Fig. 1. Schematic diagram of TPA effect

Fig. 2. Photocurrent detection system of Ge-on-SOI photodetector in 2 μm wavelength band based on TPA effect

Fig. 3. The optical spectrum of 2 μm wavelength band laser

Fig. 4. Optical microscope images

Fig. 5. Relationship curve between input optical power and TPA photocurrent of the Ge-on-SOI photodetector