Silicon integrated Optical Phased Arrays (OPA) have been widely studied for wide and accurate beam steering applications, taking advantage of the high power handling capability, the stable and precise optical beam control, and the CMOS fabrication compatibility to realize low-cost devices. Both one-dimensional and two-dimensional silicon integrated OPAs have been demonstrated, and beam steering over a large angular range with versatile beam patterns have been achieved. However, existing silicon integrated OPAs are based on single mode operation, tuning the phase delay of the fundamental mode amongst phased array elements and generating a beam from each OPA. Whilst generating more beams for parallel steering are feasible by using multiple OPAs integrated on the same silicon circuit, the device size, complexity as well as power consumption increase substantially. To overcome these limitations, in this research, we propose and demonstrate the feasibility of designing and using multimode OPA to generate more than one beam from the same silicon integrated OPA. The overall architecture, multiple beam parallel steering operation principle, and key individual components are discussed. Results show that with the simplest two modes operation, the proposed multimode OPA design principle can realize parallel beam steering to reduce the number of beam steering required over the target angular range and the power consumption by almost 50%, whilst minimizing the device size by more than 30%. When the multimode OPA operates with a larger number of modes, the improvements on the number of beam steering, the power consumption and the size increase further.