J.C. Loulergue

Nonlinear optical properties of (H + ,He + )- implanted planar waveguides in z-cut lithium niobate: annealing effect

Reflection second-harmonic generation from the polished waveguide end face was used to investigate the nonlinear properties of LiNbO3-implanted waveguides fabricated by use of 2-MeV He+ and 1.5-Mev ...

Second-harmonic generation in He + -implanted gadolinium calcium oxoborate planar waveguides

What is believed to be the first investigation of second-harmonic generation (SHG) in Ca(4)GdO (BO(3))(3) waveguides is reported. A planar waveguide was formed by 2-MeV-helium implantation. We cut the sample to achieve type I noncritical phase matching of an 823-nm fundamental wave for fundamental light propagating along the y axis and polarized along the z crystallophysic axis of the crystal. SHG was achieved with a relatively low pumping power of a cw Ti:sapphire laser. The results indicate that the nonlinearity of the material remains in the guiding region after ion implantation.

Formation of planar optical waveguides in the new nonlinear gadolinium calcium oxoborate, Ca(4)GdO(BO(3))(3), crystal by 2-MeV He(+) implantation.

A planar waveguide composed of the new nonlinear material, Ca(4)GdO(BO(3))(3) (GdCOB), is reported. This crystal belongs to the calcium oxoborate family. It has attractive nonlinear properties that can be of great interest in integrated optics applications. We used a method of He(+) implantation to fabricate waveguides in GdCOB crystals by creating a buried layer of lowered refractive index a few micrometers beneath the surface. Both TE and TM modes were observed. Therefore, according to the Y cut of the crystal, refractive-index values of n(x) , n(y) , and n(z) were obtained. Index profiles were reconstructed by an improved inverse WKB method. The profiles showed a steplike index behavior, indicating that the guiding region obtained was of good optical quality.

Refractive index and anisotropy measurements in He+ implanted KTiOPO4 (KTP) optical waveguides

Planar optical waveguides have been formed in Z-cut KTP materials by He+ ion implantation. Guided modess spectra and refractive index profiles nx, nxy, ny and nz are determined from dark m-lines spectroscopy and by using an IWKB method. The coupling efficiency and light confinement are better with TM (nz) modes than TE ones. This could be explained by the cristallographic axes orientation with respect to the propagation direction. The anisotropy investigation of the waveguide will end this work.

Implanted waveguides in borate crystals (LTB, β-BBO, and LBO) for frequency conversion

Abstract Helium implantation is used to produce optical waveguides in LTB, β-BBO and LBO materials. These waveguides present a step index behavior revealing a good optical quality of the guiding region with losses in the range 2–5 dB cm−1. The annealing process at 200°C during 2–24 h showed a good stability of the guiding region with a slight decrease of the optical losses. Preliminary results of SHG in LBO:He+ waveguides are reported.

Effective nonlinear coefficients of organic powders measured by second-harmonic generation in total reflection: numerical and experimental analysis

A second-harmonic wave generated by an evanescent wave (SHEW) is used to measure the effective nonlinear coefficient of organic materials in powder form. The SHEW signal is less sensitive than the powder method to the phase-matching conditions of the material. For this reason, the SHEW technique can be used to survey a wide variety of samples. The effective nonlinear coefficient and the refractive indices of the sample are obtained as fitting parameters. The influence of experimental conditions on the fitting process is discussed. The results obtained from our powders are compared with the nonlinear coefficients of the same materials in bulk crystal form. Good agreement is found between experimental results and literature values.

Waveguiding properties of pulsed-laser deposition Ca4GdO(BO3)3 thin films

Abstract Waveguiding properties of stoichiometric Ca4GdO(BO3)3 (GdCOB) thin films deposited on quartz substrates by the pulsed-laser deposition (PLD) technique are reported. The optical properties and the anisotropy of the obtained thin films are investigated using the prism-coupling technique. Refractive indices (nx=1.666, ny=1.673 and nz=1.680 at 632.8 nm) were, respectively, determined from the transverse electric (TE) and the transverse magnetic (TM) mode excitations. These values are found to be 3% lower than those of the bulk material, which is likely due to the structural and morphological features of the deposited GdCOB films.

Frequency doubling in He/sup +/-implanted periodically poled lithium niobate waveguides

Frequency doubling has been successfully performed in helium implanted planar waveguides in periodically poled lithium niobate by using quasi phase matching to generate blue laser beams.

Depth dependence of the second harmonic generation of ion implanted waveguides

Summary from only given. Second harmonic generation within optical waveguides offers the potentiality to elaborate robust, compact and reliable laser sources emitting at short wavelengths for many applications. One of the major problems encountered in producing efficient SHG devices is that the non-linear coefficients in the guiding region may undergo a degradation during the fabrication process. Light ion beam implantation has been used to form optical waveguides in many non-linear crystals. Using this technique it has been shown that the electro-optic coefficients as well as the linear optical properties of the guiding region are well preserved. A detailed characterization of the non-linear capabilities of implanted waveguides is therefore needed. We report on the investigation of the depth dependence of the second harmonic generation properties of H/sup +/ and He/sup +/ implanted LiNbO/sub 3/ waveguides, before and after thermal annealing. The measurement technique used is based on second-harmonic generation occurring during normal reflection from the polished end face of the sample.

CW blue-light second-harmonic generation from Ti:sapphire pumping in ion-implanted Ca/sub 4/GdO(BO/sub 3/)/sub 3/ (GdCOB) waveguides

Summary form only. In this paper we report on detailed studies of cw blue laser beam generation in Ca/sub 4/GdO(BO/sub 3/)/sub 3/ (GdCOB) waveguides using type I non critical phase matching. The GdCOB waveguides are produced by using a triple-energy He+-implant. In these conditions low-loss waveguides are obtained.