Mirror structure for reducing the effect of feedback on a VCSEL
View Patent ↗An exemplary embodiment of the present invention integrates an absorbing layer into the emitting mirror of a VCSEL to reduce the reflectivity of the emitting mirror as seen by the feedback optical wave. The absorbing layer may be made of a suitable semiconductor material, such as a GaAs layer in a laser emitting near 850 nm or highly doped p-layer, and may disposed epitaxially in a semiconductor or metamorphic mirror. Alternatively, a metal layer may be disposed in the dielectric portion of a hybrid mirror or all-dielectric mirror.
1. A vertical cavity surface emitting laser, comprising:
an optical cavity adjacent a first mirror;
an emitting mirror adjacent said optical cavity;
a mode defining aperture for controlling transverse modes; and
an absorbing layer integrated within the emitting mirror,
wherein said absorbing layer is laterally located within at least a portion of said mode defining aperture, and
wherein said absorbing layer is located at or near a null in the standing optical wave pattern in closest proximity to an emission facet so as to minimally interact with transmission light in the optical cavity, and further so as to strongly interact with external light reflected back into the cavity.
2. A vertical cavity surface emitting laser, comprising:
an optical cavity adjacent a firs mirror;
an emitting mirror adjacent said optical cavity;
a mode defining aperture for controlling transverse modes; and
an absorbing layer integrated within the emitting mirror,
wherein said absorbing layer is laterally located within at least a portion of said mode defining aperture, and
wherein said absorbing layer comprises a layer of conductive material.
3. The vertical cavity surface emitting laser of claim 2 wherein said conductive material comprise, titanium.
4. The vertical cavity surface emitting laser of claim 1 wherein said absorbing layer comprises a layer of semiconductor material.
5. The vertical cavity surface emitting laser of claim 4 wherein said semiconductor material is doped p-type.
6. The vertical cavity surface emitting laser of claim 4 wherein the semiconductor material is a narrow bandgap material, and wherein an absorption edge of said semiconductor material is at a longer wavelength than emission wavelength of said vertical cavity surface emitting laser.
7. The vertical cavity surface emitting laser of claim 1 wherein said emitting mirror comprises a DBR having a plurality of mirror periods.
8. The vertical cavity surface emitting laser of claim 1 wherein said upper ohmic contact comprises an intracavity contact coupled to the optical cavity.
9. The vertical cavity surface emitting laser of claim 8 wherein said emitting mirror comprises a dielectric DBR having a plurality of mirror periods.
10. The vertical cavity surface emitting laser of claim 9 wherein optical thickness of mirror period containing said absorbing layer does not equal optical thickness of remaining mirror periods.
11. The vertical cavity surface emitting laser of claim 10 wherein said absorbing layer comprises a layer of conductive material.
12. The vertical cavity surface emitting laser of claim 11 wherein said conductive material comprises titanium.
13. The vertical cavity surface emitting laser of claim 1 wherein said emitting mirror comprises a hybrid mirror having a semiconductor portion and a dielectric portion.
14. The vertical cavity surface emitting laser of claim 13 wherein said absorbing layer is integrated within said dielectric portion.
15. The vertical cavity surface emitting laser of claim 14 wherein said absorbing layer comprises a layer of conductive material.
16. The vertical cavity surface emitting laser of claim 15 wherein said conductive material comprises titanium.
17. A vertical cavity surface emitting laser, comprising:
an optical cavity adjacent a first mirror;
a semiconductor emitting mirror adjacent said optical cavity; and
an absorbing layer integrated within the emitting mirror,
wherein said absorbing layer is located at or near a null in the standing optical wave pattern in closest proximity to an emission facet so as to minimally interact with transmission light in the optical cavity, and further so as to strongly interact with external light reflected back into the cavity.
18. The vertical cavity surface emitting laser of claim 17 wherein said absorbing layer comprises a layer of semiconductor material.
19. The vertical cavity surface emitting laser of claim 18 wherein said semiconductor material is doped p-type.
20. The vertical cavity surface emitting laser of claim 18 wherein the semiconductor material is a narrow bandgap material, and wherein an absorption edge of said semiconductor material is at a longer wavelength than emission wavelength of said vertical cavity surface emitting laser.