Heavy water detection using ultra-high-Q microcavities

Ultra-high-Q optical microcavities (Q > 10(7)) provide one method for distinguishing chemically similar species. Resonators immersed in H2O have lower quality factors than those immersed in D2O due to the difference in optical absorption. This difference can be used to create a D2O detector. This effect is most noticeable at 1300 nm, where the Q(H2O) is 10(6) and the Q(D2O) is 10(7). By monitoring Q, concentrations of 0.0001% [1 part in 106 per volume] of (DO)-O-2 in H2O have been detected. This sensitivity represents an order of magnitude improvement over previous techniques. Reversible detection was also demonstrated by cyclic introduction and flushing of D2O. (c) 2006 Optical Society of America