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Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE

Lasing threshold conditions and output characteristics of an organic polymer optical multi-stable system with pumping and inject signal

Tingwan Wu, Junqin Feng

Published Aug 18, 2005• 0 citations
Publisher

Abstract

This paper presents some new study results on the threshold conditions and characteristics of lasing output for an organic polymer optical multi-stable system in which the medium is with pumping and the system acted with inject signal. The dynamics of light field in the medium are described with the extended forced oscillation model of optical multi-stable and lasing system. Moreover, through the theoretical analysis and numerical analogue, the gain threshold condition of amplifying under population reversion is discussed. Meanwhile the characteristics of the lasing output state with inject signal inspected. Further, the relationships of the amplifying multiple of the incident light field with the cavity detuning; and that with the two-photon detuning; also that between the two kinds detuning are found by analyzing the stationary equations. Finally, theoretical and numerical analyzing shows that the lasing frequency characteristic of such an organic polymer system with pumping and inject signal is different from the common laser. These results should be significant in some degree for both theoretical and experimental research, also application purpose.

DOI
10.1117/12.620291

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This paper presents some new study results on the threshold conditions and characteristics of lasing output for an organic polymer optical multi-stable system in which the medium is with pumping and the system acted with inject signal. The dynamics of light field in the medium are described with the extended forced oscillation model of optical multi-stable and lasing system. Moreover, through the theoretical analysis and numerical analogue, the gain threshold condition of amplifying under population reversion is discussed. Meanwhile the characteristics of the lasing output state with inject signal inspected. Further, the relationships of the amplifying multiple of the incident light field with the cavity detuning; and that with the two-photon detuning; also that between the two kinds detuning are found by analyzing the stationary equations. Finally, theoretical and numerical analyzing shows that the lasing frequency characteristic of such an organic polymer system with pumping and inject signal is different from the common laser. These results should be significant in some degree for both theoretical and experimental research, also application purpose.
In this paper the results of study on the nonlinear and lasing output characteristics of an organic polymer system, are presented. To describe the dynamics of light field in the medium, the forced oscillation model of optical multi-stable and lasing system are used. For the matter model, the material with the conjugate structure, such as polydiacetylenes which energy structure can be reduced to a three-level system considered; meanwhile the approach of efficient susceptibility is used to deduce the nonlinear susceptibility. Under these conditions, theoretical analyzing and numerical simulation shows that the system appears special output characteristics and dynamic behaviors, also instability, responding to the incident signal, especially when it satisfies both the gain condition of amplifying and that of multi-stable states. Further, the relationship between the detuning and the conditions of light amplification in this system are given out. Moreover, we find the detuning condition can describe and generalize the "frequency pulling effect", in proper situation.
This paper studies the characteristics of the nonlinear optical system in a model, which may be considered as that containing conjugate polymer, such as polydiacetylense. The dynamic equations are established through the approach of density matrix elements. The parameter conditions of laser and lasing without inversion (LWI) are discussed and the thresholds of pumping and probing fields to produce LWI are determined. The nonlinear susceptibility of the system is deduced from the density matrix equations and the forced oscillation model of laser and bistability is used to study the bi- or multi-stability of the system under lasing, or inversion without lasing (IWL) and LWI conditions. The results indicate that to realize OB or OM output in IWL or LWI situation, there must be some additional conditions on the relaxation and transition rates, also the critical output light intensity. Finally, theoretical analysis and numerical computing show that there exists unstable critical point of second kind phase transition, in such tri-stable state.
This paper presents some results on the nonlinear output charactertistics and critical behaviors of a nonlinear optical system with conjugate polymer like polydiacetylenes, in a three-level model. Based on the model of interaction of this kind of matter with the pumping field, probing field and coherent field, the nonlinear susceptibility deduced by the method of the density matrix element, and the multistable output characteristics and effects of lasing or lasing wihtout inversion are furthe studied, using the dynamic equation of the 'forced oscillation model of laser and bistability'. On the other hand, through the approach of 'quasi-thermal dynamics', we analyzed the properites of the critical point of the system. The result shows that when the system is set on a tri-stable situation there exist an unstable critical point of second kind phase transiton and near which the behavior of the system had not been reported before, as we know.
The dynamics of a two-photon laser with injected signal (TPLIS) in the limit of high quality cavity (class-A laser) is analysed by explicitly considering the underlying multi-level structure of the amplifying medium. A three-level cascade system is considered which retains the basic physics of the microscopic lasing processes. In this way the usual two-photon laser equations are consistently modified by the appearance of different dynamic frequency shifts dependent on the two-photon population inversion and on the laser intensity (ac-Stark shift). Although the basic instability scenarios are not qualitatively modified with respect to the effective two-level TPLIS, from the quantitative point of view, population-induced shifts heavily affect the threshold of appearance of instabilities.
Interaction of two coherent fields of arbitrary intensity with a general homogeneously broadened three-level molecular system for both an amplifier as well as a laser oscillator under general conditions of pumping is discussed. The amplifier solution is obtained through the time-averaged density-matrix formalism with two coherent fields treated classically. A detailed consideration of both real and imaginary parts of the electric susceptibility at pump and emission frequencies, corresponding to gain and dispersion in the active medium has been taken into account. The results obtained are used to study a number of situations for weak and strong pumping in the laser amplifier. Subsequently these are applied to a mode analysis of a unidirectional single-mode laser oscillator to determine the output characteristics of the laser and to establish conditions under which emission becomes dynamically unstable resulting in sustained oscillatory emission. The results obtained are found to be in good agreement with those of a full numerical analysis of the atomic and field coupled equations describing the system.
The behavior of a single-mode class-C laser in the presence of an injected signal is investigated theoretically in detail. We have determined the ranges of input signal strength and the frequency detuning for which the oscillations of the cavity electric field and the atomic induced dipole moment are simultaneously stable and have only one oscillation component with the frequency equal to that of the input signal (injection-locked state). One can reproduce all the previous results corresponding to class-A and class-B lasers from our results by using their relevant conditions. Finally, the energy conservation law is demonstrated for both the below-threshold and the injection-locked states of class-C laser amplifiers.