How get parametr array?

How get parametr array?

Code:
var photo2 ='[{
"photo":"c8375afbbd:x",
"sizes":[["s","9458927","1d20","RfIuuZB51yM",75,64],["m","9458927","1d21","HALC4aM1hyM",130,111],["x","9458927","1d22","-e8mBA0nmOU",420,360],["o","9458927","1d23","GFqFFIuRFOE",130,111],["p","9458927","1d24","9twLTScmx5c",200,171],["q","9458927","1d25","XikD8ZmYFRs",320,274],["r","9458927","1d26","qAUIuroqtYE",420,360]],
"kid":"7bf1820e725a4a9baea4db56472d76b4"}]
';
When i do:
alert(photo2[0].photo);
i get undefened.
Why i get error and how aright get argument photo in array photo ?