High-power single-mode distributed feedback laser

Abstract

The invention discloses a high-power single-mode distributed feedback laser which comprises a ridge waveguide, and the ridge waveguide has at least two different ridge widths in the length direction of the ridge waveguide. And the ridge width of at least one of the two end faces of the ridge waveguide is the narrowest ridge width of the ridge waveguide. The optical power is improved through the wide waveguide part formed by locally widening the ridge waveguide, and the high-order mode generated by the wide waveguide part is suppressed through the narrow waveguide part of the ridge waveguide, so that the laser emits light in a fundamental mode, and the single-mode performance is ensured.

Description

Technical Field

[0001] The present invention belongs to the technical field of lasers, and more specifically, relates to a high-power single-mode distributed feedback laser. Background Art

[0002] Semiconductor lasers have the advantages of small size, long life, and can be pumped by simple injection current, making them the most practical and important type of lasers. Among them, narrow linewidth single-mode laser sources have extensive applications in fields such as optical fiber communication, free-space optical communication, radio over fiber (RoF), sensing (such as lidar), and spectroscopy. Distributed Feedback Laser (abbreviated as DFB laser) is a main narrow linewidth single-mode laser source, which mainly relies on longitudinal single-mode waveguide confinement and Bragg grating feedback in the cavity to achieve mode selection and narrow linewidth output. Whether it can operate in a single longitudinal mode and whether it has a high side mode suppression ratio (SMSR) are the key performance indicators of DFB lasers.

[0003] In recent years, with the rise of radio over fiber, autonomous driving, and free-space optical communication technologies, the market demand for high-power narrow linewidth single-mode DFB lasers has been increasing. Generally speaking, increasing the cavity length of a DFB laser can increase its output power; however, the output power of a DFB laser cannot increase infinitely with the increase of the cavity length, and DFB lasers with long cavity lengths have problems such as multimode lasing and spatial hole burning effect. Increasing the longitudinal area of a DFB laser can increase the volume of the active region, thereby increasing its output power; however, the increase in the longitudinal area will cause the emergence of higher-order modes of the waveguide, destroying the single-mode property of the DFB laser. Summary of the Invention

[0004] The technical problem solved by the present invention is: how to balance the single-mode property and high power of DFB lasers.

[0005] The present application discloses a high-power single-mode distributed feedback laser, which includes a ridge waveguide. Along the length direction of the ridge waveguide, the ridge waveguide has at least two different ridge widths, and at least one of the two end faces of the ridge waveguide has the narrowest ridge width of the ridge waveguide.

[0006] Optionally, the ridge widths of the two end faces are the same, and along the direction from the end face to the middle of the ridge waveguide, the ridge width of the ridge waveguide changes from narrow to wide.

[0007] Optionally, the ridge waveguide includes at least three sub-ridge waveguides, and the ridge width of the sub-ridge waveguide located in the middle is greater than that of other sub-ridge waveguides.

[0008] Optionally, the length of the sub-ridge waveguide located in the middle is greater than the lengths of the other sub-ridge waveguides.

[0009] Optionally, the ridge widths of the two end faces are different, and in the direction from one end face to the other end face, the ridge width of the ridge waveguide varies from narrow to wide.

[0010] Optionally, the ridge waveguide includes at least two segments of sub-ridge waveguides.

[0011] Optionally, the lengths of the segments of the sub-ridge waveguides increase in the direction where the ridge width of the ridge waveguide varies from narrow to wide.

[0012] Optionally, the high-power single-mode distributed feedback laser includes a substrate layer, a buffer layer, a lower confinement layer, a quantum well layer, an upper confinement layer, a first cladding layer, a grating layer, a second cladding layer, and an ohmic contact layer stacked in sequence. Among them, a convex strip is formed after partial etching of the second cladding layer, and the ohmic contact layer is located on the convex strip. The ohmic contact layer and the convex strip constitute the ridge waveguide.

[0013] Optionally, the ridge depth at each position of the ridge waveguide is equal.

[0014] A high-power single-mode distributed feedback laser disclosed by the present invention has the following technical effects:

[0015] By using the wide waveguide part formed by locally widening the ridge waveguide to increase the optical power, and using the narrow waveguide part of the ridge waveguide to suppress the high-order modes generated by the wide waveguide part, the laser emits light in the fundamental mode, ensuring the single-mode property. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is the first three-dimensional structure diagram of the high-power single-mode distributed feedback laser of Embodiment 1 of the present invention;

[0017] Figure 2 It is the second three-dimensional structure diagram of the high-power single-mode distributed feedback laser of Embodiment 1 of the present invention;

[0018] Figure 3 It is the third three-dimensional structure diagram of the high-power single-mode distributed feedback laser of Embodiment 1 of the present invention;

[0019] Figure 4 It is the fourth three-dimensional structure diagram of the high-power single-mode distributed feedback laser of Embodiment 1 of the present invention.

[0020] The corresponding relationship between the reference numerals and the component names is as follows:

[0021] 10 - Substrate layer, 20 - Buffer layer, 30 - Lower confinement layer, 40 - Quantum well layer, 50 - Upper confinement layer, 60 - First cladding layer, 70 - Grating layer, 80 - Second cladding layer, 81 - Ridge, 90 - Ohmic contact layer, 100 - Ridge waveguide, 101 - End face, 110 - First sub - ridge waveguide, 120 - Second sub - ridge waveguide, 130 - Third sub - ridge waveguide, 140 - Fourth sub - ridge waveguide, 150 - Fifth sub - ridge waveguide, w - Ridge width, d - Ridge depth. Detailed implementation manners

[0022] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0023] Before describing each embodiment of the present application in detail, the technical concept of the present application will be briefly described first: In order to improve the optical power of the current DFB laser, it can be achieved by increasing the cavity length and the longitudinal area. The former will cause problems such as multimode lasing and spatial hole - burning effect, and the latter will cause the appearance of high - order modes and destroy the single - mode property. Therefore, the high - power single - mode distributed feedback laser provided by the present application, based on the principle of locally widening the ridge waveguide width, increases the optical power through the wider middle region of the ridge waveguide, and at the same time suppresses the high - order modes that appear due to local widening through the narrower end regions of the ridge waveguide, ensuring the single - mode property of the laser, thus taking into account both the single - mode property and high - power performance of the DFB laser. The specific principle of the high - power single - mode distributed feedback laser of the present application will be described below with more embodiments.

[0024] Specifically, as Figure 1 shown, a high - power single - mode distributed feedback laser in this embodiment includes a ridge waveguide 100. Along the length direction of the ridge waveguide 100, the ridge waveguide 100 has at least two different ridge widths w, and the ridge width w of at least one of the two end faces of the ridge waveguide 100 is the narrowest ridge width of the ridge waveguide 100. By setting the ridge widths at different positions of the ridge waveguide 100 to be different, a part of the ridge waveguide 100 becomes a wide waveguide and another part becomes a narrow waveguide. The wide waveguide can improve the optical power, and the narrow waveguide can suppress high - order modes, so as to ensure the output in the fundamental mode. It should be noted that the ridge width w is the horizontal width of the ridge waveguide 100 in the direction perpendicular to the length direction, and the ridge depth d is the vertical depth of the ridge waveguide 100 in the direction perpendicular to the length direction.

[0025] Furthermore, the principle of the high-power single-mode distributed feedback laser in the first embodiment to balance the optical power and single-mode property by locally widening the ridge waveguide is as follows: In the wide waveguide part of the ridge waveguide 100, since the control area of the laser for the active region is increased, the optical power of the laser can be improved, and the fundamental mode TE0, higher-order modes TE1, TE2, TE3, ······ can be excited. In the narrow waveguide part of the ridge waveguide 100, since the control area of the laser for the active region is small, only the fundamental mode TE0 can be excited. From the perspective of the resonator of the entire laser, the amplification lengths of the higher-order modes TE1, TE2, TE3, ······ are the length of the wide waveguide, while the amplification length of the fundamental mode TE0 is the sum of the length of the wide waveguide and the length of the narrow waveguide, that is, the amplification length of the fundamental mode TE0 is the length of the ridge waveguide 100. Therefore, the gain coefficient of the fundamental mode TE0 is higher than that of the higher-order modes. Finally, only the fundamental mode TE0 is excited, while the higher-order modes TE1, TE2, TE3, ······ are suppressed, thus ensuring the single-mode property of the laser output.

[0026] Exemplarily, the high-power single-mode distributed feedback laser includes a substrate layer 10, a buffer layer 20, a lower confinement layer 30, a quantum well layer 40, an upper confinement layer 50, a first cladding layer 60, a grating layer 70, a second cladding layer 80, and an ohmic contact layer 90 stacked in sequence from bottom to top. Among them, a convex strip 81 is formed after locally etching the second cladding layer 80, and the ohmic contact layer 90 is located on the convex strip 81. The ohmic contact layer 90 and the convex strip 81 constitute the ridge waveguide 100.

[0027] As an implementation manner, the substrate layer 10 is an n-InP substrate with a thickness of 350 μm, the doping atom is Si, and the doping concentration is 3.0×10 18 cm -3 . The buffer layer 20 is an n-InP buffer layer with a thickness of 1500 nm, the doping atom is Si, and the doping concentration is 1.0×10 18 cm -3 . The lower confinement layer 30 is a multi-layer structure, which is an undoped InGaAsP layer with a bandgap wavelength of 900 nm, an undoped InGaAsP layer with a bandgap wavelength of 1050 nm, and an undoped InGaAsP layer with a bandgap wavelength of 1200 nm from bottom to top, and the thickness of each layer is 20 nm. The quantum well layer 40 is a pair, the well layer is a 1.2% compressively strained InGaAlAs, and the barrier layer is a 0.3% tensile strained InGaAlAs quantum well, and the lasing wavelength is 1520 nm. The upper confinement layer 50 is a multi-layer structure, which is an undoped InGaAsP with a bandgap wavelength of 1200 nm, an undoped InGaAsP with a bandgap wavelength of 1050 nm, and an undoped InGaAsP with a bandgap wavelength of 900 nm from bottom to top, and the thickness of each layer is 20 nm. The first cladding layer 60 is a layer with a thickness of 100 nm, the doping atom is Zn, and the doping concentration is 1.0×1017 cm -3 InP of -3 . The grating layer 70 is InP buried with a doping concentration of 1×10 17 cm -3 、InGaAsP with a bandgap wavelength of 1150 nm, and the grating period corresponds to the first Bragg length. The second cladding layer 80 is an InP layer with a thickness of 1800 nm, and the doping atoms are Zn, and the doping concentration varies from 1.0×10 17 cm -3 gradually to 2.0×10 18 cm -3 。The ohmic contact layer 90 is InGaAs with doping atoms of Zn and a doping concentration of 1.0×10 19 cm -3 and a thickness of 200 nm.

[0028] In one embodiment, the ridge widths of the two end faces 101 are the same. In the direction from the end face 101 to the middle of the ridge waveguide 100, the ridge width w of the ridge waveguide 100 changes from narrow to wide. In this embodiment, the shape of the ridge waveguide 100 is wide in the middle and narrow at both ends.

[0029] Exemplarily, the ridge waveguide 100 includes at least three sub-ridge waveguides, and the ridge width of the sub-ridge waveguide located in the middle is greater than that of other sub-ridge waveguides. As Figure 1 shown, the ridge waveguide 100 includes a first sub-ridge waveguide 110, a second sub-ridge waveguide 120, and a third sub-ridge waveguide 130. The second sub-ridge waveguide 120 is located in the middle, that is, the second sub-ridge waveguide 120 is located between the first sub-ridge waveguide 110 and the third sub-ridge waveguide 130, and the ridge width w of the second sub-ridge waveguide 120 is greater than the ridge widths w of the first sub-ridge waveguide 110 and the third sub-ridge waveguide 130. Among them, the projection of the second sub-ridge waveguide 120 on the horizontal plane is a rectangle, and the ridge width w at each position of the second sub-ridge waveguide 120 is the same. The projections of the first sub-ridge waveguide 110 and the third sub-ridge waveguide 130 on the horizontal plane are trapezoids, and the ridge widths w of the first sub-ridge waveguide 110 and the third sub-ridge waveguide 130 increase along the direction from the end face 101 to the second sub-ridge waveguide 120. At this time, the second sub-ridge waveguide 120 is a wide waveguide for enhancing the optical power, and the first sub-ridge waveguide 110 and the third sub-ridge waveguide 130 are narrow waveguides for suppressing the high-order modes generated by the wide waveguide, so that the laser emits in the fundamental mode, taking into account both the optical power and the single-mode property.

[0030] In another example, as Figure 2As shown, the ridge waveguide 100 includes five sub-ridge waveguides, namely the first sub-ridge waveguide 110, the second sub-ridge waveguide 120, the third sub-ridge waveguide 130, the fourth sub-ridge waveguide 140, and the fifth sub-ridge waveguide 150 arranged along the length direction. The third sub-ridge waveguide 130 is located in the middle of the ridge waveguide 100. The projection of the third sub-ridge waveguide 130 on the horizontal plane is rectangular and the ridge width of the third sub-ridge waveguide 130 is the widest ridge width of the ridge waveguide 100. The projections of the second sub-ridge waveguide 120 and the fourth sub-ridge waveguide 140 on the horizontal plane are trapezoidal, and the projections of the first sub-ridge waveguide 110 and the fifth sub-ridge waveguide 150 on the horizontal plane are rectangular, and the ridge widths of the first sub-ridge waveguide 110 and the fifth sub-ridge waveguide 150 are the narrowest ridge widths of the ridge waveguide 100.

[0031] Further, the length of the sub-ridge waveguide in the middle is greater than the lengths of other sub-ridge waveguides. The sub-ridge waveguide in the middle is a wide waveguide, and the sub-ridge waveguides on both sides are narrow waveguides. Without changing the length of the ridge waveguide 100, by increasing the length of the wide waveguide, the optical power can be further increased. Exemplarily, for the above five-section sub-ridge waveguide case, the total length of the ridge waveguide 100 is 1500 μm, the lengths of the first sub-ridge waveguide 110 and the fifth sub-ridge waveguide 150 are 150 μm and the ridge width is 1.8 μm, the lengths of the second sub-ridge waveguide 120 and the fourth sub-ridge waveguide 140 are 250 μm, and the length of the third sub-ridge waveguide 130 is 700 μm and the ridge width is 4.2 μm. Further, the ridge depth d at each position of the ridge waveguide 100 is equal. Exemplarily, the thickness of the ridge waveguide 100 is set to 1750 nm.

[0032] In another embodiment, the ridge widths of the two end faces 101 are different. Along the direction from one end face 101 to the other end face 101, the ridge width w of the ridge waveguide 100 changes from narrow to wide. The shape of the ridge waveguide 100 in this embodiment is wide at one end and narrow at the other end.

[0033] Exemplarily, the ridge waveguide 100 includes at least two sub-ridge waveguides. As Figure 3 shown, the ridge waveguide 100 includes the first sub-ridge waveguide 110 and the second sub-ridge waveguide 120. The ridge width w of the first sub-ridge waveguide 110 is less than the ridge width w of the second sub-ridge waveguide 120. Among them, the projection of the first sub-ridge waveguide 110 on the horizontal plane is trapezoidal, and the ridge width w of the first sub-ridge waveguide 110 increases along the direction from the end face 101 to the second sub-ridge waveguide 120. The projection of the second sub-ridge waveguide 120 on the horizontal plane is rectangular, and the ridge width w at each position of the second sub-ridge waveguide 120 is the same.

[0034] In another example, as Figure 4As shown, the ridge waveguide 100 includes three sub-ridge waveguides, namely a first sub-ridge waveguide 110, a second sub-ridge waveguide 120, and a third sub-ridge waveguide 130 that are arranged along the length direction and have gradually increasing ridge widths. The projection of the first sub-ridge waveguide 110 on the horizontal plane is trapezoidal. The ridge width w of the second sub-ridge waveguide 110 increases in the direction from the second sub-ridge waveguide 120 to the third sub-ridge waveguide 130. The projection of the third sub-ridge waveguide 130 on the horizontal plane is rectangular, and the ridge width w at each position of the third sub-ridge waveguide 130 is the same.

[0035] Furthermore, the length of each sub-ridge waveguide increases in the direction where the ridge width of the ridge waveguide changes from narrow to wide. That is, in each sub-ridge waveguide, the wider the ridge width of the sub-ridge waveguide, the longer the length of the sub-ridge waveguide. In other words, the length of the wide waveguide is greater than the length of the narrow waveguide. When the length of the ridge waveguide 100 remains unchanged, the optical power can be further increased by increasing the length of the wide waveguide.

[0036] The high-power single-mode distributed feedback laser disclosed in this embodiment improves the optical power through the wide waveguide part formed by locally widening the ridge waveguide, and suppresses the high-order modes generated in the wide waveguide part through the narrow waveguide part of the ridge waveguide, enabling the laser to emit light in the fundamental mode and ensuring single-mode performance.

[0037] The specific embodiments of the present invention have been described in detail above. Although some embodiments have been shown and described, those skilled in the art should understand that these embodiments can be modified and perfected without departing from the principles and spirit of the present invention defined by the claims and their equivalents, and these modifications and improvements should also be within the protection scope of the present invention.

Claims

1. A high-power single-mode distributed feedback laser, characterized in that, The high-power single-mode distributed feedback laser includes a ridge waveguide, which has at least two different ridge widths in the length direction of the ridge waveguide, and the ridge width of at least one end face of the two end faces of the ridge waveguide is the narrowest ridge width of the ridge waveguide.

2. The high-power single-mode distributed feedback laser according to claim 1, characterized in that, The ridge widths of the two end faces are the same, and in the direction from the end face to the middle of the ridge waveguide, the ridge width of the ridge waveguide changes from narrow to wide.

3. The high-power single-mode distributed feedback laser according to claim 2, wherein The ridge waveguide includes at least three sub-ridge waveguides, and the ridge width of the sub-ridge waveguide located in the middle is greater than that of the other sub-ridge waveguides.

4. The high-power single-mode distributed feedback laser according to claim 3, characterized in that, The length of the sub-ridge waveguide located in the middle is greater than that of the other sub-ridge waveguides.

5. The high-power single-mode distributed feedback laser according to claim 1, wherein The ridge widths of the two end faces are different, and in the direction from one end face to the other end face, the ridge width of the ridge waveguide changes from narrow to wide.

6. The high-power single-mode distributed feedback laser according to claim 5, characterized in that, The ridge waveguide includes at least two sub-ridge waveguides.

7. The high-power single-mode distributed feedback laser according to claim 6, characterized in that, The length of each sub-ridge waveguide increases in the direction where the ridge width of the ridge waveguide changes from narrow to wide.

8. The high-power single-mode distributed feedback laser according to any one of claims 1 to 7, characterized in that The high-power single-mode distributed feedback laser includes a substrate layer, a buffer layer, a lower confinement layer, a quantum well layer, an upper confinement layer, a first cladding layer, a grating layer, a second cladding layer, and an ohmic contact layer stacked in sequence. Among them, after partial etching of the second cladding layer, a raised strip is formed, and the ohmic contact layer is located on the raised strip. The ohmic contact layer and the raised strip constitute a ridge waveguide.

9. The high-power single-mode distributed feedback laser according to claim 8, wherein, The ridge depth at each position of the ridge waveguide is equal.

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