We report the measured finesse value of similar to 390 in nonabsorbing
AlxOy/AlGaAs cavities. The nonabsorbing cavity consisting of a bottom
AlxOy/AlGaAs distributed Bragg reflector (DBR), an AlxOy spacer layer
, and a top AlxOy/AlGaAs DBR is prepared by a wet-oxidation process. T
he measured resonance linewidth agrees well with that of calculation,
indicating very small overall losses in the cavity. The wet-oxidation
process does not seem to degrade the interface of the epitaxial layers
significantly. The lower bound of maximum achievable reflectivity fro
m the AlxOy DBR is estimated to be >99.95%, assuming an average interf
ace roughness of about 0.6 nm. The maximum achievable finesse of this
type of cavity is expected to be larger than that of the all-epitaxial
counterpart assuming the same roughness. (C) 1998 American Institute
of Physics.