Photonic chip capable of emitting at least one output emission and optical components using such chips - Patents.com

Abstract

The invention relates to an integrated photonic chip (PIC) for generating at least one combined emission light, the integrated photonic chip (PIC) comprising at least two active combining devices (ACD1, ACD2) optically associated with a bank of lasers (LB) having different wavelengths, the bank being composed of at least two lasers (L1, L2) emitting a first emission light (l1, l2) and a second emission light (l'1, l'2) and configured on at least one optical output (OO) to combine the emission light received at its optical input to generate a combined emission light (l1+l'1, l2+l'2; l1+l2, l'1+l'2). The invention also relates to an optical component comprising such a photonic chip.

Description

[Technical field]

[0001] The present invention relates to a photonic chip that has very particular application in the field of communications using wavelength division multiplexing, and also to an optical component that uses such a chip. [Background technology]

[0002] The increasing need for communication between computing and storage resources in data centers requires the implementation of communication channels used in wavelength division multiplexing (WDM) to handle high bit rates, which can be as high as 400 Gbit / s or even 800 Gbit / s.

[0003] Part of the solution that makes it possible to address this need is to implement high-power WDM sources. As described in the article "WDM Source Based on High-Power, Efficient 1280-nm DFB Lasers for Terabit Interconnect Technologies" by B. Buckley, IEEE PHOTONICS TECHNOLOGY LETTERS, VOL. 30, NO. 22, NOVEMBER 15, 2018, such sources comprise a bank of distributed feedback lasers with Bragg gratings distributed along the laser cavity. The lasers emit light at stepped wavelengths, typically spaced by 100 GHz.

[0004] Each laser is formed of an optical cavity defined between two facets, one of which is substantially transparent and covered with an anti-reflective coating, the other facet being essentially reflective. Light emitted by the laser at the side of the substantially transparent facet is propagated to an input port of a passive optical mixer. This mixer generates a plurality of emitted lights at its output ports, each combining the emitted lights fed to the input ports. The generated output lights at these output ports are thuslight is multi-wavelength (in a spectral comb, each line of the comb is the emission light They are then coupled to an optical fiber via a fiber grating.

[0005] The manufacture of such lasers is delicate, since the reflective facets of the optical cavity must be formed with high precision. Indeed, it is necessary to position the reflective facets very precisely, to within 50 nm, or better within 20 nm, with respect to the feedback Bragg grating of the laser, which cannot be done systematically with commonly used laser cleaving techniques. The efficiency of this manufacturing method is therefore relatively low, on the order of 50%, resulting in the formation of malfunctioning lasers. This low efficiency is all the more problematic, since it applies to each laser of a bank of lasers, so that the manufacturing efficiency of this bank, if it contains N lasers, corresponds to the manufacturing efficiency of one laser to the power N, which can be particularly low for high values ​​of N (typically 8 or more).

[0006] It is also known that the wavelength of emission emitted by a distributed feedback laser having such a reflective facet is poorly controlled due to inaccurate positioning of the reflective facet. light This results in variability in the spacing that exists between the spectral lines, but it is generally desired that this spacing be constant, for example 100 GHz.

[0007] Finally, significant losses (especially insertion losses) in the passive optical mixers used to form the output emissions affect the amount of power available in the optical fiber to which the mixers are coupled. light It is proposed to create lasers with a power content of several hundred milliwatts each, such that the laser with a power content of 10 mW is the input / output port of the optical mixer. These losses tend to increase with the number of input / output ports of the optical mixer, which becomes a problem when the number of lasers in the bank is large. In such mixers, the input emission lightIn order to utilize the full amount of power in the bank, the number of input and output ports would necessarily be the same. Therefore, the solution proposed in the above mentioned document requires the number of optical fibers to be the same as the number of lasers in the bank, which may be a limitation in certain applications.

[0008] Object of the invention The aim of the present invention is to propose a solution to at least some of these problems. Summary of the Invention

[0009] To this end, the present invention proposes an integrated photonic chip for generating at least one combined emission light, the integrated photonic chip comprising: - a bank of at least two lasers having different wavelengths, each laser comprising an optical cavity defined by two ends and emitting a first and a second emission of light respectively from the two ends, at least two active combining devices optically associated with the bank of lasers, each active combining device having at least a first optical input and a second optical input for receiving a portion of the first emitted light and the second emitted light, and configured to combine the emitted light received at the optical inputs of each active combining device at at least one optical output to generate a combined emitted light, the active combining devices further comprising control and measurement elements for controlling the combined emitted light generated at the optical outputs, the control and measurement elements comprising at least one pilot controllable phase shifter and a photodetector; a waveguide grating for directly propagating the first emitted light and the second emitted light between the bank of lasers and the active coupling device.

[0010] According to other advantageous, non-limiting characteristics of the present invention, taken alone or according to any technically feasible combination, the following: - the two lasers are phase-shifted lasers, the ends of which are separated by a feedback grating; the optical cavity of each phase-shift laser is provided with a grating that induces a quarter-wave shift in the cavity; - a laser of the bank of lasers is assembled with a first portion at least partially comprising a waveguide grating, the integrated photonic chip comprises at least one emission zone of at least one output emission light, the waveguide grating also propagates the emission light coupled between the active coupling device of the chip and the at least one emission zone, Each active coupling device is associated with a phase-shifting laser of the bank of lasers, and a first emission of the phase-shifting laser light and the second release light are guided toward the first and second optical inputs of the active coupling devices, respectively, and each active coupling device has a first emission light and the second release light A control element and a measurement element can be used to coherently combine The active combining device performs coherent combining; a combiner having two inputs respectively coupled to a first optical input and a second optical input, and two optical outputs, a first of the outputs being coupled to the optical output, the control element includes at least one pilot-controllable phase shifter arranged optically upstream of at least one of the inputs of the combiner; the measurement element includes a photodetector disposed optically downstream of the second output of the combiner; Each active coupling device is associated with two phase-shifted lasers of the bank of lasers and controls the emission of one of the two phase-shifted lasers. light is guided towards the first optical input, and the emission of the other of the two phase shift lasers light is guided towards the second optical input, and using the control and measurement elements, each active combining device measures the emission from the two lasers. lightIt is possible to spectrally combine The active combining device performs spectral combining, a first combiner and a second combiner, the first combiner having two inputs respectively coupled to the first and second optical inputs, the second combiner having two outputs, a first of the two outputs being coupled to the optical output, the two combiners being optically coupled to each other by two arms; A delay line disposed in one of the two arms; the control element includes at least one pilot-controllable phase shifter arranged optically upstream of the second combiner; the measurement element includes a photodetector disposed optically downstream of the second output of the second combiner; the active coupling device of the first photonic block is arranged on a first side of the bank of lasers and the active coupling device of the second photonic block is arranged on a second side of the bank of lasers opposite the first side, the bank of lasers comprises 2^n phase shift lasers associated with at least 2^n active coupling devices forming a first coupling stage, n being an integer greater than 1; the integrated photonic chip comprises at least a second coupling stage arranged downstream of the first coupling stage, the second coupling stage being formed from at least one secondary coupling device; the number of output emissions is less than or equal to the number of phase-shift lasers; the at least one secondary combining device is selected from the list formed by an active coherent combining device, an active spectrum combining device, a passive power divider; -Waveguide grating is the output emitter light associated with at least one coupler, e.g., an edge coupler, disposed in the emission zone of Phase-shifted lasers have graded emission wavelengths.

[0011] According to another aspect, the object of the present invention proposes an optical component comprising an integrated photonic chip as disclosed above and an integrated control circuit electrically connected to the control element and the measurement element of the active coupling device, the integrated control circuit being configured to control the output emission light generated on the optical output of the active coupling device. [Brief description of the drawings]

[0012] Other features and advantages of the present invention will become apparent from the following detailed description of the invention which refers to the accompanying drawings. [Figure 1] FIG. 1 is a block diagram of a first embodiment. [Diagram 2] FIG. 2 is a block diagram of the active coupling device of FIG. [Diagram 3] 1 shows a first example of an integrated photonic chip and optical component according to a first embodiment. [Figure 4] FIG. 11 is a block diagram of a second embodiment. [Figure 5a] FIG. 5 is a block diagram of the active coupling device of FIG. 4. [Figure 5b] FIG. 5 is a block diagram of the active coupling device of FIG. 4. [Figure 6] 2 shows a second example of an integrated photonic chip according to the second embodiment. [Figure 7] 13 shows a third example of an integrated photonic chip that hybridizes the first and second embodiments. [Figure 8] 13 shows a fourth example of an integrated photonic chip that is a hybrid of the first and second embodiments. [Figure 9] 13 shows a fifth example of an integrated photonic chip that is a hybrid of the first and second embodiments. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] The various embodiments and examples that are the subject of the following description use a bank of phase-shifted lasers, in which the lasers generally have different wavelengths, for example stepped wavelengths, uniformly distributed in a determined frequency band. In a communication application using wavelength division multiplexing (WDM) as presented in the introduction of this application, for example, in the various embodiments and examples of this specification it is possible to provide a bank made of 8 or 16 phase-shifted lasers, whose emitted light has frequencies separated from each other by 50 GHz, 100 GHz, 200 GHz or 400 GHz.

[0014] The lasers constituting the laser bank are advantageously so-called "phase-shifted" lasers. They are distributed feedback lasers, i.e. lasers that use a Bragg grating to select the wavelength of the emitted emission. This feedback grating is distributed along an optical cavity, which has two ends defined by the extent of the grating. Thus, according to the invention, each phase-shifted laser emits a first emission and a second emission respectively exiting from the two ends of the optical cavity. The optical cavity of each laser comprises a grating that induces a quarter-wave shift, inserted entirely in the center of the cavity, to ensure that this laser only emits over a single wavelength.

[0015] The integrated photonic chip is obtained by assembling the lasers of the laser bank with a first part of the chip, which has been previously treated to form therein at least the waveguide grating of the chip. This assembly can be carried out, for example, by molecular bonding. Such a method is described in particular in the document T. Thiessen et al. "Back-Side-on-BOX Heterogeneous Integrated III-V-on-Silicon O-Band Distributed Feedback Lasers" in Journal of Lightwave Technology, vol. 38, no. 11, pp. 3000-3006, 2020. This method allows forming the lasers of the bank and their emission without the need to first form facets by cleaving the material forming the optical cavity. light to the waveguide grating of the chip.

[0016] Phase-shifted lasers have the advantage of providing emission with a very well controlled wavelength. Their manufacture is relatively easy, especially when implementing the assembly techniques mentioned above, and, as mentioned in the introduction to this application, they do not suffer from the efficiency limitations of distributed feedback lasers, one of whose facets is provided with a reflective coating. However, such laser configurations have the disadvantage of producing two emissions, i.e. one at each end of the optical cavity. light and these emissions light The optical power of each of the three lasers is reduced (single emission generated by a distributed feedback laser with a reflective facet). light (less than half the optical power of the

[0017] The various embodiments presented improve this situation by proposing a different architecture of an integrated photonic chip for the purpose of combining together the emissions coming from a bank of lasers. Thus, an integrated photonic chip with N phase-shifted lasers (generating 2N emissions) can be coupled to M optical fibers, where M is less than or equal to N. Each optical fiber receives the combined emissions from the chips with an improved amount of power.

[0018] It should be noted that the use of a passive mixer associated with a photonic chip comprising a bank of N lasers of power P, with 2N emissions of power P / 2, results in providing at the output of the mixer 2N combined emissions, each with a power of P / 4N (2N * (A 2N mixer induces losses on the order of 1 / 2N.) Such power levels are not sufficient, especially when this number N is relatively large.

[0019] In a chip with multiple lasers, for optical routing reasons, it is advantageous to arrange the phase-shifted lasers on the chip so that their respective ends are aligned to define a first side of the laser bank where the first emission is emitted, and a second side of the laser bank where the second emission is emitted. Various embodiments repeat this advantageous arrangement, but this is in no way a limitation of the invention. In general, the lasers forming the laser bank may be arranged in any suitable arrangement.

[0020] 1 shows a block diagram of a first embodiment of an integrated photonic chip PIC. The chip PIC comprises a bank of lasers LB, here formed for ease of explanation from two phase-shifted lasers L1, L2. In this embodiment, the two emissions emitted by the lasers L1, L2 are combined into a combined emission of increased power. light are coherently combined with each other to form

[0021] The first phase shift laser L1 emits a first light beam from each of its ends. light l1 and second release light Similarly, the second phase-shifted laser L2 emits the first emission from each of its ends. light l2 and second release light As already mentioned, the emission generated by the first laser L1 and the second laser L2 is light preferably have different wavelengths.

[0022] The integrated photonic chip PIC of the block diagram of Fig. 1 comprises two active coupling devices ACD1, ACD2, which are shown in detail in Fig. 2. Each active coupling device ACD1, ACD2 is associated with a laser L1, L2 and performs a coherent combination of a first emission l1, l2 with a second emission l'1, l'2. Thus, two combined emissions l1+l'1, l2+l'2 are generated by the lasers L1, L2, which are guided into emission zones Z1, Z2 of the chip, which may be formed, for example, by edge couplers.

[0023] The integrated photonic chip PIC also comprises a waveguide grating WG for propagating the first and second emitted light between the bank LB of lasers and the active coupling devices ACD1, ACD2 and for propagating the coupled emitted light between these active coupling devices ACD1, ACD2 and the emission zones of the chips Z1, Z2. Advantageously, the waveguide WG propagates the first and second emitted light directly between the bank LB of lasers and the active coupling devices ACD1, ACD2, i.e. light is not modified (eg, modulated) during this propagation.

[0024] In all embodiments of the invention, the coupling devices ACD1, ACD2 are said to be "active" because they comprise control and measurement elements that allow to control the emissions emerging from the phase shift lasers L1, L2 and in particular to combine them in a fully controlled manner by controlling the phase of these emissions. The control and measurement elements comprise at least one pilot-controllable phase shifter and a photodetector. Due to the active nature of these devices, the coupling can be realized with reduced losses of the order of 0.5 dB. These control and measurement elements, in particular the pilot-controllable phase shifter and the photodetector, are electrically connected to electrical contact pads of the integrated photonic chip PIC. An integrated control circuit CTRL_IC can be associated to the integrated photonic chip PIC and is electrically connected to the control and measurement elements of the active coupling devices ACD1, ACD2. The integrated control circuit CTRL_IC calibrates the control elements (e.g. pilot-controllable phase shifters) and adjusts the combined emissions generated at the optical outputs of the active coupling devices ACD1, ACD2 to the phase of these emissions. light is adapted to regulate the optical output of the integrated control circuit so that the optical output of the integrated control circuit is adapted to comply with a selected set point, in particular so that all optical power is transmitted at one of these optical outputs. For this purpose, the integrated control circuit receives measurements provided by the photodetector, which measurements enable the implementation of the optical control.

[0025] Fig. 2 shows a first active combining device ACD1 of the first embodiment, it being understood that the second active combining device ACD2 has an identical architecture. The first active combining device ACD1 has a first optical input Ol1 and a second optical input Ol1' for receiving the first emitted light l1 and the second emitted light l'1 from the first laser L1, respectively. The first active combining device ACD1 also has an optical output OO for generating an emitted light l1+l'1, which coherently combines the emitted light received at the optical inputs Ol1, Ol1'. Such a combination is performed, for example, by a combiner CP implemented by a multimode interferometer or a Y-junction waveguide. The combiner CP has two inputs coupled to the first optical input Ol1 and the second optical input Ol1', respectively, and two outputs, of which the first output is coupled to the optical output OO of the active combining device ACD1.

[0026] To enable this coherent combining, the first active combining device ACD1 shown in Fig. 2 comprises two pilot-controllable phase shifters PS1, PS1' arranged optically upstream of the input of the combiner CP. These may be thermo-optical phase shifters. light The phase delay propagated to is controllable by an electrical signal PS_ctrl generated by the control device CTRL_IC. In general, the active combining device ACD1 of this first embodiment comprises at least one pilot-controllable phase shifter, which is sufficient to enable coherent combining, but it may require a significant amount of energy to achieve the conditions enabling this combining. For this reason, it is advantageously proposed to equip the active combining device with two pilot-controllable phase shifters.

[0027] The first active combining device ACD1 shown in Fig. 2 also comprises a photodetector PD optically downstream of the second output of the combiner CP, which generates an electrical signal TAP that is supplied to the control device CTRL_IC.

[0028] In operation, the control device CTRL_IC adjusts, using the control signal PS_ctrl, the phase introduced by the phase shifters PS1, PS1' so that a maximum value of the optical power of the signal is combined at the output of the combiner CP propagating towards the optical output OO. To do this, the control device CTRL_IC measures the optical power available on the other channels of the combiner using a measurement signal provided by the photodetector PD and tries to minimize it. In other words, the control device CTRL_IC adjusts the phase introduced by the phase shifters PS1, PS1' using the combiner CP with the aim of minimizing the measurement signal TAP provided by the photodetector PD. light l1 and second release light First release before binding l'1 light l1 and second release light Regulation is performed by adjusting the phase of l'1.

[0029] 3 shows a first example of an integrated photonic chip PIC and an optical component according to this first embodiment of the invention. Here we also find a control device CTRL_IC electrically connected to the integrated photonic chip PIC by means of a bus BUS which groups together all the control and measurement signals PS_ctrl, TAP intended to control the active coupling devices ACD1 to ACDN of the chip PIC.

[0030] In this example, the integrated photonic chip PIC comprises N (e.g. 8, 16 or more) phase-shifted lasers. Each phase-shifted laser L1 to LN is associated with an active combining device ACD1 to ACDN, which coherently combines two emissions provided by each of the ends of an optical cavity forming a laser.

[0031] The coupled emission light is, in this example, guided towards emission zones Z1 to Zn, where it is coupled into a grating of N optical fibers F1 to FN. These emission zones Z1 to ZN are lightTo facilitate the injection of the , coupling means, such as an edge coupler or a surface coupling grating, may be provided. Of course, other optical elements may be coupled to the coupled emission to perform any desired transformation into the coupled emission. light It may be provided on the propagation path, within the integrated photonic chip, or outside the integrated photonic chip.

[0032] FIG. 4 shows a block diagram of a second embodiment of an integrated photonic chip PIC according to the invention.

[0033] The chip PIC in the block diagram of Fig. 4 comprises, for ease of description, a bank of lasers LB formed of two phase-shifted lasers L1, L2. The bank of lasers LB has all the characteristics of the bank shown in the first part of the description. The two phase-shifted lasers L1, L2 emit, inter alia, a first light emission l1, l'1 and a second light emission l2, l'2 having different wavelengths. In this embodiment, the emissions emitted by the two phase-shifted lasers L1, L2 are spectrally combined to form a combined multispectral radiation of increased power.

[0034] Thus, as can be seen very clearly in Fig. 4, the first emitted light l1 emitted by the first phase-shifted laser L1 and the first emitted light l2 emitted by the second phase-shifted laser L2 are both guided onto the optical inputs 0l1, 0l2 of the first active combining device ACD1, thus resulting in a spectral combination of the two first emitted lights l1, l2 to form a first combined emitted light l1+l2 in this embodiment. Similarly, the second emitted light l'1 emitted by the first phase-shifted laser L1 and the second emitted light l'2 emitted by the second phase-shifted laser L2 are both guided onto the optical inputs Ol1, Ol2 of the second active combining device ACD2 to form a combined emitted light l'1+l'2. The active combining devices ACD1, ACD2 thus constitute a multiplexer or interleaver.

[0035] As in the first embodiment, the integrated photonic chip PIC of this second embodiment comprises a waveguide grating WG for propagating the first and second emitted light between the bank LB of lasers and the active coupling devices ACD1, ACD2, and for propagating the coupled emitted light between the active coupling devices ACD1, ACD2 and the emission zones Z1, Z2 of the chip. Of course, as in the first embodiment, other optical elements can be added to the coupled emitted light in order to perform any desired conversion to the coupled emitted light. light It may be provided on the propagation path, within the integrated photonic chip PIC, or outside the integrated photonic chip.

[0036] The integrated photonic chip PIC can also be associated with a control integrated circuit CTRL_IC, electrically connected to the control elements of the active coupling devices ACD1, ACD2 and similar to the one presented in the first embodiment. The integrated control circuit CTRL_IC is thus configured to control the operation of the active coupling devices ACD1, ACD2 in order for them to perform the desired spectral coupling. For this purpose, the integrated control circuit CTRL_IC receives measurement signals TAP from the active coupling devices ACD1, ACD2 and generates control signals PS_ctrl directed to these devices.

[0037] Fig. 5a is a block diagram of the first active combining device ACD of Fig. 4, it being understood that the second active combining device ACD2 has an identical architecture. In general, this active combining device ACD of the second embodiment can be a Mach-Zehnder interferometer. More precisely, this first active combining device ACD1 has a first optical input Ol1 and a second optical input Ol2 for receiving the first emitted light l1, l2 of the two lasers L1, L2, respectively. It also has an optical output OO at which the emitted light received at the optical inputs Ol1, Ol2 are spectrally combined to generate a combined emitted light l1+l2. Such a combination is for example performed by two combiners CP1, CP2 formed by a multimode interferometer or a Y-junction waveguide. The first combiner CP1 has two inputs respectively coupled to the first and second optical inputs Ol1 and Ol2, and two outputs respectively coupled to the two inputs of a second combiner CP2, which itself has two outputs, the first of which is coupled to the optical output OO of the active combining device ACD1.

[0038] To allow the spectral combination without significant optical losses, the first active combining device ACD1 shown in Fig. 5a comprises two pilot-controllable phase shifters PS1, PS2 optically arranged between the two combiners CP1, CP2. As in the first embodiment, the device can be provided with a single pilot-controllable phase shifter. The phase shift propagated by the phase shifters PS1, PS2 to the emitted light is controllable by a control electrical signal PS_ctrl generated by the control device CTRL_IC. One of the two arms connecting the combiners CP1, CP2 comprises an additional waveguide section DL forming a delay line. As is known, the length of the additional waveguide section DL determines the transmission function of the active combining device, i.e. the spectral deviation that the first emitted light must have at the input of the device to allow it to be combined at the output. A detailed description of this device is given, inter alia, in the publication "Wavelength Filters for Fibre Optics", edited by H. Venghaus, Springer Series in Optical Sciences, Vol. 123, Springer, pp. 381-432.

[0039] The first active combining device ACD1 shown in Fig. 5a also comprises a photodetector PD optically downstream of the second output of the second combiner CP2, which photodetector generates an electrical measurement signal TAP that is supplied to the control device CTRL_IC.

[0040] In operation, the control device CTRL_IC uses the control signal PS_ctrl to adjust the phase introduced by the phase shifters PS1, PS2 to produce the output light is coupled at the output of the coupler propagating towards the optical output OO. To do this, the control device CTRL_IC measures the optical power available on the other channels of the coupler using a measurement signal provided by the photodetector PD and thus tries to minimize the optical power.

[0041] Figure 5b shows an alternative block diagram to that shown in Figure 5a, where the first active coupling device ACD is in this case implemented by a resonant ring. The resonant ring RR is arranged between two arms arranged between the optical input and the optical output of the active coupling device ACD. A phase shifter PS is arranged on the resonant ring RR. One of the outputs is also equipped with a photodetector PD.

[0042] 6 shows a second example of an integrated photonic chip PIC according to a second embodiment of the invention. For ease of reading the figure, the illustration of a control device CTRL_IC is omitted, but such a device may be provided in electrical connection to the integrated photonic chip PIC as presented in example 1 of FIG. 3 to form a functional optical component.

[0043] The bank of lasers LB is placed in the centre of the integrated photonic chip PIC, between a first photonic block B1 and a second photonic block B2. These two blocks B1, B2 have an identical construction in this example, so only the architecture of the first block B1 is shown in detail. Of course, it is not necessary that these two blocks are completely identical. Each block comprises a first photonic block LB and a second photonic block LB. The first photonic block LB is arranged in the centre of the integrated photonic chip PIC, between a first photonic block LB and a second photonic block LB. These two blocks B1, B2 have an identical construction in this example, so that only the architecture of the first block B1 is shown in detail. Of course, it is not necessary that these two blocks are completely identical. Each block comprises a first photonic block LB and a second photonic block LB. The second photonic block LB is arranged in the centre of the integrated photonic chip PIC, between a first photonic block LB and a second photonic block LB. light between them.

[0044] The phase-shifted lasers L1 to L8 of the bank of lasers LB have stepped wavelengths, and the two lasers with successive indices Li, Li+1 are separated by a spectral separation band of 100 GHz in this example. Of course, the value of this spectral separation band depending on the field of application, the total emission light The available spectral bandwidth to accommodate and the number of phase-shifted lasers in the bank of lasers LB can be freely chosen.

[0045] Continuing with the description of FIG. 6 and the first photonic block B1, the latter comprises four active combining devices ACD1-ACD4, each associated with two first emissions of two different phase-shifted lasers. Four combined emissions are thus formed, each of which therefore has two spectral lines corresponding to the emission wavelengths of each of the original phase-shifted lasers. These four active combining devices ACD1-ACD4 are similar and form the first combining stage of the first block.

[0046] In the example of Fig. 6, a second coupling stage is provided, consisting of two active secondary coupling devices ACDa-ACDb. The combined emissions are guided in pairs to the inputs of these two devices, which then combine these emissions to provide two combined emissions. light are sequentially combined in pairs. light has four spectral lines corresponding to the emission wavelengths of each of the original phase-shifted lasers. More precisely, the first secondary device ACDa supplies an emission light l1+l2+l3+l4 having the spectral components of the first four lasers L1-L4 to which it is optically coupled. Similarly, the second secondary device ACDb supplies an emission light l5+l6+l7+l8 having the spectral components of the other four lasers L5-L8 of the bank to which it is optically coupled. It should be noted that to facilitate this two-stage combining, the phase-shifted lasers L1-LN are associated with the active combining devices of the first stage in an interleaved manner, and the two phase-shifted lasers associated with the same active combining device are shifted by 200 GHz. In this way, it is ensured that the spectral combining of the second stage of the first block B1 is performed for two emission lights having spectral lines separated from each other by 100 GHz.

[0047] Finally, the first photonic block of the example of FIG. 6 comprises, in a third stage, a power divider S constituting a device for passively combining the combined emissions leaving the second stage. This passive combining device constitutes the third combining stage. Such a passive device allows to easily combine (without active control means) the two combined emissions leaving the second stage of the first photonic block B1, albeit at the expense of a relatively large optical loss of the order of 3.5 dB. This first block finally combines, in two emission zones Z1, Z2, the emissions leaving the eight phase-shifted lasers L1 to L8 of the bank of lasers LB. light Two output emissions that spectrally combine light Each output emission resulting from multiple couplings light It will be understood that the second photonic block B2 of the integrated photonic chip can have an architecture identical to that of the first photonic block B1, as already mentioned, so that finally the integrated photonic chip PIC generates four output emissions, which can be coupled into a grid of four optical fibers, not shown.

[0048] More generally, it is understood that each photonic block B1, B2 can comprise several coupling stages, each stage being composed of at least one active or passive coupling device. Coupling devices present in stages of order 2 or higher are called secondary coupling devices in this application. It is therefore possible to make a particularly effective photonic chip (by giving preference to active coupling devices) and limit the number of output ports of the chip, i.e. each output emission has a relatively high optical power, independent of the number of phase-shifted lasers for the output emission. It is therefore possible to propose an integrated photonic chip with N phase-shifted lasers, each generating two output light beams, and to effectively couple this chip PIC to M optical fibers, where M is less than N (in the case of several coupling stages) or equal to N (in the case of a chip PIC with a single coupling stage).

[0049] 7 shows a third example of an integrated photonic chip PIC, which is a hybrid of the first and second embodiments. To simplify the drawing, the control and measurement elements and the associated signals for all active coupling devices are not shown, although they are of course present.

[0050] In this example, eight phase-shifted lasers L1 to L8 are associated with a first coupling stage formed from eight active coupling devices ACD1 to ACD8 according to the first embodiment. Each active coupling device thus has two emission radiators emerging from its associated phase-shifted laser. light , and perform coherent combining of the signals.

[0051] This first stage is optically connected by waveguide gratings to three other successive stages of secondary active combining devices which perform the spectral combining according to the second embodiment, i.e. the second stage is composed of four secondary active combining devices ACD1' to ACD4', the third stage is composed of two secondary active combining devices ACDa, ACDb and the fourth stage is composed of a single secondary active combining device ACDc.

[0052] The integrated photonic chip of this third example uses only active coupling devices, which tends to reduce optical losses (at the expense of a slightly higher degree of complexity in the controls). All the optical power generated by the bank of lasers, except for losses, is transmitted to the single output emission of the chip PIC in a single emission zone Z1. light This output will be available at light transmits the spectral components of the eight phase-shifted lasers LS1 to LS8 of the bank LB.

[0053] Figure 8 shows a fourth example of an integrated photonic chip PIC, which hybridizes the first and second embodiments. It is a variant of the photonic chip of the third example of figure 7, in which the secondary active coupling device of the fourth stage is replaced by a passive coupling device S, which may be a power divider. The optical power generated by the bank of lasers is split into two output emitters of the chip PIC, in two emission zones Z1, Z2. light will be available in.

[0054] Figure 9 shows a fifth example of an integrated photonic chip PIC, which is a hybrid of the first and second embodiments. It is a modification of the photonic chip PIC of the third and fourth examples of figures 7 and 8, in which the secondary active coupling devices ACDa, ACDb, ACDc of the fourth and third stages are replaced by passive coupling devices S, such as power dividers. The optical power generated by the bank of lasers is distributed to the four output emitters of the chip PIC, in four emission zones Z1 to Z4. light It should be noted that this architecture requires the intersection of two waveguides in the zone indicated by an X in this figure, which introduces a loss of the order of 0.5 dB.

[0055] Naturally, the invention is not limited to the described embodiments and variants can be added thereto without departing from the scope of the invention as defined by the claims.

[0056] Although the use of a bank of distributed feedback phase-shifted lasers has been shown to form a preferred type of laser in many applications due to the advantages described in the previous paragraphs of this application, the invention is in no way limited to this type of laser, and the invention applies more generally to any bank formed by lasers, each laser comprising an optical cavity defined by two ends and emitting a first and a second emission respectively from the two ends.

[0057] To reduce the number of contact pads on the integrated photonic chip PIC and to facilitate the routing of the measurement signals, all conductive lines carrying the measurement signals TAP of the active coupling devices ACD1 to ACDN can be connected together. A single electrical measurement signal is thus available at a single pad of the chip PIC, which measurement signal represents the optical power available at all the photodetectors of the active coupling devices of the chip PIC. A single line of the bus BUS carries this measurement signal to transmit it to a single input of the control device CTRL_IC. The latter implements a program for calibrating and / or controlling the control signals PS_ctrl of the phase shifters of each active coupling device ACD1 to ACDN. The purpose of this calibration and / or control program is to minimize the value carried by a single measurement signal, for example during the start-up phase of the chip.

[0058] As an alternative to such a program, it may be proposed to equip the integrated photonic chip with a multi-way switch, controllable by the control device CTRL_IC and enabling the photodetector of a selected active coupling device to be connected to a single contact pad of the integrated photonic chip.

[0059] Additionally, in various embodiments and examples, coupled release light Although it has been described and illustrated that the combined emitted light is directly guided towards the emission zone of the integrated photonic chip, this feature is not essential, and it is therefore possible to provide that other devices that block the propagation of these combined emitted light, for example a modulation grating, are inserted before they are propagated by the waveguide grating towards the emission zone of the chip.

[0060] More generally, the integrated photonic chip does not need to have an emission zone. The integrated photonic chip can, for example, constitute an integrated communication device between a computing device and a memory device, allowing data to be communicated between these two devices without the need to couple the chip to an optical fiber or to propagate the output emission by free propagation. In this case, the coupled emission light In addition to the above-mentioned means for preparing the release light In general, therefore, it is an object of the invention to generate at least one combined emission from a bank of lasers, which may be of the DFB, DBR (Distributed Reflector Laser) or DML (Directly Modulated Laser) type.

Claims

1. an integrated photonic chip (PIC) for generating at least one combined emission light, comprising: a bank (LB) composed of at least two lasers (L1, L2) with different wavelengths, each laser comprising an optical cavity defined by two ends and emitting a first light emission (l1, l2) and a second light emission (l'1, l'2) respectively emerging from said two ends, at least two active coupling devices (ACD1, ACD2) optically associated with said bank (LB) of lasers, each active coupling device (ACD1, ACD2) having at least a first optical input (Ol1, Ol2) and a second optical input (Ol1', Ol2') for receiving a portion of said first emitted light (l1, l2) and said second emitted light (l'1, l'2), and at least one optical output (optical output, OO) of each active combining device (ACD1, ACD2) is configured to combine the emitted light received at the optical inputs (Ol1, Ol1'; Ol1, Ol2) of the active combining devices (ACD1, ACD2) to generate a combined emitted light (l1+l'1, l2+l'2; l1+l2, l'l+l'2), at least two active combining devices further comprising control and measurement elements (PD, PS1, PS1'; PS2) for controlling the combining of the emitted light and generating the combined emitted light (l1+l'1, l2+l'2; l1+l2, l'1+l'2) generated at the optical output (OO), said control and measurement elements comprising at least one controllable phase shifter (PS1, PS1', PS2) and a photodetector (PD), an integrated photonic chip (PIC) comprising a waveguide network (WG) for direct propagation of the first and second emitted light between the bank of lasers (LB) and the active coupling devices (ACD1, ACD2).

2. 2. The integrated photonic chip (PIC) of claim 1, wherein the two lasers (L1, L2) are phase-shifted lasers, the ends of which are separated by a feedback grating.

3. 3. An integrated photonic chip (PIC) according to claim 2, wherein the optical cavity of each phase shift laser (L1, L2) is provided with a grating which induces a quarter-wave shift in the cavity.

4. 2. The integrated photonic chip (PIC) of claim 1, wherein the lasers (L1, L2) of the bank of lasers are assembled with a first portion that at least partially comprises the waveguide network (WG).

5. 2. The integrated photonic chip (PIC) of claim 1, comprising at least one emission zone (Z1-Z4) of at least one output emission light, said waveguide network (WG) also propagating said coupled emission light between said active coupling devices (ACD1, ACD2) of said chip and said at least one emission zone (Z1-Z4).

6. 2. The integrated photonic chip (PIC) of claim 1, wherein each active combining device (ACD1, ACD2) is associated with a phase shift laser (L1, L2) of the bank of lasers (LB), and the first emitted light (l1, l2) and the second emitted light (l'1, l'2) of the phase shift laser (L1, L2) are guided towards the first optical input (Ol1) and the second optical input (Ol2) of the active combining device (ACD1, ACD2), respectively, and the control and measurement elements (PD, PS1, PS1') can be used such that each active combining device (ACD1, ACD2) coherently combines the first emitted light (l1, l2) and the second emitted light (l'1, l'2).

7. said active combining devices (ACD1, ACD2) performing coherent combining; a combiner (CP) having two inputs respectively coupled to said first optical input (O11) and to said second optical input (O12) and two optical outputs, a first of which is coupled to said optical output (OO), said control element comprises at least one pilot-controllable phase shifter (PS1, PS1') arranged optically upstream of at least one of said inputs of said combiner (CP); An integrated photonic chip (PIC) according to claim 6, wherein said measurement element comprises a photodetector (PD) arranged optically downstream of the second output of said combiner (CP).

8. 2. The integrated photonic chip (PIC) of claim 1, wherein each active combining device (ACD1, ACD2) is associated with two phase shift lasers (L1, L2) of the bank of lasers (LB), the emission light (l1, l'1, l2, l'2) of one of the two phase shift lasers (L1, L2) being guided towards the first optical input (Ol1) and the emission light (l1, l'1, l2, l'2) of the other of the two phase shift lasers (L1, L2) being guided towards the second optical input (Ol2), and the control and measurement elements (LS1, LS2, PD) can be used such that each active combining device (ACD1, ACD2) spectrally combines the emission light emerging from the two lasers.

9. said active combining devices (ACD1, ACD2) performing spectral combining; a first combiner (CP1) and a second combiner (CP2), the first combiner having two inputs respectively coupled to the first optical input (Ol1) and to the second optical input (Ol2), the second combiner having two outputs, a first of which is coupled to the optical output (OO), the two combiners being optically coupled to each other by two arms, a delay line (DL) arranged in one of the two arms, said control element comprises at least one pilot-controllable phase shifter (PS1, PS2) arranged optically upstream of said second combiner (CP2); The integrated photonic chip (PIC) of claim 8, wherein the measurement element comprises a photodetector (PD) arranged optically downstream of the second output of the second combiner (CP2).

10. 10. The integrated photonic chip (PIC) of claim 9, wherein the active coupling device (ACD1) of a first photonic block (B1) is arranged on a first side of the bank of lasers and the active coupling device (ACD2) of a second photonic block (B2) is arranged on a second side of the bank of lasers opposite the first side.

11. 2. The integrated photonic chip (PIC) of claim 1, wherein the bank of lasers comprises 2^n phase shift lasers (L1-LN) associated with at least 2^n active coupling devices (ACD1-ACDN) forming a first coupling stage, n being an integer greater than 1, and the integrated photonic chip (PIC) comprises at least a second coupling stage arranged downstream of the first coupling stage, the second coupling stage being formed from at least one secondary coupling device.

12. The integrated photonic chip (PIC) of claim 11, wherein the number of output emissions is equal to or less than the number of said phase shift lasers (L1-LN).

13. The integrated photonic chip (PIC) of claim 11, wherein said at least one secondary combining device is selected from the list formed by an active coherent combining device, an active spectrum combining device, a passive power divider (S).

14. The integrated photonic chip (PIC) of claim 11, wherein the waveguide network (WG) is associated with at least one coupler, e.g. an edge coupler.

15. The integrated photonic chip (PIC) of claim 11, wherein the phase-shifted lasers (L1, L2) have graded emission wavelengths.

16. An optical component comprising an integrated photonic chip (PIC) according to any one of claims 1 to 15 and a control integrated circuit (CTRL_IC) electrically connected to the control and measurement elements (PS1, PS1', PS2, PD) of the active coupling devices (ACD1, ACD2), wherein the integrated control circuit (CTRL_IC) is configured to control the output emission light generated on the optical output (OO) of the active coupling devices (ACD1, ACD2).

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