DFB laser and laser system with same

Abstract

The utility model discloses a DFB laser and a laser system having the same, the DFB laser comprises a grating layer, the grating layer comprises a grating waveguide and a sampling grating, the sampling grating is formed in the grating waveguide, the sampling grating is an antisymmetric Bragg grating so as to enable the grating layer to support TE0 and TE1 mode transmission, teeth of the sampling grating extend along a first direction, and teeth of the sampling grating extend along a second direction; the first direction is perpendicular to the propagation direction of the laser; the ridge waveguide is arranged on one side of the grating layer in the thickness direction, in the laser propagation direction, the portion, located on the downstream portion of the sampling grating, of the ridge waveguide is a first waveguide section, and the size of at least part of the first waveguide section in the first direction is gradually reduced, so that the TE1 mode is filtered out by the first waveguide section. According to the DFB laser provided by the utility model, the sampling grating of the antisymmetric Bragg grating is arranged, so that mixed resonance of two transverse modes can be realized under the same reflection wavelength of laser, and the Lorentz linetype of a spectrum can be effectively broadened through mutual competition and coupling of the two modes.

Description

Technical Field

[0001] The utility model relates to the technical field of lasers, in particular to a DFB laser and a laser system having the same. Background Art

[0002] When the linewidth of the laser becomes wider, the laser can carry more information, increase the data transmission rate and reduce dispersion. In some laser systems equipped with DFB lasers, the linewidth of the DFB laser needs to be widened to meet usage needs. Utility Model Content

[0003] The present invention aims to solve at least one of the technical problems in the prior art. To this end, the present invention provides a DFB laser, which has a wider laser line width.

[0004] The utility model also provides a laser system having the above-mentioned DFB laser.

[0005] According to the first aspect of the present invention, a DFB laser comprises: a grating layer, the grating layer comprising a grating waveguide and a sampled grating, the sampled grating being formed in the grating waveguide, the sampled grating being an antisymmetric Bragg grating such that the grating layer supports TE0 and TE1 mode transmission, the teeth of the sampled grating extending along a first direction, the first direction being perpendicular to the propagation direction of the laser light; and a ridge waveguide, the ridge waveguide being provided on one side of the grating layer in a thickness direction, the portion of the ridge waveguide located downstream of the sampled grating in the propagation direction of the laser light being a first waveguide segment, the dimension of at least a portion of the first waveguide segment gradually decreasing in the first direction such that the first waveguide segment filters out the TE1 mode.

[0006] According to the DFB laser of the first aspect of the present invention, by providing a sampled grating of an antisymmetric Bragg grating, the laser can achieve hybrid resonance of two transverse modes at the same reflection wavelength. The competition and coupling between the two modes can effectively broaden the Lorentzian line shape of the spectrum, thereby widening the linewidth of the DFB laser. By gradually reducing the size of at least a portion of the first waveguide segment in the first direction, the stability of the laser output can be improved while ensuring the DFB laser outputs single transverse and vertical modes.

[0007] According to some embodiments of the present invention, the first waveguide segment includes: a gradient segment and a constant diameter segment, the constant diameter segment is connected to an end of the gradient segment away from the sampling grating, and in the propagation direction of the laser, the size of the gradient segment in the first direction gradually decreases.

[0008] According to some embodiments of the present invention, in the first direction, the size of the portion of the ridge waveguide and the sampled grating opposite to each other in the thickness direction of the grating layer is 4.5um or 5um, the size of the gradient section toward one end of the sampled grating is 4.5um or 5um, and the size of the gradient section away from one end of the sampled grating is greater than or equal to 2um and less than 2.5um.

[0009] According to some embodiments of the present invention, in the propagation direction of the laser, the size of the equal-diameter segment is greater than or equal to 6 um and less than 15 um.

[0010] According to some embodiments of the present invention, in the propagation direction of the laser, the portion of the ridge waveguide located upstream of the sampling grating is a second waveguide segment, and on a projection plane perpendicular to the propagation direction of the laser, the projection portions at both ends of the second waveguide segment overlap.

[0011] According to some embodiments of the present invention, in the propagation direction of the laser, the second waveguide segment extends obliquely toward the sampled grating.

[0012] According to some embodiments of the present invention, in the propagation direction of the laser, the second waveguide segment extends along an arc line.

[0013] According to some embodiments of the present invention, the DFB laser further comprises: a substrate and an active region, the active region being disposed on a side of the grating layer away from the ridge waveguide, the active region being connected between the substrate and the grating layer, the side of the substrate away from the active region and the side of the ridge waveguide away from the grating layer being both coated with a gold layer; and / or the DFB laser is coated with an anti-reflection coating at both ends of the laser light path in the extension direction.

[0014] A laser system according to a second aspect of the present invention includes: the DFB laser according to the first aspect of the present invention.

[0015] According to the laser system of the second aspect of the present invention, by providing the DFB laser according to the first aspect of the present invention, the use requirements can be met and the performance of the laser system can be improved.

[0016] According to some embodiments of the present invention, the laser system is a fiber optic gyroscope.

[0017] Additional aspects and advantages of the present invention will be given in part in the following description and will become apparent from the following description or learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a schematic diagram of a DFB laser according to an embodiment of the present utility model;

[0019] Figure 2 is a schematic diagram of a DFB laser according to another embodiment of the present utility model;

[0020] Figure 3 yes Figure 2 Schematic diagram of another angle of the DFB laser shown in .

[0021] Reference numerals:

[0022] 100. DFB laser;

[0023] 10. Grating layer; 11. Grating waveguide; 12. Sampled grating;

[0024] 20, ridge waveguide; 21, first waveguide segment; 211, gradient segment; 212, constant diameter segment; 22, second waveguide segment;

[0025] 30. substrate;

[0026] 40. Active region; 41. Lower confinement layer; 42. Quantum well; 43. Upper confinement layer;

[0027] 50. Gold layer;

[0028] 60. Anti-reflective coating. DETAILED DESCRIPTION

[0029] The following describes in detail embodiments of the present invention, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to explain the present invention, and should not be construed as limiting the present invention.

[0030] Reference below Figure 1-Figure 3 A DFB laser 100 (distributed feedback laser) according to an embodiment of the first aspect of the present invention will be described.

[0031] like Figure 1-Figure 3 As shown, the DFB laser 100 according to the embodiment of the first aspect of the present invention includes: a grating layer 10 and a ridge waveguide 20.

[0032] Specifically, the grating layer 10 includes a grating waveguide 11 and a sampled grating 12. The sampled grating 12 is formed in the grating waveguide 11. The sampled grating 12 is an antisymmetric Bragg grating so that the grating layer 10 supports TE0 and TE1 mode transmission. The teeth of the sampled grating 12 are along a first direction (e.g., Figure 1 The first direction extends in the front-to-back direction shown in FIG, and the first direction extends in the direction of propagation of the laser light (eg Figure 1The ridge waveguide 20 is perpendicular to the left and right directions shown in the figure, and is provided on one side of the grating layer 10 in the thickness direction. In the propagation direction of the laser, the portion of the ridge waveguide 20 located downstream of the sampled grating 12 is the first waveguide segment 21. The size of at least a portion of the first waveguide segment 21 gradually decreases in the first direction so that the first waveguide segment 21 filters out the TE1 mode.

[0033] That is, the size of a portion of the first waveguide segment 21 in the first direction may gradually decrease, or the size of the entire first waveguide segment 21 in the first direction may gradually decrease.

[0034] Among them, the downstream of the sampled grating 12 refers to the part through which the laser passes after passing through the sampled grating 12. The sampled grating 12 includes a first grating and a second grating connected in a first direction. The first direction is perpendicular to the propagation direction of the laser. The teeth of the first grating and the second grating extend along the first direction and have the same period. The teeth of the first grating and the teeth of the second grating are staggered in the propagation direction of the laser.

[0035] During the operation of the DFB laser 100, the DFB laser 100 generates laser light by stimulated radiation, and the laser light resonates back and forth in the resonant cavity. The sampled grating 12 of the antisymmetric Bragg grating causes the laser light to undergo mixed resonance of two TE0 and TE1 transverse modes at the same reflection wavelength. The laser TE0 and TE1 modes compete with each other and couple to form transverse resonance. During the product design process, the length of the sampled grating 12 is controlled to control the phase, so that the competition of the resonant modes broadens the Lorentz line shape of the spectrum and the coherence of the spectrum meets the requirements of use.

[0036] After the laser passes through the sampled grating 12, in order to ensure the output of a single horizontal and vertical mode of the DFB laser 100, the TE1 mode needs to be filtered out. By gradually reducing the size of at least part of the first waveguide segment 21 in the first direction, the size of the first waveguide segment 21 at the downstream end only supports the TE0 mode. The structure of the first waveguide segment 21 does not produce a sudden change, which can improve the stability of the laser output.

[0037] According to the DFB laser 100 of the first embodiment of the present invention, by providing a sampled grating 12 of an antisymmetric Bragg grating, the laser can achieve hybrid resonance of two transverse modes at the same reflection wavelength. The competition and coupling between the two modes can effectively broaden the Lorentzian line shape of the spectrum, thereby widening the linewidth of the DFB laser 100. By gradually reducing the size of at least a portion of the first waveguide segment 21 in the first direction, the stability of the laser output can be improved while ensuring that the DFB laser 100 outputs a single transverse and vertical mode.

[0038] In some embodiments of the present invention, Figure 1 and Figure 2As shown, the first waveguide segment 21 includes a gradient segment 211 and a constant-diameter segment 212. The constant-diameter segment 212 is connected to the end of the gradient segment 211 away from the sampled grating 12. The gradient segment 211 gradually decreases in size in the first direction along the direction of laser propagation. This allows at least a portion of the first waveguide segment 211 to gradually decrease in size in the first direction. During laser transmission, the gradient segment 211 filters out the TE1 mode, while the TE0 mode is transmitted from the gradient segment 211 to the constant-diameter segment 212, then passes through the constant-diameter segment 212 and is output from the DFB laser 100. The constant-diameter segment 212 guides the laser light, further improving the stability of the laser output.

[0039] In some embodiments of the present invention, in the first direction, the portion of the ridge waveguide 20 that faces the sampled grating 12 in the thickness direction of the grating layer 10 has a size of 4.5 μm or 5 μm, the end of the gradient section 211 facing the sampled grating 12 has a size of 4.5 μm or 5 μm, and the end of the gradient section 211 away from the sampled grating 12 has a size greater than or equal to 2 μm and less than 2.5 μm. For example, the end of the gradient section 211 away from the sampled grating 12 can have a size of 2 μm, 2.1 μm, 2.2 μm, 2.3 μm, 2.4 μm, or 2.5 μm. This allows the ridge waveguide 20 upstream of the first waveguide segment 21 to pass both the TE0 and TE1 modes, while the end of the gradient section 211 away from the sampled grating 12 can filter out the TE1 mode. During product design, these parameters can be adjusted within the aforementioned ranges, thereby reducing product design difficulty.

[0040] In some embodiments of the present invention, the size of the equal-diameter segment 212 in the direction of laser propagation is greater than or equal to 6 μm and less than 15 μm. For example, the size of the equal-diameter segment 212 in the direction of laser propagation can be 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, or 15 μm. This allows the length of the resonant cavity to be moderate, allowing the line width to vary within the equal-diameter segment 212 to meet operational requirements. It is understood by those skilled in the art that the laser line width is inversely proportional to the square of the photon lifetime within the resonant cavity. Increasing the total length of the resonant cavity prolongs the photon lifetime within the cavity, thereby narrowing the spectral line width.

[0041] In some embodiments of the present invention, Figure 1 and Figure 2As shown, in the direction of laser propagation, the portion of the ridge waveguide 20 located upstream of the sampled grating 12 is the second waveguide segment 22. On a projection plane perpendicular to the direction of laser propagation, the projections of the second waveguide segment 22 at both ends overlap. This reduces reflections from the end facets of the DFB laser 100, minimizing the impact of random phases generated by end facet reflections on the longitudinal modes during mode competition and improving the stability of the DFB laser 100.

[0042] In some embodiments of the present invention, Figure 1 As shown, in the propagation direction of the laser, the second waveguide segment 22 extends obliquely toward the sampled grating 12. In this way, the laser propagates more smoothly in the second waveguide segment 22, which can further improve the stability of the DFB laser 100.

[0043] In some embodiments of the present invention, Figure 1 As shown, in the propagation direction of the laser, the second waveguide segment 22 extends along an arc line. This can further improve the smoothness of the laser propagation in the second waveguide segment 22, thereby further improving the stability of the DFB laser 100.

[0044] In some embodiments of the present invention, Figure 1-Figure 3 As shown, the DFB laser 100 further includes: a substrate 30 and an active region 40. The active region 40 is provided on a side of the grating layer 10 away from the ridge waveguide 20. The active region 40 is connected between the substrate 30 and the grating layer 10. The side of the substrate 30 away from the active region 40 and the side of the ridge waveguide 20 away from the grating layer 10 are both coated with a gold layer 50.

[0045] Among them, the active area 40 includes a stacked lower confinement layer 41, a quantum well 42 and an upper confinement layer 43. The lower confinement layer 41 is connected to the substrate 30, and the upper confinement layer 43 is connected to the grating layer 10. In the active area 40, a large number of electrons jump from the top of the valence band to the bottom of the conduction band, forming an inversion of the number of particles at the upper and lower energy levels, and forming a laser through the resonance of the sampling grating 12 and the reflecting surfaces at both ends.

[0046] Preferably, the substrate 30 is an InP (indium phosphide) substrate 30, and the height of the substrate 30 is 100um-120um. For example, the height of the substrate 30 can be 100um, 102um, 108um, 114um, 119um or 120um. Thus, the band gap width of the substrate 30 can meet the wavelength required for optical communication. The lower limiting layer 41 is an InGaAsP (indium gallium arsenic phosphide) material layer, the quantum well 42 is an AlGaAsP (aluminum gallium arsenic phosphide) material, and the upper limiting layer 43 is an InGaAsP (indium gallium arsenic phosphide) material layer.

[0047] The gold layer 50 can act as a metal strip to absorb or attenuate radiation leakage that may be generated during propagation in the waveguide in the TE0 mode, thereby improving the transmission efficiency of the waveguide, reducing energy loss, and improving the overall performance of the DFB laser 100.

[0048] During the production of the DFB laser 100, all grating structures are equivalently realized using a sampled grating 12 method. After sequentially fabricating the gold layer 50, substrate 30, and active region 40 in a single epitaxial growth process, a zero-order grating is fabricated by holographic exposure on the surface of the active region 40. A secondary epitaxial growth is then performed using a lithography machine using mask error correction technology, integrating a first-order grating within the DFB laser 100. After holographic exposure and photolithography, a seed grating with a period a is fabricated. This seed grating is then subjected to secondary photolithography to create a sampled grating 12 with a period b. During product design, by designing the two periods a and b and superimposing their Fourier transforms, micron-scale photolithography can be used to achieve nanometer-scale electron beam lithography results. Preferably, a is 256.8 nm and b is 4.191 nm.

[0049] In some embodiments of the present invention, Figure 1 and Figure 2 As shown, the DFB laser 100 is coated with an anti-reflection coating 60 at both ends of the laser light path. This further reduces reflections from the end faces of the DFB laser 100, reduces the impact of random phases generated by end face reflections on the longitudinal modes during mode competition, and improves the stability of the DFB laser 100.

[0050] During the production process of the DFB laser 100, the substrate 30, active region 40, gold layer 50, grating layer 10, ridge waveguide 20 and anti-reflection coating 60 can be produced on the same wafer through epitaxy and photolithography. On the one hand, this can reduce waveguide loss, and on the other hand, the degree of integration is higher, which can reduce production costs.

[0051] The laser system according to the second aspect of the present invention includes: the DFB laser 100 according to the embodiment of the first aspect of the present invention.

[0052] For example, the laser system can be an optical guidance system, a spectrum analyzer, an optical computing chip, or a fiber optic gyroscope.

[0053] Optical guidance systems can be used in missile guidance or drone navigation. Wider linewidth can provide better anti-interference ability and flexibility. Optical guidance systems can also be used in industrial measurement, robot positioning, etc. Linewidth-widened lasers can provide a wider spectral range, thereby increasing measurement accuracy and stability.

[0054] When using an optical spectrum analyzer in environments such as material composition detection, chemical reaction monitoring, environmental monitoring, or industrial monitoring, a wider linewidth can improve sensitivity and measurement range.

[0055] The wider linewidth of optical computing chips can effectively eliminate phase sensitivity and reduce the difficulty of large-scale development of optical computing chips.

[0056] Wider linewidth in fiber optic gyroscopes can reduce noise and drift, improve scale factor stability, and reduce cost.

[0057] The laser system according to the second aspect of the present invention can meet the use requirements and improve the performance of the laser system by providing the DFB laser 100 according to the first aspect of the present invention.

[0058] In some embodiments of the present invention, the laser system is a fiber optic gyroscope.

[0059] In fiber optic gyroscopes, the optical fiber used for optical signal transmission and Sagnac effect detection is often several kilometers long, placing stringent demands on the output power of the light source. Fiber optic gyroscopes use SLEDs (superluminescent diodes) as their light source. SLEDs achieve light output through amplified spontaneous radiation, but the transition process of spontaneous radiation is a random process. The atoms spend very short periods of time in excited states, and the energy level they transition to is uncertain. Therefore, the radiation efficiency of spontaneous radiation is relatively low, with most of the energy dissipated as heat or other forms, and only a small portion of the energy being radiated as photons. Therefore, achieving very high power is difficult. In contrast, the DFB laser 100 (distributed feedback laser), leveraging its stimulated emission mechanism and enhanced reflection from the grating, can easily achieve high power output in the hundreds of milliwatts, effectively solving the power shortage problem faced by SLEDs.

[0060] Because SLEDs utilize an amplified spontaneous emission mechanism, their operating threshold is relatively high, typically around 50mA, and they require a relatively high current to achieve the desired power level. This significantly impacts the overall power consumption of the fiber optic gyroscope system. The DFB laser 100, however, effectively reduces system power consumption and improves energy efficiency thanks to its low threshold (down to below 10mA) and significantly lower current consumption while maintaining the same power requirements.

[0061] At the same time, by setting the sampled grating 12 as an antisymmetric Bragg grating, the line width of the DFB laser 100 can be increased, thereby meeting the use requirements of the fiber optic gyroscope.

[0062] In summary, by providing the DFB laser 100 , the performance of the fiber optic gyroscope can be improved.

[0063] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation to the present invention.

[0064] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature specified as "first" or "second" may explicitly or implicitly include one or more of such features. In the description of this utility model, "plurality" means two or more, unless otherwise specifically defined.

[0065] In this utility model, unless otherwise expressly specified or limited, the terms "installed," "connected," "connect," "fixed," etc. should be understood in a broad sense. For example, they can refer to fixed connection, detachable connection, or integration; mechanical connection, electrical connection, or communication; direct connection or indirect connection through an intermediate medium; internal communication between two components or interaction between two components. For those skilled in the art, the specific meanings of the above terms in this utility model can be understood according to specific circumstances.

[0066] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0067] Although the embodiments of the present invention have been shown and described, those skilled in the art will appreciate that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and purpose of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A DFB laser, characterized in that: include: a grating layer, the grating layer comprising a grating waveguide and a sampled grating, the sampled grating being formed in the grating waveguide, the sampled grating being an antisymmetric Bragg grating such that the grating layer supports TE0 and TE1 mode transmission, the teeth of the sampled grating extending along a first direction perpendicular to the propagation direction of the laser; A ridge waveguide is provided on one side of the grating layer in the thickness direction. In the propagation direction of the laser, the portion of the ridge waveguide located downstream of the sampled grating is a first waveguide segment. The size of at least a portion of the first waveguide segment in the first direction gradually decreases so that the first waveguide segment filters out the TE1 mode.

2. The DFB laser according to claim 1, characterized in that The first waveguide section includes a gradient section and a constant diameter section, wherein the constant diameter section is connected to an end of the gradient section away from the sampling grating. In the propagation direction of the laser, the size of the gradient section in the first direction gradually decreases.

3. The DFB laser according to claim 2, characterized in that In the first direction, the size of the portion of the ridge waveguide and the sampled grating opposite to each other in the thickness direction of the grating layer is 4.5um or 5um, the size of the gradient section toward one end of the sampled grating is 4.5um or 5um, and the size of the gradient section away from one end of the sampled grating is greater than or equal to 2um and less than 2.5um.

4. The laser according to claim 2, characterized in that In the propagation direction of the laser, the size of the equal-diameter segment is greater than or equal to 6 um and less than 15 um.

5. The DFB laser according to claim 2, characterized in that In the propagation direction of the laser, the portion of the ridge waveguide located upstream of the sampled grating is the second waveguide segment. On a projection plane perpendicular to the propagation direction of the laser, the projections of both ends of the second waveguide segment overlap.

6. The DFB laser according to claim 5, characterized in that In the propagation direction of the laser light, the second waveguide segment extends obliquely toward the sampled grating.

7. The DFB laser according to claim 6, characterized in that In the propagation direction of the laser, the second waveguide segment extends along an arc line.

8. The DFB laser according to claim 1, wherein Also includes: A substrate and an active region, wherein the active region is provided on a side of the grating layer away from the ridge waveguide, the active region is connected between the substrate and the grating layer, and the side of the substrate away from the active region and the side of the ridge waveguide away from the grating layer are both plated with a gold layer; and / or, both ends of the DFB laser in the direction of extension of the laser light path are plated with an anti-reflection coating.

9. A laser system, characterized in that: include: The DFB laser according to any one of claims 1 to 8.

10. The laser system according to claim 9, characterized in that The laser system is a fiber optic gyroscope.

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