Laser device and manufacturing method

Abstract

To provide a laser device having a higher modulation speed, a high device yield, and improved array compatibility under either cooled or uncooled operating conditions.SOLUTION: An active layer structure 20 between a semiconductor substrate 30 and a grating structure 40 configured for operation, comprising a common active layer, a first facet 50-1 and a second facet 50-2, wherein the grating structure comprises spatially adjacent integrated grating sections, a cladding structure 70 for optical confinement of laser light, a DFB structure 60-1 with a first grating section 42-1, and a DBR structure 60-2 with a second grating section 42-2, the first grating section and the second grating section share a common active layer for the integrated grating section, the DFB structure includes a first optical function as a lasing function, and the DBR structure includes a second DBR structure as an optical feedback.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This application relates to laser devices and methods for manufacturing the same, including but not exclusively, distributed feedback and distributed Bragg reflector lasers that share a common active layer. This application also relates to methods for generating laser light. [Background technology]

[0002] For optical data transmission in telecommunications systems, data centers or high-performance computing systems, high-speed transmitter components are required. High-speed distributed feedback (DFB) lasers, especially in the o-band wavelength range, are key components for these applications. Within the past decade, significant R&D efforts have been made to increase the modulation speed of DFB lasers by optimizing the InGaAlAs MQW active layer and DFB grating for high carrier-photon resonance (CPR), as well as by reducing the laser's series resistance and parasitic capacitance. In this way, DFB lasers with frequency bandwidths up to 30 GHz at room temperature have been achieved. However, recent advances have pushed the boundaries further, with some DFB lasers achieving frequency bandwidths of over 40 GHz [1.1], [1.2]. These advances have been made using traditional methods to improve CPR. One approach involves increasing the ratio between the optical confinement factor and the mode field diameter [1.1]. Another approach utilizes a membrane DFB with a buried sapphire layer on a silicon substrate [1.2].

[0003] Various industrial applications require bit rates exceeding 100 Gbps for data transmission. While existing electroabsorption modulated DFBs show good performance in 100 Gbps non-return-to-zero (NRZ) formats, they are not a cost-effective or energy-efficient solution. Therefore, alternative approaches are being explored to further increase the modulation bandwidth of directly modulated lasers (DMLs). One such technique is detuning, where the lasing mode is positioned at the longer wavelength side of the reflection spectrum [1.4], [1.7]. Another technique involves exploiting a second resonance, called photon-photon resonance (PPR), in addition to CPR to improve the laser's speed [1.3], [1.4], [1.5], [1.6], [1.7]. This requires a coupled-cavity laser structure with feedback. This technique not only offers the possibility of faster data transmission, but also allows for lower chirp modulation compared to EML. Several studies have demonstrated various coupled-cavity laser variants, including passive feedback lasers [1.3], double DFB [1.4], distributed reflector (DR) lasers [1.5], DFB+R lasers [1.6], and directly modulated membrane DFB lasers on SiC substrates [1.7]. To date, the highest speeds have been reported by [1.7], achieving over 110 GHz at 25 °C and 74 GHz at 85 °C using directly modulated membrane DFB lasers on SiC substrates. However, such membrane lasers suffer from very low optical output power, much lower than 1 mW, making them unusable for many applications.

[0004] Most of the variations reported so far involve a coating with a certain degree of reflectivity on at least one of the facets. Therefore, these variations suffer from very low device yields and are not suitable for array compatibility or mass production. So far, only [1.8] has demonstrated an array of two devices achieving 60 GHz modulation bandwidth in each channel. [1.8] used a film DML on SiO2 / Si with distributed Bragg reflector (DBR) gratings on both sides of the DFB. Here, a uniform grating DFB is used, and the rear-side DBR (DBR-r) ensures stable single-mode operation. The front-side DBR (DBR-f) selects longer wavelength modes and provides optical feedback, thus exploiting the properties of detuning loads and the PPR effect. The DBR grating in this design is realized using a butt-jointed, grown-on passive waveguide, which contributes to an arbitrary phase condition between the DFB and DBR. Therefore, even if reflective coatings on the facets are avoided, the possibility of a high-yield array is very limited due to the arbitrary phase between the gratings. Furthermore, a conventional DFB design featuring an additional active distributed reflector (ADR) with the same waveguide core as the DFB laser has been demonstrated [1.9]. In this configuration, the ADR effectively replaces the high-reflectivity (HR) coating on the back surface of the DFB. A modulation bandwidth of 24 GHz is achieved. However, the photon-photon resonance (PPR) effect is not utilized here.

[0005] Recently, [1.10] investigated a variant of the double DFB configuration in which the two DFBs are separated by a passive section grown via a butt-joint process. This device exploits the PPR effect and achieves speeds of up to 72 Gbps when cooled and 40 Gbps when uncooled. However, in this configuration, the grating does not have a fixed phase condition, and the yield of devices demonstrating the PPR effect was limited, even though the facets were coated with antireflection (AR) coatings. Summary of the Invention [Problem to be solved by the invention]

[0006] Therefore, there is a particular need to provide a laser device that has higher modulation speeds, high device yields, and improved array compatibility in either cooled or uncooled operating conditions. Such a need is met by a laser device according to independent claim 1 and a laser device according to independent claim 18, a method for manufacturing a laser device according to claim 19, and a method for generating laser light according to claim 20. Furthermore, specific embodiments of the inventive concept for the laser device according to independent claim 1 are defined in the dependent claims. [Means for solving the problem]

[0007] According to one embodiment, a laser device includes an active layer structure disposed between a semiconductor substrate and a lattice structure. The active layer structure includes a common active layer configured to generate laser light, and the lattice structure is configured to manipulate the generation. The laser device further includes a first facet disposed spatially adjacent to one end of the active layer structure and a second facet disposed spatially adjacent to the opposite end of the active layer structure. The first facet is configured to emit laser light. The first facet and the second facet include an anti-reflective coating. The lattice structure includes a plurality of integrally formed lattice sections disposed spatially adjacent to one another. The laser device further includes a cladding structure configured to optically confine the laser light. The cladding structure is adapted to be disposed between the active layer structure and the cladding structure. The laser device further includes a DFB structure having a first lattice section of the lattice structure. The laser device further includes at least one DBR structure having a second lattice section of the lattice structure. The first grating section and the second grating section share a common active layer that is common to at least a plurality of the integrally formed grating sections. The DFB structure includes a first associated optical function as a lasing function. At least one DBR structure includes a second associated optical function as optical feedback. Thus, laser devices of the present concepts employing multiple integrally formed grating sections have a predetermined or fixed phase condition when sharing a common active layer between them. The predetermined or fixed phase condition between the integrally formed grating sections across the common active layer is ensured by sequential or single grating writing using a single grating writing field. Thus, laser devices of the present concepts achieve higher device yields.

[0008] The laser device of this concept avoids the phase mismatch caused by facet coating. This is achieved by including an anti-reflection coating on each of the first and second facets. AR coatings do not allow for arbitrary phase conditions in the laser device. Therefore, the laser device avoids the common phase mismatch caused by facet coatings and improves array compatibility. The laser device of the present disclosure uses a DFB structure to perform the lasing function and at least one DBR structure to provide optical feedback, with both structures having a common active layer to achieve the PPR effect. This leads to an increase in modulation bandwidth, for example, a higher modulation bandwidth of over 100 GHz. Therefore, the laser device according to the present invention provides a dual DFB laser with a common active layer (DFB+DBR) and a feasible multiple DFB laser with a common active layer, with improved modulation speed and enhanced array compatibility.

[0009] According to one embodiment, the grating structure further includes an ungrating section configured to provide passive feedback of the laser light, the ungrating section being disposed between two grating sections of the grating structure that share a common active layer. According to one embodiment, the grating structure is obtained by a common or single writing process, which may include using either a common or single electron beam, a common or single stepper-based lithography process, or a common or single holographic writing process. According to one embodiment, the grating structure includes at least one phase shift element forming part of one of the grating sections, the at least one phase shift element configured to impart a predetermined phase shift to light traveling through the at least one phase shift element. According to one embodiment, the laser device includes an electrode arrangement, wherein the DFB structure is disposed between a first pair of electrodes, and the first pair of electrodes is associated with the DFB structure to adapt an optical function of the DFB structure.

[0010] According to one embodiment, the DFB structure is configured to obtain a first resonance having a first frequency of carrier photon resonance (CPR). According to one embodiment, the at least one DBR structure is disposed between a second pair of electrodes, and the second pair of electrodes is associated with the at least one DBR structure to adapt an optical function of the at least one DBR structure. According to one embodiment, the at least one DBR structure is configured to obtain a second resonance having a second resonant frequency of the photon-photon resonance (PPR). By this means, a laser device comprising a DFB structure and at least one DBR structure uses the PPR effect and allows for an improvement in the modulation bandwidth. According to one embodiment, the semiconductor substrate comprises at least one of InP, GaAs, Si, SiC, SiNx, and thin film lithium niobate. The process of providing the semiconductor substrate with at least one of InP, GaAs, Si, SiC, SiNx, and thin film lithium niobate may include a micro-transfer printing process or a process involving a film laser.

[0011] According to another aspect of the present invention, a laser device includes an active layer structure disposed between a semiconductor substrate and a lattice structure. The active layer structure includes a common active layer including aluminum (e.g., a common active layer including InGaAlAs), where the common active layer is configured to generate laser light and the lattice structure is configured to manipulate the generation. The laser device further includes a first facet disposed spatially adjacent to one end of the active layer structure and a second facet disposed spatially adjacent to an opposing end of the active layer structure. The first facet is configured to emit laser light, and the second facet is located opposite the first facet. The first facet and the second facet each include an anti-reflection coating. The active layer structure further includes two integrated passive sections disposed spatially adjacent to the opposing ends of the common active layer and the first and second facets. By this means, the laser device, with the aid of the two integrated passive sections, prevents aluminum-based oxidation processes at the facets. This allows the laser device to have aluminum-free facets, thereby improving reliability, since the passive section comprises material that is devoid of aluminum.

[0012] According to another aspect of the inventive concept, a method for fabricating a laser device includes disposing an active layer structure between a semiconductor substrate and a lattice structure. The active layer structure includes a common active layer configured to generate laser light, and the lattice structure is configured to manipulate the generation. The lattice structure includes at least a plurality of integrally formed lattice sections arranged spatially adjacent to one another. The method further includes adapting a cladding structure configured to optically confine the laser light. The lattice structure is disposed between the active layer structure and the cladding structure. The method further includes disposing a first facet spatially adjacent to one end of the active layer structure and a second facet spatially adjacent to an opposing end of the active layer structure. The first facet is configured to emit laser light, the second facet is opposite the first facet, and the first and second facets each include an anti-reflection coating. The method further includes disposing a DFB structure with the first lattice section of the lattice structure. The method further includes disposing at least one DBR structure having a second grating section of the grating structure, such that the first grating section of the DFB structure and the second grating section of the at least one DBR structure share a common active layer that is common to at least a plurality of the integrally formed grating sections. In accordance with another aspect of the inventive concept, a method for generating laser light includes disposing an active layer structure including a common active layer between a semiconductor substrate and a plurality of integrally formed grating sections of a grating structure, the common active layer configured to generate the laser light and the grating sections configured to manipulate the generation.

[0013] Thus, embodiments leverage the PPR effect to enable the fabrication of laser devices with higher modulation speeds and improved array compatibility, such as, but not limited to, dual DFB lasers (DFB+DBR) with a common active layer, significantly reducing overall manufacturing costs compared to conventional PPR-based lasers.

[0014] In the following description, the embodiments are described in detail, but it should be understood that the embodiments provide many applicable concepts that can be implemented in a wide variety of laser device fields. The specific embodiments described are merely illustrative of particular ways to implement and use the concepts and do not limit the scope of the embodiments. In the following description of the embodiments, the same or similar elements having the same function are given the same reference numerals or identified by the same names, and repeated descriptions of elements given the same reference numerals or identified by the same names are typically omitted. In the following description, numerous details are set forth to provide a more complete description of the embodiments of the present disclosure. However, it will be apparent to those skilled in the art that other embodiments may be practiced without these specific details. In other instances, well-known structures and devices are shown in diagrammatic form, rather than in detail, in order to avoid obscuring the examples described herein. Furthermore, features of different embodiments described herein may be combined with each other unless otherwise stated. Embodiments of the inventive concept are described in detail below with reference to the accompanying drawings. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a schematic cross-sectional view of a laser device according to one embodiment of the inventive concept; [Figure 2] 1 is a schematic cross-sectional view of a laser device according to another embodiment of the inventive concept, the laser device including a DFB structure and a DBR structure. [Figure 3] 1 is a schematic cross-sectional view of a laser device in accordance with another embodiment of the inventive concept, the laser device including a grating structure having a grating-free section. [Figure 4] 1 is a schematic cross-sectional view of a laser device in accordance with another embodiment of the inventive concept, the laser device including a semiconductor optical amplifier section. [Figure 5] 1 is a schematic cross-sectional view of a laser device according to another embodiment of the inventive concept, the laser device including two integrated passive sections. [Figure 6]1 is a schematic cross-sectional view of a laser device according to another embodiment of the inventive concept, the laser device including a DFB section and two DBR sections. [Figure 7] 1 is a schematic block diagram of a method for manufacturing a laser device according to one embodiment of the inventive concept; [Figure 8] FIG. 1 is a schematic block diagram of a method for generating laser light according to an embodiment of the inventive concept. DETAILED DESCRIPTION OF THE INVENTION

[0016] Equivalent or equivalent elements, or elements having equivalent or equivalent functionality, are designated in the following description with the same or equivalent reference numerals, even if they occur in different figures. In the following description, numerous details are set forth to provide a more thorough explanation of embodiments of the present invention. However, it will be apparent to those skilled in the art that other embodiments of the present invention can be practiced without these specific details. In other instances, well-known structures and devices are shown in block diagram form, rather than in detail, to avoid obscuring the embodiments of the present invention. Furthermore, features of different embodiments described below can be combined with each other unless otherwise specified. To facilitate the description of the different embodiments, the drawings include a Cartesian coordinate system x, y, z, where the xy plane corresponds to a cross section of the laser device, i.e., is parallel to the cross section, the direction perpendicular to the reference plane (xy plane) corresponds to the "+z" direction, and the direction perpendicular to the reference plane (xy plane) corresponds to the "-z" direction. In the following description, "lateral direction" means a direction parallel to the x direction, "vertical direction" means a direction parallel to the y direction, and "longitudinal direction" means a direction parallel to the z direction.

[0017] A laser device 10 according to one aspect of the inventive concepts of the present disclosure will now be described with reference to FIG. FIG. 1 illustrates, by way of example, a schematic cross-sectional view (parallel to the xy plane) of a laser device 10 including an active layer structure 20, a semiconductor substrate 30, a lattice structure 40, a first facet 50-1, a second facet 50-2, a cladding structure 70, and a DFB structure 60-1 and at least one DBR structure 60-2 that share a common active layer 24 of the active layer structure 20. As seen in FIG. 1 , the active layer structure 20 is disposed between the semiconductor substrate 30 and the lattice structure 40. That is, the active layer structure 20 is sandwiched between the semiconductor substrate 30 and the lattice structure 40, thereby allowing for additional layers, such as buffer layers / waveguides not shown in FIG. 1 but understood by those skilled in the art, between the active layer structure 20 and the semiconductor substrate 30 on the one hand and the active layer structure 20 and the lattice structure 40 on the other hand. In particular, FIG. 1 shows that the lattice structure 40 is sandwiched between the active layer structure 20 and the cladding structure 70. In other words, the lattice structure 40 may be spatially adjacent to the cladding structure 70, and the active layer structure 20 may be spatially adjacent to the lattice structure 40 along one face 22. The active layer structure may also be spatially adjacent to the semiconductor substrate 30, thereby allowing for additional layers therebetween, possibly along an opposing face 23 opposite that face 22. In particular, the active layer structure 20 may extend laterally along the x-direction such that the lateral width of the active layer structure 20 matches the lateral width of the semiconductor substrate 30, the lateral width of the lattice structure 40, and the lateral width of the cladding structure 70.

[0018] According to one embodiment, suitable semiconductor substrates include at least one of InP, GaAs, Si, SiC, SiNx, and thin-film lithium niobate, although not necessarily excluding other suitable materials. The process of providing the semiconductor substrate with at least one of InP, GaAs, Si, SiC, SiNx, and thin-film lithium niobate may include a micro-transfer printing process or a process involving a film laser. The active layer structure 20 includes a common active layer 24 configured to generate laser light. The common active layer 24 is common to at least one, a subset, or preferably all of the DFB and DBR structures of the laser device 10. In contrast to other aspects and embodiments of the inventive concepts described in this disclosure, ends 28-1, 28-2 of the active layer structure 20 may coincide with ends 28-1, 28-2 of the common active layer 24, as shown in FIG.

[0019] As will be explained in more detail below, particularly with reference to Figures 2-6, the common active layer 24 may itself be a layer stack that is structured, including a specific multiple quantum well (MQW) structure, and / or sandwiched between specific waveguide layers. According to one embodiment, the active layer may include at least one of InGaAsP(QW) / InGaAsP(barrier) multiple quantum well (MQW), InGaAlAs(QW) / InGaAlAs(barrier) MQW, InGaAsP(QW) / InGaAlAs(barrier) MQW, InAs multiple quantum dot (MQD), and InAs MQDash material. The grating structure 40 of the laser device 10 is configured to manipulate the generation of laser light. This manipulation may include modifying the optical properties of the laser light provided by the common active layer 24. For example, modifying the optical properties of the laser light may include changing the optical gain of the laser light, exciting a mode of the laser light to enable resonance, or changing the phase of the laser light. The lattice structure 40 includes a plurality of integrally formed lattice sections 42-1, 42-2, . . . arranged spatially adjacent to one another to allow for the inclusion of further sections therebetween.

[0020] According to one embodiment, the grating structure 40 may be obtained by a common or single writing process, which may include, but is not limited to, using either a common or single electron beam, a common or single stepper-based lithography process, or a common or single holographic writing process. The multiple grating sections 42-1, 42-2, . . . are arranged on the same or a common active layer 24, which can be easily obtained by a common or single writing step, to provide a fixed phase condition.

[0021] FIG. 1 exemplarily illustrates that the grating structure 40 includes two integrally formed grating sections 42-1, 42-2 spatially adjacent to one another. The multiple integrally formed grating sections 42-1, 42-2, ... may be defined by a single grating writing field for fabrication, such as an electron beam grating writing system using an electron beam exposure field, a common stepper-based lithography process, or a common holographic writing process. Using a single grating writing process ensures that the grating sections 42-1, 42-2, ... are written consecutively, i.e., directly in a single pass. This results in a predetermined phase condition across the multiple grating sections 42-1, 42-2, ... that are directly written by the single grating writing field. More specifically, using a single writing step allows for the predetermined phase condition in the fabricated device to be accurately obtained and maintained across a large number of fabricated devices, resulting in a high yield.

[0022] At least two of the grating sections 42-1, 42-1, . . . are spatially separated, ie, do not spatially overlap, and, for example, have a common boundary or border. In other words, the grating structure 40 includes two or more spatially separated grating sections 42-1, 42-2, ... arranged adjacent to one another. The two or more spatially separated sections 42-1, 42-2, ... may be integrally formed to achieve a specific phase condition across them. Thus, any phase across the grating sections 42-1, 42-2, ... of the grating structure 40, and therefore phase mismatch within the laser device 10, is avoided. This improves device yield and therefore array compatibility of the laser device 10. The materials of the semiconductor substrate 30 and the lattice structure 40 may include at least one of InP, InGaAsP, InGaAs, and other suitable materials. The DFB structure 60-1 has a first grating section 42-1 of the grating structure 40, and at least one DBR structure has a second grating section 42-2 of the grating structure 40. The first grating section 42-1 and the second grating section 42-2 share a common active layer 24.

[0023] A possible embodiment of the present invention may relate to a laser device including a DFB structure 60-1 and at least one DBR structure 60-2, which means that the laser device may have a DFB structure and two DBR structures, or a DFB structure and three DBR structures, or a DFB structure and a greater number of DBR structures, as exemplarily illustrated in one of the figures of the present disclosure. Alternatively or additionally, the DFB structures may be configured to provide the optical function of the DFB structures as a lasing function. That is, any one DFB structure of the two, three, or more DFB structures may provide the lasing function for the laser device, and each of the other DFB structures of the two, three, or more DFB structures may provide the function of an optical reflector. In one embodiment, it is also feasible that only one DFB structure of the two, three, or more DFB structures may exclusively provide the lasing function for the laser device.

[0024] Thus, in accordance with embodiments of the inventive concepts, it is feasible that a laser device may include multiple DFB structures and multiple DBR structures that share a common active layer 24. Each of the multiple DFB structures may have a grating section of the grating structure 40. Each of the multiple DBR structures may have a grating section of the grating structure 40. The multiple DFB structures and multiple DBR structures may be arranged to share a common active layer 24 that is common to at least a plurality of integrally formed grating sections 42-1, 42-2, .... Additional structures may be disposed in or on the same common active layer 24 or different active layers as part of the active layer structure 20.

[0025] 1 exemplarily illustrates a laser device 10 including a DFB structure 60-1 and a DBR structure 60-2. The DFB structure 60-1 includes a first grating section 42-1, and the DBR structure 60-2 includes a second grating section 42-2. The DFB structure 60-1 and the DBR structure 60-2 are spatially adjacent to each other and share a common active layer 24 that is common to the grating section 42-1 of the DFB structure 60-1 and the second grating section 42-2 of the DBR structure 60-2. Implementing the common active layer 24 may involve single electron beam or stepper writing or holographic writing, which can avoid the need for an interface between different bonded active layers and thus provide precise phase conditions across the DFB structure 60-1 and the DBR structure 60-2. By eliminating the need to bond different portions or sections of the active layer, which can cause undesirable effects or deviations in the phase condition, the target or designed phase condition can be precisely achieved across multiple devices, thereby resulting in a high yield in the manufacturing process of the laser device 10. This allows the common active layer 24 of the laser device 10 to be configured to maintain a specific phase condition across the DFB structure 60-1 and the DBR structure 60-2. This helps to further avoid phase mismatches in the laser device 10 and reduces overall manufacturing costs.

[0026] It is also a feasible embodiment that the laser device of the present inventive concept may be additionally designed or optimized to allow for uncooled operation. The DFB structure 60-1 includes a first associated optical function as a laser oscillation function. That is, the DFB structure 60-1 may be configured to generate laser light. In other words, the DFB structure 60-1 is configured to enable lasing action of laser light provided by the common active layer 24. The at least one DBR structure 60-2 includes a second associated optical function. The second associated optical function may include optical feedback. In other words, the at least one DBR structure 60-2 may be configured to provide optical feedback of the laser light. The optical feedback of the laser light may include reflection.

[0027] Although not explicitly shown in FIG. 1 , the DFB structure 60-1 may be provided with a structure that enables electrical activation of the DFB structure 60-1. Electrical activation, or energization, of the DFB structure may include biasing and / or modulating the DFB structure with an electrical signal via application of an electric field, such as an injection current. Also, although not explicitly shown in FIG. 1 , at least one DBR structure 60-2 may be provided with a structure that enables electrical activation of the at least one DBR structure 60-2. This electrical activation or energization of the at least one DBR structure 60-2 may be optional. In other words, various embodiments of the inventive concept may relate to at least one DBR structure 60-2, and at least one DBR structure 60-2 may lack a structure that enables its energization. In other words, at least one DBR structure 60-2 may be configured not to be modulated. Furthermore, in embodiments of the present invention in which a laser device may include multiple DBR structures, at least one of the multiple DBR structures may be provided with a structure that enables energization.

[0028] The laser device of Figure 1 can function as a light-emitting device. In particular, light can be emitted in response to an electrical signal applied between the DFB structure 60-1 on the one hand and the semiconductor substrate 30 on the other hand. While the laser device 10 according to Figure 1 may be referred to as a dual DFB laser with a common active layer or a DFB+DBR laser with a common active layer, it should be noted that, in accordance with the inventive concepts, multiple DFB structures and multiple DBR structures may optionally share a common active layer, resulting in a multi-laser device with a common active layer. According to one embodiment, the laser device 10 may include an electrode arrangement, in which the DFB structure 60-1 may be disposed between a first pair of electrodes associated with the DFB structure 60-1 to adapt the optical function of the DFB structure 60-1, i.e., the laser oscillation action of the DFB structure 60-1. Such electrodes may be used to apply an electric field to the DFB structure 60-1 and thereby activate, tune, or modulate the optical field. Different electrode pairs may, but need not, have separate or distinct electrodes. For example, different electrode pairs may share a common electrode, such as a reference electrode, e.g., electrode 66-3 in FIG. 2 . According to one embodiment, the DFB structure 60-1 may be configured to obtain a first resonance having a first frequency of carrier photon resonance (CPR). According to one embodiment, the laser device 10 may include an electrode arrangement, and at least one DBR structure 60-2 may be disposed between a second electrode pair, and the second electrode pair is associated with the at least one DBR structure 60-2 to adapt the optical function of the at least one DBR structure 60-2. According to one embodiment, the at least one DBR structure 60-2 may be configured to obtain a second resonance having a second resonant frequency of the photon-photon resonance (PPR).

[0029] In the following, an illustrative example of an embodiment of the inventive concept according to Figure 1 will be described in more detail. It will be understood by those skilled in the art that the following details are intended to provide only non-limiting examples of the many possible variations of laser device 10. For example, a portion of the common active layer 24 shared by the DFB structure 60-1, and thus the first grating section 42-1 of the grating structure 40, may be biased and modulated with the aid of an electrode arrangement to provide lasing of the laser light provided by the active layer 24. The lasing of the laser light may result in a first resonance having a first frequency, such as a carrier-photon resonance (CPR) frequency. A different portion of the common active layer 25 shared by the DBR structure 60-2, and thus the second grating section 42-2 of the grating structure 40, may be biased with the aid of an electrode arrangement to provide optical feedback via reflection within the laser device 10.

[0030] At least one DBR structure 60-2 may be electrically inactive, for example, based on the lack of electrodes or other means, i.e., at least one DBR structure 60-2 may be adapted to allow light emitted from the DFB structure 60-1 to be optically transparent within the at least one DBR structure 60-2. This allows the at least one DBR structure 60-2 to function as a controllable Bragg grating section, if desired. Therefore, light emitted by the lasing action of the first DFB structure 60-1, i.e., light that may be emitted from the DFB structure 60-1, may optically transmit the second DFB structure 60-2 and its components of the common active layer 24. Light emitted from the DFB structure 60-1 may compensate for losses in the at least one DBR structure 60-2, thus making the at least one DBR structure 60-2 transparent. This reduces absorption losses and results in significant reflection in the laser device 10.

[0031] Regardless of electrical activation of at least one DBR structure 60-2, the DBR structure 60-2 may be adapted to enable a second resonance having a second resonant frequency, such as a photon-photon resonance (PPR) having a photon-photon resonance frequency. In particular, the DBR structure 60-2 may be electrically pumped to obtain a specific value of the PPR frequency. The second resonant frequency may be higher than the first resonant frequency, i.e., the PPR frequency may be higher than the CPR frequency. In other words, the mode associated with PPR may be higher than the mode associated with CPR. That is, the DBR mode may be adapted to be on the longer wavelength side of the DFB mode. Therefore, the laser device 10 may achieve a higher modulation speed due to the higher PPR frequency allowed by the PPR effect. 1, according to one embodiment, the laser device 10 may include a second DBR structure. The optical function of the second DBR structure may include mode selection for the laser device. That is, the second DFB structure may select the frequency of light provided by the common active layer 24 of the active layer structure 20.

[0032] 1, the first facet 50-1 is arranged spatially adjacent to one end 28-1 of the active layer structure 20, and the second facet 50-2 is arranged spatially adjacent to the opposing end 28-2 of the active layer structure 20. The second facet 50-2 is located opposite the first facet 50-1. The first facet 50-1 is configured to emit laser light. It is also possible that the second facet 50-2, instead of the first facet 50-1, may be configured to emit laser light. Thus, either the facet 50-1 or 50-2 configured to emit light may form the front facet of the laser device 10, and the other facet may form the back facet of the laser device 10. As can also be seen in FIG. 1 , facets 50-1, 50-2 may extend in a vertical direction parallel to the y-axis so as to cover laterally opposing side surfaces of semiconductor substrate 30, laterally opposing side surfaces formed at ends 28-1, 28-2 of active layer structure 20, and laterally opposing side surfaces of lattice structure 40.

[0033] Each of the first facet 50-1 and the second facet 50-2 may include an anti-reflection (AR) coating 52. The AR coating 52 mitigates the adverse effects of random phase introduced into the laser light by facet reflections. The AR-coated facets 50-1, 50-2 thus help maintain a predetermined phase condition in the laser device 10, which, in combination with the PPR effect, can result in a high single-mode yield device, e.g., at least 80%, at least 90% or more, e.g., up to 100%, for high modulation rate applications and ensure array compatibility. Alternatively, or in addition, either of the facets 50-1, 50-2 may be tilted longitudinally along the longitudinal projection, which is at an angle relative to the z-direction. That is, at least one of the first facet 50-1 and the second facet 50-2 may be arranged to be tilted at an oblique angle. The oblique angle may be within an acceptable range, for example, at least 7°, or in some cases at least 9°. The tilted or beveled facets may avoid back reflections in the laser device 10.

[0034] In other words, each facet 50-1, 50-2 may include an AR coating 52, and either of these facets 50-1, 50-2 may be tilted or sloped at an inclination angle along a longitudinal projection, which is at an angle with respect to the z-direction. The AR coating and tilt of the facet may then further avoid back reflections. It should be understood that any one of the facets 50-1, 50-2 that includes an AR coating 52 may be tilted, or both facets 50-1, 50-2 that include an AR coating 52 may be tilted.

[0035] The material of the facets 50-1, 50-2 may be formed by the sides of the layer stack of the device without preventing possible further coatings. The cladding structure 70 is configured to optically confine the laser light, and is adapted such that the grating structure 40 is disposed between the active layer structure 20 and the cladding structure 70 . According to another embodiment, the conductivity type of the semiconductor substrate 30 may be opposite to the conductivity type of the cladding structure 70. For example, the conductivity type of the semiconductor substrate 30 may comprise n-type and the conductivity type of the cladding structure 70 may comprise p-type, or vice versa. The material of the cladding layer 70 may include at least one of a quaternary layer, InGaAs, and InP cladding.

[0036] It should also be understood that the semiconductor substrate 30, cladding structure 70, active layer structure 20, facets 50-1, 50-2, and lattice structure 40 may extend longitudinally along a longitudinal projection that may be parallel to the z direction. This means that the semiconductor substrate 30, cladding structure 70, active layer structure 20, and lattice structure 40 may have equal longitudinal cross sections in the xz plane perpendicular to the cross-sectional view shown in Figure 1. The facets 50-1, 50-2 may also have longitudinal cross sections in the yz plane perpendicular to the cross-sectional view shown in Figure 1, because they extend vertically along the y direction and cover the side surfaces of the semiconductor substrate 30, the side surfaces of the active layer structure 20 defined by its ends 28-1, 28-2, and the side surfaces of the lattice structure 40. After describing some embodiments of the inventive concept with reference to Figure 1, further embodiments of the laser device will be described with reference to Figures 2-6. In particular, embodiments of the laser device 10 with various realizations of the grating structure 40 and the active layer structure 20 will be described.

[0037] 2 exemplarily illustrates a schematic cross-sectional view parallel to the xy plane of a laser device 200 according to one embodiment. The laser device 200 may be formed in accordance with the laser device 10. Details described herein in connection with FIG. 2 may be combined with the laser device 10. The DFB structure 60-1 and the DBR structure 60-2 may be arranged to share a portion of the cladding structure 70 and partially cover the lattice structure 40. Both the DFB structure 60-1 and the DBR structure 60-2 may be covered by a contact layer 74, which is a different electrically isolated portion of the same conductive layer, with the different portions having the same conductivity type as the DFB structure 60-1 and the DBR structure 60-2. The portions 74-1 and 74-2 of the contact layer 74 may be arranged such that their lateral extensions coincide with the lateral extensions of the DFB structure 60-1 and the DBR structure 60-2 that they cover. That is, the first portion 74-1 may extend laterally the same width, at least within a tolerance, as the first grating section 42-1 of the first DFB structure 60-1, and the second portion 74-2 may extend laterally the same width, at least within a tolerance, as the second grating section 42-2 of the DBR structure 60-2. For example, the contact layer 74 may be formed of a metal.

[0038] In particular, the laser device 200 may include an electrode arrangement in which the DFB structure 60-1 is disposed between a first electrode pair 66-1 / 66-3 and at least one DBR structure 60-2 is disposed between a second electrode pair. The electrode 66-1 of the first electrode pair may be disposed to partially cover the contact layer 74, e.g., portion 74-1, such that the contact layer 74 is disposed between the DFB structure 60-1 and the electrode 66-1. Another electrode 66-2 of the second electrode pair, including electrodes 66-2 and 66-3, may be disposed to cover a portion of the contact layer 74, e.g., portion 74-2, such that the contact layer 74 is disposed between the at least one DBR structure 60-2 and the other electrode 66-2. Each of the electrodes 66-1, 66-2 may have a lateral extension that essentially or exactly matches the lateral extension of the corresponding portion 74-1, 74-2 of the contact layer 74.

[0039] 2 also shows that the first electrode pair and the second electrode pair may share a common electrode 66-3 disposed on the first surface of the semiconductor substrate 30 facing outward from the active layer structure 20. The common electrode 66-3 has an opposite polarity to one electrode 66-1 and the other electrode 66-2. For example, the electrodes 66-1 and 66-2 may be p-type, and the common electrode 66-3 may be n-type. In another example, in contrast to the previous example, the electrodes 66-1 and 66-2 may be n-type, and the common electrode 66-3 may be p-type. Sharing a common electrode between different electrode pairs may enable precise setting of voltages and / or avoidance of offsets between different pairs. Sharing a common voltage may also provide a common ground terminal. However, this does not exclude configurations in which two or more electrode pairs do not share a common electrode, for example, by segmenting electrode 66-3, which may allow for increased degrees of freedom for controlling the device. A common electrode may also be used for more than two DBR structures. Alternatively or additionally, the electrode arrangement may be configured to provide current conduction for DFB structure 60-1. Furthermore, it may be feasible for the electrode arrangement to be configured to exclusively provide current conduction for DFB structure 60-1.

[0040] Although common electrode 66-3 is shown as being disposed adjacent to substrate 30 on the first surface, with segmented electrodes 66-1 and 66-2 on the other side of common active layer 24, this arrangement may also be reversed, e.g., electrodes 66-1 and 66-2 may be formed as common electrodes, with electrode 66-3 being segmented accordingly. It is also feasible that the common electrodes may be arranged so that one of the common electrodes is adjacent to substrate 30 and the other of the common electrodes is adjacent to cladding structure 70. It is further feasible that the electrode arrangement may be adapted to have surface contacts disposed on the surface of the laser chip / device. In some cases, but not exclusively, the semiconductor substrate may be insulated, i.e., may not include electrodes. In particular, the electrode arrangement may be a surface electrode arrangement adapted to provide electrical conduction and to be disposed on a surface of the cladding structure 70 facing outward from the active layer structure 20. That is, the electrode arrangement may be implemented or realized on a surface of the laser device that is not adjacent to the substrate 30.

[0041] The electrodes may include spacings 68 to segment the electrodes from one another. Figure 2 shows that portions 74-1, 74-2 of contact layer 74, and therefore adjacently disposed segmented electrodes 66-1, 66-2, may be adapted not to extend laterally relative to the overall lateral extension of lattice structure 40, and the lateral extensions of segmented electrodes 66-1, 66-2 may be segmented by spacings 68.

[0042] In particular, as shown in FIG. 2 , the first grating section 42-1 of the grating structure 40 in the first DFB structure 60-1 may include a first plurality of gratings 46-1. The first plurality of gratings 46-1 may be adapted to enable the optical function of the first DFB structure 60-1, i.e., lasing action of the first DFB structure 60-1. The second grating section 42-2 of the grating structure 40 in the DBR structure 60-2 may include a second plurality of gratings 46-2. The second plurality of gratings 46-2 may be adapted to enable the optical function of the second DFB structure 60-2. The grating characteristics of the grating sections 42-1, 42-2, such as the grating period, grating height, or grating shape, may be configured to operate the DFB structure 60-1 and the DBR structure 60-2. Each grating of the grating sections may have an individual layout adapted to the optical function of, for example, the DFB and / or DBR structure. For example, forming or fabricating integrally formed grating sections using a single writing step may allow for easy formation of different grating sections or different properties for different sections while maintaining phase conditions between the different sections.

[0043] According to one embodiment, the plurality of integrally formed grating sections 42-1, 42-2, . . . may include complex coupled gratings and / or exponential coupled gratings. According to one embodiment, at least two grating periods of the plurality of integrally formed grating sections 42-1, 42-2, ... may be equal to each other, and the coupling coefficients of the at least two grating sections 42-1, 42-2, ... may be equal to each other. According to one embodiment, the grating periods of at least two of the plurality of integrally formed grating sections 42-1, 42-2, ... may be different from each other, and the coupling coefficients of the at least two grating sections 42-1, 42-2, ... may be different from each other. Such a configuration is shown in FIG. 2, where, by way of non-limiting example only, the grating period of the first DFB structure 60-1 may be different from the grating period of the DBR structure 60-2. Specifically, the grating width of the first plurality of gratings 46-1 may be different from the grating width of the second plurality of gratings 46-2. It can also be seen in FIG. 2 that both of the plurality of gratings 46-1, 46-2 may have the same grating height. Variations of grating sections 42-1, 42-2 having plurality of gratings 46-1, 46-2 with different grating heights and / or equal grating widths are also feasible.

[0044] 2, it can also be seen that the grating height of the grating sections 42-1, 42-2 can match the height of the ungrid section 44. Alternatively, the height of the ungrid section 44 can be different from the grating height of at least one of the plurality of grating sections 42-1, 42-2, ... 2 may include a complex coupling lattice. Additionally or alternatively, at least one of the plurality of lattices 46-1, 46-2 may include an exponential coupling lattice. According to one embodiment, the grating structure 40 includes at least one phase shift element 48 forming part of one of the grating sections 42-1, 42-2, ..., the at least one phase shift element 48 configured to impart a predetermined phase shift to light traveling through the at least one phase shift element 48.

[0045] The first grating section 42-1 shown in FIG. 2 may include one phase-shift element 48. It is not excluded to implement the grating section 42-1 with additional phase-shift elements or no phase-shift elements at all. The phase-shift element 48 may be adapted to obtain a phase-shift grating section. That is, the first grating section 42-1 may be a phase-shift grating section. The phase-shift element 48 may have a width selected to obtain a specific phase shift. The width of the phase-shift element 48 may be greater than the grating width of the first plurality of gratings in one or more grating sections. It is also possible for the width of the phase-shift element 48 to be smaller than the grating width of the first plurality of gratings 46-1. While any relationship may be implemented, any advantageous optical relationship may be implemented when comparing the gratings of a grating section with the gratings of the phase-shift elements that are part of it, such as λ / 2, λ / 4, or a multiple of a wavelength, such as 4λ, 3λ, or 2λ.

[0046] According to one embodiment, as shown in FIG. 2, each of the plurality of integrally formed grating sections 42-1, 42-2 may include a plurality of gratings 46 having a ridge waveguide structure or a buried heterostructure. The laser device 200 may include a first waveguide layer or buffer layer 78 disposed between the semiconductor substrate 30 and the active layer structure 20. The laser device 200 may further include a second waveguide layer 80 disposed between the cladding structure 70 and the active layer structure 20 and may be configured to form the grating structure 40. That is, the plurality of gratings 46 may be formed from the second waveguide layer 80. However, in contrast to the illustration of FIG. 2, it may be an equally feasible embodiment of the present invention for the grating 46 to be formed from the first waveguide layer 78, i.e., for the first waveguide layer 78 instead of the second waveguide layer 80 to be configured to form the grating structure 40.

[0047] The first and second waveguide layers 78 and 80 may be as wide as the faces 22 and 23 of the active layer structure 20, and may extend laterally within a certain tolerance. The second waveguide layer 80 may have the opposite conductivity type to the semiconductor substrate 30 and the first waveguide layer 78. That is, the first waveguide layer 78 may have the same conductivity type as the semiconductor substrate and the opposite conductivity type to the lattice structure 40 and the cladding structure 70. For example, the first waveguide layer 78 may be n-type and the second waveguide layer 80 may be p-type. For example, it is also possible that the first waveguide layer 78 may be p-type and the second waveguide layer 80 may be n-type.

[0048] The embodiment of laser device 200 shown in Figure 2 is described as a non-limiting example and does not limit the scope of the invention, but may have the following physical and optical characteristics. Therefore, the following characteristics and parameters are intended to be exemplary. It should be noted that the following characteristics and parameters do not limit the achievable parameters and the range of their possible variations. For example, the first DFB structure 60-1 has a wavelength of 250 cm -1 The second DFB structure 60-2 may be a 120 μm long quarter-wave shifted DFB with a grating length of 40 μm and a coupling coefficient of 250 cm. This DFB structure may be optimized for uncooled or cooled operation. -1The active reflector may have a uniform grating having a lattice pattern of 0.01 μm, which may correspond to a reflection of about 58%. The common active layer 24 (CAL) may have a length of 160 μm. This example is one of several possible embodiments that do not limit the present invention.

[0049] 3 exemplarily illustrates a schematic cross-sectional view parallel to the xy plane of a laser apparatus 300 according to one embodiment. Laser apparatus 300 may be formed in accordance with laser apparatus 10 or may be a variation of laser apparatus 200 shown in FIG. 2. Details described herein in connection with FIG. 3 may be combined with laser apparatus 10 and / or 200.

[0050] According to one embodiment, the grating structure 40 may further include a grating-free section 44 configured to provide passive feedback of the laser light, the grating-free section 44 being disposed between two grating sections 42-1, 42-2, ... that share a common active layer 24. That is, the grating-free section 44 and the plurality of grating sections 42-1, 42-2, ... are disposed on the same common active layer 24. In other words, the lattice structure 40 includes two or more spatially separated lattice sections 42-1, 42-2, ... arranged adjacent to one another, allowing at least a lattice-free section 44, or possibly a greater number of lattice-free sections, between any two lattice sections of the plurality of lattice sections 42-1, 42-2, ... that share a common active layer 24.

[0051] The grating-free section 44 and the multiple grating sections 42-1, 42-2, ... are disposed on the same or common active layer 24, which can be easily obtained by a common or single writing step, to provide a fixed phase condition. The multiple integrally formed grating sections 42-1, 42-2, ... and the grating-free section 44 may be defined by a single grating writing field for manufacturing, such as an electron beam grating writing system using an electron beam exposure field. This results in a predetermined phase condition across the multiple grating sections 42-1, 42-2, ... and the grating-free section 44 being directly written by the single grating writing field. The grating-free section 44 may be adapted to allow reflection of the laser light. The grating-free section 44 may also be adapted to not obtain optical gain of the laser light. In particular, the lateral extent of the grating-free section 44 may be selected to improve the optical properties of the laser light. Such optical properties of the light may include, but are not limited to, reflective, absorptive, or transmissive properties.

[0052] FIG. 3 exemplarily illustrates that the lattice structure 40 includes two integrally formed lattice sections 42-1, 42-2, each of which is spatially adjacent to a non-lattice section 44. 3, the lateral extension of the grating-free section 44 may be greater than the lateral extension of any of the grating sections 42-1, 42-2, ... However, this does not preclude implementations of the laser device that include grating-free sections with smaller lateral extensions between the grating sections.

[0053] 3 illustrates that the lattice structure 40 may include one or a single lattice-free section 44, various embodiments may relate to cases in which multiple lattice-free sections are arranged, each of which may be arranged as a single lattice-free section or in combination with at least one additional lattice-free section between any two of the lattice-free sections 42-1, 42-2, ... of the lattice structure 40 that share a common active layer 24. In particular, the multiple lattice-free sections may be arranged adjacent to the multiple lattice-free sections 42-1, 42-2, ... of the lattice structure 40 that share a common active layer 24, such that a combination of the lattice-free section and the lattice section 42-# is obtained, e.g., an alternating combination of the lattice-free section and the lattice section 42-# is obtained.

[0054] Electrical activation may be provided to the grating-free section 44 by disposing the grating-free section 44 with electrodes in an electrode arrangement as described above in this disclosure. Thus, energizing the grating-free section 44 can provide an associated optical function to the grating-free section 44. That is, the grating-free section 44 may be pumped by a pumping means to achieve transparency. Alternatively, the grating-free section 44 may be configured to be unpumped. It is emphasized that the grating-free section 44 may be integrally formed according to a plurality of integrally formed grating sections 42-1, 42-2, ... included in the grating structure 40. The grating-free section may thus be adapted to not introduce undesirable phase mismatches due to component attachment to one another and may maintain predetermined phase conditions across the DFB structures 60-1, 60-2, ....

[0055] 4 shows a schematic cross-sectional view parallel to the xy plane of a laser device 400 according to another embodiment. Laser device 400 may be formed in accordance with laser device 10 according to the described aspects of the inventive concept. Furthermore, laser device 400 may be a variation of laser devices 200, 300 and may further include at least one semiconductor optical amplifier (SOA) section 90 disposed on common active layer 24 between grating structure 40 and one of facets 50-1, 50-2, where SOA section 90 may be configured to modify the optical properties of the laser light, i.e., SOA 90 is configured to increase the output power of the laser light.

[0056] According to one embodiment, the laser device may further include at least one semiconductor optical amplifier (SOA) section 90 disposed on the common active layer 24 between the grating structure 40 and one of the facets 50-1, 50-2, the SOA 90 being configured to modify the optical properties of the laser light, i.e., the SOA 90 being configured to increase the output power of the laser light. For example, the SOA section 90 may be configured to obtain optical gain of the optical signal provided by the common active layer 24. In other words, the SOA section 90 may be adapted to amplify the optical signal provided by the common active layer 24, or the SOA section 90 may be configured to boost / increase the output power of the light provided by the common active layer 24 by electrical pumping means.

[0057] 4 illustrates that one SOA section 90 may be disposed between the first DFB structure 60-1 and the first facet 50-1, and the facets may be configured to share a common active layer 24 and emit laser light. The SOA section 90 may include an unlattice section 92 disposed between the first grating section 42-1 and the first facet 50-1. That is, the unlattice section 92 of the SOA section 90 may be disposed between the cladding structure 70 and the active layer structure 20 in vertical projection parallel to the y direction.

[0058] According to another possible embodiment, the SOA section 90 may be disposed on the active layer structure 20 between the lattice structure 40 and one of the facets 50-1, 50-2. That is, in some cases, the SOA section 90 may be configured so as not to share a common active layer 24. For example, the lattice-free section 92 of the SOA section 90 may be disposed between the cladding structure 70 and an additional active layer that is different from the common active layer as part of the active layer structure 20. This additional active layer may be disposed adjacent to the common active layer 24, possibly using other processes, including but not exclusively, butt-jointing. Additionally or alternatively, the SOA section 90 may be disposed between the DBR structure 60-2 and the second facet 50-2, where the facet may be configured to emit laser light instead of the first facet 50-1. In particular, the grating-free section 92 may be disposed between the second grating section 42-2 and the second facet 50-2. However, the SOA section 90 may advantageously be disposed between the DBR structure 60-2 and any of the facets 50-1, 50-2 configured to emit light. That is, a variation of the laser device 400 of FIG. 4 in which the SOA section 90 is disposed adjacent to the DBR structure 60 and adjacent to the facet 50-2 configured to emit light instead of the facet 50-1 forms a viable embodiment.

[0059] Further embodiments provide structures that include two or more SOA sections, for example, two SOA sections, each of which may be positioned between one of the facets 50-1, 50-2 and an end of the grating structure 40. Optionally, such a single SOA may be extended by additional SOAs. Thus, the SOA section 90 can improve the output optical power of the laser light emitted by the laser device in accordance with the inventive concepts of the present disclosure.

[0060] FIG. 5 shows a schematic cross-sectional view parallel to the xy plane of a laser device 500 according to an independent embodiment of the inventive concept. The laser device 500 may include an active layer structure 20 disposed between a semiconductor substrate 30 and a lattice structure 40. The active layer structure 20 may include a common active layer 24 formed to include aluminum. For example, the common active layer 24 may include InGaAlAs, thus including aluminum. The common active layer 24 is configured to generate laser light, and the lattice structure 40 is configured to manipulate the generation. The laser device 400 may further include a first facet 50-1 spatially adjacent to an end 28-1 of the active layer structure 20 and a second facet 50-2 spatially adjacent to an opposing end 28-2 of the active layer structure 20. The first facet 50-1 may be configured to emit laser light, the second facet may be opposite the first facet, and the first facet and second facet 50-2 may include an anti-reflective coating 52. The active layer structure 20 may include two integrated passive sections 94-1, 94-2 disposed spatially adjacent to opposite ends 28-1, 28-2 and the first and second facets 50-1, 50-2 of the active layer 24. That is, in one embodiment, the active layer structure 20 includes exactly two integrated passive sections formed, for example, as aluminum-free passive sections.

[0061] The aluminum-free passive sections 94-1, 94-2 may be adapted to provide spatial separation between the facets 50-1, 50-2 to minimize optical loss of laser light. In particular, aluminum in the common active layer 24 may induce optical loss. Because aluminum has a high chemical affinity for oxygen, exposing the aluminum-containing common active layer 24 to air or an oxygen-rich environment through the facets 50-1, 50-2 may lead to undesirable oxidation processes and adversely affect device reliability. Therefore, the integrated passive sections 94-1, 94-2 may provide spatial separation between the aluminum-containing common active layer 24 and the facets 50-1, 50-2. In other words, the passive sections may surround the ends 28-1, 28-2 of the aluminum-containing common active layer 24 to obtain aluminum-free facets 50-1, 50-2. Therefore, the laser device 500 with the aid of the integrated passive sections 94-1, 94-2 may enable an improvement in the reliability of the device.

[0062] It should be noted that the laser device 500 as shown in Figure 5 may also be understood as an embodiment of the aspect of the present invention described with reference to Figures 1 to 4. In particular, the laser device 500 may be considered as a modification of the laser device according to Figures 1 to 4 described above. 5, the first passive section 94-1 may be disposed adjacent to the first facet 50-1, i.e., the front facet or a facet that may be configured to emit light, and the end 28-1 of the common active layer 24. The second passive section 94-2 may be disposed adjacent to the second facet 50-2, i.e., the back facet or a facet that may not be configured to emit light, and the end 28-2 of the common active layer 24. The passive sections 94-1, 94-2 may cover the sides of the active layer defined by the ends 28-1, 28-2, i.e., the sides of the passive sections 94-1, 94-2 may extend longitudinally, i.e., parallel to the z-direction, along the longitudinal extension or length of the common active layer 24.

[0063] Additionally, the aluminum-free integrated passive sections 94-1, 94-2 may be positioned by forming a butt joint at the interface between the end 28-1, 28-2 of the common active layer 24 and the facet 50-1, 50-2. The passive sections 94-1, 94-2 may be vertically surrounded on one side by grating-free waveguide sections 98-1, 98-2 and on the other side by the waveguide layer 78. As seen in FIG. 4 , the grating-free waveguide section 98-1 may abut the first facet 50-1 and the first passive section 94-1, and the grating-free waveguide section 98-2 may abut the second facet 50-2 and the second passive section 94-2. The material of the integrated passive section may include InGaAsP and / or other suitable materials.

[0064] FIG. 6 exemplarily illustrates a schematic cross-sectional view parallel to the xy plane of a laser device 600 according to one embodiment. The laser device 600 may be formed in accordance with the laser device 10 and may include a DFB structure 60-1 and two DBR structures 60-2 and 60-3 having integrally formed grating sections 42-1, 42-2, and 42-3 of a grating structure 40 that share a common active layer 24. In FIG. 6 , more than one DBR structure, for example, two DBR structures, are implemented. The embodiments described in connection with other laser devices of this disclosure may be implemented in the laser device 600 without limitation.

[0065] The DFB structure 60-1 may be disposed adjacent to the first DBR structure 60-2 on one side and adjacent to the second DBR structure 60-3 on the other side. The second DBR structure 60-3 may be disposed between the DFB structure 60-1 and the first facet 50-1. The first DBR structure 60-2 may be disposed between the second facet 50-2 and the DFB structure 60-1. The DFB structure 60-1 may have a first grating section 42-1 having a first grating period, the first DBR structure 60-2 may have a second grating section 42-2 having a second grating period, and the second DBR structure 60-3 may have a third grating section 42-3 having a third grating period.

[0066] 6, the second grating period may optionally be greater than both the first and third grating periods, and the first grating period may optionally be less than the third grating period. Other variations involving comparing the grating periods of grating sections 42-1, 42-2, and 42-3 to one another may provide possible alternatives. As previously described in this application, for example, the first, second, and third grating periods may be equal to one another.

[0067] The grating width of the plurality of gratings 46-2 in the second grating section 42-2 may be larger than the grating width of the plurality of gratings 46-1 in the first grating section 42-1 and the grating width of the plurality of gratings 46-3 in the third grating section 42-3. The grating width of the plurality of gratings 42-1 in the first grating section 42-1 may be equal to the grating width of the plurality of gratings 42-3 in the third grating section 42-3. Each of the DFB structure 60-1 and the DBR structures 60-2, 60-3 may be arranged with their respective electrode pairs 66-1 / 66-3, 66-2 / 66-3, 66-5 / 66-3.

[0068] In particular, the laser device 600 may include an electrode arrangement in which the DFB structure 60-1 is disposed between a first electrode pair 66-1 / 66-3, the first DBR structure 60-2 is disposed between a second electrode pair 66-2 / 66-3, and the second DBR structure 60-3 is disposed between a third electrode pair 66-5 / 66-3. The electrode 66-1 of the first electrode pair may be disposed to partially cover the contact layer 74, e.g., portion 74-1, such that the contact layer 74 is disposed between the DFB structure 60-1 and the electrode 66-1. The other electrode 66-2 of the second electrode pair, including electrodes 66-2 and 66-3, may be disposed to cover at least a portion of the contact layer 74, e.g., portion 74-2, such that the contact layer 74 is disposed between the first DBR structure 60-2 and the other electrode 66-2. The third electrode 66-5 of the third electrode pair, including electrodes 66-5 and 66-3, may be disposed to cover at least a portion, such as portion 74-3, of the contact layer 74 such that the contact layer 74 is disposed between the second DBR structure 60-3 and the third electrode 66-3. Each of the electrodes 66-1, 66-2, 66-3 may have a lateral extension that essentially or exactly coincides with the lateral extension of the corresponding portion 74-1, 74-2, 74-3 of the contact layer 74.

[0069] Each of the DFB structure 60-1 and the DBR structures 60-2, 60-3 may include associated optical functions. For example, the laser device 600 may be a DFB+dual DBR laser device, where the optical function of the DFB 60-1 may be lasing action, in which the DFB may be configured to obtain CPR having a CPR frequency, the optical function of the first DBR 60-2 may be mode selection, for example, variably implemented based on the application of an optional electric field, and the optical function of the second DBR 60-3 may include optical feedback, in which the second DBR may be configured to obtain PPR having a PPR frequency associated with the second DBR. It is also possible to swap the optical functions of the first DBR 60-2 and the second DBR 60-3, i.e., the optical function of the second DBR 60-3 may include optical feedback instead of the first DBR 60-2, and the optical function of the first DBR 60-2 may include mode selection instead of the second DBR 60-3. Therefore, the laser device 600 may have an improved modulation bandwidth due to the PPR effect.

[0070] 2-6, each of the plurality of integrally formed grating sections 42-1, 42-2 may include a plurality of gratings 46 having a ridge waveguide structure or a buried heterostructure. The plurality of gratings 46 may be formed in a waveguide layer 80 having a conductivity type opposite that of the semiconductor substrate 30. Other embodiments of the invention relate to methods for manufacturing laser devices and methods for generating laser light, such methods may be implemented by operation of the described devices.

[0071] 7 shows a schematic block diagram of a method 700 for fabricating a laser device according to an embodiment of the present invention. The method 700 includes step 710 of disposing an active layer structure between a semiconductor substrate and a grating structure, the active layer structure including a common active layer configured to generate laser light, the grating structure configured to manipulate the generation, and the grating structure including a plurality of integrally formed grating sections arranged spatially adjacent to one another, by writing the grating sections using a single or common electron beam field, by writing the grating sections using a single or common stepper lithography process, or by writing the grating sections using a single or common holographic process; and step 720 of adapting a cladding structure configured to optically confine the laser light, the grating structure disposed between the active layer structure and the cladding structure. Step 720 includes arranging a first facet spatially adjacent to one end of the active layer structure and a second facet spatially adjacent to an opposing end of the active layer structure, the first facet configured to emit laser light and the second facet opposite the first facet, the first facet and the second facet including an anti-reflection coating, and step 740 includes arranging a DFB structure having a first grating section of a grating structure and at least one DBR structure having a second grating section of a DBR structure, the first grating section of the DFB structure and the second grating section of the at least one DBR structure sharing a common active layer that is common to at least a plurality of integrally formed grating sections, which may provide a fixed phase condition when comparing different devices formed by the same process.

[0072] 8 shows a schematic block diagram of a method 800 for generating laser light according to an embodiment of the present invention. The method 800 includes step 810 of disposing an active layer structure including a common active layer between a semiconductor substrate and a plurality of integrally formed grating sections of a grating structure, the common active layer configured to generate laser light and the grating sections configured to manipulate the generation.

[0073] Embodiments according to the present disclosure relate to the following aspects. Aspect 1 is an active layer structure disposed between the semiconductor substrate and the grating structure, the active layer including a common active layer configured to generate laser light; an active layer structure in which the lattice structure is configured to manipulate the generation; a first facet disposed spatially adjacent to one end of the active layer structure, and a second facet disposed spatially adjacent to an opposing end of the active layer structure; a first facet configured to emit laser light, a second facet opposite the first facet, the first facet and the second facet each including an anti-reflective coating; a first facet and a second facet, the grating structure including a plurality of integrally formed grating sections arranged spatially adjacent to one another; a cladding structure configured to optically confine laser light, the cladding structure being adapted such that the grating structure is disposed between the active layer structure and the cladding structure; a DFB structure having a first grating section of a grating structure; at least one DBR structure having a second grating section of the grating structure, the first grating section and the second grating section share a common active layer that is common to at least a plurality of the integrally formed grating sections; At least one DBR structure, wherein the DFB structure includes a first associated optical function as a lasing function, and the at least one DBR structure includes a second associated optical function; A laser device is provided, comprising:

[0074] Aspect 2 provides the laser device of aspect 1, wherein the grating structure further includes an ungreasing section configured to provide passive feedback of the laser light, the ungreasing section being disposed between two grating sections of the grating structure that share a common active layer. Aspect 3 provides the laser device of aspect 1 or 2, wherein the grating structure is obtained by a common or single writing process.

[0013] Aspect 4 provides a laser apparatus according to any preceding aspect, wherein the grating structure includes at least one phase-shifting element forming a portion of one of the grating sections, the at least one phase-shifting element configured to impart a predetermined phase shift to light traveling through the at least one phase-shifting element.

[0075] Aspect 5 provides a laser device according to any of the preceding aspects, wherein the conductivity type of the semiconductor substrate is opposite to the conductivity type of the cladding structure. A sixth aspect provides a laser device according to any of the preceding aspects, including an electrode arrangement, wherein the DFB structure is disposed between a first pair of electrodes, and the first pair of electrodes is associated with the DFB structure to adapt an optical function of the DFB structure. Aspect 7 provides the laser device of aspect 6, wherein the DFB structure is configured to obtain a first resonance having a first frequency of a carrier-photon resonance (CPR).

[0076] Example 8 provides a laser device according to Example 6 or 7, wherein the at least one DBR structure is disposed between a second pair of electrodes, and the second pair of electrodes is associated with the at least one DBR structure to adapt an optical function of the at least one DBR structure. Aspect 9 provides the laser device of aspect 8, wherein the at least one DBR structure is configured to obtain a second resonance having a second resonance frequency of the photon-photon resonance (PPR). A tenth embodiment provides the laser device of any one of the eighth or ninth embodiments, further comprising a second DFB structure, wherein the optical function of the second DFB structure comprises mode selection of the laser device.

[0077] Example 11 provides a laser device according to any preceding example, wherein the active layer comprises at least one of an InGaAsP(QW) / InGaAsP(barrier) multiple quantum well (MQW), an InGaAlAs(QW) / InGaAlAs(barrier) MQW, an InGaAsP(QW) / InGaAlAs(barrier) MQW, an InAs multiple quantum dot (MQD), and an InAs MQD material. Example 12 provides a laser apparatus according to any preceding example, wherein each of the plurality of integrally formed grating sections comprises a complex coupled grating and / or an exponential coupled grating. Example 13 provides a laser device according to any preceding example, wherein each of the plurality of integrally formed grating sections comprises a plurality of gratings having a ridge waveguide structure or a buried heterostructure. Example 14 provides a laser device according to any of the preceding examples, wherein at least two of the plurality of integrally formed grating sections have equal grating periods, and the at least two grating sections have equal coupling coefficients.

[0078] Example 15 provides a laser device according to any of the preceding examples, wherein at least two of the plurality of integrally formed grating sections have grating periods different from each other, and wherein coupling coefficients of the at least two grating sections are different from each other. Example 16 provides a laser apparatus according to any preceding example, including at least one semiconductor optical amplifier (SOA) section disposed on a common active layer between the grating structure and one of the facets, the SOA configured to increase the output power of the laser light. Example 17 provides the laser apparatus of any preceding example, wherein the semiconductor substrate comprises at least one of InP, GaAs, Si, SiC, SiNx, and thin-film lithium niobate.

[0079] Aspect 18 is an active layer structure disposed between the semiconductor substrate and the lattice structure, the active layer structure including a common active layer formed to include aluminum (e.g., a common active layer including InGaAlAs), the common active layer configured to generate laser light and the lattice structure configured to steer the generation; a first facet disposed spatially adjacent to one end of the active layer structure and a second facet disposed spatially adjacent to an opposing end of the active layer structure, the first facet configured to emit laser light and the second facet on an opposite side of the first facet, the first facet and the second facet including an anti-reflective coating; wherein the active layer structure further includes opposing ends of the common active layer and two integrated passive sections disposed spatially adjacent to the first facet and the second facet. A laser device is provided.

[0080] A nineteenth aspect is a method for manufacturing a laser device, comprising: An active layer structure is formed between the semiconductor substrate and the lattice structure. the active layer structure includes a common active layer configured to generate laser light, and the grating structure is configured to steer the generation; and the lattice structure includes a plurality of integrally formed lattice sections arranged spatially adjacent to one another. placing the a cladding structure configured to optically confine laser light; The grating structure is disposed between the active layer structure and the cladding structure. an adapting step; a first facet spatially adjacent one end of the active layer structure and a second facet spatially adjacent an opposing end of the active layer structure; a first facet configured to emit laser light, a second facet opposite the first facet, and the first and second facets including anti-reflective coatings; placing the disposing a DFB structure having a first grating section of a grating structure; at least one DBR structure having a second grating section of the grating structure; The first grating section of the DFB structure and the second grating section of the at least one DBR structure share a common active layer that is common to at least a plurality of integrally formed grating sections. The step of placing The present invention provides a method comprising: Aspect 20 provides a method for generating laser light, the method including the step of disposing an active layer structure including a common active layer between a semiconductor substrate and a plurality of integrally formed grating sections of a grating structure, the common active layer configured to generate laser light and the grating sections configured to manipulate the generation.

[0081] Although some aspects have been described in the context of an apparatus, it will be apparent that these aspects also represent descriptions of corresponding methods, where a block or apparatus corresponds to a method step or feature of a method step. Similarly, aspects described in the context of a method step also represent descriptions of a corresponding block or item or feature of a corresponding apparatus. While the present invention has been described with respect to several embodiments, there are alterations, permutations, and equivalents that fall within the scope of the present invention. It should also be noted that there are many alternative ways of implementing the methods and compositions of the present invention. It is therefore intended that the following appended claims be interpreted to include all such alterations, permutations, and equivalents that fall within the true spirit and scope of the present invention.

[0082] References [1.1]K.Nahakara et.al.,“112-Gb / s PAM-4 Uncooled(25°C to 85°C)Directly Modulation of 1.3-μm InGaAlAs-MQW DFB BH Lasers with Record High Bandwidth”,ECOC 2020,paper PD2.4 [1.2]T.Hiraki et.al.“Uncooled Operation of Directly Modulated Membrane Laser with Buried Sapphire Layer on Si Substrate”,OFC 2024,paper Tu2D.3 [1.3]U.Troppenz,J.Kreissl,M.Mohrle,C.Bornholdt,W.Rehbein,B.Sartorius,I.Woods,M.Schell,“40Gbit / s directly modulated lasers:physics and application,”Proc.SPIE 7953,Novel In-Plane Semiconductor Lasers X,79530F(16 February). 2011) [1.4]Gayatri Vasudevan Rajeswari,Martin Moehrle,Falco Ehrensack,Ute Troppenz,Ariane Sigmund,Martin Schell,“Novel>57GHz Bandwidth O-band InGaAlAs MQW RW DFB,”Proc.SPIE 12440,Novel In-Plane Semiconductor Lasers XXII,1244007(15 March 2023) [1.5]Active license plate 20170256912 license plate [1.6]Matsui,Y.,Schatz,R.,Che,D.et al.Low-chirp isolator-free 65-GHz bandwidth directly modulated lasers.Nat.Photonics 15,59-63(2021). [1.7]S.Yamaoka et.al.“Uncooled 100-GBaud Operation of Directly Modulated Membrane Lasers on High-Thermal-Conductivity SiC Substrate”,ECOC 2020,paper We1E.3 [1.8]N.-P.Diamantopoulos et al.,“60GHz Bandwidth Directly Modulated Membrane III-V Lasers on SiO2 / Si,”in Journal of Lightwave Technology,vol.40,no.10,pp.3299-3306,15 May15,2022,doi:10.1109 / JLT.2022.3153648. [1.9]G.Liu,G.Zhao,J.Sun,D.Gao,Q.Lu,and W.Guo,“Experimental demonstration of DFB lasers with active distributed reflector,”Opt.Express 26,29784-29795(2018). [1.10]G.Vasudevan Rajeswari,M.Moehrle,A.Sigmund,M.Schell,“Dual DFB for Uncooled 40Gbps and Cooled 72 Gbps Direct Modulation”,submitted to ISLC conference 2024.

Claims

1. an active layer structure disposed between the semiconductor substrate and the lattice structure, the active layer structure including a common active layer configured for generation of laser light, the lattice structure configured to manipulate the generation; a first facet disposed spatially adjacent to one end of the active layer structure and a second facet disposed spatially adjacent to an opposing end of the active layer structure, the first facet configured to emit the laser light and the second facet on an opposite side of the first facet, the first facet and the second facet each including an anti-reflection coating; a first facet and a second facet, the grating structure including a plurality of integrally formed grating sections arranged spatially adjacent to one another; a cladding structure configured to optically confine the laser light, the grating structure adapted to be disposed between the active layer structure and the cladding structure; a DFB structure having a first grating section of the grating structure; at least one DBR structure having a second grating section of the grating structure, the first grating section and the second grating section share the common active layer that is common to at least the plurality of integrally formed grating sections; at least one DBR structure, wherein the DFB structure comprises a first associated optical function as a lasing function, and the at least one DBR structure comprises a second associated optical function as optical feedback; A laser device comprising:

2. 10. The laser device of claim 1, wherein the grating structure further comprises an ungreasing section configured to provide passive feedback of the laser light, the ungreasing section being disposed between two grating sections of the grating structure that share the common active layer.

3. 10. The laser device of claim 1, wherein the grating structure is obtained by a common or single writing process.

4. 10. The laser device of claim 1, wherein the grating structure includes at least one phase shift element forming a portion of one of the grating sections, the at least one phase shift element configured to impart a predetermined phase shift to light traveling through the at least one phase shift element.

5. 2. The laser device of claim 1, wherein the conductivity type of the semiconductor substrate is opposite to the conductivity type of the cladding structure.

6. 10. The laser device of claim 1, comprising an electrode arrangement, the DFB structure being disposed between a first pair of electrodes, the first pair of electrodes being associated with the DFB structure to adapt the optical function of the DFB structure.

7. 7. The laser device of claim 6, wherein the DFB structure is configured to obtain a first resonance having a first frequency of a carrier-photon resonance (CPR).

8. 7. The laser device of claim 6, wherein the at least one DBR structure is disposed between a second pair of electrodes, the second pair of electrodes being associated with the at least one DBR structure to adapt the optical function of the at least one DBR structure.

9. 9. The laser device of claim 8, wherein the at least one DBR structure is configured to obtain a second resonance having a second resonant frequency of a photon-photon resonance (PPR).

10. 10. The laser device of claim 1, further comprising a second DBR structure, wherein the optical function of the second DBR structure comprises mode selection of the laser device.

11. 10. The laser device of claim 1, wherein the common active layer comprises at least one of InGaAsP(QW) / InGaAsP(barrier) multiple quantum well (MQW), InGaAlAs(QW) / InGaAlAs(barrier) MQW, InGaAsP(QW) / InGaAlAs(barrier) MQW, InAs multiple quantum dot (MQD), and InAs MQDash materials.

12. 10. The laser device of claim 1, wherein each of the plurality of integrally formed grating sections comprises a complex coupled grating and / or an exponential coupled grating.

13. 10. The laser device of claim 1, wherein each of the plurality of integrally formed grating sections comprises a plurality of gratings having a ridge waveguide structure or a buried heterostructure.

14. 2. The laser device of claim 1, wherein at least two of the plurality of integrally formed grating sections have equal grating periods, and the at least two grating sections have equal coupling coefficients.

15. 2. The laser device of claim 1, wherein at least two of the plurality of integrally formed grating sections have grating periods that are different from each other, and the at least two grating sections have coupling coefficients that are different from each other.

16. 10. The laser device of claim 1, further comprising: at least one semiconductor optical amplifier (SOA) section disposed on the common active layer between the grating structure and one of the first facet and the second facet, the semiconductor optical amplifier (SOA) configured to increase an output power of the laser light.

17. 10. The laser device of claim 1, wherein the semiconductor substrate comprises at least one of InP, GaAs, Si, SiC, SiNx, and thin film lithium niobate.

18. an active layer structure disposed between the semiconductor substrate and the lattice structure, the active layer structure including a common active layer formed to include aluminum, the common active layer configured for generating laser light and the lattice structure configured to manipulate the generation; a first facet disposed spatially adjacent to one end of the active layer structure and a second facet disposed spatially adjacent to an opposing end of the active layer structure, the first facet configured to emit the laser light, the second facet on an opposite side of the first facet, and the first facet and the second facet including an anti-reflection coating; wherein the active layer structure further includes two integrated passive sections disposed spatially adjacent opposite ends of the common active layer and the first and second facets.

19. 1. A method for manufacturing a laser device, comprising: An active layer structure is formed between the semiconductor substrate and the lattice structure. the active layer structure includes a common active layer configured to generate laser light, and the grating structure is configured to manipulate the generation; and the lattice structure includes a plurality of integrally formed lattice sections arranged spatially adjacent to one another; placing the a cladding structure configured to optically confine the laser light, The grating structure is disposed between the active layer structure and the cladding structure. an adapting step; a first facet spatially adjacent one end of the active layer structure and a second facet spatially adjacent an opposing end of the active layer structure; the first facet is configured to emit the laser light, the second facet is opposite the first facet, and the first facet and the second facet include an anti-reflective coating. placing the disposing a DFB structure having a first grating section of the grating structure; at least one DBR structure having a second grating section of the grating structure; the first lattice section of the DFB structure and the second lattice section of at least one DBR structure share the common active layer that is common to at least the plurality of integrated lattice sections. The step of placing A method comprising:

20. 1. A method for generating laser light, comprising: disposing an active layer structure including a common active layer between a semiconductor substrate and a plurality of integrally formed grating sections of a grating structure, said common active layer configured to generate said laser light and said grating sections configured to manipulate said generation; A method comprising:

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