Photonic crystal (PhC) has offered a powerful means to mold the flow of light and manipulate light-matter interaction at subwavelength scale. Silicon has a large refraction index and low loss in infrared wavelengths, which makes it an important optical material. And silicon has been widely used for integrated photonics applications. In this paper, we have reviewed some recent theoretical and experimental works in our group on infrared two-dimensional (2D) air-bridged silicon PhC slab devices that are based on both band gap and band structure engineering. We have designed, fabricated, and characterized a series of PhC waveguides with novel geometries, PhC high-quality (high-Q) cavity, and channel drop filters utilizing resonant coupling between waveguide and cavity. These devices are aimed to construct a more flexible network of transport channel for infrared light at micrometer/nanometer scale. We have also explored the remarkable dispersion properties of PhCs by engineering the band structures to achieve negative refraction, self-collimation, superprism, and other anomalous dispersion behaviors of infrared light beam. Furthermore, we have designed and fabricated a PhC structure with negative refraction effect and used scanning near-field optical microscopy to observe the negative refraction beam. Finally, we have designed and realized a PhC structure that exhibits a self-collimation effect in a wide angle range and with a large bandwidth. Our works presented in this review show that PhCs have a strong power of controlling propagation of light at micrometer/nanometer scale and possess a great potential of applications in integrated photonic circuits.