A Sellmeier equation for the extraordinary index of congruent lithium niobate is derived. The source data for the fit contain previously published data [Opt. Commun.17, 322 (1996); erratum20, 188 (1997); J. Appl. Phys.45, 3688 (1974)] and new measured tuning data for an optical parametric oscillator using periodically poled lithium niobate. Phase-matching predictions are accurate for temperatures between room temperature and 250 °C and wavelengths ranging from 0.4 to 5  µm.

Temperature-dependent Sellmeier equation for the index of refraction, n e , in congruent lithium niobate

Quasi-periodic structure can be introduced into nonlinear optical materials such as LiTaO3 crystals. Such structures were used for quasi–phase-matching second-harmonic generation. These materials are now shown to be able to couple second-harmonic generation and sum-frequency generation through quasi–phase-matching. The approach led to a direct third-harmonic generation with high efficiency through a coupled parametric process. The result verifies that high-order harmonics may be generated in a quadric nonlinear medium by a number of quasi–phase-matching processes, and therefore, exhibits a possible important application of quasi-periodic structure materials in nonlinear optics.

http://science.sciencemag.org/content/sci/278/5339/843.full.pdf

Quasi-phase-matched third-harmonic generation in a quasi-periodic optical superlattice

The induced nonlinear electric dipole and higher moments in an atomic system, irradiated simultaneously by two or three light waves, are calculated by quantum-mechanical perturbation theory. Terms quadratic and cubic in the field amplitudes are included. An important permutation symmetry relation for the nonlinear polarizability is derived and its frequency dependence is discussed. The nonlinear microscopic properties are related to an effective macroscopic nonlinear polarization, which may be incorporated into Maxwell's equations for an infinite, homogeneous, anisotropic, nonlinear, dielectric medium. Energy and power relationships are derived for the nonlinear dielectric which correspond to the Manley-Rowe relations in the theory of parametric amplifiers. Explicit solutions are obtained for the coupled amplitude equations, which describe the interaction between a plane light wave and its second harmonic or the interaction between three plane electromagnetic waves, which satisfy the energy relationship ${\ensuremath{\omega}}_{3}={\ensuremath{\omega}}_{1}+{\ensuremath{\omega}}_{2}$, and the approximate momentum relationship ${\mathrm{k}}_{3}={\mathrm{k}}_{1}+{\mathrm{k}}_{2}+\ensuremath{\Delta}\mathrm{k}$. Third-harmonic generation and interaction between more waves is mentioned. Applications of the theory to the dc and microwave Kerr effect, light modulation, harmonic generation, and parametric conversion are discussed.

/pdf/interactions-between-light-waves-in-a-nonlinear-dielectric-2m21ug6r84.pdf

Interactions between Light Waves in a Nonlinear Dielectric

A new kind of correlated photon-pair source based on a waveguide integrated on a periodically poled lithium niobate substrate is reported. Using a pump laser of a few /spl mu/W at 657 nm, photon-pairs are generated/degenerated at 1314 nm. Detecting /spl sim/1500 coincidences per second, a conversion rate of 10/sup -6/ pairs per pump photon can be inferred, which is four orders of magnitude higher than that obtained with previous bulk sources. These results are very promising for the realisation of sources for quantum communication and quantum metrology experiments requiring a high signal-to-noise ratio or working with more than one photon-pair at a time.

https://hal.archives-ouvertes.fr/hal-00432358/document

Highly efficient photon-pair source using periodically poled lithium niobate waveguide

In this letter, we present a source of quantum-correlated photon pairs based on parametric fluorescence in a fiber Sagnac loop. The photon pairs are generated in the 1550-nm fiber-optic communication band and detected with InGaAs-InP avalanche photodiodes operating in a gated Geiger mode. A generation rate > 10/sup 3/ pairs/s is observed, which is limited by the detection electronics at present. We also demonstrate the nonclassical nature of the photon correlations in the pairs. This source, given its spectral properties and robustness, is well suited for use in fiber-optic quantum communication and cryptography networks.

/pdf/all-fiber-photon-pair-source-for-quantum-communications-h2sbr20ji2.pdf

All-fiber photon-pair source for quantum communications

We fabricated second-order nonlinear gratings in D-shaped germanosilicate fibers, using thermal poling and periodic electrodes defined by standard photolithography. These gratings, which are up to 75??mm long, were used for efficient quasi-phase-matched frequency doubling of 1.532??m nanosecond pulses from a high-power erbium-doped fiber amplifier. Average second-harmonic powers as high as 6.8??mW and peak powers greater than 1.2??kW at 766??nm were generated, with average and peak conversion efficiencies as high as 21% and 30%, respectively.

/pdf/greater-than-20-efficient-frequency-doubling-of-1532-nm-osu67e3jsx.pdf

Greater than 20%-efficient frequency doubling of 1532-nm nanosecond pulses in quasi-phase-matched germanosilicate optical fibers.

Pulse train multiplication based on the temporal Talbot effect in a linearly-chirped fiber Bragg grating has been experimentally demonstrated. A 40GHz repetition-rate, nearly transform-limited 10ps duration optical pulse train at 1.533µm has been obtained from a 2.3GHz mode-locked Er-Yb:glass laser using a 100cm long linearly-chirped apodized fiber grating.

/pdf/40-ghz-pulse-train-generation-at-1-5-mum-with-a-chirped-2pp81sfjlq.pdf

40-GHz pulse-train generation at 1.5 mum with a chirped fiber grating as a frequency multiplier.

We report highly efficient blue-light generation by frequency doubling of a high-power cw diode-pumped 946-nm Nd:YAG laser. A periodically poled lithium niobate crystal, 6 mm long and with a period of 4.6 µm, was used in the experiment. 49 mW of blue light was generated with a conversion efficiency of 4.6%. The measured effective nonlinear coefficient (d,eff~19pm/V) and the temperature-bandwidth (Delta.T~3°C) of the crystal are close to the theoretical limits.

49 mW of cw blue light generated by first-order quasi-phase-matched frequency doubling of a diode-pumped 946-nm Nd:YAG laser.

A comparison between thermal poling of silica in air and in vacuum is reported. It is shown that the second-order susceptibility and thickness of the nonlinear layer as well as their time evolution are highly dependent on the surrounding poling atmosphere. In the vacuum case a charge distribution (under the anode) more complex and broader than that for the air case has also been revealed by laser induced pressure pulse measurements. A multiple charge carrier model can explain the formation and evolution of the depletion region under the anode. The findings are relevant to achieve improved nonlinearities in fiber and waveguide devices.

/pdf/thermal-poling-of-silica-in-air-and-under-vacuum-the-50szouhd3x.pdf

Thermal poling of silica in air and under vacuum: the influence of charge transport on second harmonic generation

We report the observation of quasiphase matched parametric fluorescence from a periodically poled silica fiber. A pair-photon production rate of more than 100 MHz around 1532 nm was achieved in second-order nonlinear gratings for 300 mW of pump power at 766 nm. These results are very promising for the realization of reliable all-fiber single-photon sources for quantum cryptography systems and metrology applications.

/pdf/parametric-fluorescence-in-periodically-poled-silica-fibers-435zzdhg6g.pdf

Valerio Pruneri

Papers

Greater than 20%-efficient frequency doubling of 1532-nm nanosecond pulses in quasi-phase-matched germanosilicate optical fibers.

40-GHz pulse-train generation at 1.5 mum with a chirped fiber grating as a frequency multiplier.

49 mW of cw blue light generated by first-order quasi-phase-matched frequency doubling of a diode-pumped 946-nm Nd:YAG laser.

Thermal poling of silica in air and under vacuum: the influence of charge transport on second harmonic generation

Parametric fluorescence in periodically poled silica fibers