Multi-mode device for multiplexing and demultiplexing

Abstract

This disclosure relates to a multimode device for multiplexing and demultiplexing light. A configuration of an interferometric measurement device for multiplexing and demultiplexing light is disclosed. The interferometric measurement device may include a first input waveguide, a second input waveguide, an interferometric measurement waveguide, and an output waveguide. Light of a fundamental mode can be emitted into the first and second input waveguides, and the interferometric measurement waveguide can receive the fundamental mode and generate light of a higher-order mode, wherein the two modes of light can be superimposed as they propagate through the interferometric measurement waveguide. The two modes of light can be received at the output waveguide, which collapses the two modes into a single mode. Even if the wavelengths of the light are different from each other, the light propagating through the interferometric measurement device can be used to increase optical power. Additionally, the interferometric measurement device can reduce coherent noise.

Description

[0001] Cross-references to related applications

[0002] This patent application claims the benefit of U.S. Provisional Patent Application No. 63 / 248,211, filed September 24, 2021, pursuant to 35 U.S. SC §119(e), the contents of which are incorporated herein by reference in their entirety. Technical Field

[0003] This disclosure relates generally to an optical system for coupling light. More specifically, embodiments thereof relate to an optical system having waveguides that can combine or separate light. Background Technology

[0004] Typically, optical systems (such as photonic integrated circuits) can employ multiple light sources to achieve specific tasks, such as measuring various types of information. These optical systems emit light at different wavelengths, and it is desirable to multiplex and / or demultiplex this light at various points within the optical system. Space can be extremely valuable in optical systems, especially when the optical system is integrated into a device with limited available space. Therefore, it is desirable to find components that can maintain a small overall footprint while combining or separating light. Summary of the Invention

[0005] Implementations of the systems, devices, methods, and apparatuses described in this disclosure relate to an interferometric measurement device for optical combination or optical separation.

[0006] This disclosure describes an interferometric measurement apparatus for combining light from a first light source and a second light source. The interferometric measurement apparatus may include: a first input waveguide configured to receive input light from the first light source; a second input waveguide configured to receive input light from the second light source, the second input waveguide being physically separated from the first input waveguide by a gap; an interferometric measurement waveguide configured to combine the light from the first and second input waveguides; and an output waveguide physically connected to the interferometric measurement waveguide. One of the first input waveguide or the interferometric measurement waveguide may include a tapered section and a straight section adjacent to the tapered section, the tapered section combining the light from the first and second light sources.

[0007] This disclosure describes a multiplexing device. The multiplexing device may include: a first input waveguide configured to receive a single-mode light of a first wavelength; and a second input waveguide optically coupled to the first input waveguide and configured to receive the single-mode light of a second wavelength and convert the single-mode light of the second wavelength into a higher-order mode of light. The multiplexing device may further include: an interferometric waveguide optically coupled to the first input waveguide and configured to receive the single-mode light and the higher-order mode of light from the first input waveguide. Additionally, the multiplexing device may include an output waveguide optically coupled to the interferometric waveguide and configured to: convert the higher-order mode of light received from the interferometric waveguide into the single-mode light; and output combined first and second wavelength single-mode light, thereby reducing coherence noise.

[0008] Additionally, this disclosure describes a method for demultiplexing light. The method may include: receiving light of a first single mode at a first wavelength and light of a second single mode at a second wavelength from an input waveguide; receiving the first single mode light of the first wavelength and the second single mode light of the second wavelength from the input waveguide via an interferometric waveguide; generating light of a second-order mode from the interferometric waveguide; converting the second-order mode light into light of a third single mode; outputting the third single mode light of the first wavelength from a first output waveguide; and outputting the third single mode light of the second wavelength from a second output waveguide.

[0009] Furthermore, this disclosure describes an optical combining device. The optical combining device may include: a first input waveguide configured to receive a single-mode light of a first wavelength; a second input waveguide configured to receive the single-mode light of a second wavelength; an interferometric waveguide optically coupled to the first and second input waveguides and configured to convert the single-mode light of the first and second wavelengths received from the first and second input waveguides into at least two different-order modes of light; and an output waveguide optically coupled to the interferometric waveguide and configured to: convert the at least two different-order modes of light into a third single-mode light; and output the third single-mode light having a combination of the first and second wavelengths of light, thereby multiplying the optical output power of the light.

[0010] In addition to the exemplary aspects and embodiments described above, further aspects and embodiments will become apparent from the accompanying drawings and by studying the following description. Attached Figure Description

[0011] Figure 1 A block diagram of an exemplary interferometric measurement device is shown.

[0012] Figure 2A A cross-sectional top view of an exemplary interferometric measuring device configured to combine light is shown. Figure 2B A cross-sectional top view of an exemplary interferometric measuring device configured to separate light is shown.

[0013] Figures 2C to 2E A cross-sectional top view of an exemplary waveguide connector suitable for use with the interferometric measurement apparatus described herein is shown.

[0014] Figure 3A and Figure 3B It shows along Figure 2B A cross-sectional side view of an example waveguide cut by line A-A'.

[0015] Figure 4A A cross-sectional top view of an exemplary interferometric measuring device that can be used to separate or combine light in an optical system is shown. Figure 4B It shows Figure 4A An exemplary transmission curve between the input and output of an interferometric measurement device.

[0016] Figure 5A A cross-sectional top view of an exemplary interferometric measuring device that can be used to separate or combine three wavelengths of light is shown. Figure 5B It shows Figure 5A An exemplary transmission curve between the input and output of an interferometric measurement device.

[0017] The use of crosshairs or shading in the accompanying drawings is generally provided to clarify the boundaries between adjacent elements and also to improve the readability of the drawings. Therefore, the presence or absence of crosshairs or shading does not indicate or suggest any preference or requirement for a particular material, material properties, element proportions, element dimensions, commonalities of similar illustrated elements, or any other feature, property, or characteristic of any element shown in the accompanying drawings.

[0018] It should be understood that the proportions and dimensions (relative or absolute) of the various features and elements (as well as their sets and groups), and the boundaries, spacing, and positional relationships therebetween, are provided in the accompanying drawings solely to facilitate understanding of the various embodiments described herein, and are therefore unnecessarily presented or shown to measure and not intended to indicate any preference or requirement for the illustrated embodiments, in order to exclude embodiments in conjunction with them. Detailed Implementation

[0019] Reference will now be made specifically to the representative embodiments shown in the accompanying drawings. It should be understood that the following description is not intended to limit the embodiments to a single preferred embodiment. Rather, it is intended to cover alternative forms, modifications, and equivalents that may be included within the substance and scope of the embodiments defined by the appended claims.

[0020] The accompanying drawings are referenced in the following description of the examples, which illustrate specific examples that can be practiced by way of illustration. It should be understood that other examples can be used and structural changes can be made without departing from the scope of the individual examples.

[0021] Interferometric apparatuses for separating or combining two or more different wavelengths of light are described herein. The design of the interferometric apparatus can be tailored to a specific wavelength and can represent simplified options for combining or separating two wavelengths. The interferometric apparatuses described herein are typically used in optical systems employing multiple light sources. In these optical systems, it is desirable to combine light from multiple sources into a common waveguide (e.g., to facilitate routing within the optical system, routing light to a common output, etc.) or to separate one wavelength from another (e.g., for monitoring and controlling the wavelengths and / or power provided by a given one or more light sources), and therefore the system may include one or more light-splitting devices and / or one or more light-combining devices. In practice, as the number of light sources in an optical system increases, the number, size, and / or complexity of the light-splitting and light-combining devices also increase.

[0022] The interferometric apparatus described herein is particularly useful for combining or separating two or more wavelengths that are close to each other, and this can be achieved in a relatively small form factor. For example, in some cases, the optical system can be designed to include two light sources configured to emit the same target wavelength (e.g., to provide redundancy in the event of a light source failure and / or to increase the total power generated by the optical system at that wavelength). In some cases, these optical systems can tolerate some deviation from the target wavelength and still obtain virtually the same measurement results as if the measurement were performed using the target wavelength (such a precision threshold will be set based on the overall accuracy requirements of the optical system, which in turn will depend on the overall optical system design and its intended use). In these cases, it is desirable to intentionally select two light sources that emit light with different wavelengths, but such that the difference in wavelength is within acceptable tolerance. The interferometric apparatus described herein can combine these different wavelengths and can do so with a smaller footprint than could be achieved by combining multiplexers with inputs having the same wavelength.

[0023] For example, an optical system can be designed to perform measurements using a first target wavelength of light (e.g., generating the first target wavelength using one or more light sources, emitting light from the optical system at the first target wavelength, and measuring the amount returning to the optical system at the first target wavelength). The optical system can have a tolerance representing an acceptable deviation from the target wavelength at which the optical system can still perform equivalent measurements. In other words, the optical system can process light of any wavelength within the tolerance as if it were actually generated at the target wavelength. If the tolerance, as a non-limiting example, is two nanometers on either side of the target wavelength, the optical system can include two light sources configured to emit light at two different wavelengths within this range (e.g., they can be separated by less than four nanometers), and an interferometric measuring device as described herein can be used to combine these wavelengths. As mentioned above, this increases the power emitted within the acceptable limits of the target wavelength (and / or provides redundancy in the event of a light source failure) and does so with a smaller footprint.

[0024] In some cases, it is desirable to intentionally space the emitted wavelengths slightly apart by a few nanometers, as measuring with each of these wavelengths collectively reduces the effects of coherent noise in a given system. For example, in some variations, a spacing of at least three nanometers between the wavelengths emitted by the light source is desirable. By combining them using an interferometric apparatus as described herein, these wavelengths can be routed together within the system, thereby reducing the number of unique waveguides required to carry both wavelengths. Furthermore, these interferometric apparatuses may be less sensitive to variations in the manufacturing process compared to other coupling devices, such as Mach-Zehnder interferometers.

[0025] Typically, an interferometric apparatus usually includes at least one input, which is connected to at least one output via an interferometric waveguide. In a variant where the interferometric apparatus is configured to demultiplex an input having multiple wavelengths of light, the interferometric apparatus includes an input waveguide, an interferometric waveguide, and two or more output waveguides. In other cases, the interferometric apparatus may be configured to multiplex light, in which case the interferometric apparatus may include two or more input waveguides, an interferometric waveguide, and a single output. As described herein, it can be understood that the fundamental function of interferometric waveguide and optical mode coupling in an interferometric apparatus is analogous to whether the interferometric apparatus separates or combines light. That is, optical modes can still be similarly coupled from one waveguide to another, and optical modes can be generated in a similar manner.

[0026] As used throughout this specification, a reference numeral without the character α following it may refer to a corresponding reference, a group of all references, or one or more of some references. For example, "205" may refer to any one of the input waveguides 205 (e.g., input waveguide 205a, input waveguide 205b, etc.), may refer to all the input waveguides in input waveguide 205, or may refer to some of the input waveguides (e.g., one of the input waveguides in input waveguide 205a), depending on the context in which it is used.

[0027] This section describes representative applications of the methods and apparatus according to this disclosure. These examples are provided only to add context and aid in understanding. Therefore, it will be apparent to those skilled in the art that the examples can be practiced without some or all of the specific details. Other applications are possible, such that the following examples should not be considered limiting.

[0028] The following text is for reference only. Figures 1 to 5B These and other implementation schemes are discussed. However, those skilled in the art will readily understand that the detailed descriptions given herein with respect to the accompanying drawings are for illustrative purposes only and should not be construed as limiting.

[0029] Figure 1 A block diagram of an exemplary interferometric apparatus 100 that can be used in an optical system including a first light source 103a and a second light source 103b is shown. As shown, the interferometric apparatus 100 includes a first input waveguide 105a, a second input waveguide 105b, an interferometric waveguide segment 110, and an output waveguide 115. As will be described herein, the interferometric waveguide segment 110 may include one or more interferometric waveguides and may be composed of one or more segments, each with a different shape (such as straight segments, tapered segments, and / or mode-separated segments). The interferometric apparatus 100 can combine two different wavelengths of light with low optical loss, and when these wavelengths are separated by a number of nanometers (e.g., three nanometers or less, as may be determined by the acceptable tolerances discussed above), the optical system can utilize this combined light as if it were generated by a single light source with increased optical power (e.g., double the optical power) at the target wavelength. Furthermore, since the base input wavelengths are different, the coherent noise associated with measurements performed using each input wavelength can also be different, and this difference can be used to mitigate the effects of coherent noise from the resulting measurement signal.

[0030] Input waveguides 105a and 105b can receive light from the light source via an optical path that carries light from the light source to the input waveguides 105a and 105b. Typically, the optical path can be a waveguide, optical fiber, free-space optics, other light-transmitting elements, combinations thereof, etc. In other words, although the interferometric measurement device 100 can be implemented in a photonic integrated circuit, the first light source 103a and the second light source 103b do not need to be directly integrated into the same photonic integrated circuit, as long as the light from these light sources can be optically coupled into the photonic integrated circuit to reach the input waveguides 105a and 105b. For the purposes of this patent application, the first light source 103a and the second light source 103b represent light reaching the first input waveguide 105a and the second input waveguide 105b, respectively, and the actual design of the components that generate the light, route the light before it reaches the first input waveguide 105a and the second input waveguide 105b, or otherwise alter the light is unknown. That is, the optical system can preferably be configured such that the light received by each of the input waveguides 105a and 105b is light of the fundamental mode. It should also be understood that although the interferometric apparatus can be specifically designed to multiplex or demultiplex two predetermined wavelengths of light, in operation, the optical system may intermittently provide the interferometric apparatus with light at one or more wavelengths beyond the predetermined wavelengths. In these cases, the interferometric apparatus can still partially multiplex or demultiplex the light, but depending on the wavelength provided by the optical system, this may be done with significant losses or non-uniform distribution between the outputs. Although in Figure 1 The diagram shows two input waveguides 105a, 105b and two light sources 103a, 103b, but some embodiments of the interferometric apparatus described herein include three or more waveguides (such as those relative to three or more light sources) receiving light from three or more light sources. Figure 5A and Figure 5B (As described).

[0031] As mentioned above, input waveguides 105a and 105b preferably propagate light having the fundamental mode to the interferometric waveguide section 110. For each of the input waveguides 105a and 105b, the interferometric waveguide section 110 can receive light having the fundamental mode (e.g., TE00) and convert a portion of the light in the fundamental mode into light of a higher-order mode (e.g., TE10). This conversion of the light mode can be achieved in various ways, as will be referred to herein. Figures 2A to 4B As described, the interferometric waveguide section 110 converts higher-order mode light back to the fundamental mode at the output of the interferometric waveguide section 110 (i.e., at the output waveguide 115), so that the interferometric device 100 receives and outputs light in the fundamental mode. Because the fundamental mode and higher-order modes have different refractive indices within the interferometric waveguide section 110, the modes will interfere with each other as they travel within the interferometric waveguide section 110.

[0032] The relative amount of input light supplied to the input waveguide that will reach the output waveguide 115 depends on the dimensions of the interferometric waveguide section 110, the relative placement of the input and output waveguides with respect to the interferometric waveguide section 110, and the wavelength of the light received by the input waveguide. Therefore, the interferometric waveguide section 110 can be configured to maximize the transmission of a target wavelength between a given input waveguide 105a or 105b and the output waveguide 115. When the interferometric waveguide section 110 simultaneously receives light from both input waveguides 105a and 105b (e.g., a first wavelength from the first input waveguide 105a and a second wavelength from the second input waveguide 105b), the interferometric waveguide section 110 will carry both the fundamental mode and higher-order modes of the first wavelength, as well as both the fundamental mode and higher-order modes of the second wavelength. The interferometric waveguide section 110 can be configured to maximize the transmission of a first target wavelength between the first input waveguide 105a and the output waveguide 115, and is also configured to maximize the transmission of a second target wavelength between the second input waveguide 105b and the output waveguide 115, as will be discussed in more detail below.

[0033] Figure 2A A cross-sectional top view (with any layers covering the waveguides removed) of an exemplary interferometric measuring device 200 positioned within an optical system to combine light is shown. The interferometric measuring device 200 includes a first input waveguide 205a, a second input waveguide 205b, an interferometric waveguide 210, and an output waveguide 215. Similar to... Figure 1 The device includes a first input waveguide 205a and a second input waveguide 205b that can receive light in a fundamental mode (from a first light source and a second light source (not shown) of the optical system), and the received light may include a first wavelength of light received at the first input waveguide 205a, and the received light may include a second wavelength (different from the first wavelength) at the second input waveguide 205b. A cladding material 225 may surround the first input waveguide 205a and the second input waveguide 205b, the interferometry waveguide 210, and the output waveguide 215 (although the principles of this patent application will also apply to the case where air acts as the cladding layer for the waveguide). The first input waveguide 205a and the second input waveguide 205b are connected to the interferometry waveguide 210 at a first end 250a (to provide optical coupling between the input waveguide and the interferometry waveguide 210). Similarly, the output waveguide 215 is connected to the interferometry waveguide 210 at a second end 250b to optically couple the output waveguide to the interferometry waveguide. As used herein, two elements that are "optically coupled" to each other allow light to pass from one element to the other. In some embodiments, the output waveguide 215 may be a ribbed waveguide, but in other embodiments, the output waveguide 215 may be a strip waveguide.

[0034] As mentioned above, in contrast to Figure 1 As discussed, the interferometric apparatus 200 can be specifically designed to combine a first target wavelength and a second target wavelength. To achieve this, the interferometric apparatus 200 is customized to facilitate the transmission of the first target wavelength between the first input waveguide 205a and the output waveguide 215, and is also customized to facilitate the transmission of the second wavelength between the second input waveguide 205b and the output waveguide 215. As discussed above, the relative positioning between the first input waveguide 205a and the interferometric waveguide 210 will control the amount of light from the first input waveguide 205a at a given wavelength that will reach the output waveguide 215. Similarly, the relative positioning between the second input waveguide 205b and the interferometric waveguide 210 will control the amount of light from the first input waveguide 205a at a given wavelength that will reach the output waveguide 215.

[0035] The contact surface between the first input waveguide 205a and the interferometric waveguide 210 (at the first end 250a) causes a portion of the light carried by the first input waveguide 205a to convert from its fundamental mode to a higher-order mode. For light carried by the second input waveguide 205b, a similar mode conversion occurs at the contact surface between the second input waveguide 205b and the interferometric waveguide 210 (at the first end 250a). Similarly, due to the different neff (effective refractive index) between the different modes at a given wavelength, the fundamental and higher-order modes at each wavelength will interfere along the length of the interferometric waveguide 210. At the second end 250b, the contact surface between the interferometric waveguide 210 and the output waveguide 215 converts the higher-order modes of each wavelength back to their fundamental modes.

[0036] Because interference in the interferometric waveguide is wavelength-dependent, the percentage of light supplied by the input waveguides (e.g., the first input waveguide 205a or the second input waveguide 205b) that will reach the output waveguide 215 will also vary as a function of wavelength. For example, Figure 2A A graph 265 depicts the relative transmission of light between the input and output waveguides. As shown, there may be: a first transmission curve 258, representing the percentage of light (T) transmitted between the first input waveguide 205a and the output waveguide 215 as a function of wavelength (W); and a second transmission curve 260, representing the percentage of light (T) transmitted between the second input waveguide 205b and the output waveguide 215 as a function of wavelength (W). These transmission curves 258 and 260 are typically sinusoidal curves with a phase difference.

[0037] When the interferometric apparatus 200 is designed for use in a system in which the first input waveguide 205a and the second input waveguide 205b will receive (e.g., from corresponding light sources emitting these corresponding wavelengths) corresponding predetermined target wavelengths, the first input waveguide 205a and the second input waveguide 205b can each be positioned relative to the interferometric waveguide 210 along the first end 250a to maximize the light transmission to the output waveguide 215 at their respective target wavelengths. In other words, it is desirable to configure the interferometric apparatus 200 such that the first transmission curve 258 has a peak at the first target wavelength, and the second transmission curve 260 has a peak at the second wavelength. In addition to selecting the relative positions of the input waveguides 205a, 205b, changing the dimensions of the interferometric waveguide 210 (e.g., length, width, etc.) and / or changing the positioning of the output waveguide 215 along the second end 250b of the interferometric waveguide 210 can adjust the transmission curves 258, 260 (e.g., adjust the phase and / or frequency of a given transmission curve).

[0038] exist Figure 2A In the example, the interferometric waveguide 210 includes a tapered section at a first end 250a and a straight section at a second end 250b, such that the first end 250a of the interferometric waveguide 210 is wider than the second end 250b. While thinner interferometric waveguides are generally desirable (e.g., to have a smaller footprint and / or constraint mode in the waveguide), there may be practical constraints on the extent to which the first input waveguide 205a and the second input waveguide 205b can be close to each other (which in turn can limit the ability of the input waveguides to be positioned to maximize the transmission of their respective target wavelengths, especially when the target wavelengths are closer to each other). Therefore, the tapered section allows the input waveguides 205a and 205b to be positioned further apart while still maximizing the transmission of their respective target wavelengths.

[0039] When the interferometric waveguide 210 includes a tapered section, the width, length, and taper angle of the tapered section can be adjusted to modulate the transmission curves 258, 260, but are preferably selected to avoid exciting other higher-order modes. For example, the width of the first end 250a of the interferometric waveguide 210 may taper sufficiently slowly to suppress other higher-order modes of light. The first end 250a of the interferometric waveguide 210 may taper downwards from the tapered section to the straight section. Similarly, the straight section may be wide enough to allow light of the fundamental mode as well as higher-order modes to propagate through, but is preferably designed so that it does not generate additional higher-order modes or otherwise increase optical loss. In some embodiments, the tapered and straight sections of the interferometric waveguide 210 may be strip waveguides.

[0040] Interferometric waveguide 210 can be used in the system to combine light of a first wavelength with light of a second wavelength (ideally, interferometric waveguide 210 is designed to maximize transmission at both the first and second target wavelengths) and can advantageously use this combined light in the manner discussed above. For example, when measurements are performed using the combined light, the first and second wavelengths can be close enough to each other that the output light can effectively multiply the optical power output. Although the combined light technically has two different wavelengths, they can be considered equivalent from the perspective of specific measurement results because the optical system will produce the same measurement results (within acceptable limits such as those discussed above), regardless of whether the output light (for the target output intensity) includes only the first wavelength at the target output intensity, only the second wavelength at the target output intensity, or a combination of the first and second wavelengths (combined with the target output intensity). Alternatively or additionally, the first and second wavelengths can be separated by threshold quantities, allowing the optical system to use information from each wavelength to mitigate coherent noise in the measurement.

[0041] Although the interferometric device 200 is in Figure 2A The diagram shows a configuration for combining two wavelengths of light, but it should be understood that the interferometric device 200 can alternatively be used in an optical system to separate light having two wavelengths, and can be done simply by using the output waveguide 215 as the input waveguide for receiving the combined light. Figure 2B A cross-sectional top view of an exemplary interferometric apparatus 201 for separating light is shown (any layers covering the waveguide have been removed). Interferometric apparatus 201 can be identical to interferometric apparatus 200, except that light extends through interferometric apparatus 201 in the opposite direction to that of interferometric apparatus 200. By virtue of the principle of reciprocity, interferometric apparatus 201 acts as a demultiplexer, splitting an input light having a combination of a first wavelength and a second wavelength into two distinct outputs (one with the first wavelength and the other with the second wavelength).

[0042] As shown in the figure, the interferometric measurement device 201 includes an input waveguide 205, an interferometric waveguide 210, a first output waveguide 215a, and a second output waveguide 215b. The first output waveguide 215a and the second output waveguide 215b can be connected to the tapered section of the interferometric waveguide 210. It should be understood that these components can be connected as described above relative to... Figure 2A The configuration described (where) Figure 2B The input waveguide 205, interferometric waveguide 210, first output waveguide 215a, and second output waveguide 215b correspond to respectively Figure 2AThe components (output waveguide 215, interferometric waveguide 210, first input waveguide 205a, and second input waveguide 205b) are configured to maximize the transmission of a first target wavelength between input waveguide 205 and first output waveguide 215a and minimize the transmission of a first target wavelength between input waveguide 205 and second output waveguide 215b. Furthermore, these components can be configured to maximize the transmission of a second target wavelength between input waveguide 205 and second output waveguide 215b and minimize the transmission of a second target wavelength between input waveguide 205 and first output waveguide 215a. In this manner, light of the first wavelength can be coupled only to first output waveguide 215a, and light of the second wavelength can be coupled only to second output waveguide 215b.

[0043] Since the operating principle of the interferometric measuring device 201 is simply the reverse of that of the interferometric measuring device 200, it will only be described briefly here. Specifically, the input waveguide 205 is connected to the interferometric waveguide 210, such that a portion of the light of the fundamental mode of each wavelength carried by the input waveguide 205 is converted into a higher-order mode in the interferometric waveguide 210. The fundamental mode and the higher-order mode of each wavelength interfere with each other in the interferometric waveguide, and the higher-order mode of each wavelength is converted back to the fundamental mode at the connection between the interferometric waveguide 210 and each output waveguide 215a, 215b. The interferometric measuring device 200 can (as described above relative to...) Figure 2A The described waveguide is configured such that only light of the first target wavelength is transmitted into the first output waveguide (e.g., a trough exists at the second target wavelength in the transmission curve associated with the first output waveguide) and only light of the second target wavelength is transmitted into the second output waveguide 215b (e.g., a trough exists at the first target wavelength in the transmission curve associated with the second output waveguide). In this manner, light carrying the first and second target wavelengths is demultiplexed.

[0044] When the contact surface between the input or output waveguide and the interferometric waveguide is used to convert light between fundamental and higher-order modes (or vice versa), it can be accomplished in any suitable waveguide junction. For example, Figure 2C An example of a waveguide connector 202 with a bend is shown. The waveguide connector 202 includes a first segment 202a and a second segment 202b, wherein a bend 232 is present between the first segment 202a and the second segment 202b. The first segment 202a can receive input light as light in a fundamental mode. The first segment 202a and the second segment 202b can be any waveguide of the waveguide connector (e.g., an output waveguide and an interferometric waveguide) as needed to achieve the mode conversion described above.

[0045] The bend 232 can generate higher-order modes of light from the fundamental mode light via a tilt perturbation. Although the bend 232 is shown bent in a specific direction between the first and second segments 202a, 202b, the bend 232 can be in any direction, as long as a tilt perturbation can be used to generate higher-order modes. The tilt perturbation can change the boundary conditions of the light by introducing the bend 232 at the waveguide junction 202, thereby generating higher-order modes of light from the fundamental mode light. Although the first and second segments 202a and 202b are depicted as having straight sides, in some examples the waveguide segments can be bent, as long as the appropriate width of the waveguide is maintained.

[0046] Figure 2D Another example of waveguide connector 203 is shown. Similar to... Figure 2C Waveguide connector 202, Figure 2D The waveguide connector 203 may include a first segment 203a and a second segment 203b (which may be any suitable waveguide performing the mode conversion as discussed above). Figure 2D In this process, a higher-order mode can be generated due to the "knot" 233 between the first segment 203a and the second segment 203b. The knot 233 can convert light of the fundamental mode into light of a higher-order mode. The knot 233 forms a discontinuity in the waveguide width between the first segment 203a and the second segment 203b, which is responsible for generating light of a higher-order mode. The sudden change in size between the waveguide segments at the knot 233 causes light of a higher-order mode to be generated from the light of the fundamental mode received at the input. Figure 2D In the implementation scheme, the higher-order mode light can be TE10 and the basic mode light can be TE00.

[0047] Figure 2E Another example of waveguide connector 204 is shown. (Compared to...) Figure 2C and Figure 2D Same, Figure 2E The waveguide connector 204 includes a first section 204a and a second section 204b. The differences between waveguide connector 204 and waveguide connectors 202 and 203 will be described in this document.

[0048] The first segment 204a can receive input, which can be light of the basic mode that is converted into a higher-order mode (e.g., a three-lobed mode) at the junction between the first segment 204a and the second segment 204b. Figure 2EIn the process, mode conversion is generated via the tapering portion 234 of the first segment 204a. The tapering portion 234 can be fast enough that the light of the basic mode (e.g., TE00) can be at least partially converted into light of a higher-order mode (e.g., TE20). The percentage of light converted to a higher-order mode can be controlled according to the rate of the tapering portion 234 of the first segment 204a. Similarly, in Figure 2C and Figure 2D In this configuration, the bending portion 232 and the kink portion 233 can control the percentage of light converted to a higher-order mode. It is understandable that... Figure 2C , Figure 2D and Figure 2E Any waveguide connector implementation (or combination thereof) can form the above-described Figure 2A and Figure 2B The expected pattern changes discussed in the text.

[0049] Figure 3A It shows along Figure 2B The image shows a cross-sectional side view of an example waveguide 301 taken along line A-A', where no light propagates through the interferometric measuring device 201. Waveguide 301 illustrates a general structure through which light can propagate and is not drawn to scale. Waveguide 301 includes a silicon substrate 320, a first capping layer 325, a propagation layer 330, and a second capping layer 335. Figure 3B As shown, a first capping layer 325 is positioned on a silicon substrate 320, a propagation layer 330 (which may be a propagation region) is disposed on the first capping layer 325, and a second capping layer 335 is disposed on the propagation layer 330. Although Figure 3A A first cladding layer 325 and a second cladding layer 335 are depicted, but cladding layers may exist around the sides of the waveguide, as well as cladding layers above and below the cladding layers. In this embodiment, light emitted by the light source propagates to... Figure 3A The waveguide is in or away from the plane of the waveguide 301 and specifically passes through the propagation region 330 (which is the propagation layer 330). In some embodiments, the first capping layer 325 and the second capping layer 335 may be formed of oxides, such as silicon dioxide or other suitable dielectric materials.

[0050] Figure 3B It shows along Figure 2B A cross-sectional side view of an example waveguide 301 taken along line A-A' is shown, and a cross-section of the waveguide 201 is shown, through which light 350 of a single mode propagates. As previously described in Figure 2BAs discussed above, the input waveguide 205, interferometric waveguide 210, and output waveguide 215 can all support a single mode of light 350 (such as a fundamental mode of light (e.g., TE00)). Light with the fundamental mode can propagate through the input waveguide 205 and into the interferometric waveguide 210. Although the single-mode light 350 is described above as propagating through the input waveguide 205 and the interferometric waveguide 210, the interferometric waveguide 210 can support more than one fundamental mode of light. Furthermore, the light supporting the mode in the interferometric waveguide 210 can be collapsed into a single-mode light 350 in the output waveguide 215, which outputs this diagram (i.e., Figure 3B The basic pattern of light 350 is shown in the figure.

[0051] Figure 4A A cross-sectional top view of an exemplary interferometric measuring device 400 that can be used to separate or combine light in an optical system is shown (with any layers covering the waveguide removed). The interferometric measuring device 400 will be described below as being used in an optical system to combine light (e.g., for one or more of the purposes described above), but it should be understood that the interferometric measuring device 400 can alternatively be used to separate light by reciprocal operation.

[0052] like Figure 4A As shown, the interferometric measurement device 400 may include a first input waveguide 405a, a second input waveguide 405b, an interferometric waveguide segment 410 including the first interferometric waveguide 445a and the second interferometric waveguide 445b, and an output waveguide 415. A cladding material 425 may surround individual waveguides of the interferometric measurement device 400, as discussed above.

[0053] The interferometric waveguide section 410 may have a first sinusoidal transmission curve between the first input waveguide 405a and the output waveguide 415, and a second sinusoidal transmission curve between the first input waveguide 405a and the output waveguide 415. These transmission curves are... Figure 4B The common standard is shown as 402. This is in contrast to the above. Figure 2A Similar to the described interferometric measurement device 200, the interferometric waveguide section 410 can be configured to maximize the transmission of a first target wavelength from the first input waveguide 405a to the output waveguide 415 and to maximize the transmission of a second target wavelength from the second input waveguide 405b to the output waveguide 415, which facilitates the multiplexing of the first and second target wavelengths.

[0054] To facilitate light transmission between input waveguides 405a, 405b and output waveguide 415, the first interferometric waveguide 445a may include a tapered section (a first tapered section of interferometric waveguide section 410) and a straight section, while the second interferometric waveguide 445b includes a tapered section (a second tapered section of interferometric waveguide section 410). The first tapered section is connected at a first end to the first input waveguide 405a and at a second end to the straight section of the first interferometric waveguide 445a. The first input waveguide 405a may be wider than the straight section of the first interferometric waveguide 445a, such that the first tapered section narrows from its first end to its second end. The second tapered section is connected at a first end to the second input waveguide 405b and may terminate at the second end of the second tapered section. The width of the second tapered section may widen from its first end to its second end, such that the first tapered section narrows as the second tapered section widens. The first tapered section and the second tapered section can be positioned close enough to each other (e.g., separated by a predetermined gap) to allow optical coupling therebetween.

[0055] In summary, the first and second tapered sections are configured to convert a portion of the input light from each input waveguide 405a, 405b from a fundamental mode to a higher-order mode, and to transmit each input light in both the fundamental and higher-order modes to a straight section of the first interferometric waveguide 445a. For example, the first input waveguide 405a may receive light of a first wavelength in the fundamental mode. When the light of the first wavelength is transmitted to the first tapered section of the interferometric waveguide section 410, the first and second tapered sections will work together to convert a portion of the light of the first wavelength to a higher-order mode, and to transmit light of both modes to a straight section of the first interferometric waveguide 445a.

[0056] Similarly, the second input waveguide 405b can receive light of the second wavelength in the fundamental mode. When light of the first wavelength is transmitted to the first tapered section of the interferometric waveguide section 410, the first and second tapered sections work together to convert a portion of the second wavelength light into a higher-order mode, and transmit the light of both modes to the straight section of the first interferometric waveguide 445a. In this way, the straight section of the first interferometric waveguide 445a will receive light of both the fundamental and higher-order modes for each wavelength. The different modes of a given wavelength will interfere with each other in the straight section (it should be understood that some interference between modes can also occur in the tapered sections), and the higher-order modes of each wavelength can be converted back to the fundamental mode.

[0057] The transmission profile between each input waveguide 405a, 405b and the output waveguide can be determined at least partially by the dimensions and relative placement of the output waveguide 415, the first interferometric waveguide 445a, the second interferometric waveguide 445a, the first input waveguide 405a, and the second input waveguide 405b. (This is in contrast to the previous text.) Figure 2A Similar to the described interferometric measurement device 200, these components can be selected to set the transmission frequency and phase such that the first transmission curve 258 has a peak at the first target wavelength and the second transmission curve 260 has a peak at the second wavelength.

[0058] As mentioned above, the interferometric device 400 can be used in an optical system to demultiplex light instead of multiplexing light. Specifically, the output waveguide 415 can be used instead as the input waveguide, and the optical system can be configured to direct light towards the input waveguide ( Figure 4A The output waveguide 415 provides light with a first wavelength and a second wavelength. As the light propagates into the interferometric waveguide section 410, a portion of the fundamental mode for each wavelength can be converted to a higher-order mode. The fundamental and higher-order modes for each wavelength will interfere with each other within the interferometric waveguide section 410 and will be converted back to the fundamental mode in each of the first and second output waveguides (i.e., ...). Figure 4A The first input waveguide 405a and the second input waveguide 405b in the middle.

[0059] The relative amount of each wavelength ending in each output waveguide depends on the transmission curve between the input waveguide and each output waveguide. Specifically, the transmission curves can be configured (by adjusting the relative positions and dimensions of the various waveguides of the interferometric apparatus) such that the first transmission curve has a peak at the first wavelength and a trough at the second wavelength, while the second transmission curve has a trough at the first wavelength and a trough at the second wavelength, such that only the first wavelength is coupled into the first output waveguide. Therefore, the input wavelength can be demultiplexed.

[0060] As mentioned above, in some cases, the interferometric measuring apparatus described herein can be used to separate or combine three or more wavelengths of light. Figure 5A A cross-sectional top view of an exemplary interferometric measuring device 500 that can be used to separate or combine light in an optical system is shown (with any layers covering the waveguide removed). The interferometric measuring device 500 will be described below as being used in an optical system to separate light (e.g., for one or more of the purposes described above), but it should be understood that the interferometric measuring device 500 can alternatively be used to combine light by reciprocal operation.

[0061] like Figure 5AAs shown, the interferometric measurement device 500 includes an input waveguide 505, an interferometric waveguide 510, a first output waveguide 515a, a second output waveguide 515b, and a third output waveguide 515c. A cladding material 525 may surround the input waveguide 505, the interferometric waveguide 510, and the first, second, and third output waveguides 515a-515c to provide optical confinement thereto. The interferometric waveguide 510 includes a straight section 512 and a tapered section 514; however, it should be understood that variations of the interferometric waveguide 510 may include other combinations of straight sections and / or tapered sections as needed. The input waveguide 505 is connected to the straight section 512 of the interferometric waveguide 510, and the first, second, and third output waveguides 515a-515c are connected to the tapered section 514 of the interferometric waveguide 510. (As relative to...) Figure 2A and Figure 2B As discussed, the tapered section 514 increases the width of the interferometric waveguide 510 to maximize light transmission to these outputs while facilitating placement of the output waveguides 515a-515c. The width, length, and taper angle of the tapered section can be adjusted to modulate the transmission of the output waveguides 515a-515c, but are preferably selected to avoid exciting other higher-order modes.

[0062] The junction between the input waveguide 505 and the interferometric waveguide 510 is configured to generate multiple higher-order modes. Specifically, the interferometric waveguide 515 can receive input light 530 (e.g., TE00) at a given wavelength and having a fundamental mode, and converts a first portion of the fundamental mode light into light 532 (e.g., TE01) of a first higher-order mode, and a second portion of the fundamental mode light into light 534 (e.g., TE02) of a second higher-order mode. Thus, the interferometric waveguide 510 carries each of the fundamental mode light 530, the first higher-order mode light 532, and the second higher-order mode light 534.

[0063] Light of different modes at each wavelength introduced into the interferometric waveguide 510 will interfere along the length of the interferometric waveguide 510. The contact surfaces between the interferometric waveguide 510 and the output waveguides 515a-515c can convert higher-order modes of each wavelength back to their fundamental modes. Due to this wavelength dependence of interference, the percentage of light provided by the input waveguide 505 that will reach each of the output waveguides 515a-515c will also vary as a function of wavelength. Figure 5BA graph 502 is shown depicting the relative percentage of light (T) transmitted between the input waveguide 505 and the output waveguide as a function of wavelength (“W”). As shown, the first transmission curve 540a represents the percentage of light transmitted between the input waveguide 505 and the first output waveguide 515a, the second transmission curve 540b represents the percentage of light transmitted between the input waveguide 505 and the second output waveguide 515b, and the third transmission curve 540c represents the percentage of light transmitted between the input waveguide 505 and the third output waveguide 515c. These transmission curves are typically sinusoidal curves with phase difference.

[0064] The configuration of the interferometric waveguide 510 and the relative placement of the input waveguide 505 and output waveguides 515a-515c can be selected to maximize the transmission of the first wavelength to the first output waveguide 515a, maximize the transmission of the second wavelength to the second output waveguide 515b, and maximize the transmission of the third wavelength to the third output waveguide 515c. In this manner, light of the first, second, and third wavelengths can be coupled only to the first output waveguide 515a, the second output waveguide 515b, and the third output waveguide 515c, respectively. Therefore, if the interferometric apparatus 500 is used to provide light (or a subset thereof) with the first, second, and third wavelengths, this solution is multiplexed into the corresponding output waveguides.

[0065] The interferometric apparatus 500 can also be used to combine light of multiple wavelengths. For example, the interferometric apparatus 500 can be used in an optical system in which a first light source (not shown) is optically connected to a first output waveguide 515a, a second light source (not shown) is optically connected to a second output waveguide 515b, and a third light source (not shown) is optically connected to a third output waveguide 515c. In these cases, the first, second, and third output waveguides 515a-515c alternatively serve as input waveguides for receiving light from the first, second, and third light sources, respectively. The operating principle is the reverse of the separation operation described above, such that the transmission (and its corresponding wavelength) from each of these waveguides 515a-515c is maximized at the input waveguide 505 (which acts as an output waveguide during the combination operation). This results in all three wavelengths being combined in waveguide 505.

[0066] This section describes representative applications of the methods and apparatus according to this disclosure. These examples are provided only to add context and aid in understanding. Therefore, it will be apparent to those skilled in the art that the examples can be practiced without some or all of the specific details. Other applications are possible, such that the following examples should not be considered limiting.

[0067] While the disclosed examples have been fully described with reference to the accompanying drawings, it should be noted that various changes and modifications will become apparent to those skilled in the art. It should be understood that such changes and modifications are considered to be included within the scope of the disclosed examples as defined by the appended claims.

Claims

1. An interferometric measuring apparatus for combining light from a first light source, a second light source, and a third light source, comprising: A first input waveguide is configured to receive input light of a first wavelength having a basic mode from the first light source; A second input waveguide is configured to receive input light of a second wavelength having the basic mode from the second light source, and the second input waveguide is physically separated from the first input waveguide by a certain gap. A third input waveguide is configured to receive input light of a third wavelength having the basic mode from the third light source; An interferometric waveguide configured to combine the input light from the first input waveguide, the second input waveguide, and the third input waveguide; as well as An output waveguide, physically connected to the interferometric waveguide, wherein: The interferometric waveguide includes: Gradual reduction section; and A straight section, wherein the straight section is adjacent to the tapered section; The first input waveguide, the second input waveguide, and the third input waveguide are connected to the tapered section; The tapered section is configured to generate light of a first higher-order mode from a first portion of the light of the basic mode and light of a second higher-order mode from a second portion of the light of the basic mode, and to combine the input light from the first light source, the second light source, and the third light source for each of the input light of the first, second, and third light sources; and The contact surface between the interferometric waveguide and the output waveguide is configured to convert the first higher-order mode and the second higher-order mode into the basic mode for each of the first wavelength, the second wavelength, and the third wavelength.

2. The interferometric measurement device according to claim 1, wherein the first input waveguide and the second input waveguide extend parallel to the tapered section of the interferometric measurement waveguide.

3. The interferometric measurement device according to claim 1, wherein the first input waveguide and the second input waveguide are straight along their respective lengths.

4. The interferometric measuring device according to claim 1, wherein: The output waveguide includes an output center axis; The interferometric waveguide includes an interferometric central axis; and The output center axis is offset from the interferometric measurement center axis.

5. The interferometric measuring device according to claim 1, wherein: The output waveguide includes a first width; The interferometric waveguide includes a second width; and The second width is wider than the first width.

6. The interferometric measurement device according to claim 1, wherein the angle between the first input waveguide and the interferometric measurement waveguide is the same as the angle between the second input waveguide and the interferometric measurement waveguide.

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