Pulsed laser and associated component

Abstract

Pulsed Laser and Associated Component The present invention relates to a pulsed laser (10) comprising: - an insulating substrate (12), - a rib (14) extending over the substrate (12) along an extent direction (X), the rib (14) having a plurality of through orifices (24) aligned along the extent direction (X), the rib (14) comprising a set of layers partially coated with a coating layer, called a passivation layer, the coating layer being adapted to inhibit non-radiative recombination on the surface of the coated portions of the layers and covering the layers only over a portion, the rib (14) thus comprising an uncoated area (32) and a coated area (34), the rib (14) forming a resonant cavity for at least one electromagnetic wave in a single mode, - an excitation element (16) adapted to excite only the coated area (34) of the rib (14). Figure for the abstract: figure 1

Description

Title of the invention: Pulsed laser and associated component

[0001] The present invention relates to a pulsed laser, as well as to an optical component comprising such a laser.

[0002] The development of the internet and connected sensors leads to the acquisition of considerable quantities 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.

[0003] 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" literally meaning central processing unit while a GPU is a graphics processor, the acronym GPU coming from the English term "Graphie Processing Unit" literally meaning graphics processing unit.

[0004] 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 numerous tasks such as automatic data classification and pattern recognition.

[0005] 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 comprises 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.

[0006] By definition, a deep neural network is a network comprising more than three layers of neurons and a large number of neurons per layer.

[0007] For an implementation in a CPU or a GPU, a Von Neumann funnel problem (also called Von Neumann bottleneck according to its English name) appears because the implementation of a deep neural network involves using both the memory(ies) and the processor while the latter elements are spatially separated. This results in congestion of the communication bus between the memory(ies) and the processor.

[0008] 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.

[0009] Three architectural proposals are the subject of specific studies.

[0010] The first proposal is to use a CMOS type technology. It is understood by the acronym "CMOS", Complementary Metal Oxide Semiconductor (acronym coming from the English expression "Complementary Metal-Oxide-Semiconductor"). The acronym CMOS designates both a manufacturing process and a component obtained by such a manufacturing process. In such an architecture, neurons and synapses are CMOS components.

[0011] 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 stores information efficiently because the value of its electrical resistance changes, permanently, when a current is applied.

[0012] Finally, according to a third proposal, we seek to create optical neuron networks and optical synapses.

[0013] For this last proposal, it is appropriate to have for the realization of the neurons an optical component capable of generating pulses whose frequency depends on the level of the excitation in an at least quasi-continuous manner.

[0014] For this purpose, there are laser diodes capable of emitting pulses depending on an excitation level. The term "neuron laser" is often used to designate such laser diodes.

[0015] An example of the embodiment of a neuron laser is notably described 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.

[0016] 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.

[0017] There is therefore a need for a pulsed laser capable of generating im pulses whose frequency depends on the level of excitation 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 the requirements of energy efficiency.

[0018] For this purpose, the description describes a pulsed laser comprising:

[0019] - an insulating substrate,

[0020] - a rib extending on the substrate in a direction of extent, the rib having a plurality of through-holes aligned with the direction of extension,

[0021] the rib comprising a set of layers stacked in a stacking direction orthogonal to the direction of extension (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 thus comprising an uncoated zone and a coated zone,

[0022] the rib forming a resonant cavity for at least one electromagnetic wave, the cavity being capable of making a single mode resonate,

[0023] - an excitation element of the coated area of ​​the rib, the excitation element being suitable for exciting only the coated area of ​​the rib.

[0024] According to particular embodiments, the control method has one or more of the following characteristics, taken in isolation or in all technically possible combinations:

[0025] - a length is defined for each zone, the length being the dimension according to the direction of extent and the variation in 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 other modes, for example the length being the dimension along the direction of extent and the variation in density of orifices in the rib are chosen so that the rib exhibits a resonance mode having a quality factor strictly greater than 104 and that the quality factors of all other embodiments are less than or equal to 103.

[0026] - the density of orifices in the rib varies according to the direction of extension according to a law of variation,

[0027] 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.

[0028] - the first density value and the second density value are identical.

[0029] - the polynomial function has a parabolic form.

[0030] - the polynomial function is of order at least four, and is described by a formula of the type: |,w" y =

[0032] where:

[0033] - x and y are the input and output variables of the polynomial function,

[0034] - n is an integer greater than or equal to 2, and

[0035] - Ai are constants.

[0036] - each orifice is separated from each neighboring orifice by a gap, the spacings each having a dimension, measured in the direction of extent, which varies in the direction of extent according to the law of variation.

[0037] - the rib has a width, the width being a dimension measured according to a direction perpendicular to the direction of extent, which varies according to the direction of extent according to the law of variation.

[0038] - the coated area is separated from the uncoated area by a gap extending principally principally in a direction perpendicular to the direction of extension, the gap being, preferably, located in the direction of extension at the level of an orifice.

[0039] - the dimension of the gap according to the direction of extension is between 20 na nometers and 40 nanometers.

[0040] - 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.

[0041] - the laser comprises a plurality of successive ribs and a defined waveguide in the substrate, extending in a guiding direction, the waveguide being arranged to guide the output wave of one rib to excite the next rib.

[0042] The description also relates to a component, in particular neuromorphic, comprising a laser as previously described.

[0043] In the present description, the expression “suitable for” means indifferently “adapted for”, “adapted to” or “configured for”.

[0044] Furthermore, in all that follows, by the expression "between two values", is meant a framework in the broad sense, that is to say including the values ​​of the limits.

[0045] 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:

[0046] - [Fig.l] [Fig.l] is a schematic view of an example of a laser according to the invention,

[0047] - [Fig.2] [Fig.2] is a side sectional view of a portion of the laser of [Fig.l],

[0048] - [Fig.3] [Fig.3] is a schematic representation of a part of another example of laser,

[0049] - [Fig.4] [Fig.4] is a schematic representation of a part of yet another example of laser,

[0050] - [Fig.5][Fig.6] Figures 5 and 6 are schematic representations of a part of a laser variant, and

[0051] - [[Fig.7] [Fig.7] is a schematic representation of a part of yet another laser embodiment.

[0052] A laser 10 is shown in [Fig. 1].

[0053] The term "laser" means a photonic system which produces spatially and temporally coherent light radiation based on the laser effect (acronym from the English light amplification by stimulated emission of radiation).

[0054] 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.

[0055] 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.

[0056] This desired operation is independent of the nature of the excitation (optical or electrical in particular).

[0057] Very schematically as in [Fig.l], the laser 10 comprises a substrate 12, a cavity-forming rib 14 and an excitation element 16.

[0058] The substrate 12 is a layer forming a plate on which the rib 14 rests.

[0059] 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.

[0060] The rib 14 is arranged to form an optical guide in which at least one electromagnetic wave propagates having frequencies from among a range of frequencies of interest.

[0061] According to the example described, the rib 14 is made of a material having a refractive index greater than 2.5.

[0062] The rib 14 constitutes a resonant cavity for the electromagnetic wave, that is to say a confined propagation medium for the electromagnetic wave.

[0063] The rib 14 extends mainly in a direction of extent X.

[0064] More precisely, the rib 14 comprises a central portion 20 extending between two end portions 22 as well as a plurality of orifices 24.

[0065] The central part 20 is a rectilinear part extending in the direction of extent X.

[0066] In this direction of extension, the rib 14 has a set of layers stacked according to a stacking direction Z orthogonal to the direction of extension X.

[0067] The orifices 24 are cylindrical perforations passing through the central part 20 of the rib 14.

[0068] 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.

[0069] The orifices 24 are aligned along the rib 14.

[0070] In the example of [Fig.l], each orifice 24 has a circular section and a constant diameter from one orifice 24 to the next.

[0071] Each orifice 24 extends along a central axis parallel to the stacking direction Z.

[0072] 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.

[0073] 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 that a periodic potential in a semiconductor crystal affects the movement of electrons by creating allowed and forbidden energy bands.

[0074] According to the example described, the set of layers is partially coated with a coating layer 30.

[0075] The coating layer 30 only covers the layers of the set of layers over a portion, the rib 14 thus comprising an uncoated area 32 and a coated area 34.

[0076] As shown schematically in [Fig.2], the coating layer 30 covers both the upper layer of the set of layers and the periphery 36 of the orifices 24.

[0077] 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.

[0078] 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.

[0079] Seen from above as in [Fig.l], zones 32 and 34 have a rectangular shape. tangular, the layers belonging to zones 32 and 34 not being visible.

[0080] The coating layer 30 has at all points a thickness less than or equal to 5 nm, preferably 1 nm.

[0081] 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.

[0082] Such a coating layer can be obtained by deposition carried out chemically or by plasma or by physical vapor deposition or by chemical vapor deposition or by atomic thin film deposition (ALD).

[0083] The chemical route consists, for example, of carrying out sulfurization of the surfaces of the different parts of the layers to be passivated.

[0084] 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.

[0085] The coating layer 30 can thus be described as a passivation layer 30.

[0086] Also, in the following, the uncoated zone 32 will be called the unpassivated zone 32 and the coated area 34 will be referred to as passivated area 34.

[0087] 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.

[0088] Therefore, the population of excited carriers is much lower in the unpassivated region 32.

[0089] Thus, the passivated zone 34 plays the role of a gain zone while the non-non-passivated zone 32 will play the role of a saturable absorber.

[0090] The excitation element 16 can be produced optically or electrically, in particular by a laser or electrical contacts positioned at predefined locations.

[0091] Assuming that the materials used are fixed, it is possible to envisage numerous geometric arrangements of the laser 10 shown schematically in [Fig.l], these arrangements depending on the geometric parameters which can be modified.

[0092] 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 III-V type semiconductor materials.

[0093] 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.

[0094] 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.).

[0095] In the following, a number of examples will be described for obtaining the desired operation with different geometric parameters.

[0096] For this, with reference to [Fig.3], geometric parameters that can be modified will be introduced.

[0097] One or more of these geometric parameters may 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.

[0098] Examples of geometric parameters are the dimensions of the central portion 20, in particular its length and its width.

[0099] 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.

[0100] To give an order of magnitude of dimension, the length Lc of central part 20 is less than or equal to 100 micrometers, in particular less than or equal to 50 micrometers.

[0101] The rib 14 also has a width W, measured in the transverse direction Y.

[0102] According to the example of [Fig.l], the width W is constant over the entire extent of the central part 20.

[0103] The width W is, for example, between 0.4 micrometers and 1.01 micrometers.

[0104] However, as shown in [Fig.3], the width may vary along the central portion 20.

[0105] It could also be envisaged to vary the dimensions and positions of the orifices, the corresponding parameters constituting such geometric parameters.

[0106] As for the shape, one could consider square, circular or oval shapes.

[0107] Thus, in the case of [Fig.l], the circular shape involves a single parameter which is the value of the radius while the oval shape involves several parameters.

[0108] In the following, it is assumed that the circular shape is chosen and that the shape is not a parameter used for optimization.

[0109] An arrangement parameter is now described.

[0110] 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.

[0111] Each orifice 24 of index n is separated from the following orifice of index n+1 by a spacing. The spacing separating two orifices 24 extends between the two points closer to the peripheries of the two orifices 24.

[0112] 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 an.

[0113] The dimension an varies from one spacing to another according to a variation law to be determined.

[0114] The variation law is a function of which one variable is the position xn of the orifices.

[0115] The position xn of an orifice 24 of index n is the distance separating the axis of the orifice 24 of index n of the axis of the first orifice 24 of index n = 0.

[0116] As other geometric parameters, in the example described, for each zone 32 and 34, a length L32 or L34 can be defined as being the dimension of the zone 32 or 34 according to the direction of extent X.

[0117] A parameter could therefore be the value of the ratio between the two lengths.

[0118] 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.

[0119] In this example, the optimization procedure therefore seeks to determine values ​​for the aforementioned parameters guaranteeing the desired operation for the laser 10.

[0120] In a first example, it is assumed that only the spacing and the position of the border between the two zones 32 and 34 are variable.

[0121] 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.

[0122] The optimization procedure is based on the calculation of the different resonance modes of the cavity formed by the rib 14.

[0123] Such a calculation is, for example, carried out by at least an approximate resolution of Maxwell's equations.

[0124] Such a resolution is notably carried out by simulation tools.

[0125] For each resonance mode, the frequency v and the lifetime ' are thus obtained.

[0126] It follows that, for each resonance mode, its factor can be determined of associated quality Q, this quality factor being given by the following formula:

[0127] Q = 2ttvt

[0128] The different parameters are then chosen so that the quality factor of a mode is strictly greater than 104 while the quality factors of all the other embodiments are less than or equal to 103.

[0129] 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 others. fashions.

[0130] 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.

[0131] To clearly illustrate what this optimization procedure leads to, a particular example is now described by particularizing the variation law.

[0132] The law of variation is piecewise continuous.

[0133] More precisely, according to the example described, the variation law comprises three pieces, namely a first piece M1 in which the dimension an is equal to a first dimension value, a second piece M2 in which the dimension an 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 an being in the third piece M3.

[0134] Preferably, the first dimension value and the second dimension value are identical.

[0135] In the following, the first dimension value and the second dimension value will be denoted amax.

[0136] The first and second pieces are therefore pieces in which the relation an = amax is verified.

[0137] Such a limitation to a maximum value at the ends makes it possible to weaken the resonances other than the fundamental mode.

[0138] For example, the polynomial function of the third piece M3 is a symmetrical polynomial function, of order at least equal to 2.

[0139] By the term "symmetric" it is understood that the odd order terms of the polynomial function are null.

[0140] Thus, a polynomial function for the third possible piece M3 is of the type:

[0141] an ~a(xn) - axn2 + fi

[0142] Where a and [3 are non-zero constants.

[0143] More generally, there comes a mathematical relationship of the type: 101441 y=r^'

[0145] where:

[0146] - x and y are the input and output variables of the polynomial function,

[0147] - n is an integer greater than or equal to 2, and

[0148] - A; are constants.

[0149] According to the proposed example, the polynomial function is a symmetric polynomial function of order 4.

[0150] According to the proposed example, the polynomial function for the third piece M3 is expressed in the form:

[0151] a„ -a{xn) -a^ + Ax„2 + Bx„4

[0152] Where: • a0 is the dimension of the gap separating the orifice 24 of index 0 from the orifice 24 of index 1, and • A and B are non-zero constants.

[0153] The values ​​of the constants A and B are chosen to obtain the emission by the laser 10 of a desired electromagnetic wave.

[0154] More precisely, the value of A is chosen so as to fix a value of a free spectral interval of the rib 14.

[0155] 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).

[0156] The values ​​of a0, A and B are, for example, obtained by a digital simulation of the operation of the laser 10.

[0157] For example, the value of a0 is between 300 nanometers and 600 nanometers, more particularly between 330 nanometers and 350 nanometers.

[0158] According to the example shown, the value of a0 is chosen to be equal to 340 nanometers.

[0159] For example, the value of A is chosen between 2 meters 1 and 3 meters *, more particu generally between 2.2 meters 1 and 2.4 meters *.

[0160] According to the example shown, the value of A is chosen to be equal to 2.3 meters *.

[0161] For example, the value of B is chosen between 0.5 x 107 meters 3 and 4 x 107 meters3.

[0162] According to the example shown, the value of B is chosen to be equal to 0.5 x 107 meters3.

[0163] 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%.

[0164] 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.

[0165] In particular, simulations with a value of L32 = 9 pm, L34 = 7 pm for a mode whose 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.

[0166] This shows that the laser 10 is a pulsed laser whose repetition frequency, or even the very emission of pulses, depends on the excitation.

[0167] More precisely, the emission of pulses depends on the integral of the received excitation signal. Thus, the emission will be all the faster as the signal level is high.

[0168] The laser 10 is thus a laser emitting pulses at an adjustable frequency.

[0169] The laser 10 which has just been described has a very small size, of the order of a few pm2. In this sense, laser 10 is a “nano-laser” since this laser is miniaturized.

[0170] Furthermore, the laser 10 consumes around 100 pW in operation, which corresponds to low energy consumption.

[0171] In addition, the laser 10 has a fast response, of the order of GHz.

[0172] The laser 10 can, furthermore, be integrated into a silicon photonic circuit.

[0173] In fact, the laser 10 is here a nano-hybrid structure whose laser cavity and zone active, in III-V material, are transferred to a silicon photonic circuit.

[0174] This makes the laser 10 particularly suitable for the realization of neurons in a physical implementation of a neural network.

[0175] More broadly, the laser 10 can advantageously be used in applications relating to communications, ultra-fast signal processing or analog computing.

[0176] Other embodiments of the laser 10 are conceivable and have advantages identical to those of the laser 10 described previously.

[0177] In the following, only the differences with the laser 10 of [Fig.l] are detailed, the elements not mentioned being considered as identical.

[0178] According to the example of [Fig.3], the spacing an is kept fixed but the width W varies according to the direction of extent X.

[0179] By way of illustration, the variation of the width W presents a variation law similar to those described previously for the spacing an.

[0180] According to a particular example, the width W is such that:

[0181] VF (x) = min (Wo + Ax„2 + Bx^, Wmax)

[0182] Where VF0 and are two constants.

[0183] It is possible, as a variant, to vary both the width W and the dimension an.

[0184] In each case, the density of holes in the rib varies according to the direction of extent 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.

[0185] This variation in density is obtained by varying one or more of the di- characteristic dimensions of the orifices 24 and of the rib 14.

[0186] Such spatial modulation makes it possible to obtain the existence of a single resonance mode in the cavity.

[0187] 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.

[0188] The function of this gap 40 is to ensure the electrical separation of the two zones 32 and 34.

[0189] The gap 40 has a thickness (dimension along the direction of extent X) less than or equal to 40 nm.

[0190] Preferably, the gap 40 has a thickness greater than or equal to 20 nm.

[0191] Due to its dimensions, the gap 40 constitutes a nano-groove.

[0192] Preferably, the gap 40 is located at an orifice.

[0193] As visible in [Fig.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.

[0194] Alternatively, it is possible to implant ions neutralizing the conductivity between the passivated 34 and non-passivated 32 zones on a zone corresponding to the gap (but wider, covering at least one period of the rib 14)

[0195] 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.

[0196] Figures 5 and 6 show yet another embodiment.

[0197] According to this embodiment, the laser 10 further comprises a waveguide 44 defined in the substrate, extending in a guiding direction.

[0198] 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.

[0199] The waveguide 44 is a silicon channel extending through the substrate 12, in a guiding direction X'.

[0200] According to another example, the waveguide 44 is made of silicon nitride.

[0201] More generally, the waveguide 44 is made of a transparent material whose index is higher than that of the substrate 12.

[0202] 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.

[0203] The waveguide 44 extends at a non-zero distance from the upper face 18 of the substrate 12 and from the rib 14.

[0204] The distance separating the waveguide 44 from the rib 14, measured in the transverse direction Y, may be constant or vary in the direction of extension X.

[0205] The distance separating the waveguide 44 from the rib 14 is sufficiently small so that a portion of the electromagnetic wave propagating in the rib is captured by the waveguide 44 in the form of an evanescent wave, through the insulating substrate 12.

[0206] This distance is typically between 100 nm and 200 nm if the waveguide 44 is made of silicon, but can be greater, 2 or even 3 micrometers if the material constituting the waveguide 44 has a lower refractive index.

[0207] The waveguide 44 is also capable of guiding the collected electromagnetic wave in the guiding direction X', away from the rib 14.

[0208] The waveguide 44 has a prismatic shape of rectangular section in a plane orthogonal to the guiding direction X'.

[0209] 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 to the transverse direction Y.

[0210] The coupling angle α is chosen so as to improve coupling between the rib 14 and the waveguide 44, i.e. so as to optimize the transmission of evanescent waves through the substrate 12, from the rib 14 to the waveguide 44.

[0211] The coupling angle a is, for example, between -15° and 15°.

[0212] According to a variant illustrated by [Fig.7], the laser 10 comprises a plurality of ribs 14 as well as a waveguide 44 similar to that of figures 5 and 6.

[0213] The waveguide 44 of [Fig.7] is arranged to guide the output wave of a rib 14 to excite the next rib 14.

[0214] 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.

[0215] In operation, the first rib 14 generates a signal at a first optical frequency vo.

[0216] This signal is transported by the waveguide 44 to the second rib 14.

[0217] The second rib 14 receives the signal at the first optical frequency vo which excites it and emits a signal at a second frequency vi.

[0218] This signal is transported by the waveguide 44 to the third rib 14.

[0219] The third rib 14 receives the signal at the second optical frequency vi which comes excite it and emit a signal at a third frequency v3.

[0220] This thus makes it possible to create a network of cavities.

[0221] The described embodiments can be combined according to 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 wave electromagnetic, the cavity being capable of making a single mode resonate,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. The laser of claim 1, wherein 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 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 104 and the quality factors of all other embodiments are less than or equal to 103.

3. A laser according to claim 1 or 2, wherein the density of orifices in the rib (14) varies along the direction of extent (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 value of density, 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 the same.

5. A laser according to claim 3 or 4, wherein the polynomial function has a parabolic shape.

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: y^L^x^ where: - x and y are the input and output variables of the polynomial function, - n is an integer greater than or equal to 2, and - A; 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. A laser according to any one of claims 3 to 6, wherein 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 along the direction of extent (X) according to the variation law.

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

10. Laser according to claim 9, wherein 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 in a guiding direction (X'), the waveguide (44) being separated from the rib (14) by a non-zero distance in the direction (Z).

12. A laser according to any one of claims 1 to 11, wherein 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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