Optical devices with engineered nonlinear nanocomposite materials

1. An optical device comprising:

a waveguide core including a portion formed of a nanocomposite material, said nanocomposite material including:

a matrix material; and

a plurality of quantum dots dispersed in said matrix material, a quantum dot of said plurality of quantum dots including a substantially crystalline core that includes a semiconductor material selected from the group consisting of Si and Ge, said quantum dot being substantially defect free such that said quantum dot exhibits photoluminescence with a quantum efficiency that is greater than 10 percent.

2. The optical device of claim 1 , further comprising a cladding surrounding said waveguide core.

3. The optical device of claim 1 , wherein said waveguide core includes a plurality of portions positioned at respective locations along a longitudinal axis of said waveguide core, said plurality of portions being formed of said nanocomposite material.

4. The optical device of claim 1 , wherein said waveguide core is a first waveguide core, said optical device further comprising a second waveguide core optically coupled to said first waveguide core.

5. The optical device of claim 1 , wherein said nanocomposite material has a nonlinear index of refraction γ that is at least 10 −9 cm 2 /W when irradiated with light having a wavelength λ between approximately 3×10 −5 cm and 2×10 −4 cm.

6. The optical device of claim 5 , wherein γ is at least 10 −8 cm 2 /W.

7. The optical device of claim 5 , wherein said nanocomposite material has a figure-of-merit that is at least 1, said figure-of-merit being defined as 2γ/βλ, where β is a two-photon absorption coefficient of said nanocomposite material expressed in cm/W.

8. The optical device of claim 7 , wherein said figure-of-merit is at least 1.5.

9. The optical device of claim 1 , wherein said matrix material is selected from the group consisting of polymers and glasses.

10. The optical device of claim 1 , wherein said nanocomposite material comprises more than 10 percent by weight of said plurality of quantum dots.

11. The optical device of claim 1 , wherein said nanocomposite material comprises at least 40 percent by weight of said plurality of quantum dots.

12. The optical device of claim 1 , wherein said plurality of quantum dots have a peak size between approximately 1 nm and 100 nm.

13. The optical device of claim 1 , wherein said quantum dot further includes a shell surrounding said substantially crystalline core.

14. The optical device of claim 1 , wherein said semiconductor material is Si, said shell including an oxide SiO n with n being between approximately 0 and 2.

15. The optical device of claim 1 , wherein said semiconductor material is Ge, said shell including an oxide GeO n with n being between approximately 0 and 2.

16. The optical device of claim 1 , wherein said quantum dot further includes a ligand layer surrounding said substantially crystalline core, said ligand layer including a plurality of surface ligands.

17. The optical device of claim 16 , wherein a surface ligand of said plurality of surface ligands includes a first portion and a second portion, said first portion being coupled to said substantially crystalline core, said second portion being chemically compatible with said matrix material to facilitate dispersing said quantum dot in said matrix material.

18. The optical device of claim 1 , wherein said quantum efficiency is at least 20 percent.

19. The optical device of claim 1 , wherein said quantum efficiency is at least 50 percent.

20. The optical device of claim 1 , wherein said semiconductor material is Si, said substantially crystalline core having a diameter between approximately 1 nm and 20 nm.

21. The optical device of claim 1 , wherein said semiconductor material is Ge, said substantially crystalline core having a diameter between approximately 1 nm and 50 nm.