Ring aperture vertical cavity surface-emitting laser (VCSEL) device for mode control
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- II VI DELAWARE INC
- Filing Date
- 2025-12-15
- Publication Date
- 2026-08-05
Smart Images
Figure 2026127031000001_ABST
Abstract
Description
Technical Field
[0001] Claim of Priority
[0001] This application claims the benefit of priority from U.S. Provisional Patent Application No. 63 / 833,908, filed on January 24, 2025, and U.S. Provisional Patent Application No. 63 / 749,559, filed on January 25, 2025, and claims the benefit of these applications. Each of the applications identified above is hereby incorporated by reference in its entirety.
[0002]
[0002] Aspects of the present disclosure relate to optical communication-based solutions. More particularly, certain implementations of the present disclosure relate to methods and systems for implementing and utilizing a ring aperture vertical cavity surface emitting laser (VCSEL) device for mode control.
Background Art
[0003]
[0003] The limitations and drawbacks of conventional diffraction gratings will become apparent to those skilled in the art through a comparison of such systems with some aspects of the present disclosure as described in the remainder of this application with reference to the drawings.
Summary of the Invention
[0004]
[0004] As more fully set forth in the claims, systems and methods for a ring aperture vertical cavity surface emitting laser (VCSEL) device for mode control, substantially as shown in at least one of the figures and / or as described in connection therewith, are provided.
[0005]
[0005] These and other advantages, aspects, and novel features of the present disclosure, as well as details of the illustrated embodiments thereof, will be more fully understood from the following description and the drawings.
Brief Description of the Drawings
[0006] [Figure 1]
[0006] A diagram showing an exemplary vertical cavity surface emitting laser (VCSEL). [Figure 2]
[0007] This figure shows example circular and ring apertures, along with their corresponding current and fundamental mode intensity profiles. [Figure 3]
[0008] This figure shows an example of a VCSEL with a ring opening, and an example of a process for manufacturing a VCSEL. [Figure 4]
[0009] This figure shows an example ring aperture and an example optical mode. [Figure 5]
[0010] This figure shows examples of spectra for circular and ring apertures. [Figure 6]
[0011] This figure shows an example circular aperture and an example ring aperture, along with their corresponding excited optical modes. [Figure 7]
[0012] This figure shows different examples of ring openings with different shapes. [Figure 8]
[0013] This figure shows different examples of ring openings with different surface characteristics. [Figure 9]
[0014] This figure shows different examples of ring openings with different surface etchings. [Figure 10]
[0015] This figure shows an example of an opening having multiple concentric rings. [Modes for carrying out the invention]
[0007]
[0016] Vertical-cavity surface-emitting lasers (VCSELs) are optical devices typically used as laser sources in a variety of implementations, such as in optical transceivers used within optical networks or systems. VCSELs typically employ a semiconductor laser diode-based structure configured to emit a laser beam perpendicularly from the upper surface of the structure (either upward emission, i.e., outward from the structure, or downward emission, i.e., inward from or into the structure).
[0008]
[0017] Various designs and / or structures can be used to implement VCSELs, each employing a separate mechanism to achieve current confinement and photoconfinement. Commonly, current confinement can be achieved by a lateral oxidation process that implements both current and photoconfinement. Other methods used to confine current and light include ion implantation and etching, as well as / or implementing photonic crystal structures. Another possible solution for implementing both current and photoconfinement is to grow the epitaxial structure forming the VCSEL in two steps, with the first step ending the growth by tunnel junction, which is then patterned by lithography and etching. Subsequently, a second epitaxial growth (overgrowth) process may complete the epitaxial structure. Finally, the VCSEL is manufactured by a standard fabrication process.
[0009]
[0018] Compared to other embodiments, embedded tunnel junction (TJ) VCSELs generally exhibit strong refractive index confinement due to the steps induced by TJ etching. This affects the mode characteristics excited by the resulting structure, resulting in a larger spectral width.
[0010]
[0019] The solutions disclosed herein concern VCSELs in which angularly reduced modes are excited to narrow the mode-frequency spacing and lower the thermal resistance. This can be achieved by utilizing a ring-shaped opening. In this regard, as used herein, the terms “ring” or “ring shape” refer to an opening defined by the space between two concentric, non-intersecting boundaries of any shape. For example, if the boundaries are concentric, the ring opening takes the shape of a ring.
[0011]
[0020] The use of a ring-shaped aperture can have many benefits and / or advantages. In this regard, for the same aperture area, heat dissipated inside the cavity spreads over a wider area, reducing the junction operating temperature. Implementations according to this disclosure may operate in single mode through periodic patterning of the ring width or specific patterning of surface relief features. The combination of ring aperture patterning and mode filtering allows scaling of the aperture area and thus power while still maintaining the possibility of obtaining single-mode emission by selecting one mode with any azimuthal order. Thus, the use of a ring aperture in embodiments according to this disclosure may make it possible to achieve coherent single-mode emission while maintaining the benefits of a larger aperture. Exemplary embodiments and related details are described in more detail below.
[0012]
[0021] Figure 1 shows an example of a vertical-cavity surface-emitting laser (VCSEL). Figure 1 shows VCSEL100 (or a part thereof).
[0022] The VCSEL100 may comprise a semiconductor laser diode-based structure configured to emit a laser beam perpendicularly from the upper surface of the structure (either upward emission, i.e., outside the structure, or downward emission, i.e., inside or into the structure). VCSELs are commonly used as light (e.g., laser) sources, particularly in implementations such as transceivers (e.g., optical transceivers used in data centers). Conventionally, VCSELs have been DC (I dc) and alternating current (I ac ) is driven using one or both of them.
[0013]
[0023] Various designs and / or structures can be used in the VCSEL. For example, the VCSEL 100 can utilize a distributed Bragg reflector (DBR)-based structure. An exemplary DBR-based structure is shown in FIG. 1. In this regard, as shown in FIG. 1, the VCSEL 100 includes a contact 110, an upper DBR mirror (layer) 120, an active region 130, a lower DBR mirror (layer) 140, and a substrate layer 150. In this regard, as used herein, the term “layer” does not necessarily mean a single layer. Rather, some of the structures described herein as layers (e.g., DBR and active region) can include a stack of layers rather than a single layer. The DBR mirrors (layers) 120 and 140 are disposed parallel to the upper surface of the VCSEL 100 with the active region 130 disposed between the DBR mirrors 120 and 140. The active region 130 can include one or more quantum wells for laser light generation. In this regard, the active region 130 can include a multiple quantum well (MQW) layer. The active region 130 is sandwiched between two DBR mirrors and can function as a gain medium. The lower DBR mirror 140 can be disposed on the substrate layer 150, and the substrate layer 150 can be disposed on a heat sink layer (not shown) in some cases. The contact 110 is disposed on the upper DBR mirror 120. A lower contact (not shown) can also be incorporated into the structure, such as on the lower side of the VCSEL 110 (e.g., on the substrate layer 150). The contact can include, for example, a metal material or the like. In this regard, during operation of the VCSEL 110, by the drive current flowing through the contact 110 (and the lower contact if used).
[0014]
[0024] In some cases, DBR mirrors 120 and 140 may include layers that alternate between a high refractive index (RI)-based material and a low-high refractive index (RI)-based material. The thickness of each layer can be set to obtain a high reflectivity. The use of high reflectivity can be used to fill in the short axis length of the gain region. In some cases, p-type and n-type regions can be embedded between DBR mirrors 120 and 140 to form a diode junction. This can involve more complex semiconductor processing to ensure electrical contact to the active layer / region, but can eliminate power loss in the DBR structure.
[0015]
[0025] According to the present disclosure, an improved VCSEL having improved performance, particularly with respect to mode control, can be implemented. In particular, this can be done by incorporating adjustments and / or additions into the structure of the VCSEL, thereby obtaining improved performance without adding excessive cost and / or complexity. This is described in more detail below.
[0016]
[0026] In this regard, mode control in a VCSEL is essential for optimizing performance in various applications. In optical communication, single-mode or low-order multimode operation may be preferred compared to the broad multimode emission that can cause noise and wavelength dispersion in the fiber. Narrow linewidth or single-mode VCSELs can be particularly beneficial in this context, providing a narrow emission spectrum and stable output that helps minimize signal distortion after long-distance propagation. Mode control can be particularly useful for high-power VCSELs, especially in applications that require both high output power and single-mode operation. In these cases, achieving single-mode operation at high power levels presents challenges caused by thermal effects and mode instability.
[0017]
[0027] Additionally, current-excited VCSELs are often affected by non-uniform current density within the cavity. A phenomenon known as current concentration causes the current density to be higher at the edges of the aperture. This is shown and explained in more detail with respect to Figure 2. This non-uniformity reduces the overlap between the optical mode and the excited active region area, ultimately limiting the performance of the device. In the case of a single-mode VCSEL, the selected mode is usually the fundamental Gaussian mode, which can further limit the efficiency of the optical device due to the localization of peak intensity at the center of the aperture.
[0018]
[0028] Solutions based on this disclosure can address limitations and / or problems associated with conventional VCSELs, particularly by using modified apertures that result in improved performance with respect to mode control. In various embodiments based on this disclosure, a VCSEL may incorporate a ring-shaped lithography aperture-based structure to provide both current and optical confinement, with the current and optical confinement layers patterned such that the structure is single-mode along the width of the ring aperture. The refractive index contrast provided by the confinement layers allows for the promotion of modes that share the same spatial profile along the radial distribution, but their order can be defined solely by their angular intensity distribution. This is shown and explained in more detail with respect to Figure 2.
[0019]
[0029] Figure 2 shows an example circular aperture and an example ring aperture, along with their corresponding current and fundamental mode intensity profiles. Figure 2 shows a circular aperture (i.e., a conventional aperture) 200 and a ring aperture 220.
[0020]
[0030] In this regard, the ring aperture 220 is implemented in accordance with this disclosure. Furthermore, Figure 2 shows graphs 212 and 222, which illustrate the current and fundamental mode intensity profiles for the circular aperture and the ring aperture 220, respectively. As mentioned above, VCSELs incorporating conventional designs such as the circular aperture 200 may have some limitations and / or problems with respect to mode control.
[0021]
[0031] For example, as shown in Graph 212, a current-excited VCSEL incorporating a conventional aperture (e.g., circular aperture 200) may be affected by non-uniform current density within the VCSEL cavity, resulting from current concentration that makes the current density higher at the edges of the aperture, as shown in Graph 200. This non-uniformity reduces the overlap between the optical modes and the excited active region area, and if the selected mode is a fundamental Gaussian mode, this can result in localization of peak intensity at the center of the aperture, as shown in Graph 212, which can further limit the efficiency of the VCSEL.
[0022]
[0032] In implementations based on this disclosure, such as in a VCSEL incorporating a ring opening 220, mode control and current confinement can be addressed in combination. In this regard, mode selection and current confinement layers can be introduced into the VCSEL. For example, this can be done during the growth of an epitaxial layer, which includes, for example, a lower DBR, cavity, and active region, and ends with an upper layer (e.g., a tunnel junction (TJ) layer). The upper layer is then patterned, for example, by using lithography techniques, and then the remainder of the epitaxial growth is performed, and the VCSEL is finally fabricated through the fabrication process. An example VCSEL implemented based on this process is shown and described in more detail with respect to Figure 3.
[0023]
[0033] Therefore, in the implementations based on this disclosure, it may be possible to promote frequency-spacing modes that are independent of the refractive index step provided by the lithographic aperture and depend solely on the geometric shape of the patterned layer, making the design more robust and controllable. When the device is multimode, the spectral width may be reduced, facilitating transmission through optical fibers for data transmission.
[0024]
[0034] Furthermore, embodiments based on this disclosure may address mode control and optical mode overlap, such as through a ring patterning layer that simultaneously confines light and current. Molding the current confinement layer as described herein allows for modification of current injection to improve overlap with optical modes excited by the structure, as shown in Graph 222 corresponding to the ring aperture 220. In addition, heat generated within the device can be dissipated over a wide area, simultaneously, and within the same luminescent area, thus improving the thermal resistance of the entire structure. Better thermal properties and better efficiency may also improve the modulation bandwidth and reliability of the VCSEL.
[0025]
[0035] In addition, periodic width variations can enable the use of the lateral component of light to promote single-mode emission without affecting the structure's losses. Alternatively, periodic patterning of the surface relief can also be used to select specific higher-order modes. These two techniques can be combined to stabilize the single-mode operating range. Thus, it is possible to select one mode with an arbitrary angular order and not select the fundamental Gaussian mode, as this occurs for surface relief mode filters in circular or elliptical apertures. This can enable increasing the power to scale up the aperture area while maintaining a single-mode emission, thus removing the limitations imposed by the selection of the fundamental mode.
[0026]
[0036] Figure 3 shows an example VCSEL with a ring opening, and an example process for fabricating the VCSEL. Figure 3 shows VCSEL300.
[0037] VCSEL300 may be substantially similar to VCSEL100 in Figure 1 and may operate in substantially the same manner. VCSEL300 may be implemented as a GaAs-based VCSEL. However, VCSEL300 may incorporate a ring aperture implemented in accordance with this disclosure.
[0027]
[0038] In this regard, according to this disclosure, cavity structuring of a particular shape may be used to achieve or facilitate angularly reduced mode selection in optical devices (e.g., VCSELs). VCSEL300 represents a possible implementation form of the resulting device. This technique requires an “overgrowth” process, where the epitaxial layers used to fabricate the VCSEL may be grown in two steps by a suitable epitaxial growth technique such as metal-organic chemical vapor deposition (MOCVD). In this regard, as stated above, the term “layer” as used herein does not necessarily mean a single layer, and rather some of the structures described herein as layers (e.g., DBRs and active regions) may include stacks of layers rather than a single layer.
[0028]
[0039] The epitaxial structure grown in these two steps is shown in VCSEL300 as shown in Figure 3. In this regard, VCSEL300 may comprise six layers 310, 320, 330, 340, 350, and 360, each of which is described in more detail below. For simplicity, it is assumed that VCSEL300 exhibits centrosymmetry as shown in Figure 3. In particular, Figure 3 (reference a) shows a schematic diagram of the epitaxial layers grown in the first step (layers 310-350) and the second step (upper layer 360). Furthermore, Figure 3 (reference b) shows a cross-section of the complete VCSEL structure (excluding the junctions) assuming centrosymmetry, where l represents the width of the ring opening and h is the amount of height difference within the cavity. The dotted lines schematically represent different regions, and the resonant wavelengths λ0 and λ1 may differ. Further shown is a top view of the patterned layer 350, with the regions λ0 and λ1 highlighted.
[0029]
[0040] Layer 310 represents the substrate from which the first epitaxial growth begins. Layer 320 represents the lower dispersed Bragg reflection (DBR) mirror, grown on top of layer 310, followed by layer 330, which represents the cavity containing the active region schematically represented by the dashed line in Figure 3. Layer 340 completes the cavity (layer 330) and may contain a portion of the upper dispersed Bragg reflection (DBR) mirror. Layer 340 may contain the same material as the cavity (layer 330) and / or the same material as the subsequent upper layer 360. The first epitaxial growth then terminates at layer 350, which is a conductive layer, thus allowing current to pass into the device, such as from the upper contacts realized within or on top of the upper layer 360.
[0030]
[0041] In the second step, layer 350 is patterned to define refractive index confinement and create projections that confine current. This feature can be obtained by a lithography technique or process involving masking the epitaxial layer with a suitable mask (e.g., a resist), exposing it, and developing a portion of it. The exposed area is then etched to a total depth h by standard wet or dry etching techniques. The remaining mask is then removed, the surface is cleaned, and prepared for the subsequent epitaxial growth process (overgrowth). The upper layer 360 is a choice, depending on the definition of layer 340, to form or complete the upper DBR mirror. As shown in Figure 3, the upper layer 360 is grown and / or formed as a uniform layer and is not patterned like layer 350. In this regard, layer 360 can either be fully epitaxially grown or first epitaxially grown (e.g., partially) and then completed with a deposited material. Nevertheless, the full 360 layers still consist of DBR pairs in both methods.
[0031]
[0042] In this regard, as used in this specification, “uniform layer” means that the layer is at least uniform in thickness. As such, the upper layer 360 may have a uniform thickness but not be uniform in composition, and therefore may consist of multiple layers (for example, forming a DBR pair). Nevertheless, in some cases, the upper layer may also be uniform in composition, i.e., in both thickness and composition.
[0032]
[0043] This means that forming a uniform layer on top of a patterned layer / structure can be achieved and may be possible when forming a VCSEL (e.g., VCSEL 300) using the process described herein (e.g., the “overgrowth” process), but may not be possible when using other processes such as oxide VCSEL-based methods. In this regard, when using those other processes, the top layer (e.g., similar to top layer 360) may have the same shape as the patterned layer; for example, if the patterned layer has a ring shape, the top layer is formed with a similar shape and therefore has a hole in the center of the ring, and the structure is further processed. The use of oxide VCSEL-based methods may also prevent or hinder the use of lithography techniques in patterning layer 350 (e.g., into a ring shape). Once epitaxial growth is complete, the rest of VCSEL fabrication follows. The complete epitaxial layer structure after two growths is shown in Figure 3 (see reference b).
[0033]
[0044] Layer 350 may be designed and / or implemented to have high conductivity, and its patterning step creates a region where current is limited by creating a shielding barrier at the interface between layer 340 and the upper layer 360. Light can be emitted and collected from both the upper and lower sides of the entire structure.
[0034]
[0045] The patterning of layer 350 can result in two groups of regions: the main cavity and the outer cavity, where the resonant wavelengths are different, equal to λ0 and λ1, respectively, and current can flow only through the former. The difference in these wavelengths defines the effective refractive index (RI) confinement of the structure and determines the optical modes. In particular, the effective refractive index step (Δn = n0 - n1, where n0 is the effective refractive index related to λ0 and n1 is related to λ1) is obtained by the following equation:
[0035]
number
[0036] In the formula, Δn defines a supported optical mode having a given geometry, e.g., the maximum size for the induction pattern to have single-mode operation. According to this disclosure, layer 350 can be patterned in a ring shape. The width l of the ring is narrow enough to allow the structure to support a single mode radially. As such, the final structure may support multiple modes, but all these modes share the same spatial profile along the radial direction. In this regard, forming a VCSEL (e.g., VCSEL300) using a process described herein (e.g., an "overgrowth" process) may allow Δn to have a value higher than 1% (e.g., 2%), which may be impossible to achieve when using other techniques such as oxide aperture-based techniques.
[0037]
[0046] Figure 3 (reference b) shows two vertical regions defined by the etching step of the fabrication process, the central one having a width l. Considering the vertical wavelengths formed by the three adjacent regions λ0, λ1, and λ0, the maximum width l of the ring aperture for radially single-mode behavior can be calculated. In this regard, the maximum value can be estimated (for example, according to standard considerations for waveguides) by imposing a maximum value on the number V of the equivalent step refractive index waveguide obtained by the following equation.
[0038]
number
[0039]
[0047] For example, in a VCSEL with λ=850nm, the width l is approximately 1μm.
[0048] In the situation depicted in Figure 3 (reference b), the exponential contrast increases as the value of h increases. Therefore, higher h values are beneficial when stronger light confinement is required or desired, promoting a smaller mode volume and affecting overlap with the current distribution.
[0040]
[0049] Compared to other types of VCSELs (e.g., VCSELs incorporating conventional apertures), in a VCSEL designed and / or implemented based on this disclosure (e.g., incorporating an aperture with a ring-shaped design), the excited optical modes share the same radial distribution imposed by the specific patterning of layer 350, but may differ due to the angular distribution of light intensity. This is shown and explained in more detail with respect to Figure 4.
[0041]
[0050] Furthermore, it may be possible to reduce the interdependence between the spectral width and frequency separation of the optical modes emitted by the VCSEL and the refractive index step induced by the protrusions in layer 350. This is shown and explained in more detail with respect to Figure 5.
[0042]
[0051] Furthermore, the use of lithography techniques in patterning layer 350 allows for the achievement of smaller dimensions (e.g., an initial ring radius of 200 nm) than would be possible with other techniques such as oxide-based VCSELs.
[0043]
[0052] Figure 4 shows an example ring aperture and an example optical mode. Figure 4 shows a ring aperture 400 implemented in accordance with the present disclosure.
[0053] The ring aperture 400 has a ring width l. Furthermore, Figure 4 shows a schematic diagram representing the radial and angular intensity distributions of the two excited modes 402 and 404 of the ring aperture 400. As shown in Figure 4, the two excited modes 402 and 404 of the ring aperture 400 share the same radial distribution, but their angular distributions are different, with excited mode 402 having two nodes, while excited mode 404 has four nodes. The angular distributions of the two excited modes 402 and 404 are clearly shown in Graph 406. When modes are expanded to radial and angular components, the aperture structure supports only one mode in the radial component, while being multimodal in the angular component.
[0044]
[0054] Figure 5 shows example spectra of a circular aperture and a ring aperture. Figure 5 shows graph 500 of the spectra of a circular aperture (i.e., a conventional aperture) and a ring aperture implemented according to this disclosure. The apertures have the same aperture area (e.g., 7 μm). 2 ) has the same characteristics and operates under the same conditions (e.g., 5mA).
[0045]
[0055] Graph 500 contains data representing the spectral characteristics of the two apertures. In this regard, Graph 500 includes two plots corresponding to the two apertures, each plot containing data points representing the intensity level (y-axis) in decibels (dB) as a function of the wavelength of the emitted light signal.
[0046]
[0056] As shown in Graph 500, due to different settings of excited modes, the spectrum of the ring aperture is much narrower. In this regard, the use of an aperture implemented according to this disclosure (e.g., the ring aperture described with respect to Figures 3 and 4) makes it possible to reduce the interdependence between the spectral width and frequency separation of the optical modes emitted by the VCSEL incorporating the ring aperture and the refractive index provided by, for example, the protrusions in layer 350.
[0047]
[0057] Figure 6 shows example circular apertures and example ring apertures, as well as their corresponding excited optical modes. The apertures shown in Figure 6 are apertures 600 and 620.
[0058] Aperture 600 includes a circular aperture, i.e., a conventional aperture, while aperture 620 includes a ring aperture implemented according to this disclosure. Further shown in Figure 6 are the excited optical modes 602, 604, 606, and 608 for circular aperture 600, and the corresponding excited optical modes 622, 624, 626, and 628 for ring aperture 620. In this regard, the dashed lines within the excited optical modes represent the edges of the high refractive index region. Excited optical modes 602, 604, 606, and 608 represent the first, second, third, and fourth excited modes, respectively. Excited optical modes 622, 624, 626, and 628 represent transverse electromagnetic (TEM) modes. 00 TEM 10 TEM 02 TEM 11 It represents.
[0048]
[0059] In this regard, the ring shape resulting in the suppression of the main Gaussian mode can be easily obtained, for example, by the lithographic definition of layer 350, which dictates the current and refractive index confinement. In standard oxidation processes, it is not possible to define a ring-shaped aperture, and therefore circular apertures are commonly used. Figure 6 shows an example of optical modes excited in a ring aperture compared to those excited in a conventional circular (or elliptical) aperture. In the case of a ring aperture, the modes share the same radial profile but have different angular intensity distributions. On the other hand, in the case of a conventional circular aperture, the modes have a different number of nodes, and not all of them are cylindrically symmetric. This results in much larger energies and wavelength division between those modes, and therefore a much broader spectral width, compared to a ring aperture, as shown and explained above with respect to Figure 5.
[0049]
[0060] Figure 7 shows ring openings 700, 720, and 740, which are different examples of ring openings having different shapes. Opening 700 is a circular ring opening, opening 720 is an elliptical ring opening, and opening 740 is a ring opening of arbitrary shape.
[0050]
[0061] In this regard, in the various embodiments described herein, the proposed opening has a uniform circular ring shape, but the disclosure is not limited to such designs or shapes, and rather any suitable shape may be used as long as the resulting ring opening meets the required performance criteria. In particular, the shape of the opening (e.g., the shape of the upper layer 360 after etching) is not limited to a circular ring shape, and any ring shape may be used as long as, for example, the width of the ring is sufficient to ensure single-mode emission radially. In this regard, lithographic opening processes as described herein may allow the ring opening to have any shape and a width that can vary along the ring.
[0051]
[0062] Examples of different shapes that can be implemented while maintaining a ring pattern and single-mode emission are shown in Figure 7. In this regard, as mentioned above, aperture 700 has a circular ring shape, aperture 720 has an elliptical ring shape, and aperture 740 has an arbitrary shape.
[0052]
[0063] Figure 8 shows different examples of ring openings with different surface features. These are opening structures 800, 820, and 840.
[0064] Figure 8 illustrates the use of periodically patterned width and / or periodic surface relief in ring apertures implemented according to this disclosure. As shown in Figure 8, aperture structure 800 includes a ring aperture having a periodically patterned aperture width, aperture structure 820 includes a ring aperture having a periodic surface relief, and aperture structure 840 includes a ring aperture having a periodically patterned aperture width and periodic surface relief. Each of these three aperture structures is designed to select the same optical mode shown below (below the structure). In other words, an optical mode, for example, one of the shown modes, can be activated by selecting and / or using the corresponding patterning within layer 350.
[0053]
[0065] In this regard, an additional design consideration that may be used in designing the ring aperture in embodiments of this disclosure is to select one specific order for the angular modes in addition to the fundamental mode, while maintaining single-mode emission. Several designs may be implemented to achieve such angular mode selection. One such design shown in aperture structure 800 is to periodically pattern the width of the light and current confinement ring aperture. For example, the width in narrower areas may vary (e.g., from 0 to less than the ring width l).
[0054]
[0066] Additional reflections in width steps along the ring diameter may allow for the selection of modes that align with a periodic pattern, while increasing the diffraction of misaligned modes. In this technique, the light and current-confining layers can also function as mode selectors, resulting in excited optical modes schematically represented within the mode map 802. The advantage is improved side-mode suppression ratio and single-mode selection.
[0055]
[0067] Alternatively, or additionally, in some designs, periodic surface relief may be patterned on the upper surface (e.g., the upper surface of upper layer 360) to vary the reflectivity of the epitaxial growth stack and modulate the optical loss of the structure along the ring. Depending on the initial thickness of the upper layer (e.g., upper layer 360), the depth of the etching may determine the magnitude of the increase or decrease in loss. Etching may be performed either inside or outside the surface relief region. In this regard, cross-sections of the epitaxial structure when the upper layer (e.g., upper layer 360) can be etched inside or outside the surface relief region are shown. This is shown and explained in more detail with respect to Figure 9.
[0056]
[0068] The aperture structure 820 demonstrates the use of (only) angularly periodic surface relief patterning, where the relief is configured to repeat at constant angular intervals around the aperture to match one particular higher-order mode supported by the ring structure, without periodically patterning the width of the optical and current-confining ring aperture. The aperture structure 820 results in excited optical modes schematically represented in the mode map 822. Nevertheless, the shape and number of individual surface relief features are arbitrary and not limited to the specific patterning and surface relief shown in the aperture structure 820. This may include cases where the number of surface relief features is not the same as the number of lobes in the matched mode. In this technique, the imaginary part of the effective refractive index of the structure can be affected with little effect on the real part. The real part is modulated only through the removal of layer 350.
[0057]
[0069] The aperture structure 840 demonstrates a combination of two techniques, namely, periodic patterning of the width of the optical and current confinement ring aperture and patterning of an angularly periodic surface relief configured such that the relief repeats at constant angular intervals around the aperture, when both are modulated. The aperture structure 840 results in excited optical modes schematically represented in the mode map 842.
[0058]
[0070] Figure 9 shows different example ring openings with different surface etchings. Shown in Figure 9 are opening structures 900, 920, and 940.
[0059]
[0071] Figure 9 shows various alternative techniques for facilitating the use of periodic surface relief in ring openings implemented in accordance with this disclosure. As shown in Figure 9, the opening structure 900 includes a ring opening without any surface relief, the opening structure 920 includes a ring opening having periodic surface relief in which the upper surface (e.g., the upper surface of the upper layer 360) is etched inward of the angular periodic surface relief to facilitate the periodic surface relief, and the opening structure 940 includes a ring opening having periodic surface relief in which the upper surface (e.g., the upper surface of the upper layer 360) is etched outward of the angular periodic surface relief to facilitate the periodic surface relief.
[0060]
[0072] In this regard, Figure 9 shows a cross-section of the epitaxial structure, where the upper layer (e.g., upper layer 360) is not etched (opening structure 900), the upper layer is etched inside the surface relief region (opening structure 920), and the upper layer is etched outside the surface relief region (opening structure 940).
[0061]
[0073] Figure 10 shows an example opening having multiple concentric rings. Figure 10 shows an opening structure 1000 configured for use in a VCSEL to provide improved mode suction, as described herein.
[0062]
[0074] In this regard, in some embodiments, the VCSEL may be implemented with a plurality of concentric apertures, each aperture being implemented in accordance with the disclosure, i.e., each aperture being modified to provide improved mode performance as described herein. The concentric apertures may be arranged such that the overlap of optical modes of the plurality of concentric apertures can be strongly increased. For example, the VCSEL may incorporate a plurality of concentric ring apertures.
[0063]
[0075] This is shown in Figure 10 by an aperture structure 1000 incorporating two concentric ring apertures. In this regard, the coupling between the two concentric ring apertures can be enhanced with respect to the laterally coupled cavity due to a higher overlap of modes in each ring aperture. As such, the overlap of optical modes in the two concentric ring apertures can be strongly increased. In this regard, the mode overlap in the concentric rings can be stronger with respect to the laterally coupled cavity. This is possible because, in the implementations according to this disclosure, the distance between the rings is smaller (e.g., as small as 200 nm), which is smaller than what may be possible with any existing conventional solutions.
[0064]
[0076] In an exemplary embodiment, a VCSEL can be implemented in which the optical mode and current confinement are defined by patterning the same layer of the resonant cavity within the epitaxial layer with a ring shape that is small enough that the ring width is single-mode along the radius. The two concentric boundaries forming the ring opening may be of any shape, as long as their width is small enough that it is single-mode along the radial direction.
[0065]
[0077] In an exemplary embodiment, a single-mode ring aperture VCSEL is implemented that allows for the selection of one specific high-angle-order mode in which power can be scaled along with area.
[0066]
[0078] In an exemplary embodiment, a ring aperture VCSEL is used to obtain single-mode emission in a patterned width periodic pattern.
[0079] In an exemplary embodiment, the VCSEL may incorporate a ring opening containing an angularly periodic surface relief pattern, the relief configured to repeat around the opening at constant angular intervals. A single surface relief feature may be of any arbitrary shape.
[0067]
[0080] In an exemplary embodiment, the VCSEL may incorporate a ring aperture, the aperture width may be patterned, and a periodic surface relief may be etched to obtain single-mode emission.
[0068]
[0081] In an exemplary embodiment, the VCSEL may incorporate a plurality of (≧2) concentric ring openings, each incorporating any of the features described herein with respect to any ring openings that are joined together.
[0069]
[0082] An example optical device provided by this disclosure comprises a light source-based structure, a hollow aperture disposed on the light source-based structure, and an upper layer disposed on the hollow aperture, wherein the hollow aperture provides both current and optical confinement, and the upper layer is a uniform layer in at least thickness, and the upper layer covers at least the hollow aperture and the hollow area within the hollow aperture.
[0070]
[0083] In an exemplary embodiment, the hollow opening is patterned, while the upper layer is not patterned.
[0084] In an exemplary embodiment, the hollow opening includes a patterned feature.
[0071]
[0085] In an exemplary embodiment, the patterning feature includes a periodically patterned width feature.
[0086] In an exemplary embodiment, the upper layer includes surface features.
[0072]
[0087] In an exemplary embodiment, the surface features include one or more periodic surface relief features.
[0088] In an exemplary embodiment, the surface features correspond to and / or are related to the patterning features within the hollow opening.
[0073]
[0089] In an exemplary embodiment, the hollow opening includes a ring-shaped opening.
[0090] In an exemplary embodiment, the ring-shaped opening has a uniform or circular ring shape.
[0074]
[0091] In an exemplary embodiment, the ring-shaped opening has a non-uniform ring shape.
[0092] In an exemplary embodiment, the non-uniform ring shape includes an ellipse or any other shape.
[0075]
[0093] In an exemplary embodiment, the light source-based structure includes a vertical-cavity surface-emitting laser (VCSEL)-based structure.
[0094] In an exemplary embodiment, the VCSEL-based structure comprises a substrate layer at the bottom of the VCSEL-based structure, a lower dispersed Bragg reflection (DBR) mirror layer disposed on the substrate layer, and a cavity layer disposed on the lower DBR mirror layer, the cavity layer including an active region, and an upper DBR mirror layer disposed on the cavity layer, with each of the layers being epitaxially grown.
[0076]
[0095] An exemplary embodiment of the present disclosure includes the step of forming an optical device structure comprising a light source base structure, a hollow opening disposed on the light source base structure, and an upper layer disposed on the hollow opening, wherein the optical device structure is formed layer by layer using epitaxial growth, the hollow opening is formed to provide both current confinement and optical confinement, the upper layer is a uniform layer in at least thickness, and the upper layer covers at least the hollow opening and the hollow area within the hollow opening.
[0077]
[0096] In an exemplary embodiment, the method further includes the step of forming a hollow opening and an upper layer such that the hollow opening is patterned but the upper layer is not patterned.
[0097] In an exemplary embodiment, the method further includes the step of forming a hollow opening such that the hollow opening includes patterned features.
[0078]
[0098] In an exemplary embodiment, the patterning feature includes a periodically patterned width feature.
[0099] In an exemplary embodiment, the method further includes the step of forming an upper layer such that the upper layer includes surface features.
[0079]
[0100] In an exemplary embodiment, the surface features include one or more periodic surface relief features.
[0101] In an exemplary embodiment, the surface features correspond to and / or are related to the patterning features within the hollow opening.
[0080]
[0102] In an exemplary embodiment, the method further includes the step of forming a hollow opening such that the hollow opening includes a ring-shaped opening.
[0103] In an exemplary embodiment, the method further includes the step of forming a hollow opening such that the ring-shaped opening has a uniform or circular ring shape.
[0081]
[0104] In an exemplary embodiment, the method further includes the step of forming a hollow opening such that the ring-shaped opening has a non-uniform ring shape.
[0105] In an exemplary embodiment, the non-uniform ring shape includes an ellipse or any other shape.
[0082]
[0106] In an exemplary embodiment, the light source-based structure includes a vertical-cavity surface-emitting laser (VCSEL)-based structure, the steps of forming the VCSEL-based structure include forming a substrate layer at the bottom of the VCSEL-based structure, forming a lower dispersive Bragg reflection (DBR) mirror layer on the substrate layer, forming a cavity layer on the lower DBR mirror layer, the cavity layer including an active region, and forming an upper DBR mirror layer on the cavity layer, the multiple layers being formed layer by layer using epitaxial growth.
[0083]
[0107] As used herein, “and / or” means any one or more items in the list joined by “and / or.” For example, “x and / or y” means any element of the three-element set {(x),(y),(x,y)}. In other words, “x and / or y” means “one or both of x and y.” As another example, “x, y, and / or z” means any element of the seven-element set {(x),(y),(z),(x,y),(x,z),(y,z),(x,y,z)}. In other words, “x, y, and / or z” means “one or more of x, y, and z.” As used herein, the term “exemplary” means to serve as an unrestricted example, instance, or illustration. As used herein, the term “for example (e.g.)” is the beginning of a list of one or more unrestricted examples, instances, or illustrations.
[0084]
[0108] As used herein, the terms “circuit” and “circuitry” refer to physical electronic components (e.g., hardware), as well as any software and / or firmware ("code") that may constitute hardware, may be executed by hardware, and / or may be separately associated with hardware. As used herein, for example, certain processors and memory (e.g., volatile or non-volatile memory devices, general-purpose computer-readable media, etc.) may include a first “circuit” when executing a first one or more lines of code, and a second “circuit” when executing a second one or more lines of code. In addition, a circuit may include analog and / or digital circuits. Such circuits may, for example, operate with analog and / or digital signals. It should be understood that a circuit may be in a single device or chip, on a single motherboard, in a single chassis, in multiple enclosures in a single geographical location, in multiple enclosures distributed across multiple geographical locations, and so on. Similarly, the term “module” can refer, for example, to a physical electronic component (e.g., hardware), as well as any software and / or firmware ("code") that may constitute the hardware, may be executed by the hardware, and / or may be separately associated with the hardware.
[0085]
[0109] As used herein, a circuit or module is “operable” to perform a function whenever the circuit or module contains the hardware and code necessary to perform that function, regardless of whether the performance of that function is disabled or not enabled (e.g., by a user-configurable setting, factory trim, etc.).
[0086]
[0110] Other embodiments of the present invention may provide a non-temporary computer-readable medium and / or storage medium, and / or a non-temporary machine-readable medium and / or storage medium, which store machine code and / or a computer program having at least one code section executable by a machine and / or computer, thereby causing a machine and / or computer to perform a process as described herein.
[0087]
[0111] Various embodiments of the present invention may also be embedded in a computer program product that includes all features enabling the implementation of the methods described herein and, when loaded into a computer system, can perform these methods. In this context, computer program means any expression in any language, code, or notation of a set of instructions intended to cause a system having information processing capabilities to perform a particular function, either directly or after either a) conversion into another language, code, or notation, or b) reproduction in a different material form.
[0088]
[0112] While the Method and / or System is described with reference to a specific implementation, it will be understood by those skilled in the art that various modifications can be made and equivalents can be substituted without departing from the scope of the Method and / or System. In addition, many modifications can be made to adapt the teachings of the Disclosure to specific circumstances or materials without departing from the scope of the Disclosure. Thus, the Method and / or System is not limited to the specific implementation disclosed, however, it is intended that the Method and / or System includes all implementations that fall within the scope of the appended claims.
Claims
1. A light source-based structure, A hollow opening is disposed on the structure of the light source base, An upper layer disposed above the aforementioned hollow opening and An optical device including, The aforementioned hollow opening provides both current confinement and optical confinement. The upper layer is a uniform layer in at least thickness, The upper layer covers at least the hollow opening and the hollow region within the hollow opening, an optical device.
2. An optical device according to claim 1, wherein the hollow aperture is patterned and the upper layer is not patterned.
3. An optical device according to claim 1, wherein the hollow aperture includes a patterned feature.
4. An optical device according to claim 3, wherein the patterning feature includes a periodically patterned width feature.
5. An optical device according to claim 1, wherein the upper layer includes surface features.
6. An optical device according to claim 5, wherein the surface feature includes one or more periodic surface relief features.
7. An optical device according to claim 5, wherein the surface features are related to, or correspond to and related to, the patterning features within the hollow opening.
8. An optical device according to claim 1, wherein the hollow aperture includes a ring-shaped aperture.
9. An optical device according to claim 8, wherein the ring-shaped aperture has a uniform or circular ring shape.
10. An optical device according to claim 8, wherein the ring-shaped opening has a non-uniform ring shape.
11. An optical device according to claim 10, wherein the non-uniform ring shape includes an ellipse or any other shape.
12. An optical device according to claim 1, wherein the light source-based structure includes a vertical-cavity surface-emitting laser (VCSEL)-based structure.
13. An optical device according to claim 12, wherein the VCSEL-based structure comprises a plurality of layers, the plurality of layers comprising at least, The substrate layer at the bottom of the VCSEL-based structure, A lower dispersed Bragg reflection (DBR) mirror layer is disposed on the substrate layer, A cavity layer disposed on the lower DBR mirror layer, comprising a cavity layer including an active region, An upper DBR mirror layer disposed on the cavity layer and Includes, The aforementioned multiple layers are epitaxially grown. Optical devices.
14. A step of forming an optical device structure, wherein the optical device structure includes a light source base structure, a hollow opening disposed on the light source base structure, and an upper layer disposed on the hollow opening. A method including, The optical device structure is formed layer by layer using epitaxial growth. The hollow opening is formed to provide both current confinement and optical confinement. The upper layer is a uniform layer in at least thickness, The upper layer covers at least the hollow opening and the hollow area within the hollow opening. method.
15. A method according to claim 14, further comprising the step of forming the hollow opening and the upper layer such that the hollow opening is patterned and the upper layer is not patterned.
16. A method according to claim 14, further comprising the step of forming the hollow opening such that the hollow opening includes a patterned feature.
17. A method according to claim 16, wherein the patterning feature includes a periodically patterned width feature.
18. A method according to claim 14, further comprising the step of forming the upper layer such that the upper layer includes surface features.
19. A method according to claim 18, wherein the surface feature includes one or more periodic surface relief features.
20. A method according to claim 18, wherein the surface features are related to, or correspond to and related to, the patterning features within the hollow opening.
21. A method according to claim 14, further comprising the step of forming the hollow opening such that the hollow opening includes a ring-shaped opening.
22. A method according to claim 21, further comprising the step of forming the hollow opening such that the ring-shaped opening has a uniform or circular ring shape.
23. A method according to claim 21, further comprising the step of forming the hollow opening such that the ring-shaped opening has a non-uniform ring shape.
24. A method according to claim 23, wherein the non-uniform ring shape includes an ellipse or any other shape.
25. A method according to claim 14, wherein the light source-based structure includes a vertical-cavity surface-emitting laser (VCSEL)-based structure, and the step of forming the VCSEL-based structure is: The steps include forming a substrate layer at the bottom of the VCSEL-based structure, The steps include forming a lower dispersed Bragg reflection (DBR) mirror layer on the substrate layer, The steps include forming a cavity layer, which includes an active region, on the lower DBR mirror layer, The steps include forming an upper DBR mirror layer on the cavity layer and Includes, The aforementioned multiple layers are formed layer by layer using epitaxial growth. method.