A phase change optical analog-to-digital converter

Abstract

The present invention belongs to the field of optical communication technology, specifically a phase-change optical analog-to-digital converter. The phase-change optical analog-to-digital converter of the present invention includes a multimode interferometer and phase-change materials of different widths covering different output ports of the multimode interferometer; the phase-change material is a phase-change conversion material with non-volatile characteristics or a nonlinear material with a light absorption transition threshold; the crystalline phase-change material covered on the waveguide undergoes a local phase change through a light pulse, and the phase-change material becomes partially amorphous, and the crystalline state absorbs light more strongly than the amorphous state, so the transmittance of light is enhanced after the phase change; and the difficulty of phase change of phase-change materials of different widths is different, and the more difficult the phase change is, the higher the coding effective bit. The phase-change optical analog-to-digital converter of the present invention can reduce the conversion of signals between the optical-electrical-optical domains and reduce resource consumption. Compared with other optical digital-to-analog converters, the coverage of the phase-change material does not increase the additional area, so the scale is small and easy to integrate.

Description

Technical Field

[0001] The invention belongs to the technical field of optical communications, and in particular relates to a phase-change optical analog-to-digital converter. Background Art

[0002] Currently, most of the world's data is transmitted in optical fibers, which have the characteristics of high channel rate and high throughput. However, in terms of power loss and throughput, the bottleneck of information networks lies in the limitations of their edge connections and interfaces, that is, the input / output (I / O) of digital systems or sensors requires digital-to-analog / analog-to-digital conversion. In addition, electro-optical / optical-to-electrical (EO / OE) conversion is usually the most power-consuming component in typical digital signal processing (DSP)-based high-speed optical data links.

[0003] Photonic integrated circuits (PICs) have shown the potential to meet high data processing capabilities with low latency and low power consumption. However, when connected to electronic digital architectures, the performance of photonic platforms is limited by the interfaces with the electronics. These interfaces are often limited by the bandwidth and resolution of the digital-to-analog / analog-to-digital converters (DAC / ADC), in addition to the cumbersome domain crossing between electrical and optical.

[0004] All current optical networks require these conversions at their edge, and optimizing them to meet future demands for big data processing and low-latency data access has become a challenge. Moreover, the ultimate latency, throughput performance, and power consumption of digital (mixed analog-to-digital) signal processing systems are limited by CMOS processes that are rapidly approaching their fundamental physical limits. Therefore, a passive, all-optical analog-to-digital converter that can reduce the conversion in the optical-electrical-optical domain is extremely important for high-quality optical networks. Summary of the invention

[0005] Based on the above problems, the object of the present invention is to provide a phase-change optical analog-to-digital converter for optical networks to reduce the conversion of signals between optical-electrical-optical domains and reduce resource consumption.

[0006] The phase-change optical analog-to-digital converter provided by the present invention realizes the analog-to-digital converter by covering different widths of phase-change materials on different output ports of a multi-mode interferometer (MMI). There is no need to consider the increase of area when covering the phase-change material on the waveguide, and no additional power is introduced; the crystalline phase-change material covered on the waveguide undergoes a local phase change through the light pulse.

[0007] In the present invention, the phase change material can be a phase change conversion material with non-volatile properties, accompanied by a change in absorption coefficient, such as GST (specifically Ge 2 Sb 2 Te 5), Te, etc.; or other nonlinear materials with light absorption transition threshold;

[0008] The phase change material can be deposited on the waveguide by PVD, PECVD, ALD, thermal evaporation, etc.

[0009] In the present invention, the phase change material is covered with a protective layer, and the protective layer material is selected from ITO, SiO 2 、Al 2 O 3 , HfO 2 Etc. The protective layer can be deposited on the phase change material by PVD, PECVD, ALD and other methods.

[0010] The crystalline phase change material covering the waveguide undergoes a local phase change due to the light pulse, and the phase change material becomes partially amorphous. The crystalline state absorbs light more strongly than the amorphous state, so the light transmittance is enhanced after the phase change. The difficulty of phase change of phase change materials of different widths is different. The more difficult the phase change is, the higher the coding effective bit is.

[0011] For example, for a 2-bit phase change analog-to-digital converter, at least 3 channels of output are required. The state in which all three channels have not changed phase is encoded as 00, the state in which the channel most likely to change phase has changed phase is encoded as 01, the state in which the channel second most likely to change phase has changed phase is encoded as 10, and the state in which the channel most difficult to change phase has changed phase is encoded as 11.

[0012] The present invention also provides a phase-change optical analog-to-digital converter for use in an optical network that is easy to integrate, and achieves an integrated effect by cascading multiple multi-mode interferometers (e.g., 1x2MMI). Specifically, different output ports of the cascaded multi-mode interferometers are covered with phase-change materials of different widths to implement an analog-to-digital converter.

[0013] Among them, the parameters of 1x2MMI can refer to the pdk provided by the wafer manufacturer.

[0014] The phase-change optical analog-to-digital converter for optical networks of the present invention can reduce the conversion of signals between optical-electrical-optical domains and reduce resource consumption. In addition, compared with other optical digital-to-analog converters, the coverage of phase-change materials does not increase the extra area, so the scale is small and easy to integrate. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram of the structure of a 2-bit phase-change analog-to-digital converter of the present invention.

[0016] Figure 2 The schematic diagram of the structure of the 2-bit phase-change analog-to-digital converter which is easy to integrate is shown in the figure.

[0017] The numbers in the figure are: 10 is 1x3MMI, 11 is 1 micron wide GST, 12 is 2 micron wide GST, 13 is 4 micron wide GST, 14 is input port, 15 is output port 1, 16 is output port 2, 17 is output port 3, and 18 is 1x2MMI. DETAILED DESCRIPTION

[0018] Embodiment 1:

[0019] This embodiment provides a 2-bit phase-change optical analog-to-digital converter, whose structure is as follows: Figure 1 shown.

[0020] Among them, 1x3MMI (10) has a length of 40 microns, a width of 11 microns, a waveguide width of 1.3 microns, and a width between waveguides of 2.4 microns.

[0021] Choose Si wafer, Si 3 N 4 The phase change optical analog-to-digital converter is made by micro-nano processing technology on Si 3 N 4 1x3MMI is manufactured on-chip.

[0022] Using PVD technology, phase change material GST (11, 12, 13) with a thickness of 1 micron, 2 microns, and 4 microns is covered on three different output waveguides of 1x3MMI along the waveguide direction.

[0023] Using PVD technology, a protective layer of ITO is covered on GST.

[0024] The wafer was heated on a hot plate at 250°C for 5 minutes to transform the GST into a crystalline state, after which optical testing was performed.

[0025] When a laser pulse is input from the input port (14) of the phase change optical analog-to-digital converter, it passes through the 1x3MMI, where the optical power is divided into three equal parts. The optical pulse then passes through three waveguides covered with GST of different widths. The optical pulse that is larger than the critical point of the GST phase change causes the GST to undergo a local phase change.

[0026] The 4-micron-wide GST has the strongest absorption of light and therefore the easiest phase transition; the 1-micron-wide GST has the weakest absorption of light and the most difficult phase transition; the 2-micron-wide GST is in between the two.

[0027] Light detection is performed at the three output ports (15, 16, and 17) of the phase-change optical analog-to-digital converter. If a sudden change in the light transmission rate is detected, it means that a phase change has occurred in the GST on this channel.

[0028] The light pulse that causes the 4-micron GST phase change is encoded as 01, the light pulse that causes the 2-micron wide GST phase change is encoded as 10, the light pulse that causes the 1-micron wide GST phase change is encoded as 11, and the light pulse that does not cause any phase change is encoded as 00. After that, a light pulse is needed to restore the three widths of GST to their initial crystalline state before the next pulse laser is emitted.

[0029] Embodiment 2:

[0030] This embodiment provides an integrated phase-change optical analog-to-digital converter. For higher-resolution analog-to-digital converters, multiple 1x2 MMI cascades may be used.

[0031] like Figure 2 As shown, three 1x2MMI (18) cascades are used, and there are now four output channels. The waveguides of the first three channels are covered with 1 micron, 2 micron, and 4 micron phase change material GST, respectively, and one channel can be discarded.

[0032] The remaining steps are consistent with Example 1.

Claims

1. A phase change optical analog-to-digital converter, characterized in that: Specifically, a 1x3MMI optical analog-to-digital converter is manufactured on a Si3N4 wafer through micro-nano processing technology. The PVD technology is used to cover the three different output waveguides of the 1x3MMI with 1 micron, 2 micron, and 4 micron phase change materials GST along the waveguide direction. It includes a multi-mode interferometer and phase change materials of different widths covering different output ports of the multi-mode interferometer. The crystalline phase change material covering the waveguide undergoes a local phase change through light pulses. The phase change material is a phase change conversion material with non-volatile characteristics, accompanied by a change in absorption coefficient, or a nonlinear material with a light absorption transition threshold; The crystalline phase change material covered on the waveguide undergoes a local phase change through light pulses, and the phase change material becomes partially amorphous. The crystalline state absorbs light more strongly than the amorphous state, so the light transmittance is enhanced after the phase change. Different width phase change materials have different degrees of difficulty in phase change. The more difficult the phase change is, the higher the coding effective bit is. The 4-micron wide GST has the strongest absorption of light, so the phase change is also the easiest. The 1-micron wide GST has the weakest absorption of light and the most difficult phase change. The 2-micron wide GST is between the two. The phase change material is Ge2Sb2Te5 or Te.

2. The phase-change optical analog-to-digital converter according to claim 1, characterized in that: The phase change material is covered with a protective layer, and the material of the protective layer is selected from ITO, SiO2, Al2O3, and HfO2.

3. The phase-change optical analog-to-digital converter according to claim 1, characterized in that: For a 2-bit phase-change analog-to-digital converter, there are at least 3 channels of output. The state where all three channels have not changed phase is encoded as 00, the state where the channel most likely to change phase has changed phase is encoded as 01, the state where the channel second most likely to change phase has changed phase is encoded as 10, and the state where the channel most difficult to change phase has changed phase is encoded as 11.

4. The phase-change optical analog-to-digital converter according to claim 3, characterized in that: The multi-mode interferometer is composed of a plurality of sub-multi-mode interferometers connected in cascade.

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