Research on Control of Spontaneous Emission in a Laser with Very Short Cavity

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1 Theory(1) Analysis of the paired-dielectic-slab-model of a very short optical cavity : This model allows for analytical expressions for the properties of a Fabry-Perot type very short optical cavity. Using this model, the spontaneous emission rate into radiative modes. which are coupled to the outer space, and that into guided modes. which travel along the dielectric slabs. are calculated on the basis of standing wave mode analysis. The angular distribution of the emission and the coupling ratio to a particular cavity mode (quasimode) are evaluated.(2) Analysis of realistic very short cavities : Similar analysis is performed for a cavity having a pair of mirrors with multi-dielectric layers using the matrix method. For calculation on the guided modes, effective density of modes are estimated and used.(3) Proposal of the concept of the effective area : For a Fabry-Perot type very short optical cavity. it is shown that the spatial fiel d distribution of the cavity resonant mode is dete … More rmined by the mirror reflectivities and the cavity length. The concept of effective area, related to the field distribution, is proposed'(4) Nonperturbative analysis : Nonperturbative analysis is made on "vacuum Rabi oscillation- and the concept of effective Rabi field is proposed.2 ExperimentOutput properties of a 2-10 mu m long optical cavities filled with Rhodamine 6G-ethanol solution, excited by a laser pulse of wavelength 520nm and of pulse duration lns, are compared with the fluorescence from the same dye solution in a cuvette. The emission peak was at 570 nm for both short cavity and cuvette. The emission spectal width decreased to 7.2na from 34nn and the pulse width was 0.92ns as compared with 6.3ns for the fluorescence. The output power versus input power in a log-log plot shows a slope of 2 over the mesured range, which range corresponds, probably, to the transient from fluorescence to lasing. The minimum input energy was 0.5 mu J. Improvement in sensitivity of power measurement is needed for further study. Less