Nonlinear Optical Switching Research Articles

Third-order nonlinear optical adjusting behavior in azobenzene metal complexes

The third-order nonlinear optical (NLO) materials with stimuli-responsive properties have received extraordinary attention due to their controllable photophysical properties. In this work, two attractive metal complexes third-order NLO switches, which are far superior to congeneric optical switches in terms of their performance conversion, versatility, and fast response, were successfully designed and synthesized. The test of their third-order NLO properties proves that the metal complexes exhibit reverse saturable absorption and self-defocusing refraction. After light irradiation, the third-order NLO behavior turns quickly into self-focusing refraction. The relation between the molecular structures and the third-order NLO properties was investigated via1H nuclear magnetic resonance and ultraviolet-visible absorption. The results show that the metal ions have a significant influence on the NLO behavior and reveal the origin of third-order NLO properties via Z-scan determinations, pump-probe technology, and density functional theory calculations. These metal complexes can be used as third-order NLO switches with excellent fatigue resistance and broaden the application range of third-order NLO materials with adjustable performances.

Vibrational sum-frequency generation study of molecular structure, sterical constraints and nonlinear optical switching contrast of mixed alkyl-azobenzene self-assembled monolayers

AbstractSelf-assembled monolayers (SAMs) of azobenzene (AB) functionalized alkyl thiols on gold diluted with simple alkyl thiols provide a straightforward way to photochromic surfaces with high and tunable photoswitching efficiency.Trans-cisisomerization of the AB molecule changes the physical properties of the surface, including the nonlinear optical (NLO) response. Vibrational sum-frequency generation (VSFG) spectroscopy as a nonlinear type of laser spectroscopy offers surface- and orientation-sensitive insight into the molecular structure of mixed SAMs. In this study, VSFG as well as ultraviolet-visible (UV/Vis) spectroscopy has been employed to investigate the morphology, molecular structure, and NLO response of mixed SAMs with systematically varied surface composition. Methylazobenzene (MeAB) has been used as the molecular switch with the methyl substituent serving as orientational VSFG marker. Both short-chain and long-chain alkyl thiol co-ligands have been used to gain insight into the interplay between SAM structure and sterical constraints that are known to limit the free switching volume. Underlining the dominating role of sterical effects for controlling photochromic properties, a strong inhibition of the photoswitching efficiency and NLO response has been observed for the SAMs with an alkyl thiol co-ligand long enough to spatially extend into the layer of the MeAB chromophore. Overall, with <12% signal change, the relative NLO switching contrasts remained low in all cases. VSFG spectral trends clearly revealed that the presumably higher photoswitching efficiency upon dilution with the co-ligand is counteracted by a loss of structural order of the chromophore.

Molecule-based nonlinear optical switch with highly tunable on-off temperature using a dual solid solution approach

Nonlinear optical switches that reversibly convert between on/off states by thermal stimuli are promising for applications in the fields of photoelectronics and photonics. Currently one main drawback for practical application lies in the control of their switch temperature, especially for the temperature range near room temperature. By mixed melting treatment, here we describe an alloy-like nonlinear optical switch with tunable switch temperature via a dual solid solution approach within the coordination polymer system. We initially prepare a coordination polymer (i-PrNHMe2)[Cd(SCN)3], which functions as a high-contrast thermoresponsive nonlinear optical switch originating from a phase transition at around 328 K. Furthermore, by taking advantage of a synergistic dual solid solution effect, the melt mixing of it with its analogue (MeNHEt2)[Cd(SCN)3], which features an unequal anionic chain templated by an isomeric ammonium, can afford coordination polymer solid solutions with switch temperatures that are tunable in a range of 273–328 K merely by varying the component ratio.

Two Rare-Earth Molecular Ferroelectrics with High Curie Temperatures, Large Spontaneous Polarization, Switchable Second Harmonic Generation Effects, and Strong Photoluminescence.

Smart multifunctional molecular ferroelectrics bearing high Curie temperatures and diverse excellent physical properties, such as second harmonic generation (SHG) responses, luminescence, and semiconductivity, among others, have significant applications but have seldom been documented. Herein, the rare-earth metals Nd and Pr are introduced into a simple molecular system (nBu4 N)3 [M(NO3 )x (SCN)y ] (nBu4 N= tetrabutyl ammonium, M=rare-earth metal, nBu=CH3 CH2 CH2 CH2 ), and two new multifunctional molecular ferroelectrics are obtained: (nBu4 N)3 [Nd(NO3 )4 (SCN)2 ] (1) and (nBu4 N)3 [Pr(NO3 )4 (SCN)2 ] (2). Their distinct heat and dielectric anomaly dependence on temperature verifies that compounds 1 and 2 experience high-temperature para-ferroelectric phase transitions at 408 and 413 K, respectively. Strikingly, both molecular ferroelectrics possess large spontaneous polarization with Ps values of 9.05 and 8.50 μC cm-2 , respectively, and are further characterized by the appearance of multiple intersecting non-180° domains and polarization switching behavior. In particular, compounds 1 and 2 show good stability with only a small decrease in SHG intensity after switching cycles, suggesting that they have great potential for application in nonlinear optical (NLO) switches. Simultaneously, the rare-earth compounds 1 and 2 present bright yellow-red and bright green fluorescence, respectively, at room temperature.

Three-Dimensional Perovskite Methylhydrazinium Lead Chloride with Two Polar Phases and Unusual Second-Harmonic Generation Bistability above Room Temperature

Formation of noncentrosymmetric three-dimensional (3D) lead halide perovskites has been a widely sought after goal because the polar structure opens up new vistas to properties of these materials, e.g., improved charge separation for photovoltaics arising from ferroelectric order. Here, we report growth and unique properties of a new highly distorted 3D perovskite, methylhydrazinium lead chloride (CH3NH2NH2PbCl3, MHyPbCl3). This perovskite crystallizes in polar P21 structure at room temperature, which consists of two types of PbCl6 octahedra: one weakly and another strongly deformed. The unusual deformation of every second perovskite layer is forced by the large size of methylhydrazinium cations and the ability of NH2+ terminal groups of methylhydrazinium cations to form coordination bonds with Pb2+ metal centers. On heating, MHyPbCl3 undergoes a phase transition at 342 K into another polar Pb21m phase with ordered organic cations. Temperature-resolved second-harmonic generation (TR-SHG) measurements confirm acentricity of both phases and show that second-harmonic response is enhanced for the high-temperature Pb21m phase. This intriguing property of MHyPbCl3 has been employed to demonstrate an unprecedented kind of quadratic nonlinear optical switching in which a second-harmonic response is switched between a room-temperature, low-SHG state and a high-temperature, high-SHG state. X-ray diffraction shows that enhancement of polar properties is due to rearrangement of the perovskite’s organic substructure. There is a clear pyrocurrent peak, but switching of the electric polarization could not be observed. Optical studies showed that MHyPbCl3 is a wide-bandgap material with a bandgap of 3.4 eV (365 nm). At low temperatures, it exhibits weak UV emissions at 362 and 369 nm as well as a strong broadband white emission.

Solid-State Nonlinear Optical Switch with the Widest Switching Temperature Range Owing to Its Continuously Tunable Tc.

Interest on the nonlinear optical (NLO) switches that turn on/off the second-harmonic generation (SHG) triggered by the external stimulus (such as heat) have continuously grown, especially on the solid-state NLO switches showing superior stability, reversibility, and reproducibility. Herein, we discover (NH4)2PO3F, as an entirely new solid-state NLO switch showing outstanding switch contrast and reversibility as well as strong SHG intensity (1.1 × KH2PO4 (KDP)) and high laser-induced damage threshold (2.0 × KDP), undergoes a unique first-order phase transition that originates from a reversible hydrogen-bond rearrangement and needs to overcome an energy barrier. Accordingly, we put forward a strategy to continuously modify such an energy barrier by reducing the number of hydrogen bonds per unit cell via an isoelectronic replacement of NH4+ by K+ with a similar size yet incapability of providing any hydrogen bond. Consequently, Kx(NH4)2-xPO3F (x = 0-0.3) exhibiting excellent switching performance are obtained. Remarkably, Kx(NH4)2-xPO3F not only realizes a continuously tunable Tc spanning from 270 to 150 K, representing the widest NLO switching temperature range ever known but also indicates the first solid-state NLO switch example with continuous Tc. Intrinsically, such a Tc decline depends on the weakening degree of the hydrogen-bonding interactions in the unit cell. These new insights will shed useful light on the future material design and open new application possibilities.

Photostimulated nonlinear optical switching materials based on CdBr0·95Cl0.1 nanocrystalline layers

Abstract New types of crystalline materials based on CdBr0·95Cl0.1 nanolayers have been fabricated. Due to the layered structure, it is possible to achieve nanolayers by cleaving layers of CdBr2 single crystals. These layers anisotropy opens a principal opportunity for fabricating thin CdBr0·95Cl0.1 nanocrystals with a thickness up to several nanometers without additional treatment. We have prepared the samples within a 3–30 nm thickness range. The phototreatment has been performed by bicolor coherent Nd: YAG laser with wavelengths 1540 nm/770 nm. The third-harmonic generation (THG) was detected for a fundamental 20 ns Er-glass laser beam at wavelength 1540 nm with a frequency reception of ∼10 Hz. The phototreatment was done for 2–3 min and was controlled by cw He–Ne laser-induced diffraction patterns. The maximal photoinduced changes have been found for the thinnest film possessing thickness about 3 nm. The THG effect at 1540 nm was maximal at ambient temperature. The effect is explained within a framework of the phenomenological consideration. The principal role of the space electron charge density anisotropy is discussed.

Nonlinear optical absorption switching behavior of BaTiO3 in asymmetric microcavity

In this paper, an asymmetric 1-D photonic microcavity with BaTiO3 as defect has been fabricated using RF magnetron sputtering technique. Open aperture Z-scan shows enhancement in nonlinear absorption of BaTiO3 due to strong field confinement around the defect layer. We further report the switching behavior in nonlinear absorption from reverse saturable absorption to saturable absorption in response to the angle tuning of the sample. The transfer matrix simulation results further support the cavity defect in asymmetric photonic crystal confine the photon and thereby enhancing nonlinear optical phenomena.

One-dimensional Sn(iv) hydroxide nanofluid toward nonlinear optical switching

A new chemical method is developed for the preparation of a unique one-dimensional (1D) Sn(iv) hydroxide nanofluid.

Nonlinear optical switching and all-figures of merit in Bi2S3-xSex/PMMA nanocomposite films investigated by Z scan under visible CW laser

Bi2S3-xSex/poly(methyl methacrylate) (PMMA) nanocomposite films were prepared using microwave assisted synthesis with different compositions of x. Crystal structure, surface morphology, and optical properties were investigated to characterize the prepared nanocomposite films. The crystallinity and optical band gap of the prepared Bi2S3-xSex/PMMA were affected by x. The prepared samples showed a blue shift in the absorption edge. The laser power dependent nonlinear refraction and absorption of Bi2S3-xSex/PMMA nanocomposite films were investigated by using the Z-scan technique. The optical nonlinearity of the nanocomposite films exhibited switchover from negative nonlinear refraction to positive nonlinear refraction to negative nonlinear refraction effects, and from saturable absorption to reverse saturable absorption to saturable absorption with an increase and decrease in the composition. An interesting all-optical figure of merit was reported to assess the nanocomposite films for a practical device. It was calculated that the device all-figures of merit were based on the nonlinear response, which is important for the all-optical switching device. The results demonstrate that the optimized all-optical figures of merit can be achieved by adjusting the composition and input laser power, which can be used for the design of different all-photonic devices, and the results of nonlinear switching behavior can open new possibilities for using the nanocomposite films in laser Q-switching and mode-locking.

Novel inorganic aromatic mixed-valent superalkali electride CaN3Ca: an alkaline-earth-based high-sensitivity multi-state nonlinear optical molecular switch.

Focusing on innovative high-performance single-pole double-throw nonlinear optical (NLO) molecular switches, two C3v configurations (1 and 3) and one D3h configuration (2) of bipyramidal CaN3Ca have been obtained by using quantum mechanical methods. Not only are 1, 2, and 3 alkaline-earth-based aromatic superalkalis, but they are also interesting electrides. The salt-like electronic structures of e-Ca2+N33-Ca2+ (1) and Ca2+N33-Ca2+e- (3) with localized redox centres are rare inorganic Robin-Day class II-type structures, and e0.5-Ca2+N33-Ca2+e0.5- (2) with a delocalized structure is a class III-type mixed-valent superalkali electride. Under a small external electric field of ±0.0110 a.u. (0.565 V Å-1), the short-distance hopping of Ca atoms in CaN3Ca from the D3h configuration with in-plane aromaticity to each C3v configuration with out-of-plane aromaticity brings about the long-range transfer of half an electron from one Ca atom to another. And, subsequently, a large dipole moment (μ0) and remarkable static first hyperpolarizability (β0) occur. μz and βzzz range from 0 (D3h, off form) to -12.1 or 12.1 D (C3v, on forms) and from 0 (D3h, off form) to -19 428 or 19 428 a.u. (C3v, on forms), respectively. These extremely large differences in μz and βzzz values between the D3h and each of the C3v configurations confirm the potential of these inorganic aromatic Robin-Day-type superalkali electrides for applications in high-sensitivity multi-state nonlinear optical switches.

Theoretical investigation of perfect fullerene-like borospherene Ih-B20 protected by alkaline earth metal: multi-layered spherical electride molecules as electric field manipulated second-order nonlinear optical switches.

For the challenge of stabilizing a fullerene-like borospherene, a perfect fullerene-like borospherene B20 with Ih symmetry is stabilized theoretically for the first time by selected 12 η5 (pentahapto)-Mg atoms capped on the 12 B5 pentagons, forming an exohedral metalloborospherene Ih Mg12&B20 molecule. Owing to the pull-push electron transfer relay, the molecule is converted to a spherical electride molecule (Mg2+)12&B2018- + 6e- with multiexcess electrons and high-valent B2018- polyanion with a full-shell electronic configuration, performing the stabilization of the fullerene-like B20 cage. Furthermore, we embed the metal M atom in the B20 cage, forming new endohedral electride molecules (Mg2+)12&(Mn+@B2018-) + (6 + n)e- (M = Li, n = 1 and Mg, n = 2). The embedded atom M increases the excess electron number. Notably, these electride molecules possess two different types of superatomic characteristics, exhibiting the behavior of an electron reservoir. Moreover, a compound (Mg12&B20)2O is designed and obtained, so Mg12&B20 might serve as a nano-building block. In addition, the Mg12&B20 and Mg12&(Mg@B20) electride molecules are efficient external electric field-manipulated nonlinear optical (NLO) switches with high sensitivity and reversibility. The embedding metal atom in the B20 cage can also serve as a new strategy to manipulate NLO switching.

Study on the Solid-State Nonlinear Optical Switch with the Widest Tunable Temperature Range

Study on the Solid-State Nonlinear Optical Switch with the Widest Tunable Temperature Range

Pulse nonlinear optical switching in plasmonic structures

We study switching operation in a plasmonic coupler using fs-pulses. Simulations using the finite difference time-domain method (FDTD) are carried out showing how the output changes as the pulse energy increases raising from zero to a maximum. Both cases of neglecting and realistic losses are considered in order to compare. The work is intended to explore the use of pulses for all-optical signal processing in a potentially interesting system for integrated photonics at the nanometric scale.

不同浓度Ti:Bi2Te3的调Q光纤激光器

Nonlinear optical switch based on two-dimensional material is the core device of Q-switched fiber laser. The concentration of two-dimensional material optical switch will directly affect its nonlinear optical absorption characteristics, thus changing the time-domain characteristics of the pulse. Therefore, the influence of two-dimensional material concentration on Q-switched optical pulse is studied, and a saturable absorption optical switch based on Ti: Bi2Te3 with different concentration is made through experiments. The influence of Ti: Bi2Te3 concentration on nonlinear optical absorption characteristics is analyzed, and the relationship between the modulation depth, pulse width, repetition frequency and single pulse energy of Q-switched optical pulse with different concentration Bi2Te3 is obtained. Finally, the Ti: Bi2Te3 concentration is optimized for the resonator parameters. When the pump power is 71 MW, the central wavelength is 1560 nm, the pulse width is 8 μ s, the repetition frequency is 14.2 kHz, the average output power is 2.15 MW, and the corresponding single pulse energy is 151.4 NJ.

Adjusting the Third-Order Nonlinear Optical Switch Performance Based on Azobenzene Derivatives

Adjusting the Third-Order Nonlinear Optical Switch Performance Based on Azobenzene Derivatives

Giant and Multistage Nonlinear Optical Response in Porphyrin-Based Surface-Supported Metal-Organic Framework Nanofilms.

Benefitting from the strong intrinsic nonlinear optical (NLO) property of the individual porphyrin molecule, the integration of porphyrin molecules into tightly aligned arrays may lead to intuitively promising high-performance materials of tailorable NLO effect. In order to verify this speculation, we prepare crystalline and highly oriented porphyrin-based surface-supported metal-organic framework nanofilms (SURMOFs) and then characterize their NLO performance. Results reveal that porphyrin-based SURMOFs exhibit the highest saturable absorption (SA) yet recorded with a third-order NLO absorption coefficient up to -10-3 cm/W, about 7 orders stronger than porphyrin solvents in which the porphyrin molecules are disordered, under a certain excitation strength. Further increasing the excitation strength shows that the NLO absorption property of the porphyrin-based SURMOFs can be effectively modulated from SA to reverse saturable absorption, followed by a reemerging SA. The multiple-stage NLO switching is assigned to the interplay of simultaneous one-photon SA, two-photon absorption, and two-photon SA effects. The superior and modulatable NLO property as well as the designable and ordered crystalline structure suggest that porphyrin-based SURMOFs might be employed as a new class of high-performance NLO materials with potential applications in novel optical switches or logic gates to realize the all-optical information process.

Ultrabroadband plasmonic induced transparency in random metamaterial with nanocavity

A three-dimensional (3D) metamaterial is very easily assembled as a stacked structure with two physical vapor deposition layers, one metallic and one dielectric, and with a spray of gold nanospheres (GNS) on top. The first planar metasurface is a semicontinuous gold nanocomposite which is transformed into a “dark metasurface” when embedded in a dielectric nanocavity. The second metasurface is a radiative mirror composed of the self-arranged GNS at the nanocavity's surface. The two random metasurfaces are strongly coupled through their near field inside the nanocavity. Plasmonic induced transparency is observed at normal incidence over a very wide spectral bandwidth of a few hundred terahertz from the visible to the NIR. The induced transmission maximum occurs in a spectral region where the scattering cross section from the GNS is maximum. Critical coupling between the two metasurfaces is achieved with multiple deposits of GNS and the transition from induced transparency to induced absorption is experimentally observed. Such a simple 3D metamaterial could be used to enhance non-linear optical effects, optical switching and slow light generation in the NIR.

Hopping of Li@AR (AR = Benzene and Naphthalene) between Electride and Lithium Salt Configurations Brings Considerably Different First Hyperpolarizabilities: Candidate for High-Performance Nonlinear Optical Molecular Switches

For Li@AR (AR = benzene and naphthalene), it is reported that hopping of Li atom under the external electric field between electride and lithium salt configurations brings decidedly different charg...

Long-Range Charge Transfer Driven by External Electric Field in Alkalides M–LCaL–M (M = Li or Na, L = All-cis 1,2,3,4,5,6-Hexafluorocyclohexane): Facially Polarized Janus-Type Second Order Nonlinear Molecular Optical Switches

Alkalides with large nonlinear optical (NLO) responses exhibit broad applications in the electro-optical device field. In the present work, based on alkali (Li and Na) in conjunction with alkaline-...