You ask me what is consciousness, but I ask you, what is not consciousness? Everything is made of consciousness.
When you go deep into that empty space that you are feeling in meditation, three things happen. At the beginning of the meditation, you don’t see anything, you just see emptiness, but when you put attention there, when you continue there, then you start feeling the vibrations. This is called spandana, when you feel some vibrations, some sensations, and then that vibration becomes light.
So the first step is really nothing but relaxation, and then from there feeling the energy, sensations, vibrations, and then it becomes light.
But when you can’t just sit, and say things like, “Oh, where is the vibration?”, or “I want the light now,” it’s not going to happen, forget about it. Expectation itself keeps you in a very excited state of consciousness, and keeps your mind on the surface level, so it doesn’t let you go in.