Use hacking or invisibility to pass through the lasers to the terrace. Sneak up on the guards there and knock them out. After that you can hack the door to the core or obtain the password, should be on a pocket secretary or on a computer in the security control room. When inside you'll be faced with a nasty room filled with lasers. Jump or laser your way through. You can crawl through a duct accessible to the right to get to some guards and computers and a slightly better approach. Then move up to the elevator door.