High-energy Oscillator Research Articles

Quantized Microcavity Polariton Lasing Based on InGaN Localized Excitons.

Exciton-polaritons, which are bosonic quasiparticles with an extremely low mass, play a key role in understanding macroscopic quantum effects related to Bose-Einstein condensation (BEC) in solid-state systems. The study of trapped polaritons in a potential well provides an ideal platform for manipulating polariton condensates, enabling polariton lasing with specific formation in k-space. Here, we realize quantized microcavity polariton lasing in simple harmonic oscillator (SHO) states based on spatial localized excitons in InGaN/GaN quantum wells (QWs). Benefiting from the high exciton binding energy (90 meV) and large oscillator strength of the localized exciton, room-temperature (RT) polaritons with large Rabi splitting (61 meV) are obtained in a strongly coupled microcavity. The manipulation of polariton condensates is performed through a parabolic potential well created by optical pump control. Under the confinement situation, trapped polaritons are controlled to be distributed in the selected quantized energy sublevels of the SHO state. The maximum energy spacing of 11.3 meV is observed in the SHO sublevels, indicating the robust polariton trapping of the parabolic potential well. Coherent quantized polariton lasing is achieved in the ground state of the SHO state and the coherence property of the lasing is analyzed through the measurements of spatial interference patterns and g(2)(τ). Our results offer a feasible route to explore the manipulation of macroscopic quantum coherent states and to fabricate novel polariton devices towards room-temperature operations.

High-repetition-frequency, high-energy mid-wave infrared ZnGeP2 MOPA system

A high-repetition-frequency and high-energy ZnGeP2 master oscillator power amplifier (ZGP-MOPA) system was demonstrated. The pump source was a 2097 nm Ho:YAG laser with maximum average power of about 140 W and repetition frequency of 2 kHz. Using this pump source, the ZGP-MOPA system obtained a mid-wave infrared laser with a maximum average power of 58.9 W and pulse width of 20.1 ns, corresponding to the pulse energy and peak power of 29.5 mJ and 1.5 MW. By adjusting the divergence of seed source to match the divergence of pump source, the beam quality factor M 2 of the ZGP-OPA was 3.9 × 3.7 (horizontal directions × vertical directions), the M 2 of the signal was 2.7, and the M 2 of the idler was 2.8. The corresponding maximum average power and pulse energy were 53.3 W and 26.7 mJ.

Step-wise changes in the excited state lifetime of [Eu(D2O)9]3+ and [Eu(DOTA)(D2O)]- as a function of the number of inner-sphere O-H oscillators.

Lanthanide luminescence is dominated by quenching by high-energy oscillators in the chemical environment. The rate of non-radiative energy transfer to a single H2O molecule coordinated to a Eu3+ ion exceeds the usual rates of emission by an order of magnitude. We know these rates, but the details of these energy transfer processes are yet to be established. In this work, we study the quenching rates of [Eu(D2O)9]3+ and [Eu(DOTA)(D2O)]- in H2O/D2O mixtures by sequentially exchanging the deuterons with protons. Flash freezing the solutions allows us to identify species with various D/H contents in solution and thus to quantify the energy transfer processes to individual OH-oscillators. This is not possible in solution due to fast exchange in the ensembles present at room temperature. We conclude that the energy transfer processes are accurately described, predicted, and simulated using a step-wise addition of the rates of quenching by each O-H oscillator. This documents the sequential increase in the rate of the energy transfer processes in the quenching of lanthanide luminescence, and further provides a methodology to identify isotopic impurities in deuterated lanthanide systems in solution.

Highly NIR-II luminescent erbium porphyrinoids

Erbium (Er[Formula: see text] ion exhibits efficient broadband emission at 1.53 [Formula: see text]m (4f optical transition 4I13/2 [Formula: see text] 4I15/2), which is promising to achieve better clarity and deeper penetration depth for biological imaging. However, because of the relatively low luminescent level (4I[Formula: see text], ca. 6500 cm[Formula: see text] and the tendency of being facile to be quenched by high-energy oscillators such as N-H, C-H, or O-H groups, achieving small molecular Er complexes with intense NIR-II luminescence has remained a challenge. In this work, a series of Er[Formula: see text] complexes of porphyrinoids and [Formula: see text]-perhalogenated derivatives caped with auxiliary deuterated Kläui ligands were prepared, namely X-1-Er, X-2-Er and X-cis/trans-3-Er (X = H, F, Cl, Br). Interestingly, most of the [Formula: see text]-perhalogenated Er complexes displayed high overall quantum yields ([Formula: see text] 0.1% in CH2Cl2 and CD2Cl2) and long lifetimes ([Formula: see text] 8 [Formula: see text]s in CH2Cl2 and 11 [Formula: see text]s in CD2Cl2).

Room‐Temperature Exceptional‐Point‐Driven Polariton Lasing from Perovskite Metasurface

AbstractExcitons in lead bromide perovskites exhibit high binding energy and high oscillator strength, allowing for a strong light‐matter coupling regime in the perovskite‐based cavities localizing photons at the nanoscale. This opens up the way for the realization of exciton‐polariton Bose–Einstein condensation and polariton lasing at room temperature – the inversion‐free low‐threshold stimulated emission. However, polariton lasing in perovskite planar photon cavities without Bragg mirrors has not yet been observed and proved experimentally. In this study, perovskite metasurface is employed, fabricated with nanoimprint lithography, supporting so‐called exceptional points to demonstrate the room‐temperature polariton lasing. The exceptional points in exciton‐polariton dispersion of the metasurface appear upon optically pumping in the nonlinear regime in the spectral vicinity of a symmetry‐protected bound state in the continuum providing high mode confinement with the enhanced local density of states beneficial for polariton condensation. The observed lasing emission possesses high directivity with a divergence angle of 1° over one axis. The employed nanoimprinting approach for solution‐processable large‐scale polariton lasers is compatible with various planar photonic platforms suitable for on‐chip integration.

Recent advance of high-energy ultrafast mode-locked oscillators based on Mamyshev mechanism with different starting modes

The nonlinear effect of fiber limits the further increase in pulse energy, and Mamyshev oscillator shows outstanding advantages in managing nonlinearity in waveguide medium, which is now associated with high peak power and high pulse energy. The potential applications of these laser sources based on Mamyshev mechanism have facilitated aggressive research and innovative ideas by researchers around the world. Here, we focus on the mode-locked principle and starting dynamics of Mamyshev oscillator. The review of Mamyshev technology is summarized from two starting modes of seed source injection and self-starting. Initial research and significant progress in this field, plus new insights and challenges of Mamyshev oscillator for ultrafast fiber laser technology are analyzed.

The Generation of 1.2 μJ Pulses From a Mamyshev Oscillator Based on a High Concentration, Large-Mode-Area Yb-Doped Fiber

We demonstrate a high-energy and high-average power Mamyshev oscillator based on a high performance large-mode-area step-index germanosilicate-cladding Yb-doped fiber. The oscillation of higher-order modes is effectively suppressed by employing appropriate intracavity spatial mode filtering, allowing significant scaling of single pulse energy. The laser directly generates a nearly diffraction-limited beam with an average power of 17 W operating at the fundamental repetition rate of 14.01 MHz, corresponding to a pulse energy of 1.2 μJ. The pulses could be externally dechirped to ∼58 fs, leading to a peak power of ∼13 MW. To the best of our knowledge, this is the highest pulse energy with sub-100 fs duration ever obtained directly from a mode-locked fiber oscillator.

High-energy Q-switched 16-core tapered rod-type fiber laser system.

High-energy Q-switched master oscillator power amplifier systems based on rod-type 4 × 4 multicore fibers are demonstrated, achieving energy up to 49 mJ in ns-class pulses. A tapered fiber geometry is tested that maintains low mode order in large multimode output cores, improving beam quality in comparison to a similar fiber with no taper. The tapered fiber design can be scaled both in the number of amplifying cores and in the dimensions of the cores themselves, providing a potential route toward joule-class fiber lasers systems.

Over 80 nJ Sub-100 fs All-Fiber Mamyshev Oscillator

A high-energy Mamyshev oscillator was experimentally demonstrated with an all polarization-maintaining 10/125 fiber configuration, which is initiated by an external pulse radiation. A maximum output power of 787.3 mW with the single pulse energy of 83.5 nJ was achieved at a repetition rate of 9.43 MHz. The pulse width was compressed to 56 fs with a grating pair, corresponding to a peak power of 1.15 MW considering the insertion loss of the grating pair. The evolution of the pulse properties versus the enhancement of the energy was examined and an excellent long-time stability was verified. It is believed that such a compact all-fiber ultrafast oscillator could be a promising source for practical applications such as material processing, medicine, nonlinear microscopy and so on.

To Configure Thin Layer Sonoelectrochemical Experiments

In a thin layer sonoelectrochemistry cell, a simple high frequency (ultrasonic) oscillator placed a short distance from a flat electrode surface focuses ultrasound at the electrode solution interface to impact rates of interfacial processes. Traditionally, sonoelectrochemistry in a bulk fluid uses high energy oscillators such as sonic horns that drive turbulent cavitation. In the thin layer arrangement, no cavitation is visible but rates of interfacial electrochemical events are enhanced. Effective thin layer sonoelectrochemistry requires attention to properties of the solvent and electrode material, frequency and amplitude of the oscillator, and the alignment and distance between the faces of the oscillator and the electrode. When properly configured, the thin layer sonocell enhances energy delivered to the fluid electrode interface through constructive interference. Because there is no cavitation, voltammetric morphologies remain similar to those in quiescent electrolytes. Here, conditions to set up an effective thin layer sonoelectrochemical cell are described.

Room-Temperature Upconversion in a Nanosized {Ln15} Molecular Cluster-Aggregate.

The successive absorption of low-energy photons to the accumulation of the intermediate excited states leading to higher energy emission is still a challenge in molecular architectures. Contrary to low-phonon solids and nanoparticles, the rational construction of molecular systems containing an excess of donor atoms in relation to acceptor ones is far from trivial. Moreover, the vibrations caused by high-energy oscillators commonly present on coordination compounds result in serious drawbacks on molecular upconversion. To overcome these limitations, we demonstrate that upconversion can be achieved even at room temperatures through the use of molecular cluster-aggregates (MCAs). To achieve the upconverted emission, we synthesized a MCA containing 15 lanthanide ions, {Er2Yb13}, ensuring an excess of donor atoms. With the excitation on the ytterbium ion, the characteristic green and red emissions from erbium were obtained at room temperature. To prove the mechanism behind the upconversion process, four other compositions were synthesized and studied, namely, {Y13Er2}, {Y10Er5}, {Er10Yb5}, and {Y10Er1Yb4}. Upconversion quantum yield values on the order of 10-3% were obtained, values 100000 times higher than for previously reported lanthanide-based molecular upconverting systems. The presented methodology is an interesting approach to address a fine composition control and harness the upconversion properties of nanoscale molecular materials.

All-fiber pulsed laser generation of 25.5 mJ and solution of parasitic oscillation.

A Q-switched, high-energy pulsed master oscillator power amplifier fiber laser utilizing the lab-built 100/400 µm double-cladding Yb-doped fiber is demonstrated. After two-stage amplification, the pulse energy was boosted to 25.5 mJ, for an average power of 510 W at a repetition of 20 kHz, yielding a slope efficiency of approximately 72.8%; the pulse duration was approximately 140 ns, and corresponding peak power was 182.1 kW. What is more, the limitation of further promotion of pulse energy was proposed: the threshold-like parasitic oscillation, which was determined by the injecting power, repetition, and fiber length, was the main restriction on power scaling in ultra-high-energy systems. Efficient solutions were proposed to suppress the parasitic oscillation by experimentally studies.

Electronic structure and photophysics of a supermolecular iron complex having a long MLCT-state lifetime and panchromatic absorption

Exploiting earth-abundant iron-based metal complexes as high-performance photosensitizers demands long-lived electronically excited metal-to-ligand charge-transfer (MLCT) states, but these species suffer typically from femtosecond timescale charge-transfer (CT)-state quenching by low-lying nonreactive metal-centered (MC) states. Here, we engineer supermolecular Fe(II) chromophores based on the bis(tridentate-ligand)metal(II)-ethyne-(porphinato)zinc(II) conjugated framework, previously shown to give rise to highly delocalized low-lying 3MLCT states for other Group VIII metal (Ru, Os) complexes. Electronic spectral, potentiometric, and ultrafast pump-probe transient dynamical data demonstrate that a combination of a strong σ-donating tridentate ligand and a (porphinato)zinc(II) moiety with low-lying π*-energy levels, sufficiently destabilize MC states and stabilize supermolecular MLCT states to realize Fe(II) complexes that express 3MLCT state photophysics reminiscent of their heavy-metal analogs. The resulting Fe(II) chromophore archetype, FeNHCPZn, features a highly polarized CT state having a profoundly extended 3MLCT lifetime (160 ps), 3MLCT phosphorescence, and ambient environment stability. Density functional and domain-based local pair natural orbital coupled cluster [DLPNO-CCSD(T)] theory reveal triplet-state wavefunction spatial distributions consistent with electronic spectroscopic and excited-state dynamical data, further underscoring the dramatic Fe metal-to-extended ligand CT character of electronically excited FeNHCPZn. This design further prompts intense panchromatic absorptivity via redistributing high-energy absorptive oscillator strength throughout the visible spectral domain, while maintaining a substantial excited-state oxidation potential for wide-ranging photochemistry--highlighted by the ability of FeNHCPZn to photoinject charges into a SnO2/FTO electrode in a dye-sensitized solar cell (DSSC) architecture. Concepts enumerated herein afford opportunities for replacing traditional rare-metal-based emitters for solar-energy conversion and photoluminescence applications.

Effect of Nonradiative Transitions on the Upconversion Properties of YVO4:Yb, Er Nanoparticles

The results from a comparative analysis of the emission spectra of upconversion YVO4:Yb, Er nanoparticles synthesized in sizes ranging from 10 nm to 1 μm are used to discuss the contribution from high-energy oscillators on the surfaces of nanoparticles to the nonradiative energy transfer between Er3+ ion levels, and to the formation of the red emission band at 660 nm.

A new brilliant red emitting Eu(III) ternary complex and its transparent flexible and photostable poly(urethane) hybrid thin film for optoelectronic applications

A new Eu(III) complex, [Eu(tta)3DPA] (1) (tta = 2-Thenoyltrifluoroacetone and DPA = 2,2′-Dipyridylamine) has been synthesized and characterized by analytical and spectroscopic techniques. Photoluminescence (PL) studies of complex 1 were performed in the solid state and in a range of solvents to assess the effect of high energy oscillators on the PL and the results were correlated to radiative (AR) and non-radiative (ANR) decay rates. The theoretically values are in good agreement with the experimental results. A flexible transparent thin film was developed by embedding complex 1 into poly(urethane) (PU) polymer. PU@1 was characterized by EDX, SEM, AFM, and static contact angle measurement. Mechanical properties of the PU@1 were determined. PL studies of the hybrid material displayed typical narrow emission similar to complex 1 (FWHM ≈ 3.48 nm). Thermal, photostability (under UV radiation) and Laser properties of complex 1 and PU@1 were also investigated.

Transparent NaGdF4:Nd3+ colloid prepared by femtosecond laser ablation as a liquid laser medium

By using femtosecond-pulsed laser to ablate the larger nanosized target in liquid, stable transparent NaGdF4:Nd3+ colloid has been successfully fabricated. The X-ray diffraction (XRD) spectra reveal that the colloidal nanoparticles remain the hexagonal phase crystal structure of NaGdF4 powder target. SEM and TEM images results indicate that the size of these colloidal nanoparticles decreases sharply. FT-IR results indicate that the number of O–H and C–H groups on the surface is decreased. The emission properties of the colloid have been investigated using 794nm pulsed wave laser radiation, and it is found that the colloid exhibits near-infrared luminescent emissions in the spectral range of 850–1400nm, and the decay time for 4F3/2→4I11/2 (1058nm) Nd3+ ion transitions is lengthened than that of powder target, these results are probably due to the reduced nonradiative relaxation assisted by high energy oscillators. The observed near-infrared emission of the stable transparent colloid makes it a good candidate for application in liquid laser.

Roadmap to high-energy square pulses in anomalous dispersion fiber lasers

Dissipative soliton resonance (DSR) is a soliton formation where the energy in a dissipative system becomes infinite. In the anomalous dispersion regime, this energy is not limited by the soliton area theorem. Since this phenomenon is wave breaking free, it can be useful in designing fiber lasers generating pulses with relatively high energies. Based on this principle, we have demonstrated the emission of high energetic square pulses from Er:Yb double-clad passively mode-locked fiber lasers using different mode-locking mechanisms. We first show the evolution of pulse width, energy and peak power by varying the pumping power of the amplifier, then we control separately the characteristic of the output square pulse by assigning each one to an amplifier. Experimental results exhibit record energies in fiber lasers up to 10 uJ. Full Text: PDF ReferencesW. Chang, A. Ankiewicz, J.M Soto Crespo and N. Akhmediev, " Dissipative soliton resonances", Phys. Rev. A 78, 023830 (2008). CrossRef P. Grelu, W. Chang, A. Ankiewicz, J. M. Soto-Crespo, and N. Akhmediev, "Dissipative soliton resonance as a guideline for high-energy pulse laser oscillators", J. Opt. Soc. Am. B 27, 2336 (2010). CrossRef X. Wu, D. Y. Tang, H. Zhang, and L. M. Zhao, "Dissipative soliton resonance in an all-normal-dispersion erbium-doped fiber laser", Opt. Express 17, 5580 (2009). CrossRef G. Semaan, F. Ben Braham, M. Salhi, Y. Meng, F. Bahloul, and F. Sanchez, "Generation of high energy square-wave pulses in all anomalous dispersion Er:Yb passive mode locked fiber ring laser", Opt. Express 24, 8399 (2016). CrossRef K. Krzempek, "Dissipative soliton resonances in all-fiber Er-Yb double clad figure-8 laser", Opt. Express 23, 30651 (2015). CrossRef L. Mei et al., "Width and amplitude tunable square-wave pulse in dual-pump passively mode-locked fiber laser", Opt. Lett. 39, 3235 (2014). CrossRef X. Zhang et al., "Square-wave pulse with ultra-wide tuning range in a passively mode-locked fiber laser", Opt. Lett. 37, 1334 (2012). CrossRef K. Krzempek, J. Sotor, and K. Abramski, "Compact all-fiber figure-9 dissipative soliton resonance mode-locked double-clad Er:Yb laser", Opt. Lett. 41, 4995-4998 (2016). CrossRef G. Semaan, F. Ben Braham, J. Fourmont, M. Salhi, F. Bahloul, and F. Sanchez, "10uJ dissipative soliton resonance square pulse in a dual amplifier figure-of-eight double-clad Er:Yb mode-locked fiber laser", Opt. Lett. 41, 4767 (2016). CrossRef K. Krzempek and K. Abramski, "Dissipative soliton resonance mode-locked double clad Er:Yb laser at different values of anomalous dispersion", Opt. Express 24, 22379-22386 (2016). CrossRef

ChemInform Abstract: Excited State Decay of Cyclometalated Polypyridine Ruthenium Complexes: Insight from Theory and Experiment

AbstractReview: 176 refs.

Taming Lanthanide-Centered Upconversion at the Molecular Level

Considered at the beginning of the 21th century as being incompatible with the presence of closely bound high-energy oscillators, lanthanide-centered superexcitation, which is the raising of an already excited electron to an even higher level by excited-state energy absorption, is therefore a very active topic strictly limited to the statistical doping of low-phonon bulk solids and nanoparticles. We show here that molecular lanthanide-containing coordination complexes may be judiciously tuned to overcome these limitations and to induce near-infrared (NIR)-to-visible (VIS)-light upconversion via the successive absorption of two low-energy photons using linear-optical responses. Whereas single-ion-centered excited-state absorption mechanisms remain difficult to implement in lanthanide complexes, the skillful design of intramolecular intermetallic energy-transfer processes operating in multimetallic architectures is at the origin of the recent programming of erbium-centered molecular upconversion.

High-energy femtosecond amplifier-similariton Er-doped fiber oscillator.

We demonstrated high-energy femtosecond amplifier-similariton oscillators with predominant Er-doped fibers of normal dispersion. Stably mode-locked pulses of ~3 ps, 33 nJ were produced at 720 mW pump power, while a double-pass grating pair of 36% efficiency compressed the pulses to 156 fs and 47 kW peak power (a new record). Broad mode-locked spectra supporting transform-limited pulsewidths down to 60 fs were obtained by adjusting the intracavity waveplates and filter. Continuous wave (CW) mode-locked pulses up to 53 nJ were generated by increasing the pump power to 1.5 W and by introducing significant spectral phase modulation via an intracavity pulse shaper. However, weak subpulses or pedestal could arise along with increased shot-to-shot fluctuation under this extreme operation mode.