High Pump Energy Research Articles

Mid-infrared optical parametric oscillator pumped by a high-pulse-energy, Q-switched Ho3+:YAG laser.

A high-pulse-energy mid-infrared light source is presented, based on a zinc-germanium-phosphide optical parametric oscillator (ZGP OPO) pumped by an actively $Q$-switched high-pulse-energy ${{\rm Ho}^{3 +}}{:}{\rm YAG}$ laser. The ${{\rm Ho}^{3 +}}{:}{\rm YAG}$ pump laser source is capable of generating a pulse energy of 15 mJ from a single ${{\rm Ho}^{3 +}}{:}{\rm YAG}$ rod at room temperature at a pulse repetition frequency (PRF) of 700 Hz. A maximum power of 20.1 W at a central wavelength of 2090 nm can be obtained in continuous operation, with a slope efficiency of 45.1%. A good beam quality with an ${{\rm M}^2}$ better than 1.3 was achieved in $Q$-switched operation. The presented laser architecture was used as a suitable pump source for a ZGP-based OPO. Operated at a PRF of 2 kHz and pumped with a pulse energy of 8 mJ, a low conversion threshold of 1.5 W and a maximum total output power of 6.3 W could be obtained in a linear ZGP-based OPO. At maximum power, the peak power of the generated mid-infrared radiation exceeded 120 kW, while the beam quality was affected by the strong gain lens building inside the nonlinear material as a consequence of the high-energy pump pulses.

Heat transfer and thermoregulation within single cells revealed by transient plasmonic imaging

Summary Cells, as the basic unit of life, undergo continuous heat transfer and dissipation during their metabolism, which is related not only to fundamental cellular functions but also massive applications. Unfortunately, thus far, we still know little about the heat transfer properties at the cellular or subcellular levels. Here, we demonstrated a transient microscopic method to measure the heat transfer in single cells. The thermal conductivity of different regions within a single cell shows a wide heterogeneity, and heat transfer in the region near the cell membrane is more active than the central region. However, the median values of thermal conductivity between different individual cells are quite close. A cellular-level heat regulation that responds to environmental temperature is observed in warm-blooded humans and chickens rather than in cold-blooded bullfrogs. According to the temperature-dependent cell metabolism, we proposed a hypothesis for cellular control of heat dissipation, which might be the cellular-level foundation of body thermoregulation.

High-sensitive terahertz detection by parametric up-conversion using nanosecond pulsed laser

A high-sensitive terahertz detector operating at room temperature was demonstrated based on parametric up-conversion. A nanosecond 1064-nm Nd:YAG laser was used to pump the parametric up-conversion detector and the up-conversion from terahertz wave to NIR laser was realized in a lithium niobate crystal. The minimum detectable terahertz energy of 9 pJ was realized with the detection dynamic range of 54 dB, which was three orders of magnitude higher than that of commercial Golay cell. The detectable terahertz frequency range of the detection system was 0.90 Thz–1.83 THz. Besides, the effects of pump energy and effective gain length on the detection sensitivity were studied in experiment. The results showed that higher pump energy and longer effective gain length are helpful for improving the detection sensitivity of parametric up-conversion detector.

Discussion on the factors affecting the pump efficiency of screw pump

Since the invention of screw pump in 1930, screw pump technology has been continuously improved and perfected, especially the development of synthetic rubber technology and bonding technology, which has made screw pump widely used in oil exploitation. Screw pump wells have the characteristics of low investment, high pump efficiency and energy saving. At present, screw pump has become a common artificial lifting method in oil fields using polymer flooding. In view of the present situation that screw pump wells are used for oil production more and more in Liuchang area, this paper discusses how to improve the production efficiency of screw pump wells in field production to promote the development of oil fields.

Polarization-insensitive, high-gain parametric amplification of radially polarized femtosecond pulses

Radially polarized lasers, in contrast to the conventional Gaussian laser mode, possess unique features such as sharp focusing and strong longitudinal fields. Thus far, radially polarized femtosecond pulses have been produced only by low-power devices such as mode-locked resonators and segmented half-wave plates. It is imperative to solve the bottleneck problem in generating higher powers and shorter durations. This paper reports on a polarization-insensitive, high-gain optical parametric amplifier for radially polarized femtosecond pulses, which works at type-II phase-matching and approximately degenerate wavelength. We experimentally demonstrate > --> 1000 -fold amplification of radially polarized ∼ 400 f s pulses at 1610 nm, via chirped ∼ 280 f s pumping at 800 nm, with the axially symmetric intensity profile and radial polarization state both being well-maintained within a 20 nm spectral range. With currently available high-energy picosecond pumping, the demonstrated amplification scheme will be promising to create radially polarized femtosecond pulses with ultrahigh powers and may facilitate future applications such as strong-field physics.

Efficient Fe:CdTe laser producing 0.35 J pulses in the 5 µm spectral range.

High-energy laser operation of a Fe2+-doped single-crystal CdTe is demonstrated at the temperature of 77 K. Pumped with 250 µs pulses of a 4.08 µm Fe:ZnSe laser, the Fe:CdTe laser produced a record output of 0.35 J, with a slope efficiency of 44%. A further up-scaling by employing high-energy pump sources is feasible, thus facilitating material-processing applications. The laser was tunable from 4.86 to 5.37 µm. In a nonselective cavity, the laser's central wavelength was 5.03 µm at 77 K, and shifted to 5.23 µm at 215 K. At the later operation point, reachable using a Peltier element, the laser still produced 0.15 J of output energy with an efficiency of 22%.

Concentration dependence of upconversion luminescence of Er3+/Yb3+ in the fluorophosphate glasses with small phosphates content

Abstract Frequency upconversion into green and red luminescence in fluorophosphate glasses doped with Er3+ ions (1021 to 1016 ion/cm3) and Yb3+ ions (1021 ion/cm3) while pumped with a 970 nm diode laser is presented. The red upconversion emission results from a two-photon excitation process. The upconversion emission intensity dependence on the incident pump power shows that the green upconversion luminescence arising from 2H11/2 level is also contributed by the two-photon processes. The values of n-parameter for the 4S3/2 level change from 2.7 to 2.0 during low power excitation and continue decreasing at higher pumping energy. It has been shown that the green upconversion luminescence intensity dependence on the erbium ions content has a sharp maximum at the concentration of 2* 1019 ion/cm3. We attribute the high upconversion luminescence in case of low Er3+ and Tm3+ ions concentrations (about 1018–1016 ion/cm3) to the cooperative energy transfer from Yb–Yb* dimers. The formation of excited dimers is confirmed experimentally by cooperative luminescence band at 495 nm.

Time-resolved excited state dynamics of super-exciplex in the coumarin dye laser

It has been known for a few decades that laser dye, 7-diethylamino 4-methyl coumarin (DAMC) exhibits one absorption and one fluorescence peak but produces dual amplified spontaneous emission (ASE) bands (at 427 and 460 nm) in certain solvents, under high power pulsed laser pumping. The appearance of the new peak manifested only under high pump energy excitation, is attributed to a rare excited state species, called a “superexciplex” (SX). This is a transient excited state bimolecular association in which two excited state molecules get bonded with the help of an unexcited solvent molecule acting as an intermediary. In principle, the formation of excited state species would take a time of the order of a few hundred picoseconds or even nanoseconds. The objective of this paper is to delineate the formation of such super - exciplex employing time resolved ASE spectra where the three-dimensional display gives clearer perspectives. Since the formation of the SX depends on dye concentration, pump energy, and temperature, in the present time-resolved spectroscopy (TRS) paper all the above factors had been studied in some detail.

Pulse-to-pulse spectral noise in a spontaneous parametric down conversion light source

The presence of pronounced chemical signatures of several important molecules and gases in the mid-infrared (mid-IR) spectral region has enabled numerous spectroscopic applications in diverse fields such as environmental monitoring and the life sciences. This has motivated the development of new, efficient light sources and detectors in this spectral region. In this work, we report on the development and characterization of a simple, low-cost, tunable mid-IR light source, covering the 1.45 µm to 3.5 µm spectral region, based on spontaneous parametric down conversion (SPDC) in MgO doped periodically poled lithium niobate (MgO:PPLN). The spectral coverage can be easily extended to 5 µm simply by choosing a crystal with an appropriate poling period. A low repetition rate, passively Q-switched laser provides high-energy pump pulses at 1.03 µm for the SPDC source, resulting in the generation of signal and idler fields. The source is characterized in terms of pulse-to-pulse spectral stability of the generated signal field. Interestingly, a high pulse-to-pulse energy stability does not necessarily lead to high spectral stability. Pulse-to-pulse spectral stability is measured at different pump pulse energies, showing improved spectral stability when operated well above the SPDC threshold.

Single-Mode Polymer Ridge Waveguide Integration of Organic Thin-Film Laser

Organic thin-film lasers (OLAS) are promising optical sources when it comes to flexibility and small-scale manufacturing. These properties are required especially for integrating organic thin-film lasers into single-mode waveguides. Optical sensors based on single-mode ridge waveguide systems, especially for Lab-on-a-chip (LoC) applications, usually need external laser sources, free-space optics, and coupling structures, which suffer from coupling losses and mechanical stabilization problems. In this paper, we report on the first successful integration of organic thin-film lasers directly into polymeric single-mode ridge waveguides forming a monolithic laser device for LoC applications. The integrated waveguide laser is achieved by three production steps: nanoimprint of Bragg gratings onto the waveguide cladding material EpoClad, UV-Lithography of the waveguide core material EpoCore, and thermal evaporation of the OLAS material Alq3:DCM2 on top of the single-mode waveguides and the Bragg grating area. Here, the laser light is analyzed out of the waveguide facet with optical spectroscopy presenting single-mode characteristics even with high pump energy densities. This kind of integrated waveguide laser is very suitable for photonic LoC applications based on intensity and interferometric sensors where single-mode operation is required.

Broadband nanosecond optical parametric chirped-pulse amplification with a double-sliced pump pulse

We developed a two-stage optical parametric chirped-pulse amplification (OPCPA) amplifier with a double-sliced pump pulse. To utilize a single-longitudinal laser pulse with an 8-ns duration and a 532-nm central wavelength as a high-energy pump source efficiently, two 2-ns quasi-rectangular pump pulses were generated by double-slicing the green pulse with two Pockels cells. The energy and spectral width of the amplified laser pulse with an 820-nm central wavelength were maximized by optimizing the phase matching conditions in the OPCPA amplifier via a 3-D simulation. The amplified laser pulse had a broad bandwidth of 120 nm (FWHM) and a high energy of 75 mJ. And the amplified pulse had an energy stability of 2.14% (RMS) on account of the temporal jittering between the single-mode green pulse and the Pockels cells while the single-mode green pump laser had an energy stability of 1.1% (RMS).

Coherence of bulk-generated supercontinuum

We have developed a numerical framework that allows estimation of coherence in spatiotemporal and spatiospectral domains. Correlation properties of supercontinuum (SC) pulses generated in a bulk medium are investigated by means of second-order coherence theory of non-stationary fields. The analysis is based on simulations of individual space–time and space–frequency realizations of pulses emerging from a 5 mm thick sapphire plate, in the regimes of normal, zero, and anomalous group velocity dispersion. The temporal and spectral coherence properties are analyzed in the near field (as a function of spatial position at the exit plane of the nonlinear medium) and as a function of propagation direction (spatial frequency) in the far field. Unlike in fiber-generated SC, the bulk case features spectacularly high degrees of temporal and spectral coherence in both the spatial and spatial-frequency domains, with increasing degrees of coherence at higher pump energies. When operating near the SC generation threshold, the overall degrees of temporal and spectral coherence exhibit an axial dip in the spatial domain, whereas in the far field, the degree of coherence is highest around the optical axis.

An Overview on the Recent Techniques for Improving the Flowability of Crude Oil in Pipelines

Crude oil is considered as a major source of energy all over the world. Midstream refers to the various methods of transportation. Important issues that oil transportation methods face are spills and inadvertent emissions. Therefore, most of the technology developments in transportation methods are aimed at reducing emissions, increasing efficiency, or preventing spills and leaks. Piping systems are the safest and most efficient and cost-effective way for crude oil transportation. The process suffers from serious problems such as: asphaltene and paraffin structures interactions, pipes pressure drop, and high pumping energy consumption. One of the economical important challenges in oil pipeline transportation is to keep the flowability and reduce the pressure drop along the pipe. The current review highlights the recent and most development techniques which have been used to enhance the fluidity of crude oil in pipelines.

Radiative Characteristics of Xe2Cl* Molecules under High-Energy Electron Pumping of Xe–CCl4 and Ar–Xe–CCl4 Gas Mixtures with a Low CCl4 Content

Spontaneous and stimulated emissions of Xe2Cl* triplex molecules upon excitation of Xe–CCl4 gas mixtures with a low CCl4 content by a pulsed high-energy electron beam have been experimentally studied. The electron energy is 150 keV, and the pump current pulse duration and amplitude are 5 ns and 5 A, respectively. Emission of an Xe2Cl excimer molecule in the wavelength range of 430–650 nm is shown to consist of 13 narrow vibrational bands with half-widths Δλ ~ 14 nm peaking at 399, 413, 431, 451, 472, 492, 510.3, 534.9, 540.9, 551.7, 564.4, 581.6, and 603 nm. Under the given pumping conditions, a regime of weakly amplified spontaneous emission is implemented at the energy deposition to the gas of ~200 W/cm3 on the axis of a 50‑mm cell and the electron beam pumping in the wavelength range of 450–550 nm. Spontaneous emission of the 42Г–12Г band of a Xe2Cl* excimer molecule at λmax = 486 nm was amplified by a factor of 60 in a 100‑cm cell under pumping of a dense 3He–Xe–CCl4 gas mixture by the 3He(n, p)3T nuclear reaction products at the energy deposition to the gas of ~5 mJ/cm3 in a cavity with the mirror reflections of ~99.4% (totally reflecting mirror) and 98.5% (output mirror).

Time-resolved, nonequilibrium carrier and coherent acoustic phonon dynamics in (Cd, Mg)Te single crystals for radiation detectors

We present time-resolved nonequilibrium carrier and coherent acoustic phonon dynamics in (Cd, Mg)Te single crystals intended for detection of high-energy x-ray photons. Our (Cd, Mg)Te crystals were grown using a vertical Bridgman method and during the process were doped either with In (a shallow dopant) or Ge (a deep impurity). Next they were cut into platelets and, subsequently, tested as as-grown specimens, or, before testing, long-term annealed in a temperature range of 750 °C–800 °C to improve their crystalline properties. All samples exhibited high resistivities of 109–1010 Ω cm, as required for x-ray detection applications. We have performed femtosecond optical spectroscopy, pump-probe measurements on all samples in both one-color (high-intensity 800 nm pump and low-intensity 800 nm probe) and two-color (high-intensity 400 nm pump and low-intensity 800 nm probe) configurations, and analyzed the results using our carrier dynamics rate-equation model. The model allowed us to perform a comprehensive, time-resolved analysis of relaxation dynamics of photoexcited carriers and investigate the role of carrier traps present in all tested samples. Two-color measurements also allowed us to observe and analyze the propagation of acoustic coherent phonons excited by the high-energy pump pulse. We observed that the dependence of phonon mode frequency, after including a correction of the experimentally measured crystal index of refraction dependence on the probe wavelength, was dispersionless and led to the value for the sound velocity of 3367 m s−1, which is in excellent agreement with the literature data. The intrinsic lifetime of coherent phonons in (Cd, Mg)Te was estimated to be of the order of 10 ns. Finally, we conclude that among our tested samples, the In-doped, annealed (Cd, Mg)Te crystal exhibits the best characteristics for radiation detection applications.

Generation and Nonlinear Self-Addition of Laser Frequencies Upon High-Energy Diode Pumping of Er:BaY2F8 Crystals

Special features of laser line generation upon high-energy diode pumping of Er:BaY2F8 crystals are investigated. The UV and visible laser lines are effectively formed via nonlinear self-addition of frequencies of induced Er3+ lines at 541 and 553 nm with the corresponding frequencies of IR Er3+ lines upon pumping of the Er:BaY2F8 crystals with a diode laser beam having a wavelength of 457 nm.

Two photon induced amplified spontaneous emission at low threshold from Styryl 7 dye incorporated DNA template

Studies on biophysical interactions between DNA-surfactant complexes and dye molecules are necessary to fully exploit its potential in optoelectronic devices. In this work investigations on nonlinear optical absorption and amplified spontaneous emission (ASE) of Styryl 7 dye (LDS 750) incorporating DNA-CTMA (deoxyribonucleic acid blended with cationic surfactant molecule, cetyltrimethyl-ammonium chloride) and PMMA (Poly methyl methacrylate) is reported. The nonlinear optical studies on the sample carried out using Z scan technique exhibits reverse saturable absorption with DNA -CTMA complex but with PMMA the sample behaves as a saturable absorber. We observed ASE at low pump energy for Styryl 7–DNA-CTMA film, when excited with a pulsed nanosecond Nd: YAG laser (λ = 532 nm) whereas ASE was not observed from dye incorporated with PMMA even with high pump energy. ASE characteristics were studied as a function of excitation energy density for the evaluation of threshold energy and exponential gain coefficient. The enhanced fluorescence and low threshold for ASE make Styryl 7 dye –DNA template a promising candidate for novel optoelectronic applications.

Nonlinear distortion and spatial dispersion of intense terahertz generation in lithium niobate via the tilted pulse front technique

We systematically investigate the influences of the input infrared spectrum, chirp, and polarization on the emitted intense terahertz spectrum and spatial dispersion in lithium niobate via optical rectification. The terahertz yield and emission spectrum depend on both the chirp and spectrum of the input pump laser pulses. We also observe slight non-uniform spatial dispersion using a knife-edge measurement, which agrees well with the original predictions. The possible mechanism is the nonlinear distortion effect caused by high-energy laser pumping. Our study is very important and useful for developing intense terahertz systems with applications in extreme terahertz sciences and nonlinear phenomena.

Amplified luminescence and nonaxial radiation modes in the active elements of high-power diode side-pumped solid-state lasers

A model system of two differential rate equations is proposed to describe the temporal characteristics of the radiation of a solid-state laser with high-energy pumping. Using a laser head with a YAG:Nd active element and a side-pumped laser diode array unit as an example, a method is discussed of determining the excitation levels of the active elements at which the amplified luminescence and the nonaxial (stray) lasing modes begin to manifest themselves in the output radiation dynamics all the way to the limitation of the maximum pulse energy generated by a solid-state laser in the Q-switched regime. The proposed approach to analyzing the role of the processes associated with the formation and evolution of amplified luminescence fluxes and nonaxial (stray) lasing modes in the active media can also be applied to other types of laser radiators.

Optimization of deterministic controls for a cooling radiant wall coupled to a PV array

Thermally activated building systems (TABS) can work as thermal energy storage (TES) systems, which are useful in shifting the energy use of space cooling and heating in buildings. The present study analyses and optimizes simple deterministic control concepts for radiant wall supplied by a heat pump for cooling purposes. First, the “solar” concept was studied, which was focused on exploiting the output of a photovoltaic (PV) array. Secondly, a “peak load shifting” concept exploiting the low electricity cost and high heat pump energy efficiency during night periods was evaluated. The results showed that the “solar” concept saved between 57% and 95% in comparison to a conventional control in different PV installed capacities. Moreover, the optimized “peak load shifting” concept had lower operation cost than the conventional control with most of the PV configurations proposed. Therefore, the study showed that the investment in the PV array was fully harnessed only with specific controls. Furthermore, the “solar” control concepts were found to help achieving the goals of net-zero energy buildings by maximising self-consumption of renewable energies in the building, as well as reducing the total imported/exported energy.