def cavity_round_trip_losses_approx(length, A0=1e-5, exponent=1/3):
    """Approximation of cavity round-trip losses given the cavity length, and some initial parameters.
    Inputs:
    -------
    length: float
        length of the cavity
    A0: float
        losses for a 1 meter cavity. Default is 10 ppm.
    exponent: float
        exponent of the length factor. Default is 1/3.
    """
    return A0 * length**exponent