Femto-second laser irradiation on a material can initiate intensity dependent nonlinear optical phenomena. This work focuses on multiphoton absorption, more specifically, two photon absorption (TPA) analyses. Open aperture Z-scan (OA-ZS) technique has been employed to measure TPA coefficients and TPA cross sections (TPCS). An ultrashort 800 nm Ti:Sapphire laser (FEMTOPOWER Compact PRO) with an average power of 800 mW and repetition rate of 1 kHz has been used in ZS setup. A femtosecond (10-15 s) laser pulse attains very high intensity in ultrashort time. In this work, pulse intensity ~ 1011 W/cm2 has been used. In OA-ZS, a thin sample is scanned along the laser propagation direction, within the focal spot, to measure intensity dependent changes in optical absorption. Experimental TPA data is extracted from the transmitted and reference laser beams. We have developed a C sharp (C#) based software which can extract TPA coefficients via theoretical fitting of experimentally obtained data. Linear absorption coefficients were measured via UV-vis spectroscopy which have been utilized in TPA calculations. TPA is known to be a highly sensitive process. Two photon cross sections (TPCS) of Rhodamine B and Rhodamine 6G solutions in MeOH have been measured. Understanding the factors affecting TPA is essential to assess the potential applications especially in the field of medicine such as, TPA induced photodynamic therapy and 3D photo-imaging. An in depth analysis has been carried out to assess the influence of medium as well as laser parameters on TPCS and relative TPA trends. The explored laser parameters are laser energy and pulse width. The varying medium parameters are dye solution concentrations and sample length (cuvette size). True value of TPCS is found to be independent of change in laser energy and pulse width (laser intensity). However, relative TPA is enhanced by increasing pulse energy due to increased transition probability. Shorter pulse width resulted in reduced TPA due to saturation effects. Increase in solution concentration has decreased TPCS due to agglomeration effects. An increase in TPCS with increased sample length is observed owing to an overall increase in TPA absorbers. Assessment of TPA sensitivity on laser beam and dye parameters allows better control for desired applications. Three glasses, namely, GIL49, BK7 and Glass B were irradiated by 1700 keV Au+ ion beams. Samples were post annealed at 600oC for 6 hrs. Penetration depth and distribution of Au+ ions having 1700 keV energy within glass substrates was estimated by TRIM simulations. Detailed calculations with full damage cascades were performed for each sample, taking into account the chemical composition of glass substrates. TRIM results reveal that there is no significant change in ion range, straggling and ion distribution with the change in the substrate composition. Linear absorption has been analyzed by UV-visible spectroscopy. Z scan results showed a difference in TPA coefficients for all three glasses. Highest TPA coefficient has been found in case of BK7. TRIM simulations for all three samples has given same value for total target damage. Therefore, the difference in TPA coefficient can be attributed solely to annealing induced crosslinking and reformation of glass matrix. Which leads to agglomeration of metallic particles within the glass matrix. Highest agglomeration is suspected in BK7 as its glass transition temperature is lower than annealing temperature. This is also supported by our linear absorption analyses, where, maximum absorption wavelength shifted towards longer wavelengths for BK7. Linear absorption and TPA in Cu ion embedded GIL49 has been analyzed. Metal ion embedded GIL 49 via ion exchange method has a lower value of TPA coefficient and linear absorption coefficient as compared to that in case of ion irradiation method. This can be attributed to lesser number of embedded ions and lesser ions penetration via ion exchange method. TPA in materials used in this research work has significant applicability. Rhodamine dyes can be used in synthesis of novel TPA materials for various applications. These novel materials include biomaterials such as, DNA doped Rhodamine B/Poly Vinyl Alcohol thin films. This allows tailoring of TPA properties in biomaterials for their potential applications in photonics device manufacturing. Rhodamine dyes can be incorporated in microstructures formed by TPA induced 3D polymerization. These microstructures have dyes molecules at specific sites and have broad fluorescent spectrum which can be tuned by choosing excitation positions and different excitation wavelengths. These engineered structures can be used in micro-devices. TPA in near infrared range allows deep penetration, minimal damages and high spatial resolution. TPA in metal embedded glasses can be used in optoelectronic device fabrication such as, optical limiters, optical sensors and all-optical switches.