Semiconductor laser device and circuit for and method of driving same
A directly driven laser includes multiple contacts, with at least one of the contacts for injecting current into the laser such that the laser reaches at least a lasing threshold and at least one of the contacts for providing a data signal to the laser. In some embodiments a differential data signal is effectively provided to a front and a rear section of the laser, while lasing threshold current is provided to a central portion of the laser.
1. A distributed feedback (DFB) laser, comprising:
a waveguide including an active region, with a grating in or about the waveguide, the waveguide having a longitudinal length in a direction between a front facet and a rear facet, the waveguide being generally about layers forming a p-n junction, and an anode electrical contact and a cathode electrical contact;
with at least one of the anode electrical contact and the cathode electrical contact having a longitudinal length in the direction between the front facet and the rear facet less than the longitudinal length of the active region;
wherein the at least one of the anode electrical contact and the cathode electrical contact having a longitudinal length in the direction between the front facet and the rear facet less than the longitudinal length of the active region extends along a front portion of the longitudinal length, the front portion being towards the front facet;
wherein the at least one of the anode electrical contact and the cathode electrical contact having a longitudinal length in the direction between the front facet and the rear facet less than the longitudinal length of the active region is the anode electrical contact; and
further comprising a further anode electrical contact, the further anode electrical contact having a longitudinal length in the direction between the front facet and the rear facet less than the longitudinal length of the active region, with the further anode electrical contact extending along a rear portion of the longitudinal length, the rear portion being towards the rear facet.
2. The DFB laser of claim 1 , wherein one of the anode electrical contact and the further anode electrical contact comprises a modulation current contact and the other of the anode electrical contact and the further anode electrical contact comprises a bias current contact.
3. The DFB laser of claim 2 , further comprising electrical isolation limiting longitudinal movement of current from the modulation current contact and the bias current contact.
4. The DFB laser of claim 3 wherein the electrical isolation comprises an isolation implant.
5. The DFB laser of claim 3 wherein the electrical isolation comprises a trench.
6. A distributed feedback (DFB) laser, comprising:
a waveguide including an active region, with a grating in or about the waveguide, the waveguide having a longitudinal length in a direction between a front facet and a rear facet, the waveguide being generally about layers forming a p-n junction, and an anode electrical contact and a cathode electrical contact;
with at least one of the anode electrical contact and the cathode electrical contact having a longitudinal length in the direction between the front facet and the rear facet less than the longitudinal length of the active region; and
wherein the grating includes a phase shift longitudinally under the at least one of the anode electrical contact and the cathode electrical contact having a longitudinal length in the direction between the front facet and the rear facet less than the longitudinal length of the active region.
7. A method of operating a laser, comprising:
providing a data current signal into a first longitudinal portion of the laser and not providing the data current signal into a second longitudinal portion of the laser; and
providing a bias current signal into the second longitudinal portion of the laser and not providing the bias current signal into the first longitudinal portion of the laser.
8. The method of claim 7 wherein the first longitudinal portion of the laser is a high optical power portion of the laser and the second longitudinal portion of the laser is not a high optical power portion of the laser.
9. The method of claim 7 wherein the first longitudinal portion of the laser is about a front of the laser and the second longitudinal portion of the laser is about a rear of the laser.
10. The method of claim 7 wherein the laser is a distributed feedback laser.
11. The method of claim 7 wherein the laser is a Fabry-Perot (FP) laser.
12. The method of claim 7 wherein the laser is a distributed Bragg (DBR) reflector laser.
13. The method of claim 7 , further comprising providing the data current signal to a third longitudinal portion of the laser.
14. The method of claim 13 wherein the first longitudinal portion of the laser is about a front of the laser, the second longitudinal portion of the laser is about a center of the laser, and the third longitudinal portion of the laser is about a rear of the laser.
15. The method of claim 14 wherein the data current signal is a differential signal, with a first signal of the differential signal provided to the first longitudinal portion of the laser and a second signal of the differential signal provided to the third longitudinal portion of the laser.
16. The method of claim 15 wherein the second signal of the differential signal is the complement of the first signal of the differential signal.
17. The method of claim 15 wherein the first current signal is provided by a driver, and the driver includes an external stage driving an amplifying stage within a package containing the laser.
18. The method of claim 17 wherein the amplifying stage is connected in parallel with the first longitudinal portion of the laser.
19. A method of operating a laser, comprising:
providing a differential signal to a pair of gain stages within a package containing the laser, the differential signal providing a data signal, the pair of gain stages providing a signal to a front portion of the laser and/or a rear portion of the laser depending on state of the differential signal; and
providing a bias signal to a central portion of the laser.
20. A laser and drive circuitry, comprising:
a laser with a first electrical contact and a second electrical contact, each for provision of current signals to the laser, and a contact coupled to ground;
a dc current source coupled to the first electrical contact;
a data signal driver coupled to the second electrical contact;
wherein the laser includes a third electrical contact for provision of current signals to the laser, with the data signal driver coupled to the third electrical contact;
wherein the third electrical contact is longitudinally near the rear facet, the second electrical contact is longitudinally near the front facet, and the first electrical contact is longitudinally between the third electrical contact and the second electrical contact; and
wherein the data signal driver is configured to provide a differential signal over a differential signal line.
21. The laser and drive circuitry of claim 20 wherein a first line of the differential signal line is coupled to the third electrical contact and a second line of the differential signal line is coupled to the second electrical contact.
22. The laser and drive circuitry of claim 21 further comprising an amplifying stage including a pair of gain stages, wherein a first gain stage of the pair of gain stages is coupled to the first line of the differential signal line and the second contact and a second gain stage of the pair of gain stages is coupled to the second line of the differential signal line and the third contact.