KR102400522B1 - Wavelength tunable laser device - Google Patents

Abstract

a substrate having a gain region, a phase control region, a distribution region, a lower clad layer disposed on the substrate, diffraction gratings disposed in the lower clad layer over the distribution region, disposed on the lower clad layer, the distribution region an optical waveguide extending from to the gain region, an upper clad layer disposed on the optical waveguide, and first to third electrodes disposed on the upper clad layer of the distribution region, the phase adjustment region, and the gain region, respectively Provided is a tunable laser device comprising It may be the same as the overlapping of the first grid pattern and the second grid pattern having a second length and a second interval in the first direction.

Description

Tunable laser device {WAVELENGTH TUNABLE LASER DEVICE}

The present invention relates to a tunable laser device, and more particularly, to a distributed feedback laser diode.

Among semiconductor-based optical devices, functional laser devices that select a specific wavelength, such as a distributed feedback laser diode and/or a distributed Bragg reflector laser diode, are being developed. These functional laser devices may perform wavelength filtering using a diffraction grating. For example, only the light wave having a specific wavelength corresponding to the Bragg wavelength due to the periodic refractive index change of the light wave may be reflected. Thereby, wavelength filtering can be achieved. The reflected light wave of a specific wavelength may be oscillated by being fed back to the gain region.

An object of the present invention is to provide a tunable laser device having a short length.

Another object to be solved by the present invention is to provide a tunable laser device having a low threshold current.

The problems to be solved by the present invention are not limited to the problems mentioned above, and other problems not mentioned will be clearly understood by those skilled in the art from the following description.

A tunable laser device according to embodiments of the present invention for solving the above technical problems includes a substrate having a gain region, a phase adjustment region, and a distribution region, a lower clad layer disposed on the substrate, and the lower portion on the distribution region diffraction gratings disposed in the cladding layer, an optical waveguide disposed on the lower clad layer and extending from the distribution region to the gain region, an upper clad layer disposed on the optical waveguide, and the distribution region, the phase adjustment and first to third electrodes respectively disposed on the upper clad layer in the region and the gain region. The diffraction gratings may be distributed in a direction parallel to the substrate and the optical waveguide. The arrangement pattern of the diffraction gratings may be the same as that of overlapping a first grating pattern having a first length and a first interval in the first direction and a second grating pattern having a second length and a second interval in the first direction can

A tunable laser device according to embodiments of the present invention for solving the above technical problems includes a substrate having a gain region, a phase adjustment region, and a distribution region, a lower clad layer disposed on the substrate, and the lower portion on the distribution region first diffraction gratings disposed in a clad layer, an optical waveguide disposed on the lower clad layer and extending from the distribution region to the gain region, an upper clad layer disposed on the optical waveguide, the upper portion on the base distribution region It may include second diffraction gratings disposed in the cladding layer, and first to third electrodes disposed on the upper clad layer of the distribution region, the phase adjustment region, and the gain region, respectively. The first and second diffraction gratings may be distributed in a direction parallel to the substrate and the optical waveguide. A period of the first diffraction gratings may be different from a period of the second diffraction gratings.

In the tunable laser device according to embodiments of the present invention, the diffraction gratings may have high reflectance and a narrow bandwidth. In addition, the diffraction gratings may be set to have an optimized reflectance according to the laser light. In addition, the tunable laser device exhibits a high negative mode suppression rate, and single-mode oscillation characteristics can be stably exhibited.

1 and 2 are cross-sectional views illustrating a tunable laser device according to embodiments of the present invention.
3 is a diagram for explaining a diffraction grating.
4 and 5 are diagrams for explaining reflection spectra of diffraction gratings.
6 is a view for explaining an oscillation spectrum of a tunable laser device.
7 is a view for explaining a tuning spectrum of a tunable laser device.
8 and 9 are cross-sectional views illustrating a tunable laser device according to embodiments of the present invention.

In order to fully understand the configuration and effect of the present invention, preferred embodiments of the present invention will be described with reference to the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, and may be implemented in various forms and various changes may be made. However, it is provided so that the disclosure of the present invention is complete through the description of the present embodiments, and to completely inform those of ordinary skill in the art to which the present invention belongs, the scope of the invention. Those of ordinary skill in the art will understand that the inventive concept may be practiced in any suitable environment.

The terminology used herein is for the purpose of describing the embodiments and is not intended to limit the present invention. In this specification, the singular also includes the plural unless specifically stated otherwise in the phrase. As used herein, 'comprises' and/or 'comprising' refers to the presence of one or more other components, steps, operations and/or elements mentioned. or addition is not excluded.

When a film (or layer) is referred to as being on another film (or layer) or substrate in the present specification, it may be formed directly on the other film (or layer) or substrate or a third film (or layer) between them. or layer) may be interposed.

In various embodiments of the present specification, the terms first, second, third, etc. are used to describe various regions, films (or layers), etc., but these regions and films should not be limited by these terms. do. These terms are only used to distinguish one region or film (or layer) from another region or film (or layer). Accordingly, a film quality referred to as a first film quality in one embodiment may be referred to as a second film quality in another embodiment. Each embodiment described and illustrated herein also includes a complementary embodiment thereof. Parts indicated with like reference numerals throughout the specification indicate like elements.

Unless otherwise defined, terms used in the embodiments of the present invention may be interpreted as meanings commonly known to those of ordinary skill in the art.

Hereinafter, a tunable laser device according to the concept of the present invention will be described with reference to the drawings.

1 and 2 are cross-sectional views illustrating a tunable laser device according to embodiments of the present invention. 3 is a diagram for explaining a diffraction grating.

1 , a tunable laser device according to the concept of the present invention may be provided. The tunable laser device may be a distributed Bragg reflector (DBR) laser diode. The tunable laser device may include a substrate 10 , a lower clad layer 20 , an optical waveguide 30 , an upper clad layer 40 , diffraction gratings 70 , and electrodes 52 , 54 , 56 . have.

The substrate 10 may include indium phosphorus (InP). The substrate 10 may have a gain region G, a phase adjustment region P, and a distribution region D. The substrate 10 may be grounded. According to other embodiments, the substrate 10 may not include the phase adjustment region P. For example, as shown in FIG. 2 , the substrate 10 may include a gain region G and a distribution region D adjacent to each other.

A lower clad layer 20 may be disposed on the substrate 10 . The refractive index of the lower clad layer 20 may be higher than that of the substrate 10 and lower than that of the optical waveguide 30 to be described later. The lower clad layer 20 may include n-type indium phosphorus (InP).

An optical waveguide 30 may be disposed on the lower clad layer 20 . The optical waveguide 30 may extend in a direction parallel to the substrate 10 . The optical waveguide 30 may include intrinsic InP. The optical waveguide 30 may include an active optical waveguide 32 and a passive optical waveguide 34 . The active optical waveguide 32 may be disposed on the gain region G. The passive optical waveguide 34 may be connected to the active optical waveguide 32 . The passive optical waveguide 34 may be disposed on the phase adjustment region P and the distribution region D. On the other hand, in the case of the embodiment of FIG. 2 in which the substrate 10 does not have the phase adjustment region P, the optical waveguide 30 has an active optical waveguide 32 on the gain region G and a passive optical waveguide on the distribution region D. An optical waveguide 34 may be included.

An upper clad layer 40 may be disposed on the optical waveguide 30 . The upper clad layer 40 may include n-type indium phosphorus (InP). The upper clad layer 40 may have a lower refractive index than that of the optical waveguide 30 .

First to third electrodes 52 , 54 , and 56 may be disposed on the upper clad layer 40 . The first to third electrodes 52 , 54 , and 56 may be disposed on the gain region G, the phase adjustment region P, and the distribution region D, respectively. The first to third electrodes 52 , 54 , and 56 may provide current to the substrate 10 . The current may electrically change refractive indices of the lower clad layer 20 , the optical waveguide 30 , and the upper clad layer 40 . Alternatively, in the embodiment of FIG. 2 in which the substrate 10 does not have the phase control region P, the second electrode 54 may not be provided.

When a current is provided to at least one of the first to third electrodes 52 , 54 , and 56 , laser light 80 may be generated along the optical waveguide 30 .

When a current is applied to the first electrode 52 , the active optical waveguide 32 in the gain region G may obtain a gain of the laser light 80 . The intensity of the laser light 80 may be proportional to the current applied to the first electrode 52 .

When a current is applied to the second electrode 54 , the phase of the laser light 80 may be modulated. The current applied to the second electrode 54 may electrically change the refractive index of the passive optical waveguide 34 in the phase control region P to tune the wavelength of the laser light 80 .

First and second anti-reflection coating layers 62 and 64 may be disposed on both sides of the optical waveguide 30 . The first and second anti-reflective coating layers 62 and 64 may be disposed on both sidewalls of edges of the lower clad layer 20 , the optical waveguide 30 , and the upper clad layer 40 . The first and second anti-reflection coating layers 62 and 64 may resonate the laser light 80 traveling through the optical waveguide 30 . The laser light 80 may be output through the second anti-reflection coating layer 64 to the outside.

Diffraction gratings 70 may be disposed in the lower clad layer 20 . The diffraction gratings 70 may be disposed in the lower clad layer 20 of the distribution region D. The diffraction gratings 70 may be spaced apart from the optical waveguide 30 in a direction perpendicular to the substrate 10 . The diffraction gratings 70 may include P-type indium phosphorus (InP), indium gallium arsenide (InGaAs), or a cavity. The patterns of the diffraction gratings 70 may be arranged in the same direction as the direction in which the optical waveguide 30 extends. The patterns of the diffraction gratings 70 may have a width or length of 0.1 μm. The patterns of the diffraction gratings 70 may have an interval of 0.1 μm. Hereinafter, patterns of the diffraction gratings 70 will be described in detail with reference to FIG. 3 .

Referring to FIG. 3 , each of the patterns of the diffraction gratings 70 may be disposed to have different lengths L and spacing S. The arrangement pattern of the diffraction gratings 70 may be the same as that in which two patterns having different periods are overlapped. In detail, the arrangement pattern of the diffraction gratings 70 may be the same as that of superimposing the virtual first grating patterns 72 and the second grating patterns 74 . The period Δ1 of the first grid patterns 72 and the period Δ2 of the second grid patterns 74 may be different from each other. For example, the first grid patterns 72 may have a first length L1 and may be arranged at a first interval S1 . The second grid patterns 74 may have a second length L2 and may be arranged at a second interval S2 . In this case, the second length L2 may be longer than the first length L1 , and the second interval S2 may be longer than the first interval S1 . As shown in FIG. 2 , when the first grating patterns 72 and the second grating patterns 74 are overlapped, the length L of the arrangement pattern of the diffraction gratings 70 is the second length L2 . ) and may periodically change within a range shorter than the sum (2×L1+L2) of twice the first length L1 and the second length L2. The interval S of the diffraction gratings 70 is longer than the difference S2-S1 between the second interval S2 and the first interval S1, and periodically changes within a range shorter than the second interval S2. can

The reflection spectrum of the diffraction gratings 70 may be adjusted according to the arrangement pattern as described above. For example, the reflection spectrum of the diffraction gratings 70 may correspond to an intersection region of the reflection spectrum of the first grating patterns 72 and the reflection spectrum of the second grating patterns 74 . The bandwidth of the laser light 80 may be changed according to the arrangement pattern of the diffraction gratings 70 .

4 and 5 are diagrams for explaining reflection spectra of diffraction gratings.

Referring to FIG. 4 , the reflection spectra of the comparative example having a constant period (length and spacing) and the example having the diffraction gratings 70 of the present invention were compared. As shown in FIG. 4 , compared to the reflection spectrum of the comparative example, it can be confirmed that the reflection spectrum of the following example provides an appropriate reflectance for the operation of the laser and the bandwidth is reduced at the same time.

Meanwhile, the reflection spectrum of the diffraction gratings 70 may be changed according to the period Δ1 of the first grating patterns 72 and the period Δ2 of the second grating patterns 74 . Referring to FIG. 5 , the difference Δ between the period Δ1 of the first grating patterns 72 and the period Δ2 of the second grating patterns 74 is changed, and the diffraction gratings 70 ) was calculated. As shown in FIG. 5 , according to the difference Δ between the period Δ1 of the first grating patterns 72 and the period Δ2 of the second grating patterns 74 , the diffraction gratings 70 ), the maximum value and width of the reflection spectrum peak may vary. Accordingly, the period Δ1 of the first grating patterns 72 and the period Δ of the second grating patterns 74 so that the diffraction gratings 70 have an optimized reflectance according to the laser light 80 . 2) can be set.

6 is a view for explaining an oscillation spectrum of a tunable laser device.

Referring to FIG. 6 , the laser oscillation characteristics of the comparative example having a constant period (length and spacing) were compared with the laser oscillation characteristics of the example having the diffraction gratings 70 of the present invention. In the case of the comparative example, other peaks are also found around the main peak, and it can be seen that the embodiment has a higher side-mode suppression ratio than the comparative example. In addition, in the case of the embodiment, it can be seen that the threshold current (Ith) is about 12.4 mA, which is suitable for direct modulation.

7 is a view for explaining a tuning spectrum of a tunable laser device. The wavelength tunability of the tunable laser element is obtained by injecting current into the distribution region D to change the effective refractive index of the optical waveguide. 7 is a graph of measuring the wavelength mobility of the oscillation mode according to the injection of current, and the wavelength at which the oscillation mode appears in the tunable laser device is measured by injecting different currents into the distribution region (D). As shown in FIG. 7 , it can be seen that the tunable laser device exhibits a high negative mode suppression ratio when an applied current is applied, and stably exhibits single-mode oscillation characteristics.

In the tunable laser device according to embodiments of the present invention, the diffraction gratings may have a narrow bandwidth while maintaining appropriate reflectivity. In addition, the diffraction gratings may be set to have an optimized reflectance according to the laser light. In addition, the tunable laser device exhibits a high negative mode suppression rate, and single-mode oscillation characteristics can be stably exhibited.

8 and 9 are cross-sectional views illustrating a tunable laser device according to embodiments of the present invention. Here, for convenience of description, the description will be focused on points that are different from or not described above, and the omitted parts are according to the embodiments of the above-described content of the present invention.

Referring to FIG. 8 , a tunable laser device may be provided. The tunable laser device may be a distributed Bragg reflector (DBR) laser diode. The tunable laser device includes a substrate 10 , a lower clad layer 20 , an optical waveguide 30 , an upper clad layer 40 , diffraction gratings 76 , 78 , and electrodes 52 , 54 , 56 . can do.

The substrate 10, the lower clad layer 20, the optical waveguide 30, the upper clad layer 40, and the electrodes 52, 54, and 56 of the tunable laser device are as described with reference to FIGS. 1 and 2 . may be the same/similar.

The diffraction gratings 76 , 78 may include a first diffraction grating 76 and a second diffraction grating 78 .

The first diffraction gratings 76 may be disposed in the upper clad layer 40 . The first diffraction gratings 76 may be disposed in the upper clad layer 40 of the distribution region D. The first diffraction gratings 76 may be spaced apart from the optical waveguide 30 in a direction perpendicular to the substrate 10 . The first diffraction gratings 76 may include P-type indium phosphorus (InP), indium gallium arsenide (InGaAs), or a cavity. The patterns of the first diffraction gratings 76 may be arranged in the same direction as the direction in which the optical waveguide 30 extends.

The second diffraction gratings 78 may be disposed in the lower clad layer 20 . The second diffraction gratings 78 may be disposed in the lower clad layer 20 of the distribution region D. As shown in FIG. The second diffraction gratings 78 may be spaced apart from the optical waveguide 30 in a direction perpendicular to the substrate 10 . The second diffraction gratings 78 may include P-type indium phosphorus (InP), indium gallium arsenide (InGaAs), or a cavity. The patterns of the second diffraction gratings 78 may be arranged in the same direction as the direction in which the optical waveguide 30 extends.

The period of the first diffraction gratings 76 and the period of the second diffraction gratings 78 may be different from each other. For example, like the first grating patterns 72 and the second grating patterns 74 described with reference to FIG. 3 , the first diffraction gratings 76 have a first length L1, They may be arranged at intervals of one (S1). The second diffraction gratings 78 may have a second length L2 and may be arranged at a second interval S2 . In this case, the second length L2 may be longer than the first length L1 , and the second interval S2 may be longer than the first interval S1 .

According to the period of the first and second diffraction gratings 76 and 78 , the total reflection spectrum reflected by the optical waveguide 30 may be adjusted. As the first and second diffraction gratings 76 and 78 having different periods are disposed above and below the optical waveguide 30, the total reflection spectrum reflected by the optical waveguide 30 is shown in FIGS. 1 to 3 . It may be the same/similar to the diffraction gratings 70 described above.

In the above, embodiments of the present invention have been described with reference to the accompanying drawings, but those of ordinary skill in the art to which the present invention pertains can practice the present invention in other specific forms without changing its technical spirit or essential features. You can understand that there is Therefore, it should be understood that the embodiments described above are illustrative in all respects and not restrictive.

10: substrate 20: lower clad layer
30: optical waveguide 40: upper clad layer
52, 54, 56: electrodes 62, 64: anti-reflective coating layer
70, 76, 78: diffraction grating

Claims (10)

a substrate having a gain region, a phase adjustment region, and a distribution region;
a lower clad layer disposed on the substrate;
an optical waveguide disposed on the lower clad layer and extending from the distribution region to the gain region;
an upper clad layer disposed on the optical waveguide;
diffraction gratings provided in either the lower clad layer or the upper clad layer on the distribution area and adjacent to the optical waveguide; and
and first to third electrodes respectively disposed on the upper clad layer of the distribution region, the phase adjustment region, and the gain region,
the diffraction gratings are arranged in a first direction parallel to the substrate and the optical waveguide;
The arrangement pattern of the diffraction gratings is the same as that of overlapping a first grating pattern having a first length and a first interval in the first direction and a second grating pattern having a second length and a second interval in the first direction, and ,
The second length of the second grid pattern is longer than the first length of the first grid pattern,
The second interval of the second grating pattern is longer than the first interval of the first grating pattern.
delete a substrate having a gain region, a phase adjustment region, and a distribution region;
a lower clad layer disposed on the substrate;
an optical waveguide disposed on the lower clad layer and extending from the distribution region to the gain region;
an upper clad layer disposed on the optical waveguide;
diffraction gratings provided in either the lower clad layer or the upper clad layer on the distribution area and adjacent to the optical waveguide; and
and first to third electrodes respectively disposed on the upper clad layer of the distribution region, the phase adjustment region, and the gain region,
the diffraction gratings are arranged in a first direction parallel to the substrate and the optical waveguide;
The arrangement pattern of the diffraction gratings is the same as that of overlapping a first grating pattern having a first length and a first interval in the first direction and a second grating pattern having a second length and a second interval in the first direction, and ,
A length of the arrangement pattern of the diffraction gratings is longer than the second length and is periodically changed within a range shorter than the sum of twice the first length and the second length. The method of claim 1,
The reflection spectrum of the diffraction gratings is the same as the sum of the reflection spectrum of the first grating pattern and the reflection spectrum of the second grating pattern. The method of claim 1,
wherein the first grating pattern and the second grating pattern are disposed in the lower clad layer on the distribution region. The method of claim 1,
the first lattice pattern is disposed in the lower clad layer on the distribution area;
The second grating pattern is a tunable laser device disposed in the upper cladding layer on the distribution region. The method of claim 1,
The tunable laser device further comprising anti-reflection coating layers respectively disposed at both ends of the optical waveguide in the first direction. a substrate having a gain region, a phase adjustment region, and a distribution region;
a lower clad layer disposed on the substrate;
first diffraction gratings disposed in the lower clad layer on the distribution region;
an optical waveguide disposed on the lower clad layer and extending from the distribution region to the gain region;
an upper clad layer disposed on the optical waveguide;
second diffraction gratings disposed in the upper clad layer on the distribution region; and
and first to third electrodes respectively disposed on the upper clad layer of the distribution region, the phase adjustment region, and the gain region,
the first and second diffraction gratings are arranged in a first direction parallel to the substrate and the optical waveguide;
the first diffraction gratings have a first length and are arranged at a first spacing;
the second diffraction gratings have a second length different from the first length and are arranged at a second spacing different from the first spacing;
the second length of the second diffraction gratings is longer than the first length of the first diffraction gratings;
The second spacing of the second diffraction gratings is longer than the first spacing of the first diffraction gratings.
delete 9. The method of claim 8,
The tunable laser device further comprising anti-reflection coating layers respectively disposed at both ends of the optical waveguide in the first direction.

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