Coherent and collimated blue light generated by four-wave mixing in Rb vapour.

We investigate frequency up-conversion of low power cw resonant radiation in Rb vapour as a function of various experimental parameters. We present evidence that the process of four wave mixing is responsible for unidirectional blue light generation and that the phase matching conditions along a light-induced waveguide determine the direction and divergence of the blue light. Velocity-selective excitation to the 5D level via step-wise and two-photon processes results in a Doppler-free dependence on the frequency detuning of the applied laser fields from the respective dipole-allowed transitions. Possible schemes for ultraviolet generation are discussed.

[1]  R. Scholten,et al.  Blue five-level frequency-upconversion system in rubidium. , 2006, Optics letters.

[2]  T. J. Killian.  Thermionic Phenomena Caused by Vapors of Rubidium and Potassium , 1926 .

[3]  J. E. Bjorkholm,et al.  Erratum: Line shape and strength of two-photon absorption in an atomic vapor with a resonant or nearly resonant intermediate state , 1976 .

[4]  O. Heavens.  Radiative Transition Probabilities of the Lower Excited States of the Alkali Metals , 1961 .

[5]  R. Scholten,et al.  State-selective imaging of cold atoms , 2008 .

[6]  S Franke-Arnold,et al.  Enhanced frequency up-conversion in Rb vapor. , 2010, Optics express.

[7]  S. Rolston,et al.  Nondegenerate four-wave mixing in rubidium vapor: The diamond configuration , 2008 .

[8]  M. Scully,et al.  Lasers without inversion. , 1994, Science.

[9]  Leo W. Hollberg,et al.  Efficient frequency up-conversion in resonant coherent media , 2002 .

[10]  Edward S. Fry,et al.  ULTRASLOW GROUP VELOCITY AND ENHANCED NONLINEAR OPTICAL EFFECTS IN A COHERENTLY DRIVEN HOT ATOMIC GAS , 1999, quant-ph/9904031.

[11]  J. Mompart,et al.  Propagation effects on lasing without population inversion , 2000 .

[12]  A. V. Taichenachev,et al.  ACTIVE MEDIA: Optical cascade pumping of the 7P3/2 level in cesium atoms , 2005 .

[13]  J E Debs,et al.  Coherent 455 nm beam production in a cesium vapor. , 2009, Optics letters.

[14]  P. Hannaford,et al.  Highly nonlinear atomic medium with steep and sign-reversible dispersion* , 2003 .

[15]  A. Sargsyan,et al.  Doppler-free satellites of resonances of electromagnetically induced transparency and absorption on the D2 lines of alkali metals , 2006 .

[16]  Jordi Mompart,et al.  Lasing without inversion , 2000 .