The demand for more efficient and clean engines have prompted the research and development of new engine technologies. Automotive engines expected to run with leaner mixtures and higher compression ratios. Lean burn is effective to increase fuel economy whilst reducing emissions but unreliable ignition of the lean mixtures by the conventional spark plug is one of the problems which causes concerns to the engine designers. Laser induced plasma ignition is an promising technology and holds many benefits over the spark ignition because it can extend the ignitability of lean mixtures with flexibility of the ignition location and absence of electron degradation for improved engine performance with lean burn. In this study, high-speed photography is used to investigate the flame kernel growth and propagation in an optical direct injection engine using laser ignition by a Nd:YAG laser. Coupled with heat release analysis, the results demonstrate that the variations in both the laser energy and equivalence ratio have considerable influence on the flame kernel growth rate, but compared with spark ignition, the combustion process has reduced initiation time with an overall faster flame propagation speed associated much reduced cyclic variability. Discussion of the influence of laser ignition on the combustion initiation process is provided with association to an optical study in a constant volume vessel with laser ignition using Schlieren photography which reveals the profiles of the flame kernel growth history under controlled conditions.