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US 7,606,282 B2Granted
Optimizing VCSEL mirrors for improving temperature response
AssigneeFinisar Corporation
InventorsRalph H. Johnson, James Guenter
Life of this patent
Estimating the term…
Abstract
Improved slope efficiency in a VCSEL can be accomplished by selecting particular mirror layer compositions and/or mirror layer configurations that minimize increased reflectivity in the top mirror and/or maximize increased reflectivity of the bottom mirror with increasing temperature. Improved reflectivity of the bottom mirror compared to the top mirror over a desired operating temperature range can be facilitated by (i) selecting mirror pairs for the bottom and/or top mirror that gives the bottom mirror pairs a greater increase in contrast ratio with increasing temperature compared to the top-mirror pairs, and/or (ii) including fewer mirror pairs in the bottom mirror than the number of mirror pairs that would give optimal reflectivity.
Claims25
A vertical cavity surface emitting laser (VCSEL), comprising:
- a bottom mirror above a substrate, the bottom mirror comprising a plurality of lower mirror pairs, each lower mirror pair comprised of a first bottom-mirror layer and a second bottom-mirror layer, the first and second bottom-mirror layers having different indices of refraction, wherein the first and second bottom-mirror layers have a contrast ratio that increases with increasing temperature over a desired operating temperature range;
- an active region above the bottom mirror, the active region comprising a plurality of quantum wells;
- and
- an upper mirror above the active region, the upper mirror comprising a plurality of upper mirror pairs, each upper mirror pair comprised of a first upper-mirror layer and a second upper-mirror layer, the first and second upper-mirror layers having different indices of refraction,
- wherein, with increasing temperature over the desired operating temperature range, the contrast ratio of the first and second upper-mirror layers either (i) decreases or (ii) increases to a lesser extent than the contrast ratio of the first and second bottom-mirror layers, thereby reducing fluctuation of a slope efficiency of the VCSEL;
- and
- wherein the VCSEL has an operating wavelength in a range from about 600 nm to about 870 nm and the bottom mirror comprises an AlxGax−1As system, the first bottom-mirror layer having an aluminum content in a range from about 16 atomic % to about 25 atomic % and the second bottom-mirror layer having an aluminum content in a range from about 70 atomic % to about 100 atomic %.
4 more elements
A method of fabricating a VCSEL comprising:
- (a) identifying,
- (i) a first composition for forming a first bottom-mirror layer;
- (ii) a second composition for forming a second bottom-mirror layer, the second composition having a different index of refraction than the first composition;
- (iii) a third composition for forming a first top-mirror layer;
- and
- (iv) a fourth composition for forming a second top-mirror layer, the fourth composition having a different index of refraction than the third composition;
- wherein a contrast ratio between the first and second compositions is identified as increasing more with increasing temperature compared to a contrast ratio between the third and fourth compositions, the compositions therefore being identified as compositions that reduce fluctuations in slope efficiency of the VCSEL;
- (b) forming a bottom mirror having a plurality of alternating first and second bottom-mirror layers comprised of the first and second compositions, respectively;
- (c) forming an active region above the bottom mirror, the active region comprising a plurality of quantum wells;
- and
- (d) forming a top mirror having a plurality of alternating first and second top-mirror layers comprised of the third and fourth compositions, respectively to yield a VCSEL wherein the VCSEL has an operating wavelength in a range from about 600 nm to about 870 nm and the bottom mirror comprises an AlxGax−1As system, the first bottom-mirror layer having an aluminum content in a range from about 16 atomic % to about 25 atomic % and the second bottom-mirror layer having an aluminum content in a range from about 70 atomic % to about 100 atomic %.
8 more elements
A vertical cavity surface emitting laser (VCSEL), comprising:
- a bottom mirror above a substrate, the bottom mirror comprising a plurality of lower mirror pairs, each lower mirror pair comprised of a first bottom-mirror layer and a second bottom-mirror layer, the first and second bottom-mirror layers having different indices of refraction, the bottom mirror having a reflectivity less than 99.8%;
- an active region above the bottom mirror, the active region comprising a plurality of quantum wells;
- an upper mirror above the active region, the upper mirror comprising a plurality of upper mirror pairs, each upper mirror pair comprised of a first upper-mirror layer and a second upper-mirror layer, the first and second upper-mirror layers having different indices of refraction;
- and
- wherein the lower mirror has at least 5 fewer lower-mirror pairs than an optimal number of lower-mirror pairs, the number of lower-mirror pairs being selected such that the lower mirror increases in reflectivity with increasing temperature over a desired operating temperature range from about 15° C. to about 40° C., thereby minimizing fluctuation of a slope efficiency of the VCSEL.
2 more elements
A vertical cavity surface emitting laser (VCSEL), comprising:
- a bottom mirror above a substrate, the bottom mirror comprising a plurality of lower mirror pairs, each lower mirror pair comprised of a first bottom-mirror layer and a second bottom-mirror layer, the first and second bottom-mirror layers having different indices of refraction, wherein the first and second bottom-mirror layers have a contrast ratio that increases with increasing temperature over a desired operating temperature range;
- an active region above the bottom mirror, the active region comprising a plurality of quantum wells;
- and
- an upper mirror above the active region, the upper mirror comprising a plurality of upper mirror pairs, each upper mirror pair comprised of a first upper-mirror layer and a second upper-mirror layer, the first and second upper-mirror layers having different indices of refraction,
- wherein, with increasing temperature over the desired operating temperature range, the contrast ratio of the first and second upper-mirror layers either (i) decreases or (ii) increases to a lesser extent than the contrast ratio of the first and second bottom-mirror layers, thereby reducing fluctuation of a slope efficiency of the VCSEL;
- and
- wherein the VCSEL has an operating wavelength in a range from about 900 nm to about 1100 nm and the bottom mirror comprises an AlxGax−1As system, the first bottom-mirror layer having an aluminum content in a range from about 5 atomic % to about 15 atomic % and the second bottom-mirror layer has an aluminum content in a range from about 70 atomic % to about 100 atomic %.
4 more elements
A vertical cavity surface emitting laser (VCSEL), comprising:
- a bottom mirror above a substrate, the bottom mirror comprising a plurality of lower mirror pairs, each lower mirror pair comprised of a first bottom-mirror layer and a second bottom-mirror layer, the first and second bottom-mirror layers having different indices of refraction, wherein the first and second bottom-mirror layers have a contrast ratio that increases with increasing temperature over a desired operating temperature range;
- an active region above the bottom mirror, the active region comprising a plurality of quantum wells;
- and
- an upper mirror above the active region, the upper mirror comprising a plurality of upper mirror pairs, each upper mirror pair comprised of a first upper-mirror layer comprising TiO2 and a second upper-mirror layer, the first and second upper-mirror layers having different indices of refraction,
- wherein, with increasing temperature over the desired operating temperature range, the contrast ratio of the first and second upper-mirror layers decreases thereby reducing fluctuation of a slope efficiency of the VCSEL;
- wherein the second upper-mirror layer comprises MgF2, SiO2, Al2O3, SiO, Si3N4, ZrO2, HfO2, Si, or a combination thereof.
3 more elements
Dependencies are inferred from the claim text.