在mathematica中对一个复函数的模，再积分结果还是复数形式，求教各位大神。请问这是什么问题？
 

NIntegrate[
Conjugate[
Exp[-Pi/775*y^2/(Pi*0.22^2/775 - 2*I*2.5)]*
Integrate[
Exp[-z^2/0.22^2]*Exp[-I*(Pi/775)/(2*2.5)*(x - z)^2], {z, -0.2,
Infinity}]] Exp[-Pi/775*y^2/(Pi*0.22^2/775 - 2*I*2.5)]*
Integrate[
Exp[-z^2/0.22^2]*Exp[-I*(Pi/775)/(2*2.5)*(x - z)^2], {z, -0.2,
Infinity}], {x, -0.7, 0.7}, {y, -Sqrt[0.49 - x^2],
Sqrt[0.49 - x^2]}]