High Nonlinear Optical Response Research Articles

Influence of the surface modification of BaTiO3 nanoparticles by hydrolyzed chitosan obtained from shrimp exoskeletons on the optical response intensity of the second harmonic

Ferroelectric nanoparticles, due to their high non-linear optical response, are of considerable practical interest for their use as nanoprobes for the study of biological materials by multiphoton microscopy methods. To prevent toxic effects, it is necessary to modify the surface using biocompatible polymers. Here we report the results of the study on the effect of surface modification of BaTiO3 nanoparticles with hydrolyzed chitosan obtained from shrimp exoskeletons (Penaeus vannamei). It was found that increasing of the hydrolyzed chitosan concentration in the solution during surface modification from 1 to 3% leads to a significant reduction in nanoparticle agglomeration, while the intensity of the second harmonic generation changes insignificantly.Graphical abstract

Analyzing cases of significant nondynamic correlation with DFT using the atomic populations of effectively localized electrons

Quantum multireference effects are associated with degeneracies and near-degeneracies of the ground state and are critical to a variety of systems. Most approximate functionals of density functional theory (DFT) fail to properly describe such effects. A number of diagnostics have been proposed to estimate in advance the reliability of a given single-reference solution in this respect. Some of these diagnostics, however, lack size-consistency while remaining computationally expensive. In this work, we propose the DFT method of atomic populations of effectively localized electrons (APELE) as a novel diagnostic in this vein. It is compared with existing diagnostics of nondynamic correlation on select exemplary systems. The APELE method is on average in good agreement with the popular T1 index, while being size-consistent and less costly. It becomes particularly informative in cases involving bond stretching or bond breaking. The APELE method is applied next to organic diradicals like the bis-acridine dimer and the p-quinodimethane molecule which possess unusually high nonlinear optical response, and to the reaction of ethylene addition to Ni dithiolene. Our results for this reaction are consistent with the T1 diagnostics and in addition, shed some light on the degree of d-electron localization at the Ni center.

Optimization on preparation conditions to improve the nonlinear optical response of ZnO/TiO2/ZrO2 ternary nanocomposites under continuous-wave laser irradiation

Sol-gel method under ultrasonic treatment was utilized to synthesize ZnO/TiO2/ZrO2 ternary nanocomposites. The synthesized samples were characterized using the X-ray diffraction (XRD) analysis, Field Emission Scanning Electron Microscopy (FESEM), UV–VIS, and Photoluminescence (PL) spectroscopy to determine and confirm the successful synthesis of ZnO/TiO2/ZrO2 ternary nanocomposites. The calcination time, aging time, calcination temperature, and duration of ultrasonic irradiation were selected as variable parameters to optimize the nonlinear optical response of nanocomposites under continuous-wave laser irradiation using the Z-scan setup. The results suggest that ZnO/TiO2/ZrO2 ternary nanocomposites with a high third-order nonlinear optical response are potential materials that can be advantageous for photonics application purposes. The application of the statistical analysis shows that the optimum condition for the preparation procedure to achieve the highest nonlinear optical parameters for ZnO/TiO2/ZrO2 ternary nanocomposites can be obtained by selection of a calcination time of 4 h, an aging time of 24 h, calcination temperature of 400 °C, and 30 min of ultrasonic irradiation.

Highly accurate DFT investigation for triggering the ultra-strong static and dynamic nonlinear optical properties of superalkali doped aminated graphdiyne (NH2-GDY) donor-π-acceptor (D-π-A) quantum dots

Keeping in mind the desirability of novel two-dimensional materials with an ultra-high nonlinear optical (NLO) response for the fabrication of optoelectronic devices, we have investigated nine complexes by doping superalkalis (M2X; M = Li, Na, K and X = F, Cl, Br) onto the novel aminated graphdiyne (NH2-GDY) quantum dots. The geometric, electronic and NLO responses (static and dynamic) of the M2X doped aminated graphdiyne (M2X@NH2-GDY) complexes have been systematically investigated using density functional theory (DFT) computations. All the superalkalis are preferably oriented on the triangular large porous site of NH2-GDY containing extensive delocalized π-conjugated electrons and interact via an intermolecular π-electron donor–acceptor (D-π-A) process. The lithium and potassium-containing superalkali doped complexes exhibit high structural stability due to their large interaction energies. The change in the electronic properties of the M2X doped NH2-GDY quantum dots is investigated by analyzing the NBO charge transfer, vertical ionization energies (VIEs), HOMO-LUMO energy gaps and density of states spectra. TD-DFT calculations show ultra-high transparency of these complexes in the ultraviolet region. The strong NLO characteristics of the designed complexes are demonstrated by their high static and dynamic hyperpolarizability values. Among all the nine complexes, the K2F@NH2-GDY, K2Cl@NH2-GDY and K2Br@NH2-GDY complexes possess exceptionally high βo values: 1.16 × 104, 1.06 × 104 and 1.02 × 104 au, respectively, owing to the large atomic radius and high atomic number of the potassium metal atoms. The frequency-dependent NLO responses, Electro-Optical Pockels Effects (EOPE) and Second Harmonic Generation (SHG) are analyzed to investigate the dynamic NLO response. It is revealed that the K2X@NH2-GDY complexes also exhibit exceptionally high dynamic NLO responses (107 or 108 au) at 1064 nm wavelength. Our present research not only highlights the significance of superalkali doping on aminated graphdiyne quantum dots but also indicates that the K2X@NH2-GDY complexes are potentially important for next-generation optoelectronic devices.

Connecting effect on the charge transport and nonlinear optical properties of heteronanotubes

Carbon/boron nitride heteronanotubes are now at the centre of experimental and theoretical studies because of their tunable properties and diverse applications. Herein, we investigate the charge transport and optical properties of carbon/boron nitride hybrid single- and double-walled nanotubes on the basis of first-principles calculations. Our results reveal that the C/BN heterojunctions with radial junctions parallel (horizontal) to the tube axis have more effects than the perpendicular (vertical) junctions on the charge transport properties of heteronanotubes. Furthermore, we find that the nonlinear optical response can be meaningfully controlled by altering the C/BN content and junction arrangement. In double-walled coaxial heteronanotubes, the interwall interaction is also found to increase the electron and hole transport rates noticeably and to have a major effect on the first hyperpolarizabilities of C/BN heteronanotubes. In contrast with coaxial carbon nanotubes, where the inner constituent is totally shielded by the outer tube, in our studied C/BN coaxial heteronanotubes, the inner shell is only partially shielded by the outer constituent. This study suggests a strategy to high-efficient design heteronanotubes with high charge transport properties and tunable nonlinear optical responses. Moreover, the designed C/BN heteronanotubes can discrete electrons and holes, suggesting their application in solar cell materials.

Enhanced non-linear optical response of calix[4]pyrrole complexant based earthides in the presence of oriented external electric field

We report here rationally designed alkaline earthides using calix[4]pyrrole complexant. Alkali metal atoms are intercalated into calix[4]pyrrole while alkaline earth metals are kept outside the cavity to form M+(calix[4]pyrrole)M- (M+ = Li, Na & K; M- = Be, Mg & Ca). Under the action of four N atoms, the s valence electron of the alkali metal atoms overflows from the bottom of the cup to becomes excess electrons and enwraps the alkaline earth metal forming negative charge on alkaline earth metal. Nine complexes with general formula, M+(calix[4]pyrrole)M- (M+ = Li, Na and K; M- = Be, Mg and Ca) are designed and their geometric, electronic and nonlinear optical (NLO) properties are studied in detail. The alkaline earthide identities of the designed compounds are determined by distribution of electron densities in highest occupied molecular orbitals (HOMOs) and natural bond orbital (NBO) analyses. Presence of negative charges and localization of HOMOs on alkaline earth metals in all these complexes shows the alkaline earthide nature of these complexes. The spectra of partial density of states (PDOS) further confirm the presence of excess electrons on alkaline earth metals. These alkaline earthides show considerably high nonlinear optical responses with the first hyperpolarizabilities (βo) up to 1.98x104 au. Such high βo values are attributed to the presence of excess electron on alkaline earth metals. Moreover, their low transition energies from 2.06 to 3.87 eV reveal the susceptible and diffuse nature of excess electron. We also calculated the NLO response of designed complexes under the influence of external electric field of strength 0.001 a.u and found that NLO response of Li+[Calix4pyrrole]Ca- has increased from 1.90 × 104 a.u to 8.19 x106 a.u. We expect that our work may inspire experimental chemists to explore synthetic, chemical and physical characterization of these new alkaline earthides.

Li@C60 thin films: characterization and nonlinear optical properties.

Organic materials have attracted considerable attention in nonlinear optical (NLO) applications as they have several advantages over inorganic materials, including high NLO response, and fast response time as well as low-cost and easy fabrication. Lithium-containing C60 (Li@C60) is promising for NLO over other organic materials because of its strong NLO response proven by theoretical and experimental studies. However, the low purity of Li@C60 has been a bottleneck for applications in the fields of solar cells, electronics and optics. In 2010, highly purified Li@C60 was finally obtained, encouraging further studies. In this study, we demonstrate a facile method to fabricate thin films of Li@C60 and their strong NLO potential for high harmonic generation by showing its comparatively strong emission of degenerate-six-wave mixing, a fifth-order NLO effect.

Li4EPc: A metallo‐organic electride comprising metal‐nitrogen bonds

AbstractAn in silico design of a new metallo‐organic electride, containing metal‐nitrogen bonds, namely, Li4EPc, with high non‐linear optical (NLO) properties (βtotal = 6.382 × 104 au) is presented. Density functional theory (DFT)‐based computation has revealed the thermodynamic stability of Li42+ cluster encapsulated in EPc host moiety where EPc is an extended phthalocyanine system. Natural bond orbital (NBO) analysis is performed to study the bonding nature of the aforementioned species. We have also performed atoms in molecules (AIM) analysis to confirm the presence of an isolated electron at the interstitial tetrahedral hollow formed by three‐dimensional Li42+ cluster attached with EPc ligand. Linear and NLO properties of the designed electride have been analyzed by polarizability () and first hyperpolarizability calculations (βtotal). Frequency dependent first hyperpolarizability, second harmonic generation (SHG), electro‐optic Pockel's effect (EOPE) have also been computed. Furthermore, we report the hydrogen adsorption potential of each Li atom in Li4EPc system. The result shows that two H2 molecules can be adsorbed per lithium atom leading to a total of eight H2 molecules adsorbed by Li42+ cluster through physisorption process. This work provides a new insight into designing a stable metallo‐organic electride (Li4EPc) with high NLO response which also can be used as an efficient hydrogen storage material.

Giant femtosecond nonlinear optical response in bi-metallic GO nanocomposites for photonic applications

Graphene based 2D materials after suitable modification may results into materials with strong nonlinear optical (NLO) responses. Here, incorporation of Au, and Ag nanoparticles (NPs) in graphene oxide (GO) nanosheet (GO_Au_Ag) is carried out for restructuring of its electronic bands. Reshuffling in the electronic band-to-band transitions and their relaxation process is achieved resulting into achievement of high NLO response in GO_Au_Ag than those of pure GO nanosheets, graphene quantum dot (GQD), and nitrogen doped GQD (N-GQD), by fs Z-scan technique. GO, GQD, and N-GQD, shows only two-photon absorption (2PA), with two times larger absorption coefficient (β) in N-GQD than that of GO and GQD. Interestingly, GO_Au_Ag nanocomposite exhibits simultaneous 2PA and three-photon absorption (3PA) under the excitation of the fs laser pulses. In the presence of prolongated relaxation time and transfer of charge between GO and metal’s state through excited state absorption (ESA), GO_Au_Ag showed a larger β value than N-GQD and the giant third order nonlinear susceptibility (χ (3)) of ∼10−9 (esu). Furthermore, GO_Au_Ag sample shows the optical limiting threshold of only 4.6 μJ/cm2, smaller than that of N-GQD.

Hybrid nanocomposite film provides FWM and Fabry Perot Filter: Towards multi-wavelength fiber laser generation in 1 µm region

We report on the demonstration of a multi-wavelength ytterbium-doped fiber laser (YDFL) by exploiting a nanocomposite film to act as both a Fabry-Perot (FP) filter and a nonlinear material inside the ring cavity. The proposed filter is formed by combining an FP structure based on a large core diameter single-mode fiber (SMF) with a nanocomposite film. The nanocomposite film was prepared by coating gold nanostars with zinc-oxide nanorods/multi-walled carbon nanotubes (ZnO-NRs@Au-NSs/MWCNTs) embedded into polyvinyl alcohol (PVA) polymer. Moreover, the fabricated hybrid nanocomposite film exhibits a high nonlinear optical response that fulfilling the requirement to induce the FWM effect employed to suppress the mode-competition. Four lasing lines of uniform power-symmetry distribution with a spacing of ~160 GHz have been generated by appropriately adjusting the pump power strength to 230 mW. The results suggest that ZnO-NRs@Au-NSs/MWCNTs nanocomposite film could be a promising filter for stable multi-wavelength generations at room temperature.

A New Strategy of bi-Alkali Metal Doping to Design Boron Phosphide Nanocages of High Nonlinear Optical Response with Better Thermodynamic Stability

Nonlinear optical materials have gained immense scientific interest in the recent times owing to their vast applications in various fields. Continuous strides are made to design and synthesize materials with large nonlinear optical response and high thermodynamic stability. In this regard, we present here bi-alkali metal doping on boron phosphide nanocage as a new strategy to design thermodynamically stable materials with large nonlinear optical response. The geometric, thermodynamic, electronic, optical and nonlinear optical properties of complexes are explored through density functional theory (DFT) simulations. The doping of alkali metal atoms introduces excess of electrons in the host (B12P12) nanocage. These electrons contribute towards the formation of new HOMOs, which reduce the HOMO–LUMO gaps of the designed complexes. The HOMO–LUMO gaps of the designed complexes range from 0.63 eV to 3.69 eV. The diffused excess electrons also induce large hyperpolarizability values in the complexes i.e. up to 4.0 × 104au. TD-DFT calculations have been performed for crucial transition states and UV–VIS analysis. Non-covalent interaction (NCI) along with quantum theory of the atoms in molecules (QTAIM) analyses are carried out to understand the bonding interactions between alkali metal atoms and B12P12 nanocage. All the obtained results suggest that bi-alkali metal doped nanocages are exceptionally stable materials with improved NLO response.

Decorating electron redundant Si n Al12–n N12 (n = 1, 2) nanocages with superalkalis M3O (M = Li, Na, K): excess electron D-A frameworks and nonlinear optical properties

The electron redundant Si n Al12–n N12 (n = 1, 2) nanocages decorated with superalkalis M3O (M = Li, Na, K) are designed and their stabilities, electronic structures and nonlinear optical (NLO) properties are investigated by using density functional theory calculations. The Si-doped Si n Al12–n N12 cages are more stable than the stoichiometric Al12N12, and the calculation reveals that superalkalis M3O can be bound strongly on these electron redundant cages, with binding energies about 5 eV. The superalkalis M3O transfer electrons to Si n Al12–n N12 and the M3O@Si n Al12–n N12 form excess electron donor–acceptor (eeD-A) frameworks. The excess electrons in M3O@Si n Al12–n N12 form loosely bound lone pair electrons, which push up the HOMO energies and lead to narrower energy gaps. The special electronic structures make these complexes have high NLO responses and they are nearly transparent in deep-ultraviolet region. The largest first hyperpolarisability is observed for K3O@Si2Al10N12 and the value reaches 7.12 × 105 au. We hope this study can provide new strategies for exploring unconventional NLO materials.

Computational Study of Structural, Molecular Orbitals, Optical and Thermodynamic Parameters of Thiophene Sulfonamide Derivatives

Thiophene and sulfonamide derivatives serve as biologically active compounds, used for the manufacture of large numbers of new drugs. In this study, 11 selected derivatives of thiophene sulfonamide were computed for their geometric parameters, such as hyperpolarizability, chemical hardness (ƞ), electronic chemical potential (μ), electrophilicity index (ω), ionization potential (I), and electron affinity (A). In addition, FT-IR and UV-Vis spectra were also simulated through theoretical calculations. The geometrical parameters and vibrational frequencies with assignments of the vibrational spectra strongly resemble the experimentally calculated values. Besides, the frontier molecular orbitals were also determined for various intramolecular interactions that are responsible for the stability of the compounds. The isodensity surfaces of the frontier molecular orbitals (FMOs) are the same pattern in most of the compounds, but in some compounds are disturbed due to the presence of highly electronegative hetero-atoms. In this series of compounds, 3 shows the highest HOMO–LUMO energy gap and lowest hyperpolarizability, which leads to the most stable compound and less response to nonlinear optical (NLO), while 7 shows the lowest HOMO–LUMO energy gap and highest hyperpolarizability, which leads to a less stable compound and a high NLO response. All compounds have their extended three-dimensional p-electronic delocalization which plays an important role in studying NLO responses.

Nonlinear optical response of teetotum boron clusters

Using density functional theory calculations, we design the novel materials with high nonlinear optical responses via linking the Li atom and Li3O superalkali to the [Rh2B18], [Ir2B18], [RhPdB18]+, [IrPtB18]+, [Pd2B18] 2+, and [Pt2B18] 2+ teetotum boron clusters. Our results reveal that the first static hyperpolarizability of the Li3O@M2B18, as a microscopic criterion of the nonlinear optical materials, are higher than the Li@M2B18 materials due to the higher electron-donating ability of the Li3O compared to the Li atom. Besides, the hyperpolarizability of the designed materials significantly increases along with the imposed external electric fields, representing that the nonlinear optical responses of the considered materials can be enhanced by applying the electric files parallel to the charge transfer direction.

Silicon Nanosheets versus Graphene Nanosheets: A Comparison of Their Nonlinear Optical Response

Silicene, the silicon analogue of graphene, represents a new class of two-dimensional (2D) materials, which shares some of the outstanding physical properties of graphene. Furthermore, it has the advantage of being compatible with the current Si-based technology. However, this 2D material is not stable and is quite prone to oxidation. The hydride-terminated silicene, called silicane, is a more stable form of 2D silicon, if functionalized via, for example, the hydrosilylation reaction. In this work, the third-order nonlinear optical (NLO) properties of two functionalized silicanes, namely hydride-terminated silicon nanosheets (SiNS-H) and 1-dodecene-functionalized silicon nanosheets (SiNS-dodecene), are accessed and compared to those of single-layer graphene, under 35 ps, 532 and 1064 nm excitation. The present results show that the functionalized silicanes exhibit comparable and even higher NLO response than that of single-layer graphene, making them strong competitors of graphene and very interesting candidates for future photonic and optoelectronic applications.

Removal of toxic heavy metal ions from waste water using superchalcogens: A theoretical study

One of the most exciting events in chemistry is the stable assemblies of atoms, denoted by superatoms, that could mimic the behaviors of elements in the periodic table. For the first time by Jena et al., a novel type of di-anions superchalcogens (BeAl122− and TiAu122-) has been introduced based on the various electron-counting rules. Inspired by the fascinating finding of these superatoms and guided by density functional theory calculations, we propose a novel and efficient strategy to capture pollutants from waste water via adsorbing the toxic heavy metal cations (Cd2+, Hg2+, and Pb2+) by the BeAl122− and TiAu122− superchalcogens. Our results reveal that the BeAl122− and TiAu122− superchalcogens were powerful to adsorb the Pb2+, Hg2+, and Cd2+ cations in the aqueous solution. Furthermore, by investigating the hydrated cations, the adsorption of hydrated [Pb(H2O)4]2+ on the BeAl122− and TiAu122− superatoms was found thermodynamically more favorable than the [Cd(H2O)4]2+ and [Hg(H2O)4]2+. Our calculations also showed that the adsorbing heavy metal cations can considerably narrow the wide HOMO-LUMO gap and remarkably enhance the first hyperpolarizability of the pristine BeAl122− and TiAu122− superchalcogens, due to electron transfer in this type of superatoms. Moreover, the results highlight the systems with higher electron transport rates, show the larger first hyperpolarizability as well as the higher nonlinear optical response. Time-dependent density functional calculations also revealed “ligand to metal charge transfer” vertical excitations for the cation/superchalcogen systems. However, these theoretical findings might be helpful for experimental scientists toward designing high-efficient adsorbents based on superatoms for eliminating water pollutants.

The Importance of Excellent π-π Interactions in Poly(thiophene)s To Reach a High Third-Order Nonlinear Optical Response.

Poly(thiophene)s have an inherently large third-order nonlinear optical (TONO) response, but applications are not straightforward due to unoptimized materials. Therefore, several structure-property relationships (molar mass, branching, regioregularity) are investigated to unravel which structural modifications give the highest TONO response. Poly(3-hexylthiophene) with different molar masses, poly[3-(2-ethylhexyl)thiophene] with different molar masses, and random copolymers with different degrees of regioregularity are synthesized and measured by UV-vis spectroscopy and the third harmonic scattering technique. Every structural modification that leads to an increase in π-π interactions in poly(thiophene)s leads to an increase in the TONO response of the material. Therefore, a material with a high molar mass, an unbranched alkyl side chain, and a high regioregularity degree is preferably tested as a promising TONO material.

The structure-property studies and mechanism of optical limiting action of methyl 4-((4-aminophenyl)ethynyl)benzoate crystal under continuous wave laser excitation

This study focuses on the design of the new dye of donor-π-acceptor (D−π−A) system of methyl 4-((4-aminophenyl)ethynyl)benzoate (MAPEB) to highlight its structural-property relation through a combined experimental and quantum chemical calculation approaches for optical limiting applications. MAPEB was synthesized via aerobic condition palladium-catalysed Sonogashira cross-coupling reaction with good yield. This molecular structure was confirmed by single crystal X-ray crystallographic analysis and the crystal exhibits monoclinic non-centrosymmetric space group of Pc. The existence of intermolecular interactions was confirmed by Hirshfeld analysis, showing high contribution of C⋯H contact which suggested the high nonlinear optical response of the compound. The experimental spectroscopic data including Fourier Transform Infrared (FT-IR), 1H and 13C Nuclear Magnetic Resonance, electronic absorption spectra, HOMO-LUMO energy gap were compared with Density Functional Theory (DFT) at 6–311++G (d,p) basis set. The experimental results complement the theoretical findings in supporting anticipated electronic properties of the molecule. Additionally, the z-scan analysis unveils an excellent value of χ3 of MAPEB in the order of 10−6 esu which indicate good nonlinear optical material under 532 nm continuous wave laser. Low optical limiting action was measured at 110 kW/cm2 which is suitable for various continuous wave laser applications. These findings prove that MAPEB has the potential to be employed as NLO materials for photonic applications.

Insight into the Expanded Mislinked Porphyrins with High Second Order Nonlinear Optical Response.

Materials with outstanding nonlinear optical (NLO) response exhibit excellent prospects in electrooptic devices. Thus, it is essential to find a high-performance NLO material to meet the growing demand for high-speed data transmission. In this study, theoretical investigations on the second order NLO properties of the novel expanded mislinked thia-norhexaphyrin, sulfur-free pentaphyrin, and their substituted derivatives were performed using density functional theory. Theoretical calculations display that the approximate planar structures of sulfur-free pentaphyrin embedded with two five-membered rings exhibits a remarkable NLO response and holds large dipolar contribution (ΦJ=1 = 63.5%) to the first hyperpolarizability among four parent expanded mislinked porphyrins. The static first hyperpolarizability values of these expanded porphyrins were found to range from 3490 to 14 229 au. In addition, the second order NLO response of these porphyrins has greatly improved except for minority electron-releasing- and electron-withdrawing-group substituted cases, and the static first hyperpolarizability value has increased to 47 950 au after installing the donor and acceptor groups. Unambiguous evidence reveals that expanded mislinked porphyrin can serve as a potential candidate for NLO materials.

Passively Q-switched erbium-doped fiber laser utilizing tungsten oxide as a saturable absorber.

We demonstrated a passively $Q$Q-switched fiber laser utilizing tungsten oxide (${\rm WO_{3}}$WO3) thin film as a saturable absorber (SA). The ${\rm WO_{3} {\text -} SA}$WO3-SA was sandwiched as a polymer composite film between fiber ferrules in an erbium-doped fiber cavity. ${\rm WO_{3}}$WO3 exhibits high nonlinear optical response characterized by an appropriate modulation depth of 10% and a saturation intensity of ${100}\;{{\rm MW/cm}^2}$100MW/cm2. The fiber cavity starts to generate a stable pulse train whereby as the pump power increases from 45 to 165 mw, the repetition rate increases from 16.75 to 56.3 kHz, while the pulse width decreases from 13.8 to 4.3 µs. The $Q$Q-switched laser generated maximum pulse energy of 6.6 nJ obtained at 165 mW, which was the maximum pump power available by the used laser diode. This is, to the best of our knowledge, the first demonstration of a $Q$Q-switched fiber laser based on the ${\rm WO_{3} {\text -} SA}$WO3-SA, which could contribute as a new potential SA material in the field of pulsed fiber lasers.