From Wookieepedia how a lightsaber works:
The weapon consisted of a blade of pure plasma emitted from the hilt and suspended in a force containment field. The field contained the immense heat of the plasma, protecting the wielder, and allowed the blade to keep its shape. The hilt was almost always self-fabricated by the wielder to match his or her specific needs, preferences and style.
It seems the Dark Lords of the Sith Empire were ultimately responsible for the advancement of lightsabers, replacing the belt-mounted power pack with a power cell within the hilt. An internal superconductor was introduced, which transferred the returning looped energy from the negative-charged flux aperture back into an internal power cell. With this modification, the power cell would only expend power when the energy loop was broken, such as when the lightsaber cut something, solving the power supply problem. According to the Tedryn Holocron, the Sith also created the schematics for the first double-bladed lightsabers.
High levels of energy generated by a high-output Diatium power cell was unleashed through a series of focusing lenses and energizers that converted the energy into plasma. The plasma was projected through a set of lightsaber crystals that lent the blade its properties and allowed for the adjustment of blade length and power output. The ideal number of crystals was three, though only one was required
Once focused by the crystals, the plasma was sent through a series of field energizers and modulation circuitry within the emitter matrix that further focused it, making it into a coherent beam of energy that was projected from the blade emitter. The blade typically extended about a meter before being arced by the blade containment field back to a negatively charged fissure ringing the emitter, where it was channeled back to the power cell by a superconductor, completing the circuit.
Okay so from all of these quotes here's how I understand a lightsaber to work. There's a powercell in the handle. The power is then focused through crystals that act as a lens. It is preferable to use three crystals but you can make a lightsaber with just one. Then the energy goes through an emitter matrix which further focuses it into a coherent beam. The projected beam goes out about a meter on average then arcs back by the blade containment field(which is somehow done with the force) back into the emitter, and then back to the powers cell, which completes a circuit.
This means that it's a one way shot, a straight line out. In addition it says that the Sith had to design a two sided blade, which I assume is a regular lightsaber connected with separate power cells and seperate crystals to create effectively two separate lightsabers that are connected at the hilt. We see G Canon evidence of this when Darth Mauls lightsaber is cut in half in "The Phantom Menace."
So how does Kylo Ren's lightsaber have beams coming out in a cross formation at the hilt? Does he have separate crystals to focus the beams out? Is it a containment field in an irregular shape, if so how is that done? I am confused and it's possible my understanding of how the fields that generate a lightsabers form are off.
Also as a side note if you feel like addressing it and it applies: Wouldn't the cross parts coming out of the hilt take up more energy and be more for effect then for purpose? If it needs additional power cells or a larger one wouldn't that make the lightsaber much heavier and more difficult to use?
How does Kylo Ren's lightsaber make that cross shape?