What kind of grass is this? It is found in one of zen garden my friend took the picture from

Looks more like a non-grass groundcover - I think it's irish moss (Sagina subulata). Here's a photo from a zen garden site showing a similar effect to your photo. You may find the information in the linked site useful in constructing your own garden.

It looks more like a type of moss to me rather than grass. It's so short and dense, like a carpet. Perhaps searching for "Zen garden moss" would give you some ideas for species to grow in your own garden.