Second harmonic light generation (SHG) was observed from as-deposited silica glass thin films suitable for waveguiding, without the need for an inversion symmetrybreaking poling treatment. Thin film stacks of up to 16 layers of alternating 2% phosphorusdoped and undoped silica glass on silica substrates were prepared and probed with a pulsed Nd:YAG laser at 1064 nm. We observed that even though these structures were not poled, they possess a net second order non-linearity with a value of the order of 0.03 pm/V. The SHG increased with the number of layers (total thicknesses between 4 and 9.6 µm have been tested) and also depended on the thickness ratio between the doped and undoped layers. Annealing at 800°C for 4 hours removed the nonlinearity completely.

No abstract

INTRODUCTION Phenomenological approach attempt to use knowledge of the bulk response. This leeds to the long standing problem of additional boundary condition in phenomenological optics. Then, one develops green's functions for an extended hydrodynamic model. Here, one consider hydrodynamic model with spatial dispersion in both the longitudinal and the transversal response function. One develops the relation between ABC and nonlocal conductivity of the surface problem. For the homogeneous bulk system, the conductivity tensor gives longitudinal and transverse conductivities. The poles of this conductivity determine Eigen solutions of the ⃖ ⃗ ̅ = 0 where ⃖ ⃗ is a differential operator containing spatial derivative. To study optical response, one has are another model called the specular reflection model, In this model the conduction electron are specularly reflected at the surface plan. This system responds like one side of a homogenous system with a mirror plane for all properties and also for the existing fields. On a

No abstract

Silica glass is a centrosymmetric material that does not support even-ordered nonlinearity. Despite the fact, its vast importance in photonic systems motivated researchers to develop techniques to break the centrosymmetric structure. However, to this day the effective nonlinearity in silica glass remains too low for practical applications in active nonlinear devices. In this study, a model of sub-dividing glass samples into multiple, alternating doped and undoped silica layers is investigated for its ability to enhance nonlinearity in silica glass. The glass samples are fabricated using a standard PECVD process. The dopant in the layers is germanium. Nonlinearity is induced in the samples using corona poling and the samples are characterized using Maker fringe measurements. The primary focus of this research is to analyze the distinctive properties of the nonlinearity profile that emerge due to certain alterations in the poling conditions. The following two steps introduce the alterations. In the first step, a set of two identical samples are poled with a positive voltage, but one of the samples is oriented in the opposite orientation inside the poling setup. One can alternatively think of it as a reversal of the electrodes. In the next step, another identical set of samples is poled in the same manner, but with a negative poling voltage. Thus, four glass samples are produced that possess unique nonlinearity profiles as shown by the Maker fringe measurements. It is observed that the intensity of SHG from the samples increases as the square of the intensity of the applied laser beam. The nonlinearity was stable and permanent for months. Different dopant types affect the Maker fringe patterns. A MATLAB hypothesis suggested that the modulation fringes for certain samples occur due to the formation of two nonlinear regions near the electrodes, each of width 5 µm. The samples which did not show modulation fringes only have a single nonlinear layer of width 9 µm. The findings of this research project can be implemented to understand the charge migration mechanism due to poling, thus enhancing the optimization capability of inducing nonlinearity in silica glass.ii