Fig. 5: Operating process of the developed all-optical OTP verification token.

a Token Enrollment. The token comprises a large array of laser-printed gold-silicon microstructures. All of them are effectively divided into 25 sections, each exhibiting a unique PL signal dependent on the pump laser beam’s polarization (see Supplementary Note 9 and Supplementary Figs. 17 and 18). Consequently, the token functions as several arrays, each corresponding to a distinct laser polarization (0°, 45°, 90°, or 135° relative to the y-axis). The orange frame highlights sections forming a single microstructure. During enrollment, N PL spectra are measured from randomly selected sections and stored in our dynamic database, along with their spatial coordinates (x, y) and the corresponding laser polarization (P). This database is then transferred to a secure cloud server, and the token is issued to the user. b Token Verification. First, on request, the server provides the coordinates (x, y, P) of n points from the database. Then, the user records the corresponding spectra and sends them as a response. Next, using our ML model, the server compares the user’s spectra with the stored ones. In the event of a match, the user is verified, and the used spectra are removed from the database. Otherwise, verification fails. The whole verification process can be repeated cyclically until the database is depleted. The database size N is predetermined to accommodate a sufficient number of authentication cycles.