Nonlinear Optical Devices Research Articles

Tailoring the Thickness-Dependent Optical Properties of Conducting Nitrides and Oxides for Epsilon-Near-Zero-Enhanced Photonic Applications.

The unique properties of the emerging photonic materials, conducting nitrides and oxides, especially their tailorability, large damage thresholds, and, importantly, the so-called epsilon-near-zero (ENZ) behavior, have enabled novel photonic phenomena spanning optical circuitry, tunable metasurfaces, and nonlinear optical devices. This work explores direct control of the optical properties of polycrystalline titanium nitride (TiN) and aluminum-doped zinc oxide (AZO) by tailoring the film thickness, and their potential for ENZ-enhanced photonic applications. This study demonstrates that TiN-AZO bilayers support Ferrell-Berreman modes using the thickness-dependent ENZ resonances in the AZO films operating in the telecom wavelengths spanning from 1470 to 1750nm. The bilayer stacks also act as strong light absorbers in the ultraviolet regime using the radiative ENZ modes and the Fabry-Perot modes in the constituent TiN films. The studied Berreman resonators exhibit optically induced reflectance modulation of 15% with picosecond response time. Together with the optical response tailorability of conducting oxides and nitrides, using the field enhancement near the tunable ENZ regime can enable a wide range of nonlinear optical phenomena, including all-optical switching, time refraction, and high-harmonic generation.

Towards compact phase-matched and waveguided nonlinear optics in atomically layered semiconductors

Nonlinear frequency conversion provides essential tools for light generation, photon entanglement, and manipulation. Transition metal dichalcogenides (TMDs) possess huge nonlinear susceptibilities and 3R-stacked TMD crystals further combine broken inversion symmetry and aligned layering, representing ideal candidates to boost the nonlinear optical gain with minimal footprint. Here, we report on the efficient frequency conversion of 3R-MoS2, revealing the evolution of its exceptional second-order nonlinear processes along the ordinary (in-plane) and extraordinary (out-of-plane) directions. By measuring second harmonic generation (SHG) of 3R-MoS2 with various thickness - from monolayer (~0.65 nm) to bulk (~1 {\mu}m) - we present the first measurement of the in-plane SHG coherence length (~530 nm) at 1520 nm and achieve record nonlinear optical enhancement from a van der Waals material, >10^4 stronger than a monolayer. It is found that 3R-MoS2 slabs exhibit similar conversion efficiencies of lithium niobate, but within propagation lengths >100-fold shorter at telecom wavelengths. Furthermore, along the extraordinary axis, we achieve broadly tunable SHG from 3R-MoS2 in a waveguide geometry, revealing the coherence length in such structure for the first time. We characterize the full refractive index spectrum and quantify both birefringence components in anisotropic 3R-MoS2 crystals with near-field nano-imaging. Empowered with these data we assess the intrinsic limits of the conversion efficiency and nonlinear optical processes in 3R-MoS2 attainable in waveguide geometries. Our analysis highlights the potential of 3R-stacked TMDs for integrated photonics, providing critical parameters for designing highly efficient on-chip nonlinear optical devices including periodically poled structures, resonators, compact optical parametric oscillators and amplifiers, and optical quantum circuits.

Broadband BiOCl Nonlinear Saturable Absorber for Watt‐Level Passively Q‐Switched Yb:LuAG Single Crystal Fiber Laser

AbstractThe development of nonlinear optical (NLO) devices is limited to the mid‐infrared range due to the lack of broadband NLO response. As an indirect band gap semiconductor, BiOCl has a band gap of ≈3.3 eV. The special anisotropic lamellar structure makes it exhibit excellent electrical and optical properties; however, its NLO saturable absorption effect is rarely reported. In this study, the NLO response, optical properties, and applications of BiOCl crystals grown by chemical vapor phase transport method are studied in detail. The transmission spectrum indicates the BiOCl crystal has a broadband transparent region (0.4–11 µm). The saturable absorption of BiOCl is characterized by the Z‐scan method with 532 and 1030 nm pulsed lasers. With BiOCl as the saturable absorber (SA), watt‐level passively Q‐switched pulsed laser based on Yb:LuAG single crystal fiber (SCF) is realized. This is the first report of BiOCl as SA for passively Q‐switched all‐solid‐state pulsed laser, and the obtained average power is the highest value of passively Q‐switched SCF pulsed lasers reported so far. The high transmittance, high laser damage threshold, wideband NLO response, and environmental stability of BiOCl indicate that BiOCl crystal is a potential candidate for NLO applications.

Chiral Lead-Free Double Perovskite Single-Crystalline Microwire Arrays for Anisotropic Second-Harmonic Generation.

Halide double perovskites present a new branch for versatile optoelectronic devices because of their huge structural compatibility and environmental friendliness, whereas nonlinear optics (NLO) devices remain blank for this fascinating family. Simultaneously, the precise patterning of single-crystalline perovskite microwire arrays remains a challenge for the integration of NLO devices. Herein, we designed lead-free chiral 2D double perovskites with the nonsymmetrical structure presenting second-harmonic generation (SHG). Furthermore, perovskite single-crystalline arrays with regulated geometry, pure orientation, and high crystallinity are prepared using the capillary-bridge confined assembly technique. The efficient SHG originates from the asymmetric crystal structure and high crystallinity of the microwire arrays. Compared with their polycrystalline thin-film counterparts, linearly polarized SHG and a higher SHG conversion efficiency are demonstrated based on microwire arrays. The results not only expand the applications of lead-free double perovskites in the NLO-integrated fields but also provide a viable way for lead-free optoelectronic devices.

Giant Enhancement and Directional Second Harmonic Emission from Monolayer WS2 on Silicon Substrate via Fabry-Pérot Micro-Cavity.

Two-dimensional transition metal dichalcogenides (TMDs) possess large second-order optical nonlinearity, making them ideal candidates for miniaturized on-chip frequency conversion devices, all-optical interconnection, and optoelectronic integration components. However, limited by subnanometer thickness, the monolayer TMD exhibits low second harmonic generation (SHG) conversion efficiency (<0.1%) and poor directionality, which hinders their practical applications. Herein, we proposed a Fabry-Pérot (F-P) cavity formed by coupling an atomically thin WS2 film with a silicon hole matrix to enhance the SH emission. A maximum enhancement (∼1580 times) is achieved by tuning the excitation wavelength to be resonant with the microcavity modes. The giant enhancement is attributed to the strong electric field enhancement in the F-P cavity and the oscillator strength enhancement of excitons from suspended WS2. Moreover, directional SH emission (divergence angle ∼5°) is obtained benefiting from the resonance of the F-P microcavity. Our research results can provide a practical sketch to develop both high-efficiency and directional nonlinear optical devices for silicon-based on-chip integration optics.

Large third-order optical nonlinearities of two-dimensional CsPbBr3 nanoplatelets

Metal halide perovskites show considerable optical nonlinearity and could be used for cost-effective nonlinear optical devices if their nonlinear susceptibilities can be improved. Here, we report large optical nonlinearity, including third-order nonlinear absorption, refraction, and two-photon absorption excited luminescence, of CsPbBr3 nanoplatelets with a thickness of two or three atomic layers and a plane size of about 60 nm. Specifically, the nonlinear absorption was mainly induced by two-photon absorption at low incident powers, and the nonlinear absorption cross section reached 2.15 × 107 GM. It is two orders of magnitude larger than that of CsPbBr3 nanocrystals, which makes them an ideal optical limiting material. Furthermore, the nanoplatelets exhibited large self-phase modulation-induced nonlinear refraction, and the figures of merit W and T satisfied W &amp;gt;1 and T &amp;lt;1, which allow for optical switching. The large optical nonlinearity of CsPbBr3 nanoplatelets provides a basis for multifunctional applications in nonlinear optical devices.

Defect-doped one-dimensional nonlinear photonic crystals exhibit coherent perfect absorption with bistable properties

In this paper, the bistable phenomenon with the coherent perfect absorption properties are studied through the nonlinear transfer matrix method in one-dimensional nonlinear photonic crystals doped with a defect. The focus is on the influences of the relative phase of coherent light on the bistable coherent absorption intensity, and the tuning of the bistable threshold by parameters such as angle and wavelength of incidence. The simulated results show that the coherent absorption intensity is very sensitive to the relative phase of coherent incidence. As the phase decreases, the absorption intensity also decreases, varying from 1 to −1 when the phase change is within 180°. The tuning of the relative phase to the absorption intensity provides great convenience for the application of bistable, and parameters such as the incident angle can also achieve sensitive tuning of the bistable threshold. The larger the incident angle, the larger the threshold, and the more obvious the bistable phenomenon at TE mode. The application of nonlinear optical devices has been expanded in the fields of filters, optical switches, optical power threshold devices, etc.

Tunable optical nonlinearity of indium tin oxide for optical switching in epsilon-near-zero region.

The propagation of light in the epsilon-near-zero (ENZ) region of materials exhibits intriguing linear and nonlinear optical phenomenon that have been extensively exploited for a plethora of applications. Here, we show that the optical properties as well as the ENZ wavelength of magnetron-sputtered indium tin oxide (ITO) thin films could be judiciously engineered. The measurement of nonlinear optical properties reveals that the control of deposition conditions allows for the tuning of absorptive optical nonlinearity between saturable absorption and reverse saturable absorption. The ENZ wavelength for the ITO film is deduced as around 1553nm. We obtain the highest third-order nonlinear absorption coefficient and imaginary part of third-order nonlinear susceptibility for the ITO thin film through Z-scan method as -50.56 cm/GW and ∼38 × 10-14 e.s.u. at 1050nm, and -64.50 cm/GW and ∼45 × 10-14 e.s.u. at 1550nm, respectively. We demonstrate further that the strong saturable absorption of the ITO thin film enables Q-switched pulse laser generation in ∼1050 and ∼1550nm regions with tunable repetition rates and pulse energies. The present results suggest the great application potential of the ITO thin film in the field of nonlinear optical devices.

Computational modeling for the design of new fluorescent organic compounds based on both diketopyrrolopyrrole and nitrobenzofurazan moieties

• Design of new fluorescent organic compounds based on both diketopyrrolopyrrole and nitrobenzofurazan moieties. • Planar geometry stabilized by intra-molecular non-covalent interactions (NCIs). • Excellent optoelectronic properties of the studied compounds. • Push-pull effects on the geometrical, optical and charge transfer properties of the designed molecules have been examined. • Potential applications of the designed materials for their use in OSCs and NLO devices. Three examples of organic π-conjugated systems, based on both diketopyrrolopyrrole (DPP) and nitrobenzofurazan (NBD) were theoretically designed as host fluorescent materials that all of them emitted intense infrared fluorescence and the maximum emission bands ranged from 841 nm to 868 nm. Theoretical analysis by utilizing density function theory (DFT) and its extension of TD-DFT methods with B3LYP functional at the 6–311 g(d,p) calculation level, in acetonitrile, have been reported on the geometry, optoelectronic, absorption/emission characteristics of the studied materials. The furan-, thiophene-, or selenophene-flanked-DPP and coupled to NBD, named after M1 (X = O), M2 (X = S) and M3 (X = Se), have a great impact on optoelectronic properties to design lower optical band gap materials with excellent nonlinear optical (NLO) properties and efficient intra-molecular charge transfer (ICT). The studied molecular structures adopt a planar geometry stabilized by intra-molecular non-covalent interactions (NCIs). The reduced density gradient (RDG) has been further developed to analyze and understand the typical NCIs and their characteristics. The analysis of electron density and its reduced density gradient (RDG), NCIs, the topological analyses from MEP, ELF and LOL, QTAIM were carried out to evaluate the charge transfer within the investigated compounds.

RETRACTED ARTICLE: Optical and structural properties of Sn and Ag-doped PbS/PVA nanocomposites synthesized by chemical bath deposition

In this work, Sn and Ag doped PbS/PVA nanocomposites, in three different concentrations were successfully prepared using the low-cost and simple method of chemical bath deposition (CBD). X-ray diffraction patterns confirmed the formation of the PbS cubic phase in all of the nanocomposites. FE-SEM images showed that PbS NPs are cubic in shape and the doping can alter the shape of grains. DLS analysis applied for solution NPs exhibited a 175 nm size distribution for PbS NPs and decreased by doping Ag and Sn to almost 100 nm and 110 nm, respectively. Optical absorption spectra showed the blue phenomena and the band gaps of Sn: PbS/PVA and Ag: PbS/PVA nanocomposites increased with adding Sn and Ag from 3.08 eV for pure PVA/PbS to 3.33 eV for Sn doped and 3.43 eV for Ag-doped samples. The nonlinear refractive index is decreased from 0.55 m2 W−1 for pure PVA/PbS to 0.11 m2 W−1 and 0.13 m2 W−1 for Sn and Ag-doped samples, respectively. Hence, doping Ag and Sn enhanced the optical sensitivity issue of nanocomposites and raised the optical resistivity. Collectively, our results can be useful in the design of linear and nonlinear optical devices such as sensors and optical switches and limiters.

Additive‐Triggered Polar Polymorph Formation: β‐Sc(IO 3 ) 3 , a Promising Next‐Generation Mid‐Infrared Nonlinear Optical Material

Noncentrosymmetric (NCS) solids have attracted interest for their potential in ferroelectric, piezoelectric, and nonlinear optical (NLO) devices, but their synthesis remains a major challenge. In this study, the additive Li2CO3 triggers formation of an NCS precursor at an early nucleation stage, and plays a crucial role in the successful polymorphism transformation. The resultant metastable β-Sc(IO3)3 is a promising mid-infrared NLO crystal, with the strongest second-harmonic generation responses (2.2 × KTiOPO4 @ 2100 nm, 16 × KH2PO4 @ 1064 nm) and the largest optical bandgap (4.52 eV) for a rare-earth iodate, as well as sufficient birefringence (Δn = 0.219 @ 546 nm) for type I phase-matching, and wide optical transparency, which are induced by optimal alignment of the iodate anions. This study reveals the key role of additives in the growth of polar NCS solids, a discovery with implications for the strategic design of new NCS polymorphism materials with exceptional NLO properties.

Additive-Triggered Polar Polymorph Formation: β-Sc(IO3 )3 , a Promising Next-Generation Mid-Infrared Nonlinear Optical Material.

Noncentrosymmetric (NCS) solids have attracted interest for their potential in ferroelectric, piezoelectric, and nonlinear optical (NLO) devices, but their synthesis remains a major challenge. In this study, the additive Li2 CO3 triggers formation of an NCS precursor at an early nucleation stage, and plays a crucial role in the successful polymorphism transformation. The resultant metastable β-Sc(IO3 )3 is a promising mid-infrared NLO crystal, with the strongest second-harmonic generation responses (2.2×KTiOPO4 @ 2100 nm, 16×KH2 PO4 @ 1064 nm) and the largest optical band gap (4.52 eV) for a rare-earth iodate, as well as sufficient birefringence (Δn=0.219 @ 546 nm) for type I phase-matching, and wide optical transparency, which are induced by optimal alignment of the iodate anions. This study reveals the key role of additives in the growth of polar NCS solids, a discovery with implications for the strategic design of new NCS polymorphism materials with exceptional NLO properties.

Spectroscopic investigation and density functional theory prediction of first and second order hyperpolarizabilities of 1-(4-bromophenyl)-3-(2,4-dichlorophenyl)‑prop-2-en-1-one

This work presents the spectroscopic analysis and nonlinear optical (NLO) behaviour of 1-(4-Bromophenyl)-3-(2,4-dichlorophenyl)‑prop-2-en-1-one (DCBC). The motivation behind choosing chalcone derivative DCBC for NLO studies is its crystallization in non-centrosymmetric structure, excellent second harmonic generation efficiency (SHG) and flexibility in structure of chalcones due to donor-acceptor groups. The compound was characterized by FT-IR, FT-Raman, UV–vis and NMR techniques. The structural and spectroscopic features of the molecule were calculated using density functional theory (DFT) employing B3LYP/6–311++G(d,p) basis set and compared with the experimental values. The complete vibrational assignments were made on the basis of potential energy distribution (PED). The Natural Bond Orbital (NBO) analysis of DCBC has been done in order to provide the detailed insight into the nature of electronic conjugation between the bonds in this molecule. The second-order perturbation theory analysis of Fock matrix in the NBO basis of the molecule shows the strong intramolecular hyperconjugative interactions between σ (Cl3-C28) to σ*(C26-C28), n(1)(Cl3) to σ*(C26-C28) and π(C6-C8) to π*(C5-C13) resulting in large stabilization energies leading to large delocalization. A time-dependant variant of DFT (TD-DFT) is applied to calculate the electronic properties such as oscillator strengths, absorption maxima and HOMO and LUMO energies. The HOMO-LUMO energy gap is found to be 3.882 eV and is used to calculate global reactivity parameters. Isotropic chemical shifts were calculated using gauge invariant atomic orbital (GIAO) method and these matched well with the experimental results, indicating the accuracy of calculation method. Molecular Electrostatic Potential (MEP) surface has been depicted to know the chemically active regions of the molecule. The nonlinear optical properties of title molecule were addressed theoretically by the determination of two contributions, vibrational and electronic, to polarizability (α) and the first and the second order hyperpolarizabilities (β and γ). The electronic first and second order hyperpolarizabilities of DCBC determined by Finite Field approach method are found to be 17.805 × 10−30 and 6.0 × 10−41 e.s.u. respectively. These values are comparable to other chalcones and organic NLO materials which indicate that the studied molecule is responsive to nonlinear optical (NLO) effect and has enhanced applicability in the development of nonlinear optical devices.

CVD growth and optical characterization of homo and heterobilayer TMDs

The stacking of few layers of transition metal dichalcogenides (TMDs) and their heterostructures allows us to create new structures, observe new physical phenomena, and envision new applications. Moreover, the twist angle in few-layer TMDs can significantly impact their electrical and optical properties. Therefore, controlling the TMD material and obtaining different stacking orientations when synthesizing TMDs via chemical vapor deposition (CVD) is a powerful tool, which can add functionality to TMD-based optoelectronic devices. Here, we report on the synthesis of few-layer MoS2 and WS2 crystals, as well as their heterobilayer structures with 0° and 60° twist angles between layers via CVD. Raman and photoluminescence spectroscopies demonstrate the quality, crystallinity, and layer count of our grown samples, while second harmonic generation shows that adjacent layers grow with 0° or 60° twist angles, corresponding to two different crystal phases. Our study based on TMDs with different and multiple stacking configurations provides an alternative route for the development of future optoelectronic and nonlinear optical devices.

Enhanced near-infrared femtosecond nonlinear optical properties in zinc borate glasses activated with Er2O3

Several advanced materials have been investigated for nonlinear optical device applications. However, oxide glasses are competing materials in contrast to those advanced materials due to ease of preparation in three dimensions with diverse shapes along with flexibility in choosing the composition which is essential to tune the nonlinear optical features for specific applications. Doping rare-earth ions is one of the methods used to tune the nonlinear optical features of glass specimens, and it has been explored extensively in recent years. Using femtosecond laser pulses, the effect of Er2O3 concentration on nonlinear optical characteristics such as nonlinear absorption, nonlinear refraction, and optical limiting qualities was investigated using the Z-scan approach. The dual photon absorption and self‒focusing refraction nonlinear magnitudes are improved as the function of Er2O3 content owing to the formation of non‒bridging oxygens and enhancement in polarizability of glasses while the optical limiting features were decreased. These nonlinear absorptions and optical limiting results endorse the high Er2O3 loaded glasses are beneficial for nonlinear photonic devices functioning in the near-infrared regions.

Efficient Excitation and Tuning of Multi-Fano Resonances with High Q-Factor in All-Dielectric Metasurfaces.

Exciting Fano resonance can improve the quality factor (Q-factor) and enhance the light energy utilization rate of optical devices. However, due to the large inherent loss of metals and the limitation of phase matching, traditional optical devices based on surface plasmon resonance cannot obtain a larger Q-factor. In this study, a silicon square-hole nano disk (SHND) array device is proposed and studied numerically. The results show that, by breaking the symmetry of the SHND structure and transforming an ideal bound state in the continuum (BIC) with an infinite Q-factor into a quasi-BIC with a finite Q-factor, three Fano resonances can be realized. The calculation results also show that the three Fano resonances with narrow linewidth can produce significant local electric and magnetic field enhancements: the highest Q-factor value reaches 35,837, and the modulation depth of those Fano resonances can reach almost 100%. Considering these properties, the SHND structure realizes multi-Fano resonances with a high Q-factor, narrow line width, large modulation depth and high near-field enhancement, which could provide a new method for applications such as multi-wavelength communications, lasing, and nonlinear optical devices.

Electronic, Thermodynamic Properties, Nonlinear Optical Responses, and Molecular Docking Studies on Cephalexin

The topology analysis of electron localization function (ELF), localized orbital locator (LOL), the study of nonlinear optical properties, thermal properties, and biological activities of cephalexin have been performed using DFT/B3LYP and employing 6-311++G(d,p) basis sets. The Mulliken atomic charge on atoms has been calculated. The quantities describing nonlinear optical (NLO) properties like molecular polarizability (α), first hyperpolarizability (β), and second hyperpolarizability (γ) were comparable to the values of urea. The computed value of the second hyperpolarizability was found to be negative, which is an important feature for the system of controllable NLO devices. The thermodynamic properties like heat capacity (S), enthalpy (H), and entropy (S) are positively correlated with the temperature. Further, the title molecule shows good potentiality for binding with the selected target protein matrix metalloproteinase-2.

Enhanced non-linear optical response of alkali metal-doped nitrogenated holey graphene (C2N)

In the quest of better non-linear optical (NLO) materials, a DFT method is employed on alkali metals doped C2N to investigate the optoelectronic characteristics. To understand the optoelectronic properties the charge distribution is a key factor for which frontier molecular orbitals (FMOs), transition density matrix (TDM), density of states (DOS), electron density difference map (EDDM) and molecular electrostatic potential(MEP) analyses were carried out. Interaction energy (Eint) is computed to delve into thermodynamic stability. The projected results of all the complexes is lying in domain of effective NLO materials, like constricted EH-L, reduced Eopt, bathochromic shift in ʎmax and above all upgraded α0 and β0. When compared to C2N, doped complexes display extraordinary NLO response with 1st hyperpolarizability ranging from 2.4 × 104 (K@C2N) to 8.02 × 104 a.u. (Li@C2N). Furthermore, alkali metal doping also lessens the energy gap (EH-L)from 2.3 eV to 2.06 eV in Li@C2N. The nature of vibrations and interactions are probed via IR and NCI analysis. Doped molecules (Li@C2N-K@C2N) do possess greater dipole moment (2.48 D to 5.56 D) than C2N (2.04 D). All characteristics support the use of all doped complexes in integrated NLO devices, paving the way for new approach to computational designing of super-efficient NLO materials.

Investigation of structural, optoelectronic and thermoelectric properties of GaCuX2 (X = S, Se and Te) chalcopyrites semiconductors using the accurate mBJ approach

Ternary chalcopyrites have recently been the focus of scientists due to their optoelectronic and thermoelectric application as solar energy converters, nonlinear optical devices and detectors. In the present study, we used the first principle calculations based on the density functional theory (DFT) to explore the structural, optoelectronic and thermoelectric properties of GaCuX2 (X = S, Se and Te). The electronic band structure, density of states and optical properties were investigated using the modified Becke Johnson (TB-mBJ) approximation. These materials were discovered to be direct band gap semiconductors in this study, which agrees well with previously reported results. When compared to GaCuS2 and GaCuTe2, GaCuSe2 has a smaller gap value, due to the lower chemical bonding nature of Ga and Se atoms. The density of states of these three ternary chalcopyrites, as well as their optical properties including dielectric functions, optical conductivity and absorption coefficient have also been examined and discussed in details. The maximum reflectivity occurs at 13.5 eV, which exists in the ultra-violet region, showing that investigated materials can be employed to shield high frequency ultraviolet radiations. The calculated maximum refractive index static value varies from 1.5 to 5.5 eV, predicting that the materials under consideration can be used in a vast range of optoelectronic applications, especially in the visible range. GaCuS2 shows high refraction among these compounds. Finally, the thermoelectric properties of these materials, such as the Seebeck coefficient, the power factor and figure of merit, are analyzed using the semi-classical Boltzmann theory as executed in the BoltzTraP code. The high Seebeck coefficient and figure of merit values reveal that these systems belong to a new class of high-efficiency thermoelectric materials (TE) for high-temperature application fields. These findings are likely to open up new route for researchers looking into the potential areas of application of these compounds in thermoelectric and optoelectronic devices.

Third-order nonlinear responses of symmetrical meso-substitutes porphyrin derivatives

A series of porphyrin derivatives with an electron-accepting group (EAG), electron-donating group (EDG) attached in phenyl at a meso-position have been prepared and studied using the Z-scan technique. Due to EAG and EDG effects, the nonlinear refractive index, n2 and nonlinear absorption coefficient, β were measured with the order of 10−5(cm2/W)and 100(cm/W), respectively. Herein, Hydroxy and methoxy groups as electron donor indicate better result in comparison with electron accepting groups like methoxycarbonyl substituted in phenyl group or pyridine attached at a meso-position of porphyrin. Although the cobalt as substituted in porphyrin can increase nonlinearity responses, EDG has more effective in enhancement of nonlinearity than metal substituted. Nonlinear optical properties of the products were discussed to the effect of cobalt ion substitution at the core of porphyrin structure. The main results indicated some symmetric porphyrins can have higher nonlinearity responses than some asymmetric porphyrins. Considering results, symmetric porphyrins can more improve nonlinearity responses than metal substituted in porphyrins. The good results of these type of porphyrins causes to be a good candidate in nonlinear optical devices.