JP7498868B2 - Arrayed waveguide grating and its manufacturing method, transceiver, and optical communication system - Google Patents

Description

This application claims priority to Chinese Patent Application No. 202110025612.6, entitled "ARRAYED WAVEGUIDE GRATING AND MANUFACTURING METHOD THEREOF, TRANSCEIVER, AND OPTICAL COMMUNICATION SYSTEM," filed with the China National Intellectual Property Office on January 8, 2021, and is incorporated herein by reference in its entirety.

This application relates to the field of optical communications, and in particular to an arrayed waveguide grating and a manufacturing method thereof, a transceiver, and an optical communications system.

Arrayed waveguide gratings (AWGs) are a core component of wavelength division multiplexing (WDM) technology.

The AWG includes a first waveguide, a first star coupler, an arrayed waveguide, a second star coupler, and a second waveguide, which are connected sequentially. The optical signal passing through the arrayed waveguide forms a Gaussian spectrum (also called Gaussian spectrum), so the spectrum of the optical signal output by the AWG is a Gaussian spectrum. The 3 dB bandwidth (the frequency range determined when the peak point of the power spectral density is reduced to 1/2 of the power spectral density) of the Gaussian spectrum is small. When an optical signal is transmitted based on an AWG with a small 3 dB bandwidth, the wavelength shift (also called wavelength drift) of the input optical signal easily causes a large insertion loss (which is called insertion loss for short, also called component insertion loss).

This application provides an arrayed waveguide grating and a manufacturing method thereof, a transceiver, and an optical communication system. The technical solutions are as follows:

According to a first aspect, an arrayed waveguide grating is provided, comprising a first waveguide, a pre-spreading component, a first coupler, an arrayed waveguide, a second coupler, and a second waveguide. The arrayed waveguide comprises m waveguides, the first waveguide comprises n waveguides, and the second waveguide comprises p waveguides. m is a positive integer greater than 1, n and p are both positive integers, and n and p are different.

The first waveguide is configured to input n optical signals to the first coupler. The first coupler is configured to couple the n optical signals to the m waveguides for transmission. The second coupler is configured to couple the optical signals transmitted in the m waveguides to the p waveguides for transmission. The second waveguide is configured to output the p optical signals. The first coupler and/or the second coupler can be star couplers/star couplers(s). A star coupler is a planar waveguide with a Rowland circle structure (also called a free propagation region). The Rowland circle structure is to reduce diffraction distortion and achieve uniform distribution of optical power.

The pre-diffusion component is located between the first waveguide and the first coupler, or between the second coupler and the second waveguide. A sub-wavelength grating arranged along the extension direction of the pre-diffusion component is arranged in the region where the pre-diffusion component is located, and the pre-diffusion component is configured to adjust the flatness of the top of the output spectrum of the arrayed waveguide grating. For example, the sub-wavelength grating arranged in the region where the pre-diffusion component is located means that the sub-wavelength grating is arranged in the pre-diffusion component, or that the sub-wavelength grating is arranged in the region surrounded by the boundary of the pre-diffusion component.

According to the AWG provided in this application, a pre-diffusion component with a sub-wavelength grating structure is added between the first waveguide and the first coupler or between the second coupler and the second waveguide. The pre-diffusion component is configured to adjust the flatness of the top of the output spectrum of the AWG, so that a flat-top spectrum is finally output from the AWG. The 3 dB bandwidth of the flat-top spectrum is large, which can effectively reduce the insertion loss caused by the wavelength shift of the optical signal. Moreover, since the AWG can resist the wavelength shift of the optical signal, there is no need to arrange an additional wavelength control system, which reduces the manufacturing cost and reduces the structural complexity of the AWG.

The grating parameters of a grating include the grating periodicity and/or the duty cycle. The grating period is the distance between two adjacent slits of the grating. The duty cycle is the ratio of the width of the gap between adjacent slits of the grating to the grating period. A subwavelength grating is a grating whose grating period is smaller than the operating wavelength. In a subwavelength grating, the grating period has a value range of [0.1 μm, 1 μm] and the duty cycle has a value range of (0, 1).

In the present application, the sub-wavelength grating structure on the pre-diffusion component may have multiple types. Based on the arrangement direction, the sub-wavelength grating structure on the pre-diffusion component may be classified into two types, which are provided in the following first and second option examples. Based on the grating parameters, the sub-wavelength grating structure on the pre-diffusion component may be classified into two types, which are provided in the following third and fourth option examples.

In a first example option, the subwavelength grating on the pre-diffusion component is a one-dimensional subwavelength grating. In other words, the subwavelength grating has only one alignment direction.

In an example of the second option, the subwavelength grating on the pre-diffusion component is a two-dimensional subwavelength grating (also called a 3D subwavelength grating). In the AWG, the subwavelength grating on the pre-diffusion component is a two-dimensional subwavelength grating, in other words, the subwavelength grating on the pre-diffusion component has two orientation directions.

In a third example option, the subwavelength grating is a uniform grating. A uniform grating is a grating whose grating period and duty cycle are both fixed values.

In a fourth example option, the subwavelength grating is a non-uniform grating. A non-uniform grating is a grating whose grating period and duty cycle are not fixed values. In other words, a non-uniform grating is a grating having at least two grating periods and/or a grating having at least two duty cycles. For example, the non-uniform grating can be a gradient grating. A gradient grating is a grating whose grating period gradually increases or decreases.

During practical implementation, the first to fourth example options may be combined based on circumstances. For example, the sub-wavelength grating on the pre-diffusion component is a one-dimensional sub-wavelength grating and is a uniform grating. Alternatively, the sub-wavelength grating on the pre-diffusion component is a two-dimensional sub-wavelength grating and is a uniform grating. Alternatively, the sub-wavelength grating on the pre-diffusion component is a one-dimensional sub-wavelength grating and is a non-uniform grating. Alternatively, the sub-wavelength grating on the pre-diffusion component is a two-dimensional sub-wavelength grating and is a non-uniform grating. Alternatively, the sub-wavelength grating on the pre-diffusion component is a two-dimensional sub-wavelength grating, one group of the sub-wavelength gratings is a uniform grating, and the other group of the sub-wavelength gratings is a non-uniform grating.

It should be noted that the above description is provided using an example in which the slits of the subwavelength grating are strip slits. In actual implementation, the slits of the subwavelength grating may be slits of other shapes, for example, curved slits. The lengths of the slits of the subwavelength grating may be equal or different.

Before manufacturing the AWG, the grating parameters of the sub-wavelength grating may be determined first, and the AWG is manufactured based on the determined grating parameters. In this way, the top of the output spectrum of the AWG is flat. In an implementation, the flatness of the top of the output spectrum of the AWG is related to the grating parameters of the sub-wavelength grating. The grating parameters of the sub-wavelength grating may be determined based on the flatness of the top of the output spectrum of the manufactured AWG. In another implementation, the equivalent refractive index of the AWG is related to the grating parameters of the sub-wavelength grating, and the equivalent refractive index of the AWG is related to the flatness of the top of the output spectrum of the AWG. The grating parameters of the sub-wavelength grating may be determined based on the equivalent refractive index of the manufactured AWG. If the grating period does not change, a larger duty cycle indicates a larger equivalent refractive index of the AWG. If the duty cycle does not change, a larger grating period indicates a larger equivalent refractive index of the AWG.

In an optional implementation, the pre-diffusion component is an axisymmetric structure, with the axis of symmetry of the pre-diffusion component parallel to the extension direction of the pre-diffusion component. An axisymmetric pre-diffusion component is easy to fabricate and can produce a symmetric double-peak optical field, so that the top of the output spectrum of the AWG is flat and not tilted.

The first waveguide has an axisymmetric structure, and the axis of symmetry of the pre-diffusion component is aligned with the axis of symmetry of the first waveguide. The axisymmetric first waveguide can be easily manufactured and can produce a symmetric Gaussian spectrum. The axis of symmetry of the pre-diffusion component is aligned with the axis of symmetry of the first waveguide to facilitate stable transmission of the optical signal. During practical implementation, the axis of symmetry of the pre-diffusion component may alternatively not be aligned with the axis of symmetry of the first waveguide.

The pre-diffusion component is a multimode interference (MMI) component. The MMI component is a rectangular structure, and the sub-wavelength grating is disposed on the MMI component, i.e., on the rectangular surface of the MMI component. In FIG. 8, the pre-diffusion component is a Y-shaped structure (also called a Y-branch structure), and the sub-wavelength grating is disposed in the area surrounded by the boundaries of the Y-shaped structure. In the present application, the pre-diffusion component may alternatively be another structure capable of adjusting the flatness of the top of the output spectrum of the AWG, for example, another structure capable of generating a double-peak optical field.

According to a second aspect, a transmitter machine is provided, comprising a light source, a modulator, and any one of the arrayed-waveguide gratings of the first aspect. The light source, the modulator, and the arrayed-waveguide grating are connected in sequence. n is greater than p. The light source is configured to output an optical signal. The modulator is configured to modulate a received optical signal to obtain a multi-wavelength optical signal, and input the multi-wavelength optical signal to the arrayed-waveguide grating.

According to a third aspect, a receiver apparatus is provided, comprising any one of the arrayed waveguide gratings of the first aspect and a plurality of receivers. The arrayed waveguide grating is separately connected to the plurality of receivers, where n is less than p. The receivers are configured to receive the optical signals output by the arrayed waveguide grating.

According to a fourth aspect, an optical communication system is provided, comprising a transmitter machine of the second aspect, a receiver machine of the third aspect, and an optical fiber connected to the transmitter machine and the receiver machine, respectively.

According to a fifth aspect, there is provided a method for manufacturing an arrayed waveguide grating, comprising:

providing a substrate; and fabricating a first waveguide, a pre-diffusion component, a first coupler, an arrayed waveguide, a second coupler, and a second waveguide on the substrate, where the arrayed waveguide includes m waveguides, the first waveguide includes n waveguides, and the second waveguide includes p waveguides, where m is a positive integer greater than 1, n and p are both positive integers, and n and p are different; the first waveguide is configured to input n optical signals to the first coupler, and the first coupler is configured to couple the n optical signals to the m waveguides for transmission. the second coupler is configured to couple the optical signals transmitted in the m waveguides to the p waveguides for transmission, and the second waveguide is configured to output the p optical signals; the pre-diffusion component is located between the first waveguide and the first coupler or between the second coupler and the second waveguide, a sub-wavelength grating arranged along the extension direction of the pre-diffusion component is arranged in the region where the pre-diffusion component is located, and the pre-diffusion component is configured to adjust the flatness of the top of the output spectrum of the arrayed waveguide grating.

Since the grating parameters of a subwavelength grating are related to the flatness of the top of the output spectrum of the AWG or the equivalent refractive index of the AWG, the grating parameters can be determined using the following two optional implementations:

In an optional implementation, prior to fabricating the first waveguide, the pre-diffusion component, the first coupler, the arrayed waveguide, the second coupler, and the second waveguide on the substrate, the method further includes: determining grating parameters of the sub-wavelength grating based on the top flatness of the output spectrum of the fabricated arrayed waveguide grating, the grating parameters including the grating period and/or the duty cycle.

In another optional implementation, prior to fabricating the first waveguide, the pre-diffusion component, the first coupler, the arrayed waveguide, the second coupler, and the second waveguide on the substrate, the method further includes: determining grating parameters of the sub-wavelength grating based on an equivalent refractive index of the fabricated arrayed waveguide grating, where the grating parameters include a grating period and/or a duty cycle.

According to the AWG provided in this application, a pre-diffusion component with a sub-wavelength grating structure is added between the first waveguide and the first coupler or between the second coupler and the second waveguide. The pre-diffusion component is configured to adjust the flatness of the top of the output spectrum of the AWG, so that a flat-top spectrum is finally output from the AWG. The 3 dB bandwidth of the flat-top spectrum is large, which can effectively reduce the insertion loss caused by the wavelength shift of the optical signal. In addition, since the AWG can resist the wavelength shift of the optical signal, there is no need to arrange an additional wavelength control system, which reduces the manufacturing cost and reduces the structural complexity of the AWG.

According to the AWG provided in this application, the pre-diffusion component with the sub-wavelength grating provides high flatness at the top of the output spectrum of the AWG, so that the insertion loss due to the wavelength shift of the optical signal in the AWG can be reduced. In addition, the flatness at the top of the output spectrum of the AWG is adjusted using the output spectrum of the AWG. Therefore, there is no need to arrange additional thermal adjustment components, the complexity of the AWG is reduced, the power consumption of the AWG is reduced, and the insertion loss caused by temperature drift is avoided.

According to the AWG provided in this application, the grating parameters of the subwavelength grating are adjusted in coordination with the pre-diffusion component to adjust the flatness of the top of the output spectrum of the AWG, so that it has high design freedom, high compatibility, and is applicable to different substrate materials and optical waveguide materials. In addition, since the pre-diffusion component with the subwavelength grating is arranged, the overall component size of the AWG is hardly increased, the manufacturing cost is low, and the AWG can be miniaturized.

1 is a schematic diagram of the spectrum of an optical signal output by a conventional AWG.

FIG. 1 is a schematic diagram of a structure of an AWG according to an embodiment of the present application.

FIG. 2 is a schematic diagram of the structure of another AWG according to an embodiment of the present application.

FIG. 2 is a schematic diagram of the working principle of a first coupler according to an embodiment of the present application;

FIG. 2 is a schematic diagram of the working principle of a second coupler according to an embodiment of the present application;

FIG. 1 is a schematic diagram of the working principle of an AWG according to an embodiment of the present application.

FIG. 2 is a schematic diagram of a part of the structure of an AWG according to an embodiment of the present application.

FIG. 2 is a schematic diagram of a portion of the structure of another AWG according to an embodiment of the present application.

FIG. 2 is a schematic diagram of the working principle of another AWG according to an embodiment of the present application.

FIG. 2 is a schematic diagram of a part of the structure of an AWG according to an embodiment of the present application.

FIG. 2 is a schematic diagram of a part of the structure of an AWG according to an embodiment of the present application.

FIG. 2 is a schematic diagram of a cross section of an AWG according to an embodiment of the present application.

FIG. 2 is a schematic diagram of an output spectrum of an AWG according to an embodiment of the present application.

FIG. 2 is a schematic diagram of the structure of a transmitter machine according to an embodiment of the present application;

FIG. 13 is a schematic diagram of the structure of another transmitter machine according to an embodiment of the present application.

FIG. 2 is a schematic diagram of the structure of a receiver machine according to an embodiment of the present application;

FIG. 1 is a schematic diagram of the structure of an optical communication system according to an embodiment of the present application.

1 is a schematic flow chart of a method for manufacturing an AWG according to an embodiment of the present application.

In order to make the principles and technical solutions of the present application clearer, the following provides a more detailed description of the implementation of the present application with reference to the accompanying drawings.

The conventional AWG includes a first waveguide, a first star coupler, an arrayed waveguide, a second star coupler, and a second waveguide, which are connected in sequence. FIG. 1 is a schematic diagram of the spectrum (also called the output spectrum) of an optical signal output by a conventional AWG. The spectrum is a Gaussian spectrum. In the schematic diagram of the spectrum, the horizontal axis represents wavelength in micrometers (μm) or nanometers (nm). The vertical axis represents power transmittance in decibels (dB) (the vertical axis may alternatively represent optical power in milliwatts (mw) or decibel-milliwatts (dBm)). Power transmittance is the ratio of the output optical power of the optical signal to the input optical power. As shown in FIG. 1, the Gaussian spectrum is mainly caused by a Gaussian optical field that is generated when the optical signal passes through the arrayed waveguide. The top of the Gaussian spectrum is prominent, and the 3 dB bandwidth is small. The 3 dB bandwidth is usually only about 40% of the total bandwidth of the Gaussian spectrum. When an optical signal is transmitted based on an AWG with a small 3 dB bandwidth, if the wavelength of the input optical signal is unstable and a small wavelength shift occurs, the optical power may be reduced and a large insertion loss (abbreviated as insertion loss) may occur. See the schematic diagram of the spectrum in Figure 1. The wavelength shift means that the wavelength of the optical signal shifts from the wavelength corresponding to the position with the maximum power transmittance to the wavelength corresponding to another position. If the insertion loss needs to be reduced, a wavelength control system needs to be added to control the wavelength of the input optical signal. However, the wavelength control system increases the manufacturing cost of the AWG and increases the structural complexity of the AWG.

2 and 3 are schematic diagrams of the structure of two AWGs 10 according to an embodiment of the present application. The flatness of the top of the output spectrum of the AWG is high, and the wavelength range corresponding to the 3 dB bandwidth can be increased, so that the insertion loss caused by the wavelength shift of the optical signal in the AWG is reduced, and there is no need to arrange an additional wavelength control system. As shown in FIGS. 2 and 3, the AWG 10 includes a first waveguide 101, a pre-spreading component 102, a first coupler 103, an arrayed waveguide 104, a second coupler 105, and a second waveguide 106.

The arrayed waveguide 104 includes m waveguides, the first waveguide 101 includes n waveguides, and the second waveguide 106 includes p waveguides. m is a positive integer greater than 1, n and p are both positive integers, and n and p are different. In FIG. 2, an example of m=10, n=1, and p=5 is used for explanation. In FIG. 3, an example of m=10, n=5, and p=1 is used for explanation. The values of m, n, and p are not limited in the embodiment of the present application.

The first waveguide 101 is configured to input n optical signals to the first coupler 103, and the second waveguide 106 is configured to output p optical signals.

The first coupler 103 is configured to couple n optical signals to m waveguides for transmission. FIG. 4 is a schematic diagram of the working principle of the first coupler according to an embodiment of the present application. As shown in FIG. 4, in the first coupler 103, each of the n optical signals is input from the first waveguide 101, enters the coupling region (i.e., Rowland circle) of the first coupler 103, branches off from the coupling region, and then simultaneously enters m waveguides. The first coupler 103 is configured to distribute the power of the n optical signals evenly to the m waveguides. In FIG. 4, an example of n=1 and m=5 is used for illustration, but the specific values of n and m are not limited. For example, when an optical signal having a wavelength of 1550 nm enters the coupling region of the first coupler 103, the optical signal having that wavelength simultaneously enters m waveguides of the arrayed waveguide 104.

The arrayed waveguide 104 is configured to transmit optical signals using the principle of multi-beam interference. In the arrayed waveguide 104, there is a fixed length difference between adjacent waveguides. In order to form different wavefront slopes after the m optical signals pass through the arrayed waveguide 104, optical path differences are introduced to focus the m optical signals at different positions of the second coupler 105. Thus, the m optical signals are received by different waveguides of the second waveguide 106 through the second coupler 105.

The second coupler 105 is configured to couple optical signals transmitted in the m waveguides to the p waveguides for transmission. FIG. 5 is a schematic diagram of the working principle of the second coupler according to an embodiment of the present application. As shown in FIG. 5, in the second coupler 105, after the m optical signals are transmitted from the arrayed waveguides 104 with fixed length difference, the m optical signals are diffracted in the coupling region (i.e., Rowland circle) of the second coupler 105, focused at p positions, and output separately from the p waveguides of the second waveguide 106. In the coupling region of the second coupler 105, optical signals with the same wavelength are focused at the same position of the coupling region, and optical signals with different wavelengths are focused at different positions of the coupling region. The second coupler 105 may implement a demultiplexing function. Specifically, the wavelengths of the optical signals entering the p waveguides of the second waveguide 106 are different from each other. In FIG. 5, an example of m=5 and p=3 is used for explanation. The second coupler 105 is assumed to output three optical signals with different wavelengths, which are optical signals with wavelengths λ1 to λ3. However, the specific values of m, p, and λ are not limited.

The first coupler 103 and/or the second coupler 105 may be a star coupler/star couplers. A star coupler is a planar waveguide (also called a free propagation region) with a Rowland circle structure. The Rowland circle structure is to reduce diffraction distortion and achieve a uniform distribution of optical power.

2, the pre-diffusion component 102 is located between the first waveguide 101 and the first coupler 103, and the pre-diffusion component 102 forms a transition area between the first waveguide 101 and the first coupler 103. The widths of the first waveguide 101, the pre-diffusion component 102, and the first coupler 103, for example, gradually increase or gradually decrease. Alternatively, as shown in FIG. 3, the pre-diffusion component 102 is located between the second coupler 105 and the second waveguide 106, and the pre-diffusion component 102 forms a transition area between the second coupler 105 and the second waveguide 106. The widths of the second coupler 105, the pre-diffusion component 102, and the second waveguide 106, for example, gradually increase or gradually decrease.

As shown in FIG. 2 or FIG. 3, the sub-wavelength diffraction grating 1021 arranged along the extension direction (i.e., length direction) r1 of the pre-diffusion component 102 is arranged in the region where the pre-diffusion component 102 is located, and the width direction r2 of the pre-diffusion component 102 is perpendicular to the extension direction r1 of the pre-diffusion component 102. The pre-diffusion component 102 and the sub-wavelength diffraction grating 1021 can be obtained by manufacturing using the same composition technology. For example, the sub-wavelength diffraction grating arranged in the region where the pre-diffusion component is located means that the sub-wavelength diffraction grating is arranged in the pre-diffusion component, or that the sub-wavelength diffraction grating is arranged in the region surrounded by the boundary of the pre-diffusion component.

The pre-spreading component 102 is configured to adjust the flatness of the top of the output spectrum of the AWG 10. The flatness of the top of the output spectrum is the degree of change in the amplitude of the power transmittance when the wavelength of the optical signal changes. A smaller change in the amplitude of the power transmittance indicates a higher flatness. Based on the adjustment performed by the pre-spreading component 102, the AWG 10 may output a flat-top spectrum. Since the 3 dB bandwidth of the flat-top spectrum can be greatly improved, the wavelength range corresponding to the 3 dB bandwidth is effectively increased, and the insertion loss caused by the instability of the input optical signal is reduced to a certain extent.

According to the AWG provided in this embodiment of the present application, a pre-diffusion component with a sub-wavelength grating structure is added between the first waveguide and the first coupler or between the second coupler and the second waveguide. The pre-diffusion component is configured to adjust the flatness of the top of the output spectrum of the AWG, so that a flat-top spectrum is finally output from the AWG. The 3 dB bandwidth of the flat-top spectrum is large, which can effectively reduce the insertion loss caused by the wavelength shift of the optical signal.

In addition, since the AWG can resist the wavelength shift of the optical signal, there is no need to deploy an additional wavelength control system, which reduces the manufacturing cost and reduces the structural complexity of the AWG.

In an embodiment of the present application, the pre-diffusion component 102 can form a double-peak optical field (also called a double-hump optical field or a hump optical field). The double-peak optical field is an optical field having two waveform peaks (also called protrusions) and one waveform trough (also called depression) located between the two waveform peaks. FIG. 6 is a schematic diagram of the operation principle of the AWG 10 according to an embodiment of the present application. For example, FIG. 6 shows the change process of the optical field corresponding to the optical signal in FIG. 2 as the optical signal passes through the first waveguide 101, the pre-diffusion component 102, and the first coupler 103. The optical field of the optical signal input from the first waveguide 101 is a Gaussian optical field. After the optical signal passes through the pre-diffusion component 102, the optical field of the optical signal input to the first coupler 103 changes to a double-peak optical field.

In an optional method, the pre-diffusion component 102 uses a self-mapping principle to form a double-peak optical field. Self-mapping, also called self-imaging, is a function of a multimode waveguide. Based on the self-mapping function, N copies of the optical field (N is a positive integer) of the input optical field are periodically regenerated at intervals according to the distribution of the input optical field along the optical signal transmission direction of the waveguide. Different evenly divided optical fields, for example, a 1:2 optical field (i.e., a double-peak optical field), a 1:3 optical field (i.e., a triple-peak optical field), or a 1:4 optical field (i.e., a four-peak optical field), appear at different positions along the optical signal transmission direction of the multimode waveguide. In an embodiment of the present application, the pre-diffusion component 102 is a multimode waveguide. The length of the pre-diffusion component 102 can ensure that the 1:2 optical field appears at the output end of the pre-diffusion component 102. FIG. 7 is a schematic diagram of a part of the structure of an AWG according to an embodiment of the present application. In FIG. 7, the pre-diffusion component 102 is an MMI component that utilizes the self-imaging principle to form a double-peaked optical field.

In another optional method, the pre-diffusion component 102 utilizes the power equal division principle to form a double-peak optical field. The pre-diffusion component 102 based on the power equal division principle is a power division structure. The pre-diffusion component 102 divides the power of the input optical signal into two equal parts, and outputs the two optical signals obtained after division using two branch waveguides. When the distance between the two branch waveguides is short, the optical fields of the optical signals on the two branches form a double-peak optical field due to the superposition of edge energies. FIG. 8 is a schematic diagram of a part of the structure of another AWG according to an embodiment of the present application. In FIG. 8, the pre-diffusion component 102 is a Y-shaped structure (also called a Y-branch structure). The Y-shaped structure includes a main waveguide a1 and two branch waveguides a2 connected to the main waveguide a1. In the Y-shaped structure, a double-peak optical field is formed using the power equal division principle.

In an embodiment of the present application, the pre-diffusion component 102 may alternatively be another structure capable of adjusting the flatness of the top of the output spectrum of the AWG, for example, another structure capable of generating a double-peaked optical field. This is not limited to this embodiment of the present application.

For example, as shown in Figures 2 and 3, the pre-diffusion component 102 has an axisymmetric structure, and the symmetry axis of the pre-diffusion component 102 is parallel to the extension direction r1 of the pre-diffusion component 102. The axisymmetric pre-diffusion component 102 is easy to manufacture and can form a symmetric double-peak optical field so that the top of the output spectrum of the AWG 10 is flat and not tilted.

In this embodiment of the present application, the first waveguide 101 may be an axisymmetric structure, and the symmetry axis of the pre-diffusion component 102 is aligned with the symmetry axis of the first waveguide 101. The axisymmetric first waveguide 101 can be easily manufactured and form a symmetric Gaussian spectrum. The symmetry axis of the pre-diffusion component 102 is aligned with the symmetry axis of the first waveguide 101 such that the power of the two protrusions (i.e., two peaks) of the double-peak optical field is equal. Thus, the symmetry of the double-peak optical field is ensured. During practical implementation, the first waveguide 101 may alternatively be a non-axisymmetric structure.

For example, FIG. 9 is a schematic diagram of the superposition of the double-peak optical field corresponding to the optical signal output by the pre-diffusion component 102 and output by the arrayed waveguide 104 and the Gaussian optical field. The depression of the double-peak optical field and the protrusion of the Gaussian optical field can cancel each other out, so that the flatness of the top of the optical field of the optical signal finally output from the AWG 10 is high. This optical field is called a flat-top optical field, and the output spectrum corresponding to this optical field is a flat-top spectrum. In FIG. 9, the horizontal axis of the schematic diagram of each optical field is the width of the waveguide through which the optical signal passes, in micrometers. The vertical axis is the magnetic field strength corresponding to the optical signal, in a.u., where a.u. represents a unit of relative value and can be any set unit. FIG. 9 does not show the two coordinate axes of the schematic diagram of each optical field.

A diffraction grating is an optical component that contains a large number of parallel slits (or scales). The grating parameters of a diffraction grating include the grating period and/or the duty cycle. The grating period, also called the grating constant, is the distance between two adjacent slits of the diffraction grating and may be expressed as the distance between the same sides of the two slits. The grating period may be equal to the sum of the width of one slit of the diffraction grating and the width of the gap between the slit and another slit. The duty cycle is the ratio of the width of the gap between adjacent slits of the diffraction grating to the grating period. As shown in Figure 7, an example where the grating period a is the distance between the right sides of the two slits and b is the width of the gap between the slits (i.e., the width of the area between the two slits) is used in Figure 7 for identification purposes.

A subwavelength grating is a grating whose grating period is smaller than the operating wavelength. For example, the grating period of the subwavelength grating provided in this embodiment of the present application has a value range of [0.1 μm, 1 μm], and the duty cycle has a value range of (0, 1). In an AWG, the operating wavelength is the wavelength of the optical signal supported by the AWG. For example, if the output end of the AWG includes one optical channel, the operating wavelength is the wavelength of the optical signal corresponding to the optical channel. If the output end of the AWG includes multiple optical channels, the optical signals passing through the AWG are multiple optical signals corresponding to the multiple optical channels. In this case, the operating wavelength is the specified wavelength of the multiple optical signals. For example, the specified wavelength is the center wavelength, any wavelength, minimum wavelength, maximum wavelength, or average wavelength.

For different types of pre-diffusion components 102, the sub-wavelength grating may be located at different positions of the pre-diffusion component 102. For example, in FIG. 7, the pre-diffusion component 102 is an MMI component, which is a rectangular structure. The sub-wavelength grating is located on the MMI component, i.e., on the rectangular surface of the MMI component. In FIG. 8, the pre-diffusion component 102 is a Y-shaped structure (also called a Y-branch structure), and the sub-wavelength grating is located in the area surrounded by the boundaries of the Y-shaped structure, i.e., between the two branch waveguides a2.

In this embodiment of the present application, the sub-wavelength grating 1021 on the pre-diffusion component 102 may have multiple types. Based on the placement direction, the sub-wavelength grating 1021 on the pre-diffusion component 102 may be classified into two types, which are provided in the following first and second option examples. Based on the grating parameters, the sub-wavelength grating 1021 on the pre-diffusion component 102 may be classified into two types, which are provided in the following third and fourth option examples.

In a first example option, the subwavelength grating on the pre-diffusion component 102 is a one-dimensional subwavelength grating. In other words, the subwavelength grating has only one orientation. The structure of the subwavelength grating on the pre-diffusion component 102 is shown in FIG. 2, FIG. 3, FIG. 7, or FIG. 8.

In a second optional example, the sub-wavelength grating on the pre-diffusion component 102 is a two-dimensional sub-wavelength grating (also called a 3D sub-wavelength grating). FIG. 10 is a schematic diagram of a part of the structure of an AWG according to an embodiment of the present application. In the AWG, the sub-wavelength grating on the pre-diffusion component 102 is a two-dimensional sub-wavelength grating, in other words, the sub-wavelength grating on the pre-diffusion component 102 has two arrangement directions. In this case, as shown in FIG. 10, in addition to the sub-wavelength grating arranged along the extension direction r1 of the pre-diffusion component 102, a sub-wavelength grating arranged along another direction r2 is further arranged on the pre-diffusion component 102. The other direction r2 is perpendicular to the extension direction r1 of the pre-diffusion component 102. In this way, the sub-wavelength grating arranged along the extension direction of the pre-diffusion component 102 and the sub-wavelength grating arranged along another direction form a grid grating structure. In an optional implementation, the sub-wavelength grating slits arranged along the extension direction r1 of the pre-diffusion component 102 and the sub-wavelength grating slits arranged along another direction r2 are arranged on the surface of the pre-diffusion component, and each grid in the grid grating is a block-shaped body protruding relative to the surface of the pre-diffusion component.

In a third optional embodiment, the subwavelength grating is a uniform grating. A uniform grating is a grating in which the grating period and the duty cycle are both fixed values. The structure of a uniform grating is shown in Figure 2, Figure 3, Figure 7, Figure 8, or Figure 10. As shown in Figure 7, the duty cycle of a grating is the ratio of the width b of the inter-slit gap to the grating period a, i.e., b/a.

In a fourth example option, the sub-wavelength grating is a non-uniform grating. A non-uniform grating is a grating in which the grating period and the duty cycle are not fixed values. In other words, a non-uniform grating is a grating with at least two grating periods and/or a grating with at least two duty cycles. FIG. 11 is a schematic diagram of a portion of the structure of an AWG according to an embodiment of the present application. In the AWG, the sub-wavelength grating on the pre-diffusion component 102 is a non-uniform grating. For example, the non-uniform grating can be a gradient grating. A gradient grating is a grating in which the grating period gradually increases or decreases.

During practical implementation, the first to fourth option examples may be combined based on circumstances. For example, the sub-wavelength grating on the pre-diffusion component 102 is a one-dimensional sub-wavelength grating and is a uniform grating. Alternatively, the sub-wavelength grating on the pre-diffusion component 102 is a two-dimensional sub-wavelength grating and is a uniform grating. Alternatively, the sub-wavelength grating on the pre-diffusion component 102 is a one-dimensional sub-wavelength grating and is a non-uniform grating. Alternatively, the sub-wavelength grating on the pre-diffusion component 102 is a two-dimensional sub-wavelength grating and is a non-uniform grating. Alternatively, the sub-wavelength grating on the pre-diffusion component 102 is a two-dimensional sub-wavelength grating, one group of the sub-wavelength gratings is a uniform grating, and the other group of the sub-wavelength gratings is a non-uniform grating.

It should be noted that in all the above-mentioned embodiments, the example in which the slits of the sub-wavelength grating are slits distributed along a straight line is used for explanation. In actual implementation, the slits of the sub-wavelength grating may be slits of other shapes, for example, curved slits. The lengths of the slits of the sub-wavelength grating may be equal or different. A sub-wavelength grating that can implement the function of adjusting the flatness of the top of the output spectrum of the pre-diffusion component 102 should be within the protection scope of the embodiments of the present application.

In this embodiment of the present application, the positions of the two peaks of the double-peak optical field are determined based on the width of the pre-diffusion component 102 (the width direction is r2 as shown in FIG. 2, FIG. 3, or FIG. 10). The equivalent refractive index of the pre-diffusion component 102 affects the depth of the depression of the double-peak optical field. Usually, the equivalent refractive index of the pre-diffusion component 102 is negatively correlated to the depth of the double-peak optical field. In other words, a smaller equivalent refractive index of the pre-diffusion component 102 indicates a deeper depression of the double-peak optical field. It should be noted that the equivalent refractive index of the pre-diffusion component is the equivalent refractive index of the region in which the pre-diffusion component is located. For example, if the pre-diffusion component is an MMI, the region in which the pre-diffusion component is located is the region surrounded by the boundary of the MMI. If the pre-diffusion component is a Y-shaped structure, the region in which the pre-diffusion component is located is the region surrounded by the boundary of the Y-shaped structure. If the pre-diffusion component 102 does not have a sub-wavelength grating, for example, if the pre-diffusion component is an MMI component without a sub-wavelength grating, the width and equivalent refraction of the MMI component are fixed, so the MMI component cannot accurately adjust and control the amplitude distribution of the double-peak optical field generated by the double self-mapping effect. In the double-peak optical field output by the MMI component, the optical fields between the two image points (i.e., the two peaks) overlap and rise as a whole. As a result, the depression degree of the middle region (i.e., the depression region) of the optical field is insufficient, and the depression depth does not meet the flatness requirement of the output spectrum of the AWG. Therefore, the use of the pre-diffusion component 102 without a sub-wavelength grating cannot make the top of the output spectrum of the AWG 10 reach the target flatness. The sub-wavelength grating can adjust the depression depth of the double-peak optical field by affecting the equivalent refractive index of the pre-diffusion component (e.g., lowering the equivalent refractive index of the pre-diffusion component) to affect the shape of the output spectrum of the AWG 10. By disposing the sub-wavelength grating, the pre-diffusion component 102 can adjust the flatness of the top of the output spectrum of the AWG 10 so that the top of the output spectrum of the AWG 10 reaches a target flatness, provided that the pre-diffusion component 102 has a width that helps adjust the equivalent refractive index of the pre-diffusion component.

In this way, before manufacturing the AWG 10, the grating parameters of the sub-wavelength grating may be determined first, and the AWG 10 is manufactured based on the determined grating parameters. In this way, the top of the output spectrum of the AWG 10 is flat. The grating parameters include the grating period and/or the duty cycle. In an implementation, the flatness of the top of the output spectrum of the AWG 10 is related to the grating parameters of the sub-wavelength grating. The grating parameters of the sub-wavelength grating may be determined based on the flatness of the top of the output spectrum of the manufactured AWG 10. In another embodiment, the equivalent refractive index of the AWG 10 (or the equivalent refractive index of the pre-diffusion component) is related to the grating parameters of the sub-wavelength grating, and the equivalent refractive index of the AWG is related to the flatness of the top of the output spectrum of the AWG. If the grating period does not change, a larger duty cycle indicates a larger equivalent refractive index of the AWG. If the duty cycle does not change, a larger grating period indicates a larger equivalent refractive index of the AWG. In this case, the grating parameters of the sub-wavelength grating may be determined based on the equivalent refractive index of the manufactured AWG 10. For specific processes of the two implementations, please refer to the processes of the subsequent method embodiments.

The AWG 10 provided in this embodiment of the present application may further include a substrate (also called substrate plate), and an AWG pattern (pattern) is disposed on the substrate. The AWG pattern includes a first waveguide 101, a pre-diffusion component 102, a first coupler 103, an arrayed waveguide 104, a second coupler 105, and a second waveguide 106. In different manufacturing scenarios, the material of the substrate may be different, and the material of the AWG pattern may also be different. For example, the material of the substrate may be lithium niobate (LiNbO ₃ ), III-V semiconductor compounds, silicon dioxide (SiO ₂ ), silicon (Si), polymer, or glass. The optical waveguide material for manufacturing the AWG pattern may be silicon (Si), silicon nitride (SiN), silicon oxynitride (SiON), or silicon dioxide.

Optionally, the AWG 10 may further include another material layer. For example, the AWG 10 may further include a first protective layer located on the side of the AWG pattern closer to the substrate, and/or a second protective layer located on the side of the AWG pattern closer to the substrate. Both the first protective layer and the second protective layer are configured to protect the AWG pattern to improve the lifetime of the AWG pattern. For example, the material of both the first protective layer and the second protective layer is silicon dioxide. FIG. 12 is a schematic diagram of a cross section of the AWG 10 according to an embodiment of the present application. The AWG 10 includes a substrate 107, a first protective layer 108, an AWG pattern M, and a second protective layer 109. The AWG pattern M includes the first waveguide 101, the pre-diffusion component 102, the first coupler 103, the arrayed waveguide 104, the second coupler 105, and the second waveguide 106 of the previous embodiment. The sub-wavelength grating 1021 is disposed on the pre-diffusion component 102.

In the following, for ease of understanding, the structure of an actual AWG is used as an example for explanation. In the AWG, it is assumed that the arrayed waveguide includes 16 waveguides (also called 16 channels), and the length difference between adjacent waveguides is 100 (GHz), in other words, the channel spacing is 100 gigahertz (GHz). The channel spacing is the ratio of the wavelengths corresponding to the waveform peaks of the output spectrum of adjacent waveguides to the frequency spacing. The material of the AWG pattern is silicon nitride, and the thickness of the silicon nitride layer is 80 nanometers (nm). In addition, the AWG further includes a first protective layer and a second protective layer disposed on both sides of the AWG pattern. The materials of both the first protective layer and the second protective layer are silicon dioxide. The widths of the first waveguide, the second waveguide, and the arrayed waveguide are each 3.5 micrometers. The spacing between the n waveguides of the first waveguide and the junctions between the n waveguides and the first coupler is 8 micrometers, and the spacing between the p waveguides of the second waveguide and the junctions between the p waveguides and the second coupler is 8 micrometers. The spacing between the m waveguides of the arrayed waveguide and each of the junctions between the m waveguides and the first coupler and the junctions between the m waveguides and the second coupler is 10 μm. m=145, n=1, p=16. Both the first coupler and the second coupler include a Rowland circle structure, and the diameter of the Rowland circle structure is 1.823 millimeters. A pre-diffusion component having a one-dimensional subwavelength grating is disposed between the first waveguide and the first coupler, and the pre-diffusion component is an MMI.

Figure 13 is a schematic diagram of the output spectrum of the AWG according to an embodiment of the present application. The output spectrum of the AWG includes spectra corresponding to the 16 waveguides (also called output channels) included in the second waveguide. In the schematic diagram of the output spectrum, the horizontal axis represents the wavelength in μm, and the vertical axis represents the power transmittance in dB. The introduction of the sub-wavelength grating effectively blocks the superposition of the two protrusions of the double-peak optical field, resulting in a large concavity. As shown in Figure 13, the resulting output spectrum has good spectral flatness of each waveguide in the second waveguide. For example, for one optical signal, the 0.5 dB bandwidth (the frequency range determined when the peak point of the power spectral density is reduced by 0.5 dB) is 46 GHz, and the 1 dB bandwidth is 53 GHz. It is clear that the 1 dB bandwidth (the frequency range determined when the peak point of the power spectral density is reduced by 1 dB) reaches 53% of the channel spacing, and the 3 dB bandwidth is greater than 53% of the channel spacing. In this case, the 3 dB bandwidth of the obtained flat-top spectrum can be significantly improved, and the insertion loss caused by the instability of the input optical signal can be effectively reduced.

According to the AWG provided in this embodiment of the present application, the pre-diffusion component with the subwavelength grating provides a high flatness at the top of the output spectrum of the AWG, thereby reducing the insertion loss caused by the wavelength shift of the optical signal in the AWG. In addition, the impact of manufacturing errors on the performance of the AWG component can be further reduced, improving the stability of the AWG component.

In the related art, an AWG is further proposed. The AWG includes a thermal tuning component disposed at the input end of the first waveguide, which heats the first waveguide to reduce the wavelength shift of the input optical signal. However, the complexity of the AWG increases, and the power consumption of the AWG increases. In addition, temperature drift also results in insertion loss. According to the AWG provided in this embodiment of the present application, the flatness of the top of the output spectrum of the AWG is adjusted using the output spectrum of the AWG. Therefore, no additional thermal tuning component needs to be disposed, the complexity of the AWG is reduced, the power consumption of the AWG is reduced, and the insertion loss caused by temperature drift is avoided.

In addition, according to the AWG provided in this embodiment of the present application, the grating parameters of the subwavelength grating are adjusted to coordinate with the pre-diffusion component to adjust the flatness of the top of the output spectrum of the AWG, so that the design has high flexibility, high compatibility, and is applicable to different substrate materials and optical waveguide materials. Furthermore, since the pre-diffusion component with the subwavelength grating is arranged, the overall component size of the AWG is hardly increased, the manufacturing cost is low, and the AWG can be miniaturized.

14 and 15 are schematic diagrams of the structure of two transmitter machines (also called optical transmitter machines) 20 according to an embodiment of the present application, respectively. The transmitter machine 20 includes a light source 201, a modulator 202, and an AWG 203. The AWG 203 can be any AWG 10 provided in the embodiment of the present application.

In Figures 14 and 15, the light source 201, the modulator 202, and the AWG 203 are connected in this order. In the AWG 203, the amount of waveguide n included in the first waveguide is greater than the amount of waveguide p included in the second waveguide. For example, p=1. In this way, the AWG 203 multiplexes multiple optical signals into one optical signal.

In Figures 14 and 15, the light source 201 is configured to output an optical signal, and the modulator 202 is configured to modulate the received optical signal to obtain a multi-wavelength optical signal and input the multi-wavelength optical signal to the AWG 203.

In an optional implementation, as shown in FIG. 14, the transmitter machine 20 includes one light source 201 and one or more modulators 202. The optical signal output by the light source 201 has a fixed wavelength and is modulated by one or more modulators 202 to obtain a multi-wavelength optical signal. In another optional embodiment, as shown in FIG. 15, the transmitter machine 20 includes multiple light sources 201 and multiple modulators 202, and the multiple light sources 201 are connected one-to-one to the multiple modulators 202. The different light sources 201 have different wavelengths and are fixed wavelengths, and the optical signal output from each light source 201 is modulated by the corresponding modulator 202. The multiple modulators 202 output optical signals with multiple wavelengths and input the optical signals with multiple wavelengths to the AWG 203.

According to the transmitter machine provided in this embodiment of the present application, a pre-spreading component having a sub-wavelength grating structure is added between the first waveguide and the first coupler of the AWG or between the second coupler and the second waveguide. The pre-spreading component is configured to adjust the flatness of the top of the output spectrum of the AWG, so that a flat-top spectrum is finally output from the AWG. The 3 dB bandwidth of the flat-top spectrum is large, which can effectively reduce the insertion loss caused by the wavelength shift of the optical signal, and the insertion loss of the transmitter machine is further reduced.

In addition, due to the low insertion loss of the AWG, there is no need to deploy an additional wavelength control system, thereby reducing manufacturing costs and the size of the transmitter machine.

FIG. 16 is a schematic diagram of the structure of a receiver machine 30 according to one embodiment of the present application. The receiver machine 30 includes an AWG 301 and multiple receivers 302. The AWG 301 can be any AWG 10 provided in the embodiments of the present application.

In FIG. 16, AWG301 is separately connected to multiple receivers 302, and receivers 302 are configured to receive optical signals output by AWG301. In AWG301, the amount of waveguides n included in the first waveguide is less than the amount of waveguides p included in the second waveguide. For example, n=1. In this manner, AWG301 separates one optical signal into multiple optical signals. For example, AWG301 outputs multiple optical signals, and each of the multiple optical signals is input to a different receiver 302.

According to the receiver machine provided in this embodiment of the present application, a pre-spreading component with a sub-wavelength grating structure is added between the first waveguide and the first coupler of the AWG, or between the second coupler and the second waveguide. The pre-spreading component is configured to adjust the flatness of the top of the output spectrum of the AWG, so that a flat-top spectrum is finally output from the AWG. The 3 dB bandwidth of the flat-top spectrum is large, which can effectively reduce the insertion loss caused by the wavelength shift of the optical signal, and the insertion loss of the receiver machine is further reduced.

In addition, due to the low insertion loss of the AWG, there is no need to deploy an additional wavelength control system, resulting in reduced manufacturing costs and reduced size of the receiver machine.

FIG. 17 is a schematic diagram of the structure of an optical communication system 40 according to one embodiment of the present application. The optical communication system includes a transmitter machine 401, a receiver machine 402, and an optical fiber 403 connected to the transmitter machine 401 and the receiver machine 402, respectively. The transmitter machine 401 may be the transmitter machine 20 in the above-mentioned embodiment, and the receiver machine 402 may be the receiver machine 30 in the above-mentioned embodiment.

Figure 18 is a schematic flow chart of a method for manufacturing an AWG according to an embodiment of the present application. The manufacturing method of the present invention includes the following steps:

S501: Determine grating parameters of a subwavelength grating, the grating parameters including a grating period and/or a duty cycle.

As mentioned above, the grating parameters of a subwavelength grating are related to the flatness of the top of the output spectrum of the AWG or the equivalent refractive index of the AWG, so the grating parameters can be determined using the following two optional implementations:

In the implementation of the first option, the grating parameters of the subwavelength grating are determined based on the apex flatness of the output spectrum of the AWG to be manufactured.

The higher the flatness of the top of the output spectrum of the AWG obtained by manufacturing, the smaller the insertion loss generated by the AWG due to the wavelength shift of the optical signal. Therefore, before manufacturing the AWG, the grating parameters of the sub-wavelength grating can be determined based on the flatness to be achieved of the top of the output spectrum of the AWG. For example, the staff can continuously adjust the grating parameters using simulation software and observe the change in the flatness of the top of the output spectrum of the AWG obtained through simulation. If the top of the output spectrum of the AWG obtained through simulation is approximately horizontal, the corresponding grating parameters are determined as the grating parameters required to manufacture the AWG. The grating period and/or duty cycle of the sub-wavelength grating are adjusted to more accurately control the concavity of the double-peak optical field, so that the double-peak optical field meets the input field distribution required in the AWG spectral flatness design. Therefore, the required flatness of the spectrum of the AWG is achieved.

As mentioned above, when the grating period does not change, a larger duty cycle indicates a larger equivalent refractive index of the AWG. When the duty cycle does not change, a larger grating period indicates a larger equivalent refractive index of the AWG. The equivalent refractive index of the pre-diffusion component is negatively correlated with the concavity of the double-peak optical field. Correspondingly, when other parameters do not change, the equivalent refractive index of the AWG is negatively correlated with the concavity of the double-peak optical field. In this case, for example, before manufacturing the AWG, the staff may use simulation software to keep the grating period unchanged and gradually reduce the duty cycle of the sub-wavelength grating. For example, the staff may start with a duty cycle of 1 (or 0.99) and gradually reduce the duty cycle. In this way, the equivalent refractive index of the AWG gradually decreases (the equivalent refractive index of the pre-diffusion component also gradually decreases), and the concavity of the double-peak optical field gradually increases. The staff may observe that the flatness of the output spectrum of the AWG gradually increases. If the duty cycle of the sub-wavelength grating continues to decrease after the flatness reaches a maximum value, the equivalent refractive index of the AWG continues to decrease (the equivalent refractive index of the pre-diffusion component also gradually decreases), and the concavity of the double-peak optical field continues to increase. The staff may observe that the flatness of the output spectrum of the AWG gradually decreases. Therefore, the staff may record the correspondence between the duty cycle of the sub-wavelength grating and the flatness of the output spectrum, and after finding that the flatness of the output spectrum of the AWG first increases and then decreases, find the flatness at the turning point of the flatness (specifically, the inflection point where the flatness first increases and then decreases) as the target flatness, and refer to the aforementioned correspondence based on the target flatness to determine the target duty cycle.

For another example, before manufacturing the AWG, staff may alternatively use simulation software to keep the duty cycle unchanged and adjust the grating period. Or, staff may adjust the duty cycle and the grating period simultaneously. For the process of determining the grating parameters, please refer to the target duty cycle determination process described above. Details will not be described in this embodiment of the present application.

In the implementation of the second option, the grating parameters of the subwavelength grating are determined based on the equivalent refractive index of the AWG to be fabricated.

A high flatness at the top of the output spectrum of the AWG obtained by manufacturing indicates that the insertion loss generated by the AWG due to the wavelength shift of the optical signal is small. The equivalent refractive index of the AWG changes based on the flatness at the top of the output spectrum of the AWG. Therefore, before manufacturing the AWG, the equivalent refractive index of the AWG can be determined based on the flatness to be achieved at the top of the output spectrum of the AWG. Then, the grating parameters of the sub-wavelength grating are determined based on the equivalent refractive index of the AWG. For example, the staff may determine a target flatness at the top of the output spectrum (for example, the target flatness may be determined based on the method provided in the first optional implementation) and convert the target flatness at the top of the output spectrum to a target equivalent refractive index of the AWG. Then, the grating parameters are continuously adjusted using simulation software to observe the change in the equivalent refractive index of the AWG obtained through simulation. If the equivalent refractive index of the AWG obtained by simulation is equal to or close to the target equivalent refractive index, the corresponding grating parameters are determined as the grating parameters required for manufacturing the AWG. Since the equivalent refractive index of the pre-diffusion component also affects the equivalent refractive index of the AWG, the flatness of the top of the output spectrum can alternatively be converted to the target equivalent refractive index of the pre-diffusion component. Then, the grating parameters are continuously adjusted using simulation software to observe the change in the equivalent refractive index of the pre-diffusion component obtained through simulation. If the equivalent refractive index of the pre-diffusion component obtained through simulation is equal to or close to the target equivalent refractive index, the corresponding grating parameters are determined as the grating parameters required for fabricating the AWG.

The equivalent refractive index of the pre-diffusion component affects the flatness of the top of the output spectrum, and the equivalent refractive index of the pre-diffusion component is also affected by the material and thickness, so before manufacturing the AWG, staff can determine the target material and target thickness by adjusting the material and thickness of the pre-diffusion component, and then manufacture the AWG by using the target material and target thickness in the manufacturing process.

S502: Provide the substrate.

For example, the substrate material can be lithium niobate, a III-V semiconductor compound, silicon, silicon nitride, silicon dioxide, silicon, a polymer, or glass.

S503: Fabricate a first waveguide, a pre-diffusion component, a first coupler, an arrayed waveguide, a second coupler, and a second waveguide on a substrate.

The arrayed waveguide includes m waveguides, the first waveguide includes n waveguides, and the second waveguide includes p waveguides. m is a positive integer greater than 1, n and p are both positive integers, and n and p are different. The first waveguide is configured to input n optical signals to the first coupler. The first coupler is configured to couple n optical signals to the m waveguides for transmission. The second coupler is configured to couple optical signals transmitted in the m waveguides to the p waveguides for transmission. The second waveguide is configured to output p optical signals. The pre-diffusion component is located between the first waveguide and the first coupler or between the second coupler and the second waveguide. A sub-wavelength diffraction grating arranged along the extension direction of the pre-diffusion component is arranged in the region where the pre-diffusion component is located, and the pre-diffusion component is configured to adjust the flatness of the top of the output spectrum of the AWG.

The first waveguide, the pre-diffusion component, the first coupler, the arrayed waveguide, the second coupler, and the second waveguide may be fabricated using a one-time or multiple-time synthesis technique (also called photoetching technique). For example, the fabrication process includes: forming an optical waveguide material layer on a substrate plate using a deposition, coating, or sputtering technique; and performing a one-time synthesis technique on the optical waveguide material layer to obtain an AWG pattern. The AWG pattern includes the first waveguide, the pre-diffusion component, the first coupler, the arrayed waveguide, the second coupler, and the second waveguide. Optionally, the aforementioned AWG pattern may further include another structure. The one-time synthesis technique includes photoresist coating, exposure, development, etching, and photoresist lift-off. For example, in the synthesis technique, the etching process may be completed by using a dry etching process.

For example, the optical waveguide material can be silicon, silicon nitride, silicon oxynitride, or silicon dioxide.

During actual implementation, another material layer may alternatively be fabricated on the substrate based on the actual situation. For example, before the AWG pattern is fabricated on the substrate, the first protective layer may alternatively be formed using deposition, coating, or sputtering technology. Optionally, after the AWG pattern is fabricated on the substrate, the second protective layer may alternatively be formed using deposition, coating, or sputtering technology. Both the first protective layer and the second protective layer are configured to protect the AWG pattern and improve the life of the AWG pattern. For example, the material of both the first protective layer and the second protective layer is silicon dioxide.

According to the manufacturing method of the AWG provided in this embodiment of the present application, a pre-diffusion component with a sub-wavelength grating structure is added between the first waveguide and the first coupler or between the second coupler and the second waveguide of the AWG. The pre-diffusion component is configured to adjust the flatness of the top of the output spectrum of the AWG, so that a flat-top spectrum is finally output from the AWG. The 3 dB bandwidth of the flat-top spectrum is large, which can effectively reduce the insertion loss caused by the wavelength shift of the optical signal.

The aforementioned fabrication method of AWG is fully compatible with conventional AWG fabrication technology. The pre-diffusion components with sub-wavelength grating structures in the AWG pattern and other devices can be synchronously fabricated using one-time or multiple-time synthesis technology, without the need to add additional technological steps. The fabrication process is simple, easy to implement, and the fabrication cost is low.

In this application, the terms "first" and "second" are used merely for descriptive purposes and cannot be understood as an indication or implication of relative importance. The term "plurality" means two or more, unless expressly limited otherwise. "A refers to B" means that A is the same as B or that A is a simple variation of B.

It should be noted that in the accompanying drawings, the sizes of layers and regions may be exaggerated for clarity of illustration. Additionally, when an element or layer is referred to as "on" another element or layer, it can be understood that the element or layer may be directly on top of the other element, or that there may be intermediate layers. Additionally, when an element or layer is referred to as "under" another element or layer, it can be understood that the element or layer may be directly under the other element, or that there may be multiple intermediate layers or elements. Additionally, when a layer or element is referred to as "between" two layers or elements, it can be further understood that the element or layer may be a unique layer between the two layers or elements, or that there may be one or more intermediate layers or elements. Similar reference marks throughout the specification indicate similar elements.

The AWG and its manufacturing method, transceiver, and optical communication system provided in the above-mentioned embodiments belong to the same concept. For the specific implementation process, please refer to the device embodiment, and the details will not be described here.

The above description is merely an optional embodiment of the present application, but is not intended to limit the present application. Any modification, equivalent replacement, or improvement made without departing from the spirit and principles of the present application should fall within the protection scope of the present application.

Claims (12)

An arrayed waveguide grating having a first waveguide, a pre-diffusion component, a first coupler, an arrayed waveguide, a second coupler, and a second waveguide,
the arrayed waveguide has m waveguides, the first waveguide has n waveguides, and the second waveguide has p waveguides, m is a positive integer greater than 1, n and p are both positive integers, and n and p are different;
the first waveguides are configured to input n optical signals to the first coupler, the first coupler is configured to couple the n optical signals to the m waveguides for transmission, the second coupler is configured to couple the optical signals transmitted in the m waveguides to the p waveguides for transmission, and the second waveguides are configured to output p optical signals;
the pre-diffusion component is located between the first waveguide and the first coupler or between the second coupler and the second waveguide, a sub-wavelength grating arranged along an extension direction of the pre-diffusion component is arranged in a region where the pre-diffusion component is located, and the pre-diffusion component is configured to adjust the flatness of a top of the output spectrum of the arrayed-waveguide grating ;
the flatness of the apex of the output spectrum of the arrayed waveguide grating is related to grating parameters of the sub-wavelength grating, the grating parameters including a grating period and/or a duty cycle.
Arrayed Waveguide Grating. a sub-wavelength grating arranged along a first direction is further arranged on the pre-diffusion component, the first direction being perpendicular to the extension direction of the pre-diffusion component;
2. The arrayed waveguide grating of claim 1. The sub-wavelength grating is a uniform grating or a non-uniform grating.
3. The arrayed waveguide grating according to claim 1 or 2. an effective refractive index of the arrayed waveguide grating is related to a grating parameter of the sub-wavelength grating, and the effective refractive index of the arrayed waveguide grating is related to the flatness of the apex of the output spectrum of the arrayed waveguide grating;
4. The arrayed waveguide grating according to claim 1. The pre-diffusion component has an axisymmetric structure, and the axis of symmetry of the pre-diffusion component is parallel to the extension direction of the pre-diffusion component.
5. The arrayed waveguide grating according to claim 1. The pre-diffusion component is a multi-mode interference (MMI) component or is a Y-shaped structure;
6. The arrayed waveguide grating of claim 5 . the first waveguide is an axially symmetric structure, and the axis of symmetry of the pre-diffusion component is aligned with the axis of symmetry of the first waveguide;
6. The arrayed waveguide grating of claim 5 . A transmitter machine comprising a light source, a modulator, and an arrayed waveguide grating according to any one of claims 1 to 7 ,
the light source, the modulator, and the arrayed waveguide grating are connected in series, and n is greater than p;
the light source is configured to output an optical signal, the modulator is configured to modulate the received optical signal to obtain a multi-wavelength optical signal, and input the multi-wavelength optical signal to the arrayed waveguide grating;
Transmitter machine. A receiver machine comprising an arrayed waveguide grating according to any one of claims 1 to 7 and a plurality of receivers, comprising:
the arrayed waveguide grating is separately connected to the plurality of receivers, n being less than p; the receivers are configured to receive the optical signals output by the arrayed waveguide grating;
Receiver machine. 10. An optical communication system comprising a transmitter machine according to claim 8 , a receiver machine according to claim 9 , and optical fibers respectively connected to said transmitter machine and said receiver machine. 1. A method for manufacturing an arrayed waveguide grating, the method comprising:
Providing a substrate;
fabricating a first waveguide, a pre-diffusion component, a first coupler, an arrayed waveguide, a second coupler, and a second waveguide on the substrate;
the arrayed waveguide has m waveguides, the first waveguide has n waveguides, and the second waveguide has p waveguides, m is a positive integer greater than 1, n and p are both positive integers, and n and p are different;
the first waveguide is configured to input n optical signals to the first coupler, the first coupler is configured to couple the n optical signals to the m waveguides for transmission, the second coupler is configured to couple the optical signals transmitted in the m waveguides to the p waveguides for transmission, and the second waveguide is configured to output p optical signals;
the pre-diffusion component is located between the first waveguide and the first coupler or between the second coupler and the second waveguide, a sub-wavelength grating arranged along an extension direction of the pre-diffusion component is arranged in a region where the pre-diffusion component is located, and the pre-diffusion component is configured to adjust the flatness of a top of the output spectrum of the arrayed-waveguide grating ;
Prior to the step of fabricating a first waveguide, a pre-diffusion component, a first coupler, an arrayed waveguide, a second coupler, and the second waveguide on the substrate, the method may further include:
determining grating parameters of the sub-wavelength grating based on the flatness of the apex of the output spectrum of the fabricated arrayed waveguide grating, the grating parameters including a grating period and/or a duty cycle;
Method. Prior to the step of fabricating a first waveguide, a pre-diffusion component, a first coupler, an arrayed waveguide, a second coupler, and a second waveguide on the substrate, the method further comprises:
determining grating parameters of the subwavelength grating based on the equivalent refractive index of the arrayed waveguide grating to be manufactured;
The method of claim 11 .

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