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When micrometre-sized polymer particles were added into a dye-doped pendant drop that acted as a quasi-two-dimensional circular resonator, we found a blueshift of the peak wavelength of its lasing spectrum. The lasing output was also enhanced by the particles. The spectral blueshift was explained by a model of dye lasing in a circular cavity. The model includes losses of the scattering particles, medium absorption and radiation leakage. An optimum particle density for maximum lasing output was deduced. The results are consistent with our experimental findings.

We have reduced the lasing threshold of a circular resonator, formed by a dye-doped pendant drop, by changing its shape from a circle to an oval. This phenomenon can be explained by the decrease of the number (p) of modes that support lasing in the resonator. A theory that connects wave and ray pictures in dealing with the cavity resonance is used to estimate p and its dependence on the eccentricity of an oval-shaped resonator. The measured lasing threshold and the calculated p have a linear relationship in agreement with our prediction.

We have observed lasing from the rim of dye-doped ethylene glycol pendant drops. Spatial-resolved spectral measurements show that the lasing wavelength varies along a vertical rim of the drop. Time-resolved measurements indicate that lasing precession occurs within the drop. Various lasing patterns due to lasing precession are explained. The measured precession periods for different pumping points are in good agreement with the calculated values based on morphology-dependent resonance theory.

We observed for the first time (to our knowledge) a new type of all optical double-quasi-steady-state photorefractive spatial soliton in a Cu:KNSBN crystal.The soliton was created without an applied electric field but with an inducing laser beam.An all optical switching effect was found in the formation of the soliton.

We present a theory of photovoltaic(PV) spatial solitons(SS's), that includes the PV contribution of a background beam(BB). The theory predicts that a dark or a bright SS can be formed in the same crystal with positive refractive index perturbation (Δn). If the ratio (R) of the effective Glass constants(EGC) of the BB to that of the signal beam(SB) is1. We have formed a one-dimensional dark PV SS in a crystal, as predicted.

Normally, when an imperfectly mode-locked 532nm ps laser is incident upon a Cu:KNSBN photorefractive crystal, no self-pumped phase conjugation can occur. We report however, for the first time to our knowledge, that if a photorefractive waveguide is first created in the crystal by a mode-locked beam of the same wavelength, then self-pumped phase conjugation can be induced for the imperfectly mode-locked beam.