DE102021214145A1 - HETEROGENE INTEGRATION OF FREQUENCY COMB GENERATORS FOR HIGH-SPEED TRANSCEIVERS - Google Patents

Abstract

A photonic frequency comb generator includes two integrated dies: an indium phosphide die on which a first wavelength laser is grown, and a silicon photonic die with a micro ring resonator connected to the laser and frequency modulators. The micro ring resonator converts the first wavelength into a number of second wavelengths. One type of micro ring resonator is a hybrid non-linear optical wavelength generator that includes non-silicon materials such as SiC or SiGe on silicon to achieve non-linear wavelength generation. The second wavelengths are generated by adjusting the geometric size of the ring and the spacing between the ring and the traverse waveguide. Another type of micro ring resonator splits the first wavelength into a plurality of second wavelengths and transmits the plurality of second wavelengths to filters and modulators that each select and modulate one of the second wavelengths in a one-to-one relationship. This frequency comb generator finds application in WDM/CWDM and multi-chip modules in high-speed transceivers.

Description

CROSS REFERENCE

The application claims priority to Greek Patent Application No. 20200100735 , filed December 16, 2020, the disclosure of which is incorporated herein by reference in its entirety.

TECHNICAL AREA

The invention relates to the field of telecommunications. In particular, the invention relates to high-speed photonic transceivers for interconnects.

BACKGROUND

Data centers depend on a fast and robust communication infrastructure. This is achieved through the use of optical connections, particularly between different server racks. Any physical connection using a single optical fiber comprises multiple communication channels, characterized by different wavelengths in WDM (Wavelength Division Multiplexing) systems.

The transmitters in WDM optical transceiver modules are typically based on arrays of discrete single-wavelength lasers, such as B. the distributed feedback lasers (DFB). However, to reduce power consumption and complexity, these lasers could be replaced with a single comb laser. The comb laser generates a series of discrete, evenly distributed frequencies.

As transceivers increase their line bit rate from the current 25 Gbit/s to 50 Gbit/s and later to 100 Gbit/s and the modulation order from current techniques such as Non-Return-to-Zero (NRZ) to Pulse Amplitude Modulation Level 4 (PAM-4), the challenge is to scale the power consumption of the laser sources, as these increases require an increase in the signal-to-noise ratio (SNR) of the transmitter.

For example, going from NRZ to PAM-4 at the same bitrate reduces SNR by a factor of 3. Therefore, performance must increase by a factor of 3, just by the same number of bit error rates (BER) to be retained as before.

When moving from PAM-4 to PAM-8 (PAM level 8), both of which operate at the same bit rate, the SNR must be increased in order for the PAM-8 signal to achieve the same BER as PAM-4.

In order to achieve a sustainable relationship between SNR and BER, the available power of the laser source usually has to be increased, which increases costs. As a result, the lasers must produce more light, which in turn increases power consumption beyond linear scaling while making heat dissipation and thermal management more difficult.

This is especially important for transceivers that need to be encapsulated in standardized pluggable forms that have limited heat dissipation properties and space constraint, requiring them to rely on an airflow design, reducing the amount of power transceivers can absorb from the main rack by the Form factor standards is limited.

Frequency comb generators attempt to replace arrays of discrete laser sources with a single, single-wavelength laser source. The light from the laser is then split into several different light beams with different wavelengths, and each of these beams is used to transmit an individual data stream.

Traditional frequency comb generators have been built with discrete components for applications that require a large footprint, such as B. in the areas of measurement technology and sensors. However, such devices are bulky and do not meet the requirements of integrated photonics.

The existing integrated frequency comb generators are designed either for silicon photonics platforms or for other III-V semiconductor platforms such as indium phosphide (InP) based optical devices. A general diagram for each of the technologies is in 1A and 1B shown.

1A shows a schematic of an existing frequency comb generator based only on silicon photonics. the inside 1A The silicon photonics approach shown always requires an external laser source, which can be flip-chip mounted on the silicon photonics die or connected via an input fiber connection. The combined or divided frequency outputs are presented as a series of outputs connected to optical fibers.

On the other hand, in the indium phosphide method, as in 1B shown to be grown within the indium phosphide die. At the same time, the other components are arranged to be grown on the indium phosphide die. In 1B the system does not require an external laser source, simplifying the system-on-chip concept. The combined or divided frequency outputs are shown as an array of outputs connected to optical fibers.

In both cases, optical fibers are configured to connect to the system die by either V-grooves or vertical gratings. As described above, most frequency comb generator approaches focus on a single technology platform: either full silicon photonics or just indium phosphide.

The following tables list the advantages and disadvantages of current frequency comb generators based on each technology: Table 1 lists the advantages and disadvantages of frequency comb generators in an all-silicon photonics system, and Table 2 lists the advantages and disadvantages of frequency comb generators in an all-silicon indium phosphide system. Table 1 silicon photonics advantages Disadvantages Low cost Low yield due to laser attachment High input losses in the waveguides Table 2 indium phosphide advantages Disadvantages Laser grown on die High costs Reinforcement blocks can be added Lots of noise due to gain

Therefore, the problem arises of how to move from the current design focused on a single technology to a heterogeneous integration in which both technologies are used for the most appropriate purposes (i.e. indium phosphide for light generation and silicon photonics for light modulation). ).

Therefore, there is still a need to develop a frequency comb generator that is compatible with integrated circuits (IC) and can be integrated into photonic chips.

SHORT SUMMARY

The invention is defined by the claims. Aspects and embodiments are described herein for purposes of illustration of the invention, which may or may not fall within the scope of the claims.

According to an embodiment of the present disclosure, there is provided a photonic frequency comb generator, comprising: a first die, the first die comprising a light source grown on an indium phosphide material; a second die, the second die comprising an optical wavelength generator disposed on a silicon photonic substrate, the first die and the second die being integrated together; an input terminal connected to the first die; and an output terminal connected to the second die.

In some examples, the light source is a laser grown on the indium phosphide material, the laser emitting a first wavelength.

In some examples, the optical wavelength generator is a micro ring resonator connected to the laser.

In some examples, the silicon photonics substrate includes: filters and modulators connected to the micro ring resonator; wherein the micro ring resonator is configured to convert the first wavelength into a plurality of second wavelengths; and wherein one of the filters selects one of the plurality of second wavelengths and transmits that wavelength to one of the modulators in a one-to-one relationship.

According to another embodiment of the present disclosure, there is provided a photonic frequency comb generator, comprising: a first die, the first die comprising a light source grown on an indium phosphide material; a second die, the second die comprising a non-linear optical wavelength generator disposed on a silicon photonic substrate, the first die and the second die being integrated together; an input terminal connected to the first die; and an output terminal connected to the second die.

In some examples, the light source is a laser grown on the indium phosphide material, the laser emitting a first wavelength.

In some examples, the non-linear optical wavelength generator is a micro ring resonator comprised of hybrid materials coupled to the laser.

In some examples, the hybrid materials are made of non-silicon materials such as silicon carbide (SiC) or silicon germanium (SiGe).

In some examples, the SiC material is fabricated using a technique that includes: 1) growing SiC on a silicon photonic substrate through an interlayer or PVD deposition; 2) flip-chip a SiC die directly onto the silicon photonic substrate; 3) flip-chip the SiC die directly onto the silicon photonic substrate; 4) attaching the SiC die through a polymer glass interposer with the silicon carbide die and the silicon photonic substrate juxtaposed; and 5) attachment through a fiber connected to the SiC die and the silicon photonic substrate through waveguide tapers.

In some examples, a waveguide bus connects a plurality of micro ring modulators to the micro ring resonator, and the micro ring resonator is configured to convert the first wavelength into a plurality of second wavelengths, the plurality of second wavelengths being distributed from the micro ring resonator into the wave guide bus, and wherein one of the plurality of micro ring modulators selects one of the plurality of second wavelengths from the waveguide bus and transmits into the micro ring modulators in a one-to-one relationship.

In some examples, the conversion of the first wavelength into a plurality of second wavelengths is accomplished by adjusting the geometric size of the micro-ring resonator and the spacing between the micro-ring and the waveguide bus.

In some examples, the light source grown on the indium phosphide material is a semiconductor optical amplifier (SOA) to amplify the first wavelength emitted by a laser oscillator on the second die.

According to another embodiment of the present disclosure, there is provided a multi-chip module having a photonic frequency comb generator, comprising: a first die having a Light source grown on an indium phosphide material; a second die, the second die comprising an optical wavelength generator disposed on a silicon photonics substrate; wherein the first die and the second die are connected by an optical waveguide; an input terminal connected to the first die; and an output terminal connected to the second die.

In some examples, the optical waveguide connecting the first die and the second die comprises an optical fiber, a polymer waveguide, or a glass waveguide.

In some examples, the light source is a laser grown on the indium phosphide material, the laser emitting a first wavelength.

In some examples, the optical wavelength generator is a micro ring resonator connected to the laser.

In some examples, the silicon photonics substrate includes: multiple channels of filters and modulators connected to the microring resonator; wherein the micro ring resonator is configured to convert the first wavelength into a plurality of second wavelengths; and wherein one of the filters selects one of the plurality of second wavelengths and transmits that wavelength to one of the modulators in a one-to-one relationship.

In some examples, a third die is provided that is coupled to the second die, the third die being an electronic die that includes circuitry for electronic signal processing, including equalization, encoding, switching, and logic operations.

In accordance with another embodiment of the present disclosure, a multi-chip module (MCM) has N photonic frequency comb generators each comprising a first die and second die pair.

In some examples, the MCM also includes an electronic die connected to the N photonic frequency comb generators via a multi-lane waveguide, the electronic die including circuitry for electronically manipulating signals, including equalization, encoding, switching, and logic operations.

According to another embodiment of the present disclosure, an M-channel WDM module is provided that includes the photonic frequency comb generators described above.

In some examples, a number of filters and a number of modulators are both Mx4, where M is a positive integer 1,2,...M and Mx4 equals 4,8,...M.

According to another embodiment of the present disclosure, an M-channel CWDM module is provided that includes the photonic frequency comb generators described above.

In some examples, a number of filters and a number of modulators are both M'×4, where M' is a positive integer 1, 2,...M'.

In one embodiment, a photonic frequency comb generator includes two integrated dies: an indium phosphide die on which a laser of a first wavelength is grown, and a silicon photonic die with a micro ring resonator connected to the laser and frequency modulators. The micro ring resonator converts the first wavelength into a number of second wavelengths. One type of micro ring resonator is a hybrid non-linear optical wavelength generator that includes non-silicon materials such as SiC or SiGe on silicon to achieve non-linear wavelength generation. The second wavelengths are generated by adjusting the geometric size of the ring and the spacing between the ring and the traverse waveguide. Another type of micro ring resonator splits the first wavelength into a plurality of second wavelengths and transmits the plurality of second wavelengths to filters and modulators that each select and modulate one of the second wavelengths in a one-to-one relationship. This frequency comb generator finds application in WDM/CWDM and multi-chip modules in high-speed transceivers.

Each feature of one aspect or embodiment may be applied to other aspects or embodiments, in any suitable combination. In particular, any feature of a method aspect or embodiment may be applied to an apparatus aspect or apparatus embodiment and vice versa.

character list

• 1A zeigt ein schematisches Diagramm eines bestehenden Frequenzkammgenerators, der ausschließlich auf Silizium-Photonik-Technologie basiert;
• 1B zeigt ein schematisches Diagramm eines bestehenden Frequenzkammgenerators, der nur auf Indiumphosphid-Technologie basiert;
• 2 zeigt einen hybriden Frequenzkammgenerator mit einem Indiumphosphid-Die, der auf einen Silizium-Photonik-Die Flip-Chip-montiert ist, gemäß einigen Ausführungsformen der vorliegenden Offenbarung;
• 3 zeigt ein schematisches Diagramm eines Frequenzkammgenerators mit einem Bus-Wellenleiter, gefolgt von mehreren Mikroringmodulatoren, gemäß einigen Ausführungsformen der vorliegenden Offenbarung;
• 4A zeigt ein schematisches Diagramm einer beispielhaften Konfiguration mit dem InP-Laser-Die, der mit dem Frequenzkammgenerator auf dem Silizium-Photonik-Die verbunden ist, gemäß einigen Ausführungsformen der vorliegenden Offenbarung;
• 4B zeigt ein schematisches Diagramm einer anderen beispielhaften Konfiguration mit einem hybriden InP-Die, der eine Laser-/Verstärkerquelle enthält, die an den Silizium-Photonik-Die angeschlossen ist, der einen Laserresonator und einen Frequenzkammgenerator enthält, gemäß einigen Ausführungsformen der vorliegenden Offenbarung;
• 5A zeigt ein schematisches Blockdiagramm eines Frequenzkammgenerators mit 4-Kanal-Schema gemäß einigen Ausführungsformen der vorliegenden Offenbarung;
• 5B zeigt ein schematisches Blockdiagramm eines Frequenzkammgenerators mit N-Kanal-Schema gemäß einigen Ausführungsformen der vorliegenden Offenbarung;
• 6A-6C zeigen schematische Darstellungen von drei Arten von Frequenzkammgeneratoren, die in Multi-Chip-Modulen (MCM) implementiert sind, in denen ein Indiumphosphid-Die, ein Silizium-Photonik-Die und ein zusätzlicher elektronischer Die verwendet werden, gemäß einigen Ausführungsformen der vorliegenden Offenbarung;
• 7 zeigt ein schematisches Diagramm eines Frequenzkammgenerators für Wavelength Division Multiplexing (WDM) gemäß einigen Ausführungsformen der vorliegenden Offenbarung; und
• 8 zeigt ein schematisches Diagramm eines Frequenzkammgenerators für coarse Wavelength Division Multiplexing (CWDM) im Doppelbetrieb gemäß einigen Ausführungsformen der vorliegenden Offenbarung.

Having thus generally described the invention, reference should now be made to the accompanying drawings, which are not necessarily drawn to scale.

• 1A shows a schematic diagram of an existing frequency comb generator based solely on silicon photonics technology;
• 1B Figure 12 shows a schematic diagram of an existing frequency comb generator based only on indium phosphide technology;
• 2 12 shows a hybrid frequency comb generator with an indium phosphide die flip-chip mounted on a silicon photonics die, in accordance with some embodiments of the present disclosure;
• 3 12 shows a schematic diagram of a frequency comb generator with a bus waveguide followed by multiple micro ring modulators, according to some embodiments of the present disclosure;
• 4A 12 shows a schematic diagram of an example configuration with the InP laser die connected to the frequency comb generator on the silicon photonics die, according to some embodiments of the present disclosure;
• 4B 12 shows a schematic diagram of another exemplary configuration with a hybrid InP die containing a laser/amplifier source connected to the silicon photonic die containing a laser resonator and a frequency comb generator, according to some embodiments of the present disclosure;
• 5A 12 shows a schematic block diagram of a frequency comb generator with 4-channel scheme according to some embodiments of the present disclosure;
• 5B 12 shows a schematic block diagram of a frequency comb generator with N-channel scheme according to some embodiments of the present disclosure;
• 6A-6C 12 show schematic diagrams of three types of frequency comb generators implemented in multi-chip modules (MCM) using an indium phosphide die, a silicon photonic die, and an additional electronic die, according to some embodiments of the present disclosure;
• 7 12 shows a schematic diagram of a wavelength division multiplexing (WDM) frequency comb generator according to some embodiments of the present disclosure; and
• 8th 12 shows a schematic diagram of a dual mode coarse wavelength division multiplexing (CWDM) frequency comb generator, according to some embodiments of the present disclosure.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is described in more detail below with reference to the accompanying drawings, in which some, but not all, embodiments of the invention are illustrated. Indeed, these inventions may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like numbers refer to like elements throughout. Terms such as "top", "bottom", "front", etc. are used in the examples below for explanatory purposes to describe the relative position of certain components or portions of components. Accordingly, for example, the term “upper power grid layer” may be used to describe a power grid layer; however, the power distribution layer may be on top or bottom depending on the orientation of the item being written.

With the advent of photonics integrated circuits, frequency comb generators can now be integrated into photonic dies, making them small in size for use in integrated transceivers.

2 10 shows a hybrid frequency comb generator according to some embodiments of the present disclosure. In 2 is an indium phosphide die mounted on a silicon photonic die, and a series of fibers or waveguides serve as inputs and outputs.

3 FIG. 12 shows a schematic diagram of a frequency comb generator according to some embodiments of the present disclosure.

In 3 For example, the frequency comb generator includes a laser, a micro ring resonator, a bus waveguide with multiple wavelength lines, and a number of micro ring modulators tuned to each wavelength line such that each micro ring modulator directly modulates a wavelength line. Therefore, certain wavelength lines are extracted and individually modulated by corresponding micro ring resonators.

The indium phosphide die contains a laser source and/or a semiconductor optical amplifier (SOA). The laser has a narrow frequency band and emits UV, visible or IR light. The laser can be a fiber laser or a VCSEL laser mounted on a III-V semiconductor substrate, e.g. B. the InP die, but is not limited only to the InP die.

The laser light is routed through an integrated coupling to an input of a micro ring resonator on the silicon photonic die. The micro ring resonator broadens the wavelength of the laser by a non-linear property that narrows the wavelength bandwidth of the laser source to a number of wavelengths s, wavelength 1 to wavelength N (see 3 ), or simply extends to wavelengths in a broader spectrum.

To achieve this, a mechanism for generating non-linear light from the single wavelength of the laser output is required. In order to increase the non-linearity of the micro ring resonator, the micro ring resonator can be built with a heterogeneous structure, i. H. on silicon photonics using non-silicon material e.g. B. silicon carbide or silicon germanium (SiGe), instead of just silicon material. In this way, the micro ring resonator can provide high non-linear mixing and create multi-wavelength spread of the incoming wavelength signal from the indium phosphide laser/amplifier. This silicon-based hybrid non-linear micro-ring resonator requires a manufacturing process that allows for the growth of the non-silicon materials on, or is compatible with, the silicon die, or at least can be integrated with the non-silicon die.

The choice of SiC is based on some advantageous properties of the material. SiC has a wide band gap (2.4 to 3.2 eV), which corresponds to a wide, low-loss transmission window (400-5000 nm) covering the operational transmission band for fiber optic communications. SiC fabrication is compatible with complementary metal-oxide-semiconductor (CMOS), as opposed to incompatible Indium Gallium Arsenide (InGaAs), Aluminum Nitride (AlN), and Lithium Niobate (LiNbO3). ). SiC has both second and third order optical nonlinearity, since the generation of frequency combs is due in part to its high third order nonlinearity. In addition, silicon carbide has good thermal conductivity, with the thermal conductivity coefficient being three times higher than that of silicon.

A micro ring resonator can be manufactured with SiC in a CMOS-compatible process in the temperature range of 800 to 1000 degrees Celsius for monocrystalline 3C-SiC or 400 to 800 degrees Celsius for amorphous and nanocrystalline 3C-SiC. Methods such as chemical vapor deposition (CVD), physical vapor deposition (PVD), or plasma-enhanced chemical vapor deposition (PECVD) can be used.

In some cases, crystalline SiC is required on SiO ₂ and SiC cannot be grown directly on SiO ₂ . A new SiC die consisting only of SiC can be connected to the silicon photonic die by a die-to-die connection method, e.g. B. by transferring the SiC thin film to a SiO ₂ film on a substrate, z. a silicon wafer or a silicon-on-insulator (SOI). tor) wafers with a very thin silicon cap layer, or by surface treatment to form a buffer layer before growing the SiC layer on a silicon-based substrate.

In summary, there are different techniques to fabricate the hybrid microring resonator with SiC: 1) growth of SiC on silicon photonics through an interlayer plus PVD deposition; 2) Flip chip from SiC die directly on silicon photonics with light input and output through waveguide; 3) Flip chip from SiC die directly on silicon photonics with light input and output through vertical grating couplers; 4) attaching through a polymer glass interposer where the silicon carbide die and the silicon photonic die are juxtaposed; and 5) attaching the SiC die by a fiber connected to each die by waveguide tapers.

The techniques for fabricating the hybrid micro ring resonator with SiC are not limited to the methods listed above, and other techniques can be used as long as they allow high manufacturing yields while maximizing optical light transmission from the silicon carbide die to the silicon photonics die. The ensure.

As in 3 As shown, the output of the wide-wavelength (wavelength 1 to wavelength N) micro-ring resonator is coupled to a multi-wavelength transverse bus waveguide, followed by a number of micro-ring modulators tuned to individual wavelengths such that each micro-ring modulator modulates one wavelength directly . Therefore, specific wavelengths are extracted by corresponding micro ring resonators and modulated individually. Each of the N micro ring modulators is tailored to a different wavelength.

By adjusting the diameter of the micro ring resonator and the decoupling distance between ring and traverse waveguide, the free spectral range and thus the wavelength difference of N channels in the frequency comb can be selected.

4A 12 shows a schematic diagram of an example configuration with the InP laser die connected to the frequency comb generator on the silicon photonics die, in accordance with some embodiments of the present disclosure.

Dividing the different system functions into different materials leads to different configurations. As in 4A shown, the laser is implemented on the InP die and the micro ring resonator for comb generation on the silicon photonic (SiPh) die. Other components, such as the optical filters that generate wavelengths 1 through N and the micro ring modulators are also implemented on the silicon photonic die. It is also possible to use a non-linear non-silicon material such as SiC on the silicon substrate for ridge generation.

4B 10 shows a schematic diagram of another exemplary configuration with a hybrid InP die containing a laser/amplifier source connected to the silicon photonic die containing a laser resonator and a frequency comb generator, according to some embodiments of the present disclosure.

In another, in 4B configuration shown, the laser resonator can be hybrid. The laser oscillator is built on the side of the silicon photonic die, while the gain block that enables amplification by the semiconductor optical amplifier (SOA) is grown on the InP die. The other optical filter components and feedback mechanisms for generating wavelengths 1 through N are also fabricated on the silicon photonic die, e.g. B. a Bragg grating or an arrangement of a micro ring resonator and optical waveguide couplers.

A transverse bus waveguide, as in 3 shown in 4A and 4B used after the micro ring resonator. The individual wavelengths are also modulated in a similar way. Therefore, the functions and structures of these modulation parts are not repeated here.

There are various techniques for modulating the light emerging from the frequency comb generator. In another exemplary embodiment, the micro ring resonator generates a series of signals with equidistantly spaced wavelengths, which are then filtered by special filters. Each filter has a center wavelength designed to correspond to only one of the signals at that wavelength. The signal from this filter, which is a narrow band of wavelengths (sometimes referred to as a single wavelength although it has a bandwidth), is then fed to an optical modulator, e.g. B. one Mach-Zehnder modulator, which modulates the optical signal with an electrical signal. The electrical signal can be a non-return-to-zero (NRZ) modulator, a four-level pulse amplitude modulator (PAM-4), or a modulator that is any multi-level applies signal transmission technology, e.g. B. the encoding of digital information in any format.

At the in 5A and 5B In the filter technique shown, a special filter is used for each frequency comb line that responds to a wavelength band. This dedicated filter extracts the wavelength band and sends it to a comb line, and a modulator performs phase or amplitude modulation depending on the application. The modulator can be a Mach-Zehnder modulator or a micro ring modulator.

5A FIG. 12 shows a schematic block diagram of a frequency comb generator with a four-channel scheme, according to some embodiments of the present disclosure. In the four-channel scheme of 5A the four-channel frequency comb generator system includes a light source on an indium phosphide die. The light source can be a laser and/or an amplifier combined in the laser block. The single wavelength laser light emitted is guided into a micro ring resonator on the silicon photonic die. The micro ring resonator combs several lines with different frequencies, a number of filters are used to separate the lines of the frequency comb and a number of modulators, each following one of the filters, are used to modulate this frequency line independently. in the in 5A In the four channel example shown, the micro ring resonator is connected to four channels and each channel consists of a filter and a modulator connected in series. The outputs of the four channels are combined in optical fiber cables.

5B shows another system similar to 5A , but with N-channels. The descriptions of the N-channel system should be similar to the four-channel scheme above and are therefore not repeated here.

In some other applications, the frequency comb generator is used in large multi-chip modules (MCM). As a rule, the indium phosphide dies and the silicon photonic dies do not have to be integrated together. Instead, they are connected to each other via a fiber connection or polymer flex waveguide.

6A-6C 12 show schematics of three types of frequency comb generators implemented in multi-chip modules (MCM) that include an indium phosphide die, a silicon photonic die, and an additional electrical die, according to some embodiments of the present disclosure.

Separate dies can be used for the three types of frequency comb generators in large MCM dies that do not need to be integrated as in the systems described above. Examples of these systems are described below and in the 6A until 6C shown.

In 6A there are two dies - the InP die 1 and the silicon photonic die 2. The laser source is fabricated on an indium phosphide material (die 1) and a second integrated circuit is fabricated in a silicon photonic die (die 2) . The two dies are interconnected by a line of fiber, polymer waveguide, glass waveguide, or other interconnection lines. The silicon photonic die (die 2) contains a micro ring resonator to complete the frequency comb operation, as well as filter and modulation blocks to select and modulate each individual frequency line.

In 6B is the system in 6A augmented with a third die (Die 3), which is an electronic die containing all systems for electronically processing signals, including but not limited to equalization, encoding, switching, and logical operations.

In 6C the implementation of the multi-chip module (MCM) is further expanded. A central die 4 (electronics) containing all signal processing electronics is surrounded by N pairs of photonic dies, each pair comprising an indium phosphide die 1 for the light source and a silicon photonic die 2 for frequency combining, and the die 1 and die 2 are connected by an optical fiber channel, a polymer waveguide or a glass waveguide, similar to FIG the in 6A described system. The central electronic die 4 is connected to each of the photonic pairs die 1 and die 2 by M traces of electrical connections, which may include power traces as well as low frequency and high frequency traces.

The integration of frequency comb generators into transceivers also offers the possibility of driving a transceiver from a wavelength WDM source, e.g. a four-wavelength channel scheme, to coarse-WDM (CWDM) as with eight wavelength channels. The similar frequency comb generators can be used to generate either four wavelengths to feed a WDM link or eight wavelengths to feed a CWDM link. The following figures describe these extensions.

7 FIG. 12 shows a schematic diagram of a frequency comb generator for WDM operation, according to some embodiments of the present disclosure.

In 7 a laser is built on an indium phosphide die, followed by a micro ring resonator, filters and modulators on a silicon photonic die. The output signal of the laser is broadened or divided non-linearly by the micro ring resonator and divided into four channels by the WDM method. The outputs of the four channels are combined into waveguide or fiber optic cables.

8th FIG. 12 shows a schematic diagram of a frequency comb generator for dual mode CWDM, according to some embodiments of the present disclosure.

8th shows an extension of the four-channel WDM system to an eight-channel system. CDWM is a WDM technology for metro and access networks. Typically, the transmission is realized via 8 channels with wavelengths between 1270 nm and 1610 nm. Due to the channel spacing of relatively coarse (coarse) 20 nm, inexpensive lasers can be used. In 8th the eight-channel CWDM combines two of the in 7 illustrated four-channel WDMs. A laser is built on the indium phosphide die, the output signal of which is non-linearly broadened or divided by the micro ring resonator, resulting in eight wavelength bands (4+4) which are divided into two different buses by WDM methods. The laser and the micro ring resonator are shared by all channels of the WDMs. The following filters and modulators are built on two silicon photonic dies, each responsible for a four-channel WDM. The outputs of the four channels are combined into waveguide or optical fiber cables. This scheme can be used in combination with the approaches in 3 or 5B be used.

Many modifications and other embodiments of the inventions set forth herein will come to mind to one skilled in the art to which these inventions pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. It is therefore to be understood that the inventions are not limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a general and descriptive sense only and not for purposes of limitation.

It is understood that the aspects and embodiments described above are exemplary only and that changes may be made in detail within the scope of the claims.

Each apparatus, method, and feature disclosed in the description and (where appropriate) claims and drawings may be provided independently or in any suitable combination.

Reference signs contained in the claims are for illustrative purposes only and have no limiting effect on the scope of the claims.

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• GR 20200100735 [0001]

Claims (22)

Photonic frequency comb generator comprising: a first die, the first die comprising a light source grown on an indium phosphide material; a second die, the second die comprising an optical wavelength generator disposed on a silicon photonic substrate; an input terminal connected to the first die; and an output port connected to the second die. Photonic frequency comb generator claim 1 , wherein the first die and the second die are integrated with each other. Photonic frequency comb generator claim 1 , wherein the first die and the second die are connected by an optical waveguide. Photonic frequency comb generator claim 3 , wherein the optical waveguide connecting the first die and the second die comprises either an optical fiber, a polymer waveguide or a glass waveguide. A photonic frequency comb generator according to any one of the preceding claims, wherein the optical wavelength generator is a non-linear optical wavelength generator. A photonic frequency comb generator as claimed in any preceding claim, wherein the light source is a laser grown on the indium phosphide material and the laser emits a first wavelength. Photonic frequency comb generator according to one of Claims 1 until 5 , wherein the light source grown on the indium phosphide material is a semiconductor laser amplifier (SOA) configured to amplify the first wavelength emitted from a laser oscillator cavity on the second die. Photonic frequency comb generator claim 6 , wherein the optical wavelength generator is a micro ring resonator connected to the laser. Photonic frequency comb generator claim 7 , wherein the optical wavelength generator is a micro ring resonator connected to the laser oscillator cavity. Photonic frequency comb generator claim 8 or 9 , wherein the silicon photonics substrate comprises: filters and modulators connected to the micro ring resonator; wherein the micro ring resonator is configured to convert the first wavelength into a plurality of second wavelengths; and wherein one of the filters selects one of the plurality of second wavelengths and transmits that wavelength to one of the modulators in a one-to-one relationship. Photonic frequency comb generator claim 10 , wherein the silicon photonics substrate comprises multiple channels of filters and modulators connected to the micro ring resonator. Photonic frequency comb generator according to one of Claims 8 until 11 , further comprising a plurality of micro ring modulators connected to the micro ring resonator via a waveguide bus, the micro ring resonator being configured to convert the first wavelength into a plurality of second wavelengths, the plurality of second wavelengths from the micro ring resonator into the waveguide bus and wherein one of the plurality of micro ring modulators selects one of the plurality of second wavelengths from the waveguide bus and transmits into the micro ring modulators in a one-to-one relationship. Photonic frequency comb generator claim 10 , 11 or 12 , wherein the conversion of the first wavelength into the plurality of second wavelengths is achieved by adjusting a geometric size of the micro ring and a spacing between the micro ring and the waveguide bus. Photonic frequency comb generator according to one of Claims 8 until 13 , wherein the micro ring resonator comprises hybrid materials. Photonic frequency comb generator Claim 14 , wherein the hybrid materials include non-silicon materials such as silicon carbide (SiC) or silicon germanium (SiGe). Photonic frequency comb generator claim 15 wherein the SiC material is fabricated using techniques including: 1) growth of SiC on a silicon photonic substrate through an interlayer or PVD deposition; 2) flip-chip a SiC die directly onto the silicon photonic substrate; 3) flip-chip the SiC die directly onto the silicon photonic substrate; 4) attach the SiC die through a polymer glass interposer with the SiC die and the silicon photonic substrate juxtaposed; and 5) attaching the SiC die to the silicon photonic substrate by a fiber connected to the SiC die and the silicon photonic substrate by waveguide tapers. Multi-chip module with the photonic frequency comb generator according to one of the preceding claims. Multi-chip module after Claim 16 , further comprising a third die connected to the second die, the third die being an electronic die containing circuitry for electronically manipulating signals, including equalization, encoding, switching and logic operations. Multi-chip module with N photonic frequency comb generators according to one of Claims 1 until 15 , wherein each of the N photonic frequency comb generators comprises a first die and second die pair. Multi-chip module after Claim 18 , further comprising an electronic die connected to the N photonic frequency comb generators respectively by a multi-lane waveguide, the electronic die including circuitry for electronically manipulating signals, including equalization, encoding, switching and logic operations. M-channel WDM module comprising the photonic frequency comb generators according to claim 10 , 11 or 12 , where a number of filters and a number of modulators are both M × 4, where M is a positive integer 1, 2, ... M and M × 4 equals 4, 8, ... M × 4. M-channel CWDM module incorporating the photonic frequency comb generators as per claim 10 , 11 or 12 , where a number of filters and a number of modulators are both M' × 4, where M' is a positive integer 1, 2, ... M' × 4.

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