The Intensity Fluctuations And Linewidth Of The One-mode Dressed State Lasers From Cascade Three-level Atom

Laser has excellent coherence, which is of great importance in the field of optic and practical applications, have been paid much attention since its birth. As the noise accompanied by, which makes the laser produces a limit linewidth and coher-ence has certain restrictions in the process of the production of laser. So, the research on noise, which is a great significance for the improvement of noise suppression and laser coherence.Previous to this, the research on noise focus on quantum noise, pump noise and the correlations between the former two, but in this thesis, we choose Man-del parameter Q to characterize the intensity fluctuation and study the connection between the intensity fluctuation, linewidth and intensity of the laser, we choose a system with cascade three-level atom, which driven by two strong classical fields, the optic field a generated from level|2)to|1). We give the master equation and the Hamiltonian of the system, then rewrite them in the dressed representation. Firstly, we use the Heisenberg-Langevin approach to get the operator Langevin equations and c-number Langevin equations; secondly, calculate the non-vanished c-number d-iffusion coefficients; thirdly, take advantage of steady state conditions to obtain the steady-state solution; finally, utilize the previous conditions to calculate the expres-sion of intensity, linewidth and fluctuation of the laser. Draw the image of various physical quantities with software, adjust the value of each parameter and analyze its change law, draw some conclusions. Through research we found that, decrease as the intensity fluctuation, but narrower the linewidth and increase the coherence; there are some restraint on the intensity fluctuation in a way by increasing the intensity of the laser generated by the system.