An optical resonator is characterized that employs both ultrahigh-reflective coated surfaces and total internal reflection to enable cavity ringdown spectroscopy of surfaces, films, and liquids. The monolithic folded design possesses a polarization-independent finesse that allows polarization-dependent phenomena, such as molecular orientation, to be probed. Although a restricted bandwidth (~15% of the design wavelength) results from use of reflective coatings, the resonator provides high sensitivity and facile operation. A minimum detectable absorption of 2.2 x 10(-6) was obtained for single laser shots by use of multimode excitation at 530 nm with an excimer-pumped, pulsed dye laser.