Tag free bio sensing micro strip

A filter assembly removably connectable to an optical assembly which forms a portion of a laser resonating cavity of a laser system, the laser resonating cavity having a gain medium, the filter assembly forming a portion of the laser resonating cavity when the filter assembly is attached to the optical assembly and positioned such that light propagating in the laser resonating cavity is incident on the filter assembly, the filter assembly comprising:

• an array comprising at least one site having as assay;
• and
• an optical structure comprising
• an overlay layer comprising a first surface of the optical structure and including a first surface and a second surface, the first surface having the array disposed thereon, and
• at least one partially reflective film layer comprising a second surface of the optical structure, said at least one partially reflective film layer disposed such that said overlay layer is between said array and said at least one partially reflective film layer,
• wherein the filter assembly is configured such that a reaction that occurs in the assay changes the refractive index of the optical structure thereby changing an optical characteristic of light propagating in the laser resonating cavity and incident on the filter assembly.