Database on the nonlinear optical properties of graphene based materials

The knowledge of optical nonlinearity is pre-requisite for the utility of the nonlinear optical (NLO) materials for optoelectronic device fabrication. Z-scan experimental technique based on the principles of spatial beam distortion, has been successfully employed for years to precisely investigate the NLO parameters. In the field of optical nonlinearity, graphene has proven itself as a strong candidate material owing to the possibility of strong light-matter interactions. A detailed comparison of the NLO properties of graphene and its derivatives (G/GDs) is crucial to identify and accelerate their utility for future flexible optoelectronic device applications. Herein, we share the experimental records of the optical nonlinearity in G/GDs, obtained from the well established Z-scan technique from the available literature, reported in the period from 2009 to 2019 and were extracted from the provided raw data [1]. The data sheet includes material composition, characteristics of the excitation laser source (operating wavelength, laser energy/power/intensity) and the NLO parameters (nonlinear absorption (NLA), nonlinear refraction (NLR), saturation intensity, optical limiting threshold). For practical use, they are tabulated in the present paper and will enable users to search the material data and filter down the set of desired materials using given parameters for their possible optoelectronic device applications. The data is related to the research article entitled “Unraveling absorptive and refractive optical nonlinearities in CVD grown graphene layers transferred onto a foreign quartz substrate” (Agrawal et al., 2019) [2].


a b s t r a c t
The knowledge of optical nonlinearity is pre-requisite for the utility of the nonlinear optical (NLO) materials for optoelectronic device fabrication. Z-scan experimental technique based on the principles of spatial beam distortion, has been successfully employed for years to precisely investigate the NLO parameters. In the field of optical nonlinearity, graphene has proven itself as a strong candidate material owing to the possibility of strong lightmatter interactions. A detailed comparison of the NLO properties of graphene and its derivatives (G/GDs) is crucial to identify and accelerate their utility for future flexible optoelectronic device applications. Herein, we share the experimental records of the optical nonlinearity in G/GDs, obtained from the well established Z-scan technique from the available literature, reported in the period from 2009 to 2019 and were extracted from the provided raw data [1]. The data sheet includes material composition, characteristics of the excitation laser source (operating wavelength, laser energy/power/intensity) and the NLO parameters (nonlinear absorption (NLA), nonlinear refraction (NLR), saturation intensity, optical limiting threshold). For practical use, they are tabulated in the present paper and will enable users to search the material data and filter down the set of desired materials using given parameters for their possible optoelectronic device applications. The data is related to the research article entitled "Unraveling absorptive and refractive optical nonlinearities in

Data
The database presented in this article describes a detailed comparison of the NLO properties of G/ GDs, obtained experimentally from the Z-scan techniques, from the available literature reported in the period from 2009 to 2019. Fig. 1 (obtained from the raw data provided for the year-wise bifurcated research publications [1]) shows a histogram to graphically display the number of experimental research articles published from 2009 onwards, which clearly suggests the increasing interest of the scientific community to examine the optical nonlinearities in G/GDs. Fig. 2 depicts a schematic diagram for the Z-scan experimental setup, employed to investigate the optical nonlinearity. Fig. 3 illustrates a tree-like classification for the graphene based materials database, where the database is primarily classified in five families, including metal decorated-G/GDs, 2D transition metal dichalcogenides (TMDs) and post-transition metal trichalcogenides (TMTs)-G/GDs, semiconductor-graphene based materials, G/GDs dispersed in various solutions and single(SL)/few(FL)/multilayer(ML) graphene material based films. Each family has several members which are characterized by a set of attributes including: composition, laser parameters (operating excitation wavelength, laser energy/power/intensity) and experimentally derived NLO parameters (NLA, NLR, saturation intensity (Is), optical limiting threshold (F th )).

Value of the Data
The data presented here is acquired using the Z-scan technique and covers the critical NLO properties of G/GDs from the previously published Z-scan experimental reports since 2009 until the end of 2019. The database can be used to assess the potential of G/GDs as possible NLO materials. The database will enable users to search the material data and filter down the set of desired materials using given parameters. The database can be further used to accelerate the development in the field of graphene based materials for their possible optoelectronic applications.
these entries makes up a material record which is highly valuable for the researchers interested in the optical nonlinearity in G/GDs from the experimental point of view.

Experimental design, materials, and methods
For all the literature presented in this article, the data was acquired from the well established Z-scan technique, pioneered by Sheik Bahae et al. [3e5], and has also been extensively described elsewhere [6,7]. Briefly, the NLO is the optics of light where NLA and NLR becomes intensity dependent. For this, a high power/intense laser light source is irradiated on the NLO material and the transmitted signal from the material was recorded as a function of intensity, varied by translating the sample through the focal plane of a tight focussing lens along its propagation (z) axis (Fig. 2). Z-scan experiment can be formed in two geometries:  was collected and focused onto the detector using another lens, and (ii) closed aperture (CA) geometry where only the on-axis beam is allowed to be collected at the detector for the determination of NLR. It is noteworthy to mention here that graphene has attracted much attention after Andre Geim and Kostya Novoselov were awarded the 2010 Nobel Prize in Physics "for groundbreaking experiments regarding the 2D material graphene". After that, this material and their derivatives decorated with other materials viz; decorated with metals, TMDs, TMTs, semiconductors has been extensively investigated for various properties (Fig. 3). This material has also gained tremendous interest in the field of flexible optoelectronic device applications because of the possibility of strong light-matter interactions and flexible nature.
Although, there are a number of theoretical as well as experimental reports published in the field of optical nonlinearities in G/GDs. Herein, only the experimentally derived optical nonlinearity employing Z-scan technique has been listed (Table 1). Usually, OA experimental curve/result exhibits either a sharp peak or valley at the focal plane of the tight focussing lens as a consequence of saturable absorption (SA) or reverse saturation absorption (RSA), respectively. However, in graphene based materials, a combination of SA and RSA has also been observed where the transmittance from the material is found to increase at both the ± z-direction with respect to the focal plane, followed by a dip at the focus [2]. On the other hand, under CA geometry, the far-field on-axis normalized transmittance as a function of traversed distance exhibits a peak followed by a valley or vice versa. The prefocal peak (valley) and postfocal valley (peak) in the experimentally obtained curve indicates the negative (positive) sign of the NLR coefficient. These parameters were obtained from the best possible theoretical fitting to the experimental Z-scan profile depending upon the property of the grown material. The theoretical fitting of the experimental Z-scan profile is based on various phenomenon including; multi-photon absorption (n-PA, where integer n > 1), SA, RSA, NLO scattering, thermal lensing or a combination of these effects. Further details regarding the functions used for the fitting of the experimental data curves are given elsewhere [2e7]. This work reflects the state-of-theart of the novel graphene material and the NLO properties are not equally renowned for every derivative due to the lack of literature data. In view of this, listing of these entries (Table 1) makes up a material record which precisely represents the material property and will enable users to search the material data and filter down the set of desired materials using given parameters. The database was used by Agrawal et al. [2].  Table 1 Database for the NLO parameters (NLA/NLR/Is/F th ) investigated under various laser parameters (wavelength/laser power/energy/intensity) derived from Z-scan experimental studies for metal decorated-G/GDs, 2D-TMDs, post-TMTs-G/GDs, semiconductor-graphene based materials, G/GDs dispersed in various solutions and single/few/multilayer graphene material based films and many others. Parenthesis (column 2) indicates the reference number of published articles that are given in Ref. [1].