EP4681299A1 - Integrated photonic transmission circuit capable of operating over an extended temperature range - Google Patents

Abstract

The invention relates to an integrated photonic transmission circuit (1) including a laser source (LS) for producing light radiation and comprising a grating defining a transmission wavelength (L_bragg) and a first amplifying medium (A1) having a first photoluminescence wavelength (L₁) and a semiconductor optical amplifier (SOA) comprising a second amplifying medium (A2) having a second photoluminescence wavelength (L_gain). According to the invention, the laser source (LS) and the optical amplifier (SOA) are configured such that, at a first temperature (T0), the transmission wavelength (L_bragg) is closer to the first photoluminescence wavelength (L₁) than to the second (L_gain) and, at a second temperature (T1), the transmission wavelength (L_bragg) is closer to the second photoluminescence wavelength (L_gain) than to the first (L₁).

Description

Integrated photonic emission circuit capable of operating over a wide temperature range FIELD OF THE INVENTION

The present invention relates to an integrated photonic emission circuit. Such a circuit can find an application in the field of telecommunications to produce a transmission component or in the field of sensors, for example to produce a LIDAR component.

TECHNOLOGICAL BACKGROUND OF THE INVENTION

Photonic integrated circuits are integrated circuits capable of generating, detecting or manipulating light radiation. These circuits, like electronic integrated circuits, can incorporate on a single substrate (for example a silicon-based substrate) multiple functional blocks, such as laser sources, switches, modulators, amplifiers, power distributors, these blocks being connected to each other by waveguides.

An integrated photonic emission circuit is provided with a source of light radiation, typically a laser source. In a manner well known per se (see for example EP2811593), such a source comprises an optical amplifying medium formed of a stack of layers of III-V materials constituting at least one hetero junction or so-called “active” region, for example a plurality of quantum wells. This stack can be made from materials chosen from the following non-exhaustive list: InP, AsGa, InGaAlAs, InGaAsP, InAsP. The choice of materials making up this stack defines the photoluminescence wavelength of the amplifying medium. The amplifying medium is characterized by its amplification gain, which is a function of the wavelength. This function has a peak for the so-called “photoluminescence” wavelength, and decreases on either side of this wavelength to define an amplification bandwidth whose width can typically be of the order of 30 nm.

The amplifying medium is arranged, for example in a ribbon, in line with a portion of a waveguide, called a coupling portion, the waveguide being able to be formed for example in silicon. The circulation of a current in this medium makes it possible to pump it electrically in order to establish a hybrid optical mode in the amplifying medium and in the waveguide portion. The laser effect is obtained by means of a feedback structure making it possible to form a resonant cavity. This structure can be produced by a distributed reflector, for example a Bragg grating, arranged at the level of the amplifying medium or in the waveguide. The Bragg grating defines the emission wavelength of the light radiation produced by the laser source. The hybrid optical mode which is formed in the amplifying medium and in the coupling portion of the underlying waveguide tends to propagate in the waveguide.

Document EP3538937 proposes to form such a laser source (as well as the other active elements of the photonic integrated circuit) by "vignetting", i.e. by transferring a block of III-V materials onto the coupling portion of a waveguide using a layer transfer technique. In other approaches, the block of layers of III-V materials forming the amplifying medium is produced by deposition, for example by epitaxial deposition, on the coupling portion of the waveguide. This block of materials is treated, in particular by etching, to form the electrical contacts on either side of the junction in order to form a functional laser diode. When it is sought to produce a plurality of active elements, for example a plurality of laser sources, the block of III-V materials can also be structured to individualize a plurality of diodes arranged at right angles to a plurality of waveguide coupling portions. This approach, all the details and implementation variants of which can be found in the document EP3538937 cited above, is very advantageous in that it simplifies the manufacture of integrated photonic emission circuits. This is particularly the case when these include several active elements having amplifying media made of the same materials, by allowing the collective manufacture of these active elements.

To produce light radiation with satisfactory power, the emission wavelength of the light radiation (defined by the period of the Bragg grating) and the photoluminescence wavelength of the amplifying medium (defined by the nature of the materials defining the stack) are chosen to correspond. At a minimum, we seek to place the emission wavelength of the light radiation in the amplification bandwidth of the amplifying medium.

However, and as recalled in document US2011211603, these wavelengths undergo drifts with the operating temperature of the laser source. Thus, the emission wavelength of the light radiation, referenced L _bragg in the remainder of this description, tends to increase with the temperature, this increase being of the order of 0.1 nm/°C. The gain function and the gain peak of the amplifying medium tend to increase much more significantly with the temperature, of the order of 0.6 nm/°C.

There represents, in a power in decibel (dB)/wavelength in nm reference frame, the evolution of the gain L₁ of the amplifying medium and the emission wavelength L_braggof a laser source, of the state of the art. It thus illustrates the phenomena appearing at three increasing temperatures T0, T1, T2 due to these differentiated drifts. We note first of all that the gain function of the amplifying medium G(T0), G(T1), G(T2), and in particular the amplitude of the gain peak, tends to decrease with the temperature.

At a relatively low operating temperature T0, the emission wavelength L _bragg (T0) is arranged in the gain bandwidth of the amplifying medium, at a wavelength greater than the wavelength L ₁ (T0) of the gain peak. Although at this emission wavelength L _bragg (T0) the gain is not maximum, this situation is not unfavorable, because at a relatively low temperature T0, the gain remains relatively large. The emission power of the emitted radiation can therefore be satisfactory.

At an intermediate operating temperature T1, due to the drifts induced by the temperature rise on the gain function and on the emission wavelength, the emission wavelength L _bragg (T1) is arranged at a wavelength close to the wavelength L ₁ (T1) of the gain peak. This situation is favorable since the amplification provided is maximum or close to its maximum.

At a relatively high operating temperature T2, the emission wavelength L _bragg (T2) is this time arranged in the lower part of the gain bandwidth of the amplifying medium, at a wavelength lower than the wavelength L ₁ (T2) of the gain peak. This situation is not favorable, because it combines on the one hand a gain function weakened by the relatively high operating temperature and on the other hand the emission wavelength L _bragg (T2) is located in a portion far from the peak of this function. The power of the emitted light radiation is therefore particularly low.

It is therefore understood that the laser source is capable of producing light radiation having a satisfactory power, greater than a desired power threshold, in a limited operating temperature range, in the range [T0,T1] in the example of the .

To increase the power of the light radiation produced by the source, it is possible to add to the laser source, integrated in the photonic integrated circuit, a semiconductor optical amplifier (often referred to by the English expression "Semiconductor optical amplifier" or SOA, in the field). An example of such an integrated circuit is notably described in the document US2013107900. This amplifier is arranged end to end (i.e. without an intermediate waveguide) with the laser source and has, just like this laser source, an amplifying medium prepared from the same materials as that of the source. Although the semiconductor optical amplifier can somewhat extend the temperature range ensuring satisfactory operation of the laser source, by increasing the overall gain function applying to the light radiation produced, the photonic integrated circuit remains subject to the same temperature drift effects and therefore has the same limitations as those presented with reference to the .

In document US2003/210723 the laser source and the optical amplifier are monolithically integrated, i.e. they share the same active region.

It therefore remains desirable to extend the operating temperature range of integrated photonic emission circuits.

SUBJECT OF THE INVENTION

An aim of the invention is to propose at least a partial solution to this problem. More particularly, an aim of the invention is to provide an integrated photonic emission circuit having a wider operating temperature range than those of the integrated circuits of the state of the art.

BRIEF DESCRIPTION OF THE INVENTION

In order to achieve this goal, the subject of the invention provides an integrated photonic emission circuit according to claim 1.

• le milieux amplificateurs de la source laser et le milieux amplificateurs de l’amplificateur sont configurés pour que leurs longueurs d’ondes de photoluminescence respectives à la première température sont séparées d’un écart en longueur d’onde inférieure ou égale à leurs dérives en température à la seconde température ;
• le premier milieu amplificateur est choisi de sorte que, sur une gamme de température comprise entre la première température et la seconde température, l’écart existant entre la longueur d’onde d’émission et la première longueur d’onde de photoluminescence soit inférieur à une demi-bande passante du premier milieu amplificateur ;
• le circuit photonique intégré d’émission comprend une pluralité de sources laser présentant un premier milieu amplificateur de composition identique, une pluralité d’amplificateurs optiques à semiconducteur présentant un second milieu amplificateur de composition identique, et une pluralité de guides d’onde respectivement disposés entre les sources laser et les amplificateurs optiques à semiconducteur pour respectivement transmettre les rayonnements lumineux produits par les sources laser aux amplificateurs optiques à semiconducteur ;
• le circuit photonique intégré d’émission comprend une pluralité d’amplificateurs optiques à semiconducteur complémentaire présentant un second milieu amplificateur complémentaire de composition identique et présentant une longueur d’onde de photoluminescence complémentaire inférieure ou égale, à la première température, à la seconde longueur d’onde de photoluminescence ;
• le circuit photonique intégré d’émission comprend, optiquement en aval de la pluralité d’amplificateurs optiques à semiconducteur et de la pluralité d’amplificateurs optiques à semiconducteur complémentaires, une pluralité de commutateurs optiques, chaque commutateur optique étant relié à un amplificateur optique à semiconducteur et à un d’amplificateur optique à semiconducteur complémentaire ;
• le circuit photonique intégré d’émission comprend une pluralité de sources laser et une pluralité d’amplificateurs optiques à semiconducteur, les sources laser et les d’amplificateurs optiques à semiconducteur présentant deux à deux un milieu amplificateur de même composition, et une pluralité de guides d’onde respectivement disposés entre des sources laser et des amplificateurs optiques à semiconducteur présentant des milieux amplificateur de composition différentes ;
• le circuit photonique intégré d’émission comporte en outre un multiplexeur en longueurs d’onde disposé en aval de la pluralité d’amplificateurs optiques à semiconducteur et optiquement relié aux amplificateurs optiques à semiconducteur pour produire un rayonnement lumineux multispectral ;
• le circuit photonique intégré d’émission comprend au moins un dispositif optique additionnel disposé entre la source laser et l’amplificateur optique à semiconducteur ;
• le dispositif optique additionnel est un modulateur ou un commutateur.

According to other advantageous and non-limiting characteristics of the invention, taken alone or in any technically feasible combination:

• the amplifying media of the laser source and the amplifying media of the amplifier are configured so that their respective photoluminescence wavelengths at the first temperature are separated by a wavelength difference less than or equal to their temperature drifts at the second temperature;
• the first amplifying medium is chosen so that, over a temperature range between the first temperature and the second temperature, the gap existing between the emission wavelength and the first photoluminescence wavelength is less than half a bandwidth of the first amplifying medium;
• the integrated photonic emission circuit comprises a plurality of laser sources having a first amplifying medium of identical composition, a plurality of semiconductor optical amplifiers having a second amplifying medium of identical composition, and a plurality of waveguides respectively arranged between the laser sources and the semiconductor optical amplifiers to respectively transmit the light rays produced by the laser sources to the semiconductor optical amplifiers;
• the integrated photonic emission circuit comprises a plurality of complementary semiconductor optical amplifiers having a second complementary amplifying medium of identical composition and having a complementary photoluminescence wavelength less than or equal, at the first temperature, to the second photoluminescence wavelength;
• the integrated photonic transmitting circuit comprises, optically downstream of the plurality of semiconductor optical amplifiers and the plurality of complementary semiconductor optical amplifiers, a plurality of optical switches, each optical switch being connected to a semiconductor optical amplifier and to a complementary semiconductor optical amplifier;
• the integrated photonic emission circuit comprises a plurality of laser sources and a plurality of semiconductor optical amplifiers, the laser sources and the semiconductor optical amplifiers having in pairs an amplifying medium of the same composition, and a plurality of waveguides respectively arranged between laser sources and semiconductor optical amplifiers having amplifying media of different compositions;
• the integrated photonic emission circuit further comprises a wavelength division multiplexer arranged downstream of the plurality of semiconductor optical amplifiers and optically connected to the semiconductor optical amplifiers to produce multispectral light radiation;
• the integrated photonic emission circuit comprises at least one additional optical device arranged between the laser source and the semiconductor optical amplifier;
• the additional optical device is a modulator or a switch.

BRIEF DESCRIPTION OF THE FIGURES

Other characteristics and advantages of the invention will emerge from the detailed description of the invention which follows with reference to the appended figures in which:

There illustrates the phenomenon of thermal drift applying to an integrated photonic emission circuit and its impact on the power of the light radiation produced by this circuit;

Figures 2a, 2b represent, in top view, the basic diagram of an integrated photonic emission circuit 1 according to implementation modes;

There represents, in a power/wavelength frame, the evolution of the gains of the amplifying media A1, A2 and of the emission wavelength L _bragg of the photonic circuit 1 configured according to the invention, with the operating temperature of the circuit;

There represents an integrated photonic emission circuit in a parallel configuration;

There represents another mode of implementation of an integrated photonic circuit in parallel configuration;

There illustrates the operation of the photonic circuit of the ;

There represents an example of another mode of implementation of a photonic circuit according to the invention, in series configuration.

DETAILED DESCRIPTION OF THE INVENTION

There represents, in top view, the block diagram of an integrated photonic emission circuit 1 according to an implementation mode. This photonic circuit 1 comprises, monolithically integrated on a substrate, a laser source LS, a semiconductor optical amplifier SOA (more simply referred to as an “amplifier” in the remainder of this description), and a waveguide WG arranged between the laser source LS and the amplifier SOA.

The laser source LS comprises a first amplifying medium A1. This medium, as has already been presented in the introduction to this application, is formed of a stack of layers of III-V materials constituting at least one hetero junction, for example based on InP, AsGa, InGaAlAs, InGaAsP or InAsP. The first amplifying medium A1 here takes the general form of a ribbon arranged at right angles to a first coupling portion of a waveguide WG1, for example made of silicon, in which an optical mode is established when the first amplifying medium A1 is crossed by a first current. For the sake of simplification, it has been omitted to represent on the block diagram of the , the circuits, tracks and contacts allowing the injection of this current.

The first amplifying medium A1 having a first photoluminescence wavelength L ₁ which depends on the composition of an active region of this medium and its operating temperature. The active region may correspond to quantum wells based on III-V quaternary compounds (InGaAlAs, InGaAsP) or quantum dots based on InGaAs. The active region is sandwiched between a layer of N-type semiconductor material and a layer of P-type semiconductor material. These layers, typically based on InP or AsGa, make it possible to circulate a current in the active region, and to electrically pump the amplifying medium in order to allow the generation of light.

The laser source also comprises a grating G made in the first amplifying medium A1 or in the first waveguide portion WG1, for example a Bragg grating. The grating G defines, in particular through its pitch, an emission wavelength L _bragg of the laser source LS.

Continuing the description of the principle diagram of the , the SOA amplifier comprises a second amplifying medium A2 having a second photoluminescence wavelength L _gain . This second amplifying medium A2 is different from the first amplifying medium A1, that is to say that it is composed of a stack of III-V materials of compositions different from the III-V materials making up the first amplifying medium A1. Consequently, the second photoluminescence wavelength L _gain is different from the first photoluminescence wavelength L ₁ .

The second amplifying medium A2 also takes the general form of a block arranged at right angles to a second portion of waveguide WG2, extending between an input and an output of the amplifier, and in which the optical mode generated by the laser source LS propagates and is amplified when this second medium A1 is crossed by a second current. For the sake of simplification, it has been omitted to represent on the block diagram of the , the circuits, tracks and contacts allowing the injection of this current.

In any event, the first current flowing in the first amplifying medium A1 and the second current flowing in the second amplifying medium A2 are distinct from each other, these two media being electrically isolated. Each of these media A1, A2 is provided with contacts, tracks and circuits making it possible to control these currents, and the operation of the laser source and the amplifier SOA independently of each other.

It is noted that the independent control of the gain of the laser source and the gain of the SOA amplifier, by injecting different currents into them, forms a notable advantage of a photonic circuit according to the invention, in that it offers a capacity for adaptation of these gains according to the temperature.

The passive waveguide WG is arranged between the laser source LS and the input of the amplifier SOA to transmit the light radiation produced by this source LS to the amplifier SOA. It connects the first waveguide portion WG1 and the second waveguide portion WG2, which are therefore not arranged end to end as is the case in the photonic circuits of the prior art reported in the introduction to this application.

It is noted that the amplifying media A1, A2 of the laser source LS and the amplifier SOA being distinct from each other, electrically isolated from each other, and formed of materials of different compositions, they cannot be contiguous or constituted of a single monolithic block of material. They are therefore separated by a separation distance d, this separation requiring the presence of the waveguide WG to propagate the optical mode from the laser source LS to the amplifier SOA.

Of course, the integrated photonic emission circuit 1 can have other elements which can be, for example, optically inserted between the laser source LS and the amplifier SOA, via a plurality of waveguides GW. Thus, the , a photonic circuit 1 of another embodiment, comprising a modulator MOD, optically connected by waveguides WG to the laser source LS and to the amplifier SOA. In FIGS. 2a and 2b, an output waveguide WG3 has also been shown, optically connecting the output of the amplifier to, for example, a component allowing the coupling of the optical flow from the photonic circuit 1 to an optical fiber. Other coupling configurations of the photonic circuit 1 are alternatively possible, for example via a surface grating coupled to the output waveguide WG3.

There represents, in a power/wavelength frame, the evolution of the gains of the amplifying media A1, A2 and of the emission wavelength L _bragg of the photonic circuit 1 configured according to the invention, with the operating temperature of the circuit.

At a first relatively low operating temperature T0, which may correspond to room temperature (20°C), the emission wavelength L _bragg (T0) is arranged in the gain bandwidth of the first amplifying medium A1, at a wavelength greater than the wavelength L ₁ (T0) of the gain peak. This configuration is obtained by choosing the nature of the first amplifying medium A1 and by defining the parameters of the lattice of the laser source LS.

For example, at a first temperature corresponding to room temperature (20°C), the emission length L_braggis 1330nm, and the photoluminescence wavelength L₁ of the first amplifying medium A1 (the gain peak of this first medium) is chosen to correspond to 1315nm.

The gain bandwidth of the second amplifier medium A2 (in thick line on the ) is configured, by choosing the nature of the materials constituting this medium, to be shifted from the gain bandwidth of the first amplifying medium A1 towards the shorter wavelengths. However, it will be advantageous to ensure that the amplifier SOA is "transparent", i.e. that its gain at the emission wavelength L _bragg of the laser source LS is not less than 0 dB, at the first temperature T0.

For example, the photoluminescence wavelength L_gain of the second amplifying medium A2 (the gain peak of this second medium) is chosen to correspond to 1300nm, i.e. 15nm lower than the photoluminescence wavelength of the first medium L₁

In this configuration at the first temperature T0, and as is clearly visible on the , the emission wavelength L _bragg is closer to the first photoluminescence wavelength L ₁ than to the second photoluminescence wavelength L _gain .

The SOA amplifier contributes little to the amplification of the optical mode produced by the LS laser source. The optical mode produced by the LS laser source alone has sufficient power, above a determined threshold, and requires little or no additional amplification.

As the operating temperature of the photonic circuit increases, the emission wavelength L _bragg and the first and second photoluminescence wavelengths L ₁ , L _gain drift with different dynamics.

Thus, at a second relatively high operating temperature T1, which can be 80°C or 100°C, the first and second photoluminescence wavelengths L₁, L_gain are shifted towards the longer wavelengths by a difference which is of the order of 0.6nm per °C of temperature rise (i.e. the difference T1-T0). The gain functions of the first and second amplifying media A1,A2 are also of smaller amplitudes at the second temperature T1 than at the first T0. The emission wavelength L_braggis shifted towards the longer wavelengths by a difference of the order of 0.1nm per °C of temperature rise (T1-T0).

Continuing the example described above, and taking the second temperature T2 at 80°C, 60° higher than the first temperature T0 chosen at room temperature, the emission wavelength L_bragg(T1) is shifted by 6nm to 1336nm, and the first and second photoluminescence wavelengths L₁, L_gain are shifted by 36nm to 1351nm and 1336nm respectively.

Also, and due to this differentiated temperature drift dynamics, the emission wavelength L _bragg (T1) is arranged, at the second operating temperature T1, in the gain bandwidth of the first amplifying medium A1, at a wavelength lower than the wavelength L ₁ (T1) of the gain peak. This emission wavelength L _bragg (T1) is also arranged in the gain bandwidth of the second amplifying medium A2.

At the second temperature T1, the emission wavelength L _bragg is closer to the second photoluminescence wavelength L _gain than to the first photoluminescence wavelength L ₁ .

As a result, the SOA amplifier contributes to the amplification of the optical mode produced by the LS laser source. This amplification makes it possible to at least compensate for the lower gains of the amplifier media A1, A2 at the relatively higher temperature T1, in order to maintain an optical mode of sufficient power, higher than the determined threshold.

By differentiating the two amplifying media A1, A2 of the laser source LS and the amplifier SOA and by configuring them so that their photoluminescence wavelength L ₁ , L _gain is shifted by a wavelength difference less than or equal to their temperature drift over a target temperature range [T0-T1], it is ensured that the optical mode produced by the laser source LS is sufficiently amplified, by the first amplifying medium A1 of the laser source LS and/or by the second amplifying medium A2 of the amplifier SOA to maintain its power, over the extended target temperature range, above the determined threshold.

Advantageously, the first amplifying medium A1 is chosen so that, over a temperature range between the first temperature T0 and the second temperature T1, the difference D existing between the emission wavelength L _bragg and the first photoluminescence wavelength L ₁ is less than a half-bandwidth BW/2 of the first amplifying medium A1. In this way, it is ensured that over the entire temperature range [T0-T1], the laser source produces an optical mode whose power is greater than a minimum power. The bandwidth BW of the first amplifying medium A1 can for example be set at 3 dB, as is usual.

The first temperature T0 can be room temperature and the second temperature can be 60°C, 80°C or 100°C depending on the operating range targeted by the photonic circuit 1.

The principles of the invention which have just been set out can be deployed in numerous modes of implementation.

So, the represents an integrated photonic circuit 1 for emission in a parallel configuration. This circuit comprises a plurality of identical laser sources LS. These laser sources LS therefore each comprise a grating defining the same emission wavelength L _bragg . They also each comprise a first amplifying medium A1, these amplifying media A1 all being of the same composition and therefore defining the same first photoluminescence wavelength L ₁ . Advantageously, this medium comes from a single monolithic block of III-V materials formed at the level of a plurality of first portions WG1 of waveguides, and structured to define the plurality of laser sources LS therein, as was explained in the introduction to this application.

The photonic circuit 1 also comprises a plurality of semiconductor optical amplifiers SOA each comprising a second amplifying medium A2 having the same composition and therefore defining the same second photoluminescence wavelength L _gain . Advantageously, and as has been explained in the case of the first amplifying medium A1, this second medium A2 comes from a single monolithic block of III-V materials formed and structured at right angles to a plurality of second waveguide portions WG2.

Finally, the photonic circuit 1 comprises a plurality of waveguides WG,WG' arranged between the laser sources LS and the semiconductor optical amplifiers SOA to respectively transmit the light radiation produced by the laser sources LS to the semiconductor optical amplifiers SOA. In the embodiment shown in FIG. , MOD modulators are also provided, respectively arranged between a laser source LS and an amplifier SOA to form an integrated photonic transmission circuit, but this element is perfectly optional or could be replaced by an optical element providing another function.

The nature of the amplifying media A1, A2 and the emission wavelength L _bragg are chosen in accordance with what was presented during the description of the previous figures: very generally, at the first temperature T0, the emission wavelength L _bragg is closer to the first photoluminescence wavelength L ₁ than to the second photoluminescence wavelength L _gain . At the second temperature T1, higher than the first temperature T0, the emission wavelength L _bragg is closer to the second photoluminescence wavelength L _gain than to the first photoluminescence wavelength L ₁ .

There represents another mode of implementation of a photonic circuit 1 in parallel configuration.

We find in the photonic circuit of this , a plurality of LS laser sources and MOD modulators in the same configuration as that presented in the . Each laser source LS is optically connected to an input of a modulator MOD via a waveguide WG. Output channels of the modulators MOD are respectively connected by other waveguides WG' to semiconductor optical amplifiers SOA having the same second amplifying medium A2. These elements are configured similarly to the configuration of the implementation mode of the .

Advantageously, the MOD modulators each have two outputs in phase opposition. This can therefore be a silicon modulator of the Mach Zender type. Alternatively, the modulators could be replaced by simple switches, also having two outputs on which the energy of the light radiation propagating from their inputs is distributed.

In the case of the integrated circuit of the , the second output (not connected to the semiconductor optical amplifier SOA) is optically connected, via the waveguides WG', to a plurality of complementary semiconductor optical amplifiers SOA2. These complementary amplifiers SOA2 have the same complementary amplifying medium A2', different from the second amplifying medium A2. More precisely, the complementary amplifying medium A2' has a complementary photoluminescence wavelength L _gain2 less than or equal, at the first temperature T0, to the second photoluminescence wavelength L _gain .

We observe as illustrated in the , that such a configuration of the photonic circuit makes it possible to extend the operating temperature range of the photonic circuit, the complementary amplifiers SOA2 ensuring the amplification of the optical modes when the temperature drift no longer allows the SOA amplifiers to ensure sufficient gain.

Downstream of the SOA amplifiers and the SOA2 complementary amplifiers, a plurality of optical switches SW are provided making it possible to select, from the plurality of outputs of the SOA amplifiers and the SOA2 complementary amplifiers, and according to the effective operating temperature of the circuit 1, the amplified radiation which is propagated by the WG3 output waveguides to the emission output of the integrated photonic circuit 1.

More precisely, at a relatively low temperature the switches are operated to propagate towards the output waveguides WG3 the radiations coming from the amplifiers SOA. At a relatively high temperature, the switches are operated to propagate by the output waveguides WG3 the radiations coming from the complementary amplifiers SOA2.

There represents an example of yet another mode of implementation of a photonic circuit 1 according to the invention, this time in a so-called wavelength multiplexed configuration.

In this configuration, a plurality of LS laser sources₁-LS₅and a plurality of SOA semiconductor optical amplifiers₁-SOA₅, comprise two by two an amplifying medium A’₁-HAS'₅of identical constitution. In other words, an amplifying medium of unique composition A_iis placed at the right of a first portion of waveguide of a laser source LS_iand to the right of a second portion of waveguide of an SOA amplifier_i. A plurality of waveguides WG, WG’ are respectively arranged between laser sources LS._iand SOA optical amplifiers_i+1, the first amplifying medium A_ifrom the LS laser source_ibeing of different composition from the second amplifying medium A_i+1 of the optical amplifier SOA_i+1, to respectively transmit the light rays produced by the LS laser sources_ito semiconductor optical amplifiers SOA_i+1.

In the example shown, the photonic circuit comprises 5 types of amplifying media A’₁-HAS'₅, each from a block of III-V material formed and structured at the level of a first portion of waveguide of an LS laser source and a second portion of waveguide of an SOA amplifier. The LS laser source_i is also equipped with a network defining an emission wavelength L_{bragg ,i}. The nature of the amplifying medium A’_iand the emission wavelength L_{bragg ,i}are therefore chosen to allow the proper functioning of the LS laser source_iand the SOA amplifier_I.

In the circuit shown, there are a plurality of laser sources LS_ieach having an emission wavelength L_{bragg ,i} different and a plurality of SOA amplifiers_i. The emission wavelengths L_{bragg , 1 -}L_{bragg, 5} are stepped (1330 nm, 1310 nm, 1290 nm, 1245 nm, 1270 nm and 1225 nm as shown in the ) to provide a plurality of light rays intended to be combined or multiplexed in wavelengths between them and to form, at the output of the photonic circuit 1, a multi-wavelength radiation. The materials of the amplifying media A’₁-HAS'₅ are chosen to also stage their photoluminescence wavelength (1305 nm, 1285 nm, 1265 nm, 1245 nm and 1225 nm).

As can be seen on the , WG waveguides make it possible to optically couple a laser source LS comprising a first amplifying medium A' _i having a first photoluminescence wavelength to an amplifier SOA comprising a second amplifying medium A' _i+1 having a second photoluminescence wavelength.

This chaining by the waveguides WG,WG' is repeated to couple a laser source LS _i associated with a first amplifier medium A _i to an amplifier SOA _i+1 associated with a second amplifier medium A _i+1 , different from the first.

Note that in the chaining shown in the , the first amplifier of the SOA ₁ chain, associated with the amplifier medium designated A' ₁ in this figure, and the last laser source LS ₅ , associated with the amplifier medium designated A' ₅ in the figure, are not used. Since these two elements are not used, they can therefore be omitted.

This mode of implementation, multiplexed in wavelengths, has the advantage of limiting the number of amplification media of different composition (of tiles) for the manufacture of the optical device by pooling their exploitation. 5 tiles of different natures are necessary for example to realize the structure of the , these blocks being structured to produce the first and second amplification media associated with the 4 LS laser sources_i and to the 4 SOA amplifiers_i, i.e. 8 amplifying media.

Of course, the invention is not limited to the methods of implementation described and variant embodiments can be made without departing from the scope of the invention as defined by the claims.

Claims (10)

Integrated photonic emission circuit (1) comprising:

• a laser source (LS) for producing light radiation and comprising a grating defining an emission wavelength (L _bragg ) and a first amplifying medium (A1) having a first photoluminescence wavelength (L ₁ );
• a semiconductor optical amplifier (SOA) comprising a second amplifying medium (A2), electrically isolated from the first amplifying medium (A1) and spaced apart by a separation distance (d) from the first amplifying medium (A1), the semiconductor optical amplifier (SOA) having a second photoluminescence wavelength (L _gain );
• at least one passive waveguide (WG) arranged between the laser source (LS) and the semiconductor optical amplifier (SOA) for transmitting the light radiation produced by the laser source (LS) to the semiconductor optical amplifier (SOA);

the laser source (LS) and the semiconductor optical amplifier (SOA) being configured so that:

1. at a first temperature of 20°C (T0), the emission wavelength (L _bragg ) is closer to the first photoluminescence wavelength (L ₁ ) than to the second photoluminescence wavelength (L _gain ), and;
2. at a second temperature of 80°C (T1), the emission wavelength (L _bragg ) is closer to the second photoluminescence wavelength (L _gain ) than to the first photoluminescence wavelength (L ₁ ).

Integrated photonic emission circuit (1) according to claim 1 in which the amplifying media (A1) of the laser source (LS) and the amplifying media (A2) of the amplifier (SOA) are configured so that their respective photoluminescence wavelengths (L ₁ , L _gain ) at the first temperature of 20°C (T0) are separated by a wavelength difference less than or equal to their temperature drifts at the second temperature (T2). Integrated photonic emission circuit (1) according to one of the preceding claims, in which the first amplifying medium (A1) is chosen so that, over a temperature range between the first temperature of 20°C (T0) and the second temperature (T1), the gap (D) existing between the emission wavelength (L _bragg ) and the first photoluminescence wavelength (L ₁ ) is less than half a bandwidth of the first amplifying medium (A1). Integrated photonic emission circuit (1) according to one of the preceding claims comprising a plurality of laser sources (LS) having a first amplifying medium (A1) of identical composition, a plurality of semiconductor optical amplifiers (SOA) having a second amplifying medium (A2) of identical composition, and a plurality of waveguides respectively arranged between the laser sources (LS) and the semiconductor optical amplifiers (SOA) to respectively transmit the light radiation produced by the laser sources (LS) to the semiconductor optical amplifiers (SOA). Integrated photonic emission circuit (1) according to claim 4 comprising a plurality of complementary semiconductor optical amplifiers (SOA2) having a second complementary amplifying medium (A2') of identical composition and having a complementary photoluminescence wavelength (L _{gain 2} ) less than or equal, at the first temperature of 20°C (T0), to the second photoluminescence wavelength (L _gain ). Integrated photonic emission circuit (1) according to the preceding claim comprising, optically downstream of the plurality of semiconductor optical amplifiers (SOA) and the plurality of complementary semiconductor optical amplifiers (SOA2), a plurality of optical switches (SW), each optical switch being connected to a semiconductor optical amplifier (SOA) and to a complementary semiconductor optical amplifier (SOA2). Integrated photonic emission circuit (1) according to one of claims 1 to 3 comprising a plurality of laser sources (LS _i ) and a plurality of semiconductor optical amplifiers (SOA _i ), the laser sources and the semiconductor optical amplifiers (LS _i , SOA _i ) having two by two an amplifying medium of the same composition, and a plurality of waveguides (WG, WG') respectively arranged between laser sources (LS _i ) and semiconductor optical amplifiers (SOA _i+1 ) having amplifying media of different composition. Integrated photonic emission circuit (1) according to the preceding claim further comprising a wavelength division multiplexer (MUX) arranged downstream of the plurality of semiconductor optical amplifiers (SOA _i ) and optically connected to the semiconductor optical amplifiers (SOA _i ) to produce multispectral light radiation. Integrated photonic emission circuit (1) according to one of the preceding claims, comprising at least one additional optical device arranged between the laser source (LS) and the semiconductor optical amplifier (SOA). Integrated photonic emission circuit (1) according to the preceding claim in which the additional optical device is a modulator (MOD) or a switch.