Resonant metallic nanostructure for enhanced two-photon absorption in a thin GaAs p-i-n diode

 

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 consist s in the GaAs layer, a gold sub-wavelength grating on the illuminated side, and a gold mirror on the opposite side. For TM-polarized light, the structure exhibit s 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°)

APL_2photons_Fig1.png APL_2photons_Fig2.png APL_2photons_Fig3.png

(a) Schematic of the photo-detecting device, (b) SEM image (top view), (c, left) Normalized electric field intensity map at 1.486 um, for a TM-polarized incident wave at normal incidence, (c-right) average field intensity along a period

(a) Incident power delivered by the OPO source vs wavelength. (b) Measured photocurrent vs wavelength. A significant increase appears around 1.468 um due to the Fabry-Perot resonance. (c) Quadratic dependence of photocurrent with incident power.

Calculated TPA gain factor vs wavelength for a TM polarized wave at normal incidence for two set s of gratings parameters. Inset: gain factor vs incidence angle

Contact : Jean-Luc Pelouard (jean-luc.pelouard@lpn.cnrs.fr)

Further reading : B. Portier et al. Appl. Phys. Lett. 105 011108 (2014)