Kassahun, Fesseha (PhD)Siyum, Yibeltal2018-07-092023-11-092018-07-092023-11-092011-06http://10.90.10.223:4000/handle/123456789/7404Applying c-number Langevin equations, we have calculated the Q function for the two- mode coherent and subharmonic light. We have then determined the Q function for the superposition of these two light beams. With the aid of the pertinent Q functions, we have obtained the mean and variance of the photon number sum and di erence for the two-mode coherent light, the two-mode subharmonic light, and the superposition of the two-mode coherent and subharmonic light beams. We have found that the signal and idler modes are separately in chaotic states. We have also found that the mean photon number for the superposition of two-mode coherent and subharmonic light turns out to the sum of the mean photon number of the individual light beamsenSubharmonic Light BeamsTwo-Mode Coherent and Subharmonic Light BeamsThesis