Producing bragg gratings in optical waveguides
We describe methods of producing gratings such as Bragg gratings with optical waveguides. Described are the writing and erasing of gratings within SiON waveguides by forming standing waves. Methods, systems, instruments, and devices are described that provide improved transmission of light through such waveguides.
1. A method for producing and subsequently erasing a grating within an optical waveguide comprising:
providing a waveguide comprising a SiON core having a refractive index above 1.6;
irradiating the waveguide with a writing beam having a periodic intensity corresponding to the desired grating for a period of time sufficient to form a grating within the waveguide; and,
erasing the grating by irradiating the waveguide with a second writing beam having a periodic intensity different than that of the writing beam used to form the grating.
2. The method of claim 1 wherein the irradiation is provided within the waveguide.
3. The method of claim 1 wherein the irradiation is provided external to the waveguide.
4. The method of claim 1 wherein the periodic intensity comprises a standing wave.
5. The method of claim 1 wherein the periodic intensity is provided by interference between two or more beams.
6. The method of claim 1 wherein the wavelength of the writing beam is from 450 nm to about 700 nm.
7. The method of claim 1 further wherein in addition to erasing the initial grating, the second writing beam produces a second grating.
8. The method of claim 7 wherein the second grating has a different wavelength.
9. The method of claim 1 wherein the writing beam is in the visible range of wavelengths.
10. The method of claim 1 wherein the writing beam has a wavelength of between 450 nm to 700 nm.
11. The method of claim 1 wherein the gratings are used to couple light between polarization states.
12. The method of claim 1 wherein the gratings are used to couple light between transverse modes.
13. The method of claim 1 wherein the SiON waveguide core has a refractive index above 1.7.
14. The method of claim 1 wherein the SiON waveguide core has a refractive index of about 1.8.
15. The method of claim 1 wherein the waveguide is in a chip.
16. The method of claim 15 wherein the chip comprises a silicon chip.
17. The method of claim 15 wherein the chip further has a coupler that couples light from an external laser into the waveguide.
18. The method of claim 1 wherein the SiON waveguide core is surrounded by SiO 2 .
19. The method of claim 1 wherein the refractive index of the SiON core is brought to above 1.6 by varying the ratio of the elements.
20. The method of claim 1 wherein the refractive index of the SiON core is brought to above 1.6 by varying the ratio of oxygen to nitrogen.
21. The method of claim 1 wherein the refractive index of the SiON core is formed using a deposition process.
22. The method of claim 21 wherein the deposition process is used to vary the ratio of oxygen to nitrogen.
23. The method of claim 1 wherein the refractive index of the SiON core is between 1.6 and 1.8.