Microstructural and nonlinear optical properties of silica–titania sol-gel film doped with PbS quantum dots

Thin silica–titania films doped with different concentration of PbS quantum dots (PbS/oxide molar ratios ranging from 5% to 25%) were fabricated via a sol-gel route. The structural properties were studied by x-ray diffraction, high-resolution transmission electron microscopy, and Rutherford backscattering spectrometry. The PbS crystals were found to have a mean diameter in the range 2.3–3.5 nm with narrow size distribution. The resonant nonlinear optical properties were studied by the nonlinear m-line technique and degenerate four-wave mixing. High negative nonlinear refractive indices (n2) were measured at 1.064 μm. Different n2 values were obtained for nanosecond excitation (n2=10−7–10−8 cm2/kW) and for picosecond excitation (n2=10−9–10−10 cm2/kW). The differences can be explained by saturation effects. Measurements at 532 nm showed n2 values ten times higher than at 1.064 μm. The response time of the nonlinearity for both wavelengths was below 35 ps.

[1]  K. Kubodera,et al.  Observation of optical bistability in CdS(x)Se(1-x)-doped glasses with 25-psec switching time. , 1987, Optics letters.

[2]  H. Fragnito,et al.  Light induced permanent modifications of the nonlinear optical properties of semiconductor doped glasses , 1996 .

[3]  B. G. Potter,et al.  Laser-induced darkening in semiconductor-doped glasses , 1991 .

[4]  R. C. Weast.  Handbook of chemistry and physics , 1973 .

[5]  P. Roussignol,et al.  New results on optical phase conjugation in semiconductor-doped glasses , 1987 .

[6]  K. I. Kang,et al.  Room temperature spectral hole burning and elimination of photodarkening in sol‐gel derived CdS quantum dots , 1994 .

[7]  L. Brus.  Zero-dimensional "excitons" in semiconductor clusters , 1986 .

[8]  Giancarlo C. Righini,et al.  Correlation between the structural and optical properties of polydispersed II-VI quantum dots in glass matrix , 1991 .

[9]  B. G. Potter,et al.  Quantum‐size effects on the band edge of CdTe clusters in glass , 1994 .

[10]  D Cotter,et al.  Picosecond pump-probe interferometric measurement of optical nonlinearity in semiconductor-doped fibers. , 1989, Optics letters.

[11]  R. Doremus,et al.  Handbook of glass properties , 1986 .

[12]  Brian J.J. Zelinski,et al.  Attenuation of sol-gel waveguides measured as a function of wavelength and sample age , 1994, Optics & Photonics.

[13]  D. Pohl,et al.  Laser-Induced Dynamic Gratings , 1986 .

[14]  B. D. Fabes,et al.  Laser processing of sol-gel coatings , 1992 .

[15]  V. Degiorgio,et al.  OPTICAL NONLINEARITY OF SEMICONDUCTOR-DOPED GLASSES AT FREQUENCIES BELOW THE BAND-GAP - THE ROLE OF FREE-CARRIERS , 1995 .

[16]  Donald L. Lee,et al.  Electromagnetic Principles of Integrated Optics , 1986 .

[17]  J. Puls,et al.  Determination of the anisotropic ambipolar diffusion coefficient of CdS at room temperature , 1994 .

[18]  François Hache,et al.  Time‐resolved measurements of carrier recombination in experimental semiconductor‐doped glasses: Confirmation of the role of Auger recombination , 1993 .

[19]  Yukio Osaka,et al.  Optical nonlinearity of CdSe microcrystallites in a sputtered SiO2 film , 1990 .

[20]  Richard C. Lind,et al.  Degenerate four-wave mixing in semiconductor-doped glasses , 1983 .

[21]  E. Palik.  Handbook of Optical Constants of Solids , 1997 .

[22]  R. Powell,et al.  Preparation and non-linear optical properties of CdS quantum dots in Na2O-B2O3-SiO2 glasses by the sol-gel technique , 1996 .

[23]  Ghassan E. Jabbour,et al.  PbS quantum-dot doped glasses as saturable absorbers for mode locking of a Cr:forsterite laser , 1997 .

[24]  J. Boilot,et al.  Correlation between structural and optical properties of PbS nanocrystals , 1996 .

[25]  Ying Wang,et al.  PbS in polymers. From molecules to bulk solids , 1987 .

[26]  G. R. Olbright,et al.  Interferometric measurement of the nonlinear index of refraction, n2, of CdSxSe1−x‐doped glasses , 1986 .

[27]  Takagahara.  Excitonic optical nonlinearity and exciton dynamics in semiconductor quantum dots. , 1987, Physical review. B, Condensed matter.

[28]  R. Kane,et al.  Theoretical Study of the Electronic Structure of PbS Nanoclusters , 1996 .

[29]  G. R. Olbright,et al.  Optical nonlinearities and ultrafast carrier dynamics in semiconductor doped glasses , 1988 .

[30]  J. Coutaz,et al.  Saturation of the nonlinear index of refraction in semiconductor-doped glass , 1991 .

[31]  E. Yeatman,et al.  Fabrication and characterisation of a CdS-doped silica-on-silicon planar waveguide , 1996 .

[32]  Michael Bass,et al.  Handbook of optics , 1995 .

[33]  A. Gabel,et al.  Ultrafast carrier and grating lifetimes in semiconductor‐doped glasses , 1985 .

[34]  Alessandro Martucci,et al.  Microstructural and optical properties of sol-gel silica-titania waveguides , 1997 .

[35]  W. M. Haynes.  CRC Handbook of Chemistry and Physics , 1990 .

[36]  Nicholas F. Borrelli,et al.  Quantum confinement of PbS microcrystals in glass , 1994 .

[37]  A. Martucci,et al.  Resonant nonlinear optical properties of PbS nanocrystals under nano- and picosecond pulsed laser excitation , 1997 .

[38]  S. Saltiel,et al.  Relationship between phase-conjugation efficiency and grating response time in semiconductor-doped glasses , 1989 .

[39]  D. W. Hall,et al.  Quantum confinement effects of semiconducting microcrystallites in glass , 1987 .

[40]  Lindberg,et al.  Third-order optical nonlinearities in semiconductor microstructures. , 1988, Physical review. B, Condensed matter.

[41]  D. J. Hagan,et al.  Kramers-Krönig relations in nonlinear optics , 1992 .

[42]  David A. B. Miller,et al.  Theory of the linear and nonlinear optical properties of semiconductor microcrystallites. , 1987, Physical review. B, Condensed matter.