Step 1.
First of all create a new Photoshop document with a black background. Create a new layer , choose the elliptical marquee tool and and make a circular selection (a). Choose the gradient tool and set it to reflected gradient (b). Set the foreground color to white and the background color to black, and then drag from the center of the selection to create a gradient (c)
(a)

(b)

(c)

Step 2.
Keep the gradient selected, contract (select > modify > contract) the selection by 2 pixels (a), and delete the area that’s selected (b)
(a)

(b)

Step 3.
Zoom in to 300%, create a new layer and use the elliptical marquee tool to create an oval (a). Choose the gradient tool and set to linear gradient. Set the foreground color to dark grey (5C5C5C) and the background to black, and drag from the top of the selection to the bottom, to create the gradient (b).
(a)

(b)

Final Result:

Via : Black Button