D. Josse

Near‐infrared optical parametric oscillation in a N‐(4‐nitrophenyl)‐L‐prolinol molecular crystal

Optical parametric oscillation has been achieved in a 1.9‐mm‐thick organic nonlinear optical crystal of NPP [N‐(4‐nitrophenyl)‐L‐prolinol]. Tunability from 0.9 to 1.7 μm is obtained for the first time in an organic crystal with a maximum total conversion efficiency of about 5%. Considerable possibilities for further optimization are available.

Polymer microring lasers with longitudinal optical pumping

We propose an optical pumping scheme for microring cavity lasers. The pump beam is end-fire coupled into the optical fiber that supports the microring cavity. When propagating along the fiber, the pump light is coupled into and excites the gain medium in the microring. We have demonstrated that this pumping geometry leads to an enhanced slope efficiency and significant reduction of the lasing threshold. In addition, as the excitation of the gain medium is uniform, certain effects that are prone to occur in the usual transversal pumping configuration because of nonuniform excitation can be avoided.

Matching molecular and optical multipoles in photoisomerizable nonlinear systems

We experimentally investigate the coupling rules between molecules and optical fields in the all-optical poling scheme. The efficiency and symmetry of the photoinduced quadratic nonlinearity is shown to be dependent on tensorial selection rules connecting the symmetries of the optical poling fields and the molecular tensors. We show that an optimal poling is obtained by matching the molecular symmetry to either a quasi-dipolar or a purely octupolar poling field, each being engineered by use of circular polarizations. Moreover, we define optimized poling conditions allowing the direct measurement of molecular nonlinear anisotropies. This research can be applied to nonlinear and photoisomerizable multipolar molecular systems.

Polymer-based microcavity with photoencoded quadratic nonlinearity.

Functional electro-optic polymer thin films embedded in microcavity structures have been poled by an all-optical procedure based on the interference of multiphoton absorption processes. The photoinduced X((2)) tensor was then further addressed at modal resonance for the fundamental wavelength, leading to significant enhancement of the second-harmonic-generation efficiency. An order-of-magnitude enhancement, which is due to electric field resonant conditions inside the microcavity, has been probed by an optical parametric oscillator, in comparison with a single-path thin-film configuration. This configuration opens new perspectives in the realm of nonlinear photonic device processing.

Enhanced photoinduced birefringence in polymer microcavities

We investigate photoinduced birefringence in functionalized polymer microcavities illuminated by a visible polarized cw laser beam. The cavity studied in this experiment consists of an assembly of two Bragg mirrors embedding a polymer film with tethered azobenzene dyes. Linearly polarized light induces orientationally selective excitation of the chromophore guests, resulting in optical anisotropy of the film. The mechanism of the phenomenon is based on random-to-axial statistical reorientation of the azochromophores following repetitive trans-cis-trans photoisomerization cycles. The resulting birefringence is inferred from analysis of the spectral shifts of the cavity Fabry–Perot longitudinal modes as a result of illumination. A large value of the birefringence of the order of 10−2 is noted after currently unoptimized durations of the order of 30′ in the 1.3–1.5 μm range with possible applications in optical storage at WDM telecom-compatible wavelengths.

Progress in erasable and permanent polymer based DFB-structures with multicolour tunable laser emission

Highly luminescent organic solid state media including molecular dye doped guest-host systems and novel conjugated polymers currently attract a lot of interest for application in photonic technology. We demonstrate organic solid-state lasers with broadly and continuously tuneable mode emission (Δλ = 40nm, FWHM < 1nm). Feed-back onto polymeric DFB-structures results from dynamic and permanent photoinduced in-plane gratings. A write and read - technique for easy and low cost fabrication of single and multiple grating devices is presented. The combination and optimization of tuneable gratings with specific confinement features as from different waveguiding formats open-up new approaches in integrated optics.

Towards non-linear photonics in all-optically poled polymer microcavities

Abstract Optical poling is currently emerging as a powerful all-optical procedure for imparting non-centrosymmetry and moreover multipolar non-linear order to a functionalized polymer medium. Interference of mutually coherent fundamental and harmonic beams with adequate polarizations leads to permanent statistical multipolar ordering of the medium breaking centrosymmetry. Selective angular hole-burning within an initially isotropic distribution of molecules and subsequent molecular reorientation allow for a permanent imprint of the quadratic non-linear optical tensor associated to a controllable orientational pattern. We provide evidence of this process, for the first time to our knowledge, in a high-finesse microcavity configuration whereby all-optical dye orientation is achieved in the active layer of the microcavity. Microcavities embedding optically poled films are shown to exhibit enhanced second harmonic generation (SHG) due to the longitudinal electric field modal resonance inside the microcavity as compared to the significantly lower efficiency of plain films in the absence of cavity. This demonstration opens a new route towards promising applications in the realm of polymer-based non-linear photonics.