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Home page > Research Areas > Secure Networks > Nonlinear Optics for Quantum Communications

Nonlinear Optics for Quantum Communications

Coordinator : Paul Voss
Post-doc : David Chapron

Context and Objective

Objective : New coherent optical photon sources for applications in optical quantum communications.

Light sources used in quantum cryptography and quantum calculations are currently limited by the use of single photon (linear optic) or by the use of double photons created in non-linear crystal by a second order process. A photon source using the inverse process of third harmonic generation, a third order parametric amplifier, will permit the production of triply correlated photons. Because of the weakness of $\chi$ ⁽³⁾ this should be performed in a waveguide.

To accomplish this objective, new optical devices are required :

phase matching of pure third order $\chi$ ⁽³⁾ process
large bandwidth
some manufacturing tolerances.

The non-linear optics research team is designing and constructing such devices.

Research themes

1. Design of third harmonic generation devices ____

Pure third harmonic generation efficiency is currently around 2% for low rate regenerating amplified pulses in bulk crystal. To obtain this result, high optical power and low repetition rate are needed to generate a third harmonic wave in the non-linear crystal, but without phase-matching. In contrast, our approach is based on the use of waveguides to obtain an effective third harmonic generation process at a high rate to confine the electrical field (Fig.1).

Fig 1. Exemple de guide d'onde

Fig 1. Waveguide example. (a) Waveguide structure composed of one core surrounded by two materials (M1,M2) in order to confine the generated wave at 3 $\omega$ . (b) Calculation results which show the mode profile at 3 $\omega$ in the waveguide.

2. Experimental research : pure third harmonic generation in waveguides ____

The experimental setup for third harmonic generation is composed of a Coherent femtosecond Ti-Saphir laser (Verdi V10 (10W, 76MHz) + Mira 900F) followed by an OPO (Fig. 2).

Fig 2. Montage expérimental

Fig 2. Experimental setup Ti:Saphir femtoseconde laser + OPO

This setup can generate femtosecond pulses with a large bandwidth of the output signal wavelength from near-IR to near-UV (Fig. 3).

Fig 3. Longueurs d'onde disponibles en sortie de l'OPO

Fig 3. Available signal wavelengths at the OPO output [700nm, 3µm]

Keywords

optics

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