Detectable labels, methods of manufacture and use

An encodable particle comprising:

• a glass particle doped with at least one rare earth element distributed in the particle at a concentration, a location, or both, to provide a pattern or an array of marks having a unique identification code to identify a functional group attached thereto, the functional group is selected from the group consisting of a nucleic acid, an antibody, a protein, and an enzyme,
• the rare earth element is selected from the group consisting of Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, U, and combinations thereof,
• the particle comprises a fiber having a diameter of 10 microns to 100 microns, and
• the fiber having a cross-section including an array of layers, each layer having an optical property different from an optical property of adjacent layers.