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International audience; We investigate infrared detection at room temperature using non-degenerate two-photon absorption in a nanostructured indium phosphide photodiode. We designed the detector structure to achieve a good nonlinear absorption by combining three major ideas: first, we use the non-degenerate twophoton absorption process, which is known to be more efficient than the previously used degenerate two-photon absorption. Second, we ensured a correct spatial overlap of our pump field with our signal field. Third, we optimized the nanostructuration to increase the signal field amplitude locally within the active medium of the device. The resulting device consists of a PIN junction embedded between a back-reflecting gold mirror and a top grating. We experimentally characterized our diode with regard to reflectivity and two-photon absorption generated photocurrent for a continuouswave pump and a nanosecond pulsed signal of around 3.39 lm. Owing to the nanostructuration, the generated photocurrent shows a gain of 24 with respect to the bulk response of InP.

Degenerate two-photon absorption (TPA) is investigated in a 186 nm thick gallium arsenide (GaAs) p-i-n diode embedded in a resonant metallic nanostructure. The full device consists in the GaAs layer, a gold subwavelength grating on the illuminated side, and a gold mirror on the opposite side. For TM-polarized light, the structure exhibits a resonance close to 1.47 μm, with a confined electric field in the intrinsic region, far from the metallic interfaces. A 109 times increase in photocurrent compared to a non-resonant device is obtained experimentally, while numerical simulations suggest that both gain in TPA-photocurrent and angular dependence can be further improved. For optimized grating parameters, a maximum gain of 241 is demonstrated numerically and over incidence angle range of (−30°; +30°).

We investigate the linear response of silicon p-i-n diodes to sub-bandgap photons (1.4 μm-1.6 μm) that has been reported by many authors and left unexplored till then. The quantum efficiency of this mechanism is extremely low (typically 10−9) but has a drastic influence on silicon devices harnessing two-photon absorption. We show that this linear photonic current decreases with temperature, displaying an activation energy similar to the dark current one. We show that this behaviour is consistent with a photo-assisted Shockley-Read mechanism in which the occupancy factor of a defect state in the Si band gap is influenced by the sub-band gap photon flux.