Jean Botineau

Independent control of index and profiles in proton-exchanged lithium niobate guides

We demonstrate the possibility of controlling, practically independently, the form and indices of proton-exchanged lithium niobate guides by means of guide annealing and proton exchange in lithium-rich solutions. Experimental results are presented that indicate how one can realize specific guide designs.

Fabrication and characterization of Titanium Indiffused Proton Exchanged (TIPE) waveguides in lithium niobate

Abstract We report the fabrication and characterization of optical waveguides realized in LiNbO 3 by a combined titanium indiffusion proton exchange (TIPE) process. These guides provide several unique advantages which include permitting tailorong of guide birefringence, realizing proton exchanged Y -cut plates of good optical quality, and the realization of imbedded TM guides due to a lowering of n o caused by proton exchange.

Extension of second-harmonic phase-matching range in lithium niobate guides

An extension of the fundamental wavelength phase-matching range for second-harmonic generation based on titanium-indiffused proton-exchanged lithium niobate guides has been demonstrated. Both the theoretical basis and experimental verification are presented.

Stabilization of a stimulated Brillouin fiber ring laser by strong pump modulation

A stable train of compressed Stokes pulses (to ~10 nsec) is obtained in a stimulated Brillouin fiber ring laser (of length L = 83 m) by periodically interrupting the argon-ion cw pump beam with an intraring cavity acousto-optic modulator. Interruption of the pump action, at each round-trip time tr ≃ Ln/c, permits damping of the excited sound waves that accumulate at the entry of the fiber owing to the inertial response of the material, well described by the coherent three-wave stimulated Brillouin scattering model (C3W-SBS equations). Amplification and compression of the backscattered Stokes pulse are limited by nonlinear optical Kerr effect, which is incorporated into the C3W-SBS equations.

Absolute measurement of the 1.06 μm two-photon absorption coefficient in GaAs

Comparing the recombination light intensity produced in GaAs by a 1.06 μm pulse inducing two-photon absorption, with the intensity produced by a 0.53 μm pulse, we obtain directly the two-photon absorption cross-section. This method can be generalized to other materials.

Optical properties determination at 10.6 μm of thin semiconducting layers

An optical characterization of thin semiconducting multilayers in the infrared range, using a combination ofm-lines and reflection spectroscopy techniques is exposed. Such a method, non-destructive, allows to determine the thickness and the refractive index of each component of a multilayer multimodal planar waveguide.

Guided‐wave measurement of the 1.06‐μm two‐photon absorption coefficient in GaAs epitaxial layers

The optical perturbation of an infrared wave guided in a GaAs epitaxial layer allows us to measure the two‐photon absorption coefficient β for the wavelength λ=1.06 μm. The use of optical properties of free carriers induced by the two‐photon effect and of guided optical wave techniques strongly enhances method accuracy. The result (β=0.06 cm MW−1) is in good agreement with the most recent bulk measurements and the theoretical values.

Optical determination of free carriers parameters in an epitaxial GaAs layer

The optical perturbation of an infrared wave guided in a GaAs epitaxial layer allows to measure characteristic parameters of free carriers: collision frequency (2·1013 rad·sec−1), depth penetration of induced photopairs (∼2.5μm), relaxation times of free carriers.

Soliton compression and locking in a Brillouin fiber ring laser

ABSTRACT Stimulated Brillouin scattering (SBS) in an optical fiber cavity resonantly couples an optical cw-pump anda backscattered Stokes wave with electrostrictively excited longitudinal GHz hypersound waves. Below a crit-ical feedback the Stokes wave self-structurates into ns pulses, called Brillonin dissipative three-wave solitons; they are able in turn to electrostrictively excite lower frequency acoustic waves (f = 5 MHz to 1 GHz), dueto cladding Brillouin scattering (CBS), transversally propagating with respect to the fiber axis in the fiberscladding. We derive a four-wave model which couples the transverse CBS dynamics to the nonlinear dissipative three-wave SBS dynamics. Above a critical coupling, the resonant CBS oscillations (f/FSR = integer) arestrong enough to break the pulses, while stable compressed or decompressed pulses are still obtained in finitefrequency ranges between resonant frequencies: the small damped low frequency CBS vibrations contribute tolock further longitudinal cavity modes which compose the compressed SBS soliton. A stability map is computed.Compression up to a factor 0.4 with respect to the bare Brillouin soliton is numerically obtained, yielding nspulses of peak intensity up to 14 times the cw launched pump, in fair quantitative agreement with experimentsdone in long fiber ring cavities.Keywords : Stimulated Brillouin scattering, dissipative solitons, fiber ring lasers, pulse compression

A coherent approach to stationary stimulated Brillouin fiber amplifiers

An analytical stationary solution is proposed for the collinear Brillouin fiber mirror in the frame of the 1-D-coherent 3-wave model, in which decoupled phases allow side-resonance interaction, the conservation of the impulsion being insured by a nonlinear phase gradient. The Lorentzian shape of the gain curve of low efficiency stationary SBS amplifiers is then justified, even when the interaction is strong enough to stimulate an acoustic wave with a narrow spectral width. It is shown that, when SBS efficiency increases, the gain curve first exhibits some gain narrowing, then saturates, yielding for high pump powers a spectral band larger than the spontaneous Brillouin bandwidth.RésuméUne thé orie gé né rale de l’amplification Brillouin en régime stationnaire, est pré senté e qui tient compte à la fois de la déplétion de la pompe et d’un é ventuel dé saccord en fré quence du signal par rapport à la ré sonance. Cette é tude impose une ré interpré tation de la notion de largeur de gain Brillouin, l’amplificateur se comportant comme l’é quivalent acoustique d’un laser lorsque les ondes ré trodiffusée et maté rielle sont l’une et l’autre stimulées. On est alors en pré sence de trois ondes (pompe-Brillouin-acoustique), spectralement très é troites et donc de fré quences et de phases bien définies; en ré gime stationnaire, on peut se ramener à un système d’ é quations où les intensités sont indépendantes des phases, le dé saccord de fré quence é ventuel des trois ondes par rapport à la ré sonance é tant compensé par un gradient de phase longitudinal stationnaire. La largeur spectrale d’un amplificateur Brillouin peut ici être dé finie comme celle de la courbe de gain obtenue en faisant varier la fré quence d’un signal Stokes monochromatique autour de la résonance. Cette nouvelle dé finition n’affecte pas l’évolution de la ré ponse spectrale de l’amplificateur en fonction de la puissance. Dans la limite des gains faibles, on retrouve ainsi la lorentzienne associée à la diffusion spontanée, de même que son affinement par le gain. Puis, ce gain saturant à la résonance à une valeur correspondant à un transfert d’énergie presque total de la pompe vers l’onde Stokes, la courbe de gain recommence à s’ élargir, menant pour les très fortes puissances de pompe à une bande plus large que celle de la diffusion Brillouin spontanée.