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The optimum self-focussing materials with an intensity-dependent refractive index and the realization of the ability of these materials to produce intensity dependent phase shift in all optical photonic devices have become a topic of continuous investigation. Many organic materials including dye-doped polymer films are creating interest due to their advantages in terms of enhanced efficiency, and optimum mechanical properties to fabricate reliable devices. In this paper, we have studied the nonlinear optical properties like nonlinear absorption and nonlinear refraction of a two-photon fluorescent dye DASPB doped in Polymethyl methacrylate-methacrylic acid (PMMA-MA) polymer matrix using open aperture and closed aperture Z-scan experimental methods by means of low power continuous wave (CW) laser beam. The optical limiting properties of these films are also studied using Type 1 and Type 2 configurations at different input powers using continuous wave (CW) laser beams of 532 nm wavelength. The nonlinear refractive index n2, nonlinear absorption coefficient β, changes in refractive index with input intensity, and the magnitude of third-order optical nonlinearity of the dye-doped film are experimentally determined. The saturated output power for type 1 and type 2 optical limiting are determined. The input limiting threshold and saturated output power level for both type 1 and type 2 optical limiting configurations are recorded. DASPB dye-doped in PMMA-MA polymer film has shown saturation absorption at lower input irradiance and reverse saturation absorption along with two-photon absorption at higher input irradiance and hence found to be a potential candidate for the third harmonic property based photonic devices.

The third harmonic optical applications such as optical phase conjugation, image processing, optical switching, and optical limiting in Photonics requires efficient nonlinear optical materials to be used with low power laser beams. During the last three decades, organic molecules have attracted the attention of many researchers due to their high nonlinear optical susceptibility and the possibility of tailoring their properties suitable to be used to protect optical detection components and devices such as human eyes and optical sensors, by controlling the output energy on the image plane below the desired level. Extensive studies have been performed and reported for the case of single crystals of organic molecules, organic molecules in liquid solutions, and organics and organometallics doped in various solid substances. One of the major benefits of organic optical materials is that they are usually much less costly and easier to process in device form than their inorganic materials. In this paper, an extensive literature survey on nonlinear optical materials is depicted. This includes review of organic nonlinear material research, materials for reverse saturation absorption, molecules for two-photon and multi-photon absorption, experimental techniques for nonlinear refraction, nonlinear absorption, optical limiting, and optical phase conjugation. Finally, the review includes the materials used in photonic devices, materials used for optical phase conjugation like nonresonant media and resonant media including absorbing liquid and solid materials, lasing gain media, metal vapors, and photorefractive materials.

Materials with exceptional third order nonlinear optical properties are critical to the continuing development of photonics and electro-optical devices such as those used in optical communications, networking, optical computation for signal processing, and data storage devices. The nonlinear optical material research is generally focussed on improving the efficiency of optical wavelength conversion, optical amplification, nonlinear absorption, refractive index changes etc. which are input light intensity dependent. During last few years, the organic dye-doped polymer films are getting more attention due to their advantages in fabricatingoptimum photonics devices. In this paper, we have studied the nonlinear optical properties like nonlinear absorption and nonlinear refraction of an azo dye Disperse Orange-25 (DO-25) doped in Polymethyl methacrylate-methacrylic acid (PMMA-MA) polymer matrix using open aperture and closed aperture Z-scan experimental methods for continuous wave (CW) laser input. The optical limiting properties of these films are also studied using Type 1 and Type 2 configurations at different input power using continuous wave (CW) laser beams of 532 nm wavelength.The nonlinear absorption coefficient, nonlinear refractive index, and saturated output power for type 1 and type 2 optical limiting are determined.

Nonlinear optical materials with optimum properties are essential in continuous developmentof photonic and electro-optical devices, used in optical communications, networking, opticalcomputation for signal processing, and data storage equipments. The changing trend is to useorganic materials/dyes that exhibit exceptional nonlinear optical properties instead ofconventional materials which have comparatively low nonlinear properties. These organicmaterials/dyes are easy to prepare in solution or solid form. The resulting organic material has a low dielectric constant, eliminating the need for poling while maintaining the refractive index. However, these organic materials have few of the drawbacks inherent in the processing of comparable inorganic materials like of intense light induced degradation or bleaching and aggregation at higher dye concentration. In order to overcome these drawbacksand for effective use of highly nonlinear dyes, the dye molecules are doped in polymermatrix. This idea of dye-doped polymer material matrix may increase the concentration ofabsorptive or fluorescence centers as well as the opto-chemical and opto-physical stability.In this paper, we have discussed the strategic advantages of dye-doped polymer nonlinearmaterials in comparison with organic and inorganic nonlinear materials for optical phase conjugation and all optical switches in future photonics technology. This was done bystudying the linear optical properties and nonlinear optical Phase Conjugation properties oftwo azo dye-doped polymer films by considering organic dyes disperse orange (DO-25) anddisperse yellow (DY-7) doped in a polymer matrix Polymethyl methacrylate methacrylic acid(PMMA-MA). The nonlinear optical phase conjugation properties are studied usingDegenerate Four Wave Mixing set-up using 532 nm wavelength CW laser beam. The effectof dye concentration, intensity of backward, forward pump, and inter beam angle betweenprobe and forward pump beam on phase conjugation reflectivity are also studied andcompared.

In this paper, we have studied the linear optical properties and nonlinear optical Phase Conjugation properties of two azo-dye-doped polymer films by considering organic dyes disperse orange (DO-25) and disperse yellow (DY-7) doped in a polymer matrixPolymethyl methacrylate methacrylic acid (PMMA-MA). The nonlinear optical phase conjugation properties are studied usingDegenerate Four-Wave Mixing set-up using 532 nm wavelength CW laser beam. The effect of dye concentration, the intensity of backward,forward pump, and the inter-beam angle between the probe and forward pump beam on phase conjugation reflectivity are also studied andcompared.