Cutoff frequency of transfer function at -6 dB
I don't recognize your transfer function as one of the classic low-pass-filter implementations. A Butterworth filter, for instance, would be:

$$
H(s) = \frac{f_c^2}{s^2+1.414f_cs+f_c^2}
$$

note: for me, it's unusual to see the use of \$f\$ instead of \$w\$ in these formulas, but mathematically it should be equivalent, as long as you use \$s=jf\$ instead of \$s=jw\$