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Communication Dans Un Congrès Année : 2020

Optimized bi-resonant nanostructured diode for infrared photodetection through non degenerate two-photon absorption

Résumé

Two-photon absorption (TPA) is a third order non-linear process that relies on the quasi-simultaneous absorption of two photons. Therefore, it has been proved to be an interesting tool to measure ultra-fast correlations 1 or to design all-optical switches. 2 Yet, due to the intrinsically low efficiency of the non-linear processes, these applications rest upon high peak power light sources such as femtosecond and picosecond pulsed laser. However TPA has also been noticed as an appealing new scheme for quantum infrared detection. 3, 4 Indeed, typical quantum detection of IR radiation is based on small gap semiconductors that need to be cooled down to cryogenic temperature to achieve sufficient detectivity. TPA enables the absorption of IR photons by wide gap semiconductors when pump photons are provided to complete optical transitions across the gap. Still, the low efficiency of TPA represents a difficulty to detect usual infrared photon fluxes. To tackle this issue, we combined three strategies to improve the detection efficiency. First, it has been proved theoretically and experimentally that using different pump and signal photon energies, which is known as non degenerate TPA (NDTPA), help increasing the TPA efficiency by several orders of magnitude. 5 Secondly, it is well known that TPA has a quadratic dependence with the signal electric fields modulus, so we designed a specific nanostructure to enhance the signal field inside the active medium of the detector. Finally, since TPA is a local quasi-instantaneous process, both pump and signal photons must be temporarily and spatially co-localized inside the active medium. We made sure to maximize the overlap of the fields inside our device. In this proceeding, we report the concepts of nanostructures and how it influences TPA absorption in a PIN photodiode. Experimental data point out that infrared photons were detected inside our first generation of diodes. However some issues are still to deal with to reach infrared detection with low fluxes thermal sources. The SNR (signal to noise ratio) can be widely improved by reaching higher values of NDTPA photocurrent and limiting the sub-gap absorptions mainly responsible for the structure noise. Consequently a second generation of nanostructured photodiodes has been designed to perform better detection. NDTPA theory The expected photocurrent generation in a PIN junction through two-photon absorption is a sum of three terms: (1) the linear absorption current, (2) the degenerate TPA current of the pump and (3) the NDTPA-generated photocurrent : J total = α (ω p) I p + β (ω p , ω p) I 2 p + β (ω p , ω s) I p I s (1) Where I p (resp. I s) is the intensity [W/m 2 ] of the pump (resp. signal) beam, · represent the integration in the i-layer, the α is the linear absorption coefficient and β is the TPA coefficient. The first term comes from a linear absorption of sub-bandgap photons from the pump light. This phenomenon has been studied in several materials (silicium, gallium arsenide) and is explained as a photo-assisted Shockley-Read-Hall (PASRH) process. 6, 7 The second term is the degenerate two-photon absorption of the pump. 3 The last one comes from the non-degenerate
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Dates et versions

hal-02864687 , version 1 (11-06-2020)

Identifiants

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Maxence Dauphin, Baptiste Fix, Grégoire Beaudoin, Isabelle Sagnes, Julien Jaeck, et al.. Optimized bi-resonant nanostructured diode for infrared photodetection through non degenerate two-photon absorption. Quantum Sensing and Nano Electronics and Photonics XVII, Feb 2020, San Francisco, United States. pp.Proc. SPIE 11288, 112881S, ⟨10.1117/12.2545730⟩. ⟨hal-02864687⟩
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