EP2245710A2

EP2245710A2 - Method and device for stabilising the spectrum of a pulsed coherent optical source

Info

Publication number: EP2245710A2
Application number: EP09712936A
Authority: EP
Inventors: Steve Lecomte
Original assignee: Centre Suisse dElectronique et Microtechnique SA CSEM
Current assignee: Centre Suisse dElectronique et Microtechnique SA CSEM
Priority date: 2008-02-22
Filing date: 2009-02-20
Publication date: 2010-11-03
Also published as: WO2009103180A3; WO2009103180A2; US20100329287A1

Abstract

The invention relates to a method for stabilising the spectrum of a pulsed coherent optical source that comprises controlling the offset frequency ω₀ and the repetition rate ω_r in order to stabilise the frequencies of the comb lines constituting the optical spectrum thereof. The method comprises forming, from the pulsed coherent optical source (S₁), a beam that is directed onto a reference resonant optical cavity (CR), and using the signal generated by the reference resonant optical cavity (CR) for controlling the offset frequency ω₀ or the repetition rate ω_r, and probing, using a comb line, an atomic or molecular transition (AMT) in order to generate a driving signal for the repetition rate ω_r or the offset frequency ω₀.

Description

METHOD AND DEVICE FOR STABILIZING THE SPECTRUM OF A COHERENT PULSED OPTICAL SOURCE

The present invention relates to a method for stabilizing the spectrum of a pulsed coherent optical source according to which the offset frequency ωo and the repetition rate ω _{r are} slaved to slave the frequencies of the lines of the comb which make up its optical spectrum, as well as a device for implementing this method. Precise and stable oscillators are used in a good number of applications. Miniaturization and the reduction of the power consumption of such oscillators would be desirable in particular for portable or autonomous instruments. We have already proposed in "The miniature atomic clock - pre-production results" R. Lutwak et al., Proceedings EFTF07 a miniature clock based on microwave atomic transitions rather than on an optical transition. The choice of an optical transition makes it possible to increase the quality factor of the reference resonance and therefore the performances of the oscillator.

An optical clock requires the use of a mode-locked laser as a frequency divider to bring an optical frequency to a microwave frequency. This has been proposed by Prof. Theodore Hansch of the University of Munich and Max Planck Institute of Garching in Germany and Prof. John Hall of JILA, Boulder, Colorado, USA. The Nobel Prize in Physics was awarded to them in 2005 for this invention. A new generation of atomic clocks based on optical transitions is currently under development and has already demonstrated superior performance to the best atomic clocks based on microwave transitions. The frequency of each mode n of the optical spectrum emitted by a pulsed-mode laser is given by the following relation where n is an integer:

0> _op,, _n = n-ω _r + ω _o

In an optical clock, a continuous laser or pulsed laser mode is slaved to an optical transition. In order to be able to exploit the frequency stability obtained at the optical frequency, the mode-locked pulsed laser acts as a frequency divider. The repetition rate of the pulsed laser will have the same relative frequency stability as the optical frequency and it can therefore be processed electronically and serve as a frequency reference to the user. In order to exactly divide the optical frequency, the shifted frequency ω _o must be known and stabilized. The stabilization of the shifted frequency ω ₀ is obtained by means of a non-linear interferometer f-2f as shown schematically in Th. Udem et al., Optical Frequency Metrology, Nature 416 233-237, 2003)

The frequency of the repetition rate is typically between 75 MHz and 2 GHz for the lasers usually used in these applications. The principle that has just been described is precisely that of an optical atomic clock in which a continuous laser is slaved very stably on a reference atom or ion. In order to manufacture a miniature optical clock, the standard concept of pulsed laser stabilization with the non-linear interferometer f-2f does not seem very suitable for reasons of consumption and complexity. Indeed to achieve a nonlinear interferometer f-2f, an optical spectrum covering an octave is required. To generate this broad spectrum, short pulses and energy from a large laser and requiring several watts to several tens of watts of power are currently needed.

In order to overcome the power constraint of the optical pulses for the nonlinear interferometer, the stabilization of the offset frequency ω _o is done on an ultrastable external cavity. RJ Jones et al have already in "Precision stabilization of femtosecond lasers to high finesse optical cavities" Phys. Rev. A 69, 051803 (R) (2004), carried out a detailed comparison of two stabilization systems which leads to a new understanding of the optimum conditions and the limits for the stabilization of a cavity on the ability to transfer the frequency stability of the cavity in the microwave domain. The stability of the frequency comb is explored both in the optical domain and in the field of radio frequency. The stabilization of the repetition rate can be done either on an external cavity (which therefore creates a non-referenced oscillator) or on an atomic or molecular transition (atomic clock and referenced oscillator). In the case of RJ Jones et al., The repetition rate is stabilized on the resonant cavity. The resonant cavity inevitably has a drift of its resonance frequencies due to variations in its length (vibration and temperature essentially). In RJ Jones et al. mentioned above, the laser used is a titanium-sapphire type laser and is therefore incompatible with an electrical consumption of less than several watts. In order to obtain good frequency stability, the chosen laser produces short light pulses (less than 20 femtoseconds). The reference cavity has a length of 39.5cm and the propagation of the light beams is of free propagation type. This choice of components was motivated by the desire to test the limits of the frequency stability of the laser repetition rate on an external cavity without worrying about other aspects such as consumption and compactness.

The object of the present invention is to overcome, at least in part, the disadvantages of the aforementioned solutions.

To this end, the invention relates to a method for stabilizing the spectrum of a pulsed coherent optical source according to claim 1 or claim 2. It also relates to a device for implementing the method according to claim 1 as defined by claim 6 and a device for carrying out the method according to claim 2 as defined by claim 7. The essential difference between the scheme of Jones et al. and the present invention lies essentially in the medium and long-term stability of the microwave frequency generated by the device. In the case of the present invention, the repetition rate is stabilized on an atomic or molecular reference which intrinsically offers greater environmental stability.

The inventive concept adopted here also makes it possible to meet the requirements of miniaturization and considerable limitation of consumption which, with the precision sought, constituted two additional objectives of the present invention, making it possible to meet the conditions necessary for the production of a product. portable device of low power.

Among the key elements of the invention is the combination of a compact pulsed laser, low consumption and whose pulses are not necessarily ultrashort with a compact reference cavity and ultrastable. Depending on the forms of execution proposed, a transition of reference interrogated directly with the pulsed laser or indirectly by means of a continuous laser servo can also be used.

Advantageously, this device could be fiber or made in integrated optics with other types of waveguides. Currently such systems are bulky, they consume a lot of energy and they use technologies incompatible with a miniaturization of the device. For each physical subsystem, a list of relevant components to achieve the objectives of consumption and compactness is proposed. It is clear that any combination of these subsystems is possible to achieve the goals of consumption and compactness. The term physical subsystems includes elements such as laser, waveguides, reference cavity, atomic reference, photodetectors, lenses, phase modulators, optical filters, etc. The elements of the device that are not part of physical subsystems are: power electronics and control and stabilization electronics.

The compact and ultrastable resonant optical cavity is used at least for stabilizing the offset frequency of the optical spectrum of the pulsed light source. Different types of cavity are envisaged:

1. A solid standard made of ultra-low expansion glass to minimize thermal drift that causes a variation in its length. Very high reflectivity dielectric mirrors are provided on its faces to obtain a high fineness (or quality factor) of the resonator to increase the performance of the device. Such standards are described on the website www. generaloptics. corn 2. A standard as described above, but with cavity hollow in the air to limit the thermal drift of the standard (variation of its length) due to residual absorption of the light stored in the resonator cause of heating. The hollow cavity also offers the advantage of eliminating the dispersion due to the glass of the standard mentioned in point 1. Information relating to this standard can be found on the site mentioned in point 1. 3. An ultracompact ring-type resonator with high quality factor described in EP 1554618 B1.

4. An ultracompact optical resonator based on a mechanically structured material based on photonic bandgap effect (P. Pottier et al., Triangular and Hexagonal High Q-factor 2-D Photonic Bandgap Cavities on IH-V Suspended Membranes, J. Lightwave Technology, 2058 (1999).

The pulsed coherent optical source is compact and low consumption. It acts as a frequency divider from the optical domain to the microwave domain. The stable and pure microwave frequency produced by the complete arrangement is provided by the repetition rate of the stabilized pulsed optical source. In order to obtain a compact and low-consumption device, the following sources are possible: 1. Laser of multisection type emitting by the slice and quantum wells with saturable absorber DE 10322112 B4.

2. Laser of multisection type emitting by the slice and quantum dots with saturable absorber, Y. -C. Xin et al., Reconfigurable quantum dot monolithic passive multisection mode-locked laser, Optics Express 7623 (2007).

3. Surface Emitting and Vertical Cavity Laser

(VECSEL) with saturable absorber not integrated into the optical grain generating structure, D. Lorenser et al., Towards wafer-scale integration of high repetition rate passively mode-locked surface emitting semiconductor lasers, Appl. Phys. B 79,927 (2004).

4. Synchronous surface-emitted and external-cavity mode (MIXSEL) integrated laser, A. R. Bellancourt et al., First demonstration of a modelocked integrated external-cavity surface emitting laser (MIXSEL), CLEO 07, CWIl talk.

5. Fiber laser J. Chen et al., High repetition rate, low jitter, low intensity noise, fundamentally mode-locked 167 fs soliton Er-fiber laser, 32 1566 (2007).

6. Raman type laser, B. R: Koch et al., Mode-locked silicon evanescent lasers, Opt. Express 11225 (2007).

7. Diode-pumped solid-mode solid-mode laser with saturable semiconductor absorber (SESAM) L.

Krainer et al., Compact Nd: YVO ₄ lasers with repetition rate up to 160 GHz, IEEE J. Quantum Electr. 38 1331 (2002).

8. Continuous light pumped microtoroid resonator, US 2008285606 A1.

9. Fiber optic resonator pumped by continuous light, T. Braje et al. (http: //tf.nist.gov/cgi-bin/showpubs .pi)

In the proposed arrangements, one or more elements for spatially separating different colors from the spectrum are required. Here is a non-exhaustive list of compact components compatible with the integrated optical approach that can perform this task (non-exhaustive list): 1. Planar selective network (AWG), www.jdsu.com.

2. Interleaver, www.jdsu.com.

3. Glass blade with dielectric coating whose reflectivity varies with wavelength.

4. Diffraction grating. 5. Resonant optical cavity with low fineness and wide free spectral range. In some proposed arrangements, a phase modulator is required to achieve Pound-Drever-Hall type servo, RWP Drever et al., Laser phase and frequency stabilization using an optical resonator, Appl. Phys. B, 97 (1983). In order to have a compact arrangement, the following components can be used (non-exhaustive list):

1. IBM, W. M. J. Green et al., Ultra-compact-low RF power, 10 Gb / s silicon Mach-Zehnder modulator, Opt. Exp.15 17106 (2007)

2. Intel www.intel.com

3. JDSU www.jdsu.com

To ensure the compactness of all the arrangements described, fiber optic waveguides or channel waveguides (made of different materials such as silicon oxide, silicon nitride, silicon, polymers, etc. on the domain: http://www.crcpress.com/shoppingcart/products/product detail.asp? sku = DK3157) can be used. The technologies associated with channel waveguides also make it possible to produce an optical chip.

These waveguides also make it possible to ensure the coupling and decoupling of the laser beam of the different elements composing the arrangements.

One of the peculiarities of this invention is to be able to overcome a very wide optical spectrum necessary (typically an octave) to be able to control in a customary way the offset frequency of the pulsed light source. Nevertheless, a nonlinear optical element allowing a spectral broadening makes it possible to improve the performances of the system. Indeed according to RJ Jones et al. mentioned above, the quality of the stabilization of the shifted frequency, thus the stability of the repetition rate ω _r , increases with the spectral width used according to the relation: ω _C between / (2π-Δf)

Where ω _center is the _center frequency of the optical frequency interval Δf considered (Δf = ω _b -ω _a ) in the proposed arrangements. In order to increase the spectral width of the source (without however reaching the octave), the use of an optically nonlinear element is required. This element must be placed directly after the pulsed light source in order to benefit from the maximum power of the pulses and thus to widen the spectrum to the maximum. Different types of non-linear elements are possible and compatible with light-guiding technologies such as optical fiber or channel waveguide:

1. Highly non-linear optical fiber of standard singlemode type www.ofs.com or photonic crystal type http://www.crystal-fibre.com/.

2. Waveguide with conical geometry.

Note that the nonlinear element has not been shown in the attached diagrams. The continuous laser stabilized on an atomic or molecular optical reference must be of narrow spectral width. In arrangements where such a laser is required, the microwave signal generated by the device will be designed to have the following effects: 1. The spectral width of the continuous laser will have an effect on the spectral purity of the microwave signal generated by the device (noise phase).

2. Medium and long-term frequency stability will have an effect on the medium and long-term frequency stability of the microwave source.

Such a laser can be realized with the following technologies: 1. Distributed reaction distributed DFB type semiconductor laser or Bragg reflector distributed laser DBR.

2. Fabry-Perot type semiconductor laser in extended cavity. 3. Toroidal resonator type laser L. Yang et al., A 4- Hz fundamental linewidth on-chip microlaser, CLEO 07, talk CMR2 4. Fiber laser www.np-photonics.com

The accompanying drawings illustrate, schematically and by way of example, four embodiments of devices for implementing the methods that are the subject of the present invention.

Figure 1 is a block diagram of a first embodiment; Figure IA is a partial view of a variant of the diagram of Figure 1; Fig. 2 is a block diagram of a second embodiment; Fig. 3 is a block diagram of a third embodiment; Figure 4 is a block diagram of a fourth embodiment.

The block diagram of FIG. 1 comprises a pulsed coherent light source S ₁ at the output of which is a separator plate L ₃ or an element of interference filter type or a Fabry-Perot resonator, or an interleaver for spectral separation. . The separator plate L ₃ directs the light of the source Si on a phase modulator MP at the output of which a second separator plate L ₃ directs the light towards a reference cavity CR to stabilize the offset frequency C _{0 O} or the repetition rate ω _r of the optical source Si by the Pound-Drever-HaIl method. The optical signal coming from the reference cavity CR is directed by the second splitter plate to a photodetector PDi through an optional bandpass filter F _pb to stabilize ω _r (Figure 1) or to two photodetectors PD _IA and PD _IB through a planar AWG selective grating to stabilize (Oo as The electrical signals from PD _iA and PDi _B are subtracted by a differential amplifier A and their difference is used as an error signal to act on the optical source Si and to stabilize the shifted frequency CO.sub.o. where there is only one photodetector PDi, the electrical signal is brought back to the optical source Si to stabilize repetition rate ω _r .

A second continuous coherent light source S ₂ forms a continuous beam directed on an atomic or molecular transition TAM whose signal is used to slave the continuous coherent optical source S ₂ . The frequency difference between a mode of the pulsed optical beam spectrum derived from the pulsed optical source Si and the continuous beam coming from the continuous optical source S ₂ is also detected for controlling the repetition rate ω _r or the offset frequency ωo

For this purpose, two splitter blades L _s are placed at the output of the optical source S ₂ . Advantageously, a band-pass filter F _pb is placed in front of a photodetector PD ₂ , the output of which is connected to the pulsed optical source Si. The electrical signal leaving the photodetector serves to slave ω _r or ωo.

The output of the atomic or molecular transition is directed on a photodetector PD ₃ whose electrical signal is transmitted to the continuous optical source S ₂ to control the optical frequency.

The embodiment illustrated by the diagram of FIG. 2 differs from that of the diagram of FIG. This is because the reference cavity CR slaves the offset frequency ω ₀ or the repetition rate ω _r by the intensity of the light signal transmitted by the reference cavity CR, as shown in the diagram, or the PDI photodetector. is located at the output of the reference cavity CR, contrary to Figure 1. Advantageously, a bandpass filter F _pb or an AWG planar selective network or an interleaver is disposed between the reference cavity and the photodetector PDi. In the case where an AWG plane selective grating is used, the variant of the partial diagram of FIG. 1A applies to the processing of the light signal transmitted by the reference cavity CR of FIG. 2.

The remainder of the device of FIG. 2 is completely similar to that of FIG. 1 and reference can be made to the corresponding description of FIG. 1, which applies to FIG. 2.

The diagram of FIG. 3 is very close to that of FIG. 1, but in this case only the pulsed coherent light source Si is used. As in the case of FIG. 1, the optical signal coming from the reference cavity CR is directed by the second splitter plate towards a photodetector PDi through an optional bandpass filter F _pb to stabilize the repetition rate ω _r by the Pound-Drever-Hall method or, as illustrated by the variant of FIG. 1A, to two PDi _A and PDi _B photodetectors through a planar AWG selective grating for stabilizing CDo. The separator plate L ₃ , which may be an interference filter type element or a Fabry-Perot resonator or an interleaver, located at the output of the pulsed optical source Si directs and selects a line of the comb of the optical spectrum on the pass filter. band F _pb located between the separating plate L ₃ and the atomic or molecular transition TAM. The comb line probes the atomic or molecular transition and the electrical absorption signal from the photodetector PD _{3 is} used to enslave the repetition rate ω _r or the offset frequency ω ₀ of the source Si.

The diagram of FIG. 4 is very similar to that of FIG. 2 and differs essentially only in that it uses only a pulsed light source Si. As in the case of FIG. intensity transmitted by the reference cavity CR is directed towards a photodetector PDi through an optional bandpass filter F _pb to stabilize ω _r or, as illustrated by the variant of FIG. 1A, to two photodetectors PD _iA and PDi _B to through an AWG planar selective grating for stabilizing ωo- As in the case of FIG. 3, the separating plate L _s , which may be an element of interference filter type or a Fabry-Perot resonator or an interleaver, situated at the output of FIG. the pulsed optical source S1 directs and selects a line of the comb of the optical spectrum on the bandpass filter F _pb located between the splitter plate L ₃ and the atomic or molecular transition TAM. The comb line probes the atomic or molecular transition and the electrical absorption signal from the photodetector PD ₃ makes it possible to control the repetition rate ω _r or the offset frequency ωo of the source Si.

With regard to the technical characteristics of the components used in the diagrams of FIGS. 1 to 4, the following values may be given by way of example:

In the case of a monolithic CR reference cavity made of glass, the highly reflective dielectric treatment of the mirrors is realized to obtain a reflectivity> 99%. Preferably the treatment is carried out with a compensation of the dispersion of the glass. The length of the cavity is between 100 mm and 1.0 mm, corresponding to a field spectral free between 1 and 100 GHz respectively. The glass is ultra-low expansion type (ULE).

In the case of the reference cavity CR with air gap and shim, the glass is also ultra-low expansion type (ULE). The mirrors are treated to have a reflectivity> 99%, if possible the treatment is intended to have a zero dispersion on 100-200 nm, for a wavelength of 1550 nm and length between 150 mm and 1.5 mm corresponding at a free spectral range between 1 and 100 GHz respectively.

For the pulsed light source, compact and low consumption, depending on the type of laser, the wavelength is between 750 nm and 1600 nm. The duration of the pulses is between 100 fs and 10 ps. The spectral width of the pulses is between 0.25 nm and 25 nm for a wavelength of 1550 nm. The average optical power is 1 to 100 mW, the repetition rate is between 1 and 100 GHz. The consumption is 10 mW <30OmW <1000 mW. For the microtoroxid resonator pumped by continuous light, the wavelength is 1550 nm, the spectral width is 10 to 300 nm, the optical power is 10 mW <150 mW <200 mW, free spectral range is 10 GHz and 1000 GHz. The consumption is 30 mW <150 mW <600 mW.

The compact element making it possible to spatially separate the different spectral components is a planar selective grating (AWG), or an interleaver whose free spectral range is between 50 and 100 GHz. The cell and atomic or molecular reference referred to above as the atomic or molecular transition contains the reference in gaseous form. It may be a quartz or pyrex cell with a size typically between 5 and 10 mm in length in the direction of propagation of the laser beam and between 5 and 10 mm in diameter.

It can also be a MEMS type cell with silicon or pyrex substrate and two windows welded pyrex on either side of the substrate. A hole typically of 1 mm is provided in the center of the substrate 1 to a few mm thick defining the length of the optical path. The lateral dimension of the cell is 2 to 5 mm side.

It can still be a microstructured hollow optical fiber cell. A reference gas is trapped in the heart of the hollow fiber (core diameter <20 μm). The length of the fiber is between 10 and 1000 mm.

The reference atom or molecule is either an alkaline vapor, typically of rubidium or cesium, or an acetylene gas, hydrogen cyanide, iodine (I ₂ ), water vapor, especially.

As for the continuous coherent optical source, it is a laser whose power consumption is 10 <50 <200 mW, the optical power is 3 <15 <80 mW, the spectral width <1 MHz and the wavelength depending on the atomic or molecular reference is between 750 and 1600 nm.

In the diagrams of FIGS. 1 to 4, the propagation of the beams can be either in optical fibers or in waveguides to further limit the dimensions. To finally reduce the dimensions to the maximum, all these elements can be realized in integrated optics.

A volume and consumption assessment has been drawn up with regard to the scheme of FIG. 1. A comparison has been made between the volume and consumption of this device and a device of the state of the art, in which the occurrence of RJ Jones et al. mentioned above which constitutes the closest state of the art. The chosen dimensions of the components of FIG. 1 are as follows:

Pulsed laser Si: length 1 mm, 0 0,5 mm

Continuous laser S ₂ : length 1 mm, 0 0,5 mm

MP phase modulator: length 1 mm, 0 1 mm

AWG planar grating: 6x6 mm

Resonant cavity CR: 10 mm, 0 3 mm

PD photodetectors: 0.5 mm, 0.5 mm

Atomic / molecular transition cell TAM: 1x1 mm

Table 1: Volume / consumption balance of the Jones et al. * Source of voltage and current not included.

Table 2: Volume / consumption balance of the diagram of Figure 1. * Source of voltage or current not included.

The volume and consumption values do not take into account the control and power electronics required by the device. The numbers give a lower limit achievable.

There is a reduction in volume by a factor of 100,000 and a reduction in consumption by a factor of 100 with elements and technologies available to date.

Claims

1. A method for stabilizing the spectrum of a pulsed coherent optical source according to which the shifted frequency ω 0 and the repetition rate ω _{r are} slaved to slave the frequencies of the lines of the comb which make up its optical spectrum, characterized in that a beam is formed from the pulsed coherent optical source and directed to a reference resonant optical cavity and the signal formed by the reference resonant optical cavity is used to control the shifted frequency ω 0 or the repetition rate ω _r and is probing by means of a comb line an atomic or molecular transition to form a servo signal of the repetition rate ω _r or the offset frequency ωo.

2. A method for stabilizing the spectrum of a pulsed coherent optical source according to which the offset frequency ωo and the repetition rate ω _{r are} slaved to slave the frequencies of the comb lines which make up its optical spectrum, characterized in that a pulsed beam which is directed on a reference resonant optical cavity is formed from the pulsed coherent optical source and the signal formed by the reference resonant cavity is used to control the shifted frequency ωo or the repetition rate ω _r and forming from a continuous coherent optical source a continuous beam which is directed on an atomic or molecular transition whose signal is used to enslave the continuous coherent optical source and detects the frequency difference between the optical beams pulsed and continuous to enslave the repetition rate ω _r or the offset frequency ωo.

3. Method according to one of claims 1 and 2 wherein spatially separates different colors of the spectrum of the optical comb.

4. Method according to one of claims 1 and 2, wherein the frequency of the optical domain of the pulsed coherent optical source is divided into the microwave domain by the repetition rate ω _r of the stabilized pulsed coherent optical source.

5. Method according to one of claims 1 and 2, wherein the stabilized frequency offset ω ₀ or the repetition rate ω _r using a phase modulator by a servo-type Pound-Drever-Hall.

6. Device for implementing the method according to claim 1, comprising a pulsed coherent light source (Si) with a volume less than 10. ICT ⁴ cm ³ and a power of less than 1 W and a resonant cavity (CR) of ultrastable reference volume less than 0.2 cm ³ .

7. Device for implementing the method according to claim 2, comprising a pulsed coherent light source (Si) with a volume of less than 10.10 ^-4 cm ³ and a power of less than 1 W, a reference resonant cavity (CR). ultrastable volume less than 0.2 cm ³ and a continuous coherent light source (S ₂ ) volume less than 10.10 ^{~ 4} cm ³ and a power less than 0.5 W.

8. Device according to one of claims 6 and 7 comprising at least one optical element (L ₃ ) for separating different colors of the optical spectrum of the pulsed coherent optical source (Si).

9. Device according to claim 8 wherein the optical element (L ₃ ) for separating different colors of the optical spectrum of the pulsed coherent optical source (Si) is chosen from among the following elements: planar selective grating, interleaver, glass slide with dielectric coating whose reflectivity varies as a function of the wavelength, diffraction grating, resonant optical cavity with low fineness and wide free spectral range.

10. Device according to one of claims 6 and 7, wherein the source of pulsed coherent light (Si) is selected from the following sources: laser multisection emitting by the wafer and quantum wells with saturable absorber, multisection laser emitting by the slice and quantum dots with saturable absorber, vertical cavity surface-emitting laser (VECSEL) with saturable absorber not integrated with the optical grain generating structure, an external surface-emitted synchronized mode external cavity laser (MIXSEL) ), a fiber laser, a Raman laser, a solid state laser and a semiconductor saturable absorber (SESAM) blocked mode, a continuous light pumped microtoroid resonator, a light pumped optical fiber resonator keep on going.

11. Device according to one of claims 6 and 7, wherein the resonant cavity (CR) ultrastable reference is selected from the following elements: monolithic glass standard ultra-low expansion ULE whose faces include dielectric mirrors with a reflectivity of greater than 99%, the same glass standard but with a hollow air cavity, an ultracompact resonator of the type having a quality factor greater than 10 ⁶ , an ultracompact optical resonator made of a mechanically structured material and based on the effect of photonic band gap.

12. Device according to one of claims 6-11, wherein the various elements of which it is composed are connected by optical fiber waveguides or channel waveguides made of materials chosen from the following materials: silicon, silicon nitride, silicon, polymers or equivalent, to ensure the coupling and the decoupling of the laser beam between these different elements.

13. Device according to one of claims 6-12, wherein an optically nonlinear spectral broadening element is placed directly at the output of the pulsed coherent optical source, this spectral broadening element being selected from the following components: Highly nonlinear optical fiber of standard singlode type or photonic crystal type, waveguide with conical geometry.

14. Device according to one of claims 7-13, wherein the spectral width of the continuous coherent optical source (S ₂ ) is less than 1 MHz and is formed by one of the following laser distributed DFB type semiconductor laser or DBR distributed laser Bragg reflector, extended-cavity Fabry-Perot type semiconductor laser, toroidal resonator type laser, fiber laser.

15. Device according to one of claims 6 to 14 wherein at least a portion of the optical components are made in integrated optics.