Pulsed laser and associated component

Abstract

The present invention relates to a pulsed laser (10) comprising: - an insulating substrate (12); - a rib (14) extending over the substrate (12) in a direction of extension (X), the rib (14) having a plurality of through-holes (24) aligned in the direction of extension (X), the rib (14) comprising a set of layers partially coated with a coating layer referred to as a passivation layer, the coating layer being capable of inhibiting non-radiative recombination on the surface of the portions of layers that are covered and said coating layer covering the layers only in one portion, the rib (14) thus comprising an uncoated region (32) and a coated region (34), the rib (14) forming a resonant cavity for at least one electromagnetic wave in a single mode; - an excitation element (16) capable of exciting only the coated region (34) of the rib (14).

Description

[0001] Pulsed laser and associated component

[0002] The present invention relates to a pulsed laser, as well as to an optical component comprising such a laser.

[0003] The development of the internet and connected sensors has led to the acquisition of considerable amounts of data. This phenomenon, often referred to as "big data," involves the use of computers to exploit all of the data obtained. Such exploitation can be used in multiple fields, including automatic data processing, diagnostic assistance, predictive analysis, autonomous vehicles, bioinformatics, and surveillance.

[0004] To implement such exploitation, it is known to use machine learning algorithms that are part of programs that can be executed on processors such as CPUs or GPUs. A CPU is a processor, the acronym CPU coming from the English term "Central Processing Unit" while a GPU is a graphics processor, the acronym GPU coming from the English term "Graphic Processing Unit" literally meaning graphic processing unit.

[0005] Among the learning implementation techniques, the use of formal neural networks, and in particular deep neural networks, is increasingly widespread, these structures being considered very promising due to their performance for many tasks such as automatic data classification and pattern recognition.

[0006] A neural network is generally composed of a succession of layers of neurons, each of which takes its inputs from the outputs of the previous layer. More precisely, each layer includes neurons taking their inputs from the outputs of the neurons in the previous layer. Each layer is connected by a plurality of synapses. A synaptic weight is associated with each synapse. It is a real number, which takes both positive and negative values. For each layer, the input of a neuron is the weighted sum of the outputs of the neurons in the previous layer, the weighting being done by the synaptic weights.

[0007] By definition, a deep neural network is a network with more than three layers of neurons and a large number of neurons per layer.

[0008] For implementation in a CPU or GPU, a Von Neumann bottleneck problem arises because implementing a deep neural network involves using both the memory(ies) and the processor while these latter elements are spatially separated. This results in congestion of the communication bus between the memory(ies) and the processor.

[0009] It is therefore desirable to develop dedicated hardware architectures, bringing memory and computing closer together, to create fast, low-power neural networks capable of learning in real time.

[0010] Three architectural proposals are the subject of specific studies.

[0011] The first proposal is to use CMOS technology. It is understood by the acronym "CMOS", Complementary Metal Oxide Semiconductor (acronym coming from the English expression "CMOS"). The acronym CMOS refers to both a manufacturing process and a component obtained by such a manufacturing process. In such an architecture, neurons and synapses are CMOS components.

[0012] A second proposal is to use CMOS neural networks and memristive synapses. Memristive synapses are synapses using memristors. In electronics, a memristor (or memristance) is a passive electronic component. The name is a portmanteau of the two English words memory and resistor. A memristor efficiently stores information because the value of its electrical resistance changes permanently when a current is applied.

[0013] Finally, according to a third proposal, we seek to create optical neural networks and optical synapses.

[0014] For this last proposal, it is necessary to have for the realization of the neurons an optical component capable of generating pulses whose frequency depends on the level of excitation in a manner at least quasi-continuous.

[0015] For this purpose, there are laser diodes capable of emitting pulses depending on the excitation level. The term "neuron laser" is often used to refer to such laser diodes.

[0016] An example of a neuron laser implementation is described in particular in the article by S. Barbay et al. entitled "Excitability in a semiconductor laser with saturable absorber" in Optics letters, vol. 36, page 4476-4478 dated 2011. The concept is taken up in the context of "neuromorphic computing" in the article by MA Nahmias et al. entitled "A leaky integrate-and-fire laser neuron for ultrafast cognitive computing" taken from the journal IEEE Journal of Selected Topics in Quantum Electronics, volume 19, number 5 of 2013.

[0017] However, this technique does not lend itself easily to exploitation because the vertical geometry of the laser cavity is not compatible with the planar approach of integrated photonics; the emission wavelength is absorbed by the Silicon, and the energy efficiency is very low.

[0018] There is therefore a need for a pulsed laser capable of generating pulses whose frequency depends on the excitation level in an at least quasi-continuous manner and which can be easily integrated into a photonic circuit, for example in Silicon on oxide, having a smaller size and having an efficiency compatible with energy efficiency requirements.

[0019] For this purpose, the description describes a pulsed laser comprising:

[0020] - an insulating substrate,

[0021] - a rib extending over the substrate in a direction of extent, the rib having a plurality of through-orifices aligned with the direction of extent, the rib comprising a set of layers stacked in a stacking direction orthogonal to the direction of extent (X), the set of layers being partially coated with a coating layer, called a passivation layer, the coating layer being capable of inhibiting non-radiative recombination on the surface of the portions of layers that the coating layer covers, the coating layer covering the layers only over a portion, the rib thus comprising an uncoated zone and a coated zone, the rib forming a resonant cavity for at least one electromagnetic wave, the cavity being capable of resonating a single mode,

[0022] - an excitation element for the coated area of ​​the rib, the excitation element being capable of exciting only the coated area of ​​the rib.

[0023] According to particular embodiments, the control method has one or more of the following characteristics, taken in isolation or in all technically possible combinations:

[0024] - a length is defined for each zone, the length being the dimension along the direction of extension and the variation in the density of orifices in the rib are chosen so that the rib exhibits a resonance mode having a quality factor strictly greater than 10 times the quality factor of all the other modes, for example the length being the dimension along the direction of extension and the variation in the density of orifices in the rib are chosen so that the rib exhibits a resonance mode having a quality factor strictly greater than 10 4and that the quality factors of all other embodiments are less than or equal to 10 3 .

[0025] - the density of orifices in the rib varies according to the direction of extension according to a variation law, the variation law being continuous and comprising three pieces, a first piece in which the density is equal to a first density value, a second piece in which the density is equal to a second density value, the third piece connecting the first piece and the second piece according to a polynomial function, the minimum value of the density being in the third piece.

[0026] - the first density value and the second density value are identical.

[0027] - the polynomial function has a parabolic form.

[0028] - the polynomial function is of order at least four, and is described by a formula of the type: Or :

[0029] - x and y are the input and output variables of the polynomial function,

[0030] - n is an integer greater than or equal to 2, and

[0031] - Ai are constants.

[0032] - each orifice is separated from each neighboring orifice by a spacing, the spacings each having a dimension, measured according to the direction of extension, which varies according to the direction of extension according to the law of variation.

[0033] - the rib has a width, the width being a dimension measured in a direction perpendicular to the direction of extent, which varies according to the direction of extent according to the law of variation.

[0034] - the coated area is separated from the uncoated area by a gap extending mainly in a direction perpendicular to the direction of extension, the gap preferably being located in the direction of extension at an orifice.

[0035] - the dimension of the gap according to the direction of extension is between 20 nanometers and 40 nanometers.

[0036] - the laser further comprises a waveguide defined in the substrate, extending in a guiding direction, the waveguide being separated from the rib by a non-zero distance in the direction.

[0037] - the laser comprises a plurality of successive ribs and a waveguide defined in the substrate, extending in a guiding direction, the waveguide being arranged to guide the output wave of a rib to excite the following rib. The description also relates to a component, in particular neuromorphic, comprising a laser as previously described. In the present description, the expression "suitable for" means indifferently "adapted for", "adapted to" or "configured for".

[0038] Furthermore, in all that follows, the expression "between two values" is understood to mean a framework in the broad sense, that is to say including the values ​​of the limits.

[0039] Characteristics and advantages of the invention will appear on reading the description which follows, given solely by way of non-limiting example, and made with reference to the appended drawings, in which:

[0040] - figure 1 is a schematic view of an example of a laser according to the invention,

[0041] - Figure 2 is a side sectional view of a portion of the laser of Figure 1,

[0042] - Figure 3 is a schematic representation of part of another example of a laser,

[0043] - Figure 4 is a schematic representation of a part of yet another example of a laser,

[0044] - Figures 5 and 6 are schematic representations of part of a laser variant, and

[0045] - Figure 7 is a schematic representation of a part of yet another embodiment of a laser.

[0046] A laser 10 is shown in Figure 1.

[0047] The term "laser" refers to a photonic system that produces spatially and temporally coherent light radiation based on the laser effect (acronym from the English light amplification by stimulated emission of radiation).

[0048] A laser source combines an optical amplifier with an optical cavity in which the light radiation is partially confined, also called a resonator. Each time the light radiation passes through the cavity, part of the light leaves the cavity and the other part is reinjected into the cavity and the amplifier to be amplified.

[0049] The laser 10 is a pulsed laser, that is to say capable of emitting electromagnetic waves corresponding to an emission of pulses when the laser receives an excitation exceeding a threshold.

[0050] This desired operation is independent of the nature of the excitation (optical or electrical in particular).

[0051] Very schematically as in figure 1, the laser 10 comprises a substrate 12, a cavity-forming rib 14 and an excitation element 16.

[0052] The substrate 12 is a layer forming a plate on which the rib 14 rests. According to the example described, the substrate 12 is transparent to the emitted radiation and is made of a material having a refractive index of less than 2.1.

[0053] The rib 14 is arranged to form an optical guide in which at least one electromagnetic wave propagates having frequencies from a range of frequencies of interest.

[0054] According to the example described, the rib 14 is made of a material having a refractive index greater than 2.5.

[0055] The rib 14 constitutes a resonant cavity for the electromagnetic wave, that is to say a confined propagation medium for the electromagnetic wave.

[0056] The rib 14 extends mainly in a direction of extent X.

[0057] More specifically, the rib 14 comprises a central portion 20 extending between two end portions 22 as well as a plurality of orifices 24.

[0058] The central part 20 is a rectilinear part extending in the direction of extension X.

[0059] In this direction of extent, the rib 14 has a set of layers stacked according to a stacking direction Z orthogonal to the direction of extent X.

[0060] The orifices 24 are cylindrical perforations passing through the central part 20 of the rib 14.

[0061] By the term “through”, it is understood that each orifice 24 passes through all the layers of the rib 14, in the stacking direction Z, up to the upper face of the substrate 12.

[0062] The holes 24 are aligned along the rib 14.

[0063] In the example of Figure 1, each orifice 24 has a circular section and a constant diameter from one orifice 24 to the next.

[0064] Each orifice 24 extends along a central axis parallel to the stacking direction Z.

[0065] The central axis extends in a median plane of the central part 20, perpendicular to the transverse direction Y. The choice of the diameter of the orifices 24 relative to the width of the rib 14, as well as the distribution of the orifices along the central part 20 allow the rib 14 to form a photonic crystal.

[0066] By the term "photonic crystal" is meant a periodic structure of dielectric or semiconductor materials modifying the propagation of electromagnetic waves in the same way as a periodic potential in a semiconductor crystal affects the movement of electrons by creating allowed and forbidden energy bands. According to the example described, the set of layers is partially coated with a coating layer 30.

[0067] The coating layer 30 only covers the layers of the layer set over a portion, the rib 14 thus comprising an uncoated area 32 and a coated area 34.

[0068] As shown schematically in Figure 2, the coating layer 30 covers both the top layer of the layer assembly and the periphery 36 of the orifices 24.

[0069] By covering the periphery 36 of the orifices 24, the coating layer 30 is in contact with all of the other layers of the set of layers.

[0070] The central part 20 can thus be divided into two parts, a first part corresponding to the uncoated zone 32 comprising the layer portions of the set of layers without contact with the coating layer 30 and a second part corresponding to the coated zone 34 comprising the layer portions of the set of layers in contact with the coating layer 30.

[0071] Seen from above as in Figure 1, areas 32 and 34 have a rectangular shape, with the layers forming part of areas 32 and 34 not being visible.

[0072] The coating layer 30 has at all points a thickness less than or equal to 5 nm, preferably 1 nm.

[0073] In the example described, the coating layer 30 is capable of inhibiting non-radiative recombination on the surface of the layer portions that the coating layer 30 covers.

[0074] Such a coating layer can be obtained by chemical or plasma deposition or by physical vapor deposition or by chemical vapor deposition or by atomic thin film deposition (ALD).

[0075] The chemical route consists, for example, of carrying out sulfurization of the surfaces of the different parts of the layers to be passivated.

[0076] This makes it possible to reduce surface recombination, the characteristic time associated with recombination being increased from approximately 200 picoseconds without the coating layer 30 to more than 2 ns in the presence of the coating layer 30.

[0077] The coating layer 30 can thus be described as a passivation layer 30.

[0078] Also, in the following, the uncoated area 32 will be referred to as the unpassivated area 32 and the coated area 34 will be referred to as the passivated area 34.

[0079] The excitation element 16 is capable of injecting free carriers into the passivated zone 34, which makes it possible to generate a population inversion in the active medium. Consequently, the population of excited carriers is much lower in the non-passivated zone 32.

[0080] Thus, the passivated zone 34 plays the role of a gain zone while the non-passivated zone 32 will play the role of a saturable absorber.

[0081] The excitation element 16 can be produced optically or electrically, in particular by a laser or electrical contacts positioned at predefined locations.

[0082] Assuming that the materials used are fixed, it is possible to envisage numerous geometric arrangements of the laser 10 shown schematically in Figure 1, these arrangements depending on the geometric parameters which can be modified.

[0083] As a non-limiting example of material, the substrate 12 may be made of silicon oxide and the rib 14 is formed from a multi-layer assembly of type III-V semiconductor materials.

[0084] Furthermore, a very thin layer (thickness strictly less than 50 nm) of semiconductor material is arranged between the substrate 12 and the rib 14 to electrically connect the rib 14 to the excitation element 16.

[0085] A "III-V" type semiconductor is a compound semiconductor made from one or more elements from column III of the periodic table of elements (boron, aluminum, gallium, indium, etc.) and one or more elements from column V or pnictogens (nitrogen, phosphorus, arsenic, antimony, etc.).

[0086] In the following, a number of examples will be described to achieve the desired operation with different geometric parameters.

[0087] For this, with reference to figure 3, geometric parameters that can be modified will be introduced.

[0088] One or more of these geometric parameters can then be optimized to obtain the desired operation for the laser 10, i.e. an emission of pulses when the laser 10 receives an excitation exceeding a threshold (neuron laser operation). An optimization procedure will also be described in the remainder of the description.

[0089] Examples of geometric parameters are the dimensions of the central portion 20, including its length and width.

[0090] The length of the central part 20 is a first example of such a parameter, it is the dimension of the central part 20 along the direction of extent X.

[0091] To give an order of magnitude of dimension, the length L c of central part 20 is less than or equal to 100 micrometers, in particular less than or equal to 50 micrometers. The rib 14 also has a width W, measured in the transverse direction Y.

[0092] According to the example of figure 1, the width W is constant over the entire extent of the central part 20.

[0093] The width W is, for example, between 0.4 micrometers and 1.01 micrometers.

[0094] However, as shown in Figure 3, the width may vary along the central portion 20.

[0095] It could also be considered to vary the dimensions and positions of the orifices, the corresponding parameters constituting such geometric parameters.

[0096] As for the shape, we could consider square, circular or oval shapes.

[0097] Thus, in the case of Figure 1, the circular shape involves a single parameter which is the value of the radius while the oval shape involves several parameters.

[0098] In the following, it is assumed that the circular shape is chosen and that the shape is not a parameter used for optimization.

[0099] An arrangement parameter is now described.

[0100] The orifices 24 are referenced below by an index n, starting from a first orifice bearing the index n = 0, chosen at one end of the rib 14, closest to one of the extreme parts of the rib 14.

[0101] Each orifice 24 of index n is separated from the next orifice of index n+1 by a spacing. The spacing separating two orifices 24 extends between the two points closest to the peripheries of the two orifices 24.

[0102] A dimension of the spacing separating the orifice 24 of index n from the orifice 24 of index n+1, measured along the direction of extent X, is noted a n .

[0103] The dimension a n varies from one spacing to another according to a variation law to be determined.

[0104] The law of variation is a function whose variable is the position x n holes.

[0105] The x position n of an orifice 24 of index n is the distance separating the axis of the orifice 24 of index n from the axis of the first orifice 24 of index n = 0.

[0106] As other geometric parameters, in the example described, for each zone 32 and 34, a length L32 or L34 can be defined as the dimension of zone 32 or 34 according to the direction of extent X.

[0107] A parameter could therefore be the value of the ratio between the two lengths.

[0108] Alternatively, the position of the boundary between the two zones 32 and 34 can be defined as a geometric parameter to be optimized, which is assumed in the following. In this example, the optimization procedure therefore seeks to determine values ​​for the aforementioned parameters that guarantee the desired operation for the laser 10.

[0109] In a first example, we assume that only the spacing and the position of the border between the two zones 32 and 34 are variable

[0110] Thus, the optimization procedure here aims to obtain the law of variation of the dimension from one spacing to another and the position of the border between the two zones 32 and 34.

[0111] The optimization procedure is based on the calculation of the different resonance modes of the cavity formed by rib 14.

[0112] Such a calculation is, for example, carried out by at least an approximate resolution of Maxwell's equations.

[0113] Such a resolution is carried out in particular by simulation tools.

[0114] For each resonance mode, the frequency v and the lifetime T are thus obtained.

[0115] It follows that, for each resonance mode, its associated quality factor Q can be determined, this quality factor being given by the following formula:

[0116] Q = 2TIVT

[0117] The different parameters are then chosen so that the quality factor of a mode is strictly greater than 10 4 whereas the quality factors of all other embodiments are less than or equal to 10 3 .

[0118] More generally, as other values ​​are possible for the quality factors, the different parameters are chosen so that the quality factor of a mode is strictly higher by a factor of 10 compared to the quality factors of the other modes.

[0119] The optimization procedure therefore corresponds to a classic optimization under constraint which can be carried out by any type of optimization technique, in particular by a least squares technique.

[0120] To illustrate what this optimization procedure leads to, a particular example is now described by particularizing the variation law.

[0121] The law of variation is piecewise continuous.

[0122] More precisely, according to the example described, the variation law has three pieces, namely a first piece M1 in which the dimension a n is equal to a first dimension value, a second piece M2 in which the dimension has n is equal to a second dimension value, the third piece M3 connecting the first piece and the second piece according to a polynomial function, the minimum value of the dimension a nbeing in the third piece M3. Preferably, the first dimension value and the second dimension value are identical.

[0123] In the following, the first dimension value and the second dimension value will be denoted Hmax-

[0124] The first and second pieces are therefore pieces in which the relation an — amax is verified.

[0125] Such a limitation to a maximum value at the ends makes it possible to weaken resonances other than the fundamental mode.

[0126] For example, the polynomial function of the third piece M3 is a symmetric polynomial function, of order at least equal to 2.

[0127] By the term "symmetric" it is understood that the odd order terms of the polynomial function are null.

[0128] Thus, a polynomial function for the third possible piece M3 is of the type: a n = ax n ~) = ax n2 + / 3

[0129] Where a and p are non-zero constants.

[0130] More generally, there comes a mathematical relationship of the type: Or :

[0131] - x and y are the input and output variables of the polynomial function,

[0132] - n is an integer greater than or equal to 2, and

[0133] - Ai are constants.

[0134] According to the proposed example, the polynomial function is a symmetric polynomial function of order 4.

[0135] According to the proposed example, the polynomial function for the third piece M3 is expressed in the form: a n = a xn) = a0+ Ax n 2 + Bx n 4

[0136] OR :

[0137] • ao is the dimension of the gap separating the orifice 24 of index 0 from the orifice

[0138] 24 of index 1, and

[0139] • A and B are non-zero constants.

[0140] The values ​​of the constants A and B are chosen to obtain the emission by the laser 10 of a desired electromagnetic wave.

[0141] More precisely, the value of A is chosen so as to fix a value of a free spectral interval of the rib 14. The value of B is chosen to maximize the quality factor of the chosen electromagnetic mode of the rib 14 (in other words, this is taken into account in the objective function of the optimization procedure).

[0142] The values ​​of ao, A and B are, for example, obtained by a numerical simulation of the operation of the laser 10.

[0143] For example, the value of ao is between 300 nanometers and 600 nanometers, more specifically between 330 nanometers and 350 nanometers.

[0144] According to the example shown, the value of ao is chosen to be equal to 340 nanometers.

[0145] For example, the value of A is chosen between 2 meters -1 and 3 meters -1 , more particularly between 2.2 meters -1 and 2.4 meters -1 .

[0146] According to the example shown, the value of A is chosen to be equal to 2.3 meters -1 .

[0147] For example, the value of B is chosen between 0.5 x 10 7 meters -3 and 4 x 10 7 meters -3 .

[0148] According to the example shown, the value of B is chosen equal to 0.5 x 10 7 meters -3 .

[0149] In the example described, furthermore, the ratio R between the length L34 of the passivated zone 34 and the length of the central part 20 of the rib 14 is between 30% and 70%, preferably between 40% and 60%.

[0150] The values ​​of A and B of the example presented were tested experimentally by simulations and measurements carried out by the applicant made it possible to validate such operation.

[0151] In particular, simulations with a value of L32 = 9 pm, L34 = 7 pm for a mode whose full width at half maximum of the spatial intensity distribution of the optical mode is 7 pm have shown operation with a regime where the laser emits pulses whose energy is between 10 and 100 fJ, the duration is between 30 picoseconds (ps) and 100 ps, ​​and the repetition frequency varies between a fraction of a GHz and around ten GHz, depending on the regime.

[0152] This shows that laser 10 is a pulsed laser whose repetition frequency, or even the emission of pulses itself, depends on the excitation.

[0153] More precisely, the pulse emission depends on the integral of the received excitation signal. Thus, the emission will be faster the higher the signal level.

[0154] Laser 10 is thus a laser emitting pulses at an adjustable frequency.

[0155] The laser 10 which has just been described has a very small size, of the order of a few pm 2 In this sense, laser 10 is a “nano-laser” since this laser is miniaturized.

[0156] In addition, the 10 laser consumes about 100 pW in operation, which corresponds to low power consumption. In addition, the 10 laser has a fast response, in the order of GHz.

[0157] The laser 10 can also be integrated into a silicon photonic circuit.

[0158] In fact, the laser 10 is here a nano-hybrid structure whose laser cavity and active zone, in III-V material, are transferred to a silicon photonic circuit.

[0159] This makes the 10 laser particularly suitable for realizing neurons in a physical implementation of a neural network.

[0160] More broadly, the 10 laser can be advantageously used in applications concerning communications, ultra-fast signal processing or analog computing.

[0161] Other embodiments of the laser 10 are conceivable and have advantages identical to those of the laser 10 described previously.

[0162] In the following, only the differences with the laser 10 of Figure 1 are detailed, the elements not mentioned being considered identical.

[0163] According to the example in Figure 3, the spacing a n is kept fixed but the width W varies according to the direction of extent X.

[0164] As an illustration, the variation of the width W presents a variation law similar to those described previously for the spacing a n .

[0165] According to a particular example, the width W is such that:

[0166] W(x) = min(W0+ Ax n 2 + Bx n 4 ; W max )

[0167] Where W o and V max are two constants.

[0168] It is possible, alternatively, to vary both the width W and the dimension a n .

[0169] In each case, the density of orifices in the rib varies according to the direction of extension according to a variation law, the variation law being such that the variation law is continuous and comprising three pieces, a first piece in which the density is equal to a first density value, a second piece in which the density is equal to a second density value, the third piece connecting the first piece and the second piece according to a polynomial function, the minimum value of the density being in the third piece.

[0170] This variation in density is obtained by varying one or more of the characteristic dimensions of the orifices 24 and the rib 14.

[0171] Such spatial modulation allows to obtain the existence of a single resonance mode in the cavity.

[0172] According to a variant illustrated by FIG. 4, the passivated zone 34 is separated from the non-passivated zone 32 by a gap 40 extending mainly in a direction perpendicular to the direction of extension X. The function of this gap 40 is to ensure the electrical separation of the two zones 32 and 34.

[0173] The gap 40 has a thickness (dimension along the direction of extent X) less than or equal to 40 nm.

[0174] Preferably, the gap 40 has a thickness greater than or equal to 20 nm.

[0175] Due to its dimensions, the gap 40 constitutes a nano-groove.

[0176] Preferably, the gap 40 is located at an orifice.

[0177] As visible in Figure 4, the gap 40 is thus formed by two through parts which open on the one hand onto the exterior and on the other hand onto the orifice 24.

[0178] Alternatively, it is possible to implant ions neutralizing the conductivity between the passivated 34 and non-passivated 32 zones on an area corresponding to the gap (but wider, covering at least one period of the rib 14)

[0179] For example, H+ ions could be implanted, so that the passivated 34 and non-passivated 32 zones will be in contact by a barrier zone preventing the passage of carriers.

[0180] Figures 5 and 6 show yet another embodiment.

[0181] According to this embodiment, the laser 10 further comprises a waveguide 44 defined in the substrate, extending in a guiding direction.

[0182] The waveguide 44 extends into the substrate 12, away from the upper face. The waveguide 44 is thus a waveguide buried in the substrate 12.

[0183] The waveguide 44 is a silicon channel extending through the substrate 12, in a guiding direction X'.

[0184] According to another example, the waveguide 44 is made of silicon nitride.

[0185] More generally, the waveguide 44 is made of a transparent material whose index is higher than that of the substrate 12.

[0186] The waveguide 44 is capable of collecting a portion of the electromagnetic wave propagating in the rib 14, in the form of evanescent waves passing through the substrate 12.

[0187] The waveguide 44 extends at a non-zero distance from the upper face 18 of the substrate 12 and from the rib 14.

[0188] The distance separating the waveguide 44 from the rib 14, measured in the transverse direction Y, may be constant or vary according to the direction of extension X.

[0189] The distance separating the waveguide 44 from the rib 14 is small enough for a portion of the electromagnetic wave propagating in the rib to be captured by the waveguide 44 in the form of an evanescent wave, through the insulating substrate 12. This distance is typically between 100 nm and 200 nm if the waveguide 44 is made of silicon, but may be greater, 2 or even 3 micrometers if the material constituting the waveguide 44 has a lower refractive index.

[0190] The waveguide 44 is also capable of guiding the collected electromagnetic wave in the guiding direction X', away from the rib 14.

[0191] The waveguide 44 has a prismatic shape of rectangular section in a plane orthogonal to the guiding direction X'.

[0192] The guide direction X' forms a coupling angle a with the extension direction X, in an XY plane parallel to the guide direction X and the transverse direction Y.

[0193] The coupling angle α is chosen so as to improve coupling between the rib 14 and the waveguide 44, that is to say so as to optimize the transmission of evanescent waves through the substrate 12, from the rib 14 to the waveguide 44.

[0194] The coupling angle a is, for example, between -15° and 15°.

[0195] According to a variant illustrated by figure 7, the laser 10 comprises a plurality of ribs 14 as well as a waveguide 44 similar to that of figures 5 and 6.

[0196] The waveguide 44 of Figure 7 is arranged to guide the output wave of one rib 14 to excite the next rib 14.

[0197] In the schematic example with three ribs 14, the waveguide 44 winds from the first rib 14 to the third rib 14 via the second rib 14.

[0198] In operation, the first rib 14 generates a signal at a first optical frequency v0.

[0199] This signal is transported by the waveguide 44 to the second rib 14.

[0200] The second rib 14 receives the signal at the first optical frequency v0 which excites it and emits a signal at a second frequency v1.

[0201] This signal is transported by the waveguide 44 to the third rib 14.

[0202] The third rib 14 receives the signal at the second optical frequency v ± which excites it and emits a signal at a third frequency v3.

[0203] This allows a network of cavities to be created.

[0204] The described embodiments can be combined in any technically feasible configuration.

Claims

CLAIMS 1. Pulsed laser (10) comprising: - an insulating substrate (12), - a rib (14) extending on the substrate (12) in a direction of extent (X), the rib (14) having a plurality of through-orifices (24) aligned with the direction of extent (X), the rib (14) comprising a set of layers stacked in a stacking direction (Z) orthogonal to the direction of extent (X), the set of layers being partially coated with a coating layer, called a passivation layer, the coating layer being capable of inhibiting non-radiative recombination on the surface of the portions of layers that the coating layer covers, the coating layer covering the layers only on a portion, the rib (14) thus comprising an uncoated zone (32) and a coated zone (34), the rib (14) forming a resonant cavity for at least one electromagnetic wave, the cavity being capable of resonating a single mode, and - an excitation element (16) for the coated area of ​​the rib, the excitation element (16) being capable of exciting only the coated area (34) of the rib (14).

2. Laser according to claim 1, in which a length is defined for each zone (32, 34), the length being the dimension along the direction of extension (X) and the variation in density of orifices (24) in the rib (14) are chosen so that the rib (14) has a resonance mode having a quality factor strictly greater than 10 times the quality factor of all the other modes, for example the length being the dimension along the direction of extension (X) and the variation in density of orifices (24) in the rib (14) are chosen so that the rib (14) has a resonance mode having a quality factor strictly greater than 10 4 and that the quality factors of all other embodiments are less than or equal to 10 3 .

3. Laser according to claim 1 or 2, in which the density of orifices in the rib (14) varies according to the direction of extension (X) according to a variation law, the variation law being continuous and comprising three pieces, a first piece in which the density is equal to a first density value, a second piece in which the density is equal to a second density value, the third piece connecting the first piece and the second piece according to a polynomial function, the minimum value of the density being in the third piece.

4. The laser of claim 3, wherein the first density value and the second density value are identical.

5. Laser according to claim 3 or 4, in which the polynomial function has a parabolic form.

6. Laser according to any one of claims 3 to 5, in which the polynomial function is of order at least four, and is described by a formula of the type: Or : - x and y are the input and output variables of the polynomial function, - n is an integer greater than or equal to 2, and - Ai are constants.

7. Laser according to any one of claims 3 to 6, in which each orifice (24) is separated from each neighboring orifice (24) by a spacing, the spacings each having a dimension, measured in the direction of extent (X), which varies in the direction of extent (X) according to the variation law.

8. Laser according to any one of claims 3 to 6, in which the rib (14) has a width (W), the width (W) being a dimension measured in a direction (Y) perpendicular to the direction of extent (X), which varies according to the direction of extent (X) according to the variation law.

9. Laser according to any one of claims 1 to 8, in which the coated zone (34) is separated from the uncoated zone (32) by a gap extending mainly in a direction (Y) perpendicular to the direction of extension (X), the gap being, preferably, located in the direction of extension (X) at an orifice (24).

10. Laser according to claim 9, in which the dimension of the gap in the direction of extension (X) is between 20 nanometers and 40 nanometers.

11. A laser according to any one of claims 1 to 10, wherein the laser (10) further comprises a waveguide (44) defined in the substrate (12), extending along a guide direction (X'), the waveguide (44) being separated from the rib (14) by a non-zero distance in the direction (Z).

12. Laser according to any one of claims 1 to 11, in which the laser (10) comprises a plurality of successive ribs (14) and a waveguide (44) defined in the substrate (12), extending in a guiding direction, the waveguide (44) being arranged to guide the output wave of a rib to excite the following rib.

13. Component, in particular neuromorphic, comprising a laser (10) according to any one of claims 1 to 12.

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