Superluminescent diode module
A module accommodates multiple superluminescent light emitting diodes, SLEDs, 12 r, 12 g and 12 b . The SLEDs are arranged in an enclosure and output respective light beams to propagate into free space within the enclosure. The individual light beams from the SLED sources are combined into a single beam path within the enclosure using beam combiners 40 r - g, 40 rg - b . Each beam combiner is realized as a planar optical element, the back side of which is arranged to receive a SLED beam and route it through the optical element to the front side where it is combined with another SLED beam that is incident on and reflected by the front side. The free-space propagating combined beam is output from the module via an optical fiber 42 (or through a window).
1 . An optical source module comprising:
a housing defining an enclosure of free space;
first, second and third sources selected from the group of superluminescent light emitting diodes (“SLED”) and laser diodes (“LD”) wherein the first, second and third sources are arranged in the enclosure to emit first, second and third beams having respective first, second and third center wavelengths, the first, second and third beams propagating in the free space along first, second and third beam paths;
a first beam combiner arranged in the enclosure to receive the first beam and the second beam, and to combine them into a combined beam extending in the free space along a combined beam path;
a second beam combiner arranged in the enclosure to receive the combined first and second beam and the third beam, and to combine them to form a combined beam into the combined beam path;
first and second anamorphic prisms arranged in the combined beam path prior to the optical output port which cooperate to provide beam shaping of the combined beam; and
an optical output port arranged to receive the combined beam and to output the combined beam from the housing.
2 . The module of claim 1 , further comprising:
an aperture arranged in the combined path to clean up the combined beam.
3 . The module of claim 2 , wherein the aperture is arranged after the first and second anamorphic prisms.
4 . The module of claim 1 , wherein the optical output port is a window.
5 . The module of claim 4 , further comprising:
an aperture arranged in the combined path to clean up the combined beam, wherein the aperture is integrated into the window.
6 . The module of claim 1 , wherein the optical output port comprises: an optical fiber coupler which is attached to an optical fiber and arranged to couple the combined beam into an end of an optical fiber.
7 . The module of claim 1 , further comprising:
first, second and third power monitors arranged to measure beam power of the first, second and third sources respectively and output an associated power signal.
8 . The module of claim 7 , further comprising:
a controller connected to receive respective power signals from the first, second and third power monitors and operable to control respective drive currents supplied to the first, second and third sources responsive to the respective power signals in order to maintain a desired balance of output powers between the first, second and third beams via feedback control.
9 . The module of claim 7 , wherein the second and third power monitors are arranged to collect light transmitted respectively through the first and second beam combiners.
10 . The module of claim 7 , wherein, at least one of the first, second and third sources is an SLED comprising a front facet and a back facet, said SLED having its power monitor arranged adjacent its back facet.
11 . The module of claim 1 , wherein the first, second and third sources are two SLEDs and one LD.
12 . The module of claim 1 , wherein the first, second and third sources are one SLED and two LDs.
13 . The module of claim 1 , wherein the first, second and third sources are first, second and third SLEDs.
14 . The module of claim 1 , wherein the first, second and third sources are first, second and third LDs.
15 . The module of claim 1 , wherein the first, second and third center wavelengths are selected from different ones of red, green and blue visible wavelengths.
16 . The module of claim 15 , further comprising:
a fourth source selected from the group SLED and LD and arranged in the enclosure to emit a fourth beam having a fourth center wavelength, the fourth beam propagating in the free space along a fourth beam path; and
a fourth beam combiner arranged in the enclosure so that the first to fourth beams are combined to propagate along the combined beam path.
17 . The module of claim 16 , wherein the fourth center wavelength is selected from the group of: a visible wavelength, a near infrared wavelength and an infrared wavelength.
18 . The module of claim 16 , further comprising:
a fifth source selected from the group SLED and LD and arranged in the enclosure to emit a fifth beam having a fifth center wavelength, the fifth beam propagating in the free space along a fifth beam path; and
a fifth beam combiner arranged in the enclosure so that the first to fifth beams are combined to propagate along the combined beam path.
19 . The module of claim 18 , further comprising:
a sixth source selected from the group SLED and LD and arranged in the enclosure to emit a sixth beam having a sixth center wavelength, the sixth beam propagating in the free space along a sixth beam path; and
a sixth beam combiner arranged in the enclosure so that the first to sixth beams are combined to propagate along the combined beam path.
20 . The module of claim 1 further comprising:
a first filter arranged after combining the first beam with the second beam and configured to reject wavelength components that are shorter than the second center wavelength; and
a second filter arranged after combining the previously combined first and second beams with the third beam and configured to reject wavelength components that are shorter than the third center wavelength.
21 . The module of claim 1 further comprising:
a first filter arranged after combining the first beam with the second beam and configured to reject wavelength components that are longer than the second center wavelength; and
a second filter arranged after combining the previously combined first and second beams with the third beam and configured to reject wavelength components that are longer than the third center wavelength.