A monolithically integrated silicon-based optical feed antenna

Abstract

The application discloses a monolithic integrated silicon-based light feed antenna, which comprises a silicon-based on-chip antenna, a germanium-silicon photodetector, a bias network and a GSG pad part. The silicon-based light feed antenna realizes high radiation power and high-efficiency transmission by photoelectric conversion of the germanium-silicon photodetector with a large bandwidth and high RF saturation power and feeding into the high-gain and high-directivity silicon-based on-chip antenna for emission into space. In addition, the device is formed in a monolithic integrated manner on a CMOS-compatible SOI substrate, the parasitic effect of traditional hybrid integrated metal wire bonding is reduced, and the device structure is compact in size, which is conducive to large-scale integration.

Description

TECHNICAL FIELD

[0001] The present application relates to an integrated optoelectronic device in analog photonic communication or microwave photonics system, and more particularly to a monolithically integrated silicon-based optical feed antenna. BACKGROUND

[0002] In the field of analog photonic communication, microwave photonics system, etc., the optical feed antenna feeds the radio frequency signal into the antenna unit after photoelectric conversion by the photodetector, and the process needs two unit devices of photodetector and antenna, which can be integrated by hybrid integration or monolithic integration. The hybrid integration technology is relatively mature, and is currently the most commonly used, but its disadvantage is that when the devices based on different materials are bonded by metal wires, there will be serious parasitic effects, the frequency is limited, and the consistency of the metal lead is poor, which is not conducive to large-scale application.

[0003] Compared with the hybrid integration technology, the monolithic integration technology can significantly reduce the manufacturing cost, eliminate the parasitic effect of the metal lead, and improve the consistency and reliability of the optical feed antenna. In 2019, Behrooz Abiri et al. of California Institute of Technology realized a 4x4 silicon-based optical feed radiation array, in which a double-end optical feed-in photodetector is used as a single photodetector unit, and a broadband log-periodic spiral antenna with a sinusoidal corrugation is used as a single antenna unit. The silicon-based optical feed radiation array is composed of H-shaped distributed optical feed radiation units with optical path delay, and the coupling power at 42GHz is-45dBm. In the array, the photoelectric bandwidth of the photodetector is less than 20GHz. On the other hand, since the influence of the high dielectric constant of the silicon substrate on the antenna radiation efficiency is not considered, and the photodetector and the antenna are not perfectly matched, the optical feed antenna array has problems such as low transmission efficiency and weak radiation power. SUMMARY

[0004] The purpose of the present application is to design a monolithically integrated silicon-based optical feed antenna to solve the problems of frequency limitation, large parasitic effect and poor large-scale integration of hybrid integrated optical feed antenna, and to realize high transmission efficiency, high directivity and high radiation power.

[0005] In order to achieve the above design goal, the technical scheme of the present application is as follows:

[0006] A monolithically integrated silicon-based optical feed antenna, the optical feed antenna is integrated with a silicon-on-silicon antenna, a germanium-silicon photodetector, a bias network and a GSG pad; the monolithically integrated silicon-based optical feed antenna is composed of a silicon-on-silicon (SOI) substrate compatible with CMOS in a monolithic integrated manner; the monolithically integrated silicon-based optical feed antenna provides direct current bias for the germanium-silicon photodetector through the GSG pad, converts the optical signal into an electrical signal by the germanium-silicon photodetector, and then transmits the electrical signal to the free space by the silicon-on-silicon antenna, and the bias network functions as a direct current pass and alternating current block.

[0007] The antenna on the silicon substrate can be any one of an on-chip Yagi antenna, an on-chip Vivaldi antenna and an on-chip spiral antenna.

[0008] The on-chip Yagi antenna comprises an excitation oscillator, a director, a reflector and a balun.

[0009] The reflector introduces a corrugated comb structure to reduce the length of the reflector and improve the gain of the antenna on the silicon substrate.

[0010] The director is a meander structure to reduce the size of the antenna on the silicon substrate.

[0011] The germanium-silicon photodetector can be any one of a single detector, a lumped detector and a traveling wave detector.

[0012] The traveling wave detector is an n-stage traveling wave detector comprising n germanium-silicon detector units, log2n 1x2 multimode interferometers (MMIs) and CPW traveling wave electrodes.

[0013] The germanium-silicon photodetector is capacitive, and the antenna on the silicon substrate is inductive, and the two are designed by conjugate matching to finally realize impedance matching.

[0014] The input end of the traveling wave detector can be an open circuit to improve the RF saturation power of the traveling wave detector, or a matching load can be added to improve the bandwidth of the traveling wave detector.

[0015] According to the packaging and testing requirements of the optical feed antenna chip, the silicon-based optical fiber coupler for optical input of the traveling wave detector can be a silicon-based end face coupler or a silicon-based grating coupler.

[0016] The biasing network is composed of a plurality of spiral inductors, which are silicon-based inductors.

[0017] The beneficial effects of the present application are:

[0018] Compared with the conventional hybrid integrated optical feed antenna, the monolithic integrated silicon-based optical feed antenna of the present application is formed in a monolithic integrated manner on a CMOS compatible silicon-on-insulator (SOI) substrate, and the metal wire bonding is eliminated, thereby solving the problems of large parasitic effect and limited frequency in hybrid integration, and facilitating large-scale integration. In addition, the present application adopts a germanium-silicon photodetector with a large bandwidth and high RF saturation power, and an on-chip antenna with high gain and high directivity, and the capacitive characteristic of the germanium-silicon photodetector and the inductive characteristic of the antenna on the silicon substrate are used for conjugate matching design between the two, and the balun is used for transition connection and conversion, so that a silicon-based optical feed antenna with high radiation power can be finally realized. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 is a monolithic integrated silicon-based optical feed antenna of the present application;

[0020] Figure 2 is a schematic diagram of a traveling wave detector structure;

[0021] Figure 3 is a schematic diagram of an on-chip spiral inductor structure;

[0022] In the figure: 1, a silicon-based on-chip antenna, 2, a germanium-silicon photodetector, 3, a bias network, 4, a GSG pad, 5, a director, 6, an excitation vibrator, 7, a coplanar strip line CPS, 8, a balun, 9, a corrugated comb structure, 10, a reflector, 11, a silicon-based optical fiber coupler, 12, a 1x2 multimode interferometer MMI, 13, a germanium-silicon detector unit, 14, a coplanar waveguide CPW, 15, a traveling wave detector input end, 16, a spiral inductor. DETAILED DESCRIPTION

[0023] The present application will be further described below in conjunction with the accompanying drawings and examples. Obviously, the described examples are only a part of the examples of the present application, rather than all the examples. Based on the examples in the present application, all other examples obtained by those skilled in the art without making creative efforts fall within the scope of protection of the present application.

[0024] As Figure 1 A monolithic integrated silicon-based optical feed antenna of the present application comprises a silicon-based on-chip antenna 1, a germanium-silicon photodetector 2, a bias network 3 and a GSG pad 4. The present application is made based on a complementary metal oxide semiconductor (CMOS) process and integrates the optical feed antenna on a silicon-on-insulator (SOI substrate). The silicon-based on-chip antenna 1 adopts an on-chip Yagi antenna to improve the antenna gain and directivity; the germanium-silicon photodetector 2 adopts a traveling wave detector to improve the RF saturation power while improving the detector bandwidth.

[0025] As Figure 1 shown, the on-chip Yagi antenna comprises an excitation vibrator 6, a director 5, a reflector 10 and a balun 8. Among them, the director 5 is segmented to enhance the coupling of the driving element; the reflector 10 simultaneously serves as a floor and introduces a corrugated comb structure 9 to reduce the length of the reflector 10 and improve the gain of the silicon-based on-chip antenna 1; in order to reduce the size of the on-chip antenna, the director 5 is a meandering structure; the balun 8 is a conversion transition structure between the coplanar waveguide CPW 14 and the coplanar strip line CPS 7, so as to realize the connection between the silicon-based on-chip antenna 1 and the germanium-silicon photodetector 2.

[0026] Figure 2As a schematic diagram of the traveling wave detector, an input optical signal is injected by a silicon-based optical fiber coupler 11, enters a log2n 1x2 multimode interferometer (MMI) 12 and is evenly distributed to n germanium-silicon detector units 13 for photoelectric conversion, and the generated photocurrent is collected by a CPW traveling wave electrode. The traveling wave detector distributes the photocurrent to the n germanium-silicon detector units 13 to improve the RF saturation power while improving the detector bandwidth. The optical delay line length corresponding to the nth germanium-silicon detector unit 13 is d n When the spacing Δ between adjacent germanium-silicon detector units 13 is large, a proper optical delay line is needed for photoelectric speed matching; when the spacing Δ between adjacent germanium-silicon detector units 13 is small, it is preferable that d n =…d2=d1. The input end 15 of the traveling wave detector can be open-circuited to improve the RF saturation power of the traveling wave detector, or a matching load can be added to improve the bandwidth of the traveling wave detector.

[0027] To provide direct current bias for the traveling wave detector while isolating the alternating current signal generated by the traveling wave detector, the application designs a direct current passing and alternating current isolating bias network 3. As shown in Figure 3 , the coil width w ind , the inner diameter d in and the outer diameter d out of the single on-chip spiral inductor 16 constituting the bias network 3 are determined according to the required inductance value L ind of the circuit, and L ind is generally of the order of pH.

[0028] The working principle of the application is as follows: when an optical signal is fed into a silicon-based optical feed antenna, the traveling wave detector converts the optical signal into an electrical signal, and the generated RF electrical signal is all fed into the on-chip Yagi antenna and converted into an electromagnetic wave to be emitted into free space. The working voltage of the traveling wave detector is provided by the GSG pad 4. Due to the direct current passing and alternating current isolating characteristics of the designed bias network 3, the alternating current signal generated by the traveling wave detector will all be fed into the silicon-based on-chip antenna 1 end rather than the GSG pad 4 end. In addition, the traveling wave detector is capacitive, and the silicon-based on-chip antenna is inductive, and the two are designed through conjugate matching to achieve impedance matching.

[0029] Based on the traveling wave detector with large bandwidth and high RF saturation power and the on-chip Yagi antenna with high gain and high directivity, the application finally realizes a monolithic integrated optical feed antenna with high radiation power, and the device structure size is relatively compact without increasing the process complexity. The application can be applied to an analog photonic communication system or a microwave photon system as a standalone device, or can be large-scale integrated on a chip based on a CMOS process, greatly reducing the cost, size and power consumption.

[0030] Although the present application has been described in detail with reference to the foregoing embodiments, the technical solutions recorded in the foregoing embodiments can be modified or some technical features can be replaced by equivalent features by those skilled in the art, and any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A monolithically integrated silicon-based optical feed antenna, characterized in that: The device includes a germanium-silicon photodetector, a silicon on-chip antenna, a bias network, and a GSG pad. The GSG pad provides DC bias for the germanium-silicon photodetector. The germanium-silicon photodetector converts optical signals into electrical signals. The silicon on-chip antenna transmits the electrical signals into free space. The bias network acts as a DC-passing, AC-blocking network to ensure that all electrical signals generated by the germanium-silicon photodetector are fed into the silicon on-chip antenna. The monolithically integrated silicon-based optical antenna is constructed on a CMOS-compatible silicon-on-insulator (SOI) substrate. The bias network consists of multiple spiral inductors. The germanium-silicon photodetector is capacitive, and the on-chip antenna is inductive; the two employ a conjugate matching design.

2. The monolithically integrated silicon-based optical feed antenna according to claim 1, characterized in that: The silicon-based on-chip antenna can be any one of an on-chip Yagi antenna, an on-chip Vivaldi antenna, or an on-chip helical antenna.

3. The monolithically integrated silicon-based optical feed antenna according to claim 2, characterized in that: The on-chip Yagi antenna includes an excitation element, a director, a reflector, and a balun.

4. The monolithically integrated silicon-based optical feed antenna according to claim 3, characterized in that: The balun is a transition structure between a coplanar waveguide and a coplanar stripline.

5. The monolithically integrated silicon-based optical feed antenna according to claim 3, characterized in that: The reflector incorporates a corrugated comb-like structure to reduce reflector length and improve antenna gain on the silicon substrate.

6. The monolithically integrated silicon-based optical feed antenna according to claim 3, characterized in that: The director is a meandering structure to reduce the antenna size on the silicon substrate.

7. The monolithically integrated silicon-based optical feed antenna according to claim 1, characterized in that: The germanium-silicon photodetector can be any one of a single detector, a lumped detector, or a traveling wave detector.

8. The monolithically integrated silicon-based optical feed antenna according to claim 7, characterized in that: The traveling wave detector is an n-level traveling wave detector, comprising n germanium-silicon detector units, log2n 1×2 multimode interferometers (MMIs), and CPW traveling wave electrodes.

9. The monolithically integrated silicon-based optical feed antenna according to claim 7, characterized in that: The input terminal of the traveling wave detector can be either open-circuit or have a matched load.

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