Thermal vacuum state corresponding to squeezed chaotic light and its application

For the density operator (mixed state) describing squeezed chaotic light (SCL) we search for its thermal vacuum state (a pure state) in the real-fictitious space. Using the method of integration within ordered product (IWOP) of operators we find that it is a kind of one-and two-mode combinatorial squeezed state. Its application in evaluating the quantum fluctuation of photon number reveals: the stronger the squeezing is, the larger a fluctuation appears. The second-order degree of coherence of SCL is also deduced which shows that SCL is classic. The new thermal vacuum state also helps to derive the Wigner function of SCL.