Robert Frey

Stimulated Raman scattering in an ethanol core microstructured optical fiber

We show that high efficiency stimulated Raman scattering can be obtained using hollow core photonic crystal fiber with the core filled with a low refractive index nonlinear liquid. This new architecture opens new perspectives in the development of nonlinear functions as any kind of nonlinear liquid media can now be used to implement them, with original properties not accessible with silica core fibers.

Efficient single-mode Brillouin fiber laser for low-noise optical carrier reduction of microwave signals

We experimentally demonstrate efficient optical carrier reduction of microwave signals with a single-mode 1.5-microm wavelength Brillouin all-fiber ring laser. Because of the tunable optical coupling, the lasing threshold of the short-length (20-m) fiber cavity is lower than 5 mW, and high conversion efficiencies (up to 60%) are obtained at any pump power up to approximately 200 mW. Using the single-mode Stokes beam as a seed for the stimulated Brillouin scattering process allows up to 40-dB optical carrier depletion with almost no added noise for an optically carried microwave signal at 6 GHz. In addition, using this resonator, we provide evidence of generation of high-spectral-purity beatnotes.

Light localization induced enhancement of third order nonlinearities in a GaAs photonic crystal waveguide

Nonlinear propagation experiments in GaAs photonic crystal waveguides (PCW) were performed, which exhibit a large enhancement of third order nonlinearities, due to light propagation in a slow mode regime, such as two-photon absorption (TPA), optical Kerr effect and refractive index changes due to free-carriers generated by TPA. A theoretical model has been established that shows a very good quantitative agreement with experimental data and demonstrates the important role that the group velocity plays. These observations give a strong insight into the use of PCWs for optical switching devices.

Time‐resolved direct observation of Auger recombination in semiconductor‐doped glasses

Using time‐resolved techniques, absorption recovery, and degenerate four‐wave mixing, we directly observe the nonexponential intensity‐dependent recombination of free carriers photoexcited in semiconductor‐doped glasses. We assign this behavior to Auger recombination.

Intracavity nearly degenerate four‐wave mixing in a (GaAl)As semiconductor laser

Intracavity nearly degenerate four‐wave mixing has been demonstrated by injecting a low intensity probe beam of frequency ω−δω inside a (GaAl)As semiconductor laser operating above threshold at the pump frequency ω. Conjugated reflectivities as high as 5000 together with a 25% energy conversion efficiency are reported with only a few milliwatt pump power. Additional peaks related to the ac stark effect have been observed at a detuning which depended on the pump power. This process could be useful for the study of instabilities occurring in lasers as well as for optical amplification in laser diodes.

Cavity‐enhanced highly nondegenerate four‐wave mixing in GaAlAs semiconductor lasers

Highly nondegenerate four‐wave mixing (δω>100 GHz) has been observed in GaAlAs semiconductor lasers in the case where each of the pump, probe, and conjugate frequencies is close to that of a cavity mode. The high measured reflectivities (∼1000) have been demonstrated to depend on the relative position of the pump and probe cavity resonances. When the probe frequency was tuned, probe and conjugate spectra exhibited resonances on the cavity modes lying near the probe and conjugate frequencies. Such experiments may greatly help both in the modeling of laser action and in the measurement of laser parameters.

High-efficiency single-mode Raman generation in a liquid-filled photonic bandgap fiber

Single-spatial-mode Raman generation in an ethanol-filled photonic bandgap fiber is demonstrated. Due to the limited bandwidth of the fiber, the generation is limited to the first Stokes order only, allowing high generated power without any visible decrease of the conversion efficiency. The realization of these two key properties opens the way to the realization of optimized compact nonlinear wavelength converters that will accommodate a large variety of usable liquids.

Kerr and four-wave mixing spectroscopy at the band edge of one-dimensional photonic crystals

Kerr and four-wave mixing spectroscopy is shown to be a powerful technique to quantify the strong enhancement of the third-order optical nonlinear susceptibilities at the band edge of photonic crystals. Local field factors of about 5 are demonstrated for crossed Kerr effect and a narrow resonance peak observed for the conjugate reflectivity. Moreover, a reduction of the effective nonlinear susceptibility of the four-wave mixing process with increasing pump intensities is measured, which is due to different Kerr-induced blueshifts of the band edge for forward and backward pump beams and signal and conjugate beams. This observation definitely demonstrates the need for considering all the nonlinear processes for the optimization of nonlinear photonic crystals for a given application in optical signal processing.

Tunable far-infrared Raman generation

Abstract Tunable resonance enhanced far-infrared stimulated Raman scattering was observed in 60–160 μm range for the Q( J ) transitions in hydrogen chloride. The tuning range was about 2.3 cm -1 around each studied transition ( J = 2 to 7) and the photon efficiency was measured to be of the order of 12% giving peak power around 80 kW.

Transfer-matrix modeling of four-wave mixing at the band edge of a one-dimensional photonic crystal

We present a modeling of a degenerate four-wave-mixing nonlinear process in one-dimensional photonic crystals. The model is based on the nonlinear extension of the transfer-matrix description of propagation in the structure. The influence of light localization, near the band edge of the structure, on the enhancement of the phase-conjugate reflectivity is studied. The phase-conjugate reflectivity is shown to increase as the eighth power of the number of layers with an additional large dependence on the index contrast of the structure. In both cases the enhancement is accompanied by a strong reduction of the resonance width, which may lead to some limitation of the enhancement when ultrashort pulses are used. A strong influence of the losses on the nonlinear efficiency of the structure is also predicted with a great importance of scattering losses at the multiple interfaces of the structure.