Pascal Baldi

High-performance guided-wave asynchronous heralded single-photon source

We report on a guided-wave asynchronous heralded single-photon source based on the creation of nondegenerate photon pairs by spontaneous parametric downconversion in a periodically poled lithium niobate wave-guide. We show that, by use of the signal photon at 1310 nm as a trigger, a gated detection process permits announcement of the arrival of single photons at 1550 nm at the output of a single-mode optical fiber with a high probability of 0.37. At the same time the multiphoton emission probability is reduced by a factor of 10 compared with Poissonian light sources. Furthermore, the model we have developed to calculate those figures of merit is shown to be accurate. This study can therefore serve as a paradigm for the conception of new quantum communication and computation networks.

Control of proton exchange for LiTaO 3 waveguides and the crystal structure of HxLi 1− xTaO 3

We show how the phase diagram of the HxLi1−xTaO3 waveguiding layer on top of a crystal of a given orientation allows one to understand, and thus to control, the proton-exchange process in lithium tantalate. Different ways of producing high-quality waveguides are identified.

Intensity dependent mode competition in second harmonic generation in multimode waveguides

Second harmonic generation (SHG) in waveguides which are multimode at the second harmonic exhibit an intensity dependence in both the phase‐match wavelength and relative conversion efficiency of the different SHG modes because they are coupled to the same fundamental.

Parametric fluorescence in periodically poled LiNbO3 buried waveguides

We report on the periodic poling of LiNbO3 buried waveguides fabricated by reverse proton exchange. We evaluate their linear and nonlinear quadratic properties with the aid of parametric fluorescence.

Loss mechanisms and hybrid modes in high-δne proton-exchanged planar waveguides

We present the influence of temperature and melt acidity on the crystalline and optical quality of high-δn proton-exchanged waveguides fabricated in LiNbO3. Correlation with Rutherford backscattering and double-crystal x-ray diffraction experiments gives a physical basis for the choice of fabrication parameters that permit the realization of high-δne, low-loss planar waveguides. We pay special interest to the influence of strain-induced biaxiality in the guiding exchanged layers.

Efficient second harmonic generation in low-loss planar GaN waveguides

We demonstrate low-loss GaN/AlGaN planar waveguides grown by molecular beam epitaxy on sapphire substrates. By using a proper AlGaN cladding layer and reducing surface roughness we reach <1dB/cm propagation losses at 633nm. These low propagation losses allow an efficient second harmonic generation using modal phase matching between a TM0 pump at 1260nm and a TM2 second harmonic at 630nm. A maximal power conversion of 2% is realized with an efficiency of 0.15%·W-1cm-2. We provide a modelling that demonstrates broadband features of GaN/AlGaN platform by showing second harmonic wavelengths tunability from the visible up to the near-infrared spectral region. We discuss drawbacks of modal phase matching and propose a novel solution which allows a drastic improvement of modal overlaps with the help of a planar polarity inversion. This new approach is compatible with low propagation losses and may allow as high as 100%·W-1cm-2 conversion efficiencies in the future.

Introduction to guided-wave quantum optics (GWQO): science, technology, and magic

In this paper we propose various applications of guided wave optics to quantum optics experiments. As quantum optics moves on to multiparticle and multiport configurations, guided wave optics, incorporating both integrated optics and fiber optics, could provide a realistic means of constructing experiments and devices.

Backward Parametric Interactions in Quasi-Phase Matched Configurations

We present numerical results on backward interactions in χ2 media using a QuasiPhase Matched configuration. Contrary to the classical forward case in which all waves propagate in the same direction, one of the generated waves propagates in the direction opposite to that of the pump. These calculations show that the contrapropagating wave generation configuration is not sensitive to a pump wavelength change over a broad range. This feature may be very useful for realizing a frequency translator. Broadband mirrorless oscillation can also be expected.

Crystallographic and Optical Properties of Z-Cut High Index Soft Proton Exchange (HISoPE) LiNbO 3 Waveguides

Highly confining nonlinear optical waveguides are extremely interesting for highly efficient and ultracompact nonlinear and/or electro-optical devices. In this paper, we concentrate on correlations between structural and optical properties of channel waveguides on z-cut lithium niobate fabricated using a new waveguide fabrication method, we call HISoPE for high index soft proton exchange, which allows obtaining a guiding layer presenting an index increase as high as 0.1 and a nonlinear coefficient equal to its value in the bulk.

Nonlinear effects in Lithium Niobate proton exchanged embedded waveguides

We present preliminary results for embedded waveguides realized on LiNbO3 by a combination of direct and reverse proton exchange. A conversion efficiency of 40%W-1cm-2 can be improved up to 160%W-1cm-2 by a correction of the waveguides imperfection.