Method for making a self-aligned optical guide between an optical source and an optical fiber, and related kit
A method includes placing a fluid guide forming composition in contact with the optical source and with the optical fiber, injecting a first light in the guide forming composition from the optical source and/or from the optical fiber, to harden a central region of the optical guide, illuminating the guide forming composition with the second light to harden a peripheral region of the optical guide by photopolymerization initiated by the second photoinitiator system. The difference between the first peak wavelength and the second peak wavelength being more than 100 nm.
1. A method for making a self-aligned optical guide between an optical source producing a directional emission and an optical fiber comprising:
arranging the optical source and the optical fiber facing one another and defining an intermediate space between them, the optical source being configured to emit a first light having a first peak wavelength comprised between 700 nm and 1600 nm;
placing, in the intermediate space, a fluid guide forming composition in contact with the optical source and with the optical fiber, the guide forming composition comprising a first monomer, a first photoinitiator system able to activate the polymerization of the first monomer when illuminated with the first light, and a second photoinitiator system being able to activate the polymerization of the first monomer when illuminated with a second light having a second peak wavelength, the second photoinitiator system not interacting with the first photoinitiator system when the first photoinitiator system is illuminated with the first light, the difference between the first peak wavelength and the second peak wavelength being more than 100 nm;
injecting the first light in the guide forming composition from the optical source and/or from the optical fiber, to harden a central region of the optical guide by photopolymerization of the first monomer initiated by the first photoinitiator system, the central region connecting the optical source and the optical fiber; and
illuminating the guide forming composition with the second light to harden a peripheral region of the optical guide by photopolymerization of the first monomer initiated by the second photoinitiator system.
2. The method according to claim 1 , wherein the second light has a peak wavelength of strictly less than 650 nm.
3. The method according to claim 1 , wherein the first light has a peak wavelength comprised between 700 nm and 900 nm.
4. The method according to claim 1 , wherein the first light has a peak wavelength comprised between 1200 nm and 1400 nm.
5. The method according to claim 1 , wherein the second light has a peak wavelength of less than 450 nm.
6. The method according to claim 1 , wherein the first monomer is an acrylate monomer.
7. The method according to claim 6 , wherein the guide forming composition comprises a second acrylate monomer distinct from the first acrylate monomer the first and second acrylate monomer forming a mixture of monomers, the photopolymerization of the mixture of monomers being initiation by first and second initiator in corresponding steps.
8. The method according to claim 7 , wherein one of the first and the second acrylate monomers is a diacrylate, the other one of the first and the second acrylate monomers being a triacrylate, the first acrylate monomer comprising an epoxy bisphenol A diacrylate oligomer and the second acrylate monomer comprising a branched triacrylate.
9. The method according to claim 7 , wherein both the first and the second acrylate monomers are diacrylates, the first acrylate monomer being an epoxy bisphenol A diacrylate and the second acrylate monomer being a tri-propylene glycol diacrylate.
10. The method according to claim 1 , wherein the difference between the optical index along the axis of the optical guide in the central region and at the periphery of the optical guide in the peripheral region after hardening of the central region and of the peripheral region is greater than 5 x10 −4 .
11. The method according to claim 1 , wherein the first photoinitiator system comprises at least a photosensitizer, and an initiator.
12. The method according to claim 1 , wherein the injection of the first light is done simultaneously through the optical source and through the optical fiber.
13. The method according to claim 12 , wherein the light power density of the first light injected through the optical source is different of more than 20% from the power of the first light injected through the optical fiber.
14. The method according to claim 1 , wherein the light power density of the first light injected in the guide forming composition is between 100 W/cm 2 and 10 KW/cm 2 .
15. The method according to claim 1 , wherein the optical source is chosen among a VCSEL and an additional optical fiber.
16. The method according to claim 1 , wherein the optical fiber is a single mode optical fiber.
17. The method according to claim 1 , wherein at least after the injection of the first light, the optical guide is flexible, the method comprising a step of bending the optical guide to form a bend between a first end portion of the optical guide connected to the optical source and a second end portion of the optical guide connected to the optical fiber.
18. A kit for making a self-aligned optical guide between an optical source and an optical fiber, comprising:
an optical source and an optical guide intended for being arranged facing one another and for defining an intermediate space between them, the optical source being configured to produce a directional emission of a first light having a first peak wavelength comprised between 700 nm and 1600 nm;
a second light source being configured to emit a second light having a second peak wavelength, the difference between the first peak wavelength and the second peak wavelength being more than 100 nm;
a fluid guide forming composition intended for being placed in contact with the optical source and the optical fiber, the guide forming composition comprising a first monomer, and a first photoinitiator system able to activate the photopolymerization of the first monomer when illuminated with a first light, and a second photoinitiator system being able to activate the polymerization of the first monomer when illuminated with the second light, the second photoinitiator system not interacting with the first photoinitiator system when the first photoinitiator system is illuminated with the first light;
the optical source being able to inject the first light in the guide forming composition, to harden a central region of the optical guide by photopolymerization of the first monomer initiated by the first photoinitiator system,
the second light source being able to illuminate the guide forming composition with the second light to harden a peripheral region of the optical guide by photopolymerization of the first monomer initiated by the second photoinitiator system.