Electro-absorption modulated laser with integrated filter layer
The present disclosure is generally directed to an EML with a filter layer disposed between an active region of the EML and a substrate of the EML to absorb a portion of unmodulated light energy, and preferably the unmodulated light energy caused by transverse electric (TE) substrate mode. The filter layer preferably comprises a material with an energy band gap (Eg) that is less than the energy band gap of the predetermined channel wavelength to absorb unmodulated laser light.
1. An electro-absorption modulated laser (EML) to emit a predetermined channel wavelength, the EML comprising:
a substrate;
a distributed feedback (DFB) section provided by a first plurality of layers disposed on the substrate;
an electro-absorption modulator (EAM) section provided by a second plurality of layers disposed on the substrate;
an active region provided by the DFB section and the EAM section;
a filter layer disposed between the substrate and the active region, the filter layer comprising a material with an energy band gap less than an energy bandgap of the predetermined channel wavelength.
2. The EML of claim 1 , wherein the predetermined channel wavelength is in a range of 1260 to 1650 nm.
3. The EML of claim 2 , wherein the filter layer comprises indium gallium arsenide (InGaAs).
4. The EML of claim 3 , wherein the material forming the filter layer is selected from a group consisting of indium gallium arsenide (InGaAs), indium gallium arsenide phosphide (InGaAsP), indium gallium arsenide phosphide antimony (InGaAsSb), and aluminum gallium indium arsenic (AlGaInAs).
5. The EML of claim 1 , wherein the filter layer has an overall thickness in a range of 200 to 2000 Angstrom.
6. The EML of claim 1 , wherein the filter layer is disposed directly on the substrate.
7. The EML of claim 1 , wherein the active region includes a multi-quantum well (MQW), and wherein the filter layer is disposed from a waveguide core provided by the MQW at a first offset distance OD 1 .
8. The EML of claim 7 , wherein the first offset distance OD 1 is in a range of 1.5 to 3.0 microns.
9. The EML of claim 7 , further comprising a spacer layer disposed between the filter layer and the waveguide core of the MQW.
10. The EML of claim 9 , wherein the spacer layer comprises indium phosphide (InP).
11. The EML of claim 9 , wherein the first offset distance OD 1 is provided at least in part by the spacer layer.
12. The EML of claim 1 implemented as a buried heterostructure (BH) EML.
13. The EML of claim 1 implemented as a ridge-waveguide (RWG) EML.
14. A transmitter optical subassembly (TOSA) comprising:
an electro-absorption modulated laser (EML) to emit a predetermined channel wavelength, the EML comprising a plurality of layers disposed on a substrate to provide an active region, and wherein the EML includes a filter layer disposed between the substrate and the active region, the filter layer comprising a material with an energy band gap that is less than the energy band gap of the predetermined channel wavelength.
15. The TOSA of claim 14 , wherein the predetermined channel wavelength is in a range of 1260 to 1650 nm.
16. The TOSA of claim 14 , wherein the filter layer comprises indium gallium arsenide (InGaAs).
17. The TOSA of claim 14 , wherein the material forming the filter layer is selected from a group consisting of indium gallium arsenide (InGaAs), indium gallium arsenide phosphide (InGaAsP), indium gallium arsenide phosphide antimony (InGaAsSb), and aluminum gallium indium arsenic (AlGaInAs).
18. The TOSA of claim 14 , wherein the filter layer has an overall thickness in a range of 200 to 2000 Angstrom.
19. The EML of claim 1 , wherein the filter layer is configured to absorb at least a portion of unmodulated light.
20. The TOSA of claim 14 , wherein the filter layer is configured to absorb at least a portion of unmodulated light.