Open Access
Add to BibSonomy
Abstract
The development of solid-state nonlinear optical limiting (NOL) materials is crucial for advancing the practicality in the field of optical limiting. In this paper, we innovatively prepare a new solid NOL material which is spiral carbon nanotubes doped epoxy resin (SCNTs-doped ER, SER) with a simple physical mixing method, and achieve an excellent nonlinear optical limiting performance. We experimentally measured optical limiting of SER with different SCNTs concentrations (0.14, 0.28, and 0.43 mg/mL) and obtained the nonlinear absorption coefficient, nonlinear refractive index, and third-order nonlinear susceptibility at the wavelength 1064 nm. Z-scan experiment results show that the SER exhibits a large nonlinear absorption coefficient (5.07 ± 0.38) × 10−9 m/W. We also measure the transmittance of the SER to evaluate its nonlinear optical limiting performance. For the SER with 0.43 mg/mL concentration, the linear transmittance and minimum transmittance with NOL effects at 1064 nm are 54.8% and 26.2%, respectively. In addition, the SER also has prominent features such as a high damage threshold and easy fabrication, indicating that the SER is a promising solid material for nonlinear optical limiting.
© 2024 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement
1. Introduction
As high-power laser technology advances, it finds extensive application in domains like fundamental scientific investigation, biological therapeutics, and the military sector [1]. Nevertheless, optical detectors and human eye have also been potentially damaged by intense laser irradiation [2–4]. Consequently, the associated optical limiting materials have also started to flourish in order to prevent the possible harm produced by intense lasers. Optical limiting materials, including linear and nonlinear optical limiting (NOL) materials, and phase change materials, have been the subject of research for many years [5,6]. Among them, NOL materials have drawn a lot of attention because of their excellent nonlinear optical effects. Compared to other materials, NOL materials typically exhibit high linear transmittance for low-intensity laser pulses and low nonlinear transmittance under strong light [7,8]. This property of NOL materials that transmittance varies in relation to the incident light intensity is well suited for the protection of human eye and optical detectors in many fields, such as laser medicine, laser processing and laser detection [9].
During the past few decades, significant efforts have been made in the design and preparation of state-of-the-art NOL materials. Overall, current optical limiting materials can be divided into two categories: solution-state and solid-state materials. Solution-state materials, for example, suspensions of graphene and fullerene can be used as optical limiters to attenuate intense laser light [10,11]. However, their poor solubility and physicochemical instability in solvents hinder their practical application. Compared to solution-state materials, solid-state materials were usually provided with good chemical stability and mechanical strength, making them more suitable for optical limiting in variety of environments. Solid-state materials typically include NOL glasses [12], NOL crystals [13], and solid-state composite materials [10,11,14]. NOL glasses are an all-inorganic transparent material with good stability, high optical quality, and excellent optical limiting performance. For NOL crystal, the nonlinear optical limiting performance can be improved by doping. In addition to these materials, solid-state composite materials were typically prepared by combining NOL materials with polymer matrices, such as MoS2/Polymethyl Methacrylate (PMMA), C60/PMMA, boron nitride nanotube/Chitosan (CS), and rGO/Polyvinyl alcohol (PVA) [10,11,14,15]. In these existing reports, NOL materials are generally thin films with a polymer matrix. Nevertheless, the nonlinear limiting effect is commonly related to the effective thickness of the material [16]. The thin thickness limits the length of interaction between the propagating light and the NOL materials. Therefore, it is of great significance to search for solid-state NOL materials of suitable thicknesses.
Epoxy resin (ER) is widely used as matrix material in polymer matrix composites due to its easy-to-adjust thickness, high-temperature resistance, adhesive bonding, high hardness, high transparency, simple curing conditions and low cost of finished product. Spiral carbon nanotube (SCNT) materials in solution exhibit excellent optical limiting performance at a wide range of wavelengths [8,17]. Although carbon nanotubes can be used for optical limiting, most of the current research works on carbon nanotubes are currently realised in suspension for optical limiting [8]. The instability of suspensions is not conducive to practical applications. Instead, employing solid-state composite materials would be more stable for nonlinear optical limiting applications in different environments. There have been some studies using different matrix materials to investigate the nonlinear optical properties of solid-state thin-film materials [8,10,18–20]. Nevertheless, the preparation processes for these materials are complex and environmentally unfriendly. For example, PMMA needs to be dissolved in toxic organic solvents such as toluene [10,20].
In this paper, we innovatively propose and validate a new solid NOL material which is spiral carbon nanotubes doped epoxy resin (SCNTs-doped ER, SER). The experiment results show that the SER exhibit a large nonlinear absorption coefficient, and has higher optical limiting capacity than that of most solid NOL materials at the wavelength of 1064 nm. These experimental results show that the SER is a promising solid NOL material. To the best of our knowledge, this is the first systematic study of the nonlinear optical effects and optical limiting produced by millimetre-thick of SERs at different concentrations using nanosecond laser pulses. Moreover, it also has prominent features such as easy-to-adjust the thickness and concentration of the new solid-state composite material. Compared to other solid-state composite materials, the process of compounding SCNTs into ER is much safer. In addition, SER is prepared by a simple physical mixing method, which provides a new way to achieve excellent NOL performance.
2. Materials preparation
The SCNTs material (diameter of 100${\sim} $200 nm, length of 1${\sim} $5 µm, purity of ${\sim} \; $98%) was synthesised through the chemical vapour deposition (CVD) method (from KH Chemicals Co., Ltd). The TEM image of SCNT is shown in Fig. 1. The epoxy resin (epoxy resin AB glue, ERab) is a two-component high-temperature adhesive (from Shenzhen Tianzhongshan Technology Co., Ltd). The SER is prepared by a simple physical mixing method. First of all, 15 mg of SCNTs is added to epoxy resin B glue (ERb) with 10 mL. Afterwards, the SCNTs-doped ERb is subjected to ultrasound treatment for 30 minutes. The SCNTs-doped ERb has added 25 mL of epoxy resin A glue (ERa) and stirred with a glass rod for 5 minutes. Then, the SER mixture is treated for 30 minutes by ultrasound machine. Finally, the SER with a concentration of 0.43 mg/mL is poured into the mould with 30 mm diameter and is kept in a drying oven (50 °C) for 1 hour. Then, the dried SER is left at room temperature for 20 hours to obtain the solid-state SER. Notable, we can easily modulate the thickness of the solid material by controlling the amount of SER poured into the mould.
As shown in Fig. 2, SERs with different concentrations are fabricated by the same method as described above. Moreover, the optical micrographs indicate that the surface of the SER is flat without agglomeration phenomenon. Therefore, we believe that this simple mixing method for SER is feasible. As a NOL material, good transparency is required, and generally linear transmittance of NOL material needs to be no less than 50%. We first measured the linear transmittance of the SER at 0.14 mg/mL concentration and found that the transmittance was as high as 75%. The linear transmittances were 64% and 55% when the concentration was increased to 2 times and 3 times, respectively, which were also larger than the preset acceptable linear transmittance. Therefore, these three (0.14, 0.28, and 0.43 mg/mL) concentrations were selected for the study. Linear transmittance of the prepared SERs was recorded with a UV-VIS-NIR spectrometer (754PC spectrophotometer) in the wavelength range from 300 to 1100 nm. As shown in Fig. 3 (a), the linear transmittances of three SERs are about 57%, 64%, and 77% at the wavelength of 1064 nm. Besides, a slight shift in cutoff wavelength towards longer wavelengths as the concentration increases can be observed from transmittance spectra, which are attributed to the concentration effect as has been reported in Ref. [21].
Fig. 2. (a) Image of SERs with three SCNTs concentrations (0.14, 0.28, 0.43 mg/mL), (b) (c) and (d) optical micrograph corresponding to (a).
Fig. 3. (a) Linear transmittances of the three SERs, (b)-(d) energy band gaps determined by extrapolating the straight line of Tauc's plot of SERs at three different concentrations corresponding to (a).
Furthermore, the energy bandgap is determined from the optical transmission data of SERs by using Tauc’s plot equation [22,23], which can be written as
where B is a constant, Eg is the energy bandgap of the SERs, hυ is the photon energy, and $\gamma $ is the absorption coefficient calculated by using the relation $\gamma $ = ln(1/T)/L [24,25], where L is the thickness of the SERs, and T is the transmittance. Figures 3(b)–3(d) show the energy bandgap (Eg) values calculated using Eq. (1) of ($\gamma $hυ)2 versus hυ for the SERs. The Eg of the SERs can be obtained by extrapolating the linear part of the plot relating to ($\gamma $hυ)2 and hυ to $\gamma $hυ = 0. The Eg of SERs depends on SERs concentration and decreases from 3.58 to 3.52 eV as SERs concentration increases from 0.14 to 0.43 mg/mL as shown in Fig. 3. As reported in Ref. [26] suggests that the optical bandgap will decrease as the disorder of the amorphous phase increases. In this experiment, the increase in the concentration of SCNTs makes the SERs matrix more amorphous, which enhances the charge conduction and reduces the optical band gap [26].3. Nonlinear optical properties
Z-scan technology can measure the performance of nonlinear absorption and nonlinear refraction of samples by using a Gaussian beam and obtain the magnitude and sign of third-order nonlinear refractive index and nonlinear absorption coefficient [27]. As shown in Fig. 4, a Nd: YAG laser with a wavelength of 1064 nm is used as the light source, 1-10 ns pulse width and 1-10 Hz repetition. The 1 Hz and 10 ns laser pulse with Gaussian beam divergence of M2 = 1.4 (Less than 2% instability) is divided into two beams by a (1:1) beam splitter. The transmitted part from the beam splitter was focused on the SREs by a 100 mm convex lens, which gives a beam waist ${\omega _0}$ of (50 ± 3.8) µm. The samples with a thickness of 3 mm are placed on the stepper motor and moved along the z-axis. The moving step is set to 1 mm, and the moving speed is 1.54 mm/s. As is well known, the Z-scan technology requires the thickness of sample to be less thick than the Rayleigh length so that diffraction effects within the sample can be neglected [14,16]. In this experiment, the calculated result for the Rayleigh distance is 7.4 ± 0.56 mm. Obviously, it is greater than the thickness of SERs (3 mm) and is satisfying the requirements of Z-scan measurements on the sample. The transmitted part from the sample propagated through the aperture S of transmittance 0.38, and then it was detected by an energy Detector 1 (Thorlabs ES120C). The reflected part from the beam splitter was controlled by using a broadband filter, which was detected by another energy Detector 2 (Thorlabs ES120C). The transmittances of the SER can be obtained by comparing the measured energy intensity in Detector 1 and Detector 2. Therefore, the transmitted energy from the aperture, which is the closed-aperture Z-scan, gives information about the sign and the value of the nonlinear refractive index coefficient. Furthermore, the transmitted part from sample propagated through the aperture S of transmittance 1 which is called the open-aperture Z-scan and can be used for measuring the nonlinear absorption coefficient. The determination of the divergence of the laser affects the laser beam waist and laser energy density calibration in the experiment [22]. The uncertainty in this experiment was found to be about 7.6%, which mainly originates from the determination of the divergence of the laser used.
The open-aperture Z-scan curve is used to characterize the nonlinear absorption characteristics of the sample. In the experiments, the normalized transmittance is fitted by [14,16]
where ${q_0}$ is a dimensionless parameter, where β is the nonlinear absorption coefficient, ${I_0}$ is the peak on-axis irradiance of the laser beam at the focus, ${z_0}$ is the Rayleigh length, Leff is the effective thickness of the sample. After fitting calculation, the nonlinear absorption coefficient β of the sample can be obtained. Meanwhile, the imaginary part of the third-order nonlinear susceptibility can be expressed as [5,27] where c is the speed of light, and ${n_0}$ is the linear refractive index of the sample, $\omega $ is the frequency of the incident light.The closed-aperture Z-scan curve reflects the nonlinear refractive characteristics of the sample. In closed-aperture Z-scan experiments, the normalized transmittance is given by [16]
where $\Delta {\phi _0}$ is phase distortion at the waist of the laser beam and can be expressed as [16] where the normalized transmittance value $\Delta T$ was determined as $\Delta T = {T_P} - {T_V}$, ${T_P}$ and ${T_V}$ are the normalized peak and valley transmittance, respectively. S is the transmission of the aperture.Thus, the nonlinear refraction index ${n_2}$ can be obtained as
Meanwhile, the real part of the third-order nonlinear susceptibility can be expressed as [6]
Therefore, utilizing Eqs. (3) and (5) and combining with the obtained ${n_2}$ and β, we can obtain the third-order nonlinear susceptibility ${\chi ^{(3 )}}$ of the material.
In addition, to ensure the safety of the Z-scan experiment, we first obtained laser-induced damage threshold (LIDT) at three different concentrations of SERs by using R-on-1 measurements and their value DE at different concentrations can be calculated by the equation DE = ELIDT/(π$\omega _0^2$), where ELIDT is laser energy when the laser-induced damage [36]. The value DE is in the range of (0.78 ± 0.06)$\,\sim \; $(1.19 ± 0.09) J/cm2. Compared with some other NOL materials, as shown in Table 1, the values of DE of SERs at the wavelength of 1064 nm are better than those of some other commonly used NOL materials, such as graphene oxide Ormosil glasses, MoS2/PAN (polyacrylonitrile) in PMMA, WSe2/PVA film, and rGO/PVA film [10,19,28,29].
Table 1. Comparison of ELIDT of several materials at the wavelength of 1064 nm
We carried out open and closed Z-scan experiments with the same energy densities (0.43 ± 0.03) J/cm2, and the results for open and closed Z-scan experiments are shown in Figs. 5 and 6, respectively. As shown in Fig. 5, the obtained Z-scan curve is a single symmetrical valley curve relative to the focal plane. Therefore, the SER has reverse saturable absorption (RSA) properties. Comparing the three curves in Fig. 5, we can find that the higher the concentration of the SER, the lower the minimum normalized transmittance. The higher concentration of SER results in more pronounced nonlinear effect. The origin of reverse saturable absorption (RSA) could be attributed to the excited state absorption (ESA) or a two-photon absorption (TPA) process [30]. As reported in Ref. [18], the significant thermally induced excited state absorption at nanosecond or longer laser pulses. Consequently, in this experiment, an increase in the concentration of SCNTs enhances thermally induced excited state absorption, thereby increasing the absorption coefficient. The open aperture Z-scan experimental data was fitted by Eq. (2). Then the nonlinear absorption coefficient β was obtained using Eq. (3). The values corresponding to three different concentrations are shown in Table 2, and the value of β is in the range of (0.81 ± 0.06) ${\sim} \,$(5.07 ± 0.38) × 10−9 m/W.
Fig. 6. Normalized transmittance of the three SERs at (0.43 ± 0.03) J/cm2 in closed-aperture Z-scan.
Table 2. Nonlinear absorption coefficient β with different concentration
Figure 6 shows the closed-aperture Z-scan experiment results of the three SERs at (0.43 ± 0.03) J/cm2. These curves show that the nonlinear refractive index of the SERs is negative. High concentration makes the light more divergent. The closed aperture Z-scan experimental data was fitted by Eq. (4). Then the nonlinear refractive index ${n_2}$ was calculated by using Eq. (6) and (7). The values corresponding to three different concentrations are shown in Table 3, and the value of ${n_2}$ is in the range of (−2.8 ± 0.21)$\,\sim \,$(−7.16 ± 0.54) × 10−13 m2/W. As reported in Ref. [31], nonlinear refraction arises from cumulative carrier generation effects induced by photon absorption or thermal effects. In this experiment, an increase in the concentration of SCNTs leads to an enhancement of the thermal effect, which increases the nonlinear refraction. After obtaining the nonlinear absorption coefficient and nonlinear refractive index, we calculated the third-order nonlinear susceptibility $\chi {\,^{(3 )}}$ from Eq. (4) and (8), and the results are shown in Table 3. The value of ${\chi ^{(3 )}}$ is in the range of (0.26 ± 0.02)$\,\sim \,$(1.64 ± 0.12) × 10−7 esu.
Table 3. Nonlinear refractive index ${n_2}$ and third-order nonlinear susceptibility χ(3)with different concentrations
According to the experimental results, as shown in Table 4, we can find that the third-order nonlinear parameters (β, ${n_2}$, and ${\chi ^{(3 )}}$) of the SERs are relatively large at the wavelength of 1064 nm. Significantly, the nonlinear absorption coefficient is several tens of times greater than that of some common nonlinear materials such as Au-embedded ZnO, black phosphorus nanoplatelets, and ZnxSySe100-x-y [32–34]. These results indicate that the SERs may have good optical limiting ability.
Table 4. Value of β, ${n_2}$ and χ(3) of several representative materials
4. Optical limiting performance
The schematic diagram of the optical limiting setup is shown in Fig. 7. The laser pulse is delivered by a Nd: YAG laser with a wavelength of 1064 nm, 1-10 ns pulse width and 1-10 Hz repetition. The 1 Hz and 10 ns laser pulse with Gaussian beam divergence of M2 = 1.4 (Less than 2% instability) is divided into two beams by a (1:1) beam splitter. The transmitted part from the beam splitter was focused on the SREs by a 100 mm convex lens, which gives a beam waist of (50 ± 3.8) µm. SER is placed at the focal point of the lens. The transmitted part from sample propagated through a 200 mm convex lens, which is the same for all measurements, and then it was detected by an energy Detector 1 (Thorlabs ES120C). While the reflected part from the beam splitter was detected by another energy Detector 2 (Thorlabs ES120C). The transmittances of the SER can be obtained by comparing the measured energy intensity in Detector 1 and Detector 2.
To accurately evaluate the NOL ability of the SER, we define the optical limiting capacity coefficient δ as [35]
where T0 is the linear transmittance of the limiter at the initial values, and Tmin is the minimum transmittance of the SER with optical limiting effect. From Eq. (9), we can know that the larger the δ, the stronger the optical limiting effect of the SER.The transmittances of the three SERs with a thickness of 3 mm are depicted in Fig. 8. When the incident laser fluence is low (less than (0.12 ± 0.01) J/cm2), the transmittance of the three SERs is stable at the initial values. With the increasing laser fluence, the SER gradually exhibits nonlinear optical limiting characteristics, and the transmittances decrease gradually until the incident laser fluence reaches the LIDT. For the SER with a concentration of 0.14 mg/mL, the limiting threshold is approximately (0.44 ± 0.03) J/cm2, the damage threshold is about (1.19 ± 0.09) J/cm2, the minimum transmittance is 0.726, and the δ is 0.091. For the SER with a concentration of 0.28 mg/mL, the limiting threshold is approximately (0.43 ± 0.03) J/cm2, the damage threshold is about (0.96 ± 0.07) J/cm2, the minimum transmittance is 0.487, and the δ is 0.15. However, for the SER with a concentration of 0.43 mg/mL, the limiting threshold is approximately (0.41 ± 0.03) J/cm2, the damage threshold is about (0.78 ± 0.06) J/cm2, the minimum transmittance is 0.262, and the δ is 0.28. It is evident that the higher concentration can achieve better nonlinear optical limiting performance.
The NOL effect of the SER may have originated from the reverse saturable absorption (RSA), as has been reported in other multi-walled carbon nanotubes [2,17]. For the RSA process, the intensity of the beam in a material is [37]:
where I is the peak intensity of the incident pulsed laser, $\alpha $ is the linear absorption coefficient and $\beta $ is the RSA coefficient which is related to the imaginary part of ${\chi ^{(3 )}}$. $\beta $ can be obtained from Eq. (3).The solution of Eq. (10) (for $\alpha = 0$) can be expressed as
Therefore, the transmission of the SERs with the length of L can be calculated as follows:
According to Eq. (11) and (12), the theoretical transmittance curves corresponding to the three SERs can be obtained. Substituting β = (0.81 ± 0.06) × 10−9 m/W and L = 3 mm into Eq. (12), we calculated the transmittance curve of the limiter with 0.14 mg/mL. The result is shown in the turquoise colour curve in Fig. 8. Then, using the same method to calculate the transmittance curves of 0.28 and 0.43 mg/mL, we obtained the mustard colour and purple curves shown in Fig. 8. We find that the theoretical curves are in good agreement with the experimental results, which verifies that the optical limiting effect of the SER is mainly due to RSA.
For the SER with RSA characteristics, the NOL ability of the SER depends on the high absorption charge state generated by light. Normally, when the absorption cross-section of the excited state is greater than that of the ground state, reverse saturation absorption occurs. On nanosecond pulses, significant intersystem crossing to other states can occur from the first excited state. In this case, the five-level diagram is applicable. The molecules in the ground state absorb weaker light and are excited to the first singlet state. Then, the transmission is constant as the incident fluence is increased. Then, the molecular absorption energy in the first singlet state accumulates and transitions to a higher singlet state, resulting in optical limiting effects. In addition, undergoes inter-system hopping (ISC) to the first triplet state when the laser pulse width is nanosecond pulses. The molecules in the first triplet state can accumulate and absorb light energy to transition to a higher triplet, accompanied by the generation of optical limiting effects. Thus, the higher the incident energy, the more transition energy accumulation, and the lower the transmittance. Finally, when the energy is very high, the transmittance becomes approximately constant with low value [38].
We have experimentally verified that the SERs exhibit an evident nonlinear limiting effect, and the SER with 0.43 mg/mL can achieve better optical limiting performance with the limiting capacity coefficient δ = 0.286 and minimum transmittance Tmin = 0.262. Compared with some other NOL materials, as shown in Table 5, the values of $\delta $ and Tmin of SER at the wavelength of 1064 nm are better than those of some other commonly used optical limiting materials such as C60-based SiO2 sol-gel, graphene oxide Ormosil glasses, WO3/PVA film, and WSe2/GO/PVA film [19,28,39,40]. In addition, as a solid material, the SER has the advantages of a simple preparation process, stable chemical properties, high hardness and high mechanical strength.
Table 5. Comparison of NOL properties of several solid-state materials at 1064 nm
5. Conclusion
In summary, we have prepared SER using a simple method as a new NOL material, which has excellent nonlinear optical limiting performance and high damage threshold at the wavelength of 1064 nm. We experimentally studied the nonlinear optical properties of SER with different SCNTs concentrations (0.14, 0.28, and 0.43 mg/mL) at the wavelength of 1064 nm. The maximum value of the nonlinear absorption coefficient β, the nonlinear refractive index ${n_2}$, and third-order nonlinear optical susceptibility ${\chi ^{(3 )}}$ are respectively (5.07 ± 0.38) × 10−9 m/W, (−7.16 ± 0.54) × 10−13 m2/W, and (1.64 ± 0.12) × 10−7 esu. The light transmittances of three SERs have been measured experimentally. There are in good agreement with the theoretical curves based on the reverse saturable absorption effect. The SER at 0.43 mg/mL can achieve a very good optical limiting performance with a limiting capacity coefficient of 0.286 and a minimum transmittance of 0.262. The results show SER is a promising solid NOL material and has the potential for practical application in the protection of optical devices.
Funding
National Natural Science Foundation of China (No.62175105); Fundamental Research Funds for the Central Universities (No. 56XBC22047); Natural Science Foundation of Jiangsu Province (No. BK20231451).
Disclosures
The authors declare no conflicts of interest.
Data availability
Data will be made available on request.
References
1. J. G. Zhou and Y. W. Wong, “Organometallic acetylides of PtII, AuI and HgII as new generation optical power limiting materials,” Chem. Soc. Rev. 40(5), 2541–2566 (2011). [CrossRef]
2. Z. Li, C. He, W. Song, et al., “Optical limiting properties of hybrid nickel naphthalocyanine-titania nanoparticals thin films,” Opt. Laser Technol. 112, 413–419 (2019). [CrossRef]
3. Y. Wang, M. Lv, J. Guo, et al., “Carbon-based optical limiting materials,” Sci. China Chem. 58(12), 1782–1791 (2015). [CrossRef]
4. M. Feng, H. Zhan, and Y. Chen, “Nonlinear optical and optical limiting properties of graphene families,” Appl. Phys. Lett. 96(3), 1 (2010). [CrossRef]
5. X. Zhao, X.-Q. Yan, Q. Ma, et al., “Nonlinear optical and optical limiting properties of graphene hybrids covalently functionalized by phthalocyanine,” Chem. Phys. Lett. 577, 62–67 (2013). [CrossRef]
6. M. D. Zidan, A. Arfan, and A. Allahham, “Nonlinear optical investigations of Quinine and Quinotoxine salts by Z-scan technique,” Opt. Laser Technol. 89, 137–142 (2017). [CrossRef]
7. S. A. El-Mongy, M. I. Mohammed, and I. S. Yahia, “Preparation and spectroscopic studies of PbI2-doped poly(methyl methacrylate) nanocomposites films: Dielectric and optical limiting approach,” Opt. Mater. 100, 109626 (2020). [CrossRef]
8. K. C. Chin, A. Gohel, H. I. Elim, et al., “Modified carbon nanotubes as broadband optical limiting nanomaterials,” J. Mater. Res. 21(11), 2758–2766 (2006). [CrossRef]
9. P. Jiang, B. Zhang, Z. Liu, et al., “MoS2 quantum dots chemically modified with porphyrin for solid-state broadband optical limiters,” Nanoscale 11(43), 20449–20455 (2019). [CrossRef]
10. Q. Liao, Q. Zhang, X. Wang, et al., “Facile fabrication of POSS-Modified MoS2/PMMA nanocomposites with enhanced thermal, mechanical and optical limiting properties,” Compos. Sci. Technol. 165, 388–396 (2018). [CrossRef]
11. P. Innocenzi and G. Brusatin, “Fullerene-based organic-inorganic nanocomposites and their applications,” Chem. Mater. 13(10), 3126–3139 (2001). [CrossRef]
12. X. Feng, Z. Shi, C. Chen, et al., “All-Inorganic Transparent Composite Materials for Optical Limiting,” Adv. Opt. Mater. 8(10), 1–10 (2020). [CrossRef]
13. Y. He, C. He, B. Dong, et al., “Investigation on nonlinear absorption and optical limiting properties of Tm:YLF crystals,” Opt. Mater. 147, 114786 (2024). [CrossRef]
14. M. R. R. Vaziri, “Z-scan theory for nonlocal nonlinear media with simultaneous nonlinear refraction and nonlinear absorption,” Appl. Opt. 52(20), 4843–4848 (2013). [CrossRef]
15. Y. Chen, M. Hanack, Y. Araki, et al., “Axially modified gallium phthalocyanines and naphthalocyanines for optical limiting,” Chem. Soc. Rev. 34(6), 517–529 (2005). [CrossRef]
16. Y. Xu, Y. Lu, Y. Zuo, et al., “Z-scan measurements of nonlinear refraction and absorption for aluminum-doped zinc oxide thin film,” Appl. Opt. 58(22), 6112 (2019). [CrossRef]
17. K. Chen, W. Su, Y. Wang, et al., “Nanocomposites of carbon nanotubes and photon upconversion nanoparticles for enhanced optical limiting performance,” J. Mater. Chem. C 6(27), 7311–7316 (2018). [CrossRef]
18. P. Mondal, P. Choubey, Y. Gupta, et al., “Experimental observation of enhanced reverse saturable absorption in Bi2Se3 nanoplates doped PMMA thin film,” Mater. Res. Express 9(11), 115001 (2022). [CrossRef]
19. Y. Zu, C. He, D. Liu, et al., “Nonlinear optical properties of poly (vinyl alcohol) thin films doped with in-situ WSe2/rGO composite,” Opt. Laser Technol. 142, 107198 (2021). [CrossRef]
20. X.-L. Zhang, Z.-B. Liu, X. Zhao, et al., “Optical limiting effect and ultrafast saturable absorption in a solid PMMA composite containing porphyrin-covalently functionalized multi-walled carbon nanotubes,” Opt. Express 21(21), 25277 (2013). [CrossRef]
21. BÖ Uysal, ÜÖA Arier, and Ö Pekcan, “Tailoring the electrical and optical properties of carbon nantube reinforced transparent TiO2 composites by varying nanotube concentrations,” Surf. Rev. Lett. 27(02), 1–7 (2020). [CrossRef]
22. M. Ali, A. Shehata, M. Ashour, et al., “Measuring the nonlinear optical properties of indium tin oxide thin film using femtosecond laser pulses,” J. Opt. Soc. Am. B 37(11), A139 (2020). [CrossRef]
23. F. A. Samad, M. Sh. Abdel-wahab, W. Z. Tawfik, et al., “Thickness-dependent nonlinear optical properties of ITO thin films,” Opt. Quantum Electron. 55(8), 1–21 (2023). [CrossRef]
24. F. A. Samad, A. Mahmoud, M. Sh. Abdel-Wahab, et al., “Investigating the influence of ITO thin film thickness on the optical Kerr nonlinearity using ultrashort laser pulses,” J. Opt. Soc. Am. B 39(5), 1388 (2022). [CrossRef]
25. F. A. Samad and T. Mohamed, “Intensity and wavelength-dependent two-photon absorption and its saturation in ITO film,” Appl. Phys. A 129(1), 1–11 (2023). [CrossRef]
26. M. I. Mohammed, H. Y. Zahran, S. Zyoud, et al., “Simple processed polyvinyl alcohol/multi-wall carbon nanotube polymeric nanocomposites for high-performance optoelectronics,” J Mater Sci: Mater Electron 35(7), 1–14 (2024). [CrossRef]
27. Y. Cheng, H. Hao, H. Xiao, et al., “Third-order nonlinear optical properties of two novel fullerene derivatives,” J Mater Sci: Mater Electron 42(23), 235401 (2009). [CrossRef]
28. X. Sun, X. Hu, J. Sun, et al., “Broadband optical limiting and nonlinear optical graphene oxide co-polymerization Ormosil glasses,” Adv. Compos. Hybrid Mater. 1(2), 397–403 (2018). [CrossRef]
29. M. Shi, N. Dong, N. He, et al., “MoS2 nanosheets covalently functionalized with polyacrylonitrile: Synthesis and broadband laser protection performance,” J. Mater. Chem. C 5(45), 11920–11926 (2017). [CrossRef]
30. R. Wei, X. Tian, H. Zhang, et al., “Facile synthesis of two-dimensional WS2 with reverse saturable absorption and nonlinear refraction properties in the PMMA matrix,” J. Alloys Compd. 684, 224–229 (2016). [CrossRef]
31. D. Karthikeyan, K. Vijayakumar, P. Suhasini, et al., “Third-order nonlinear optical responses of Cr3 + ions on La2(WO4)3 nanoparticles for optical limiting applications,” J. Photochem. Photobiol., A 436, 114377 (2023). [CrossRef]
32. S. A. Ali, P. B. Bisht, B. S. Kalanoor, et al., “Enhanced short wave IR third order nonlinearity of gold nanoparticle embedded ZnO thin films,” J. Opt. Soc. Am. B 30(8), 2226 (2013). [CrossRef]
33. K. Wang, Y. Feng, C. Chang, et al., “Broadband ultrafast nonlinear absorption and nonlinear refraction of layered molybdenum dichalcogenide semiconductors,” Nanoscale 6(18), 10530–10535 (2014). [CrossRef]
34. S. Rani, D. Mohan, N. Kishore, et al., “Investigation of nonlinear optical parameters of zinc based amorphous chalcogenide films,” Optik 125(12), 2840–2843 (2014). [CrossRef]
35. Z. Wu, Y. Lu, Y. Zuo, et al., “Optical limiting effect of C 70 solution at 1064 nm,” Appl. Opt. 59(14), 4371 (2020). [CrossRef]
36. P. Wu, Y. Lian, L. Zhang, et al., “Ultraviolet laser-induced damage characteristics of 70% deuterated potassium dihydrogen phosphate crystals,” Opt. Mater. Express 12(7), 2759 (2022). [CrossRef]
37. L. W. Tutt and T. F. Boggess, “A review of optical limiting mechanisms and devices using organics, fullerenes, semiconductors and other materials,” Prog. Quantum Electron. 17(4), 299–338 (1993). [CrossRef]
38. S. Hirata, K. Totani, T. Yamashita, et al., “Large reverse saturable absorption under weak continuous incoherent light,” Nat. Mater. 13(10), 938–946 (2014). [CrossRef]
39. O. G. Morales-Saavedra, R. Castañeda, J. G. Bañuelos, et al., “Preparation of fullerene (C 60) based SiO 2 sonogel hybrid composites: UV laser induced photo-polymerization, morphological, and optical properties,” J. Nanosci. Nanotechnol. 8(7), 3582–3594 (2008). [CrossRef]
40. Y. Li, Z. Zhang, and J. Zhu, “Broadband optical limiting properties of Tungsten Trioxide-Poly (Vinyl Alcohol) solid-state nanocomposite films,” Opt. Mater. 119, 1–5 (2021). [CrossRef]
