Sliding chin genioplasty? (Photo)

You might benefit more from jaw advancement than S.G. you could read more about it on the sites below. 

The concepts of moving the chin bone forward will make your jaw longer. Depending upon the amount of horizontal movement forward will determine whether it truly becomes more narrow in the front view. (which is what I think you mean by 'well defined'. As the amount of horizontal chin movement s not substantial, the chin bone will also need to have a width narrowing procedure done on it as well. Generally it takes about 3 weeks for most of the chin swelling to resolve and one can expect some degree of chin and lower lip numbness for a few months.

Your images are posed with the 'head being forward' position and that obscures the 'real' position of the jaw. Try to take images with the head straight up so one can see the magnitude of the change required. The sliding genioplasty can certainly change the profile view and also the frontal view. To that end, the 'width' of the jaw is important to determine how much of a change is feasible to make it look natural. Recovery varies but expect a week recovery from normal activity.