A semiconductor ridge micro cavity to generate counterpropagating twin photons X.Caillet a , V. Berger a , G. Leo a , I. Sagnes b , S. Ducci *a a Laboratoire Matériaux et Phénomènes Quantiques, UMR 7162, Université Paris Diderot Paris 7 - CNRS, Case 7021, Paris Cedex 13, France; b Laboratoire de Photonique et Nanostructures, CNRS-UPR20, Route de Nozay, 91460 Marcoussis, France ABSTRACT A semiconductor ridge microcavity is designed to generate counterpropagating twin photons by parametric fluorescence. This device is suitable as a narrow bandwidth source of twin photons at 1.55 µm working at room temperature. A sensible efficiency improvement due to the presence of the vertical cavity is demonstrated. The degree of frequency correlation can be controlled through the pump field spatial and spectral profiles. Keywords: nonlinear guided optics, parametric down conversion, microcavity, twin photons 1. INTRODUCTION Semiconductor microcavities based on Distributed Bragg Reflectors (DBR) have been extensively studied in the past years due to their strong impact on applications and light matter interactions. Among the photonic devices based on these kind of cavities, we can cite VCSELs [1], light-emitting diodes and nonlinear optical switches. In the context of fundamental research, the strong coupling between exciton and photonic cavity mode is an intense field of study in this moment [2]. In all of these cases, light is strongly confined in one or, by additional lateral patterning, more dimensions, like in ridge microcavities (2D confinement) [3] or micropillars (3D confinement) [4]. The field enhancement induced by the cavity can also be used to increase the efficiency in three wave mixing processes such as Second Harmonic Generation (SHG) or Spontaneous Parametric Down Conversion (SPDC). In this context we can mention several works concerning a “transverse pump configuration”, where one of the interacting beams is parallel to the cavity axis and orthogonal to the other ones [5, 6]. The first experimental demonstration of this kind of interactions has been an SHG experiment with a ridge microcavity [7]. It has also been proposed to use SPDC in the transverse pump configuration, in order to realize a counter-propagating twin photon source [8], and the corresponding experimental demonstration has been reported in [9]. Several advantages arise from this geometry: automatic separation of the downconverted photons, large tunability, narrow spectral bandwidth. Thereafter we first illustrate the working principle of the source pointing out its main advantages (Section 2); then we describe the efficiency enhancement due to the integration of a vertical microcavity (Section 3) and we presents our experimental results on a Surface Emitted Second Harmonic Generation (SESHG) experiment (Section 4). Finally, in Section 5 we draw our conclusions. 2. PARAMETRIC DOWN CONVERSION WITH COUNTERPROPAGATING SIGNAL AND IDLER The twin-photon source presented here is a multilayer AlGaAs waveguide designed to allow a counter-propagating phase matching scheme. The lateral confinement is provided by a wet-etched ridge. In this geometry (Figure 1), a pump field (775 nm) impinges on top of the waveguide generating two counter-propagating, orthogonally polarized waveguided twin photons (~1550 nm) through spontaneous parametric down conversion. The frequencies of the emitted fields are fixed by the energy (ωp = ωs + ωi) and momentum (kp sinθ = nsks - niki) conservation,where ωp, ωs and ωi (kp, ks and ki) are the frequencies * sara.ducci@univ-paris-diderot.fr Invited Paper Quantum Sensing and Nanophotonic Devices VI, edited by Manijeh Razeghi, Rengarajan Sudharsanan, Gail J. Brown, Proc. of SPIE Vol. 7222, 72221J · © 2009 SPIE · CCC code: 0277-786X/09/$18 · doi: 10.1117/12.808182 Proc. of SPIE Vol. 7222 72221J-1