[{"coursesMarks":{"_id":"634a9be567a1f07be02f71d8","courseCode":"cse1201","courseTitle":"SP"}},{"coursesMarks":{"_id":"634a9be567a1f07be02f71db","courseCode":"cse1203","courseTitle":"DS"}}]

db.collection.aggregate([{$match:{}},{$group:{_id:null,courses:{$push:"$coursesMarks"}}},{$unset:"_id"}])