Indirect Pumping Research Articles

Emission behaviors from ZnO microwire pumped CsPbBr3 perovskite microwire.

Perovskite semiconductor materials have attracted significant attention in the fields of photovoltaics and luminescence due to their excellent photoelectric properties, such as high carrier mobility, high absorption coefficient, and high fluorescence quantum yield. In particular, low-dimensional metal-halide perovskite microcrystalline materials have been reported to exhibit low-dimensional lasing phenomena and laser devices due to their high gain and widely tunable bandgap. In this Letter, one-dimensional (1-D) ZnO microwires with their ultraviolet lasing emissions are utilized as an excitation source to pump CsPbBr3 microwire on hybrid ZnO-CsPbBr3 microscale structures. At higher excitation, the amplified spontaneous emission (ASE) behaviors from CsPbBr3 microwire are realized with ultralow threshold by indirect pumping from the ZnO lasing emission for the first time, to the best of our knowledge. In comparison, the ASE behaviors from the CsPbBr3 microwire directly pumped by Nd:YAG Q-switched laser and continuous wave laser are also performed at room temperature. There are also no multimode lasing behaviors observed. The paper provides a new method to achieve a low threshold on-chip microlaser by a high-quality perovskite micro-nano structure.

Electrically driven organic laser using integrated OLED pumping

Organic semiconductors are carbon-based materials that combine optoelectronic properties with simple fabrication and the scope for tuning by changing their chemical structure1–3. They have been successfully used to make organic light-emitting diodes2,4,5 (OLEDs, now widely found in mobile phone displays and televisions), solar cells1, transistors6 and sensors7. However, making electrically driven organic semiconductor lasers is very challenging8,9. It is difficult because organic semiconductors typically support only low current densities, suffer substantial absorption from injected charges and triplets, and have additional losses due to contacts10,11. In short, injecting charges into the gain medium leads to intolerable losses. Here we take an alternative approach in which charge injection and lasing are spatially separated, thereby greatly reducing losses. We achieve this by developing an integrated device structure that efficiently couples an OLED, with exceptionally high internal-light generation, with a polymer distributed feedback laser. Under the electrical driving of the integrated structure, we observe a threshold in light output versus drive current, with a narrow emission spectrum and the formation of a beam above the threshold. These observations confirm lasing. Our results provide an organic electronic device that has not been previously demonstrated, and show that indirect electrical pumping by an OLED is a very effective way of realizing an electrically driven organic semiconductor laser. This provides an approach to visible lasers that could see applications in spectroscopy, metrology and sensing.

Toward Nonepitaxial Laser Diodes.

Thin-film organic, colloidal quantum dot, and metal halide perovskite semiconductors are all being pursued in the quest for a wavelength-tunable diode laser technology that does not require epitaxial growth on a traditional semiconductor substrate. Despite promising demonstrations of efficient light-emitting diodes and low-threshold optically pumped lasing in each case, there are still fundamental and practical barriers that must be overcome to reliably achieve injection lasing. This review outlines the historical development and recent advances of each material system on the path to a diode laser. Common challenges in resonator design, electrical injection, and heat dissipation are highlighted, as well as the different optical gain physics that make each system unique. The evidence to date suggests that continued progress for organic and colloidal quantum dot laser diodes will likely hinge on the development of new materials or indirect pumping schemes, while improvements in device architecture and film processing are most critical for perovskite lasers. In all cases, systematic progress will require methods that can quantify how close new devices get with respect to their electrical lasing thresholds. We conclude by discussing the current status of nonepitaxial laser diodes in the historical context of their epitaxial counterparts, which suggests that there is reason to be optimistic for the future.

On-Chip Ultralow-Threshold Tunable CdSSe Nanobelt Lasers Excited by the Emission of Linked ZnO Nanowire.

The integration of optical waveguide and on-chip nanolasers source has been one of the trends in photonic devices. For on-chip nanolasers, the integration of nanowires and high antidamage ability are imperative. Herein, we realized the on-chip ultralow-threshold and wavelength-tunable lasing from alloyed CdSSe nanobelt chip that is excited by the emission from linked ZnO nanowires. ZnO nanowire arrays are integrated into CdSSe nanobelt chips by the dry transfer method. A one-dimensional (1D) ZnO nanowire forms high-quality optical resonators and serves as an indirect pumping light to stimulate CdSSe nanobelt chips, and then wavelength-tunable lasing is generated with the ultralow threshold of 3.88 μW. The lasing mechanism is quite different than direct excitation by nanosecond laser pulse and indirect pumping by ZnO emission. The ZnO-CdSSe blocks provide a new solution to realize nanowire lasing from linked nanowires rather than direct laser pumping and thus avoid the light direct damage under general nanosecond laser excitation.

Spin-noise spectroscopy of a noise-squeezed atomic state

Spin noise spectroscopy is emerging as a powerful technique for studying the dynamics of various spin systems also beyond their thermal equilibrium and linear response. Here, we study spin fluctuations of room-temperature neutral atoms in a Bell-Bloom type magnetometer. Driven by indirect pumping and undergoing a parametric excitation, this system is known to produce noise-squeezing. Our measurements not only reveal a strong asymmetry in the noise distribution of the atomic signal quadratures at the magnetic resonance, but also provide insight into the mechanism behind its generation and evolution. In particular, a structure in the spectrum is identified which allows to investigate the main dependencies and the characteristic timescales of the noise process. The results obtained are compatible with parametrically induced noise squeezing. Notably, the noise spectrum provides information on the spin dynamics even in regimes where the macroscopic atomic coherence is lost, effectively enhancing the sensitivity of the measurements. Our work promotes spin noise spectroscopy as a versatile technique for the study of noise squeezing in a wide range of spin based magnetic sensors.

Continuous wave and rhenium disulphide-based Nd:GdTaO4 laser under direct pumping

In this paper, a continuous wave (CW) and rhenium disulphide (ReS2) passively Q-switched Nd:GdTaO4 laser under the pump at 879 nm was firstly reported. CW output characteristics under indirect 808 nm pumping and direct 879 nm pumping were investigated, respectively. By comparison with indirect pumping, the direct pump at 879 nm effectively relieved thermal lenses effect. Under direct pumping, the maximum CW output power was 5.1 W with slope efficiencies (ηs) of 48.6%. In the indirect pumping a maximum CW output power of 4.3 W was obtained, corresponding to ηs of 41.2%. A ReS2 nanosheet was utilized to achieve the pulsed laser output. At absorbed pump power of 7.1 W, the highest repetition rate, narrowest pulse width, maximum average output power, single pulse energy, and peak power reached 67 kHz, 230 ns, 1 W, 14.93 μJ, and 64.9 W, respectively.

Study of emission and optical interaction in the UO2–Nd system doped in zinc phosphate glass

The study of the interaction between optically excited ions that enhances emission from fluorescence cations can be useful in industrial application and scientific research. The sensitization of active rare earth ions by uranyl ion can be particularly useful for improving the pumping efficiency of solid-state lasers. Keeping the above facts in mind, non-radiative energy transfer from optically excited UO2++ to Nd3+ has been studied in zinc phosphate glass by keeping donor concentration fixed and varying acceptor concentration at room temperature. From the experimental investigation, it has been observed that the emission intensity of the donor (UO2++) decreases with increasing acceptor (Nd3+) concentration resulting in a non-radiative energy transfer from UO2++ to Nd3+. According to Fong–Diestler’s and Forster and Dexter’s theories, the dipole–dipole transfer mechanism is found to be dominant in the present system and phonon-assisted energy transfer is also suggested. At different acceptor concentrations, various parameters necessary for the quantitative study, e.g., donor–acceptor distances (DD→A), transfer efficiencies (η), energy transfer probabilities (Pda) and critical transfer distances (R0), have been calculated. In the present study, we report that uranyl ion is particularly useful as an indirect pumping source for Nd3+.

Halide Perovskite Lateral Heterostructures for Energy Routing Based Photonic Applications

AbstractSemiconductor heterostructures hold the promise for developing novel integrated devices with on‐demand photonic and optoelectronic properties. Herein, the perovskite lateral heterostructures in forms of microplates and microwires are fabricated by precise control of two‐step atmospheric pressure chemical vapor deposition course and the unique optical properties are demonstrated for the first time. The comprehensive spectroscopic and elemental mapping characterizations reveal the core‐shell‐like configuration of the individual heterostructure, which features the fascinating energy routing nature. Taking advantage of the effective photon recycling and the energy transfer processes, the record‐low threshold (≈3.5 µJ cm−2) lasing and the indirect pumping induced lasers from the single micro‐heterostructure are demonstrated. Moreover, the distinctive optical waveguides with propagation length independent output spectra from the microwire heterostructure are realized. These findings represent a significant advance in developing novel and functional optoelectronic devices by engineering the perovskite heterostructure.

Continuous wave and rhenium disulfide passively Q-switched Nd:GdLaNbO4 laser under direct pumping

A continuous wave (CW) and passively Q-switched 1.06μm Nd:GdLaNbO4 laser under direct 879 nm pumping is firstly reported in this paper. The CW output power and slope efficiency varied from 4.50 W and 45.6% to 6.55 W and 50.0% when the indirect pumping of 808 nm was changed to the direct pumping of 879 nm. Furthermore, the beam quality was also improved significantly. For the CW Nd:GdLaNbO4 laser, as is known to all that the highest output power with excellent beam quality was obtained. In the Q-switched operation, rhenium disulfide (ReS2) synthetized by chemical vapor deposition (CVD) method was employed as a saturable absorber (SA). The optical properties and atom force microscope (AFM) image of ReS2 were measured and recorded to characterize it. A maximum average output power with 312 mW, a narrowest pulse width with 400 ns, and a highest repetition rate with 147 kHz were obtained under the direct 879 nm pumping.

RAINWATER HARVESTING (RWH) INSTALLATION FOR BUILDINGS: A SYSTEMATIC REVIEW AND META-ANALYSIS APPROACH

Rainwater that falls upon a roof surface which are collected and transferred to the storage facility for later use is a method known as Rainwater Harvesting (RWH). This method is a step towards conserving the public drinking water where the demand continues to grow worldwide. In Malaysia, there is a huge potential of rainwater harvesting based on the available rainfall amount. Even so, the existing RWH design guideline in Malaysia lacks the technical specification regarding congruousness of RWH installation method with the physical characteristic of the building. Therefore, systematic literature review and meta-analysis were done to identify and understand the suitability between the types of RWH installation system with the building’s physical characteristic. The main objective of this study is to review the existing articles from year 2000 to the present on the installation systems used in RWH for non-potable purposes. The RWH installation system, types of building and building characteristics used in the previous studies will be evaluated in order to understand the suitability or regularity of the combinations. This review uses the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) as reviewing method. The systematic review process involved four stages which are identification, screening, eligibility and included. The sources of this review are Science Direct and Google Scholar. Results show there are three types of RWH installation system that were identified namely Gravity Fed System (GFS), Indirect Pumping System (IPS) and Direct Pumping System (DPS). DPS is commonly applied for non-potable purposes in residential, commercial and educational buildings. Small yard area, sloping site condition and types of soft landscape will affect the type of RWH installation system to be used. The result can be used to determine the suitability of the RWH installation system for different types and characteristics of a building.

Exciton energy transfer in hybrid organics – Semiconductor nanostructure

We consider a hybrid heterostructure containing an inorganic quantum well in close proximity with an organic material as overlayer. The resonant optical pumping of Frenkel exciton can lead to an efficient indirect pumping of Wannier excitons. As organic material in such hybrid structure we consider crystalline tetracene. In tetracene diffusion length of singlet exciton diffusion is strongly dependent on temperature. We have obtained the exact analytical solution of diffusion equation for exciton in organics at different temperatures defining different diffusion lengths of excitons. Then we have included in consideration Coulomb interaction between organics and QW. It was shown that this interaction multiple increases effectiveness of transfer from organics to QW in the same way as it was predicted early in our publications for inverse transfer from QW to organics. The effectiveness of energy transfer in hybrid with tetracene was calculated by definite method for two selected temperatures that opens possibility to operate in full region of temperatures. Temperature dependence of energy transfer in organics opens a new possibility to turn on and off the indirect pumping due to energy transfer from the organic subsystem to the inorganic subsystem. This varying pumping may be used for experimental investigating of different nonlinear effects.

Dynamic nuclear polarization

Abstract Dynamic nuclear polarization, or DNP, refers to the increase of the polarization of nuclear spins in condensed matter, liquid or solid, coupled with electronic spins at low relative concentration, by inducing radio or microwave transitions at frequencies close to the electronic resonance frequency in the external magnetic field. Another described method relies on indirect optical pumping methods at temperatures close to room temperature for the nuclear polarization of rare gases. The various mechanisms of DNP are described in physical terms. This is followed by a succinct description of its main applications in various domains of physics, in chemistry and in medicine.

Cost-Optimal Heat Exchanger Network Synthesis Based on a Flexible Cost Functions Framework

In this article an approach to incorporate a flexible cost functions framework into the cost-optimal design of heat exchanger networks (HENs) is presented. This framework allows the definition of different cost functions for each connection of heat source and sink independent of process stream or utility stream. Therefore, it is possible to use match-based individual factors to account for different fluid properties and resulting engineering costs. Layout-based factors for piping and pumping costs play an important role here as cost driver. The optimization of the resulting complex mixed integer nonlinear programming (MINLP) problem is solved with a genetic algorithm coupled with deterministic local optimization techniques. In order to show the functionality of the chosen approach one well studied HEN synthesis example from literature for direct heat integration is studied with standard cost functions and also considering additional piping costs. Another example is presented which incorporates indirect heat integration and related pumping and piping costs. The versatile applicability of the chosen approach is shown. The results represent designs with lower total annual costs (TAC) compared to literature.

Exciton Energy Transfer in Hybrid Organics—Semiconductor Nanostructure

We consider a hybrid heterostructure containing an inorganic quantum well in close proximity with organic material as overlayer. The resonant optical pumping of Frenkel exciton can lead to an efficient indirect pumping of Wannier excitons. As organic material in such a hybrid structure, we consider crystalline tetracene. In tetracene, the singlet exciton energy is close to twice the one of triplet exciton state and singlet exciton fission into two triplets can be efficient. This process in tetracene is thermally activated and we investigate here how the temperature-dependent exciton energy transfer affects the functional properties of hybrid organic-inorganic nanostructures. We have obtained the exact analytical solution of diffusion equation for organics at different temperatures defining different diffusion lengths of excitons. The effectiveness of energy transfer in hybrid with tetracene was calculated by definite method for two selected temperatures that open possibility to operate in full region of temperatures. Temperature dependence of energy transfer opens a new possibility to turn on and off the indirect pumping due to energy transfer from the organic subsystem to the inorganic subsystem.

Metallized nanoporous anodic alumina films and their applications

The optimal conditions of the aluminum electrochemical anodization and electrochemical and chemical metallization were determined. Metallized nanoporous anodic alumina (NAA) films with ultrahigh/average/low density of pores were obtained using the optimal conditions. The physical and chemical properties of the obtained NAA films were studied by high-resolution scanning electron microscopy and the reflective interference spectra in a wavelength range of 235–735 nm. Possible applications of the obtained NAA films are in micro/nanoscale lasers with indirect electrical pumping by laser diodes; optical interferometric chemical nanosensors; and the selective interference coloration and protection of the metal surface.

926 nm laser operation in Nd:GdNbO4 crystal based on 4F3/2 → 4I9/2 transition

926 nm laser operation in a Nd:GdNbO4 crystal based on quasi-three-level 4F3/2 → 4I9/2 transition is reported, for the first time to our best knowledge. An average output power of 393 mW at 926 nm under 879 nm LD pumping is obtained with a slope efficiency of 33.3% and an optical-to-optical efficiency of 26.0%. The slope efficiency with respect to absorbed pump power is estimated to be 47.7%. Comparison between output characters of 926 nm laser under direct and indirect pumping is conducted. The average output power at 926 nm under 808 nm LD pumping reaches 305 mW with an optical-to-optical efficiency of 16.1%.

Indirect pumping bell–bloom magnetometer**Project supported by the Natural Science Foundation of Shanghai (Grant No. 16ZR1402700), the National Natural Science Foundation of China (Grant No. 91636102), and the National Key Research and Development Program of China (Grant No. 2016YFA0302000).

When the ground state hyperfine splitting of alkali metal vapor atoms is well optically resolved, the spin coherence on one hyperfine sublevel can be generated directly or indirectly by pumping the same or the other sublevel respectively. We experimentally studied the pump power dependence of the field response of a Bell-Bloom magnetometer for the two pumping schemes in a paraffin coated 87Rb vapor cell. We find that although the maximum field response is achieved by combining the two pumping schemes, indirect pumping alone can do nearly as good while being much simpler to operate. We have achieved a sensitivity of 100 fT/Hz1/2 with a single indirect pump at room temperature.

Cs 5D5/2–6F 728 nm Laser Spectroscopy with Single Pumping Laser**Supported by the National Natural Science Foundation of China under Grant No 91436210.

The sub-Doppler absorption laser spectroscopy at 728 nm transition from the 5 state to the state of cesium with linewidth near 10 MHz is first experimentally performed with indirect pumping from the ground state 6 to the state by a 455.5 nm diode laser. Using a 455.5 nm diode laser as an indirect pump laser, several excited states will be populated due to spontaneous decay from the state. We first implement the sub-Doppler absorption laser spectroscopy at 728 nm from the 5 state to the state when Cs atoms within thermal glass cell decay to the 5 state. Due to velocity transfer effect, the hyperfine structure of 5 shows a mixed and complicated pattern but very clear structure when the 455.5 nm pumping laser is counter-propagating (or co-propagating) with the 728 nm probing laser.

Theoretical Model of a Thulium-Doped Fiber Amplifier Pumped at 1570 nm and 793 nm in the Presence of Cross Relaxation

The static behavior of a thulium-doped fiber amplifier (TDFA) operating around 2 μm region at different pump wavelengths is investigated in this paper. A theoretical model is built up by solving a set of rate and propagation equations with considering the effect of cross relaxation mechanism. The developed model provides the influences of the amplified spontaneous emission noise, seed wavelength, and the thulium-doped fiber length into the TDFA performance. Simulation results indicate that the TDFA performance with pump at 1570 nm is more efficient than pump at 793 nm for core pumped thulium-doped silica fiber. Our findings show that the maximum gain reaches up to 30 dB with a 27 dBm pump power when a -10 dBm seed wavelength at 1840 nm is used. In contrast to indirect pumping at 793 nm, only 22 dB maximum gain is achieved under the same conditions. The model is also validated with previous experimental work. Our simulations are consistent with the experimental findings with small variations.

Green Stimulated Emission Boosted by Nonradiative Resonant Energy Transfer from Blue Quantum Dots.

Thanks to their tunability and versatility, the colloidal quantum dots (CQDs) made of II-VI semiconductor compound offer the potential to bridge the "green gap" in conventional semiconductors. However, when the CQDs are pumped to much higher initial excitonic states compared to their bandgap, multiexciton interaction is enhanced, leading to a much higher stimulated emission threshold. Here, to circumvent this drawback, for the first time, we show a fully colloidal gain in green enabled by a partially indirect pumping approach assisted by Förster resonance energy transfer process. By introducing the blue CQDs as exciton donors, the lasing threshold of the green CQDs, is reduced dramatically. The blue CQDs thus serve as an energy-transferring buffer medium to reduce excitation energy from pumping photons in a controlled way by injecting photoinduced excitons into green CQDs. Our newly developed colloidal pumping scheme could enable efficient CQD lasers of full visible colors by a single pump source and cascaded exciton transfer. This would potentially pave the way for an efficient multicolor laser for lighting and display applications.