Dendritic macromolecules, called "dendrimers," are a new category of hyper-structured material. Their long branching chain and the high degree of control over regular molecular weight creates a three-dimensional structure that is roughly spherical or globular. In optical applications, radiative action from the high-gain medium, containing small particles such as dendrimers, may be altered significantly under coherent optical excitation. Using a homogeneous gain medium containing dendrimers increases the stimulated emission efficiency and facilitates fine-tuning the laser modes. An optical input-output threshold behavior above which laser emission with a linewidth of less than 0.1 nm was observed is identified, even though the optical system lacked a real optical cavity. The input threshold energy from the gain medium was much smaller than the energy from the pure dye solution. The chapter describes the spatial light confinement in DCM. /dendrimer media, which generates a resonant mode in lasing action. The laser emission is characterized by (1) the appearance of resonance peaks with lines less than 0.1 nm, (2) a clear threshold excitation intensity for lasing, (3) a high degree of polarization above the threshold, and (4) increased coherency. Encapsulating the laser dye into the dendrimer increases the optical gain of the emitting media. More importantly, the emission process by the resonant modes is applicable to laser-like emission. The results show that a random optical system consisting of emitting materials, optical excitation, and cavity modes can be used to fine-tune mirrorless optical devices, even in small-device applications.
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