Mach-Zehnder interferometer with faceted mirrors

Abstract

In some embodiments, a Mach-Zehnder interferometer (MZI) includes a delay line arm formed in a chip and a mirror facet formed in the chip. The delay line arm can be configured to propagate light to the mirror facet. The mirror facet can be configured to reflect a percentage of light propagated from the delay line arm to the mirror facet back to the delay line arm.

Description

Technical Field

[0001] The present disclosure relates to Mach-Zehnder interferometers (MZIs), and for example to MZI interferometers having mirror facets. Background Art

[0002] A conventional delay line MZI includes a delay line arm and a non-delay line arm, wherein the delay line arm is longer than the non-delay line arm. Typically, the delay line MZI splits an optical signal, causing a first portion of the optical signal to propagate through the delay line arm and a second portion of the optical signal to propagate through the non-delay line arm. The delay line MZI then combines the first and second portions of the optical signal into a combined optical signal. Because the optical path of the delay line arm is longer than that of the non-delay line arm, the first portion of the optical signal is time-delayed compared to the second portion of the optical signal when combined into the combined optical signal. Summary of the Invention

[0003] In some embodiments, the MZI includes a delay line arm formed in the chip, the delay line arm configured to propagate light to a mirror facet formed in the chip; and the mirror facet is configured to reflect a certain percentage of light propagated by the delay line arm to the mirror facet to the delay line arm.

[0004] In some embodiments, the MZI includes a first mirror facet formed in the chip; a second mirror facet formed in the chip; an optical transmission element formed in the chip; a delay line waveguide formed in the chip, connected between the optical transmission element and the first mirror facet; and a non-delay line waveguide formed in the chip, connected between the optical transmission element and the second mirror facet.

[0005] In some embodiments, an optical device includes: a substrate; a first Mach-Zehnder interferometer (MZI) formed on the substrate, including: a first delay line arm, and a first mirror facet located at an end of the first delay line arm; and a second MZI formed on the substrate, including: a second delay line arm, and a second mirror facet located at an end of the second delay line arm.

[0006] In some embodiments, the MZI includes a first mirror facet; a second mirror facet; a delay line arm configured to propagate a first portion of the light beam to the first mirror facet; and a non-delay line arm configured to propagate a second portion of the light beam to the second mirror facet, wherein: a length of the delay line arm is greater than a length of the non-delay line arm; the first mirror facet is configured to reflect a certain percentage of the first portion of the light beam to the delay line arm; and the second mirror facet is configured to reflect a certain percentage of the second portion of the light beam to the non-delay line arm. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1is a diagram illustrating an example MZI described herein.

[0008] Figure 2 It shows Figure 1 Figure 2 is a cross-sectional view of a portion of an example MZI.

[0009] Figure 3 is a top view of an example trench showing the mirror facets described herein.

[0010] Figure 4 is a diagram illustrating an example MZI described herein.

[0011] Figure 5 is a schematic diagram illustrating an example optical device described herein.

[0012] Figures 6A-6C Depicted are example graphs showing the relationship between wavelength and light transmission through certain MZIs described herein.

[0013] Figures 7A-7D Depicts example optical devices and related diagrams described herein.

[0014] Figures 8A-8D Depicts example optical devices and related diagrams described herein. DETAILED DESCRIPTION

[0015] The following detailed description of example implementations refers to the accompanying drawings, in which the same reference numerals in different drawings may identify the same or similar elements.

[0016] As described above, a conventional delay line MZI (conventional delay line MZI) includes a delay line arm and a non-delay line arm, wherein the delay line arm is longer than the non-delay line arm. A first coupler of the conventional delay line MZI divides an optical signal into a first portion of the optical signal and a second portion of the optical signal, which are respectively transmitted via the delay line arm and the non-delay line arm to a second coupler, and the second coupler combines the first portion of the optical signal and the second portion of the optical signal into a combined optical signal. In some cases, such as when the conventional delay line MZI is used in applications including switches, arrayed waveguides and / or wavelength lockers (among other examples), the delay line arm can be only a few millimeters in length. However, in other cases, such as when the conventional delay line MZI is used in light detection and ranging (LIDAR) applications, the delay line arm can be several meters long (e.g., greater than one meter). Therefore, in this case, the footprint of a conventional delay line MZI can be quite large, even when a space-saving configuration is used for the delay line, such as using an interleaved spiral configuration for the delay line (e.g., two interleaved Archimedean spiral structures connected at the center by an "S-bend" waveguide). Due to the large footprint, conventional delay line MZIs may not be practically suitable for some applications that require a compact design. Furthermore, due to manufacturing limitations, when a particular application requires multiple conventional delay line MZIs, each conventional delay line MZI may need to be formed on a different substrate, which increases the complexity associated with manufacturing, assembling, and operating multiple conventional delay line MZIs. Furthermore, conventional delay line MZIs with long delay lines may require undesirable waveguide crossings, which can be avoided in some embodiments described herein.

[0017] Some embodiments described herein provide an MZI that includes a delay line arm and a non-delay line arm, wherein each arm is associated with a mirrored facet. An optical transmission element (e.g., a coupler and / or a splitter, etc.) of the MZI can be configured to provide a first portion of a light beam to the delay line arm and a second portion of the light beam to the non-delay line arm. The delay line arm can be configured to propagate the first portion of the light beam to a first mirrored facet, and the first mirrored facet can be configured to reflect a certain percentage of the first portion of the light beam to the optical transmission element via the delay line arm. The non-delay line arm can be configured to propagate the second portion of the light beam to a second mirrored facet, and the second mirrored facet can be configured to reflect a certain percentage of the second portion of the light beam to the optical transmission element via the non-delay line arm. The optical transmission element can be configured to combine the first portion of the light beam and the second portion of the light beam to generate and provide a combined light beam for output to another optical element, such as a photodiode.

[0018] Thus, for the MZI described herein, the delay line arms and non-delay line arms can have respective optical path lengths that are equal to the respective optical path lengths of the delay line arms and non-delay line arms of a conventional delay line MZI. However, it is noteworthy that, due to the respective mirror facets associated with the delay line arms and non-delay line arms of the MZI described herein, the delay line arms and non-delay line arms have respective lengths that are approximately half the respective lengths of the delay line arms and non-delay line arms of a conventional delay line MZI. Furthermore, because the respective mirror facets associated with the delay line arms and non-delay line arms of the MZI described herein reflect portions of the optical beam back to the optical transmission element, the delay line arms and non-delay line arms do not need to be connected to additional optical transmission elements (e.g., couplers) to produce a combined optical beam. Thus, the respective ends of the delay line arms and non-delay line arms (e.g., terminating with the mirror facets) can be freely positioned anywhere on the chip of the MZI described herein. This allows for independent, compact design configurations of each of the delay line arm and the non-delay line arm, which is not possible with conventional delay line MZIs, which require each of the delay line arm and the non-delay line arm to originate from a first coupler and terminate at a second coupler. This independent, compact design configuration can also avoid waveguide crossovers, such as may be necessary in the long delay line arms of conventional MZIs.

[0019] Thus, the MZIs described herein have a smaller footprint than conventional delay line MZIs that provide the same functionality (e.g., less than half the size, and in some cases less than one-third the size). Consequently, the MZIs described herein can be used in some applications where conventional delay line MZIs are not feasible (e.g., some LIDAR applications). Furthermore, the MZIs described herein allow for the formation of multiple MZIs on a single monolithic substrate (e.g., see Figure 5 ), where forming a conventional delay line MZI on a single substrate is impractical (e.g., due to the length of the delay line associated with a conventional delay line MZI, because increasing the size of the substrate to accommodate multiple conventional delay line MZIs is expensive, etc.). This reduces the complexity associated with the manufacture, assembly, and operation of the multiple MZIs described herein as compared to multiple conventional delay line MZIs.

[0020] Figure 1 is a diagram illustrating an example MZI 100 described herein. Figure 1 As shown, MZI 100 may include one or more input / outputs 102 (shown as input / output 102-1 and input / output 102-2), an optical transmission element 104, a delay line arm 106, a non-delay line arm 108, and one or more mirror facets 110 (shown as mirror facet 110-1 and mirror facet 110-2). Figure 1As shown, MZI 100 can be formed in chip 112 (e.g., formed on a single monolithic die). Chip 112 can be a planar lightwave circuit (PLC) chip, a silicon photonics chip, a silicon nitride chip, a silicon oxynitride chip, and / or a III-V semiconductor chip, among other examples (e.g., a die from a wafer or other semiconductor manufacturing process). Figure 1 As further shown, one or more reflective mirror facets 110 can be located at an interior location of chip 112. In some embodiments, one or more reflective mirror facets 110 can be located at an edge, boundary, or the like of chip 112.

[0021] In some embodiments, one or more of the input / output 102, the delay line arm 106, and / or the non-delay line arm 108 can each include an optical waveguide (e.g., a glass optical waveguide including silicon (Si), silicon dioxide (SiO2), indium phosphide (InP), and / or gallium arsenide (GaAs), among other examples) for receiving and / or transmitting light (e.g., from a light source such as a laser). The optical transmission element 104 can include a coupler, a splitter, a mixer, and / or a circulator, etc., for transmitting light from at least one input / output 102 to the delay line arm 106 and / or the non-delay line arm 108, and / or vice versa. Figure 1 As shown, the delay line arm 106 can be positioned in an arc-shaped structure; however, the layout or shape of the delay line arm 106 is not limited because the location of the end of the delay line arm 106 that terminates at the mirror facet 110-1 is not limited (for example, the mirror facet 110-1 can be located anywhere practical, and the layout of the delay line arm 106 reaching the mirror facet 110-1 can have any shape, while in a conventional delay line MZI, both ends of the delay line arm and the non-delay line arm are restricted by couplers). In addition, the length of the delay line arm 106 can be greater than the length of the non-delay line arm 108, and therefore, the optical path associated with the delay line arm 106 can be greater than the optical path associated with the non-delay line arm 108. Corresponding mirror facets 110 can be associated with the delay line arm 106 and / or the non-delay line arm 108. For example, Figure 1 As shown, the reflector facet 110-1 can be included as part of the delay line arm 106, attached to the delay line arm 106 and / or adjacent to the delay line arm 106 (e.g., at one end of the delay line arm 106), and the reflector facet 110-2 can be included as part of the non-delay line arm 108, attached to the non-delay line arm 108 and / or adjacent to the non-delay line arm 108 (e.g., at one end of the non-delay line arm 108).

[0022] In some embodiments, at least one of the one or more input / outputs 102 (e.g., input / output 102-1 and / or input / output 102-2) can be configured to receive and / or propagate a light beam to an optical transmission element 104. The optical transmission element 104 can be configured to provide a first portion of the light beam to a delay line arm 106 and a second portion of the light beam to a non-delay line arm 108.

[0023] Delay line arm 106 can be configured to propagate a first portion of the light beam to mirror facet 110-1, which can be configured to reflect a percentage of the first portion of the light beam and provide the percentage of the first portion of the light beam to delay line arm 106. Delay line arm 106 can be configured to propagate the percentage of the first portion of the light beam to optical transmission element 104. Non-delay line arm 108 can be configured to propagate a second portion of the light beam to mirror facet 110-2, which can be configured to reflect a percentage of the second portion of the light beam and provide the percentage of the second portion of the light beam to non-delay line arm 108. Non-delay line arm 108 can be configured to propagate the percentage of the second portion of the light beam to optical transmission element 104.

[0024] The optical transmission element 104 can be configured to receive the certain percentage of the first portion of the optical beam (e.g., from the delay line arm 106) and the certain percentage of the second portion of the optical beam (e.g., from the non-delay line arm 108), combine (e.g., mix or interfere) the certain percentage of the first portion of the optical beam and the certain percentage of the second portion of the optical beam to produce a combined optical beam, and provide some portion of the combined optical beam to the input / output 102 (e.g., input / output 102-1 and / or input / output 102-2). At least one input / output 102 can be configured to receive and / or propagate the combined optical beam from outside the MZI 100 (e.g., to another optical element, such as a photodiode ( Figure 1 Not shown)).

[0025] Figure 1 The number and arrangement of components shown are provided as examples. Figure 1 There may be additional components, fewer components, different components, differently arranged components, or differently connected components compared to the components shown in FIG. Figure 1 Two or more components in a can be implemented within a single component, or Figure 1 A single component shown in may be implemented as multiple distributed components. Additionally or alternatively, Figure 1 A set of components (e.g., one or more components) may perform the operations described by Figure 1 One or more functions performed by another set of components.

[0026] Figure 2 It shows Figure 1 FIG. 1 is a diagram of a cross section of a portion of an example MZI 100 . Figure 2 The cross section of FIG is longitudinally passing through a portion of arm 210 (e.g., delay line arm 106 or non-delay line arm 108) and mirror facet 110 of chip 112. Chip 112 may include one or more layers, such as substrate 202, lower cladding layer 204 (e.g., formed above substrate 202), core layer 206 (e.g., formed above lower cladding layer 204), and / or upper cladding layer 208 (e.g., formed above core layer 206). For example, as Figure 2 As shown, an upper cladding 208 can be disposed above the core 206, which can be disposed above the lower cladding 204, which can be disposed above the substrate 202. The upper cladding 208 and the lower cladding 204 can confine light within the core 206 (e.g., when the light is transmitted through the arms 210). This can be referred to as vertical light confinement. In some embodiments, the arms 210 can be the ridge of the core 206, which is surrounded by the cladding (e.g., by the upper cladding 208), or can be described as the core 206, where adjacent regions of the core 206 are doped or otherwise modified (e.g., to change the refractive index of the adjacent regions) to confine light horizontally within the waveguide. Other layer configurations of the chip 112, arms 202, or other waveguide structures are also possible.

[0027] like Figure 2 As further shown, the reflector facet 110 may include grooves 212 (in Figure 2 In some embodiments, trenches 212 may be formed (e.g., etched) in the core layer 206, the upper cladding layer 208, and at least some of the lower cladding layer 204 of the chip 112. For example, Figure 2 As shown, trenches 212 can be formed in lower cladding layer 204, core layer 206, and upper cladding layer 208. In some embodiments, trenches 212 can also be formed in at least some of substrate 202. Thus, mirror facets 110 can be etched facets. In some embodiments, trenches 212 can be formed as dicing trenches at the edge of chip 112, but additional processing steps, such as polishing, may be required.

[0028] In some embodiments, grooves 212 are configured to allow mirror facets 110 to reflect a specific percentage of light at surface 214. In some embodiments, surface 214 can reflect light due to Fresnel's law. For example, surface 214 can reflect approximately 4% of light (e.g., within a tolerance of 4% of light, such as ±0.5%) at mirror facets 110, or a loss of approximately 14 decibels (dB) (e.g., to arm 210), due to the glass-to-gas transition between arm 210 and grooves 212 (e.g., the glass-to-air transition in a non-hermetically sealed mirror facet 110, or the glass-to-nitrogen transition in a nitrogen-purged hermetically sealed mirror facet 110, among other examples). The amount of reflection can vary depending on the materials involved in grooves 212, surface 214, and / or the glass-to-gas transition.

[0029] In some embodiments, trench 212 can be metallized (e.g., to increase the amount of reflectance at surface 214). For example, after forming trench 212, a metal layer (e.g., comprising aluminum (Al), copper (Cu), gold (Au), silver (Ag), etc.) can be formed (e.g., grown, deposited, etc.) on surface 214 (e.g., the "front" surface of trench 212) and / or one or more other surfaces of trench 212. The thickness of the metal layer can be sufficiently thick (e.g., the thickness of the metal layer can meet a thickness threshold, such as a thickness threshold of 0.1 microns) so that surface 214 reflects approximately 90% (e.g., 90% of the light within a tolerance, such as ±3%) of the light reaching mirror facet 110 (e.g., via arm 210), thereby causing trench 212 to reflect approximately 90% of the light (e.g., to arm 210). Different reflection percentages are possible based on the type of metal layer and / or the thickness of the metal layer.

[0030] Additionally or alternatively, edges, borders, sides, etc. of the chip 112 of the MZI 100 can be polished and / or metallized to form the mirror facets 110. The arms of the MZI 100 (e.g., the delay line arms 106 and / or the non-delay line arms 108) can be attached and / or connected to the edges, borders, sides, etc. of the chip. The mirror facets 110 can thus reflect a specific percentage of light (e.g., 90% of the light within a tolerance, such as ±3%) that reaches the mirror facets 110 (e.g., passes through the arms).

[0031] Figure 2 The number and arrangement of components shown are provided as examples. Figure 2 There may be additional components, fewer components, different components, differently arranged components, or differently connected components compared to the components shown in FIG. Figure 2 Two or more components in a can be implemented within a single component, or Figure 2A single component shown in may be implemented as multiple distributed components. Additionally or alternatively, Figure 2 A set of components (e.g., one or more components) may perform the operations described by Figure 2 One or more functions performed by another set of components.

[0032] Figure 3 is a top view showing an example trench 212 of a mirror facet 110 described herein (eg, when the trench 212 is not metallized). Figure 3 As shown, arm 302 (e.g., delay line arm 106 or non-delay line arm 108) can be connected to groove 212 to allow light to be reflected back to arm 302 at surface 214. Figure 3 As further shown, surface 216 of groove 212 (e.g., a “back” surface of groove 212) can be angled (e.g., compared to a “front” surface 214 of groove 212 that is perpendicular to arm 302) to prevent and / or reduce light that passes through groove 212 from reflecting from surface 216 and coupling back into arm 302. Furthermore, this prevents and / or reduces light reflected at surface 216 from interfering with light reflected at surface 214 due to Fresnel reflection (e.g., as described above).

[0033] Figure 3 The number and arrangement of components shown are provided as examples. Figure 3 There may be additional components, fewer components, different components, differently arranged components, or differently connected components compared to the components shown in FIG. Figure 3 Two or more components in a can be implemented within a single component, or Figure 3 A single component shown in may be implemented as multiple distributed components. Additionally or alternatively, Figure 3 A set of components (e.g., one or more components) may perform the operations described by Figure 3 One or more functions performed by another set of components.

[0034] Figure 4 is a diagram illustrating an example MZI 400 described herein. Figure 4 As shown, the MZI 400 may include one or more input / outputs 402 (shown as input / output 402-1 and input / output 402-2), an optical transmission element 104, a delay line arm 406 and a non-delay line arm 408, and one or more mirror facets 110 (shown as mirror facet 110-1 and mirror facet 110-2). Figure 4 As shown, the MZI 400 can be formed in a chip 412 (eg, formed on a single monolithic die). The chip 412 can be a PLC chip, a silicon photonic chip, a silicon nitride chip, a silicon oxynitride chip, and / or a III-V semiconductor chip, etc. Figure 4 As further shown, one or more mirror facets 110 may be located at an interior location of chip 412 .

[0035] In some embodiments, one or more of the input / output 402, the delay line arm 406, and / or the non-delay line arm 408 can each include an optical waveguide (e.g., a glass optical waveguide including Si, SiO2, InP, and / or GaAs, among other examples) for receiving and / or transmitting light (e.g., from a light source, such as a laser, or to a receiver, such as a photodetector). As described above, the optical transmission element 104 can include a coupler, a splitter, a mixer, and / or a circulator, etc., for transmitting light from at least one input / output 402 to the delay line arm 406 and / or the non-delay line arm 408, and / or vice versa. Figure 4 As shown, delay line arm 406 can be positioned in a spiral configuration (e.g., delay line arm 406 is wound one or more times around a central point in a single spiral configuration, such as an Archimedean spiral configuration). By positioning delay line arm 406 in a spiral configuration, delay line arm 406 has a compact design (e.g., reduced size or footprint compared to existing delay line interferometers). By positioning delay line arm 406 in a spiral configuration, mirror facet 110-1 is positioned within the spiral configuration, away from the edge of MZI 400, or away from the edge of a die including MZI 400. Positioning the delay line arm in a spiral configuration that passes over other waveguides is feasible in part because the end of delay line arm 406 that terminates at mirror facet 110-1 does not need to reconnect with the end of a non-delay line arm 408 that terminates at mirror facet 110-2. This relaxed design constraint on MZI 400 allows for a more compact layout of delay line arm 406 than in conventional delay lines, without crossing over other waveguides. Furthermore, the length of the delay line arm 406 can be greater than the length of the non-delay line arm 408, and thus, the optical path associated with the delay line arm 406 can be greater than the optical path associated with the non-delay line arm 408. Corresponding mirror facets 110 can be associated with the delay line arm 406 and / or the non-delay line arm 408. For example, Figure 4 As shown, the mirror facet 110-1 can be included as part of the delay line arm 406, attached to the delay line arm 406 and / or adjacent to the delay line arm 406 (e.g., where the mirror facet is within the spiral structure of the delay line arm 406), and the mirror facet 110-2 can be included as part of the non-delay line arm 408, attached to the non-delay line arm 408 and / or adjacent to the non-delay line arm 408 (e.g., at the end of the non-delay line arm 408).

[0036] In some embodiments, at least one of the one or more input / outputs 402 (e.g., input / output 402-1 and / or input / output 402-2) can be configured to receive and / or propagate a light beam to the optical transmission element 104. The optical transmission element 104 can be configured to provide a first portion of the light beam to the delay line arm 406 and a second portion of the light beam to the non-delay line arm 408.

[0037] Delay line arm 406 can be configured to propagate a first portion of the light beam to mirror facet 110-1, which can be configured, in a similar manner as described above, to reflect a percentage of the first portion of the light beam and provide the percentage of the first portion of the light beam to delay line arm 406. Delay line arm 406 can be configured to propagate the percentage of the first portion of the light beam to optical transmission element 104. Non-delay line arm 408 can be configured to propagate a second portion of the light beam to mirror facet 110-2, which can be configured, in a similar manner as described above, to reflect a percentage of the second portion of the light beam and provide the percentage of the second portion of the light beam to non-delay line arm 408. Non-delay line arm 408 can be configured to propagate the percentage of the second portion of the light beam to optical transmission element 104.

[0038] In a similar manner as described above, the optical transmission element 104 can be configured to receive the certain percentage of the first portion of the light beam (e.g., from the delay line arm 406) and the certain percentage of the second portion of the light beam (e.g., from the non-delay line arm 408), to combine (e.g., mix or interfere) the certain percentage of the first portion of the light beam and the certain percentage of the second portion of the light beam to produce a combined light beam, and to provide portions of the combined light beam to the input / output 402 (e.g., input / output 402-1 and / or input / output 402-2). At least one input / output 402 can be configured to receive the combined light beam and / or to propagate the combined light beam to another optical element, such as a photodiode ( Figure 4 not shown).

[0039] Additionally, or alternatively, an optical splitter ( Figure 4 A power balancing optical splitter (not shown), such as a power balancing optical splitter, can be associated with the non-delay line arm 408. The optical splitter can be configured to reduce the power (e.g., optical power) of light returned from the non-delay line arm 408 to the optical transmission element 104 so that the power is balanced (e.g., equal within a tolerance) with the power (e.g., optical power) of light returned from the delay line arm 406 to the optical element 104.

[0040] Figure 4 The number and arrangement of components shown are provided as examples. Figure 4There may be additional components, fewer components, different components, differently arranged components, or differently connected components compared to the components shown in FIG. Figure 4 Two or more components in a can be implemented within a single component, or Figure 4 A single component shown in may be implemented as multiple distributed components. Additionally or alternatively, Figure 4 A set of components (e.g., one or more components) may perform the operations described by Figure 4 One or more functions performed by another set of components.

[0041] Figure 5 is a diagram illustrating an example optical device 500 described herein. Figure 5 As shown, the optical device may include an input 502 for receiving a light beam (e.g., from a laser); an input 504 for receiving an optical signal; one or more optical splitters 506 (shown as optical splitters 506-1 through 506-3); an optical mixer 508; an MZI 100 including an optical transmission element 104-1, a delay line arm 106, a non-delay line arm 108, and one or more mirror facets 110 (shown as mirror facet 110-1 and mirror facet 110-2); an MZI 400 including an optical transmission element 104-2, a delay line arm 406, a non-delay line arm 408 (including a power balancing optical splitter 506-3, a waveguide section 516, a dummy output 518, and a dummy output 519; and a dummy output 520. output) 512-1 and / or virtual output 512-2), and one or more mirror facets 110 (shown as mirror facet 110-3 and mirror facet 110-4); and / or one or more outputs 510 (shown as outputs 510-1 to 510-4). Figure 5 As shown, the optical device 500 can be formed on a chip 514. Figure 5 As further shown, one or more mirror facets 110 may be located at an interior location of chip 514 .

[0042] In some embodiments, input 502 can be configured to receive and / or transmit a light beam (e.g., from a light source, such as a laser) to beam splitter 506-1. Beam splitter 506 can be configured to split the light beam into a first beam portion and a second beam portion. In some embodiments, beam splitter 506-1 can be configured to provide the first beam portion to MZI 100 (e.g., to optical transmission element 104-1 of MZI 100) and provide the second beam portion to beam splitter 506-2.

[0043] In some embodiments, optical transmission element 104-1 of MZI 100 can be configured to provide a first portion of the first beam portion to delay line arm 106 and a second portion of the first beam portion to non-delay line arm 108. Delay line arm 106 can be configured to propagate the first portion of the first beam portion to mirror facet 110-1, which can be configured to reflect a percentage of the first portion of the first beam portion and provide the percentage of the first portion of the first beam portion to delay line arm 106. Non-delay line arm 108 can be configured to propagate the second portion of the first beam portion to mirror facet 110-2, which can be configured to reflect a percentage of the second portion of the first beam portion and provide the percentage of the second portion of the first beam portion to non-delay line arm 108.

[0044] The delay line arm 106 may be configured to propagate the percentage of the first portion of the first beam portion to the optical transmission element 104-1. The non-delay line arm 108 may be configured to propagate the percentage of the second portion of the first beam portion to the optical transmission element 104-1.

[0045] The optical transmission element 104-1 can be configured to receive the certain percentage of the first portion of the first beam portion (e.g., from the delay line arm 106) and the certain percentage of the second portion of the first beam portion (e.g., from the non-delay line arm 108), to combine (e.g., mix or interfere) the certain percentage of the first portion of the first beam portion and the certain percentage of the second portion of the first beam portion to produce a first combined beam, and to provide portions of the first combined beam to the output 510-1. The first combined beam can be received via the output 510-1 and used, for example, as a control signal for wavelength locking.

[0046] Optical splitter 506-2 can be configured to receive the second beam portion (e.g., from optical splitter 506-1) and split the second beam portion into a third beam portion and a fourth beam portion. In some embodiments, optical splitter 506-2 can be configured to provide the third beam portion to optical mixer 508 and provide the fourth beam portion to MZI 400 (e.g., to optical transmission element 104-2 of MZI 400). In some embodiments, optical splitter 506-1 and optical splitter 506-2 can be combined into a single optical splitter (e.g., using a 1×3 optical splitter or a 1×4 optical splitter) rather than as shown in FIG. Figure 5 discrete components shown.

[0047] In some embodiments, input 504 can be configured to receive and / or transmit an optical signal (e.g., from an optical information source) to optical mixer 508. In some embodiments, optical mixer 508 can be configured to combine (e.g., mix or interfere) the third beam portion with the optical signal to create a first combined optical signal and a second combined optical signal. Optical mixer 508 can be configured to provide a portion of the first combined optical signal to output 510-2 and / or provide some portion of the second combined optical signal to output 510-3. Output 510-2 can be configured to receive and / or transmit some portion of the first combined optical signal to another optical element, such as a photodiode. Output 510-3 can be configured to receive and / or transmit some portion of the second combined optical signal to another optical element, such as a photodiode.

[0048] In some embodiments, optical transmission element 104-2 of MZI 400 can be configured to split the fourth beam portion into a first portion of the fourth beam portion and a second portion of the fourth beam portion. Optical transmission element 104-2 can be configured to provide the first portion of the fourth beam portion to delay line arm 406 and provide the second portion of the fourth beam portion to non-delay line arm 408. Delay line arm 406 can be configured to propagate the first portion of the fourth beam portion to mirror facet 110-3, which can be configured to reflect a percentage of the first portion of the fourth beam portion and provide the percentage of the first portion of the fourth beam portion to delay line arm 406.

[0049] The non-delay line arm 408 can include an optical splitter 506-3 (e.g., a power balancing optical splitter) connected to the optical transmission element 104-2, a waveguide portion 516 connected between the optical splitter 506-3 and the reflector facet 110-4, and two additional waveguides connected to the virtual output 512-1 and the virtual output 512-2, respectively. The optical splitter 506-3 can be configured to split the second portion of the fourth beam portion into a first subportion of the second portion of the fourth beam portion (hereinafter referred to as the "first beam subportion") and a second subportion of the second portion of the fourth beam portion (hereinafter referred to as the "second beam subportion"). The optical splitter 506-3 can be configured to provide the first beam subportion to the waveguide portion 516. The waveguide portion 516 can be configured to propagate the first beam subportion to the reflector facet 110-4, which can be configured to reflect a certain percentage of the first beam subportion and provide the certain percentage of the first beam subportion to the waveguide portion 516. Optical splitter 506-3 can be configured to provide the second beam sub-portion to virtual output 512-1. In this manner, optical splitter 506-3 can be configured to reduce the amount of power (e.g., optical power) provided to the first beam sub-portion of waveguide portion 516 by directing a specific amount of power associated with the second beam sub-portion to virtual output 512-1.

[0050] The delay line arm 406 can be configured to propagate the certain percentage of the first portion of the fourth beam portion to the optical transmission element 104-2. The waveguide portion 516 can be configured to propagate the certain percentage of the first beam sub-portion to the optical splitter 506-3, which can be configured to split the certain percentage of the first beam sub-portion into a first percentage of the first beam sub-portion and a second percentage of the first beam sub-portion. The optical splitter 506-3 can be configured to provide the first percentage of the first beam sub-portion to the optical transmission element 104-2 and the second percentage of the first beam sub-portion to the virtual output 512-2. In this manner, the optical splitter 506-3 can be configured to facilitate balancing the power (e.g., optical power) of the certain percentage of the first portion of the fourth beam portion with the power (e.g., optical power) of the first percentage of the first beam sub-portion (e.g., such that, upon entering the optical transmission element 104-2, the amount of reflected light from the delay line arm 406 and from the non-delay line arm 408 is equal within a tolerance, as described herein).

[0051] The optical transmission element 104-2 can be configured to receive the certain percentage of the first portion of the fourth beam portion (e.g., from the delay line arm 406) and the first percentage of the first beam sub-portion (e.g., from the non-delay line arm 408 and the optical splitter 506-3), combine (e.g., mix or interfere) the certain percentage of the first portion of the fourth beam portion and the certain percentage of the first portion of the first beam sub-portion to produce a second combined beam, and provide a portion of the second combined beam to the output 510-4. The output 510-4 can be configured to receive and / or transmit the portion of the second combined beam to another optical element, such as a photodiode, and / or an optical transmission system, such as an optical discriminator, among other examples.

[0052] In some embodiments, for example, for LIDAR applications, MZI 400 can form an optical frequency discriminator, where optical power modulation is required at much smaller wavelength differences in FMCW LIDAR (Frequency Modulated Continuous Wave Light Detection and Ranging). Light from output 510-4 can be converted into an electrical signal and used to estimate the position and / or velocity information of an object. An object can be scanned by light from output 510-2 and / or output 510-3.

[0053] Figure 5 The number and arrangement of components shown are provided as examples. Figure 5 There may be additional components, fewer components, different components, differently arranged components, or differently connected components compared to the components shown in FIG. Figure 5 Two or more components in a can be implemented within a single component, or Figure 5 A single component shown in may be implemented as multiple distributed components. Additionally or alternatively, Figure 5 A set of components (e.g., one or more components) may perform the operations described by Figure 5 One or more functions performed by another set of components.

[0054] Figures 6A-6C Depicted are example graphs 600, 610, and 620 illustrating the relationship between wavelength and light transmission through a particular MZI described herein. Figure 6A As shown in graph 600, for wavelengths between 1564.6 and 1564.7 nanometers (nm), a first particular MZI having non-metallized mirror facets associated with the delay line arm and the non-delay line arm (e.g., where the delay line arm is about one meter (m) long and the delay line has an insertion loss about 7 dB greater than the non-delay line arm) has an insertion loss of about 0.05×10 -3 The modulation range. Figure 6BAs shown in graph 610, for wavelengths between 1564.6 and 1564.7 nanometers, a second particular MZI including metalized mirror facets (e.g., including an aluminum copper (AlCu) metal layer) associated with a delay line arm (e.g., where the delay line arm is approximately 1 m long and the delay line has an insertion loss approximately 7 dB greater than that of the non-delay line arm) and non-metalized mirror facets associated with the non-delay line arm has a wavelength of approximately 1.2×10 -3 The modulation range. Figure 6C As shown in graph 620, for wavelengths between 1564.4 and 1564.61 nanometers, a third particular MZI including metalized mirror facets (e.g., including an AlCu metal layer) associated with a delay line arm (e.g., where the delay line arm is approximately 6 m long and the delay line has an insertion loss approximately 9 dB greater than that of the non-delay line arm) and non-metalized mirror facets associated with the non-delay line arm has a wavelength of approximately 9×10 -3 modulation range.

[0055] As mentioned above, Figures 6A-6C One or more examples are depicted. Other examples may differ from those described herein. Figures 6A-6C described.

[0056] Figures 7A-7D Depicts an example optical device 700 and related diagrams as described herein. Figure 7A As shown, an optical device 700 can include an MZI 710 including a delay line arm 720 having a mirror facet 730 at its end. The delay line arm 720 can be positioned in a helical structure with the mirror facet 730 located within the helical structure. The delay line arm 720 can have a length of approximately 2.9 m (and the total optical length of light propagating through the MZI 710 via the delay line arm 720 can be approximately 4.2 m). The delay line arm 720 can have 94 loops in the helical structure (e.g., around the center point of the helical structure) and can have a pitch of 20 micrometers (μm) (e.g., the distance between two loops of the delay line arm 720 in the helical structure).

[0057] like Figure 7B As shown in graph 740, for wavelengths between 1564.5 and 1565 nm, when the mirror facets 730 are not metallized (e.g., light is reflected by the mirror facets via Fresnel reflection, such as due to a glass-to-gas transition), the MZI 710 has a relative high-resolution optical density of approximately 0.4×10 -3 The modulation range is about 0.11×10 -3 Power fluctuations. Figure 7CAs shown in graph 750, for wavelengths between 1564.5 and 1565 nm, when the mirror facets 730 are metallized (e.g., light is reflected by the mirror facets through a metal layer formed on the mirror facets), the MZI 710 has a wavelength of approximately 13.5×10 -3 The modulation range and wavelength are about 0.3×10 -3 Therefore, in this case, the reflector facet 730 is metallized (e.g., ) is smaller than the power fluctuation when the mirror facets are not metallized (e.g. ) is smaller. Figure 7D As shown in graph 760, MZI 710 has a free spectral range of approximately 0.57 picometers (pm) regardless of whether mirror facets 730 are unmetallized or metallized.

[0058] As mentioned above, Figures 7A-7D One or more examples are depicted. Other examples may differ from those described herein. Figures 7A-7D described.

[0059] Figures 8A-8D Depicts an example optical device 800 and related diagrams as described herein. Figure 8A As shown, the optical device 800 may include an MZI 810 including a delay line arm 820 having a reflective mirror facet 830 at its end. The delay line arm 820 may be positioned in a spiral configuration with the reflective mirror facet 830 located within the spiral configuration. Figure 8A As further shown in FIG, the delay line arm 820 can have a length of approximately 4 m (and the total optical length of light propagating through the MZI 810 via the delay line arm 820 can be approximately 6 m). The delay line arm 820 can have 88 loops in a spiral configuration (e.g., around a center point of the spiral configuration) and can have a pitch of 16 μm (e.g., the distance between two loops of the delay line arm 820 in the spiral configuration).

[0060] like Figure 8B As shown in graph 840, for wavelengths between 1564.5 and 1565 nanometers, when the mirror facets 830 are not metallized (e.g., light is reflected by the mirror facets via Fresnel reflection, such as due to a glass-to-gas transition), the MZI 810 has a relative humidity of approximately 0.25×10 -3 The modulation range is about 0.08×10 -3 Power fluctuations. Figure 8C As shown in graph 850, for wavelengths between 1564.5 and 1565 nanometers, when the mirror facets 830 are metallized (e.g., light is reflected by the mirror facets through a metal layer formed on the mirror facets), the MZI 810 has a wavelength of approximately 9.5×10-3 The modulation range is about 0.2×10 -3 Therefore, in this case, when the reflector facet 830 is metallized (e.g., ) of the modulation range compared to the power fluctuation when the mirror facets are not metallized (e.g. ) is smaller. Figure 8D As shown in graph 860, MZI 810 has a free spectral range of approximately 0.42 pm regardless of whether the mirror facets 830 are unmetallized or metallized.

[0061] As mentioned above, Figures 8A-8D One or more examples are depicted. Other examples may differ from those described herein. Figures 8A-8D described.

[0062] The foregoing disclosure provides illustration and description, but is not intended to be exhaustive or to limit the embodiments to the precise forms disclosed. Modifications and variations may be made based on the foregoing disclosure or may be derived from practice of implementation. In addition, any embodiments described herein may be combined unless the foregoing disclosure explicitly provides reasons why one or more embodiments may not be combined.

[0063] As used herein, satisfying a threshold may refer to a value greater than a threshold, greater than or equal to a threshold, less than a threshold, less than or equal to a threshold, equal to a threshold, etc., depending on the context.

[0064] As used herein, the term "layer" is intended to be broadly interpreted as one or more layers and includes layers oriented horizontally, vertically, or at other angles.

[0065] 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. In fact, many of these features can be combined in ways not specifically recited in the claims and / or disclosed in the specification. Although each dependent claim listed below may directly depend on only one claim, the disclosure of the various embodiments includes the combination of each dependent claim with every other claim in the claim set.

[0066] Unless expressly stated, any element, action or instruction used herein should not be interpreted as critical or essential. In addition, as used herein, the article "a" is intended to include one or more items and can be used interchangeably with "one or more". In addition, as used herein, the article "the" is intended to include one or more items associated with the article "the" and can be used interchangeably with "the one or more". In addition, as used herein, the term "group" is intended to include one or more items (e.g., related items, unrelated items, a combination of related and unrelated items, etc.) and can be used interchangeably with "one or more". When only one item is intended to be used, the phrase "only one" or similar language is used. In addition, as used herein, the term "having" etc. is intended to be an open term. In addition, the phrase "based on" is intended to mean "based at least in part on", unless otherwise expressly stated. In addition, as used herein, the term "or" is intended to be included when used in series and can be used interchangeably with "and / or", unless otherwise expressly stated (e.g., if used in combination with "either" or "only one of them"). Furthermore, for ease of description, spatially relative terms, such as "below," "below," "above," and "upper," may be used herein to describe the relationship of one element or feature to another element or feature 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 should be interpreted accordingly.

[0067] Related applications

[0068] This application claims priority to U.S. Provisional Patent Application No. 63 / 027,505, filed on May 20, 2020, entitled “COMPACT INTEGRATED DELAY LINE DESIGN FOR AN INTERFEROMETER,” the contents of which are incorporated herein by reference in their entirety.

Claims

1. A Mach-Zehnder interferometer (MZI), comprising: a delay line arm formed in the chip configured to propagate light to a mirror facet formed in the chip; and The mirror facet is configured to reflect a percentage of light propagating from the delay line arm to the mirror facet into the delay line arm, wherein the reflector facets include grooves, wherein the first surface of the groove is configured to reflect the certain percentage of light, and A second surface of the trench opposite to the first surface is angled and non-parallel to the first surface so as to reflect light passing through the trench away from the delay line arm.

2. The Mach-Zehnder interferometer of claim 1, wherein the mirror facets are etched facets of the chip.

3. The Mach-Zehnder interferometer of claim 1 , wherein the mirror facets are metallized to increase the percentage of light reflected at the mirror facets.

4. The Mach-Zehnder interferometer of claim 1 , wherein the delay line arms are positioned in a spiral configuration, and The reflector facets are located within the spiral structure.

5. The Mach-Zehnder interferometer of claim 1 , wherein the delay line arms are positioned in an arc-shaped configuration, and The reflector facets are located at the ends of the delay line arms.

6. The Mach-Zehnder interferometer according to claim 1, wherein: The mirror facets have a reflectivity of approximately 90%; and The other mirror facet of the non-delay line arm of the Mach-Zehnder interferometer has a reflectivity of approximately 4%.

7. A Mach-Zehnder interferometer (MZI), comprising: a first mirror facet formed in the chip; a second mirror facet formed in the chip; light transmission elements formed in the chip; a delay line waveguide formed in the chip and connected between the optical transmission element and the first mirror facet; and a non-delay line waveguide formed in the chip, connected between the optical transmission element and the second reflector facet, wherein the first reflector facet comprises a first groove, wherein the first surface of the first groove is configured to be opposite to the second surface of the first groove; The second surface forms a certain angle with the first surface and is not parallel to the first surface.

8. The Mach-Zehnder interferometer of claim 7, wherein the first trench passes through the delay line waveguide and the second mirror facet comprises a second trench passing through the non-delay line waveguide.

9. The Mach-Zehnder interferometer of claim 7, wherein the first mirror facet is metallized to increase the reflectivity of the first mirror facet, and the second mirror facet is not metallized.

10. The Mach-Zehnder interferometer according to claim 7, wherein: The non-delay line waveguide includes a power balancing optical splitter configured to reduce the optical power returned from the non-delay line waveguide to approximately match the optical power returned from the delay line.

11. The Mach-Zehnder interferometer of claim 7, wherein at least one of the first mirror facet and the second mirror facet is located at an edge of the chip.

12. The Mach-Zehnder interferometer of claim 7, wherein at least one of the first mirror facet and the second mirror facet is located within the chip and within a spiral shape formed by at least one of the delay line waveguide or the non-delay line waveguide.

13. The Mach-Zehnder interferometer according to claim 7, wherein: The first mirror facet has a reflectivity of approximately 90%; and The second mirror facet has a reflectivity of approximately 4%.

14. An optical device comprising: substrate; A first Mach-Zehnder interferometer (MZI) formed on a substrate includes: a first delay line arm, and a first mirror facet at an end of the first delay line arm; and A second Mach-Zehnder interferometer formed on a substrate, comprising: a second delay line arm, and a second mirror facet at the end of the second delay line arm, wherein at least one of the first reflector facet or the second reflector facet comprises a groove, wherein the first surface of the groove is configured to be opposite to the second surface of the groove; The second surface forms a certain angle with the first surface and is not parallel to the first surface.

15. The optical device according to claim 14, wherein: The first mirror facet is located at a first interior position on the substrate; and The second mirror facet is located at a second inner position on the substrate. The optical device of claim 14 , wherein the trench passes through the first delay line arm.

17. The optical device of claim 14, wherein the trench passes through the second delay line arm, and The trench includes a metal layer formed on one or more surfaces of the trench.

18. The optical device of claim 14, wherein the second delay line arm is positioned on the substrate in a spiral configuration.

19. The optical device of claim 14, wherein: The first mirror facet is configured to reflect a first percentage of light that propagates to the first mirror facet via the first delay line arm; and the second mirror facet being configured to reflect a second percentage of light propagating to the second mirror facet via the second delay line arm, Wherein the first percentage of light is different from the second percentage of light.

20. The optical device of claim 14, wherein: The first mirror facet has a reflectivity of approximately 90%; and The second mirror facet has a reflectivity of approximately 4%.

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