Femtosecond time scale allows us to follow and control atomic and molecular motion. The atomic vibrations happen in the range of femtosecond scale. Thus, femtosecond technology effectively measures the atomic vibration. However, to determine electron motion, one needs to reach sub-femtosecond time scale that is in attosecond time scale. High Harmonic Generation (HHG) is a non-linear process that converts infrared light to shortest wavelength, such as in the XUV regime. HHG allows to explore electronic motion and to control electron dynamics. HHG easily reaches to XUV region and is enabling attosecond pulse generation. In this thesis we focused to generate attosecond pulses by using noble gases and their mixtures. We used only argon gas, only hydrogen molecule and their mixture with neon gas. We wanted to improve the conversion efficiency (10^-6) of the fundamental light into high harmonics. We use Ne and H2 gas mixture to look enhancement of the HHs.