Entropy evolution law in a laser process

Rui Rui, He, Junhua +3 more

Fu-Yi You, Junhua Chen, Hong-Yi Fan

We analyze the laser process with three different initial states using the entangled state representation, obtain the evolution law of the mean photon number, the entropy, the specific entropy, the second degree of coherence and the Wigner functions, and find out the common characteristics of these three processes.

Adi R. Bulsara, William C. Schieve

Xavier de Hemptinne

Xiang-Guo Meng, Bao-Long Liang, Jian-Ming Liu +1 more

Using the integration within ordered products, we obtain the analytical density-operator evolution of the general quadratic state ρ 0 in a laser channel, which always maintains the same form as the initial density operator ρ 0. Introducing the differential representation of the von-Neumann entropy and two important resemble formulas, we analytically and numerically investigate the entropy evolution of the state ρ 0 in a laser channel, which is determined by not only the competition of the gain and loss of the laser channel, but also the coefficients α, β of the initial quadratic state ρ 0.

Rui He, Junhua Chen, Hong-Yi Fan

Based on the density operator’s operator-sum representation recently obtained by Fan and Hu for a laser process (Opt. Commun., 2008, 281: 5571; Opt. Commun., 2009, 282: 932; Phys. Lett. B, 2008, 22: 2435), we derive the evolution law of Wigner operator, the law is concisely expressed in the normally ordered form $\Delta (\alpha ,\alpha ^* ,t) = \tfrac{T} {\pi }:\exp [ - 2T(a^\dag e^{ - (\kappa - g)t} - \alpha ^* )(ae^{ - (\kappa - g)t} - \alpha )] $ :, where g and κ are the cavity gain and the loss, respectively, and T ≡ (κ − g)(κ + g − 2ge−2(κ−g)t )−1:, When $t = 0,\Delta (\alpha ,\alpha ^* ,t) \to \tfrac{1} {\pi }:\exp [ - 2(a^\dag - \alpha ^* )(a - \alpha )] $ ;, which is the initial Wigner operator. Using this formalism the evolution law of Wigner functions in laser process can be directly obtained.