Liquid laser cavities and waveguides. III. Radiation coupling-out and fluorescence under uniform excitation. ‘Evapolators’

An investigation was made of laser radiation coupling-out from totally reflecting closed liquid cavities by local frustration of total internal reflection with the aid of internal water spheres and external contact with a substrate or a prism. A rotating drop of ethanol containing rhodamine B in an envelope of liquid C₈F₁₈ generated laser radiation with a divergence of several angular degrees and an efficiency up to 5% relative to the excitation energy. A transparent drop of ethanol with rhodamine B, suspended in air, and subjected to uniform pumping was used to determine the depth of the zone in which lasing took place in a liquid cavity. An increase in the integral (during the pump time) fluorescence energy from a selected internal part of this drop, which did not participate in lasing, on increase in the excitation flux was in agreement with the expectations and it began to fall at high pump intensities. Characteristics of oscillations in immiscible liquids which evaporated in an evaporator — oscillator (‘evapolator’) were discussed.