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We experimentally and theoretically study self-phase modulation by Kerr effect in a liquid filled hollow core photonic crystal fiber. We perform a complete characterization of the linear optical properties of the hollow core photonic bandgap fiber filled with deuterated acetone to determine all the characteristics of the propagation mode. The nonlinear coefficient of the fiber is determined by fitting the output spectra broadened by self-phase modulation with a new analytical expression giving the spectra of a hyperbolic secant pulse transmitted through a Kerr medium. The experiment allows a precise determination of the nonlinear index change nI2 of acetone-d6 equal to (1.15±0.17)×10−19 m2 W−1.

A fast tunable filtering technique is proposed associating a diffraction grating with an intracavity Bragg grating. The bandwidth and the tuning range of this filter can be easily adapted by changing the diffraction grating's orientation, or its period, and its response is uniform over the whole tuning range. A numerical simulation of the filter response to a Gaussian beam has been developed, and it fits the experimental results allowing a calculation of the performances that could be obtained with more specific elements. For example, using a commercial acousto-optic deflector would allow a separation of 500 frequencies. It would then be possible to have a tuning range of 100 nm with a bandwidth of 0.2 nm for optical telecommunications.

Two-dimensional photonic crystals composed of two orthogonal volume diffraction gratings have been photogenerated in photopolymers. When the read beam is set at the Bragg angle, the diffraction efficiency of the transmission grating is strongly enhanced at the band edge of the reflection grating recorded in the material. Such a device provides Bragg operation and enhancement of the diffraction efficiency of the thin diffraction grating together with good wavelength selectivity. Such advantages could be interesting for optical signal processing.

International audience; The diffraction of Gaussian beams on intracavity Bragg gratings is analyzed theoretically. For reasonable waists the associated beam divergence does not significantly influence the diffraction efficiency of such devices. Nevertheless, the tilt angle of the incident beam, imposed by the Bragg resonance condition, strongly reduces the diffraction efficiency at short grating periods. However, the angular selectivity can be maintained if the Fabry-Perot cavity is tuned to the incident beam direction, which allows the use of small-volume holograms together with a dense angular multiplex. This theoretical analysis can be applied to the optimization of the diffraction properties of Gaussian beams on any intracavity Bragg grating, which could then be used for freespace parallel signal processing.

The diffraction efficiency of gratings photoinduced in semiconductor-doped glasses by interfering pump beams is used to demonstrate that refractive-index changes occur during the photodarkening process in such media. The refractive-index modifications are due to the static Kerr effect following the creation of a space-charge electric field that is photoinduced in the semiconductor nanocrystallites. This electric field, which is created by the trapping of one electron in the host glass matrix and one hole in the nanocrystallite, is in fact annihilated if a second electron–hole pair is created in the dot, making the space-charge field and photodarkening effects quite different for writing gratings. A simple theory based on these ideas is in good agreement with the experimental results. Moreover, the present measured low diffraction efficiencies (a few 10−4) could probably be greatly increased if a high static electric field were applied to the glass sample during the grating writing process, thus perhaps making semiconductor-doped media attractive for the purpose of recording permanent holograms.

Nonlinear Faraday processes in diluted magnetic semiconductors are theoretically and experimentally investigated through the analysis of the modifications of the intensity, the polarization direction, and the phase of a high-intensity arbitrarily polarized laser beam. Calculations demonstrate that the nonlinear Faraday processes are decoupled from Kerr effects when the propagation wave vector is in the (1, 1, 1) direction with respect to the crystal axes. Experiments performed in such a configuration in Cd0.75Mn0.25Te confirm this analysis and show photoinduced polarization rotations and phase changes proportional to the magnetic field that saturate when the laser intensity is increased beyond a certain value. The large nonlinear susceptibilities derived for the material show that the nonlinear Faraday processes could overcome two-photon absorption and Kerr effects for magnetic fields of the order of a few tesla.

Experiments using intracavity nearly degenerate four-wave mixing in GaAlAs semiconductor laser oscillators and resonant-type amplifiers suggest that the resonance-relaxation process can be simply interpreted in terms of the dynamic Stark effect for a two-level system. This new interpretation is confirmed by a theoretical development demonstrating that lasers and resonant-type amplifiers can actually be represented well by an equivalent two-level system that takes into account both the semiconductor medium and cavity constants. Such an analysis can be useful for the study of higher-order instabilities.

On-axis intracavity nearly degenerate four-wave mixing performed inside a laser composed of inverted two-level systems is studied theoretically using analytical solutions for the propagation equations obtained in the case in which the undepleted pump laser is operating near threshold. Reflectivities up to 103–106 are predicted, together with bandwidths that make such a setup usable for practical applications. The influence of the ac Stark effect and cavity mistuning on the reflectivity is also considered.

High-efficiency pulse compression has been obtained by using an intracavity Raman oscillator. The energy of a primary laser stored in its high-Q cavity is extracted at the Stokes frequency by means of a Stokes laser having a high Raman gain and a low-Q cavity. This technique, using hydrogen gas as the Raman medium, permits shortening of the pulse duration of a ruby laser by a factor of 6.7 with 87% effective quantum efficiency. It would be especially useful with low-gain (alexandrite) and with short-storage-lifetime lasers.