EP3807960A1 - Locking of a laser on a resonator by means of an optical amplifier - Google Patents

Locking of a laser on a resonator by means of an optical amplifier

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Publication number
EP3807960A1
EP3807960A1 EP19729767.4A EP19729767A EP3807960A1 EP 3807960 A1 EP3807960 A1 EP 3807960A1 EP 19729767 A EP19729767 A EP 19729767A EP 3807960 A1 EP3807960 A1 EP 3807960A1
Authority
EP
European Patent Office
Prior art keywords
optical
resonator
laser source
laser
modulator
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP19729767.4A
Other languages
German (de)
French (fr)
Inventor
Frédéric Van Dijk
Peppino PRIMIANI
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Thales SA
Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
Original Assignee
Commissariat a lEnergie Atomique CEA
Thales SA
Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Commissariat a lEnergie Atomique CEA, Thales SA, Commissariat a lEnergie Atomique et aux Energies Alternatives CEA filed Critical Commissariat a lEnergie Atomique CEA
Publication of EP3807960A1 publication Critical patent/EP3807960A1/en
Pending legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
    • H01S3/10084—Frequency control by seeding
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/005—Optical devices external to the laser cavity, specially adapted for lasers, e.g. for homogenisation of the beam or for manipulating laser pulses, e.g. pulse shaping
    • H01S3/0078—Frequency filtering
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/005—Optical devices external to the laser cavity, specially adapted for lasers, e.g. for homogenisation of the beam or for manipulating laser pulses, e.g. pulse shaping
    • H01S3/0085—Modulating the output, i.e. the laser beam is modulated outside the laser cavity
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
    • H01S3/06—Construction or shape of active medium
    • H01S3/063—Waveguide lasers, i.e. whereby the dimensions of the waveguide are of the order of the light wavelength
    • H01S3/067—Fibre lasers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/23—Arrangements of two or more lasers not provided for in groups H01S3/02 - H01S3/22, e.g. tandem arrangements of separate active media
    • H01S3/2308—Amplifier arrangements, e.g. MOPA
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/005—Optical components external to the laser cavity, specially adapted therefor, e.g. for homogenisation or merging of the beams or for manipulating laser pulses, e.g. pulse shaping
    • H01S5/0078—Optical components external to the laser cavity, specially adapted therefor, e.g. for homogenisation or merging of the beams or for manipulating laser pulses, e.g. pulse shaping for frequency filtering
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/06—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium
    • H01S5/065—Mode locking; Mode suppression; Mode selection ; Self pulsating
    • H01S5/0656—Seeding, i.e. an additional light input is provided for controlling the laser modes, for example by back-reflecting light from an external optical component
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/50—Amplifier structures not provided for in groups H01S5/02 - H01S5/30
    • H01S5/5027—Concatenated amplifiers, i.e. amplifiers in series or cascaded
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/50—Amplifier structures not provided for in groups H01S5/02 - H01S5/30
    • H01S5/5045—Amplifier structures not provided for in groups H01S5/02 - H01S5/30 the arrangement having a frequency filtering function
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03B—GENERATION OF OSCILLATIONS, DIRECTLY OR BY FREQUENCY-CHANGING, BY CIRCUITS EMPLOYING ACTIVE ELEMENTS WHICH OPERATE IN A NON-SWITCHING MANNER; GENERATION OF NOISE BY SUCH CIRCUITS
    • H03B17/00—Generation of oscillations using radiation source and detector, e.g. with interposed variable obturator

Definitions

  • the invention relates to frequency locking of a laser source, and more particularly to the generation of microwave electrical signals optically by means of optoelectronic oscillators.
  • electronic or optoelectronic oscillators can be used.
  • the use of optoelectronic oscillators is preferred, because unlike electronic oscillators, they make it possible to obtain an optical signal which can transport information in free space or in a gas.
  • optical signals With optical signals, it is also possible to achieve low loss transmission and generate delay with optical fibers to increase the quality factor of the oscillator.
  • an optoelectronic oscillator makes it possible to obtain very low phase noise at room temperature thanks to the low losses which can be better than solutions based solely on electronic components.
  • the most common optoelectronic oscillators include a laser source, a modulator and a photodiode.
  • the modulator receives an optical signal from the laser source and an electrical signal.
  • the electrical signal is converted into an optical signal, which is modulated and possibly delayed if a large length of optical fiber (for example, from a few meters to a few kilometers) is placed at the output of the modulator.
  • This modulated optical signal is then converted into an electrical signal by a photodiode. Part of this converted signal is fed back into the modulator (Yao et al., "Optoelectronic oscillator for photonic System", IEEE Journal of Quantum Electronics, 32: 1141-1149, 1996).
  • the gallery mode optical resonator and more generally the optical generators will make it possible to generate a delay of the signal thanks to the numerous round trips made by the signal in the cavity of the resonator. For the same delay generated, it also has the advantage of being less bulky than an optical fiber.
  • the laser source is capable of locking by injection on one of the resonance modes of the resonator so that the laser light has an optical frequency corresponding to an optical resonant frequency. of the resonator and can thus propagate in the resonator.
  • the authors therefore use a high quality factor gallery mode optical resonator as well as a prism so that part of the signal leaving the resonator is reflected at the laser source.
  • the frequency of this reflected signal is a frequency belonging to one of the resonance modes of the resonator cavity.
  • the laser source then locks by injection on a frequency of one of the resonance modes and the losses of the optoelectronic oscillator are reduced.
  • this device remains restrictive because it requires the use of a resonator with a high quality factor.
  • the invention aims to remedy the aforementioned problems of the prior art and more particularly, it aims to propose a space-saving laser system, locked on a frequency, and not requiring an important quality factor optical resonator.
  • the laser system according to the invention can be applied to optoelectronic oscillators, but more generally, it can be applied to any system wishing to lock a laser source to a resonant cavity.
  • An object of the invention is therefore a laser system characterized in that it comprises a laser source having a locking range around a free frequency, an optical resonator, placed at the output of the laser source, having a resonance mode included in the locking range of the laser source, and an optical amplifier generating spontaneous emission at the frequency of said resonance mode included in the locking range of the laser source, the resonator being arranged so that it either coupled with the laser source and the amplifier.
  • the free spectral interval of the resonator is such that half the width of the locking range of the laser source is greater than or equal to half of the free spectral interval;
  • the free spectral interval of the resonator is greater than half the width of the locking range of the laser source
  • the laser source is a semiconductor laser or a fiber laser
  • the optical amplifier is a semiconductor amplifier or a fiber amplifier
  • the laser system comprises an optical modulator placed between the laser source and the resonator, so that the modulator is coupled with the laser source and the resonator, the modulation frequency of the modulator being an integer multiple of the free spectral range of the optical resonator;
  • the optical modulator is integrated into the laser source.
  • Another object of the invention is an optoelectronic oscillator characterized in that it comprises a laser system according to the invention and a photodiode converting an optical signal into an electrical signal, the photodiode being placed at the output of said optical amplifier and said modulator being connected at the output of the photodiode.
  • the laser source, the optical amplifier, the photodiode, the modulator and the optical resonator are installed on the same optoelectronic chip; and
  • the laser source, the optical amplifier, the photodiode and the modulator are implanted on a first optoelectronic chip, which can be in III-V semiconductor, and the optical resonator is implanted on a second optical chip, which can be in silicon..
  • FIG. 1 a laser system according to a first embodiment of the invention
  • FIG. 4 an optoelectronic oscillator according to a fourth embodiment of the invention.
  • FIG. 1 shows a laser system according to an embodiment of the invention.
  • a laser source SL emits an optical signal S of free frequency f 0 .
  • the range of locking by optical injection of the laser source SL is [f 0 - Af; f 0 + Af], where Af is half the width of the locking range and is given by equation (1). It corresponds to the frequency range, around the free frequency f 0 , in which the laser source SL can be locked spectrally by injection.
  • f A is the frequency of the optical signal injected into the laser source SL (frequency of the signal EAR in FIG. 1), f 0 the free emission frequency of the laser source SL, c the speed of light in a vacuum, n g the group refractive index in the laser structure, L the length of the laser cavity, h a factor linked to the coupling losses, l e the injection rate and a H the factor for improving the width of line (or Henry factor) (Bordonalli et al., "Optical injection locking to optical frequency combs for superchannel coherent detection", Optics Express, 23: 1547-1557, 2015).
  • the signal S is transmitted to an optical resonator R. This optical resonator has a free spectral interval ISL.
  • the laser source SL is coupled with the resonator R, the latter has at least one resonance mode whose frequency is included in the locking range of the laser source SL.
  • the signal S performs several round trips within the cavity of the resonator R, and the signal at the output of the resonator R, noted SR, can be a comb of optical frequencies, or more particularly a train of pulses, exhibiting delays or a continuous signal. Indeed, if the optical spectrum of the laser source SL is monochromatic, if there are no non-linear effects in the resonator R and if there are no other signals, other than the signal from the laser source SL, injected into the resonator, then the signal at the output of the resonator will be a continuous signal.
  • the signal at the output of the resonator R is a comb of optical frequencies.
  • the first pulse of the pulse train has a delay of a time corresponding to a go into the cavity and the other pulses of the train have, relative to this first pulse, delays which are integer multiples of the time corresponding to a round trip in the cavity.
  • This signal SR corresponds, in the spectral domain, to a comb of optical lines spaced by a frequency ISL.
  • the signal SR then passes through an optical amplifier A generating spontaneous emission EA.
  • the signal coming from amplifier A (SRA) is a comb of amplified optical lines, spaced by an ISL frequency.
  • the radiation from the spontaneous emission EA propagates in all directions, in particular in the direction of the resonator R.
  • the spectral range of the spontaneous emission EA comprises at least one of the resonance modes of the resonator R, which is included in the locking range of the laser source SL ([f 0 - Af; f 0 + Af]), and includes the free frequency f 0 of the laser source SL.
  • the amplifier A is therefore coupled with the resonator R. Leaving the resonator R, the spontaneous emission EA becomes the signal EAR which is, in the spectral domain, a comb of optical lines spaced by a frequency ISL.
  • This EAR comb is injected into the laser source SL and comprises at least one optical line of frequency included in the locking range of the laser source SL ([f 0 - Af; f 0 + Af]). This thus makes it possible to lock the laser source SL on one of the frequencies of a resonance mode of the resonator R, this frequency belonging to the interval [f 0 - Af; f 0 + Af].
  • the optical frequency of the laser source SL is exactly between two resonance modes of the resonator R. Therefore, in order to ensure that, even in this case, at least one resonance mode of the resonator R is included in the locking range of the laser source SL, it is necessary that half the width of the locking range, that is to say Af, of the laser source SL is greater than or equal to half the free spectral interval ISL of the resonator R, that is to say ISL / 2 less than or equal to Af. However, it is not essential that this condition be satisfied, as long as the difference between the optical frequency f 0 and at least one mode of the resonator is less than or equal to Af, half the width of the locking range.
  • half the width of the locking range, Af, of the laser source SL is less than the free spectral interval ISL of the resonator R, that is to say Af ⁇ ISL.
  • half the width of the locking range Af is greater than the free spectral interval ISL of the resonator, that is to say Af> ISL, there may be several resonance modes included in the range of SL laser source locking. In this case, it is the mode having the frequency closest to the free frequency f 0 of the laser source SL which will give rise to locking.
  • the optical amplifier A can be a semiconductor amplifier, a fiber optical amplifier or a solid state amplifier.
  • the solid state amplifier may contain rare earth doped glasses, which can be put into the form of fiber.
  • Amplifier A is, for example, an optical amplifier with erbium-doped fiber, since the spontaneous emission spectrum of this amplifier covers a frequency range wide enough to cover several resonance modes of an optical resonator.
  • the SL laser source can be a semiconductor laser, since this type of laser is able to lock at a frequency by simple injection.
  • the laser source can be a fiber laser, which makes it possible to have a signal at the output of the laser source of higher power than with a semiconductor laser.
  • FIG. 2 shows a laser system according to a second embodiment of the invention.
  • the laser source SL is locked on a resonance mode of the resonator R according to the conditions specified in the description of FIG. 1.
  • An optical modulator M is placed between the laser source SL and the optical resonator R.
  • the signal leaving the modulator comprises lateral bands spaced from the frequency f M and centered on f 0 , or if the modulation frequency f M is not equal to the free spectral interval ISL or to one of its harmonics , it is possible that part of the signal leaving the modulator M does not belong to any resonance mode of the resonator R. In this case, this part of the signal would not be coupled to one of the modes of the resonator and would then be lost.
  • a photodiode P is placed at the output of amplifier A to convert the optical signal leaving amplifier A into an electrical signal.
  • the modulator M receives an electrical signal S e as an input
  • the signal S e iec_fiitre at the output of the photodiode P is the electrical signal S e
  • the modulator M is integrated into the laser source SL.
  • FIG. 3 shows an optoelectronic oscillator according to a third embodiment of the invention.
  • the optoelectronic oscillator generates hyper-frequency electronic signals. It includes a laser system such as that described in FIG. 2.
  • the electrical signal S e iec_fiitre leaving the photodiode P is sent to an electrical coupler CE, possibly with passage through an electrical filter FE.
  • the CE coupler makes it possible to send part of the electrical signal S e iec_fiitre to the output of the oscillator SO and the other part of the signal to the electrical input of the modulator M.
  • FIG. 4 represents an optoelectronic oscillator according to a fourth embodiment of the invention.
  • the laser source L, the optical modulator M, the optical amplifier A and the photodiode D are implanted on an optoelectronic chip of III-V PSC semiconductor.
  • the optical resonator R is installed on another PSI silicon optical chip.
  • An optical guide FO which can be an optical fiber is implanted on the two chips to guide the optical signal SO leaving the laser source L. From the spontaneous emission EA is emitted by the optical amplifier A.
  • the elements are implanted on two different chips in order to reduce losses.
  • the optical signal SO is converted by the photodiode D into an electrical signal S eiec , which is then sent to the input of the modulator M.
  • the elements making up the oscillator can be installed on the same optoelectronic chip, the chip being able to be of III-V semiconductor.

Abstract

The invention relates to a laser system characterised in that it comprises a laser source having a locking range around a free frequency f0, an optical resonator arranged at the output of the laser source and having a resonance mode within the locking range of the laser source, and an optical amplifier generating spontaneous emission at the frequency of said resonance mode within the locking range of the laser source, the resonator being arranged in such a way that it is coupled to the laser source and the amplifier.

Description

VERROUILLAGE D'UN LASER SUR UN RESONATEUR AVEC L'AIDE D'UN  LOCKING A LASER ON A RESONATOR WITH THE HELP OF A
AMPLIFICATEUR OPTIQUE  OPTICAL AMPLIFIER
L'invention concerne le verrouillage en fréquence d'une source laser, et plus particulièrement la génération de signaux électriques microondes par voie optique grâce à des oscillateurs optoélectroniques. The invention relates to frequency locking of a laser source, and more particularly to the generation of microwave electrical signals optically by means of optoelectronic oscillators.
Pour des applications d'optique hyper-fréquence, des oscillateurs électroniques ou optoélectroniques peuvent être utilisés. L'utilisation d'oscillateurs optoélectroniques est privilégiée, car contrairement aux oscillateurs électroniques, ils permettent d'obtenir un signal optique pouvant transporter l'information en espace libre ou dans un gaz. Avec des signaux optiques, il est également possible d'obtenir une transmission à faible perte et de générer un retard avec des fibres optiques afin d'augmenter le facteur de qualité de l'oscillateur. De plus, un oscillateur optoélectronique permet d'obtenir de très faibles bruits de phase à température ambiante grâce aux faibles pertes qui peuvent être meilleures que des solutions basées uniquement sur des composants électroniques. For hyper-frequency optical applications, electronic or optoelectronic oscillators can be used. The use of optoelectronic oscillators is preferred, because unlike electronic oscillators, they make it possible to obtain an optical signal which can transport information in free space or in a gas. With optical signals, it is also possible to achieve low loss transmission and generate delay with optical fibers to increase the quality factor of the oscillator. In addition, an optoelectronic oscillator makes it possible to obtain very low phase noise at room temperature thanks to the low losses which can be better than solutions based solely on electronic components.
Les oscillateurs optoélectroniques les plus courants comprennent une source laser, un modulateur et une photodiode. Le modulateur reçoit un signal optique de la part de la source laser et un signal électrique. Au passage dans le modulateur, le signal électrique est converti en signal optique, qui est modulé et éventuellement retardé si une grande longueur de fibre optique (par exemple, de quelques mètres à quelques kilomètres) est placée en sortie du modulateur. Ce signal optique modulé est ensuite converti en signal électrique par une photodiode. Une partie de ce signal converti est réinjectée dans le modulateur (Yao et al., « Optoelectronic oscillator for photonic System», IEEE Journal of Quantum Electronics, 32 : 1141-1149, 1996). The most common optoelectronic oscillators include a laser source, a modulator and a photodiode. The modulator receives an optical signal from the laser source and an electrical signal. When passing through the modulator, the electrical signal is converted into an optical signal, which is modulated and possibly delayed if a large length of optical fiber (for example, from a few meters to a few kilometers) is placed at the output of the modulator. This modulated optical signal is then converted into an electrical signal by a photodiode. Part of this converted signal is fed back into the modulator (Yao et al., "Optoelectronic oscillator for photonic System", IEEE Journal of Quantum Electronics, 32: 1141-1149, 1996).
Ces oscillateurs présentent, cependant, quelques inconvénients : ils peuvent être encombrants, notamment à cause de la longueur de fibre optique, et instables, notamment à cause des variations de température influençant les performances de la fibre optique. C'est pourquoi, les auteurs Savchenkov et al. (Savchenkov et al. « Whispering-gallery mode based opto-electronic oscillators », IEEE International Frequency Control Symposium, 1-4 juin 2010) et Liang et al. (Liang et al. « Whispering-gallery-mode-resonator-based ultranarrow linewidth external-cavity semiconductor laser », Optics letters, 35:2822, 2010) utilisent un résonateur optique à mode de galerie à la place de la fibre optique. Le résonateur optique à mode de galerie et plus généralement les générateurs optiques vont permettre de générer un retard du signal grâce aux nombreux allers-retours effectués par le signal dans la cavité du résonateur. Pour un même retard généré, il présente également l'avantage d'être moins encombrant qu'une fibre optique. Cependant pour que l'oscillateur optoélectronique fonctionne, il est nécessaire que la source laser soit capable de se verrouiller par injection sur l'un des modes de résonance du résonateur afin que la lumière du laser ait une fréquence optique correspondant à une fréquence optique de résonnance du résonateur et puisse ainsi se propager dans le résonateur. Dans ces deux documents, les auteurs utilisent donc un résonateur optique à mode de galerie à fort facteur de qualité ainsi qu'un prisme pour qu'une partie du signal sortant du résonateur soit réfléchie à la source laser. La fréquence de ce signal réfléchi est une fréquence appartenant à l'un des modes de résonance de la cavité du résonateur. La source laser se verrouille alors par injection sur une fréquence d'un des modes de résonance et les pertes de l'oscillateur optoélectronique sont réduites. Ce dispositif reste cependant contraignant car il nécessite l'utilisation d'un résonateur à fort facteur de qualité. These oscillators have, however, some drawbacks: they can be bulky, especially because of the length of optical fiber, and unstable, especially because of temperature variations influencing the performance of the optical fiber. Therefore, the authors Savchenkov et al. (Savchenkov et al. "Whispering-gallery mode based opto-electronic oscillators", IEEE International Frequency Control Symposium, June 1-4, 2010) and Liang et al. (Liang et al. "Whispering-gallery-mode-resonator-based ultranarrow linewidth external-cavity semiconductor laser ”, Optics letters, 35: 2822, 2010) use a gallery mode optical resonator instead of fiber optics. The gallery mode optical resonator and more generally the optical generators will make it possible to generate a delay of the signal thanks to the numerous round trips made by the signal in the cavity of the resonator. For the same delay generated, it also has the advantage of being less bulky than an optical fiber. However, for the optoelectronic oscillator to work, it is necessary that the laser source is capable of locking by injection on one of the resonance modes of the resonator so that the laser light has an optical frequency corresponding to an optical resonant frequency. of the resonator and can thus propagate in the resonator. In these two documents, the authors therefore use a high quality factor gallery mode optical resonator as well as a prism so that part of the signal leaving the resonator is reflected at the laser source. The frequency of this reflected signal is a frequency belonging to one of the resonance modes of the resonator cavity. The laser source then locks by injection on a frequency of one of the resonance modes and the losses of the optoelectronic oscillator are reduced. However, this device remains restrictive because it requires the use of a resonator with a high quality factor.
Pour améliorer la stabilité d'un oscillateur, il est également possible de verrouiller une source laser sur un des modes de résonance d'un résonateur en utilisant un système de Pound-Drever-Hall (Saleh et al. « Phase noise performance comparison between optoelectronic oscillators based on optical delay lines and whispering gallery mode resonators », Optics Express, 22 : 32158-32173, 2014). Le principe de ce système est de mesurer la fréquence du signal en sortie de la source laser dans une cavité de Fabry-Perrot et de renvoyer cette mesure à la source laser pour supprimer les fluctuations en fréquence. Donc en améliorant la fréquence mesurée du signal, on améliore en même temps la pureté du signal renvoyé vers le laser. Ce système est assez complexe à mettre en place car il faut à la fois pouvoir mesurer la fréquence de la source laser et à la fois ajuster cette fréquence, cela étant fait de manière électronique. Il présente un inconvénient supplémentaire car il applique une modulation de phase du signal. To improve the stability of an oscillator, it is also possible to lock a laser source on one of the resonance modes of a resonator using a Pound-Drever-Hall system (Saleh et al. “Phase noise performance comparison between optoelectronic oscillators based on optical delay lines and whispering gallery mode resonators ”, Optics Express, 22: 32158-32173, 2014). The principle of this system is to measure the frequency of the signal at the output of the laser source in a Fabry-Perrot cavity and to send this measurement back to the laser source to eliminate the frequency fluctuations. So by improving the measured frequency of the signal, we simultaneously improve the purity of the signal returned to the laser. This system is quite complex to set up because it is necessary both to be able to measure the frequency of the laser source and at the same time to adjust this frequency, this being done electronically. It has an additional disadvantage because it applies a phase modulation of the signal.
L'invention vise à remédier aux problèmes précités de l'art antérieur et plus particulièrement, elle vise à proposer un système laser peu encombrant, verrouillé sur une fréquence, et ne nécessitant pas de résonateur optique de facteur de qualité important. Le système laser selon l'invention peut s'appliquer aux oscillateurs optoélectroniques, mais plus généralement, il peut s'appliquer à tout système souhaitant verrouiller une source laser à une cavité résonante. The invention aims to remedy the aforementioned problems of the prior art and more particularly, it aims to propose a space-saving laser system, locked on a frequency, and not requiring an important quality factor optical resonator. The laser system according to the invention can be applied to optoelectronic oscillators, but more generally, it can be applied to any system wishing to lock a laser source to a resonant cavity.
Un objet de l'invention est donc un système laser caractérisé en ce qu'il comprend une source laser présentant une plage de verrouillage autour d'une fréquence libre, un résonateur optique, placé en sortie de la source laser, présentant un mode de résonance compris dans la plage de verrouillage de la source laser, et un amplificateur optique générant de l'émission spontanée à la fréquence dudit mode de résonance compris dans la plage de verrouillage de la source laser, le résonateur étant agencé de manière à ce qu'il soit couplé avec la source laser et l'amplificateur. An object of the invention is therefore a laser system characterized in that it comprises a laser source having a locking range around a free frequency, an optical resonator, placed at the output of the laser source, having a resonance mode included in the locking range of the laser source, and an optical amplifier generating spontaneous emission at the frequency of said resonance mode included in the locking range of the laser source, the resonator being arranged so that it either coupled with the laser source and the amplifier.
Selon des modes de réalisation particuliers de l'invention : According to particular embodiments of the invention:
L'intervalle spectral libre du résonateur est tel que la moitié de la largeur de la plage de verrouillage de la source laser est supérieure ou égale à la moitié de l'intervalle spectral libre ; The free spectral interval of the resonator is such that half the width of the locking range of the laser source is greater than or equal to half of the free spectral interval;
L'intervalle spectral libre du résonateur est supérieur à la moitié de la largeur de la plage de verrouillage de la source laser ;  The free spectral interval of the resonator is greater than half the width of the locking range of the laser source;
La source laser est un laser à semi-conducteurs ou un laser à fibre ;  The laser source is a semiconductor laser or a fiber laser;
L'amplificateur optique est un amplificateur à semi-conducteurs ou un amplificateur à fibre ;  The optical amplifier is a semiconductor amplifier or a fiber amplifier;
Le système laser comprend un modulateur optique placé entre la source laser et le résonateur, de manière à ce que le modulateur soit couplé avec la source laser et le résonateur, la fréquence de modulation du modulateur étant un multiple entier de l'intervalle spectral libre du résonateur optique ; et  The laser system comprises an optical modulator placed between the laser source and the resonator, so that the modulator is coupled with the laser source and the resonator, the modulation frequency of the modulator being an integer multiple of the free spectral range of the optical resonator; and
Le modulateur optique est intégré à la source laser.  The optical modulator is integrated into the laser source.
Un autre objet de l'invention est un oscillateur optoélectronique caractérisé en ce qu'il comprend un système laser selon l'invention et une photodiode convertissant un signal optique en signal électrique, la photodiode étant placée en sortie dudit amplificateur optique et ledit modulateur étant connecté à la sortie de la photodiode. Selon des modes de réalisation particuliers : Another object of the invention is an optoelectronic oscillator characterized in that it comprises a laser system according to the invention and a photodiode converting an optical signal into an electrical signal, the photodiode being placed at the output of said optical amplifier and said modulator being connected at the output of the photodiode. According to particular embodiments:
La source laser, l'amplificateur optique, la photodiode, le modulateur et le résonateur optique sont implantés sur une même puce optoélectronique ; et La source laser, l'amplificateur optique, la photodiode et le modulateur sont implantés sur une première puce optoélectronique, qui peut être en semi- conducteur lll-V, et le résonateur optique est implanté sur une seconde puce optique, qui peut être en silicium.. The laser source, the optical amplifier, the photodiode, the modulator and the optical resonator are installed on the same optoelectronic chip; and The laser source, the optical amplifier, the photodiode and the modulator are implanted on a first optoelectronic chip, which can be in III-V semiconductor, and the optical resonator is implanted on a second optical chip, which can be in silicon..
D'autres caractéristiques, détails et avantages de l'invention ressortiront à la lecture de la description faite en référence aux figures annexées et qui représentent respectivement : Other characteristics, details and advantages of the invention will emerge on reading the description made with reference to the appended figures, which respectively represent:
La figure 1, un système laser selon un premier mode de réalisation de l'invention ;Figure 1, a laser system according to a first embodiment of the invention;
La figure 2, un système laser selon un second mode de réalisation de l'invention ;Figure 2, a laser system according to a second embodiment of the invention;
La figure 3, un oscillateur optoélectronique selon un troisième mode de réalisation de l'invention ; et Figure 3, an optoelectronic oscillator according to a third embodiment of the invention; and
La figure 4, un oscillateur optoélectronique selon un quatrième mode de réalisation de l'invention.  Figure 4, an optoelectronic oscillator according to a fourth embodiment of the invention.
La figure 1 présente un système laser selon un mode de réalisation de l'invention. Une source laser SL émet un signal optique S de fréquence libre f0. La plage de verrouillage par injection optique de la source laser SL est [f0 - Af ; f0 + Af], où Af est la moitié de la largeur de la plage de verrouillage et est donnée par l'équation (1). Elle correspond à la plage de fréquence, autour de la fréquence libre f0, dans laquelle la source laser SL peut se verrouiller spectralement par injection. FIG. 1 shows a laser system according to an embodiment of the invention. A laser source SL emits an optical signal S of free frequency f 0 . The range of locking by optical injection of the laser source SL is [f 0 - Af; f 0 + Af], where Af is half the width of the locking range and is given by equation (1). It corresponds to the frequency range, around the free frequency f 0 , in which the laser source SL can be locked spectrally by injection.
Où fA est la fréquence du signal optique injecté à la source laser SL (fréquence du signal EAR dans la figure 1), f0 la fréquence libre d'émission de la source laser SL, c la vitesse de la lumière dans le vide, ng l'indice de réfraction de groupe dans la structure laser, L la longueur de la cavité laser, h un facteur lié aux pertes de couplage, le le taux d'injection et aH le facteur d'amélioration de la largeur de ligne (ou facteur d'Henry) (Bordonalli et al., « Optical injection locking to optical frequency combs for superchannel cohérent détection », Optics Express, 23 : 1547-1557, 2015). Le signal S est transmis à un résonateur optique R. Ce résonateur optique a un intervalle spectral libre ISL. Afin que la source laser SL soit couplée avec le résonateur R, celui-ci possède au moins un mode de résonance dont la fréquence est comprise dans la plage de verrouillage de la source laser SL. Le signal S effectue plusieurs allers-retours au sein de la cavité du résonateur R, et le signal en sortie du résonateur R, noté SR, peut être un peigne de fréquences optiques, ou plus particulièrement un train d'impulsions, présentant des retards ou un signal continu. En effet, si le spectre optique de la source laser SL est monochromatique, s'il n'y a pas d'effets non-linéaires dans le résonateur R et s'il n'y a pas d'autres signaux, autres que le signal issu de la source laser SL, injectés dans le résonateur, alors le signal en sortie du résonateur sera un signal continu. S'il y a des effets non-linéaires dans le résonateur, le signal en sortie du résonateur R est un peigne de fréquences optiques. Dans le cas d'un train d'impulsions, la première impulsion du train d'impulsions présente un retard d'un temps correspondant à un aller dans la cavité et les autres impulsions du train présentent, par rapport à cette première impulsion, des retards qui sont des multiples entiers du temps correspondant à un aller-retour dans la cavité. Ce signal SR correspond, en domaine spectral, à un peigne de raies optiques espacées d'une fréquence ISL. Le signal SR passe ensuite dans un amplificateur optique A générant de l'émission spontanée EA. Le signal sortant de l'amplificateur A (SRA) est un peigne de raies optiques amplifié, espacées d'une fréquence ISL. Le rayonnement issu de l'émission spontanée EA se propage dans toutes les directions, notamment dans la direction du résonateur R. De plus, la plage spectrale de l'émission spontanée EA comprend au moins un des modes de résonance du résonateur R, qui est compris dans la plage de verrouillage de la source laser SL ([f0 - Af ; f0 + Af]), et comprend la fréquence libre f0 de la source laser SL. L'amplificateur A est donc couplé avec le résonateur R. En sortant du résonateur R, l'émission spontanée EA devient le signal EAR qui est, dans le domaine spectral, un peigne de raies optiques espacées d'une fréquence ISL. Ce peigne EAR est injecté à la source laser SL et comprend au moins une raie optique de fréquence comprise dans la plage de verrouillage de la source laser SL ([f0 - Af ; f0 + Af]). Cela permet ainsi de verrouiller la source laser SL sur une des fréquences d'un mode de résonance du résonateur R, cette fréquence appartenant à l'intervalle [f0 - Af ; f0 + Af]. Where f A is the frequency of the optical signal injected into the laser source SL (frequency of the signal EAR in FIG. 1), f 0 the free emission frequency of the laser source SL, c the speed of light in a vacuum, n g the group refractive index in the laser structure, L the length of the laser cavity, h a factor linked to the coupling losses, l e the injection rate and a H the factor for improving the width of line (or Henry factor) (Bordonalli et al., "Optical injection locking to optical frequency combs for superchannel coherent detection", Optics Express, 23: 1547-1557, 2015). The signal S is transmitted to an optical resonator R. This optical resonator has a free spectral interval ISL. So that the laser source SL is coupled with the resonator R, the latter has at least one resonance mode whose frequency is included in the locking range of the laser source SL. The signal S performs several round trips within the cavity of the resonator R, and the signal at the output of the resonator R, noted SR, can be a comb of optical frequencies, or more particularly a train of pulses, exhibiting delays or a continuous signal. Indeed, if the optical spectrum of the laser source SL is monochromatic, if there are no non-linear effects in the resonator R and if there are no other signals, other than the signal from the laser source SL, injected into the resonator, then the signal at the output of the resonator will be a continuous signal. If there are non-linear effects in the resonator, the signal at the output of the resonator R is a comb of optical frequencies. In the case of a pulse train, the first pulse of the pulse train has a delay of a time corresponding to a go into the cavity and the other pulses of the train have, relative to this first pulse, delays which are integer multiples of the time corresponding to a round trip in the cavity. This signal SR corresponds, in the spectral domain, to a comb of optical lines spaced by a frequency ISL. The signal SR then passes through an optical amplifier A generating spontaneous emission EA. The signal coming from amplifier A (SRA) is a comb of amplified optical lines, spaced by an ISL frequency. The radiation from the spontaneous emission EA propagates in all directions, in particular in the direction of the resonator R. In addition, the spectral range of the spontaneous emission EA comprises at least one of the resonance modes of the resonator R, which is included in the locking range of the laser source SL ([f 0 - Af; f 0 + Af]), and includes the free frequency f 0 of the laser source SL. The amplifier A is therefore coupled with the resonator R. Leaving the resonator R, the spontaneous emission EA becomes the signal EAR which is, in the spectral domain, a comb of optical lines spaced by a frequency ISL. This EAR comb is injected into the laser source SL and comprises at least one optical line of frequency included in the locking range of the laser source SL ([f 0 - Af; f 0 + Af]). This thus makes it possible to lock the laser source SL on one of the frequencies of a resonance mode of the resonator R, this frequency belonging to the interval [f 0 - Af; f 0 + Af].
Il est possible que la fréquence optique de la source laser SL se trouve exactement entre deux modes de résonance du résonateur R. Par conséquent, afin de s'assurer que, même dans ce cas, au moins un mode de résonance du résonateur R soit compris dans la plage de verrouillage de la source laser SL, il faut que la moitié de la largeur de la plage de verrouillage, c'est-à-dire Af, de la source laser SL soit supérieure ou égale à la moitié de l'intervalle spectral libre ISL du résonateur R, c'est-à-dire ISL/2 inférieur ou égal à Af. Il n'est cependant pas essentiel que cette condition soit satisfaite, du moment que l'écart entre la fréquence optique f0 et au moins un mode du résonateur est inférieur ou égal à Af, moitié de la largeur de la plage de verrouillage. De plus, afin de minimiser le nombre de modes de résonance appartenant à la plage de verrouillage, la moitié de la largeur de la plage de verrouillage, Af, de la source laser SL est inférieure à l'intervalle spectral libre ISL du résonateur R, c'est-à-dire Af < ISL. Néanmoins, si la moitié de la largeur de la plage de verrouillage Af est supérieure à l'intervalle spectral libre ISL du résonateur, c'est-à-dire Af > ISL, il peut y avoir plusieurs modes de résonance compris dans la plage de verrouillage de la source laser SL. Dans ce cas, c'est le mode présentant la fréquence la plus proche de la fréquence libre f0 de la source laser SL qui donnera lieu au verrouillage. It is possible that the optical frequency of the laser source SL is exactly between two resonance modes of the resonator R. Therefore, in order to ensure that, even in this case, at least one resonance mode of the resonator R is included in the locking range of the laser source SL, it is necessary that half the width of the locking range, that is to say Af, of the laser source SL is greater than or equal to half the free spectral interval ISL of the resonator R, that is to say ISL / 2 less than or equal to Af. However, it is not essential that this condition be satisfied, as long as the difference between the optical frequency f 0 and at least one mode of the resonator is less than or equal to Af, half the width of the locking range. In addition, in order to minimize the number of resonance modes belonging to the locking range, half the width of the locking range, Af, of the laser source SL is less than the free spectral interval ISL of the resonator R, that is to say Af <ISL. However, if half the width of the locking range Af is greater than the free spectral interval ISL of the resonator, that is to say Af> ISL, there may be several resonance modes included in the range of SL laser source locking. In this case, it is the mode having the frequency closest to the free frequency f 0 of the laser source SL which will give rise to locking.
L'amplificateur optique A peut être un amplificateur à semi-conducteurs, un amplificateur optique à fibre ou un amplificateur à état solide. L'amplificateur à état solide peut contenir des verres dopés aux terres rares, pouvant être mis sous la forme de fibre. L'amplificateur A est, par exemple, un amplificateur optique à fibre dopée erbium, car le spectre d'émission spontanée de cet amplificateur couvre une gamme de fréquence suffisamment large pour couvrir plusieurs modes de résonance d'un résonateur optique. The optical amplifier A can be a semiconductor amplifier, a fiber optical amplifier or a solid state amplifier. The solid state amplifier may contain rare earth doped glasses, which can be put into the form of fiber. Amplifier A is, for example, an optical amplifier with erbium-doped fiber, since the spontaneous emission spectrum of this amplifier covers a frequency range wide enough to cover several resonance modes of an optical resonator.
La source laser SL peut être un laser à semi-conducteurs, car ce type de laser est capable de se verrouiller à une fréquence par simple injection. The SL laser source can be a semiconductor laser, since this type of laser is able to lock at a frequency by simple injection.
Selon un autre mode de réalisation de l'invention, la source laser peut être un laser à fibres ce qui permet d'avoir un signal en sortie de la source laser de puissance plus élevée qu'avec un laser à semi-conducteurs. According to another embodiment of the invention, the laser source can be a fiber laser, which makes it possible to have a signal at the output of the laser source of higher power than with a semiconductor laser.
La figure 2 présente un système laser selon un deuxième mode de réalisation de l'invention. La source laser SL est verrouillée sur un mode de résonance du résonateur R selon les conditions précisées dans la description de la figure 1. Un modulateur optique M est placé entre la source laser SL et le résonateur optique R. La fréquence de modulation fM du modulateur est égale à l'intervalle spectral libre ISL du résonateur R ou à une de ses harmoniques, c'est-à-dire que la fréquence fM est de la forme fM = N x ISL, avec N un entier naturel strictement positif. En effet, le signal sortant du modulateur comprend des bandes latérales espacées de la fréquence fM et centrées sur f0, or si la fréquence de modulation fM n'est pas égale à l'intervalle spectral libre ISL ou à une de ses harmoniques, il est possible qu'une partie du signal sortant du modulateur M n'appartienne à aucun mode de résonance du résonateur R. Dans ce cas, cette partie du signal ne serait pas couplée à un des modes du résonateur et serait alors perdue. Une photodiode P est placée en sortie de l'amplificateur A pour convertir le signal optique sortant de l'amplificateur A en signal électrique. Le modulateur M reçoit en entrée un signal électrique Se|ec. Le signal Seiec_fiitre en sortie de la photodiode P est le signal électrique Se|ec filtré par voie optique par le résonateur R. Figure 2 shows a laser system according to a second embodiment of the invention. The laser source SL is locked on a resonance mode of the resonator R according to the conditions specified in the description of FIG. 1. An optical modulator M is placed between the laser source SL and the optical resonator R. The modulation frequency f M of the modulator is equal to the free spectral interval ISL of the resonator R or to one of its harmonics, that is to say that the frequency f M is of the form f M = N x ISL, with N a strictly positive natural number. Indeed, the signal leaving the modulator comprises lateral bands spaced from the frequency f M and centered on f 0 , or if the modulation frequency f M is not equal to the free spectral interval ISL or to one of its harmonics , it is possible that part of the signal leaving the modulator M does not belong to any resonance mode of the resonator R. In this case, this part of the signal would not be coupled to one of the modes of the resonator and would then be lost. A photodiode P is placed at the output of amplifier A to convert the optical signal leaving amplifier A into an electrical signal. The modulator M receives an electrical signal S e as an input | ec . The signal S e iec_fiitre at the output of the photodiode P is the electrical signal S e | ec filtered optically by the resonator R.
Selon un autre mode de réalisation de l'invention, le modulateur M est intégré à la source laser SL. According to another embodiment of the invention, the modulator M is integrated into the laser source SL.
La figure 3 présente un oscillateur optoélectronique selon un troisième mode de réalisation de l'invention. L'oscillateur optoélectronique permet de générer des signaux électroniques hyper-fréquence. Il comprend un système laser tel que celui décrit en figure 2. Le signal électrique Seiec_fiitre sortant de la photodiode P est envoyé vers un coupleur électrique CE, avec éventuellement un passage dans un filtre électrique FE. Le coupleur CE permet d'envoyer une partie du signal électrique Seiec_fiitre vers la sortie de l'oscillateur SO et l'autre partie du signal vers l'entrée électrique du modulateur M. Le filtrage du signal Se|ec par voie optique et le rebouclage du signal Se|ec filtré, noté Seiec_fîitre en sortie de la photodiode P, sur le modulateur M permettent de réaliser un oscillateur opto-électronique générant des signaux de très grande pureté spectrale, grâce à la source laser SL verrouillée sur une fréquence. Figure 3 shows an optoelectronic oscillator according to a third embodiment of the invention. The optoelectronic oscillator generates hyper-frequency electronic signals. It includes a laser system such as that described in FIG. 2. The electrical signal S e iec_fiitre leaving the photodiode P is sent to an electrical coupler CE, possibly with passage through an electrical filter FE. The CE coupler makes it possible to send part of the electrical signal S e iec_fiitre to the output of the oscillator SO and the other part of the signal to the electrical input of the modulator M. Filtering of the signal S e | ec by optical means and looping back the signal S e | ec filtered, noted S e iec_fîitre at the output of the photodiode P, on the modulator M allow an opto-electronic oscillator to be generated generating signals of very high spectral purity, thanks to the laser source SL locked on a frequency.
La figure 4 représente un oscillateur optoélectronique selon un quatrième mode de réalisation de l'invention. La source laser L, le modulateur optique M, l'amplificateur optique A et la photodiode D sont implantés sur une puce optoélectronique en semi-conducteur lll-V PSC. Le résonateur optique R est implanté sur une autre puce optique en silicium PSI. Un guide optique FO qui peut être une fibre optique est implanté sur les deux puces pour guider le signal optique SO sortant de la source laser L. De l'émission spontanée EA est émise par l'amplificateur optique A. Les éléments sont implantés sur deux puces différentes afin de réduire les pertes. Le signal optique SO est converti par la photodiode D en signal électrique Seiec, qui est ensuite envoyé en entrée du modulateur M. FIG. 4 represents an optoelectronic oscillator according to a fourth embodiment of the invention. The laser source L, the optical modulator M, the optical amplifier A and the photodiode D are implanted on an optoelectronic chip of III-V PSC semiconductor. The optical resonator R is installed on another PSI silicon optical chip. An optical guide FO which can be an optical fiber is implanted on the two chips to guide the optical signal SO leaving the laser source L. From the spontaneous emission EA is emitted by the optical amplifier A. The elements are implanted on two different chips in order to reduce losses. The optical signal SO is converted by the photodiode D into an electrical signal S eiec , which is then sent to the input of the modulator M.
Selon un autre mode de réalisation de l'invention, les éléments composant l'oscillateur peuvent être implantés sur la même puce optoélectronique, la puce pouvant être en semi- conducteur lll-V. According to another embodiment of the invention, the elements making up the oscillator can be installed on the same optoelectronic chip, the chip being able to be of III-V semiconductor.

Claims

Revendications claims
1. Système laser caractérisé en ce qu'il comprend : 1. Laser system characterized in that it comprises:
Une source laser présentant une plage de verrouillage autour d'une fréquence libre f0 ; A laser source having a locking range around a free frequency f 0 ;
Un résonateur optique, présentant un mode de résonance dont la largeur spectrale est comprise dans la plage de verrouillage de la source laser ; et Un amplificateur optique générant de l'émission spontanée à la fréquence dudit mode de résonance compris dans la plage de verrouillage de la source laser,  An optical resonator, having a resonance mode whose spectral width is included in the locking range of the laser source; and an optical amplifier generating spontaneous emission at the frequency of said resonance mode included in the locking range of the laser source,
Le résonateur étant placé entre et couplé avec la source laser et l'amplificateur, de telle sorte que seule une partie de l'émission spontanée générée par l'amplificateur optique comprise dans la largeur spectrale du mode de résonance du résonateur soit injectée dans la source laser. The resonator being placed between and coupled with the laser source and the amplifier, so that only part of the spontaneous emission generated by the optical amplifier included in the spectral width of the resonance mode of the resonator is injected into the source laser.
2. Système laser selon la revendication 1, dans lequel l'intervalle spectral libre du résonateur ISL est tel que la moitié de la largeur de la plage de verrouillage de la source laser est supérieure ou égale à la moitié de l'intervalle spectral libre ISL. 2. The laser system according to claim 1, in which the free spectral interval of the ISL resonator is such that half the width of the locking range of the laser source is greater than or equal to half of the free spectral interval ISL. .
3. Système laser selon l'une des revendications précédentes, dans lequel l'intervalle spectral libre du résonateur ISL est supérieur à la moitié de la largeur de la plage de verrouillage de la source laser. 3. Laser system according to one of the preceding claims, in which the free spectral interval of the ISL resonator is greater than half the width of the locking range of the laser source.
4. Système laser selon l'une des revendications précédentes dans lequel la source laser est un laser à semi-conducteurs ou laser à fibres. 4. Laser system according to one of the preceding claims wherein the laser source is a semiconductor laser or fiber laser.
5. Système laser selon l'une des revendications précédentes dans lequel l'amplificateur optique est un amplificateur à semi-conducteurs. 5. Laser system according to one of the preceding claims wherein the optical amplifier is a semiconductor amplifier.
6. Système laser selon l'une des revendications 1 à 4 dans lequel ledit amplificateur optique est un amplificateur à fibre. 6. Laser system according to one of claims 1 to 4 wherein said optical amplifier is a fiber amplifier.
7. Système laser selon l'une des revendications précédentes, dans lequel le système comprend un modulateur optique, placé entre la source laser et le résonateur, de manière à ce que le modulateur soit couplé avec la source laser et le résonateur, la fréquence de modulation fM du modulateur étant un multiple entier de l'intervalle spectral libre ISL du résonateur optique. 7. Laser system according to one of the preceding claims, in which the system comprises an optical modulator, placed between the laser source and the resonator, so that the modulator is coupled with the laser source and the resonator, the frequency of modulation f M of the modulator being an integer multiple of the free spectral interval ISL of the optical resonator.
8. Système laser selon la revendication 7 dans lequel ledit modulateur optique est intégré à la source laser. 8. The laser system according to claim 7, wherein said optical modulator is integrated into the laser source.
9. Oscillateur optoélectronique caractérisé en ce qu'il comprend : 9. Optoelectronic oscillator characterized in that it comprises:
Un système laser selon l'une des revendications 7 à 8 ; et  A laser system according to one of claims 7 to 8; and
une photodiode convertissant un signal optique en signal électrique, la photodiode étant placée en sortie dudit amplificateur optique et ledit modulateur étant connecté à la sortie de la photodiode.  a photodiode converting an optical signal into an electrical signal, the photodiode being placed at the output of said optical amplifier and said modulator being connected to the output of the photodiode.
10. Oscillateur optoélectronique selon la revendication 9, dans lequel ladite source laser, ledit amplificateur optique, ladite photodiode, ledit modulateur et ledit résonateur optique sont implantés sur une même puce optoélectronique. 10. The optoelectronic oscillator according to claim 9, wherein said laser source, said optical amplifier, said photodiode, said modulator and said optical resonator are implanted on the same optoelectronic chip.
11. Oscillateur optoélectronique selon la revendication 9, dans lequel ladite source laser, ledit amplificateur optique, ladite photodiode et ledit modulateur sont implantés sur une première puce optoélectronique, et ledit résonateur optique est implanté sur une seconde puce optique. 11. The optoelectronic oscillator according to claim 9, wherein said laser source, said optical amplifier, said photodiode and said modulator are implanted on a first optoelectronic chip, and said optical resonator is implanted on a second optical chip.
12. Oscillateur optoélectronique selon la revendication 11 dans lequel la seconde puce optique d'implantation est en silicium. 12. The optoelectronic oscillator according to claim 11, in which the second optical implantation chip is made of silicon.
13. Oscillateur optoélectronique selon l'une des revendications 10 et 11 dans lequel la première puce optoélectronique d'implantation est en semi-conducteur lll-V. 13. Optoelectronic oscillator according to one of claims 10 and 11 in which the first implantation optoelectronic chip is in III-V semiconductor.
EP19729767.4A 2018-06-14 2019-06-13 Locking of a laser on a resonator by means of an optical amplifier Pending EP3807960A1 (en)

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FR1800607A FR3082670B1 (en) 2018-06-14 2018-06-14 LOCKING A LASER TO A RESONATOR WITH THE HELP OF AN OPTICAL AMPLIFIER
PCT/EP2019/065530 WO2019238837A1 (en) 2018-06-14 2019-06-13 Locking of a laser on a resonator by means of an optical amplifier

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