulating a circular disk-shape pump which replaces the flat pump profile typically used in numerical simulations of broad-area lasers. We show that a finite pump shape reduces the number of emitted rogue waves per unit area both below and above the laser threshold for every carrier lifetime ratio. The temporal width of the emitted rogue waves is also shown to decrease as a consequence of removing the nonphysical effects of the infinite flat pump on carrier dynamics.

Impact of the terahertz and optical pump penetration depths on generated strain waves temporal profiles in a V2O3 thin film

Triggering new stable macroscopic orders in materials by ultrafast optical or terahertz pump pulses is a difficult challenge, complicated by the interplay between multiscale microscopic mechanisms, and macroscopic excitation profiles in samples. In particular, the differences between the two types of excitations are still unclear. In this article, we compare the optical response on acoustic timescale of a V2O3 Paramagnetic Metallic (PM) thin film excited by a terahertz (THz) pump or an optical pump, at room temperature. We show that the penetration depth of the deposited energy has a strong influence on the shape of the optical transmission signal, consistent with the modulation of permittivity by the superposition of depth-dependent static strain, and dynamical strain waves travelling back and forth in the sample layer. In particular, the temporal modulation of the optical transmission directly reflects the excitation profile as a function of depth, as well as the sign of the acoustic reflection coefficient between the film and the substrate. The acoustic mismatch between the V2O3 layer and the substrate was also measured. The raw data were interpreted with a one-dimensional analytical model, using three fitting parameters only. These results are discussed in the context of triggering phase transitions by ultrafast pump pulses. To the best of our knowledge, this is the first report of the modulation of the optical transmission of V2O3 with a THz pump within the acoustic timescale.

Reconfiguration of optical continuous-wave radiations by bright soliton trains in gas-filled hollow-core photonic crystals (HC-PCFs)

We investigate the reconfiguration of a low-intensity probe propagating in the optical trap created by a train of temporal pulses, in a hollow-core photonic crystal filled with gas. The reconfiguration scheme rests on the assumption that a temporal pulse train can trap low-intensity fields in hollow-core photonic crystals, in order to compensate for their dispersion during propagation. We find a family of three bound states with different propagation constants, representing the three possible distinct pump-reconfigured probe profiles one of which is a “copy” of the pump. We analyze the effects of self-steepening on the pump and probe profiles and find that self-steepening causes a uniform shift of the pump, but a complex motion for the probe featuring anharmonic oscillations. The proposed trapping scheme is intended for optical applications involving optical-field cloning and duplication via wave guided-wave processes in photonic fiber media, in which interplay time-division multiplexed high-intensity pulses coexisting with continuous waves.

Optimal Pump Shaping for Entanglement Control in Any Countable Basis

AbstractControlling spatial mode entanglement of bi‐photon states has become paramount in quantum optics experiments, where a spontaneous parametric downconversion (SPDC) state is tailored into a desired state through control of the SPDC pump light. Particular pump shaping solutions exist but have been shown for only special cases, such as orbital angular momentum, and always at the expense of noise. Here, a basis‐independent approach to the pump shaping problem that crafts the problem in terms of an invertible tensor equation is presented, making it possible to determine the requisite pump profile for any desired downconversion joint probability spectrum, often analytically. It is first shown that this approach reproduces a number of prior results exactly and then go on to demonstrate results not possible with existing techniques, such as shaping quantum states in new bases and controlling the signal‐to‐noise ratio. It is believed that this approach is optimal as the solvable tensor equation can be tailored to focus on any desired state (sub)space and can be optimized with respect to a chosen norm. This work provides a universal approach to quantum state engineering through deterministic shaping of the SPDC pump light, making it a highly suitable workhorse of quantum optics experiments.

Non-Hermitian arrangement for stable semiconductor laser arrays.

We propose and explore a physical mechanism for the stabilization of the complex spatiotemporal dynamics in arrays (bars) of broad area laser diodes taking advantage of the symmetry breaking in non-Hermitian potentials. We show that such stabilization can be achieved by specific pump and index profiles leading to a PT-symmetric coupling between nearest neighboring lasers within the semiconductor bar. A numerical analysis is performed using a complete (2 + 1)-dimensional space-temporal model, including transverse and longitudinal spatial degrees of freedom and temporal evolution of the electric field and carriers. We show regimes of temporal stabilization and light emission spatial redistribution and enhancement. We also consider a simplified (1 + 1)-dimensional model for an array of lasers holding the proposed non-Hermitian coupling with a global axisymmetric geometry. We numerically demonstrate a two-fold benefit: the control over the temporal dynamics over the EELs bar and the field concentration on the central lasers leading to a brighter output beam, facilitating a direct coupling to an optical fiber.

A Highly Inclusive Theory of Q-Switched Lasers

A highly inclusive theory of Q-switched lasers is presented which applies to both actively and passively Q-switched lasers. The theory expands on the author’s previous publications on energy optimization to include: (1) saturable absorbers exhibiting excited state absorption and therefore a finite Figure of Merit (FOM); (2) unequal beam areas in the gain and absorbing media; and (3) both pulsed and CW pumping. Design curves for optimizing the output energy for pulse pumped lasers and CW pumped lasers at a desired pulse rate are provided. As in the author’s previous work, the optimization equation is obtained utilizing Lagrange Multipliers and yields the value of the parameter <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\rho = ln(n_{i}/n_{f})$ </tex-math></inline-formula> which maximizes the single pulse energy, where <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$n_{i}$ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$n_{f}$ </tex-math></inline-formula> are the laser inversion population densities before and after Q-switching. Using this initial result, the associated optimum absorber transmission and mirror reflectivity, pulse energy, peak power, and pulse width can be computed sequentially via simple formulas. The aforementioned parameters can all be expressed as functions of two variables, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\alpha $ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$z_{eff}$ </tex-math></inline-formula> , which are slight modifications of the variables <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\alpha $ </tex-math></inline-formula> and z previously introduced by the author for passively Q-switched lasers having infinite FOM and equal beam areas The term “plane wave theory” has sometimes been used by this and other authors in prior publications to describe a uniform pump profile in the laser medium, but we will refer to this special case more accurately as the “uniform pump theory”. The theory is extended here in the final section to include non-uniform pumping. The common case of a Q-switched laser end-pumped by a quasi-Gaussian CW laser is considered in detail and the theoretical results are found to agree well with experimental data.

Flat‐Top Pumped Multi‐Millijoule Mid‐Infrared Parametric Chirped‐Pulse Amplifier at 10 kHz Repetition Rate

AbstractThe advancement of mid‐infrared (MIR) parametric amplification technique serves as the main driving force of multiple strong‐field experiments in the frontier of science such as the generation of coherent soft X‐ray and isolated attosecond pulses. However, the low parametric down‐conversion efficiency especially in the MIR wavelength is a major bottleneck that hinders the further exploration of the MIR‐laser‐driven strong‐field physics. Here, a simple and robust method that doubles the efficiency of a MIR optical parametric chirped‐pulse amplifier (OPCPA) is reported, as a demonstration of the concept, through engineering a flat‐top pump profile via high‐efficiency diffractive optical elements. With the proposed flat‐top pump scheme, a MIR OPCPA system at 3 μm and 10 kHz repetition rate with both the record pulse energy of 2.7 mJ and the highest average power at 27 W among the MIR OPCPAs with kHz repetition rate is demonstrated. This work provides a promising approach for achieving high energy high power MIR few‐cycle lasers that can be readily used in emerging strong field experiments. In addition, it is believed that the developed technique in this work can become a general method of parametric efficiency enhancement, which is applicable to other nonlinear conversions and wavelength ranges.

Floquet description of optically pumped magnetometers

We present theoretical description of Voigt and Faraday effect based optically pumped magnetometers using the Floquet expansion. Our analysis describes the spin-operator dynamics of the first, $\hat{F}(t)$, and second, $\hat{F}^2(t)$, order moments and takes into account of different pumping profiles and decoherence effects. We find that the theoretical results are in good agreement with the experimental demonstrations over a wide range of fields and pumping conditions. Finally, the theoretical analysis presented here is generalized and can be extended to different magnetometry schemes with arbitrary pumping profiles and multiple radio-frequency fields.

Topological turbulence in spin-orbit–coupled driven-dissipative quantum fluids of light generates high-angular-momentum states (a) Contribution to the Focus Issue Turbulent Regimes in Bose-Einstein Condensates edited by Alessandra Lanotte, Iacopo Carusotto and Alberto Bramati.

We demonstrate the formation of a high-angular-momentum turbulent state in an exciton-polariton quantum fluid with TE-TM Spin-Orbit Coupling (SOC). The transfer of particles from quasi-resonantly cw pumped component to component is accompanied with the generation of a turbulent gas of quantum vortices by inhomogeneities. We show that this system is unstable with respect to the formation of bogolons at a finite wave vector, controlled by the laser detuning. This instability can be triggered by an inhomogeneity of the pumping profile as in present calculations or by other sources like natural disorder in the cavity. In a finite-size cavity, the domains with this wave vector form a ring-like structure along the border of the cavity, with a gas of mostly same-sign vortices in the center. The total angular momentum is imposed by the sign of TE-TM SOC, the wave vector at which the instability develops, and the cavity size. This effect can be detected experimentally via local dispersion measurements or by interference. The proposed configuration thus allows simultaneous experimental studies of quantum turbulence and high-angular-momentum states in continuously pumped exciton-polariton condensates.

Single-shot transient absorption spectroscopy techniques and design principles

Single-shot transient absorption (SSTA) spectroscopy is fundamentally identical to transient absorption (TA) spectroscopy but differs in its implementation to enable the measurement of sample response at a range of pump–probe time delays in a single laser shot. As in TA, a pump pulse in SSTA photoexcites a sample, inducing a change in the absorption of a probe pulse. Both commercial and home-built TA instruments typically execute serial measurements at a range of pump–probe time delays to yield transients that report on the dynamics of the photoexcited species, with the sample returning to the same relaxed state between each measurement. SSTA instruments acquire a range of pump–probe time delays simultaneously by somehow encoding the time delay into the profile of the probe beam. This dramatically reduces the time required for SSTA measurements, enabling the measurement of unstable systems undergoing irreversible processes that cannot be accurately characterized using typical TA instruments. The implementation of the encoded time delay must be appropriately designed and carefully calibrated to suit the targeted system and ensure accurate measurements. This review describes techniques used to encode the time delay and design principles for SSTA instruments. Strategies are presented to implement a broadband probe, account for spatial variations in pump and probe beam profiles that influence the intensity and noise of the spatially encoded signal, optimize detection, and correct for dynamic background signals. With these design principles in place, SSTA is capable of measuring an array of unstable and evolving systems that cannot be addressed using typical TA instruments.

Computer#aided design of the pump profile with epicycloidal gearing using MathCad tools

The article discusses a method for determining the relative eccentricity , used in calculating the thermal balance of an internal combustion engine sliding bearing. When performing this calculation, a number of temperature values are set in the bearing oil layer. For each set temperature, the engine oil viscosity value and the bearing load factor Ф are determined. To determine the relative eccentricity, graphical dependencies of the load factor on the relative eccentricity are used as input data. The thermal calculation of the sliding bearing showed that the accuracy of determining the relative eccentricity is of great importance. Their inaccurate definition leads to a failure of the thermal balance in the bearing. In addition, the method of determining the value of by the accepted value of the ratio of the working length of the bearing to the diameter of the connecting rod neck of the crankshaft (graphically) for this calculation is quite time-consuming. For this reason, the graphical method for determining has been replaced with an analytical one. Relative eccentricities were obtained using the least squares method. An algorithm has been developed for automated construction of transverse and longitudinal profiles of an oil pump with epicycloidal engagement.