This WP aims to the design and realization of versatile non-classical light sources based on spontaneous parametric conversion in the infrared. In particular, at telecom wavelengths, it’s possible to exploit all the technology developed for telecommunications for the realization of compact, efficient and robust experimental setups. They are suitable for transportation, and for integration in more complex apparata, to be used in sensing applications and in-field quantum communication.
Moreover, mid-infrared coherent sources will be developed and characterized, aiming to reach stability levels in frequency and emitted power, such to be used for space-level applications.
We designed and built a mid-IR optical parametric oscillator (OPO), pumped by a CW near-IR laser at 1.9 µm, with near-degenerate emission at 3.8 µm.
Multimode Sources of Non-Classical Radiation in Quadratic Resonators
We are developing a multimode source of non-classical light with continuous variables, for applications in quantum communication. In our set-up, a Nd:YAG laser at 1064.45 nm is used as a pump for a second-order nonlinear crystal, a periodically poled lithium niobate, placed inside a bow-tie cavity resonant for both the fundamental frequency and its second harmonic. The primary process of second harmonic generation of the infrared laser is followed by a cascaded internally pumped optical parametric oscillation, which generates two new frequencies around the pump frequency, called twin beams. This system has very rich dynamics, in fact it is possible, through successive cascaded three-wave interactions, to simultaneously generate two optical frequency combs, one in the infrared region and the other in the visible region around 532 nm. Limiting to the emission regime of the twin beams, we have already demonstrated up to -5 dB of noise reduction in their intensity difference below the standard quantum limit.
We are currently studying an experimental scheme to measure the degree of entanglement of the twin beams. For this purpose, in addition to the amplitude quadrature analysis performed for the intensity squeezing measurements, the experimental observation of the anticorrelation of the phase quadrature fluctuations is necessary. It will be carried out using two additional optical cavities, one for each twin beam. To achieve the required sensitivity we also designed, assembled, and tested an optical resonator to reduce the amplitude noise of the laser source in the frequency range of interest.
