Kassahun, Fesseha (PhD)Getachew, Solomon2018-07-032023-11-092018-07-032023-11-092011-06http://10.90.10.223:4000/handle/123456789/5926In this thesis we study the statistical properties of two-mode coherent and laser light beams in a cavity coupled to two-mode vacuum reservoir. We obtain c-number Langevin equations using the pertinent master equation. Making use of the solutions of the resulting c-number Langavien equations, we calculate the antinormally ordered characteristic function de ned in Heisenberg picture. With the help of this characteristic function, we determine the Q function for a two-mode coherent light as well as for a two mode laser light. Then the Q function is used to calculate the mean and variance of the photon number sum and di erence. On the other hand, using the aforementioned Q functions, we determine the Q function for the superposition of two-mode coherent and laser light beams. Finally, using the resulting Q function, we obtain the mean and the variance of the photon number sum and di erenceenTwo-Mode CoherentThesis