Nonlinear refractive-index and two photon-absorption near half the band gap in AlGaAs

Villeneuve, A.; Yang, C. C.; Stegeman, George I.; Lin, Chih Hong; Lin, Hao‐Hsiung

doi:10.1063/1.109320

Cited by 90 publications

(40 citation statements)

References 10 publications

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“…(Al doping is usually employed to decrease nonlinear losses near resonance [61].) Although this has both χ (2) and χ (3) effects, we can selectively enhance one or the other by choosing the cavity to have resonances at either the second or third harmonic.…”

Section: Resultsmentioning

confidence: 99%

?^(2) and ?^(3) harmonic generation at a critical power in inhomogeneous doubly resonant cavities

Rodríguez¹,

Soljačić²,

et al. 2007

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We derive general conditions for 100% frequency conversion in any doubly resonant nonlinear cavity, for both second-and third-harmonic generation via χ (2) and χ (3) nonlinearities. We find that conversion efficiency is optimized for a certain "critical" power depending on the cavity parameters, and assuming reasonable parameters we predict 100% conversion using milliwatts of power or less. These results follow from a semi-analytical coupled-mode theory framework which is generalized from previous work to include both χ (2) and χ (3) media as well as inhomogeneous (fully vectorial) cavities, analyzed in the high-efficiency limit where down-conversion processes lead to a maximum efficiency at the critical power, and which is verified by direct finite-difference time-domain (FDTD) simulations of the nonlinear Maxwell equations. Explicit formulas for the nonlinear coupling coefficients are derived in terms of the linear cavity eigenmodes, which can be used to design and evaluate cavities in arbitrary geometries.

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Section: Resultsmentioning

confidence: 99%

?^(2) and ?^(3) harmonic generation at a critical power in inhomogeneous doubly resonant cavities

Rodríguez¹,

Soljačić²,

et al. 2007

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“…This value is significantly better than that of Si ͑0.37͒, GaAs ͑0.10͒, and even Al 0.18 Ga 0.84 As ͑3.3͒ at 1540 nm. 17,18 As the n 2 values pertain to dilute dispersions of Q-PbSe, they scale linearly with the quantum dot concentration as demonstrated in the inset of Fig. 2͑d͒.…”

Section: Samplementioning

confidence: 92%

Spectroscopy of the nonlinear refractive index of colloidal PbSe nanocrystals

Moreels

Hens

Kockaert

et al. 2006

Applied Physics Letters

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A spectroscopic study of the optical nonlinearity of PbSe colloidal solutions was performed with the Z-scan technique at wavelength intervals of 1200-1350 and 1540-1750 nm. While nonlinear absorption remains below the detection threshold, the third order nonlinear refractive index n 2 shows clear resonances, somewhat blueshifted relative to the exciton transitions in the absorbance spectrum. The occurrence of thermal effects is ruled out by time-resolved measurements. At 1.55 m, measured ͑resonant͒ n 2 values exceed typical bulk semiconductor values by two orders of magnitude. At high optical intensity, the refractive index change saturates, indicating that statefilling lies at the origin of the observed effect. © 2006 American Institute of Physics. ͓DOI: 10.1063/1.2385658͔Inorganic nanocrystals make up a new class of materials since, unlike bulk materials, their optical and electronic properties can be effectively engineered by choosing the appropriate material and size of the particles. Over the last 15 years, colloid chemistry techniques have been developed that enable the synthesis of inorganic nanocrystals as highly monodisperse colloidal dispersions, offering great flexibility and easy processing. Applications of colloidal semiconductor nanocrystals ͑or quantum dots͒ have already been explored in optoelectronic or photovoltaic devices ͑photodetectors, 1 light emitting diodes, 2 and lasers 3 ͒. An additional field of applications may follow from recent studies indicating that quantum dots show strongly enhanced nonlinear optical properties, 4 and behave as saturable absorbers. 5,6 Materials with a large and fast nonlinear refractive index can be used in devices such as Mach-Zehnder interferometers, 7 and absorption saturation is a necessary element in passive modelocked lasers. 8 Unfortunately, most studies on the nonlinear optical properties of colloidal nanocrystals are performed either at energies well below the first one-photon transition ͑also referred to as the band gap͒ 4,5 or when performed around the band gap, yield results cloaked by thermal effects. 9,10 In this letter, we present the results of a very detailed study on the nonlinear refractive index n 2 of colloidal PbSe quantum dots ͑Q-PbSe͒ in the near-infrared wavelength region of 1200-1750 nm. Using Q-PbSe sizes varying between 3.9 and 5.8 nm, we measured n 2 as a function of wavelength and optical intensity I 0 . Covering a spectral range from the transparency region to the second exciton transition, we observed a strong enhancement of n 2 , correlated with the exciton transitions in the absorbance spectrum. Maximal n 2 values corresponded to −3 to − 410 −11 cm 2 /W for 1 M suspensions. We observed a saturation of the refractive index ␦n = n 2 I 0 only at optical intensities well above the single exciton saturation intensity. This may indicate that the nonlinear refraction is largely due to biexciton creation.State-of-the-art wet chemical synthesis is currently capable of yielding Q-PbSe particle dispersions with sizes varying from approxim...

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“…Around the telecom wavelength of λ = 1.55µm, they have a nonlinear figure of merit value of [3,4] F OM AlGaAs ≈ 5.38…”

Section: Semiconductor Kerr-nonlinear Systemsmentioning

confidence: 99%

Effect of loss mechanisms on Kerr-nonlinear resonator behaviour

Priem

Dumon

Bienstman

et al. 2005

Integrated Photonics Research and Applications/Nanophotonics for Information Systems

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Nonlinear refractive-index and two photon-absorption near half the band gap in AlGaAs

Cited by 90 publications

References 10 publications

?^(2) and ?^(3) harmonic generation at a critical power in inhomogeneous doubly resonant cavities

?^(2) and ?^(3) harmonic generation at a critical power in inhomogeneous doubly resonant cavities

Spectroscopy of the nonlinear refractive index of colloidal PbSe nanocrystals

Effect of loss mechanisms on Kerr-nonlinear resonator behaviour

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