Ultrahigh intensity lasers, based on the chirped pulse amplification (CPA) technique, have been excellent tools in exploring the physics of superintense laser-matter interactions and related applications. Strong field physics, including laser-driven charged particle acceleration and strong field quantum electrodynamics, has been investigated using ultrahigh intensity lasers. In order to enhance the achievable laser intensity by reducing the pulse duration, the post-compression of a 100-TW Ti:Sapphire laser using the spectral broadening in thin solid plates and the dispersion compensation with chirped mirrors was investigated. Through the post-compression, the pulse duration was shortened from 23 fs to sub 10 fs, which can double the peak-power of the laser. This kind of post-compression of CPA lasers has been studied as a cost-effective method to enhance the peak power of ultrashort high power lasers. It is noted that the spatial beam quality is a critical factor in performing the post-compression of an ultrahigh power laser. Since the spatial quality can be degraded by the intensity-dependent nonlinear process, the use of a smooth flat-top beam profile is necessary for the spectral broadening process. To prevent the degradation of a post-compressed beam in the 100-TW laser, the spatial uniformity of the laser beam profile was improved using a vacuum spatial filter with a set of slit filters. The spatial filter, consisting of two cylindrical lenses, a spherical lens, and two slits, was installed before the compressor, providing a smoothened beam for post-compression. This spatial filtering effectively removed hot spots of the laser beam, which might develop intensity spikes when self-focusing occurs after passing through the nonlinear plate. In addition, the focusing quality of post-compressed pulses was investigated since wave front distortion can be induced during the post-compression process due to intensity-dependent refractive index. In order to correct the wavefront distortion, an adaptive optics system with a deformable mirror (DM) was employed. Through the wavefront-corrected post-compression, the focus quality was improved, which effectively enhanced the peak-intensity of post-compressed laser pulses. This post-compression method with good beam quality will be an effective tool in enhancing the power of a PW laser to achieve even higher laser intensities than the current intensity record of 10²³ W/cm² obtained with the CoReLS 4-PW laser.