Create Array With In A Class?

I'm writing a ray tracing program that uses snell's law to trace rays through a system of lenses to examine abberations in a given design.I have a class called lens, which holds variables for example, name of the lens, description, number of elements.I want to be able to have a sub class or array within lens (or some other way to manage this data).I wont know what number of elements is until run time.

So I would need to define the array at run time.Part of the idea of my program is randomly generate lens elements within given rules (as in a massive lot), keep the top designs and continually refine them by making billions of micro adjustments to the variables that define the lens etc, which I can pick up later on as it'll save the database/variables.For example, say Lens(63).NumberOfElements = 6.

I want to be able to access Lens(63).Element(3).Radius1 Etc, there will be a bunch of variables under Element, such as Radius1, Radius2, refractive index, horizontal diameter, vertical diameter, and spacing between the next element if it isnt the first.

And Lens(70) may only have 4 elements etc. How can I define a different array size like that in the class under different parent array indexes at run time?