Controllable Polarization of Lasing Emission From a Polymer Microfiber Laser

Studies of the transition between amplified spontaneous emission and optical lasing in ultrahigh-Q polymeric micro-pedestals

In this work, we demonstrate the properties of Rhodamine B-doped polymeric cylindrical microlasers to perform either as gain amplification devices through amplified spontaneous emission (ASE) or as optical lasing gain devices. A study based on different %wt concentrations of microcavity families with distinct geometrical features demonstrates the characteristic dependence on either gain amplification phenomena. Principal component analysis (PCA) discriminates the relationship between the main ASE and lasing properties and the geometrical aspects of the cavity families. ASE and optical lasing thresholds were found, respectively, as low as 0.2 μJcm^-2 and 0.1 μJcm^-2 passing the best-reported microlaser performances in literature for cylindrical cavities, even in comparison with those based on 2D patterns. Moreover, our microlasers showed ultrahigh Q-factor of ∼3 × 10⁶, and for the first time, to the best of our knowledge, a visible emission comb constituted by above a hundred peaks at 40 μJcm^-2 with a registered free spectral range (FSR) of 0.25 nm corroborated through the whispery gallery mode (WGM) theory.

All-optically phase-induced polarization modulation by means of holographic method

Phase-induced polarization modulation has been achieved experimentally by means of the all-optical holographic method. An extra spiral phase is added to a Gaussian beam and then a holographic grating is recorded through the interference of a Gaussian beam and the phase-vortex beam with the same linear polarization state in an azobenzene liquid-crystalline film. We report here that the polarization state of the diffraction light from the recorded grating is different from that of the incident light, while no polarization variation occurs for the holographic grating recorded by two Gaussian beams. The phase-induced polarization modulation is mainly attributed to the formation of birefringence in the film generated by phase vortex, which is investigated through the ripple patterns resulting from the competition between photoinduced torques and analysed by the Jones matrix. The experimental results could enrich the connotation between optical parameters and offer a method to realize polarization modulation through phase control.