Simulation Of Photonic Diffusion In Random Laser

The phenomenon that the light waves spread and produce laser in disordered media has been widely concerned. In recent years a number of experimental and theoretical studies have shown that: The stimulated radiation in random media contains deeply physical sense and abundant physical phenomenon; people call the lasers that made up by using the stimulated radiation of random medium as the random laser.In this paper, we put forward the model of calculating the threshold gain of random laser, offer the method that work out the distribution function and the distribution of random variables with the mean free path and scattering intensity distribution have been known. The distribution function is derived by isotropic scattering of light, and then gets the random variables in line with the distribution of each scattering. Simulate the random walking of photon in random media use the Monte Carlo method, and then the threshold of random laser has been got. Discuss the relationship of the threshold gain to the photon mean free path,the radius of gain zone,the depth of gain zone and light absorption of non-gain zone .Bring a methodto lower the threshold. The theoretical results are identical with the experimental data.Two kinds of scatterings are discussed and the corresponding distribution functions are deduced in this paper. The spatial distribution of incoherent backscatter and reflectivity are deduced by simulating the process of stochastic photon movement in random medium using the Monte Carlo method. The results show that: 1, Different scattering ,have different reflectivity and spatial distribution of incoherent backscatter. As the angle of incidence increasing, the reflectivity of incoherent backscatter increases. 2, Reflectivity of incoherent backscatter decreases as the absorption coefficient of random medium increasing .By measuring the reflectivity of incoherent backscatter, we can get first the absorption coefficient and then the probability that photon is absorbed by particulate each time scattering. 3, Reflectivity of incoherent backscatter decreases as the mean free path of photon increasing .The mean free path can be got by measuring the reflectivity of incoherent backscatter , it is easier than testing coherent backscatter to get the mean free path.In the last, only one kind of scattering is discussed and the corresponding distribution function is deduced in this paper. Analyzing the geometry of the gain area, the spatial distribution of emergence laser is got by simulating the process of stochastic photon movement in random medium using the Monte Carlo method. The results show that : the laser intensity is the strongest in the normal direction. It weakens gradually with the angle increasing .The light intensity rotate on the symmetry of the normal. The spatial distribution of emergence laser is connected with the mean free path of photons in the random medium .According to these we can deduce the mean free path of the photons by measuring the spatial distribution of laser. The vast majority of emergence laser photon (generally above 95%) scatters out within the distance of three mean free path from the interface.