  We have demonstrated a 165 micron oblate spheroidal microcavity with free
spectral range 383.7 GHz (3.06nm), resonance bandwidth 25 MHz (Q ~ 10^7) at
1550nm, and finesse F > 10^4. The highly oblate spheroidal dielectric
microcavity combines very high Q-factor, typical of microspheres, with vastly
reduced number of excited whispering-gallery (WG) modes (by two orders of
magnitude). The very large free spectral range in the novel microcavity - few
hundred instead of few GigaHertz in typical microspheres - is desirable for
applications in spectral analysis, narrow-linewidth optical and RF oscillators,
and cavity QED.
