CN117369037A

CN117369037A - Stacked gratings for optical emitters

Info

Publication number: CN117369037A
Application number: CN202310545188.7A
Authority: CN
Inventors: 朱叶雨; C-Y·卢
Original assignee: Lumentum Operations LLC
Current assignee: Lumentum Operations LLC
Priority date: 2022-07-07
Filing date: 2023-05-15
Publication date: 2024-01-09

Abstract

Some embodiments described herein may provide an optical device. The optical device may include an optical emitter and an optical element aligned with the optical emitter. The optical element may include an oxidized aperture, one or more Distributed Bragg Reflectors (DBRs) disposed on the oxidized aperture, and a stacked periodic grating structure disposed on the one or more DBRs. The stacked periodic grating structure may include a set of layers. The set of layers may comprise alternating layers of the first material and the second material. The stacked periodic grating structure may have a selected period, depth, and fill factor selected to achieve a light field confinement in a lateral direction of a light field emitted by the optical emitter that is greater than a threshold level.

Description

Stacked gratings for optical emitters

Cross Reference to Related Applications

This patent application claims priority from U.S. provisional patent application No. 63/367882 entitled "STACKED GRATINGS FOR OPTICAL EMITTERS" filed 7/2022. The disclosure of this prior application is considered to be part of the present patent application and is incorporated by reference.

Technical Field

The present disclosure relates generally to stacked gratings and optical emitters having stacked gratings.

Background

An optical emitter, such as a top-emitting Vertical Cavity Surface Emitting Laser (VCSEL), bottom-emitting VCSEL, or edge emitter, etc., may generate a set of modes, such as a fundamental mode and one or more non-fundamental modes, during emission. Some or all of the non-basic modes may be referred to as "undesired modes". When an undesired mode propagates from an optical emitter (along with the fundamental mode), the undesired mode may affect the optical performance of an optical system that includes the optical emitter. For example, the presence of an undesired mode may affect the intensity of the beam, the phase noise of the beam, the beam quality of the beam, or the Side Mode Suppression Ratio (SMSR) of the beam, etc.

Disclosure of Invention

In some embodiments, an optical device includes: an optical emitter; and an optical element aligned with the optical emitter, wherein the optical element comprises: an oxidation hole; one or more Distributed Bragg Reflectors (DBRs) disposed on the oxidized aperture; and a stacked periodic grating structure disposed on the one or more DBRs, wherein the stacked periodic grating structure comprises a set of layers, wherein the set of layers comprises alternating layers of a first material and a second material, wherein the stacked periodic grating structure has a selected period, depth, and fill factor, wherein the selected period, depth, and fill factor of the stacked periodic grating structure are selected to achieve a light field confinement in a lateral direction of a light field emitted by the optical emitter that is greater than a threshold level.

In some embodiments, a method comprises: disposing a first set of material layers on a substrate to form an emitter having an oxide aperture, wherein the first set of layers includes a first sub-set of layers of a bottom DBR and a top DBR; patterning a surface of the first set of layers to form an etched pattern; etching the etched pattern to form a subsurface periodic grating structure; and disposing a second set of material layers on the subsurface periodic grating structure, wherein the second set of material layers comprises a second subset of layers of the top DBR forming the surface periodic grating structure, wherein the surface periodic grating structure has a selected period, depth, and fill factor, and wherein the selected period, depth, and fill factor of the surface periodic grating structure are selected to achieve a light field confinement in a lateral direction of a light field emitted by the optical emitter that is greater than a threshold level.

In some embodiments, an optical element comprises: an oxidation hole; one or more DBRs disposed over the oxide aperture; and a stacked periodic grating structure formed between the first sub-set of one or more DBRs and the second sub-set of one or more DBRs, wherein the stacked periodic grating structure has a selected period, depth, and fill factor, wherein the selected period, depth, and fill factor of the stacked periodic grating structure are selected to achieve a light field confinement in a lateral direction of a light field emitted by the optical emitter that is greater than a threshold level.

Drawings

Fig. 1A and 1B are diagrams depicting example optical emitters.

Fig. 2 is a diagram of an example embodiment of a stacked grating for an optical emitter.

Fig. 3A-3C are diagrams of example embodiments of stacked gratings for an optical emitter.

Fig. 4 is a diagram of an example embodiment of a stacked grating for an optical emitter.

FIG. 5 is a flow chart of an example process associated with fabricating a stacked grating for an optical emitter.

Detailed Description

The following detailed description of example embodiments refers to the accompanying drawings. The same reference numbers in different drawings may identify the same or similar elements.

Mode competition between fundamental and other modes (e.g., non-fundamental or undesired modes) in a beam may affect the performance of an optical system in which the beam is used. For example, pattern competition may degrade communication performance, measurement accuracy, three-dimensional (3D) imaging performance, gesture recognition performance, or the like. To reduce mode competition, the oxide aperture size of the optical emitter may be reduced, which may limit unwanted modes from propagating beyond the oxide aperture of the optical emitter. However, reducing the oxide aperture size of the optical emitter may result in an increase in the current or power density of the optical emitter, which may also affect the performance of the optical emitter and the optical system.

A Distributed Bragg Reflector (DBR) structure may be provided with an optical emitter to control or limit mode propagation in the vertical direction without limiting the oxide aperture size. However, the DBR structure may not limit the undesired mode in the lateral direction. In this case, when the DBR structure is used, the lateral mode is still limited by the oxide pore size and shape. Thus, it is desirable for the optical emitter to achieve mode control in the lateral direction without limiting the oxide aperture size or shape.

Some embodiments described herein provide stacked gratings to enable mode control of an optical transmitter. For example, the stacked gratings are configured with a duty cycle, etch depth, and/or grating period to provide mode discrimination of lateral modes and suppress undesired modes below a lasing threshold (e.g., while maintaining a fundamental mode). In this way, the stacked gratings provide single transverse mode operation. Additionally or alternatively, the optical emitter may comprise a set of DBR structures that control the propagation of modes in the vertical direction. In this case, the optical emitter realizes a single mode operation based on controlling the mode propagation in the lateral direction and the vertical direction. In some embodiments, stacked gratings are capable of single mode lasers without limiting the oxide aperture size or shape. Furthermore, based on achieving single mode operation, the optical emitters achieve polarization control, which may enable the optical emitters to be used in 3D sensing applications, etc.

Fig. 1A and 1B are diagrams depicting a top view of an example optical emitter 100 and a cross-sectional view 150 of the example optical emitter 100 along line X-X, respectively. As shown in fig. 1A, optical emitter 100 may include a set of optical emitter layers constructed in an optical emitter architecture. In some embodiments, the optical emitter 100 may correspond to one or more vertical emitting devices, such as VCSELs, oxide-confined VCSELs, injection-only VCSELs, mesa VCSELs as described herein. Although optical emitter 100 is described as a vertical emitting device, it is contemplated that an edge emitting device may also be used with some implementations described herein.

As shown in fig. 1A, the optical emitter 100 may include a circular injection protection layer 102. In some embodiments, the implanted protection layer 102 may have another shape, such as an oval, a polygon, etc. The injection protection layer 102 is defined based on a space between injection material (not shown) portions included in the optical emitter 100.

As shown in fig. 1A, the optical emitter 100 includes an ohmic metal layer 104 (e.g., a P-ohm (or "P-ohm") metal layer or an N-ohm (or "N-ohm") metal layer) that is configured in a partial ring shape (e.g., having an inner radius and an outer radius). A first region of the ohmic metal layer 104 is covered by a protective layer (e.g., a dielectric layer or passivation layer) of the optical emitter 100 and a second region of the ohmic metal layer 104 is exposed by the via 106, as described below. As shown, the ohmic metal layer 104 overlaps the implant protection layer 102. For example, in the case of the P-top/top-emission optical emitter 100, such a configuration may be used. In the case of the bottom emission optical emitter 100, the configuration may be adjusted as needed.

Not shown in fig. 1A, the optical emitter 100 includes a protective layer in which the via 106 is formed (e.g., etched). A second region of the ohmic metal layer 104 is exposed by the via 106 (e.g., the shape of the dark gray region may be a result of the shape of the via 106), while a first region of the ohmic metal layer 104 is covered by some protective layer. The protective layer may cover all optical emitters except the through-holes. As shown, the via 106 is formed in a partial ring shape (e.g., similar to the ohmic metal layer 104) and is formed on the ohmic metal layer 104 such that the metallization on the protective layer contacts the ohmic metal layer 104. In some embodiments, the via 106 and/or the ohmic metal layer 104 may be formed in another shape, such as a complete ring shape or an open ring shape.

As further shown, the optical emitter 100 includes an optical aperture 108 in a portion of the optical emitter 100 within a partially annular inner diameter of the ohmic metal layer 104. The optical emitter 100 emits a laser beam through the optical aperture 108. As further shown, the optical emitter 100 also includes a current limiting aperture 110 (e.g., an "oxide aperture" or "oxide aperture" (not shown) formed by the oxide layer of the optical emitter 100). A current limiting aperture 110 is formed below the optical aperture 108.

As further shown in fig. 1A, the optical emitter 100 includes a set of trenches 112 (e.g., oxidized trenches) spaced around the circumference (e.g., equal, unequal) of the implanted protection layer 102. How closely the trenches 112 can be positioned relative to the optical aperture 108 depends on the application and is generally limited by the implant protection layer 102, the ohmic metal layer 104, the via 106, and manufacturing tolerances.

The number and arrangement of layers shown in fig. 1A are provided as examples. In practice, optical emitter 100 may include more layers, fewer layers, different layers, or layers of different arrangements than shown in FIG. 1A. For example, while the optical emitter 100 includes a set of six grooves 112, in practice, other configurations are possible, such as compact optical emitters that include five grooves 112, seven grooves 112, or other numbers of grooves. In some embodiments, the trench 112 may surround the optical emitter 100 to form a mesa structure d _t . As another example, while the optical emitter 100 is a circular optical emitter design, in practice, other designs may be used, such as rectangular optical emitters, hexagonal optical emitters, elliptical optical emitters, and the like. Additionally or alternatively, one set of layers (e.g., one or more layers) of optical emitter 100 may each perform one or more functions described as being performed by another set of layers of optical emitter 100.

In particular, while the design of the optical emitter 100 is described as including a VCSEL, other implementations are possible. For example, the design of the optical emitter 100 may be applied in the context of another type of optical device (e.g., a Light Emitting Diode (LED)) or another type of vertically emitting (e.g., top emitting or bottom emitting) optical device. Furthermore, the design of the optical emitter 100 may be applied to optical emitters of any wavelength, power level, and/or emission profile. In other words, the optical emitter 100 is not specific to an optical emitter having a given performance characteristic.

As shown in fig. 1B, an example cross-sectional view may represent a cross-section through a pair of grooves 112 or an optical emitter 100 between a pair of grooves 112 (e.g., as shown by the line labeled "X-X" in fig. 1A). As shown, the optical emitter 100 may include a backside cathode layer 128, a substrate layer 126, a bottom mirror 124, an active region 122, an oxide layer 120, a top mirror 118, an implanted isolation material 116, a protective layer 114 (e.g., dielectric passivation/mirror layer), and an ohmic metal layer 104. As shown, the optical emitter 100 may have an overall height of, for example, about 10 μm.

Backside cathode layer 128 may include a layer in electrical contact with substrate layer 126. For example, the backside cathode layer 128 may include an annealed metallization layer, such as an AuGeNi layer, a PdGeAu layer, or the like.

The substrate layer 126 may include a base substrate layer on which an epitaxial layer is grown. For example, the substrate layer 126 may include a semiconductor layer, such as a GaAs layer, an InP layer, and/or another type of semiconductor layer.

Bottom mirror 124 may include a bottom reflector layer of optical emitter 100. For example, the bottom mirror 124 may include a Distributed Bragg Reflector (DBR).

Active region 122 may include a layer that confines electrons and defines the emission wavelength of optical emitter 100. For example, active region 122 may be a quantum well.

The oxide layer 120 may include an oxide layer that provides optical and electrical confinement for the optical emitter 100. In some embodiments, the oxide layer 120 may be formed as a result of wet oxidation of the epitaxial layer. For example, the oxide layer 120 may be Al formed by oxidation of AlAs or AlGaAs layers ₂ O ₃ A layer. Trench 112 may include an opening that allows oxygen (e.g., dry oxygen, wet oxygen) to enter the epitaxial layer forming oxide layer 120.

The current confinement holes 110 may include optically active holes defined by the oxide layer 120. The current limiting aperture 110 may range in size from about 4 μm to about 20 μm, for example. In some embodiments, the size of the current limiting aperture 110 may depend on the distance between the grooves 112 surrounding the optical emitter 100. For example, trench 112 may be etched to expose formation ofAn epitaxial layer of oxide layer 120. Here, oxidation of the epitaxial layer may occur a certain distance (e.g., identified as d in fig. 1B) toward the center of the optical emitter 100 before formation (e.g., deposition) of the protective layer 114 _o ) Thereby forming the oxide layer 120 and the current limiting hole 110. In some embodiments, the current limiting aperture 110 may include an oxide aperture. Additionally or alternatively, the current confinement holes 110 may include holes associated with another type of current confinement technique, such as etched mesas, regions without ion implantation, lithographically defined intracavity mesas, regrowth, and the like. As described in more detail herein, the current limiting aperture 110 may be aligned with the stacked grating structure, which may provide mode confinement for the optical emitter 100.

The top mirror 118 may include a top reflector layer of the optical emitter 100. For example, the top mirror 118 may include a DBR.

The implant isolation material 116 may include a material that provides electrical isolation. For example, the implant isolation material 116 may include an ion implant material, such as a hydrogen/proton implant material or similar implant element, to reduce conductivity. In some embodiments, the implant isolation material 116 may define the implant protection layer 102.

The protective layer 114 may include a layer that acts as a protective passivation layer and may act as an additional DBR. For example, protective layer 114 may include one or more sub-layers (e.g., dielectric passivation layer and/or mirror layer, siO) deposited (e.g., by chemical vapor deposition, atomic layer deposition, or other techniques) on one or more other layers of optical emitter 100 ₂ Layer, si ₃ N ₄ Layer, al ₂ O ₃ Layers or other layers).

As shown, the protective layer 114 may include one or more vias 106 that provide electrical communication to the ohmic metal layer 104. For example, the through-hole 106 may be formed as an etched portion of the protective layer 114 or a peeled portion of the protective layer 114. The optical aperture 108 may include a portion of the protective layer 114 over the current limiting aperture 110 through which light may be emitted.

Ohmic metal layer 104 may include a layer that forms an electrical contact through which an electrical current may flow. For example, the ohmic metal layer 104 may include Ti and Au layers, ti and Pt layers, and/or Au layers, etc., through which current may flow (e.g., by contacting pads (not shown) of the ohmic metal layer 104 via the via 106). The ohmic metal layer 104 may be P-ohmic, N-ohmic, or other forms known in the art. The choice of the particular type of ohmic metal layer 104 may depend on the architecture of the optical emitter and is within the knowledge of one skilled in the art. The ohmic metal layer 104 may provide an ohmic contact between the metal and the semiconductor and/or may provide a non-rectifying electrical junction and/or may provide a low resistance contact.

In some embodiments, the optical emitter 100 may be manufactured using a series of steps. For example, the bottom mirror 124, the active region 122, the oxide layer 120, and the top mirror 118 may be epitaxially grown on the substrate layer 126, after which the ohmic metal layer 104 may be deposited on the top mirror 118. Next, trench 112 may be etched to expose oxide layer 120 for oxidation. The implanted isolation material 116 may be created by ion implantation, after which the protective layer 114 may be deposited. A via 106 may be etched in the protective layer 114 (e.g., exposing the ohmic metal layer 104 for contact). Electroplating, seeding, and etching may be performed, after which the substrate layer 126 may be thinned and/or ground to a target thickness. Finally, a backside cathode layer 128 may be deposited on the bottom side of the substrate layer 126.

The number, arrangement, thickness, order, symmetry, etc. of layers shown in fig. 1B are provided as examples. In practice, optical emitter 100 may include more layers, fewer layers, different layers, differently configured layers, or differently arranged layers than shown in FIG. 1B. Additionally or alternatively, a set of layers (e.g., one or more layers) of optical emitter 100 may perform one or more functions described as being performed by another set of layers of optical emitter 100, and any layer may include more than one layer.

Fig. 2 is a diagram of an example embodiment of an optical device 200 associated with a stacked grating for an optical emitter. As shown in fig. 2, the optical device 200 includes an N-plated metal (NPLT) structure 202, a first set of layers 204, a quantum well structure 206, an oxide hole 208, a second set of layers 210, and a p-ohmic metal (POM) structure 212, by cross section Y-Y.

In some embodiments, the optical device 200 may be an optical emitter, such as a VCSEL, an oxide-confined VCSEL, an injection-only VCSEL, a mesa-type VCSEL, a top-emitting VCSEL, or a bottom-emitting VCSEL, among others. Additionally or alternatively, the optical device 200 may be an edge emitter, a light emitting diode, or another type of optical emitter. In some implementations, the optical device 200 may be included in an optical system, such as an optical communication system, a gesture recognition system, a ranging system, or a 3D imaging system, among others.

The NPTL structure 202 may be an epitaxial wafer on which the first set of layers 204 is disposed to form one or more bottom DBRs. In some implementations, the NPTL structure 202 may be a gallium arsenide (GaAs) substrate or an indium phosphide (InP) substrate. The one or more bottom DBRs may include alternating layers of a first material and a second material. For example, the first set of layers 204 may include one or more first layers of relatively high refractive index material and one or more layers of relatively low refractive index material (e.g., relatively high refractive index material having a higher refractive index than relatively low refractive index material). In some embodiments, the first set of layers 204 may include one or more metal layers (e.g., aluminum, gold, or copper layers), one or more oxide layers (e.g., silicon dioxide, titanium dioxide, or tantalum oxide layers), or one or more layers of dielectric materials, etc. In some embodiments, the first set of layers 204 and/or other layers described herein may be formed from one or more thin film layers. Additionally or alternatively, the first set of layers 204 and/or other layers described herein (e.g., layers forming a periodic stacked grating structure) may be formed from other types of periodic structures, photonic crystals, supersurfaces, or the like.

The quantum well structure 206 and associated active region of the optical device 200 are disposed on one or more bottom DBRs formed by the first set of layers 204. In some implementations, the second set of layers 204 can include a first one or more top DBRs, a periodically stacked grating structure, and/or a second one or more top DBRs. In some embodiments, the second one or more top DBRs may form a periodically stacked grating structure. For example, as described in more detail herein, photolithography and wet chemical etching processes may be used to form periodic structures from a first layer or layers, and a second layer or layers may be deposited onto the periodic structures of the first layer or layers. In this case, the second one or more layers may have a periodic structure of the first one or more layers. In other words, the first one or more top DBR pairs may be patterned to form a patterned periodic grating structure, and the second one or more top DBR pairs may be deposited onto the patterned periodic grating structure. The second one or more top DBR pairs are formed with a patterned periodic grating structure based on the second one or more top DBR pairs being deposited onto the patterned periodic grating structure. This eliminates the need for etching back from the top surface.

In some embodiments, the oxidation aperture 208 may have a particular shape. For example, the oxidation holes 208 may have a circular shape or an elliptical shape. Other shapes are also contemplated. In some implementations, the oxidation holes 208 may have a size greater than a threshold size. For example, the oxidation holes 208 may be greater than 100 microns. In some embodiments, the second set of layers 210 is formed from a set of alternating layers. For example, the second set of layers 210 may have alternating relatively low refractive index layers and relatively high refractive index layers. As described above, the relatively low refractive index layer and/or the relatively high refractive index layer may be formed of a metal layer, an oxide layer, a dielectric layer, a thin film layer, or the like.

As further shown in fig. 2, the periodic stacked grating structure is periodic with respect to the first axis, indicated in top view by reference numeral 250. For example, the periodic stacked grating structure is periodic in cross-section of the optical device 200. For example, as shown, the stack varies along the x-axis, but is uniform along the z-axis. For example, the periodic stacked grating structure may limit the optical mode of the light beam emitted by the optical device 200 to a single direction. This enables lateral mode control of the optical device 200 without the need for deep etching or limiting the size of the oxide aperture.

As described above, fig. 2 is provided as an example. Other examples may differ from that described with respect to fig. 2.

Fig. 3A-3C are diagrams of example embodiments 300/300'/300″ related to stacked gratings for an optical emitter.

As shown in fig. 3A, the periodic stacked grating structure 300 includes a first portion 302, a second portion 304, and a third portion 306. The first portion 302 is disposed over an oxidized aperture of the optical emitter. The third portion 306 is disposed under the surface p-ohm metal structure of the optical emitter. The second portion 304 is disposed between the first portion 302 and the third portion 306. In fig. 3A, the first portion 302 and the third portion 306 are uniform, but the second portion 304 includes a set of stacks and gaps. Although the portions 302/304/306 are depicted separately, the portions 302/304/306 form a single periodic stacked grating structure, as shown in FIG. 3A, with non-uniform stack and gap widths. In other words, in fig. 3A, the first portion 302 is a single gap, the second portion 304 includes two stacks and two gaps on either side of the first portion 302, and the third portion 306 is a single stack on either side of the second portion 304. Thus, as shown, the periodically stacked grating structure 300 can be said to have 6 stacks and 5 gaps. Additional numbers and arrangements are contemplated.

As further shown in fig. 3A, the periodic stacked grating structure results in the top of the stack of second portions 304 being aligned with the top surface of third portions 306 and the bottom of the gaps of portions 304 being aligned with the bottom surface of first portions 302. In other words, the high refractive index layer of the first portion 302 is vertically offset from the high refractive index layer of the third portion 306, and the high refractive index layer of the second portion 304 alternates between the vertical position of the high refractive index layer of the first portion 302 and the vertical position of the high refractive index layer of the third portion 306.

Instead, as shown in fig. 3B, the first portion 302 is aligned with the third portion 306. In this case, the high refractive index layers of the second portion 304 alternate between being aligned and offset with the high refractive index layers of the first portion 302 and the third portion 306. Fig. 3C shows another configuration of a periodically stacked grating. In fig. 3C, the first portion 302 and the second portion 304 are combined into a single set of uniform stacks and gaps, and the third portion 306 surrounds the combined first portion 302 and second portion 304 with a pair of stacks. Further, as shown in fig. 3C, a high refractive index layer 308 is disposed on top of the periodically stacked grating structure, and a set of uniformly alternating layers 310 is disposed on top of the high refractive index layer 308. In this case, layers 308 and 310 may be one or more additional top DBRs, protective layers (e.g., to reduce wear on the periodically stacked grating structure), filter layers (e.g., bandpass filters to control the wavelength emitted beyond the periodically stacked grating structure), lenses (e.g., to focus the emitted light beam), or another type of optical element.

In some implementations, the periodic stacked grating structure can have periods, depths, and/or fill factors selected to achieve a light field confinement in a lateral direction of a light field emitted by the optical emitter that is greater than a threshold level. For example, as shown in fig. 3A, different periods (e.g., horizontal widths of stacks and gaps) may be used to periodically stack the grating structures to control the lateral modes. The threshold level of optical field confinement (and/or the threshold quantum cavity size or threshold mode volume described herein) may be achieved at a particular wavelength for which an optical device comprising a periodically stacked grating structure is configured. For example, the threshold level of optical field confinement may be achieved in the range of 900 nanometers (nm) to 1550 nm. The period, depth, and/or fill factor may be selected to limit the optical mode to a particular range using a periodically stacked grating structure. In other words, the optical device may have a periodically stacked grating structure having a first period, depth, and/or fill factor when used in a first wavelength range, a first amount of power, a first DBR amount, or a first oxide aperture size, etc., and may have a second period, depth, and/or fill factor when used in a second wavelength range, a second amount of power, a second DBR amount, or a second oxide aperture size.

In some embodiments, the period may be constant across the periodic stacked grating structure or may be varied across the periodic stacked grating structure. For example, the periodic stacked grating structure may have a first period (e.g., a stack having a first width) in a first portion and a second period (e.g., a stack having a second width) in a second portion. Additionally or alternatively, the periodic stacked grating structure may comprise a stacked pattern having a plurality of widths, wherein the pattern is different in different portions or in a single portion. Similarly, the depth (e.g., the difference in height between the surface of the stack and the surface of the gap) may be constant throughout the periodic stack of gratings, or may vary over or within portions to control the undesired modes. Similarly, the fill factor (e.g., the relative width of the portions that are stacks or gaps) may be constant across the periodically stacked grating structure, or multiple fill factors may occur at multiple portions of the periodically stacked grating structure. In this way, by varying the period, depth, or fill factor, etc., a threshold quantum cavity size or threshold mode volume can be achieved for the optical emitter, thereby controlling the lateral mode and/or achieving polarization control.

As described above, fig. 3A-3C are provided as examples. Other examples may differ from those described with respect to fig. 3A-3C.

Fig. 4 is a diagram of an example embodiment 400 associated with a stacked grating for an optical emitter. As further shown in fig. 4, the periodic stacked grating structure 410 is periodic about a first axis (x) and about a second axis (z) orthogonal to the first axis. This is in contrast to the optical device 200 of fig. 2, which is shown in which the optical device 200 is periodic with respect to the first axis, rather than the second axis. In some embodiments, periodic stacked grating structure 410 includes a set of shaped posts and grooves to achieve a periodic shape about two axes. For example, as shown, the set of posts may have a circular shape, and the slots may be formed around the circular posts. It is contemplated that periodic stacked grating structure 410 may be associated with another shape, such as an elliptical column, a square column, or a rectangular column. Additionally or alternatively, it is contemplated that the periodic stacked grating structure 410 is associated with a shaped groove, wherein the pillars are formed around the shaped groove. For example, the periodic stacked grating structure 410 may include circular grooves, elliptical grooves, square grooves, rectangular grooves, or the like. In this way, the periodically stacked grating structure may limit the optical mode of the light beam emitted by the optical device 200 to a single direction.

As described above, fig. 4 is provided as an example. Other examples may differ from that described with respect to fig. 4.

Fig. 5 is a flow chart of an example process 500 associated with stacking gratings for an optical transmitter. In some implementations, one or more of the process blocks of fig. 5 are performed by an apparatus (e.g., a fabrication apparatus, a lithographic apparatus, a wet chemical etching apparatus, or a deposition apparatus, etc.).

As shown in fig. 5, process 500 may include disposing a first set of material layers on a substrate to form an emitter having an oxidized aperture, wherein the first set of layers includes a first sub-set of layers of a bottom DBR and a top DBR (block 510). For example, the device may provide a first set of material layers on a substrate to form an emitter with an oxidized aperture, wherein the first set of layers includes a first sub-set of layers of a bottom DBR and a top DBR, as described above. In some embodiments, the first set of layers includes a first sub-set of layers of the bottom DBR and the top DBR.

As further shown in fig. 5, process 500 may include patterning a surface of the first set of layers to form an etched pattern (block 520). For example, the apparatus may pattern a surface of the first set of layers to form an etched pattern, as described above.

As further shown in fig. 5, process 500 may include etching the etched pattern to form a subsurface periodic grating structure (block 530). For example, the apparatus may etch the etched pattern to form a subsurface periodic grating structure, as described above.

As further shown in fig. 5, process 500 may include disposing a second set of material layers on the periodic grating structure, wherein the second set of material layers includes a second subset of layers of the top DBR forming a surface periodic grating structure, wherein the surface periodic grating structure has a selected period, depth, and fill factor, and wherein the selected period, depth, and fill factor of the surface periodic grating structure are selected to achieve a light field confinement in a lateral direction of a light field emitted by the optical emitter that is greater than a threshold level (block 540). For example, the device may provide a second set of material layers on the periodic grating structure, as described above. In some embodiments, the second set of material layers includes a second subset of layers of the top DBR that form a surface periodic grating structure. In some embodiments, the surface periodic grating structure has a selected period, depth, and fill factor. In some implementations, the selected period, depth, and fill factor of the surface periodic grating structure are selected to achieve a light field confinement in a lateral direction of the light field emitted by the optical emitter that is greater than a threshold level.

Process 500 may include additional embodiments, such as any single embodiment or any combination of embodiments described below and/or in conjunction with one or more other processes described elsewhere herein.

In a first embodiment, process 500 includes fabricating an optical emitter aligned with an oxidation aperture.

In a second embodiment, either alone or in combination with the first embodiment, the first and second sets of layers comprise alternating layers of the first and second materials.

In a third embodiment, alone or in combination with one or more of the first and second embodiments, the first set of layers forms at least one of an active region of an oxide aperture or a high aluminum content layer.

In a fourth embodiment, alone or in combination with one or more of the first through third embodiments, disposing the second set of layers comprises disposing the second set of layers using a molecular beam epitaxy process or a metal organic chemical vapor deposition process.

While fig. 5 shows example blocks of process 500, in some implementations, process 500 includes more blocks, fewer blocks, different blocks, or differently arranged blocks than those depicted in fig. 5. Additionally or alternatively, two or more blocks of process 500 may be performed in parallel.

The foregoing disclosure provides illustration and description, but is not intended to be exhaustive or to limit the embodiments to the precise form disclosed. Modifications and variations are possible in light of the above disclosure or may be acquired from practice of the embodiments. Furthermore, any of the embodiments described herein can be combined unless the foregoing disclosure explicitly provides a reason that one or more embodiments may not be combined.

As used herein, satisfying a threshold may refer to a value greater than a threshold, greater than or equal to a threshold, less than or equal to a threshold, not equal to a threshold, etc., depending on the context.

Even though particular combinations of features are recited in the claims and/or disclosed in the specification, these combinations are not intended to limit the disclosure of the various embodiments. Indeed, many of these features may be combined in ways not specifically recited in the claims and/or disclosed in the specification. Although each of the dependent claims listed below may depend directly on only one claim, the disclosure of various embodiments includes a combination of each dependent claim with each other claim in the set of claims. As used herein, a phrase referring to "at least one" of a series of items refers to any combination of those items, including individual members. For example, "at least one of a, b, or c" is intended to encompass a, b, c, a-b, a-c, b-c, and a-b-c, as well as any combination of a plurality of like items.

No element, act, or instruction used herein should be construed as critical or essential unless explicitly described as such. Furthermore, as used herein, the articles "a" and "an" are intended to include one or more items, and may be used interchangeably with "one or more". Furthermore, as used herein, the article "the" is intended to include, and be used interchangeably with, one or more items associated with the article "the. Furthermore, as used herein, the term "group" is intended to include one or more items (e.g., related items, unrelated items, or a combination of related and unrelated items), and can be used interchangeably with "one or more". If only one item is referred to, the phrase "only one" or similar language is used. Furthermore, as used herein, the term "having" and the like are intended to be open-ended terms. Furthermore, the phrase "based on" is intended to mean "based, at least in part, on" unless explicitly stated otherwise. Furthermore, as used herein, the term "or" is inclusive in a series of uses and may be used interchangeably with "and/or" unless otherwise specifically indicated (e.g., if used in conjunction with "either" or "only one"). Further, spatially relative terms, such as "below," "beneath," "above," "over," and the like, may be used herein for ease of description to describe one element or feature's relationship to another element or feature as illustrated in the figures. Spatially relative terms are intended to encompass different orientations of the device, apparatus and/or element in use or operation in addition to the orientation depicted in the figures. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

Claims

1. An optical device, comprising:

an optical emitter; and

an optical element aligned with the optical emitter,

wherein the optical element comprises:

an oxidation hole;

one or more Distributed Bragg Reflectors (DBRs) disposed on the oxidized aperture; and

a stacked periodic grating structure disposed on one or more DBRs,

wherein the stacked periodic grating structure comprises a set of layers, wherein the set of layers comprises alternating layers of a first material and a second material,

wherein the stacked periodic grating structure has a selected period, depth and fill factor,

wherein the selected period, depth and fill factor of the stacked periodic grating structure are selected to achieve a light field confinement in a lateral direction of the light field emitted by the optical emitter that is greater than a threshold level.

2. The optical device of claim 1, wherein the stacked periodic grating structure is periodic along a first axis.

3. The optical device of claim 1, wherein the stacked periodic grating structure is periodic along a first axis and a second axis orthogonal to the first axis.

4. The optical device of claim 1, wherein the selected period, depth, and fill factor are selected to achieve a threshold quantum cavity size.

5. The optical device of claim 1, wherein the selected period, depth, and fill factor are selected to achieve less than a threshold mode volume.

6. The optical device of claim 1, wherein the selected period is constant across the stacked periodic grating structure.

7. The optical device of claim 1, wherein the selected period is a first period of a first portion of the stacked periodic grating structure and a second period of a second portion of the stacked periodic grating structure, and

wherein the first period is different from the second period.

8. The optical device of claim 1, wherein the optical emitter comprises at least one of:

vertical Cavity Surface Emitting Lasers (VCSELs),

the oxide confines the VCSEL and,

only the VCSEL is implanted,

a mesa-type VCSEL,

top-emitting VCSELs, or

Bottom emitting VCSELs.

9. The optical device of claim 1, wherein the oxidation aperture comprises a circular or oval shape.

10. The optical device of claim 1, wherein the optical device is formed on a substrate, and

wherein the substrate is a gallium arsenide (GaAs) substrate or an indium phosphide (InP) substrate.

11. The optical device of claim 1, wherein the optical field confinement above a threshold level is achieved at a wavelength range of at least 900 nanometers (nm) to 1550 nm.

12. The optical device of claim 1, wherein the optical device is configured for single lateral mode operation.

13. A method, comprising:

a first set of material layers is disposed on a substrate to form an emitter having an oxidized aperture,

wherein the first set of layers comprises a first sub-set of layers of a bottom Distributed Bragg Reflector (DBR) and a top DBR;

patterning a surface of the first set of layers to form an etched pattern;

etching the etched pattern to form a subsurface periodic grating structure; and

a second set of material layers is arranged on the subsurface periodic grating structure,

wherein the second set of material layers comprises a second sub-set of layers of the top DBR forming a surface periodic grating structure,

wherein the surface periodic grating structure has a selected period, depth and fill factor, and

wherein the selected period, depth and fill factor of the surface periodic grating structure are selected to achieve a light field confinement in a lateral direction of the light field emitted by the optical emitter that is greater than a threshold level.

14. The method of claim 13, further comprising:

an optical emitter aligned with the oxidized aperture is fabricated.

15. The method of claim 13, wherein the first and second sets of layers comprise alternating layers of a first material and a second material.

16. The method of claim 13, wherein the first set of layers forms at least one of an active region or a high aluminum content layer for the oxidized aperture.

17. The method of claim 13, wherein setting the second set of layers comprises:

the second set of layers is provided using a molecular beam epitaxy process or a metal organic chemical vapor deposition process.

18. An optical element, comprising:

an oxidation hole;

a stacked periodic grating structure formed between a first sub-set of one or more DBRs and a second sub-set of one or more DBRs,

19. The optical element of claim 18, wherein the oxidation aperture is greater than a threshold size.

20. The optical element of claim 18, wherein the optical element is configured to enable polarization control of an emitter aligned with the optical element.