Abstract
We report a detailed study of the noise properties of a visible-to-telecom photon frequency converter based on difference frequency generation (DFG). The device converts 580 nm photons to 1541 nm using a strong pump laser at 930 nm, in a periodically poled lithium niobate ridge waveguide. The converter reaches a maximum device efficiency of 46 % (internal efficiency of 67%) at a pump power of 250 mW. The noise produced by the pump laser is investigated in detail by recording the noise spectra both in the telecom and visible regimes and measuring the power dependence of the noise rates. The noise spectrum in the telecom is very broadband, as expected from previous work on similar DFG converters. However, we also observe several narrow dips in the telecom spectrum, with corresponding peaks appearing in the 580 nm noise spectrum. These features are explained by sum frequency generation of the telecom noise at wavelengths given by the phase-matching condition of different spatial modes in the waveguide. The proposed noise model is in good agreement with all the measured data, including the power dependence of the noise rates, both in the visible and telecom regimes. These results are applicable to the class of DFG converters where the pump laser wavelength is in between the input and target wavelength.
Highlights
Quantum frequency conversion (QFC) from the visible domain to the telecommunication bands plays an important role in the development of fiber-based quantum networks
We report a detailed study of the noise properties of a visible-to-telecom photon frequency converter based on difference frequency generation (DFG)
The sum frequency generation (SFG) signal was detected with a free-space linear photodiode placed after the dichroic mirrors (DMs) that spectrally seperated the beams after the waveguide, see Fig. 1(b)
Summary
Quantum frequency conversion (QFC) from the visible domain to the telecommunication (telecom) bands plays an important role in the development of fiber-based quantum networks This is because several matter systems that are currently under development as quantum nodes emit photons in the visible domain, while optical fibers have minimum losses in the telecom bands. A convenient technique for achieving QFC of these wavelengths into the telecom bands is to use a single-stage difference frequency generation (DFG) process in a non-linear χ(2) medium This requires a strong pump laser at 1/λpump = 1/λvis − 1/λtele where λvis is the wavelength of the visible photon to be converted and λtele is the target wavelength in a telecom band.
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