The young winger has thanked his former employers for transforming him into the exciting talent he is today.
"I owe them massively - I'd been at Southampton since I was seven," he told arsenal.com. "They put so much hard work into me and the fans down there welcomed me into the first team so warmly.
"I couldn't have asked for more, so I've got a lot of time for them and I hope to be able to play there again one day and show my appreciation. I'll always have a place in my heart for them."