The Swiss international has joined the Potters from Inter Milan on a five-year deal for fee of £12million after a long chase by the Staffordshire club.
After putting pen to paper on his lengthy contract, the 23-year-old winger spoke of the club's desire to sign him and admitted it was nice to finally have the deal completed after plenty of discussion.
"Over the past three days I have met great people at the club and witnessed the wonderful atmosphere at the Britannia Stadium on Sunday. That experience was overwhelming.
"My special thanks go to the manager, Mark Hughes, Chief Executive Tony Scholes and Mark Cartwright for their work in helping to make this deal happen over the past few months.
"I sincerely appreciate it so much, and will give my utmost to pay them and the supporters back on the pitch over the coming months and years.
"I can't wait to meet my new teammates and make my debut for the Club. It feels great to finally be a Potter!"