Spherical Cavity
A transparent dielectric sphere, such as a liquid droplet, also forms an interesting optical cavity. In 1986 Richard K. Chang et al. demonstrated lasing using ethanol microdroplets (20–40 micrometers in radius) doped with rhodamine 6G dye. This type of optical cavity exhibits optical resonances when the size of the sphere or the optical wavelength or the refractive index is varied. The resonance is known as morphology-dependent resonance.
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