Abstract

Much recent progress has been achieved in the fabrication of single photon emitters based on color centers in diamond, e.g., silicon-vacancy (SiV) centers emitting at λ_s = 738nm [1]. However, efficient single photon transmission in future quantum networks requires wavelengths in the telecom bands around λ_o = 1310nm or λ_c = 1550nm. In order to bridge this wavelength gap we investigate frequency downconversion according to ${\lambda }_s^{-1}-{\lambda }_p^{-1}\approx {\lambda }_c^{-1}$, where λ_p denotes the wavelength of a strong pump field. We here report on work achieving a conversion efficiency that is at least 40 times higher compared to similar experiments that have used optical powers at the single photon level [2,3]. Our setup is shown in Fig. 1(a). To emulate the single photon source at λ_s an attenuated continuous wave Ti:Sapphire laser (Ti:Sa) together with a pulse picker is used. A home-built tunable continuous wave optical parametric oscillator generates the pump light at λ_p = 1403nm. The two fields are coupled into a temperature controlled ridge waveguide (WG) made of periodically poled ZnO:LiNbO₃. It is possible to excite only the fundamental WG mode at λ_s (see inset in Fig. 1(a)) which in combination with the strong confinement in the WG provides a good spatial overlap between the interacting modes. Using a spectral filtering stage (prism, pinhole, bandpass filters) one of the three beams can be selected at the waveguide output and coupled into an optical fiber for further analysis using a single photon avalanche diode (SPAD) or a grating spectrometer, respectively.

© 2011 IEEE