Absolute value of a complex number

Question

I want to calculate |xx|^2.
Why can't Mathematica just calculate it?
What am I supposed to do here? I just want it to actually calculate it, so that there are no imaginary numbers left.
Is that so hard?

xx = (2 I E^(-I a k) k k1)/(2 I k k1 Cosh[a k1] + (k - k1) (k + k1) Sinh[a k1]);
FullSimplify[
 Assuming[{Element[k1, Reals], Element[k, Reals], Element[a, Reals]}, 
  Abs[xx]]]

OUT:

{2 E^Im[a k] Abs[(k k1)/(
   2 I k k1 Cosh[a k1] + (k - k1) (k + k1) Sinh[a k1])]}

similarly:

FullSimplify[xx*Conjugate[xx]]

OUT:

(4 E^(-I a k + I Conjugate[a] Conjugate[k])
     k k1 Conjugate[k k1])/(Conjugate[
     2 I k k1 Cosh[a k1] + (k - k1) (k + k1) Sinh[
        a k1]] (2 I k k1 Cosh[a k1] + (k - k1) (k + k1) Sinh[a k1]))}

Answer 1

Abs[xx] // ComplexExpand // Simplify

ComplexExpand[expr] "expands expr assuming that all variables are real." (Documentation)