Integrated high-power laser emitting device

Abstract

Laser emission device (1, 1'), integrated in a substrate (2), comprising: a main waveguide (10), arranged in the substrate, and extending from a main reflector (15); several secondary waveguides (20), optically connected to the main waveguide (10), extending between a coupling end (13), optically connected to the main waveguide (10), and a secondary reflector (25); the device being characterized in that each secondary waveguide (20) comprises an amplifying medium (24), connected to a laser pumping system (26) and arranged between the coupling end (23) and the secondary reflector (25) of said secondary waveguide so that the device forms as many Fabry Pérot cavities as secondary waveguides; the device comprising an extractor (15, 25), for extracting the light from the device, at the resonance wavelength. Figure 2.

Description

Title of the invention: High-power integrated laser emitting device Technical field

[0001] The technical field of the invention is integrated optics and more precisely the design of a high-power laser emission circuit intended to be used, in a non-limiting manner, in LIDAR or telecoms type applications, or other photonic applications. PREVIOUS ART

[0002] In the field of optics, we are moving towards technologies that allow large-scale manufacturing and assembly. By integrating optical components on a single chip, it is possible to reduce the size and cost of systems while increasing their performance.

[0003] In the field of LIDARS, for example, the use of wavelength-modulated laser sources is common. According to the principles of a frequency-modulated continuous wave (FMCW), it is possible to perform a continuous modulation of the emission wavelength, for example in a triangular shape, as shown in [Fig.l]. A part of an emitted laser beam is sampled and directed towards a photodetector. The laser beam reflected by a target is also directed towards the photodetector. Since the sampled beam and the reflected beam are coherent, their interference can be detected by the photodetector and results in a frequency difference directly proportional to the distance from the target. The operation of such devices is for example described in the publication by C. Poulton "Coherent solid-state LIDAR with Silicon photonic optical phased arrays".

[0004] The use of wavelength-modulated lasers can also concern the field of optical telecommunications.

[0005] Whether for LIDAR or telecom applications, compact systems with high transmission power, for example greater than 100 mW, are sought. Until now, laser sources integrated on a chip do not allow such power to be obtained. Hybrid systems allow an increase in transmission power, through a coherent combination of beams emitted by different laser sources. The publications Zhu.Y “Loss induced coherent combining in InP-Si3N4 hybrid platform”, Sci. Rep., vol.8, n° 1, Art. N°l, Jan, 2018, as well as Zeng S. “Watt-level beam combined diode laser Systems in a chip scale hybrid photonic platform”, Optics Express, Vol. 30, N° 13 / 20, June 2022, describe hybrid architectures, in which several laser sources are reported against a photonic chip. The beams emitted by each source are combined in the substrate to obtain a high-power beam. However, such architectures have the disadvantage of high manufacturing costs, due to the assembly that must be established between each laser source and the substrate. Another difficulty is the alignment between each laser source and the substrate, which can be tricky and generate losses.

[0006] The invention described below makes it possible to obtain a laser source integrated into a monolithic substrate. Depending on the arrangements, either a high-power laser source or several laser sources are obtained. Preferably, the laser source is continuously wavelength modulated, which allows use in Lidars. Presentation of the invention

[0007] An object of the invention is a laser emission device, integrated in a substrate, comprising: - a main waveguide, provided in the substrate, and extending from a main reflector, the main reflector being configured to reflect light in a reflection spectral band; - several secondary waveguides, optically connected to the main waveguide, each secondary waveguide extending between a coupling end, optically connected to the main waveguide, and a secondary reflector, each secondary reflector being configured to reflect light in the reflection spectral band; - the device being characterized in that each secondary waveguide is optically coupled to an amplifying medium, connected to a laser pumping system, the amplifying medium being suitable for laser emission under the effect of pumping exerted by the laser pumping system, the amplifying medium being arranged between the coupling end and the secondary reflector of said secondary waveguide - so that the device forms as many Fabry-Pérot cavities as secondary waveguides, each Fabry-Pérot cavity being configured to allow multiple reflections of light at the same resonance wavelength, in the reflection spectral band, between the main reflector and each secondary reflector; - the device comprising an extractor, for extracting light from the device, at the resonance wavelength, said resonance wavelength forming an emission wavelength of the device.

[0008] According to one embodiment, the main reflector or each secondary reflector is adjustable, so as to modulate the reflection spectral band.

[0009] According to one possibility, the reflection spectral band of the main reflector is adjustable, the main reflector being a Bragg mirror, coupled to a modulator configured to modulate a refractive index in said Bragg mirror. Each secondary reflector can reflect light in a fixed secondary reflection spectral band wider than the reflection spectral band of the main reflector, and containing the latter.

[0010] According to one possibility, the reflection spectral band of each secondary reflector is adjustable, each secondary reflector being a Bragg mirror, coupled to a modulator configured to modulate a refractive index in said Bragg mirror. The main reflector can reflect light in a fixed reflection spectral band and wider than the reflection spectral band of each secondary reflector, and containing the latter.

[0011] Preferably, at least one secondary waveguide comprises a secondary phase modulator, configured to modulate a refractive index along a portion of said secondary waveguide, the secondary phase modulator being disposed between the coupling end of said secondary waveguide and the secondary reflector of said secondary waveguide, so as to modulate an optical path in said secondary waveguide.

[0012] Preferably, each secondary waveguide comprises a secondary phase modulator, configured to modulate a refractive index along a portion of said secondary waveguide, the secondary phase modulator being disposed between the coupling end of said secondary waveguide and the secondary reflector of said secondary waveguide, so as to modulate an optical path in each secondary waveguide.

[0013] The main waveguide may comprise a main phase modulator, configured to modulate a refractive index along a portion of the main waveguide, the main phase modulator being disposed between each secondary waveguide and the main reflector, so as to modulate the resonance wavelength of each Fabry-Pérot cavity of the device.

[0014] According to one possibility: - the main reflector reflects more than 90% of the light, in the reflection spectral band; - each secondary reflector transmits at least 20% of the light, in the reflection spectral band, so that the secondary reflector forms the extractor of the device.

[0015] According to one possibility: - each secondary reflector reflects more than 90% of the light, in the reflection spectral band; - the main reflector transmits at least 20% in the reflection spectral band, so that the main reflector forms the extractor of the device.

[0016] The main waveguide may be formed by a first material, and surrounded by a first auxiliary material, the refractive index of which is lower than the refractive index of the first material.

[0017] Each secondary waveguide may be formed by a second material, and surrounded by a second auxiliary material, the refractive index of which is lower than the refractive index of the second material.

[0018] According to one possibility: - the first material is identical to the second material; - the first auxiliary material is identical to the second auxiliary material.

[0019] According to one possibility: - the first material and the second material are Si; - the first auxiliary material to the second auxiliary material are SiO2.

[0020] According to one possibility: - the first material is SiN; - the second material is Si; - the first auxiliary material is identical to the second auxiliary material.

[0021] Preferably, the main waveguide and at least one secondary waveguide, or each secondary waveguide, are formed in the same substrate, each amplifying medium being transferred onto said substrate.

[0022] The invention will be better understood upon reading the description of the exemplary embodiments presented in the remainder of the description, in conjunction with the figures listed below. FIGURES

[0023] [Fig. 1] shows an example of continuous wavelength modulation. The ordinate axis corresponds to the wavelength and the abscissa axis corresponds to time.

[0024] [Fig.2] shows a first embodiment.

[0025] Figures 3A and 3B schematically represent a substrate section at the level of the active material.

[0026] [Fig.4A] schematically represents a narrow and adjustable spectral reflection band of a main reflector, included in the broad spectral reflection band of a secondary reflector. The light energy propagated inside the Fabry-Pérot cavity formed by the main reflector and the secondary reflector has also been represented.

[0027] [Fig.4B] shows a configuration in which the reflection spectral band of the secondary reflector is coincident with a resonance wavelength of the Fabry-Pérot cavity.

[0028] [Fig.4C] shows a configuration in which, compared to [Fig.4B], the reflection spectral band of the secondary reflector is modified.

[0029] [Fig.4D] shows a configuration in which, compared to [Fig.4C], the resonance wavelength of the Fabry-Pérot cavity is modified.

[0030] [Fig.5] shows a diagram of a second embodiment. PRESENTATION OF SPECIAL METHODS OF IMPLEMENTATION

[0031] [Fig.2] shows a diagram of a first embodiment of a laser emission device 1 according to the invention. The device 1 is formed in a monolithic substrate 2. [Fig.2] represents a cross-sectional view of the device, in the plane of the substrate. The substrate 2 is for example of the SOI (Silicon on Insulator) type. SOI is a well-known substrate in microelectronics, but it is also widely used in the manufacture of integrated optical circuits. Silicon is transparent to telecom wavelengths (1.3 pm - 1.5 pm), and the high index contrast with its oxide (nSi = 3.51 - nSiO2 = 1.45 or An = nSi- nSiO2 = 2) makes it suitable for compact passive functions: mirrors, waveguides, resonant cavities. In addition, current manufacturing processes are mastered and allow the production of large substrates.

[0032] Other types of substrates can be used, for example SiNOI (acronym for Silicon Nitride on Insulator) or LNOI (acronym for Lithium Niobate on Insulator) type.

[0033] The device comprises a main waveguide 10, arranged in the substrate, and extending from a main reflector 15, configured to reflect a wavelength of interest. In the examples described, the main reflector 15 is a Bragg mirror, called the main Bragg mirror. Other types of reflectors, for example Sagnac loops, are conceivable. The main waveguide 10 is formed from a first material 11, in this case Si, around which extends a first auxiliary material 12, in this case SiO2. Other variants are described below.

[0034] The main waveguide 10 is formed by conventional photolithography / etching techniques. It is typically produced by etching the surface silicon layer of an SOI wafer (plate), the latter being in contact with an oxide layer 3. The Si waveguide resulting from the etching is then covered with an upper layer of a lower index material 12, for example SiO2. The upper layer can be thinned and planarized. The thickness of the upper layer can be reduced to 100 nm. The channel is arranged on the SiO2 layer 3. An example of channel geometry is described below, in connection with FIGS. 3A and 3B. The height of the waveguide 10 is typically between 220 and 500 nm, and its width can vary between 100 nm and 5 pm.

[0035] In a manner known per se, the main Bragg mirror 15 is formed from a periodic alternation of two materials having different refractive indices respectively. The periodic variation of the index generates a set of reflections which add up when they are in phase. In this example, the main Bragg mirror 15 is formed by partially etching the silicon and then depositing SiO2. The periodicity of the etched areas determines a spectral reflection band, at which the Bragg mirror reflects light, the period being of the order of a few hundred nanometers. The number of periods is typically several tens to several hundred or even thousands.

[0036] In this example: - the main Bragg mirror 15 is a mirror having a narrow reflection spectral band, the width at half-maximum of the reflection spectral band being for example less than 1 nm. The reflection spectral band is centered on the wavelength of interest - the main Bragg mirror 15 is a total mirror, in the sense that it reflects almost all of the light in the reflection spectral band. By almost all, we mean more than 90%, or even more than 95%, or even more than 99%. - the main Bragg mirror 15 is adjustable, the reflection spectral band being variable. The variation of the reflection spectral band is obtained by a modulation of the refractive indices, under the effect of a modulator 17, at the level of the materials forming the Bragg mirror. Such modulation can be obtained by a local variation of the temperature, the modulator of the Bragg mirror 17 then being a heating resistor. The modulation can also be obtained by a local injection of charges at the level of the Bragg mirror. Indeed, the refractive index of a semiconductor material depends on the charge density. In [Fig.2], the modulator 17 of the main Bragg mirror is materialized by an arrow.

[0037] The device 1 comprises several secondary waveguides 20, the structure of which is preferably, but not necessarily, identical to that of the main waveguide 10: same material, same dimensions. Generally, each secondary waveguide 20 is formed from a second material 21, in this case Si, around which extends a second auxiliary material 22, in this case SiO2.

[0038] In this example, the device 1 comprises four secondary waveguides 20. The number of secondary waveguides can be between 2 and 10, or even several dozen.

[0039] Each secondary waveguide 20 extends between a coupling end 23, intended to be optically connected to the main waveguide 10, and a secondary reflector 25. In this example, the secondary reflector is a Bragg mirror, called a secondary Bragg mirror. Preferably, the secondary Bragg mirrors are identical to each other. They are preferably formed with the same materials as the main Bragg mirror 15, so as to reflect the light in the length wave of interest defined by the main Bragg mirror 15. Preferably, the reflection spectral band of each secondary Bragg mirror 25 is identical to, or wider than, that of the main reflector, and includes the reflection spectral band of the main reflector 15. In this example: - each secondary Bragg mirror 25 is a mirror having a wide reflection spectral band, the width at half-height of the reflection spectral band being for example greater than or equal to 10 nm. - each secondary Bragg mirror 25 is a partial mirror, in the sense that it only partially reflects the light in the reflection spectral band. By partially, we mean less than 80%, or even less than 50%, for example 40%. The unreflected light is transmitted to a photonic circuit. For example, each secondary Bragg mirror 25 is connected to one of the inputs of an optical phased array (OPA) which, in the context of a LiDAR system, allows the beam to be scanned in space. The secondary Bragg mirrors form the light extractor of the device.

[0040] The length of each Bragg mirror, which can be between a few hundred microns and several millimeters.

[0041] It goes without saying that the reflection spectral band of the main Bragg mirror extends into the reflection spectral band of each secondary Bragg mirror. This produces reflections of at least one wavelength of interest which corresponds to the intersection of the reflection spectral band of the main Bragg mirror and each secondary Bragg mirror.

[0042] Between the main waveguide 10 and each secondary waveguide 20, transmission waveguides 13 extend, the function of which is to provide optical coupling between the main waveguide 15 and each secondary waveguide 25. A coupler is used at each coupling end 23 to connect / combine the beams from the different secondary guides 20 to the main waveguide 10. The coupler may be, for example, a directional coupler or a multimode interferometer (MMI - MultiMode inteferometer).

[0043] Each secondary waveguide 20 forms, with the main waveguide 10, a Fabry-Pérot cavity, allowing successive reflections of the light in the wavelength of interest. The wavelength of interest must also correspond to a resonance wavelength λr of each Fabry-Pérot cavity, as described below. In this example, the wavelength of interest λ' is defined by the Bragg mirror having the narrowest reflection spectral band. This is the main Bragg mirror 15. It can be seen that the device allows the formation of as many Fabry-Pérot cavities as there are secondary waveguides 20. Each cavity Fabry-Pérot is formed by the main waveguide 10 and a secondary waveguide 20.

[0044] An important aspect of the invention is that each secondary waveguide is optically coupled to an amplification medium 24. The amplification medium 24, or active medium, is a medium that emits laser light under the effect of pumping. It may, for example, be layers of III-V materials formed opposite the secondary waveguide 20.

[0045] The light generated by the amplification medium 24 is injected into the secondary waveguide 20 to which it is optically coupled. The amplification medium 24 may be separated from the secondary waveguide 20 by a low-index bonding layer. It is known that assemblies of IILV materials of the AlGaAs / GaAs type allow emission in the 600-800 nm range, that assemblies of IILV InGaAsP / InP materials allow emission in the 1300 / 1500 nm range.

[0046] The amplification layer 24 is produced by transferring, onto the substrate, an IILV laser epitaxy, allowing the formation of a few microns of active layers. This stack is then etched to form a waveguide above the photonic guide 20, itself also being optimized to facilitate the transfer of light to / from the IILV guide. The transfer of layers of IILV materials onto a Si waveguide formed on an SOI type substrate is for example described in Roelkens G. “IILV / silicon photonics for on-chip and inter-chip optical interconnect”, Laser Photonics Rev. 4 No. 6, 751-779 (2010).

[0047] Figures 3A and 3B schematically show cross-sectional views of the substrate 2 respectively at the level of the main waveguide 10 and at the level of the secondary waveguide 20. [Fig.3B] schematically shows a cross-sectional view of an amplification medium 24. The amplification medium is configured to be coupled to a pumping system 26. The latter is actuated to obtain a population inversion of the charge carriers in the active material. This may be optical pumping, in which case the inversion results from an absorption of a pump laser beam. Preferably, it may be electrical pumping, allowing an injection of charge carriers via a current into a pin-diode whose i (intrinsic) zone is formed by the active material. Electrical pumping is simpler to implement.

[0048] The amplifying medium 24 is arranged between the coupling end 23 and the secondary Bragg mirror 25. This allows an emission of laser light, at the wavelength of interest, which is then amplified by the Fabry Pérot cavity, because each amplifying medium 24 is arranged between two Bragg mirrors: the main Bragg mirror 15 and a secondary Bragg mirror 25.

[0049] The emission device 1 allows an emission of a high power and spatially distributed laser light, the emission resulting from the transmission of each secondary Bragg mirror 25. In the example shown, emission waveguides 29 allow the emission of light from the device. As previously described, the reflection by the secondary Bragg mirrors 25 is partial. The part of the light not reflected is transmitted. Each secondary Bragg mirror 25 is arranged between a secondary waveguide 20 and at least one emission waveguide 29. The light waves respectively emitted by each secondary waveguide 20 are coherent, at the wavelength of interest.

[0050] The use of a modulator of the main Bragg mirror 17 makes it possible to control a variation of the emission wavelength of the device. A control unit 30 makes it possible to control the modulator 17, so as to control the spectral band of reflection of the main mirror 15.

[0051] Each Fabry-Pérot cavity is defined by resonance wavelengths, defined by the relation:

[0052]

[0053] Where - Àr is the resonance wavelength; - L is the length of the Fabry-Perot cavity; - n is the effective index of the waveguide formed by the main waveguide 10, the transition guide 13 and the secondary waveguide 20: - m is an integer designating a resonance mode.

[0054] In order to obtain a continuous variation of the emission wavelength of the device, it is advantageous for the device to comprise, in each Fabry-Pérot cavity, at least one modulator, called a phase modulator, so as to modulate the resonance wavelength λr so that the latter corresponds to the wavelength of interest reflected by the Bragg mirrors.

[0055] In each Fabry-Pérot cavity, at least one of the reflectors is configured to address only one resonance peak.

[0056] Figures 4A to 4D illustrate a variation of the emission wavelength of the device. In [Fig.4A], the reflection spectral band of the main Bragg mirror 15 and the reflection spectral band of each secondary Bragg mirror 25 are represented. It is observed that the main Bragg mirror 15 reflects about 100% of the light, according to a narrow spectral band, while each secondary Bragg mirror 25 reflects about 50% of the light, according to a wide spectral band, including the narrow spectral band of the main Bragg mirror 15. In [Fig.4A], the left ordinate axis is the reflectance (%), and the abscissa axis is the wavelength (nm). An intensity of the light propagating in the Fabry-Pérot cavity formed by the main Bragg mirror 15 and by the secondary Bragg mirror 25 in different wavelengths has also been represented. (right y-axis arbitrary unit).

[0057] In Figure 4B, the spectral band of the main Bragg mirror 15 is represented, centered on a wavelength of interest 4, close to 1550 nm. Also represented, on the curve referenced FP, are resonance wavelengths λr of each Fabry-Pérot cavity. In the example of Figure 4B, the wavelength of interest 4 corresponds to a resonance wavelength λr and to the emission wavelength of the device. In [Fig.4B], the left ordinate axis is the reflectance (%), and the abscissa axis is the wavelength (m)

[0058] In Figure 4C, a shift in the spectral band of the main Bragg mirror 15 is shown. The emission wavelength of the device corresponds to a resonance wavelength 4r forming part of the reflection spectral band of the Bragg mirror, i.e. 1555 nm. This wavelength corresponds to the resonance wavelength of the Fabry-Pérot cavity included in the reflection spectral band. A discrete variation in the emission wavelength is then observed, with a jump from approximately 1548 nm ([Fig.4B]) to 1555 nm ([Fig.4C]). This makes it possible to modify the emission wavelength of the device, according to discrete values. The emission wavelength of the device then corresponds to a resonance wavelength present in the reflection spectral band of the main Bragg mirror. In [Fig.4C], the left y-axis is reflectance (%), and the x-axis is wavelength (m).The dotted lines represent the maxima of the reflection spectral bands of the main Bragg mirror before and after the shift respectively.

[0059] In order to obtain a continuous variation of the emission wavelength of the device, it is advantageous to accompany the variation of the reflection spectral band of the Bragg mirror 15 by a progressive variation of resonance wavelengths 4,- of the Fabry Perot cavity, as shown in FIG. 4D. This allows a resonance wavelength 4f to always correspond to a maximum of the reflection spectral band of the Bragg mirror 15.

[0060] The variation of the resonance wavelength λr of each Fabry Perot cavity of the device can be obtained by arranging a modulator, called the main phase modulator 18, at the main waveguide 10. The main phase modulator 18 is configured to vary the refractive index of the main waveguide 10. The variation of the refractive index can be obtained by localized heating, or by charge injection. The main phase modulator 18 can extend over a length of between a few hundred microns and a few millimeters.

[0061] For a silicon guide, it is estimated that the spectral shift can reach 0.1 nm per K. Thus, by modifying the temperature by 30°C, a spectral shift of 3 nm can be covered.

[0062] Secondary phase modulators 28 may be arranged in each secondary waveguide. Their function is to equalize the optical paths in each secondary waveguide 20. Note that it is also possible to directly modulate the current (electrical pump signal) of each amplifying medium (24), which produces a load variation in the amplifier, and therefore a modification of the optical path. The individual adjustment makes it possible to take into account variabilities resulting from device manufacturing. The arrangement of secondary phase modulators 28 in each secondary waveguide allows individual adjustment of each Fabry Pérot cavity of the device, so that all the cavities have, at all times, the same resonance wavelength λr.

[0063] Alternatively, the device shown diagrammatically in [Fig. 2] may be such that the main mirror 15 is fixed, and has a wide spectral reflection band, while each secondary mirror 25 is variable, and has a narrow spectral reflection band. However, such a configuration has the disadvantage of having to simultaneously control several secondary mirrors 25. The configuration shown in [Fig. 2] has the advantage of only having to control a single Bragg mirror, in this case the Bragg mirror 15, simultaneously with the control of the variation of the resonance wavelength of each Fabry Pérot cavity, using the main modulator 18 and / or the secondary modulators 28.

[0064] The device comprises a photodiode 10', arranged at the output of the main mirror 10, and detecting light leaks transmitted by the latter. When the optical paths of the secondary waveguides 20 are equal, each Fabry-Pérot cavity of the device allows the emission of phase-locked lasers, which leads to a significant increase in the laser power. This increase can be detected by the photodiode 10', reflecting the proper functioning of the device. The equalization of the optical path of each Fabry-Pérot cavity can be carried out sequentially, by adjusting each modulator and each amplifying medium one by one, to maximize the power collected at the level of the photodiode 10'.

[0065] The device described in connection with [Fig.2] is intended to obtain a spatially distributed coherent laser emission, at the level of each emission guide 29 connected to a secondary guide 20. An advantage is that the light guide transporting all the laser power is limited to the main light guide 10: the maximum power of the laser is transported over a relatively short length, typically over a few hundred microns.

[0066] The concentration of a high power density in a single Si waveguide can lead to absorption of the beam by TPA (Two Photon Absorption) effect. This can lead to a limitation of the optical power emitted by the device. Distributing the beam according to different secondary waveguides 20 makes it possible to reduce the impact of this type of absorption.

[0067] According to one possibility, the main waveguide 10, which concentrates the laser power, can be formed from a material less sensitive to TPA-type absorption phenomena, and more suitable for transporting high light power. Thus, the first material 11, forming the main waveguide, may be SiN, which does not exhibit TPA at the wavelengths of interest.

[0068] The device described in connection with [Fig.2] makes it possible to increase the laser power, while multiplying the emission points. It can be used in LIDAR type systems, in order to increase their range.

[0069] According to another possibility, shown in [Fig. 5], the invention can be implemented to concentrate coherent laser waves, so as to produce a high power beam. In [Fig. 5], the components, not commented on below, are identical to those described in connection with [Fig. 2], and have the same function.

[0070] A notable difference compared to the device shown in [Fig.2] is that each secondary reflector 25 is totally reflective (reflection coefficient greater than 90%, or even close to 100%), while the main reflector 15 is partially reflective, the reflection coefficient being less than 80%, or even 50%. Thus, the emission of light is carried out by an emission waveguide 19, connected to the main waveguide 10. The main reflector 15 has a light extractor function. The main reflector 15 extends between the main waveguide 10 and the emission waveguide 19. The emission of light is carried out from the light transmitted by the main Bragg mirror. A coupler 19' makes it possible to direct a small percentage of light, for example 1%, towards the photodiode 10'. The latter is used to track the laser power emitted by the device.It allows to verify that the phase locking of the different lasers has been obtained.

[0071] Regardless of the embodiment, the device can be used to emit a high-power laser beam, without necessarily varying the emission wavelength over time. In this case, it is not necessary for at least one reflector, in this case the main reflector, to be modulatable. Similarly, it is not necessary to modulate the resonance frequency of the Fabry-Pérot cavities. The main modulator 18 is not necessary. The use of the secondary modulators 28 remains preferable, for the purpose of adjusting the optical paths in each secondary waveguide 20. The device can be used for photonic calculation type applications, in which mathematical operations are performed by forming destructive or constructive interference between several coherent laser beams. Constructive interference can correspond to an addition. Destructive interference corresponds to a subtraction.

Claims

Claims

1. A laser emission device (1, 1'), integrated in a substrate (2), comprising: - a main waveguide (10), arranged in the substrate, and extending from a main reflector (15), the main reflector being configured to reflect light in a reflection spectral band; - several secondary waveguides (20), optically connected to the main waveguide (10), each secondary waveguide extending between a coupling end (13), optically connected to the main waveguide (10), and a secondary reflector (25), each secondary reflector being configured to reflect light in the reflection spectral band;- the device being characterized in that each secondary waveguide (20) is optically coupled to an amplifying medium (24), connected to a laser pumping system (26), the amplifying medium being suitable for laser emission under the effect of pumping exerted by the laser pumping system, the amplifying medium being arranged between the coupling end (23) and the secondary reflector (25) of said secondary waveguide - so that the device forms as many Fabry-Pérot cavities as secondary waveguides, each Fabry-Pérot cavity being configured to allow multiple reflections of light at the same resonance wavelength, in the reflection spectral band, between the main reflector and each secondary reflector;- the device comprising an extractor (15, 25), for extracting light from the device, at the resonance wavelength, said resonance wavelength forming an emission wavelength of the device.;

2. Device according to claim 1, in which the main reflector or each secondary reflector is adjustable, so as to modulate the spectral band of reflection.

3. A device according to claim 2, wherein the reflection spectral band of the main reflector is adjustable, the main reflector being a Bragg mirror, coupled to a modulator (17) configured to modulate a refractive index in said Bragg mirror.

4. A device according to claim 3, wherein the secondary reflector reflects light in a fixed secondary reflection spectral band wider than the reflection spectral band of the main reflector.

5. A device according to claim 4, wherein the reflection spectral band of each secondary reflector is adjustable, each secondary reflector being a Bragg mirror, coupled to a modulator (27) configured to modulate a refractive index in said Bragg mirror.

6. Device according to claim 5, in which the main reflector reflects light in a fixed spectral band of reflection and wider than the spectral band of reflection of each secondary reflector.

7. Device according to any one of the preceding claims, wherein at least one secondary waveguide (20) comprises a secondary phase modulator (28), configured to modulate a refractive index along a part of said secondary waveguide (25), the secondary phase modulator being arranged between the coupling end (23) of said secondary waveguide and the secondary reflector (25) of said secondary waveguide, so as to modulate an optical path in said secondary waveguide.

8. The device according to claim 7, wherein each secondary waveguide comprises a secondary phase modulator configured to modulate a refractive index along a part of said secondary waveguide, the secondary phase modulator being arranged between the coupling end of said secondary waveguide and the secondary reflector of said secondary waveguide so as to modulate an optical path in each secondary waveguide.

9. The device according to any one of the preceding claims, wherein the main waveguide comprises a main phase modulator (18) configured to modulate a refractive index along a part of the main waveguide, the main phase modulator being arranged between each secondary waveguide and the main reflector so as to modulate the resonance wavelength of each Fabry - Pérot cavity of the device.

10. Device according to any one of the preceding claims, in which - the main reflector (15) reflects more than 90% of the light, in the reflection spectral band; - each secondary reflector (25) transmits at least 20% of the light, in the reflection spectral band, so that the secondary reflector forms the extractor of the device.

11. Device according to any one of claims 1 to 9, wherein - each secondary reflector (25) reflects more than 90% of the light, in the reflection spectral band; - the main reflector transmits at least 20% in the reflection spectral band, so that the main reflector forms the extractor of the device.

12. Device according to any one of the preceding claims, in which the main waveguide is formed by a first material (11), and surrounded by a first auxiliary material (12, 3), the refractive index of which is lower than the refractive index of the first material.

13. Device according to any one of the preceding claims, in which each secondary waveguide (20) is formed by a second material (21), and surrounded by a second auxiliary material (22, 3), the refractive index of which is lower than the refractive index of the second material.

14. Device according to claims 12 and 13, wherein - the first material is identical to the second material; - the first auxiliary material is identical to the second auxiliary material.

15. Device according to claim 14 wherein - the first material and the second material are Si; - the first auxiliary material to the second auxiliary material are SiO2.

16. Device according to claims 12 and 13, wherein: - the first material is SiN; - the second material is Si; - the first auxiliary material is identical to the second auxiliary material.

17. Device according to any one of the preceding claims, in which the main waveguide and each secondary waveguide are formed in the same substrate (2), each amplifying medium (24) being transferred onto said substrate.

Images