An optical well is configured to receive a test sample for examining an optical characteristic of the sample at a first wavelength in a predetermined wavelength range. The optical well includes a wall having a bottom wall portion and a sidewall portion defining a chamber for receiving the test sample, and an optical film formed into a shape so that a portion of the sidewall portion includes a first portion of the optical film, and a portion of the bottom wall portion includes a second portion of the optical film. For a normally incident light, the microlayers in each of the first and second portions have an average optical reflectance of greater than about 80% in the predetermined wavelength range. The forming results in the plurality of microlayers of the integral formed optical film having a thinnest portion and a thickest portion having a thickness difference of at least 30%.