Bandwith enhanced DFB+R lite laser
A distributed feedback plus reflection (DFB+R) laser includes an active section, a passive section, a low reflection (LR) mirror, and an etalon. The active section includes a distributed feedback (DFB) grating and is configured to operate in a lasing mode. The passive section is coupled end to end with the active section. The LR mirror is formed on or in the passive section. The etalon includes a portion of the DFB grating, the passive section, and the LR mirror. The lasing mode of the active section is aligned to a long-wavelength edge of a reflection peak of the etalon.
1 . A distributed feedback plus reflection (DFB+R) laser, comprising:
a distributed feedback (DFB) section having a first length between 60 to 150 microns and having a high reflection (HR) element; and
a passive section coupled to the DFB section, the passive section having a second length between 30 to 80 microns and having a low reflection (LR) element opposite the DFB section, wherein the LR element occupies a subset of the second length with a portion of the passive section being between the LR element and the DFB section;
wherein the DFB+R laser is directly modulated and is configured to operate uncooled;
wherein a portion of the DFB section, the passive section, and the LR element form an etalon having a reflection profile with periodic peaks and valleys, and
wherein the DFB section is configured to operate in a lasing mode aligned to a long-wavelength edge of one of the periodic peaks of the reflection profile of the etalon and the lasing mode has only a single mode hop throughout a bias range of the passive section.
2 . The DFB+R laser of claim 1 , wherein the LR element comprises:
an LR mirror having a reflectivity of 15% or less;
an LR mirror formed at a front of the passive section; or
an LR coating formed on an output facet of the DFB+R laser.
3 . The DFB+R laser of claim 1 , wherein the LR element comprises an LR distributed Bragg reflector (DBR) formed in the passive section.
4 . The DFB+R laser of claim 3 , wherein a length of the LR DBR is 12 microns; and wherein a kappa of the LR DBR is at least 180 centimeter −1 .
5 . The DFB+R laser of claim 4 , wherein the DFB+R laser further comprises an anti-reflection coating formed on the output facet of the passive section.
6 . The DFB+R laser of claim 1 , wherein the HR element comprises:
an HR mirror having a reflectivity of 30% or more;
an HR mirror coupled to or formed at a rear of the DFB section; or
an HR distributed Bragg reflector (DBR) mirror.
7 . The DFB+R laser of claim 6 , wherein the HR element comprises the HR DBR mirror, wherein a length of the HR DBR mirror is 15 microns, and wherein a kappa of the HR DBR mirror is between 500 cm −1 to 1500 cm −1 .
8 . The DFB+R laser of claim 6 , wherein HR DBR mirror is formed in a multiple quantum well (MQW) layer of the DFB section.
9 . The DFB+R laser of claim 1 , further comprising a modulation contact coupled to the DFB section and configured to provide a modulation signal to the DFB section to modulate the DFB section, wherein modulation of the DFB section is configured to modulate cavity loss of the DFB+R laser and is configured to increase the carrier-photon resonance frequency (Fr) of the DFB+R laser.
10 . The DFB+R laser of claim 9 , wherein the carrier-photon resonance frequency (Fr) is at least 40 GHz.
11 . The DFB+R laser of claim 1 , further comprising a bias contact coupled to the passive section and configured to provide a bias signal to the passive section.
12 . The DFB+R laser of claim 1 , wherein the DFB section comprises an active section having a distributed feedback (DFB) grating; and wherein:
the passive section comprises a passive waveguide coupled end-to-end with the active section; or
the passive section comprises a pullback portion of the active section configured to be unpumped.
13 . The DFB+R laser of claim 1 , wherein a total cavity length of the DFB+R laser is at least 150 microns; and wherein a front end of the DFB+R laser has a recess etched therein, the recess having a front facet offset from the front end, the front facet having an anti-reflective coating.
14 . The DFB+R laser of claim 13 , wherein the DFB section comprises an active section having a distributed feedback (DFB) grating; and wherein:
the passive section comprises a passive waveguide coupled end-to-end with the active section;
the passive section comprises a passive waveguide coupled end-to-end with the active section and having a grating; or
the passive section comprises a pullback portion of the active section configured to be unpumped, the pullback portion having a DBR mirror.
15 . The DFB+R laser of claim 1 , wherein a total cavity length of the DFB+R laser is at least 150 microns; and wherein a rear end of the DFB+R laser has a recess etched therein, the recess having a rear facet offset from the rear end.
16 . The DFB+R laser of claim 15 , wherein the DFB section comprises an active section having a distributed feedback (DFB) grating; and wherein the HR element of the DFB section comprises:
an HR coating formed on the rear facet;
an HR mirror coupled to or formed at the rear of the DFB section; or
an HR distributed Bragg reflector (DBR) mirror.
17 . The DFB+R laser of claim 1 , wherein the bias range is from a threshold current to 100 mA.
18 . A method comprising:
directly modulating a distributed feedback plus reflection (DFB+R) laser in uncooled operation;
generating laser light in a distributed feedback (DFB) section of the DFB+R laser having a first length between 60 to 150 microns and having a high reflection (HR) element;
coupling the laser light from the DFB section to a passive section having a second length between 30 to 80 microns and having a low reflection (LR) element, wherein the LR element occupies a subset of the second length with a portion of the passive section being between the LR element and the DFB section;
resonating the laser light in an etalon formed by a portion of the DFB section, the passive section, and the LR element, the etalon having a reflection profile with periodic peaks and valleys; and
operating the DFB section in a lasing mode aligned to a long-wavelength edge of one of the periodic peaks of the reflection profile of the etalon and such that the lasing mode has only a single mode hop throughout a bias range of the passive section.
19 . The method of claim 18 , wherein resonating the laser light in the etalon comprises:
reflecting the laser light with an LR mirror for the LR element having a reflectivity of 15% or less;
reflecting the laser light with an LR mirror for the LR element formed at a front of the passive section;
reflecting the laser light with an LR coating for the LR element formed on an output facet of the DFB+R laser; or
reflecting the laser light with an LR distributed Bragg reflector (DBR) for the LR element formed in the passive section.
20 . The method of claim 18 , wherein reflecting the laser light with the HR element comprises:
reflecting the laser light with an HR mirror for the HR element having a reflectivity of 30% or more;
reflecting the laser light with an HR mirror for the HR element coupled to or formed at a rear of the DFB section; or
reflecting the laser light with an HR distributed Bragg reflector (DBR) mirror for the HR element.
21 . The method of claim 18 , wherein directly modulating the DFB+R laser in the uncooled operation comprises modulating the DFB section with a modulation signal configured to modulate cavity loss of the laser and configured to increase carrier-photon resonance frequency (Fr) of the laser.
22 . The method of claim 21 , comprising increasing the carrier-photon resonance frequency (Fr) to at least 40 GHz.
23 . The method of claim 18 , wherein generating the laser light in the distributed feedback (DFB) section of the DFB+R laser comprises operating an active section having a distributed feedback (DFB) grating.
24 . The method of claim 18 , further comprising providing a bias signal to the passive section with a bias contact coupled to the passive section.