CN112713504A

CN112713504A - Thermally tuned DFB laser

Info

Publication number: CN112713504A
Application number: CN202110028275.6A
Authority: CN
Inventors: 严家林
Original assignee: Ningbo Yuanxin Optoelectronic Technology Co ltd
Current assignee: Ningbo Yuanxin Optoelectronic Technology Co ltd
Priority date: 2021-01-11
Filing date: 2021-01-11
Publication date: 2021-04-27

Abstract

The invention discloses a thermally tuned DFB laser, comprising an active region and a reflective region, the active region and the reflective region both include a waveguide structure, the active region further includes a first electrode for inputting a driving current, so The laser also includes a temperature adjustment device capable of conducting heat to the waveguide structure for adjusting the operating temperature of the laser, the temperature adjustment device comprising a resistance wire and a second electrode arranged at both ends of the resistance wire, the resistance wire is in the active area and reflects extend between regions. Compared with the prior art, the present invention has the advantages that: by setting a temperature regulating device in the form of a hot electrode, and by adjusting the current applied to the hot electrode, the working temperature of the laser can be adjusted to realize semi-temperature control and meet low-cost requirements; An insulating layer is arranged under the electrode, and the heating efficiency is high.

Description

Thermally tuned DFB laser

Technical Field

The invention relates to laser technology, in particular to a thermally tuned DFB laser.

Background

A laser is a device that can emit laser light. With the development of optical fiber communication systems, fiber gratings and other technologies, fiber grating lasers have been extensively studied and developed due to the advantages of simple fabrication, narrow line width, anti-electromagnetic interference, high stability and the like. In order to overcome the spatial hole burning effect of the gain medium, a single-mode operation is realized, wherein one scheme is a ring fiber laser, and the other scheme is a linear fiber grating laser. Among them, for linear fiber grating lasers, dbr (distributed Bragg reflector) and dfb (distributed feedback) lasers are increasingly widely used because they have simple structures and low costs and can maintain high-quality laser output.

The two-section DFB laser commonly used in the DFB laser is divided into an active area and a reflecting area, wherein the active area is used for injecting current into the laser, and the reflecting area is used for optical feedback. The wavelength tunable laser system disclosed in chinese patent application No. 201120289301.2 includes a DFB laser module, a thermoelectric cooler, and a control circuit, wherein the DFB laser module is a distributed feedback laser module, the DFB laser module is disposed on the thermoelectric cooler, the thermoelectric cooler circuit is connected to the control circuit, each DFB laser module is a DFB laser module with different wavelength tuning ranges, laser generated by each DFB laser module converges on an optical waveguide, and the system outputs laser beams with different wavelengths. And the microprocessor selects a certain DFB laser module to work according to the emission wavelength, and controls the temperature of the TEC. The control method comprises the following steps: firstly, the TEC is controlled to roughly adjust the DFB output wavelength according to the theory, the TEC of the Etalon is adjusted to be the set temperature, the output laser wavelength is obtained according to the transmission efficiency of the Etalon, and then the DFB output wavelength is accurately controlled.

The existing laser completely controls the temperature of the DFB laser module through the TEC, so that the output wavelength is adjusted, and the manufacturing and working costs are high.

Disclosure of Invention

The technical problem to be solved by the present invention is to provide a thermally tuned DFB laser, which reduces the cost by a semi-temperature control method, in view of the above-mentioned shortcomings of the prior art.

The technical scheme adopted by the invention for solving the technical problems is as follows: a thermally tuned DFB laser comprising an active region and a reflective region, both comprising a waveguide structure, the active region further comprising a first electrode for inputting a drive current, characterized in that: the laser also comprises a temperature adjusting device which can conduct heat to the waveguide structure and is used for adjusting the working temperature of the laser, wherein the temperature adjusting device comprises a resistance wire and second electrodes arranged at two ends of the resistance wire, and the resistance wire extends between the active area and the reflecting area.

In order to facilitate the guiding of the heat generated by the resistance wire to the waveguide structure, a dielectric layer capable of conducting heat covers the resistance wire and the first electrode, and the dielectric layer electrically isolates the first electrode from the second electrode.

Preferably, the first electrode is disposed between the waveguide structure of the active region and the dielectric layer.

In order to facilitate the conduction of the waveguide structure and the first electrode, the waveguide structure is provided with an upper cover layer corresponding to the position of the first electrode in an active area, an insulating layer is arranged on the top surface of the waveguide structure except the top surface of the upper cover layer, and the resistance wire is arranged on the insulating layer.

In order to facilitate the arrangement of the first electrode and electrically isolate the first electrode from the second electrode, a first opening is formed in the position, corresponding to the first electrode, of the dielectric layer, so that the first electrode is embedded into the first opening and directly contacts with the upper cover layer of the waveguide structure, and at least the top of the first opening is closed.

Preferably, the first electrode includes a first active electrode and a second active electrode connected to the first active electrode, and the first active electrode is embedded in the dielectric layer.

In order to improve the heat conduction efficiency, an electric and heat conduction layer covers the dielectric layer.

In order to facilitate the arrangement of the second electrode, two ends of the resistance wire are respectively provided with a bent part formed by bending, a second opening is formed in the position, corresponding to the bent part, of the dielectric layer, the position, corresponding to the second opening, of the electric and heat conduction layer is protruded, the position, corresponding to the second opening, of the electric and heat conduction layer can penetrate through the second opening from the upper side of the dielectric layer so as to be in contact with the resistance wire, and the part, penetrating through the second opening, of the electric.

Preferably, the waveguide structure is a ridge waveguide, the waveguide structure is integrally formed with a ridge, the dielectric layer covers the ridge, and the first electrode is electrically connected to the waveguide structure at the ridge.

To realize the output of laser, the waveguide structure comprises a core layer which receives the current injected by the first electrode to realize the output of laser.

Compared with the prior art, the invention has the advantages that: by arranging the temperature adjusting device in the form of the hot electrode and adjusting the current applied to the hot electrode, the working temperature of the laser can be adjusted, semi-temperature control is realized, and the low-cost requirement is met; the heating efficiency can be improved by arranging the electric and heat conducting layer; by arranging the dielectric layer, electric isolation can be realized on the basis of heat conduction; an insulating layer is arranged below the thermode, so that the heating efficiency is high.

Drawings

FIG. 1 is a schematic diagram of a laser according to an embodiment of the present invention;

FIG. 2 is a cross-sectional view taken along line A-A of the laser of FIG. 1;

FIG. 3 is a cross-sectional view taken along line B-B of the laser of FIG. 1;

FIG. 4 is a cross-sectional view taken along line C-C of the laser of FIG. 1;

FIG. 5 is an exploded view of a laser according to an embodiment of the present invention;

fig. 6 is an equivalent circuit of the prior art DFB laser matching an additional resistor R1 on a microstrip line;

fig. 7 is an equivalent circuit of the DFB laser according to the embodiment of the present invention matching the additional resistor R1 on the microstrip line;

fig. 8 is a graph comparing the intrinsic response curves of a DFB laser according to an embodiment of the invention and a prior art laser.

Detailed Description

Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar functions.

In the description of the present invention, it is to be understood that the terms "central," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," "circumferential," and the like are used in the orientations and positional relationships indicated in the drawings for convenience in describing the present invention and to simplify the description, but are not intended to indicate or imply that the referenced devices or elements must have a particular orientation, be constructed and operated in a particular orientation, and that the directional terms are used for purposes of illustration and are not to be construed as limiting, for example, because the disclosed embodiments of the present invention may be oriented in different directions, "lower" is not necessarily limited to a direction opposite to or coincident with the direction of gravity. Furthermore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature.

Referring to fig. 1 to 5, a thermally tuned DFB laser is a two-stage DFB laser, and includes an active region 1 and a reflective region 2, wherein the active region 1 is used for injecting current, and the reflective region 2 has a structure the same as or different from that of the active region 1. The active region 1 and the reflective region 2 together include a waveguide structure and a grating layer 3, the waveguide structure of the active region 1 may include a core layer 41, a lower cover layer 42 and an upper cover layer 43, and the core layer 41, the lower cover layer 42 and the upper cover layer 43 may all adopt the prior art, for example, the core layer 41 may include an upper confinement layer, an active layer, a lower confinement layer, and the like, which are sequentially arranged from top to bottom (from a side far away from the lower cover layer 42 to a direction close to the lower cover layer 42), so as to realize laser output, and the grating layer is a uniformly distributed bragg grating. A lower cap layer 42 is provided below the core layer 41 for providing sufficient light and carrier confinement. The grating layer 3 is provided in the upper cover layer 43. The waveguide structure of the reflective region 2 may include the same core layer 41 and lower cover layer 42, the grating layer 3 is located above the core layer 41, the insulating layer 9 is disposed above the grating layer 3, and the insulating layer 9 may also be a thermal insulating layer, and when the distance is far enough, the insulating layer 9 may not have a thermal insulating function.

Preferably, the waveguide structure is a ridge waveguide for conducting a driving current, and the ridge waveguide can reduce the driving threshold current of the laser and improve the basic performance of the laser. The waveguide structure is integrally formed with a ridge 45 that is upwardly convex at an intermediate position.

The active region 1 further includes a first electrode 11 for injecting current, the first electrode 11 being disposed on the waveguide structure, including a first active electrode 111 formed on the ridge 45 of the waveguide structure, and a second active electrode 112 formed on one side of the ridge 45, the first active electrode 111 and the second active electrode 112 being integrally connected. The current injected from the first electrode 11 is applied to the waveguide structure, and the waveguide structure into which the drive current is injected functions as an active layer, thereby providing a gain to the laser. Preferably, the first active electrode 111 may be a stripe electrode, and the second active electrode 112 may be a circular electrode. The capping layer 43 corresponds to the first active electrode 111, the capping layer 43 is disposed only at the ridge 45 of the active region 1 and at a position corresponding to a position below the ridge 45, and the other position above the core layer 41 of the active region 1 is covered with the insulating layer 9.

In order to facilitate adjustment of the operating temperature of the laser, a temperature adjustment device is disposed above the ridge 45 or adjacent to the ridge 45, and a second active electrode 112 is disposed on both sides of the ridge 45. The temperature adjusting device comprises a resistance wire 7, the resistance wire 7 extends between the active area 1 and the reflection area 2, two ends of the resistance wire 7 are respectively provided with a bending part 71 which is bent towards the direction far away from the ridge 45, and a second electrode is arranged on the bending part 71 and can be injected with current to the resistance wire 7 to generate heat. The working temperature of the laser can be adjusted by adjusting the current applied to the second electrode.

In order to improve the heating efficiency and prevent the first electrode 11 and the second electrode from generating electric conduction, the ridge 45 and the resistance wire 7 are covered with the dielectric layer 5, and the dielectric layer 5 can ensure electric isolation and thermal conduction. The dielectric layer 5 is provided with a first opening 51 at a position corresponding to the first active electrode 111, so that the first active electrode 111 is embedded into the first opening 51 and directly contacts with the upper cover layer 43 of the waveguide structure, so that the current injected by the first active electrode 111 can be transmitted to the waveguide structure.

An electric and heat conducting layer 6 is arranged above the dielectric layer 5, and the electric and heat conducting layer 6 at least covers the dielectric layer 5 above the resistance wire 7. The dielectric layer 5 is provided with a second opening 52 on the bending part 71 at two ends of the resistance wire 7, the conductive and heat-conducting layer 6 protrudes at a position corresponding to the second opening 52 and can pass through the second opening 52 from above the dielectric layer 5 to be contacted with the resistance wire 7, and the part of the conductive and heat-conducting layer 6 passing through the second opening 52 forms the second electrode, so that the current injected by the second electrode can be transmitted to the resistance wire 7. The dielectric layer 5 is arranged to avoid electrical conduction between the first electrode 11 and the second electrode.

The first opening 51 is closed at least at the top (i.e. the first opening 51 is recessed from bottom to top), and the second opening 52 penetrates through the thickness of the dielectric layer 5.

Therefore, heat generated by the resistance wire 7 can be effectively conducted to the active region 1 through the electric and heat conducting layer 6, and the working temperature of the laser is improved. Alternatively, the resistance wire 7 and the first electrode 11 may be located on the same side of the ridge 45. The arrangement of the electric and heat conducting layer 6 improves the heat conducting efficiency. Furthermore, the second electrode may also be a separately provided electrode, not integral with the layer 6, in contact with the layer 6 only at the second opening 52.

Referring to fig. 3, the equivalent circuit of the matched external resistor R1 on the microstrip line of the DFB laser in the prior art is shown, in which the first inductor L1 is an equivalent inductor such as a gold wire, the first capacitor C1 is an equivalent capacitor of the microstrip line, and the second capacitor C2 and the second resistor R2 are equivalent parasitic capacitors and resistors of the DFB chip. One end of an additional first resistor R1 is used as a first input end, and the other end is connected with one end of a first inductor L1, the other end of the first inductor L1 is connected with one end of a second resistor R2, the other end of the second resistor R2 is used as a second input end, one end of a first capacitor C1 is connected between the first resistor R1 and the first inductor L1, the other end of the first capacitor C1 is connected to the second input end, one end of a second capacitor C2 is connected between the first inductor L1 and the second resistor R2, and the other end of the second capacitor C2 is connected to the second input end.

Referring to fig. 4, an equivalent circuit of the DFB laser of this embodiment is an external resistor R1 matched on the microstrip line, where the first inductor L1 is an equivalent inductor such as a gold wire, the first capacitor C1 is an equivalent capacitor of the microstrip line, the second capacitor C2 and the second resistor R2 are an equivalent parasitic capacitor and a resistor of the DFB chip, the third capacitor C3 is a parasitic capacitor brought by the second electrode 21, and the second inductor L2 and the third resistor R3 are an inductor and a resistor matched with the second electrode 21. One end of an additional first resistor R1 is used as a first input end, and the other end is connected with one end of a first inductor L1, the other end of a first inductor L1 is connected with one end of a second resistor R2, the other end of the second resistor R2 is used as a second input end, one end of a first capacitor C1 is connected between the first resistor R1 and the first inductor L1, the other end of the first capacitor C1 is connected with the second input end, one end of a second capacitor C2 is connected between the first inductor L1 and the second resistor R2, the other end of the second capacitor C2 is connected with the second input end, one end of a third capacitor C3 is connected between the first resistor R1 and the first inductor L1, the other end of the third capacitor C3 is connected with one end of the third resistor R3, the other end of the third resistor R3 is connected with the second input end, and the second inductor R2 is connected with the third resistor R3 in parallel.

Referring to fig. 5, the upper curve is the intrinsic response curve of the prior art, and the lower curve is the intrinsic response curve of the present invention. As can be seen from fig. 5, the DFB laser of the present invention can basically maintain the original direct modulation bandwidth by designing the rf inductor and the resistor matched with the existing laser, so that the resistance wire 7 and the second electrode can still maintain the high-speed modulation.

According to the DFB laser, on the basis of keeping the existing TEC, the resistance wire 7 and the second electrode are additionally arranged, the temperature is controlled through the TEC at low temperature, the temperature is not controlled through the TEC any more when the temperature of the active region 1 is higher than a certain temperature (such as 60 ℃), and the working temperature of the active region 1 is controlled through the resistance wire 7 and the second electrode (the reflecting region 2 is heated at the same time), so that a semi-automatic temperature control mode is realized, and the cost of a device is effectively saved.

The working temperature of the laser can be changed through the current injected by the resistance wire 7 and the second electrode, and the lasing wavelength of the laser can be shifted red along with the rise of the temperature, so that the lasing wavelength of the laser can be adjusted by adjusting the current injected by the resistance wire 7 and the second electrode, and the lasing wavelength can be controlled more accurately.

In addition, the heat insulation layer 9 is arranged below the resistance wire 7, so that heat is not conducted, heat can be directly transmitted to a waveguide structure of the laser, heating efficiency is high, and wide-range work is facilitated.

The direct modulation bandwidth of the DFB laser with the hot electrode can be not lost by optimizing the parameters of an external control circuit, and the height modulation is kept; the wavelength fluctuation range is small, and the wavelength can be controlled more accurately.

In the above embodiment, the DFB laser is a two-stage laser, and alternatively, the resistance wire 7 and the second electrode described above may be used in a one-stage DFB laser.

The waveguide structure may be an electromagnetic waveguide or an optical waveguide.

The China Mobile 5G forward transmission scheme adopts a WDM/MWDM scheme. A low-cost 25G CWDM is adopted to advance a 12-wavelength system, and a TEC is adopted to realize 12 wavelengths with unequal spacing. And the link budget of 10km of 5G forward transmission is met, and the method is suitable for commercial use. The scheme adopts that the upper and lower shifts are respectively carried out for 3.5 nanometers on the basis of 1271nm, 1291nm, 1311nm, 1331nm, 1351nm and 1371nm of CWDM 6 waves to obtain 12 wavelengths with unequal intervals, wherein each wavelength allows the fluctuation of + -2.5 nanometers. By adopting the laser scheme, the laser can work in a higher temperature range, so that the laser can work without the TEC when the working temperature of the laser is higher than a certain temperature. Of course, the laser of the present invention may be used in other fields as well.

Claims

1. A thermally tuned DFB laser comprising an active region (1) and a reflection region (2), the active region (1) and the reflection region (2) both comprising a waveguide structure, the active region (1) It also includes a first electrode (11) for inputting a driving current, characterized in that: the laser further includes a temperature adjustment device capable of conducting heat to the waveguide structure for adjusting the operating temperature of the laser, and the temperature adjustment device includes a resistance wire ( 7) and a second electrode arranged at both ends of the resistance wire (7), the resistance wire (7) extending between the active area (1) and the reflective area (2).

2 . The thermally tuned DFB laser according to claim 1 , wherein the resistance wire ( 7 ) and the first electrode ( 11 ) are covered with a dielectric layer ( 5 ) capable of conducting heat, and the dielectric layer ( 5 ). 3 . ) electrically isolates the first electrode (11) and the second electrode.

3. The thermally tuned DFB laser according to claim 2, wherein the first electrode (11) is arranged between the waveguide structure of the active region (1) and the dielectric layer (5).

4. The thermally tuned DFB laser according to claim 3, characterized in that: the waveguide structure has an upper cap layer (43) corresponding to the position of the first electrode (11) in the active region (1), the waveguide structure An insulating layer (9) is arranged on the top surface of the structure except the top surface of the upper cover layer (43), and the resistance wire (7) is arranged on the insulating layer (9).

5 . The thermally tuned DFB laser according to claim 4 , wherein a first opening ( 51 ) is provided at a position corresponding to the dielectric layer ( 5 ) and the first electrode ( 11 ), so that the first electrode ( 11 ). ) is buried in the first opening (51) to be in direct contact with the upper cover layer (43) of the waveguide structure, and the first opening (51) is closed at least at the top.

6. The thermally tuned DFB laser according to claim 5, wherein the first electrode (11) comprises a first active electrode (111) and a second active electrode (111) connected to the first active electrode (111). A source electrode (112), the first active electrode (111) is embedded in the dielectric layer (5).

7 . The thermally tuned DFB laser according to claim 4 , wherein the dielectric layer ( 5 ) is covered with a conductive and heat-conducting layer ( 6 ). 8 .

8 . The thermally tuned DFB laser according to claim 7 , wherein the two ends of the resistance wire ( 7 ) respectively have bent portions ( 71 ) formed by bending, and the dielectric layer ( 5 ) and the A second opening (52) is provided at a position corresponding to the bent portion (71), and the position of the conductive and heat-conducting layer (6) corresponding to the second opening (52) is raised so as to be able to pass through the first opening (52) from above the dielectric layer (5). The two openings (52) are thus in contact with the resistance wire (7), and the portion of the electrically conductive and thermally conductive layer (6) passing through the second opening (52) constitutes the second electrode.

9. The thermally tuned DFB laser according to any one of claims 4 to 8, wherein the waveguide structure is a ridge waveguide, the waveguide structure is integrally formed with ridges (45), and the dielectric layer (5) Covering the ridge (45), the first electrode (11) is electrically connected to the waveguide structure at the ridge (45).

10. The thermally tunable DFB laser according to any one of claims 1 to 8, wherein the waveguide structure comprises a core layer (41) that receives the current injected by the first electrode (11) to realize laser output.