for high utilization ratio full-screen information displays. [5][6][7][8][9][10][11][12][13][14][15] Under-screen optical fingerprint recognition (UDS-OFPR) is now a dominant technology in mobile displays, [16][17][18][19] in which the display panels are simultaneously used as light sources to shine fingers pressed on the cover glass, and the cameras are embedded beneath them to capture the fingerprint images. However, UDS-OFPR often suffers from significant dampening of the reflected signal by display panels. Arising from the weakness of the signal itself, issues including low signal-to-noise ratio and contamination vulnerability must be addressed, especially the excessive deterioration of images when the polarization direction of the reflective light is altered by protective screen films. Since the launch of the mobile terminal with organic light emitting diodes (OLED) displays, [20] numerous efforts have been made to improve the performance of UDS-OFPR, including inserting a fiber collimation layer, [21] adding a micro-lens array, and leveraging optical waveguides. [22,23] Regrettably, these technologies are insufficient to address the dampening issue caused by the rotation of reflective light polarization. Recently, to realize UDS-OFPR in liquid crystal displays, it was proposed to set extra infrared light sources in the backlight to improve the reflected fingerprint images. [24,25] However, because of the free space optical construction, the thickness of the device has to be substantially increased to fully light the sensing zone, which lowers its viability in mobile displays.In this work, we propose and demonstrate an optical waveguided fingerprint recognition system embedded with twostage dual-function gratings (TSG). In working, the gratings of the first stage couple and split the under-screen incident laser beam into two waveguiding beams. Then the gratings of the second stage are used to expand and direct the two waveguiding beams to the sensing zone. At last, the fingerprint images are captured by a camera under the display screen when a finger is pressed on the optical waveguide film. With this construction, the intensity and contrast of the image signals are significantly enhanced compared to previous free-space solutions, and its slimness, transparency, large sensing area, and replaceability indicate that it is ready for application.