A photonic system and method for frequency conversion of laser pumps

Abstract

The invention relates to a photonic system and method for frequency conversions of incoming laser pumps comprising a first laser source generating a first laser pump, a second laser source generating a second laser pump, a first waveguide, optional a second waveguide, an optical combiner and an input coupler, wherein the waveguides and the optical combiners are integrated into a compact platform, the first waveguide frequency convert the first and second laser pumps to generate a frequency converted signal. Phase shifting means are arranged to phase shift one or more of the first laser pump, the second laser pump and / or the frequency converted signal. The first waveguide generates an output signal, which is a modulated frequency converted signal by optical interaction in the first waveguides between the pumps and signals progressing in the first waveguide.

Description

[0001]83690PC01 1A PHOTONIC SYSTEM AND METHOD FREQUENCY CONVERSION OF LASERPUMPS FIELD OF THE INVENTIONThe present invention relates to a photonic system and method for frequencyconversion of incoming laser pumps which utilizes phase modulation to generateand modulate infrared light.BACKGROUND OF THE INVENTIONIn the field of optics, lasers are commonly used as a source of light beams orpumps due to their high intensity and coherence. Waveguides and opticalcombiners, such as multiplexers, are often employed to direct and manipulatelaser beams. Frequency conversion techniques, such as difference frequencygeneration (DFG), sum frequency generation (SFG), second harmonic generation(SHG) or spontaneous parametric down conversion (SPDC) are used to convertthe frequency of the laser beams to a desired frequency.DFG is a nonlinear optical process where two input beams or pumps with differentfrequencies interact within a nonlinear material to generate a signal at the difference of the two frequencies. On the other hand, SFG is a process where two input pumps combine in a nonlinear optical medium to form an output signal atthe sum of the input frequencies. SHG is a special case of SFG in which the twoinput pumps with the same frequency, therefore combining to generate an output signal at the double frequency of either of input pumps. SPDC is a special case of DFG in which the two input pumps with the same frequency, or a single inputpump, spontaneously generate two outputs with their sum of frequencies equal tothe input pump(s).The field of photonics has seen significant advancements, particularly in the areaof laser light manipulation on photonic chips, where optical on-chip componentsguide and manipulate light. Yet, current frequency conversion systems typicallyrely on free space optical setups and bulk nonlinear crystals.Such systems face several challenges. The free space optical setups in which thepump laser beams are coupled into bulk nonlinear crystal require significant space 83690PC01 2 on the order of 50cm x 50 cm x and often more. This limits their applicability in settings where space is at a premium. This size issue also impacts the system’s versatility and adaptability to various applications, making them impracticable to take out of the laboratory. Additionally, a primary issue is the difficulty in providing phase-locked generationby controlling the phase of the two laser pumps. This challenge can lead toinefficiencies and inaccuracies in the frequency conversion process. Furthermore, the current systems lack integration. The optical combiners, waveguides, and means to control the phase of the laser waves are typically separate components. This lack of integration not only contributes to the overall size of the system but also complicates the assembly and maintenance process,leading to potential errors or malfunctions.Therefore, there is a need for more compact systems. Such systems wouldaddress the aforementioned challenges by reducing the overall size of the system, improving its efficiency, simplifying its assembly and maintenance, and enhancing the accuracy of the phase-locked generation. This invention aims to fulfil this need and provide further related advantages. Hence, an improved photonic system and method for modulation and frequencyconversion would be advantageous, and in particular, a more compact photonicsystem and method for modulating the frequency conversion process would beadvantageous. OBJECT OF THE INVENTION It may be seen as an object of the present invention to provide a photonic systemand method for modulating the frequency conversion process that solves theabove-mentioned problems of the prior art by being compact and integrated. It may further be seen as an object of the present invention to provide a photonicsystem and method comprising phase-shifting means to obtain a phase change ofone or more pump(s) or signal(s) to optimize optical interactions between thepump(s) and signal(s) in a waveguide. 83690PC01 3 It is a further object of the present invention to provide an alternative to the prior art. SUMMARY OF THE INVENTIONThus, the above-described object and several other objects are intended to beobtained in a first aspect of the invention by providing a photonic system forfrequency conversion of incoming laser pump(s), the photonic system is comprising: -a first laser source, which is arranged to generate a first laser pumpat a first frequency f1, -a second laser source, which is arranged to generate a second laserpump at a second frequency f2, -a first waveguide, which is nonlinear comprising a second-ordernonlinear optical susceptibility material for frequency conversion, -an optical combiner, which is arranged to combine the laser pumpsfrom the first laser source and the second laser source, and direct the combined pumps into the first waveguide, and -an input coupler to couple the first laser pump and the second laserpump, wherein -the first waveguide and the optical combiner are integrated into acompact platform, -the first waveguide is arranged to frequency convert the first laserpump and the second laser pump to generate a frequency converted signal of a third frequency f3, -phase shifting means are arranged to generate one or more phase-shifted signal(s) by: ^phase shift the first laser pump and / or the second laser pumpbefore the first laser pump and / or the second laser pump enters the optical combiner, and / or ^phase shift the first laser pump after entering the firstwaveguide, the second laser pump after entering the first waveguide and / or the frequency converted signal, and 83690PC01 4 -the first waveguide is to generate an output signal, theoutput signal is a modulated frequency converted signal, ^where the modulated frequency converted signal is formedwithin the first waveguide by optical interaction between thephase-shifted signal(s) and one, or more, of the first laser pump(s), the second laser pump and / or the frequencyconverted signal.The photonic system is an optical device that provides phased-locked generation,amplification and / or modulation of a frequency converted signal by carefullymodulating the phase of the first laser pump, the phase of the second laser pumpand / or the phase of the frequency converted signal. The first laser source and the second laser source may be laser diodes, or anyother kind of emitting laser pump at the required wavelength.The optical combiners, waveguides, and phase shifting means to control the phaseof the laser pumps and / or the frequency converted signal are integrated on acompact platform, which preferably may be a photonic chip.The words pump and signal in this application both refer to beams of light comprising a certain center wavelength. The distinction between pump and signal is that the pump are sources of light in-coupled at the input, while the signal isgenerated from the pump sources and is the desired entity at the output.Occasionally the word “beam” is used in this application instead of pump or signalor to cover both pump and signal, so a beam may be a pump or a signal.The optical combiner is a device which combines the pumps from two or morelaser sources and leads the pumps into the first waveguide. Preferably, the opticalcombiner may be a multiplexer. The multiplexer is preferably made of the samematerial as the compact platform. Although the material may be silicon nitride(SiN), but other materials can also be applied, for instance aluminum nitride(AlN), and / or lithium niobate (LN) and / or hafnium pentoxide (HfO5). The materialsare transparent for all wavelengths involved. 83690PC01 5The input coupler is a laser-to-chip receiving the laser pumps andcoupling the laser pumps into the photonic chip.The first waveguides may be fabricated in III-V semiconductor materials withlarge second-order nonlinear optical susceptibility, preferably the nonlinearwaveguide is fabricated in or based on GaP, InGaP, GaAs, AlGaAs, InP, InGaAsP,lithium niobate or another binary, tertiary or quaternary etc. III-V semiconductormaterial, with high second-order nonlinear optical susceptibility. Materials with ahigh refractive index and large nonlinear second-order susceptibility are used, whilethe materials are transparent at the relevant wavelengths. The first waveguide isnonlinear comprising a nonvanishing second-order nonlinear optical susceptibility material for frequency conversion.To further improve upon the conversion efficiency the compact platform may be aphotonic chip with embedded photonic integrated circuit(s) (PIC(s)) which allowsfor a compact, robust, and miniature system, and has been shown to improve thenonlinear conversion due to tighter guiding of the modes, allowing for a higher conversion efficiency.The first waveguide and the optical combiner are integrated into a compactplatform, the compact platform may be entirely a photonic chip with embeddedPIC(s) in which the optical combiner, the couplers, and the nonlinear waveguidesare structurally integrated. Structural integration is to be understood as the structural integrated components are grown and fabricated as part of the compact platform, the component being made of the same material as the compact platform, or the structural integrated components are bonded to the compactplatform. Typically, the compact platform may be a photonic chip made of silicon,silicon nitride and / or silica, and the nonlinear material.The phase shifting means may be integrated into the compact platform or mayalternatively be attached to the compact platform.Phase shifting means are related to the complex exponential with a phaseargument, not to be misinterpreted as the phase matching condition, whichhappens on the basis of the wavenumbers. 83690PC01 6The substrate of the compact platform and its nonlinear material is typically eithergrown on top of each other or the nonlinear material is bonded onto the substrateof the compact platform. It may then be further processed to fabricate thewaveguide in the nonlinear material by etching. The etching can form the waveguide by removing materials both on top, but also beneath (under-etching). That the compact platform is compact is to be understood that the components are placed close to each other and are in a fixed position relative to each other so that the platform is of a minimal size, while functioning at the intendedperformance standard and being practicable to operate. The typical size of thephotonic chip is a few millimetres in length and width.An optical phase modulator is a device that varies the phase of a light beam inresponse to an electrical signal. The electrical signal may be generated by a phaseshift controller. In the phase modulation, the characteristics of the electrical signaldictate the phase of the light beam. This characteristics of the electrical signalmay be amplitude of the signal or frequency. As the characteristics of theelectrical signal change, the phase of the light beam changes correspondinglygenerating the phase-shifted signal.‘Modulation’ refers to any controlled change of the first or second laser pump orthe frequency converted signal by changing the phase of the beam.The modulated frequency converted signal is obtained by the frequency convertedsignal having been phase shifted then to subsequently further stimulate thefrequency conversion process by optically interacting with the first or second laserpumps in the first waveguide. The modulated frequency converted signal mayalso be obtained by the frequency converted signal having optically interactedwith the phase shifted first or second laser pumps in the first waveguide. Themodulated frequency converted signal becomes the output signal when themodulated frequency converted signal leaves the waveguide through the outputport. 83690PC01 7Passing through the first the frequency converted signal is graduallychanged to the modulated frequency converted signal during optical interactionwith the different beams moving within the first waveguide.In the case of spontaneous parametric down-conversion (SPDC) two frequencyconverted signals with frequency f3 and f4 may be generated when the first waveguide is frequency converting the first laser pump and the second laser pump. Optical interaction, as used herein, refers to the process by which two or morelaser pumps and / or frequency converted signals interact within the firstwaveguide. This optical interaction can result in frequency conversion processesleading to amplitude enhancement or attenuation of one or more of theinteracting pumps and signals. The specific outcomes of the optical interaction depend on the properties of the first waveguide, the characteristics of the laser pumps, and the nature of the nonlinear interaction. This interaction is facilitated by the nonlinear optical properties of the medium in which the first waveguide is constructed, leading to potential applications in optical signal processing, light generation, and other areas of photonics. The invention requires finding the right material and dimensions for the nonlinear waveguide and selecting the right laser sources and multiplexer and to find the right temperature to achieve the laser pumps to optical interact in the nonlinear waveguide to facilitate the desired frequency conversion.The output signal is a modulated frequency converted signal with its frequencygenerated by frequency conversion of the laser pump from the first laser sourceand the laser pump from the second laser source and optical interaction betweenthe pumps and frequency converted signal. The first laser pump from the firstlaser source and / or the second laser pump from the second laser source may bephase shifted before the frequency conversion.Alternatively, the frequency converted signal may be phase shifted after thefrequency conversion, which hence will be recombined in the first waveguide to modulate the output signal based on the phase-shift. 83690PC01 8The invention is particularly, but not exclusively, advantageous for obtaining aphotonic system and method comprising phase-shifting means to obtain phase-shifting of one or more beam(s) to optimize optical interactions between thebeam(s) in the first waveguide obtaining a frequency converted output signal of ahigh amplitude by adjusting the phase of one or more of the first laser pump, thesecond laser pump and / or the frequency converted signal to optimize the opticalinteraction in the first wave guide. According to an embodiment, the phase shifting means are a first phase modulator, a second optical phase modulator and / or a second waveguide. The optical phase modulator is able to phase shift by actively phase modulating the first laser pump, the second laser pump and / or the frequency converted signal. According to an embodiment, the phase shifting means are a first phase modulator.The first phase modulator is positioned to phase shift the first laser pump and / orthe second laser pump before the first and second laser pump enters the optical combiner. According to an embodiment, the phase shifting means are a second optical phase modulator and / or a second waveguide.The second waveguide and possibly the second optical phase modulator arepositioned so that the first laser pump, the second laser pump and / or a frequencyconverted signal may enter the second waveguide by evanescent coupling afterthe first laser pump and the second laser pump have entered the first waveguide.In the second waveguide the incoming beams are phase shifted either by thesecond waveguide itself or by a second optical phase modulator placed in or at the second waveguide. The phase shifted signal is then returned by the evanescent coupler to the first waveguide. 83690PC01 9 If the incoming beams are phase by the second waveguide itself, it is thelength and refractive index of the second waveguide that causes the phase shift,as the length may cause the incoming beams may be returned to the firstwaveguide offset and thereby phase shifted relative to the first laser, pump, thesecond laser pump or the frequency converted signal.The optical phase modulator is able to phase shift by actively phase modulatingthe first laser pump, the second laser pump and / or the frequency convertedsignal.Phase modulation may be performed by various methods, all of which introduce aphase shift of a given light beam by controlling a physical mechanism. Onephysical mechanism is the electrical-optical effect, where an applied voltageacross the second waveguide changes the refractive index, which resultingly willintroduce a phase shift related to the magnitude of the applied voltage. A secondphysical mechanism is a thermal-optical effect in which the temperature of thewaveguide is adjusted locally, which resultingly will alter the refractive indexlocally and hence introduce a phase shift. A third physical mechanism iscontrolling the optical path length that the optical beam covers by straining thewaveguide by applying stress on the waveguide. A fourth physical mechanism iscontrolling the amplitude of the lasers, or including a cavity with a high intense field that will trigger third-order nonlinear effects also known as the Kerr effect and cross-phase modulation which changes the effective refractive index and caninduce a phase-shift. These physical mechanisms may be applied to the first laserpump, the second laser pump and / or the frequency converted signal.The second waveguide may be fabricated in the same material as the first waveguide, but may alternatively be fabricated in other materials, which may notbe nonlinear. Therefore, the second waveguide may be a nonlinear waveguide, orit may not be a nonlinear waveguide. The second waveguide may be a resonatoror may be coupled to a resonator for having intense fields for Kerr effects, usingthe Kerr effect to induce phase-shift. 83690PC01 10 According to an embodiment, means are arranged to phase shiftthe first laser pump, the second laser pump and / or the frequency converted signalwithin the second waveguide to generate phase-shifted signal(s). According to an embodiment, -an evanescent coupler is arranged to couple one, or more, of thebeams from the first waveguide into the second waveguide as incoming beam(s), where the incoming beam(s) from the first waveguide is / are: a. the first laser pump,b. the second laser pump, and / orc. a frequency converted signal which is generated byfrequency conversion of the first laser pump and thesecond laser pump, and -the evanescent coupler is further arranged to couple the phase-shifted signal(s) from the second waveguide into the first waveguide. The second waveguide may be arranged to phase shift the incoming beam(s) bythe evanescent coupler which may be a directional optical coupler which transfersbeams between the waveguides. The evanescent coupler transfers beams fromthe first linear waveguide to the second linear waveguide, or from the second linear waveguide to the first linear waveguide. The evanescent coupler may be implemented by the first and second waveguidesand are sufficiently closely spaced that beams are optically transferred betweenthem by evanescent coupling. In the disclosed optical system, three distinct light beams progress in a first waveguide. The light beams may be the first laser pump, the second laser pump or the frequency converted signals. One, or more, of these light beams arepartially transferred to the second waveguide through the evanescent coupler.The light beam transferred to the second waveguide is the incoming beam. 83690PC01 11The specific light beams(s) from the part that is transferred is determinedby the dimensions, the material of the second waveguide and gap between thefirst and second waveguide. The evanescent coupler facilitates the selectiveinteraction between the beams in the first waveguide and the second waveguide, enabling the transfer of a fraction of the desired light beam. This system allows for precise control over the propagation of the light beams, with the unique design of the second waveguide playing a decisive role in the selection of the light beams to be transferred. This opens new possibilities for efficient and flexible optical signal processing, with potential applications in various fields of photonics, including telecommunications, data processing, and sensing.According to an embodiment, the first waveguide is further arranged so that thephase-shifted signal(s) optically interacts with the first laser pump, the secondlaser pump and / or the frequency converted signal to generate a modulatedfrequency converted signal with the same frequency as the frequency convertedsignal. According to an embodiment, the phase shifting means arranged to phase shift the first laser pump (6), the second laser pump (7) and / or the frequency converted signal (10) within the second waveguide (11) comprises a second optical phase modulator (12’’).According to an embodiment, the first optical phase modulator is arranged tophase shift the first laser pump and / or the second laser pump subsequent tobeing in-coupled and before entering the optical combiner.In this embodiment an optical phase modulator is placed before the opticalcombiner in the input coupler, but the optical phase modulator is placed on the compact platform, so the pump is in-coupled to the compact platform before it isphase shifted. It is possible to have phase modulators both before the combinerand in the second waveguide. According to an embodiment each optical phase modulator comprises a phaseshift controller arranged to control the magnitude of the phase shift. 83690PC01 12The phase shift controller is an electrical signal. In the phasemodulation, the characteristics of the electrical signal dictate the phase of theinput signal.According to an embodiment the phase shift controller (s) is / are adapted to beadjusted manually or by a computer interface.According to an embodiment the phase shift controller (s) is / are adapted to beadjusted based on a feedback signal. The photonic system may comprise an additional feedback mechanism, where themodulated frequency converted signal is transmitted as a feedback signal to thephase shift controller. The phase shift controller then may adjust the phase shiftapplied to a given optical beam based on the feedback signal, thereby eitherenhancing or diminishing the phase shifting physical mechanism. Phase modulation is performed by adjusting the electrical signal transmitted fromthe phase shift controller to the optical phase modulator which may be adjustedeither manually or by a computer interface. According to an embodiment arranging the second waveguide to phase shift the incoming beam(s) comprises adapting the refractive index of the second waveguide. The refractive index of the second waveguide may be adapted by the electrical-optical-effect and / or thermal-optical effect, adapting the length of the waveguideby a stress-strain effect or by the Kerr effect.According to an embodiment the compact platform comprises a photonic chip withembedded integrated circuit(s) (PIC(s)).According to an embodiment the frequency conversion is performed by differencefrequency generation (DFG), or by sum of frequency generation (SFG), or bysecond harmonic generation (SHG), or by spontaneous parametric down conversion (SPDC). 83690PC01 13 According to an embodiment the first waveguide comprises an input end, wherethe laser pumps enter the first waveguide, and a first reflector is arranged at theinput end of the first waveguide. The first reflector may be specifically targeted to only reflect the signal wavelength. According to an embodiment the first reflector is arranged to reflect the phase- shifted signal(s) received from the second waveguide. When the phase shifted signal enters the first waveguide from the second waveguide the phase shifted signal may be moving the opposite direction than the laser pumps, moving towards the input end, therefore, a first reflector may bepositioned at the input end to reflect the phase shifted signal, so it moves in thesame direction as the laser pumps. According to an embodiment the second waveguide comprises a remote end oppositely placed from an input end, where the input end is the end where the incoming beam enters the second waveguide, a second reflector is mounted at the remote end of the second waveguide, and the second reflector is arranged to reflect beams progressing within the second waveguide back through the second waveguide to be coupled back into the first waveguide.When the incoming beam enters the second waveguide, it may travel from theinput end towards the remote end. At the remote end a reflector is positioned toreturn the incoming beam back through the second waveguide such that thephase-shifted signal is returned to the first waveguide.According to an embodiment the optical combiner is a multiplexer, being arrangedto combine the first laser pump from the first laser source with the second laserpump from the second laser source.According to an embodiment the evanescent coupler is a directional coupler. 83690PC01 14According to an embodiment the the photonic chip comprising photonicintegrated circuits (PICs) preferably is less than 20 mm2, more preferably lessthan 5 mm2, and even more preferably less than 3 mm2.The wavelength ^1 of the first laser pump is between 380 nm and 2500 nm,preferably between 700 nm and 2000 nm.The wavelength ^2 of the second laser pump is between 380 nm and 2500 nm,preferably between 700 nm and 2000 nm.The second-order optical nonlinearity of the material used to manufacture thewaveguides is larger than 1 pm / V, preferably larger than 50 pm / V, more preferably larger than 100 pm / V.The optical loss in the waveguides is less than 15 dB / cm, preferably less than 10dB / cm, more preferably less than 5 dB / cm. In a second aspect, the invention relates to a method for frequency conversion of incoming laser pumps using a photonic system according to the first aspect of theinvention. The method comprises the steps:- generating a first laser pump at a first frequency f1,- generating a second laser pump at a second frequency f2,- coupling the first laser pump and the second laser pump into thephotonic integrated circuit, -combining the laser pumps by an optical combiner,- directing the combined laser pumps into a first waveguide, which isnonlinear comprising a second-order nonlinear optical susceptibility material for frequency conversion, -the first waveguide, frequency converting the first laser pump andthe second laser pump, generating a frequency converted signal of athird frequency f3, -generating one or more phase-shifted signal(s) by:^ phase shifting the first laser pump and / or the second laserpump before the first laser pump and / or the second laserpump enters the optical combiner, and / or 83690PC01 15 ^phase shifting first laser pump after entering the firstwaveguide, the second laser pump after entering the firstwaveguide and / or the frequency converted signal, -generating an output signal from the first waveguide, wherein theoutput signal is a modulated frequency converted signal by:^ the first waveguide forming the modulated frequencyconverted signal by optical interaction between the phase-shifted signal(s) and one, or more, of the first laser pump, the second laser pump and / or the frequency converted signal.In the case of SPDC two frequency converted signals with frequency f3 and f4 may be generated when the first waveguide is frequency converting the first laser pump and the second laser pump.In a third aspect, the invention relates to a computer implemented software whichcontrols the photonic system according to the first aspect of the invention. The computer implemented software may be implemented in programmable electronics.The first, second and third aspects of the present invention may each becombined with any of the other aspects. These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter. BRIEF DESCRIPTION OF THE FIGURESThe photonic system according to the invention will now be described in moredetail with regard to the accompanying figures. The figures show one way of implementing the present invention and is not to be construed as being limiting to other possible embodiments falling within the scope of the attached claim set. Fig. 1a and 1b illustrate an overview of the dynamics in an embodiment of the photonic system. 83690PC01 16Fig. 2 illustrates an embodiment of photonic system with an optical phasemodulator modulating the first laser pump.Fig. 3 illustrates an embodiment of the photonic system with an optical phasemodulator modulating the second laser pump.Fig. 4 illustrates an embodiment of the photonic system with an optical phasemodulator modulating the first laser pump according to a feedback signal.Figs. 5a and 5b illustrate in a simplified overview the dynamics of an advancedembodiment of the photonic system of the embodiment with a second waveguideFig. 6 illustrates an embodiment of the photonic system with an optical phasemodulator at the second waveguide modulating the frequency converted signal inthe second waveguide.Fig. 7 illustrates an embodiment of the photonic system with an optical phasemodulator at the second waveguide modulating the first laser pump in the secondwaveguide.Fig. 8 illustrates an embodiment of the photonic system with an optical phasemodulator at the second waveguide modulating the second laser pump in thesecond waveguide.Fig. 9 illustrates an embodiment of the photonic system with an optical phasemodulator at the second waveguide modulating either of the pumps or signal inthe second waveguide according to a feedback signal. Fig. 10 shows a diagram illustrating a simulation of the power of the first laserpump, the second laser pump and the output signal at different phase shifts of thefirst laser pump.Fig. 11 is a flow-chart of a method according to the invention.DETAILED DESCRIPTION OF AN EMBODIMENTFigs. 1a and 1b illustrate an overview of the dynamics in an embodiment of thephotonic system of the invention. Fig. 1a shows a compact platform 1, whichpreferably is a photonic chip with embedded integrated circuit(s) (PIC(s)), the firstlaser source 2 is generating a first laser pump 6, the second laser source 3 isgenerating a second laser pump 7. The first laser pump 6 enters an optical phasemodulator 12’ on the photonic integrated circuit 1, the first laser pump 6 is phaseshifted in the optical phase modulator 12’, and the phase shifted signal 22 and the 83690PC01 17second laser pump 7 enters the first waveguide 9. In the first waveguidethe phase shifted signal 22 and the second laser pump 7 are frequency convertedgenerating a modulated frequency converted signal 19, which is the output signal33. A phase shift controller 26 is arranged to control the optical phase modulator12’ to regulate the phase shift that is applied to the optical beam by the opticalphase modulator 12’. An electric signal 32 is sent from the phase shift controllerto the optical phase modulator 12’. The characteristic of the electrical signaldetermines the magnitude of the phase shift applied the optical beam. The phaseshift controller 26 comprises an electrical contact pad 14 with an input port 15(See Fig. 2).Fig. 1b is illustrating the same photonic system of Fig. 1a with an additionalfeedback mechanism, where the output signal 33 is transmitted as a feedbacksignal 31 to the phase shift controller 26. The phase shift controller 26 then mayadjust the phase shift taking place in the phase shift controller by changing the electric signal 32.Figs. 2-4 illustrate the embodiment of Fig. 1a and 1b in more detail.Fig 2 shows a compact platform 1 which is a photonic chip with a photonicintegrated circuit 1, the first laser source 2 generating a first laser pump 6 withfrequency f1, the second laser source 3 generating a second laser pump 7 withfrequency f2. Input couplers 4, 5 are coupling the first laser pump 6 and thesecond laser pump 7 into the PIC 1. The first laser pump 6 is phase shifted by theoptical phase modulator 12’ obtaining a phase-shifted signal 22 which enters theoptical combiner 8, together with the second laser pump 7. The optical combiner 8may be a multiplexer.The phase shift controller 26 controls the phase shift. The phase shift controller 26comprises an electrical contact pad 14 with an input port 15 for an electricalsignal. An electrical wire 13 connects the contact pad 14 to the optical phasemodulator 12’ for transmitting the electrical signal 32 controlling the phase shiftby either changing the refractive index by an electrical-optical effect or a thermaloptical effect, or by changing the optical path length by inducing a stress-straineffect in the waveguide located internally in the optical phase modulator. 83690PC01 18 From the optical combiner 8 the phase-shifted signal 22 and the second laserpump 7 enters the first waveguide 9, which is a second-order nonlinearwaveguide, in the first waveguide 9 a part of the phase-shifted signal 22 and thesecond laser pump 7 are frequency converted generating the frequency convertedsignal 10 with frequency f3. The special case of spontaneous parametric downconversion (SPDC) in which two signals with frequencies with f3 and f4 is notincluded in this drawing. The frequency converted signal may further opticallyinteract with the laser pumps by optical parametrical amplification to generate themodulated frequency converted signal 19, which is the output signal 33 and isoutputted through an output port 18.Fig. 2 shows the situation where the first laser pump 6 with the frequency f1 isphase shifted by the first modulator 12’.The optical phase modulator 12’ is placed between the input coupler 4 and theoptical combiner 8, so the phase shift of the first pump 6 takes place between theinput coupler 4 and the optical combiner 8.Fig. 3 is identically with Fig. 2 except that the first modulator 12’ is positioned tophase shift the second laser pump 7. But otherwise, the embodiment shown inFig. 3 works the same way as the embodiment shown in Fig. 2 and is thereforenot further described here.The working method for the embodiment illustrated in Figs. 2 and 3 is describedin the following. The letters A-F illustrates where in the photonic integrated circuit1 the different processes take place.A. The laser pumps 6, 7 from the two laser sources 2, 3 are coupled into thephotonic integrated circuit 1.B. Electrically controlled by the optical phase modulator 12’ the phase of one ofthe pumps is modulated.- In Fig. 2 it is the first laser pump 6 with frequency f1 that is phase modulated. 83690PC01 19- In Fig. 3 it is the second laser 7 with frequency f2 that is phasemodulated.C. The pumps are combined into the first waveguide 9 by the optical combiner 8.D. By difference frequency generation (DFG), or sum of frequency generation(SFG), or second harmonic generation (SHG) a frequency converted signal 10 withfrequency f3 is generated from optical interaction of the phase-shifted signal 22with either the first laser pump 6 (in Fig. 3) or the second laser pump 7 (in Fig. 2)in the first waveguide 9. In the case of using spontaneous parametric down-conversion two frequency converted signals and with frequency f3 and f4 aregenerated from optical interaction of the phase-shifted signal 22 with either thefirst laser pump 6 (in Fig. 3) or the second laser pump 7 (in Fig. 2) in the firstwaveguide 9.E. The signal now further enhances or diminish the generation of the modulatedsignal 19 by optical parametric amplification depending on the phase of thephase-shifted signal 22 and the non-phase shifted pump: -In Fig. 2 it is ref. 7 that is the non-phase shifted pump.- In Fig. 3 it is ref. 6 that is the non-phase shifted pump.F. the generated modulated frequency converted signal 19 is outputted throughthe output port 18. Fig. 4 is similar to Fig. 2 and is illustrating the situation where a feedback signal 31 is transmitted from the output port 18 via a beamsplitter 35 to the input port15 where the feedback signal is used to adjust the electrical signal 32 (see Fig. 1)controlling the phase shift.The phase shift controller 26 may use the feedback signal 31 to increase orreduce the phase shift to either enhance or diminish the modulated signal 19 atthe output. This functionality may be implemented in programmable electronics.Figs. 5a and 5b illustrate in a simplified overview the dynamics of an advancedembodiment of the photonic system of the embodiment with a second waveguide. 83690PC01 20Fig. 5a and 5b illustrate an of the photonic system of the invention,wherein phase shift of one or more of the first laser pump, second laser pumpand / or the frequency converted signal is taking place in the second waveguide.Fig. 5a shows a compact platform 1 which preferably is a photonic chip with anembedded integrated circuit (PIC). The first laser source 2 is generating a firstlaser pump 6, the second laser source 3 is generating a second laser pump 7. Thefirst laser pump 6 and second laser pump 7 enters the nonlinear first waveguide9. In the first waveguide the first laser pump 6 and the second laser pump 7 arefrequency converted generating a modulated frequency converted signal 19. Oneor more of the first laser pump 6, the second laser pump 7 and / or frequencyconverted signal 10 (see Fig. 6) enters the second waveguide 11 as the incomingbeam(s) 21, the second waveguide works together with an optical phasemodulator 12’’ and a reflector 16 to generate a phase shifted signal 22, which isreturned to the first waveguide 9. In the first waveguide the phase shifted signalis optical interacting with the first laser pump 6, the second laser pump 7 and / orthe frequency converted signal 10 to generate a modulated frequency convertedsignal 19 which is the output signal 33. A phase shift controller 26 is arranged tocontrol the optical phase modulator 12’’ to regulate the phase shift taking place inthe optical phase modulator 12’’ by sending an electric signal 32 to the opticalphase modulator 12’’, which either changes the refractive index by an electrical-optical effect or a thermal-optical effect, or by changing the optical path length by inducing a stress-strain effect in the waveguide located internally in optical phase modulator, and hereby causing the phase shift.Fig. 5b is illustrating the dynamics in the same photonic system of fig 5a with afeedback mechanism added, where the output signal 33 is transmitted as afeedback signal 31 to the phase shift controller 26. The phase shift controller 26 then may adjust the phase shift taking place in the optical phase modulator 12’’by changing the electric signal 32. Figs. 6-9 illustrate the embodiment of Figs. 5a and 5b in more detail.Fig 6 shows the compact platform 1, which may be a photonic chip, the first lasersource 2 generating a first laser pump 6 with frequency f1, the second lasersource 3 generating a second laser pump 7 with frequency f2. The input couplers 83690PC01 214, 5 are coupling the first laser 6 and the second laser pump 7 into theoptical combiner 8, which may be a multiplexer. The first waveguide 9, which is asecond-order nonlinear waveguide, frequency convert the first laser pump 6 andsecond laser pump 7 to generate the frequency converted signal 10 withfrequency f3. An evanescent coupler 20 is arranged to couple one, or more, of the pumps or signal from the first waveguide into the second waveguide as incoming beam(s)21. The incoming beam(s) 21 from the first waveguide is / are the first laser pump,the second laser pump, and / or the frequency converted signal. In Fig. 6 theincoming beam 21 is the first laser pump 6 which is phase shifted in the secondwaveguide 11.In the second waveguide 11 an optical phase modulator 12’’ may phase shift theincoming beam or signal 21 generating a phase shifted signal 22, which is returned to the first waveguide. A phase shift controller 26 is arranged to control the optical phase modulator 12’’to regulate the phase shift taking place in the second waveguide 11 by sending anelectric signal 32 (see Fig. 5a) to the optical phase modulator 12’’, which eitherchanges the refractive index by an electrical-optical effect or a thermal-optical effect, or by changing the optical path length by inducing a stress-strain effect inthe second waveguide 11 located internally in the optical phase modulator 12’’.The phase shift controller 26 comprises an electrical contact pad 14 with an inputport 15.The optical phase modulator 12’’ is controlled by the electrical signal 32, which istransmitted by an electrical wire 13, from the phase shift controller 26. The phaseshift controller comprises an electrical contact pad 14 and an input port forelectrical signal 15. A second reflector 16 is mounted at the remote end 38 of thesecond waveguide. When the incoming beam enters the second waveguide, it maytravel from the input end 37 towards the remote end 38. At the remote end thereflector is positioned to reflect the incoming beam and / or the phase shifted signalback through the second waveguide, so the beam or signal is travelling back in 83690PC01 22the second waveguide and the signal 22 is returned to the firstwaveguide.When the phase shifted signal 22 enters the first waveguide 9 from the secondwaveguide 11 the phase shifted signal may be moving the opposite direction thanthe laser pumps 6, 7, moving towards the input end 37, therefore, a first reflector17 may be positioned at the input end 37 to reflect the phase shifted signal, so itmoves in the same direction as the laser pumps.Fig. 7 is identically with Fig. 6 except that Fig. 7 shows the situation where thesecond laser pump 7 with the frequency f2 is the incoming beam 21 and is phaseshifted in the second waveguide 11.Fig. 8 is identically with Figs. 6 and 7 except that Fig. 8 shows the situation wherethe frequency converted signal 10 is the incoming beam 21 and is phase shifted inthe second waveguide. The working method for the embodiment illustrated in Figs. 6-8 is described in thefollowing. The letters G-O illustrates where in the photonic integrated circuit 1 thedifferent processes take place.G. The laser pumps 6, 7 from the two laser sources 2, 3 are coupled into thephotonic integrated circuit 1 and subsequently combined by the optical combiner8, after which the pumps are launched into the first waveguide 9.H. By difference frequency generation (DFG), sum of frequency generation (SFG)or second harmonic generation (SHG) a frequency converted signal 10 withfrequency f3 is generated from frequency conversion of the first laser pump 6 andthe second laser pump 7 in the first wave guide 9. In the case of usingspontaneous parametric down-conversion two frequency converted signals andwith frequency f3 and f4 are generated from the frequency conversion of the firstlaser pump 6 and / or the second laser pump 7 in the first wave guide 9.I. Part of the beams or signals in the first waveguide is coupled into the secondwaveguide by directional coupling. 83690PC01 23- In Fig. 6 it is the first laser pump frequency f1 that is primarily coupledfrom the first waveguide 9 to the second waveguide 11.- In Fig. 7 it is the second laser pump 7 with frequency f2 that is primarily coupledfrom the first waveguide 9 to the second waveguide 11.- In Fig. 8 it is the frequency converted signal 10 with frequency f3 that isprimarily coupled from the first waveguide 9 to the second waveguide 11.J. Electrically controlled by the optical phase modulator 12’’ the phase of thebeams are modulated forming the phase shifted signal.K. The phase shifted signal is reflected.L. The phase shifted signal from the second waveguide is coupled back into thenonlinear waveguide.M. The phase shifted signal is reflected.N. The phase shifted signal now has the phase that further enhance or diminishthe generation of the modulated frequency converted signal 19 by opticalparametric amplification.O. the modulated frequency converted signal is outputted through the output port18 as the output signal 33.Fig. 9 is similar to Fig. 6 and is illustrating the situation where a feedback signal 31 is transmitted from the output port 18 via a beamsplitter 35 to the input port15, where the feedback signal is used to adjust the electrical signal 32 controllingthe phase shift.The phase shift controller may use the feedback signal 26 to increase or reducethe phase shift for instance to seek to enhance the feedback signal. This functionality may be implemented in programmable electronics.Fig. 10 shows a diagram illustrating a simulation of the power of the first laserpump, the second laser pump and the output signal at different phase shifts of the 83690PC01 24first laser pump. In the simulation input 41 of the first waveguide 9, z=0,where z describes the propagation length of the light beams, the frequencyconversion is initiated. The power of the first laser pump 6 at this point is Pp1=5.0mW, the power of the second laser pump 7 at this point is Pp2=4.0 mW and thepower of the frequency converted signal at this point is Ps=1.0 mW. The diagramshows the output power 42 of the first laser pump, the output power 43 of thesecond laser pump, and the output power 44 of the output signal at z = 3 mm.The sum 45 of the output powers of the beams and signals are 10 mW. Theoutput power is the power of the beams and signals at the output port 18 whenthey leave the first waveguide.The phase shift diagram 40 shows the output power at different phase shifts ofthe first laser pump. The phase shift of the first laser pump is shown on the x-axis. When the first laser pump is phase shifted with about 90 degrees, illustratedby the OFF marking in the diagram, then the power at the output port 18 of themodulated phase shifted signal, which is the output signal 19 is close to zero.However, when the first laser pump is phase shifted with about 270 degrees,illustrated by the ON marking in the diagram, the power at the output port 18 ofthe modulated phase shifted signal, which is the output signal 19, is close to 3mW. Here the power of the first laser pump is low, so power has by opticalinteraction in the first waveguide been transferred from the first pump, and thesecond pump to the modulated frequency converted signal, which is the outputsignal 19. Therefore, the phase shift diagram 40 shows the magnitude of theoutput signal 19 at different phase shifts of the first laser pump 6. And theoptimal output signal is achieved when the phase shift is about 270 degrees.This shows that by phase shifting one of the pumps or signals the magnitude of the output signal can be adjusted and by optimal set up of the phase shift theoutput signal may be enhanced significantly.Fig. 11 illustrates the method of the invention. The method comprises generating(S1) a first laser pump, generating (S2) a second laser pump, coupling (S3) thefirst laser pump and the second laser pump into an optical combiner, the opticalcombiner is combining (S4) the laser pumps, and is directing (S5) the combined pumps into the first waveguide. The first waveguide is frequency converting (S6) 83690PC01 25the first laser pump and the second pump generating a frequency convertedsignal. Then the method further comprises generating (S7) one of more phase-shiftedsignals by phase shifting the first laser pump and / or the second laser pump beforethe first laser pump and / or the second laser pump enters the optical combiner,and / or by phase shifting the first laser pump after entering the first waveguide,the second laser pump after entering the first waveguide and / or the frequencyconverted signal. Then finally the method is generating (S8) an output signal from the firstwaveguide. The output signal is a modulated frequency converted signal formedby the first waveguide by optical interaction between the phase-shifted signalpump(s) and one, or more, of the first laser pump(s), the second laser pump and / or the frequency converted signal. DISCLAIMER: The following section contains novel theory within the field of integrated optics which underpins the invention. To fully comprehend the content of this section it requires an insight in the theory of field of optics or theory of similar fields. The complex wavenumber for a given mode ν is expressed as: kν^= βν^+ iαν / 2 = nνων / c^, (1)where βν^is the wavenumber, αν^the attenuation coefficient, nν^the effective refractiveindex,ων^the angular frequency, and c the speed of light in vacuum. The complexelectric field ℇ^^^^^⃗ and magnetic field ^ ℋ^^^^^⃗ are expressed in the coordinates ^, ^, ^̂ andtime t: ℇ^^^^^⃗ = ^ ^^^^^⃗ (^, ^)^^^^⃗ (^, ^)^^^^ , (2) , (3) 83690PC01 26which propagates in the ^̂ direction the propagator φν = kνz – ωt. Theamplitude of the field is decomposed in the mode profiles ^^^^⃗ (^, ^) and ^^^^^^⃗ (^, ^), anda complex unitless function ^^^^^^⃗ (^, ^) = ^ ^^^^^⃗ (^, ^)^^^^that accounts for mode coupling,where ^ ^^^^^⃗ = ^^^^^^^⃗ ^ and ϕν is the (real) phase of the mode. The fields are normalized^ =^ ^∬ℝ^^^^⃗ × ^^^∗ ^^ ^^^⃗ ^ ∙ ^̂ ^^ ^^ = 1^. (4)Using the above derivethe chief equation: ^^^^^^ = ^^^^^ + ^^^^, (5)where: ^^^ = ^^ ∬^^(^)^^^(^) ^^^^^ ^ ⋅ ^∗ ^^ ^^ (6) and ^^^ =^^^^^^^^^ ∬^^ ^^ ^^ ⋅ ^∗ ^^ ^^ (7) Here, γ(Ω) = Ωnmat / c, Ω is fourier frequency, ω is the laser frequency, and ^^^^is the nonlinear terms of the polarization field. The tilde accents on the variables^^ ^^, ^^, ^^^ , and ^^^ denote that these variables are the Fourier transform ofrespectively ^^^, ^, ^^, and ^^ in the time domain. Equation (5) holds for pulsedlight, but we will now consider it to be monochromatic such that ^^^ = 0, for sake ofsimplicity. Considering two pump laser sources with frequencies ωp1 and ωp2. If light from the pump sources interact with a second-order nonlinear medium (e.g. GaAs or Lithium niobate), second-order frequency conversion processes can occur, where a signal with frequency ωs is generated. For instance, considering difference frequency conversion (DFG), energy conservation yields: ^^^ = ^^^ + ^^ ⇒ λ^ =^ ^ / λ^^ – ^ / λ^^(8) Considering perfect Δβ = β^^ − β^^ − β^ = 0, (9) 83690PC01 27 equation (5) simplifies and can derive the following six coupled amplitude equations: ∂^^s = ^Γp1 − Γp2^^^^p2^^^^^^ / ^ sin(Δϕ) ^p2^p1, (10.1) =− cos^p2^^^p2 = Γp2^^^s^^^^^^ / ^ cos(Δ^) ^s^p1, (10.5) =coswhere ∆ϕ = ϕs + ϕp2 – ϕp1 is the phase-mismatch of the real phase (not to bemistaken for the phase matching condition in equation (9) that is thewavenumber-mismatch ∆β). The above is to the best of our knowledge the first introduction of the coupled-amplitude equations, including the initial source- phase, for integrated photonic circuits (PICs) using different materials. The factor: Γ^ ≡ ^^^^ / ^ ^ ∈ p1,p2,s, (12)has been introduced with κ being the coupling coefficient that describes the strength of the nonlinear interaction: ^^ κ^^≡ ^^∬^^ (^^^^^⃗ ) ⋅ ^ ^^^∗ν⃗ ^^ ^^, ν ∈ p1,p2,s. (11) In eq.(11) D is material dependent the susceptibility tensor: ^^^^^^^^^^^^^^^^^^^ = ^^^^^^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^^^^and ^⃗ is a corresponding vector of the field profiles. For the special case of DFG: 83690PC01 28 ö ÷ ÷ . ø power for the pumps and the signal by the expression: ^^(^) = ^^^^^^|^^(^)^|, ν ∈ ^1, ^2, ^.Development of the theory contributed to the insight that it was possible to eitherenhance or diminish the output signal by phase shifting one of the pumps or thefrequency converted signal allowing for modulation of the signal.In exemplary embodiments E1-E15, the invention may relate to: E1. A photonic system for frequency conversion of incoming laser pump(s), the photonic system (100) is comprising: -a first laser source (2), which is arranged to generate a first laserpump (6) at a first frequency f1, -a second laser source (3), which is arranged to generate a secondlaser pump (7) at a second frequency f2, -a first waveguide (9), which is nonlinear comprising a second-ordernonlinear optical susceptibility material for frequency conversion, -an optical combiner (8), which is arranged to combine the laserpumps (6, 7) from the first laser source and the second laser source, and direct the combined pumps into the first waveguide (9), and -an input coupler (4, 5) to couple the first laser pump and the secondlaser pump, wherein -the first waveguide (9) and the optical combiner (8) are integratedinto a compact platform (1), -the first waveguide (9) is arranged to frequency convert the firstlaser pump (6) and the second laser pump (7) to generate a frequency converted signal (10) of a third frequency f3, 83690PC01 29 -phase shifting means 12’, 12’’) are arranged to generate one ormore phase-shifted signals(s) (22) by: ^phase shift the first laser pump (6) and / or the second laserpump (7) before the first laser pump and / or the second laser pump enters the optical combiner (8), and / or ^phase shift the first laser pump (6) after entering the firstwaveguide (9), the second laser pump (7) after entering the first waveguide (9) and / or the frequency converted signal (10), and -the first waveguide (9) is adapted to generate an output signal (33),the output signal is a modulated frequency converted signal (19), ^where the modulated frequency converted signal (19) isformed within the first waveguide (9) by optical interaction between the phase-shifted signal(s) (22) and one, or more, of the first laser pump (6), the second laser pump (7) and / or the frequency converted signal (19). E2. The photonic system according to embodiment E1, wherein the phase shifting means (11, 12) are a first optical phase modulator (12’), a second optical phase modulator (12’’) and / or a second waveguide (11).E3. The photonic system according to embodiment E2, wherein phase shiftingmeans (11, 12) are arranged to phase shift the first laser pump (6), the second laser pump (7) and / or the frequency converted signal (10) within the second waveguide (11) to generate phase-shifted signal(s) (22).E4. The photonic system according to embodiment E3, wherein- an evanescent coupler (20) is arranged to couple one, or more, ofthe beams from the first waveguide (9) into the second waveguide (11) as incoming beam(s), where the incoming beam(s) from the first waveguide is / are: a. the first laser pump (6),b. the second laser pump (7), and / or 83690PC01 30 c. a converted signal (10) which is generatedby frequency conversion of the first laser pump and the second laser pump, and -the evanescent coupler (20) is further arranged to couple the phase-shifted signal(s) (22) from the second waveguide into the first waveguide. E5. The photonic system according to any of the embodiments E3-E4, wherein phase shifting means arranged to phase shift the first laser pump (6), the second laser pump (7) and / or the frequency converted signal (10) within the second waveguide (11) comprises a second optical phase modulator (12’’). E6. The photonic system according to any of the embodiments E2-E5, wherein the first optical phase modulator (12’) is arranged to phase shift the first laser pump (6) and / or the second laser pump (7) subsequent to being in-coupled and before entering the optical combiner (8). E7. The photonic system according to any of the embodiments E2-E6, whereineach optical phase modulator (12’, 12’’) comprises a phase shift controller (26)arranged to control the magnitude of the phase shift.E8. The photonic system according to embodiment E7, wherein the phase shiftcontroller(s) (26) is / are adapted to be adjusted based on a feedback signal. E9. The photonic system according to any of the embodiments E2-E8, wherein arranging the second waveguide (11) to phase shift the incoming beam(s) (21) comprises adapting the refractive index of the second waveguide. E10. The photonic system according to any of the preceding embodiments, wherein the compact platform comprises a photonic chip with embedded integrated circuit(s) (PIC(s)). E11. The photonic system according to any of the embodiments E2-E10, wherein the first waveguide (9) comprises an input end, where the laser pumps (6, 7) 83690PC01 31 enter the first waveguide, and a (17) is arranged at the input end of the first waveguide.E12. The photonic system according to embodiment E11, wherein the firstreflector (17) is arranged to reflect the phase-shifted signal(s) received from the second waveguide. E13. The photonic system according to any of the embodiments E2-E12, wherein the second waveguide (11) comprises an remote end oppositely placed from an input end, where the input end is the end where the incoming beam (21) enters the second waveguide, a second reflector (16) is mounted at the remote end of the second waveguide (11), and the second reflector is arranged to reflect beams propagating within the second waveguide back through the second waveguide tobe coupled back into the first waveguide (9).E14. The photonic system according to any of the preceding embodiments, wherein the optical combiner (8) is a multiplexer, being arranged to combine the first laser pump (6) from the first laser source (2) with the second laser pump (7) from the second laser source (3). E15. A method for frequency conversion of incoming laser pumps using a photonic system according to any of the embodiments E1-E14, wherein the method comprises the steps: -generating (S1) a first laser pump (6) at a first frequency f1,- generating (S2) a second laser pump (7) at a second frequency f2,- coupling (S3) the first laser pump and the second laser pump intothe photonic integrated circuit,- combining (S4) the laser pumps (6, 7) by an optical combiner (8),- directing (S5) the combined laser pumps into a first waveguide (9),which is nonlinear comprising a second-order nonlinear optical susceptibility material for frequency conversion, -the first waveguide (9) frequency converting (S6) the first laserpump (6) and the second laser pump (7) generating a frequency converted signal (10) of a third frequency f3, -generating (S7) one or more phase-shifted signal(s) (22) by: 83690PC01 32 ^phase shifting first laser pump (6) and / or the second laserpump (7) before the first laser pump and / or the second laser pump enters the optical combiner (8), and / or ^phase shifting the first laser pump (6) after entering the firstwaveguide (9), the second laser pump (7) after entering the first waveguide (9) and / or the frequency converted signal (10), -generating (S8) an output signal (33) from the first waveguide (9),wherein the output signal is a modulated frequency converted signal (19) by: ^the first waveguide forming the modulated frequencyconverted signal (19) by optical interaction between thephase-shifted signal(s) (22) and one, or more, of the first laser pump (6), the second laser pump (7) and / or the frequency converted signal (19). Although the present invention has been described in connection with the specified embodiments, it should not be construed as being in any way limited to the presented examples. The scope of the present invention is set out by the accompanying claim set. In the context of the claims, the terms “comprising” or “comprises” do not exclude other possible elements or steps. Also, the mentioning of references such as “a” or “an” etc. should not be construed as excluding a plurality. The use of reference signs in the claims with respect to elements indicated in the figures shall also not be construed as limiting the scope of the invention. Furthermore, individual features mentioned in different claims, may possibly be advantageously combined, and the mentioning of these features in different claims does not exclude that a combination of features is not possible and advantageous.

Claims

1. 83690PC01 33 CLAIMS 1. A photonic system for frequency conversion of incoming laser pump(s), the photonic system (100) is comprising: -a first laser source (2), which is arranged to generate a first laserpump (6) at a first frequency f1,- a second laser source (3), which is arranged to generate a secondlaser pump (7) at a second frequency f2,- a first waveguide (9), which is nonlinear comprising a second-ordernonlinear optical susceptibility material for frequency conversion, -an optical combiner (8), which is arranged to combine the laserpumps (6, 7) from the first laser source and the second laser source,and direct the combined pumps into the first waveguide (9), and -an input coupler (4, 5) to couple the first laser pump and the secondlaser pump, wherein -the first waveguide (9) and the optical combiner (8) are integratedinto a compact platform (1), wherein the compact platform is aphotonic chip with embedded integrated circuit(s) (PIC(s)), -the first waveguide (9) is arranged to frequency convert the firstlaser pump (6) and the second laser pump (7) to generate afrequency converted signal (10) of a third frequency f3,- phase shifting means (11, 12’, 12’’) are arranged to generate one ormore phase-shifted signals(s) (22) by: ^phase shift the first laser pump (6) and / or the second laserpump (7) before the first laser pump and / or the second laserpump enters the optical combiner (8), wherein the phaseshifting means (11, 12) are a first optical phase modulator (12’) and / or^ phase shift the first laser pump (6) after entering the firstwaveguide (9), the second laser pump (7) after entering thefirst waveguide (9) and / or the frequency converted signal (10), wherein ^the phase shifting means is a second optical phasemodulator (12’’) or a second waveguide (11),83690PC01 34 ^the means (11, 12’’) are arranged tophase shift the first laser pump (6), the second laser pump (7) and / or the frequency converted signal (10) within the second waveguide to generate phase-shifted signal(s) (22), and ^an evanescent coupler (20) is arranged to couple one,or more, of the first laser pump (6), the second laser pump (7), and / or a frequency converted signal (10) which is generated by frequency conversion of the first laser pump and the second laser pump, from the first waveguide (9) into the second waveguide (11) as incoming beam(s), and the evanescent coupler (20) isfurther arranged to couple the phase-shifted signal(s) (22) from the second waveguide into the first waveguide, and -the first waveguide (9) is adapted to generate an output signal (33),the output signal is a modulated frequency converted signal (19),^ where the modulated frequency converted signal (19) isformed within the first waveguide (9) by optical interaction between the phase-shifted signal(s) (22) and one, or more, of the first laser pump (6), the second laser pump (7) and / orthe frequency converted signal (10).

2. The photonic system according to claim 1, wherein phase shifting meansarranged to phase shift the first laser pump (6), the second laser pump (7) and / or the frequency converted signal (10) within the second waveguide (11) comprises a second optical phase modulator (12’’).

3. The photonic system according to any of the claims 1-2, wherein the firstoptical phase modulator (12’) is arranged to phase shift the first laser pump (6)and / or the second laser pump (7) subsequent to being in-coupled and beforeentering the optical combiner (8).83690PC01 35 4. The photonic system according of the claims 1-3, wherein each opticalphase modulator (12’, 12’’) comprises a phase shift controller (26) arranged tocontrol the magnitude of the phase shift.

5. The photonic system according to claim 4, wherein the phase shift controller(s) (26) is / are adapted to be adjusted based on a feedback signal.

6. The photonic system according to any of the claims 1-5, wherein arranging the second waveguide (11) to phase shift the incoming beam(s) (21) comprisesadapting the refractive index of the second waveguide, by the electrical-optical-effect, the thermal-optical effect, adapting the length of the waveguide by a stress-strain effect or by the Kerr effect.

7. The photonic system according to any of the claims 1-6, wherein the firstwaveguide (9) comprises an input end (37), where the laser pumps (6, 7) enterthe first waveguide, and a first reflector (17) is arranged at the input end of the first waveguide.

8. The photonic system according to claim 7, wherein the first reflector (17) is arranged to reflect the phase-shifted signal(s) received from the second waveguide.

9. The photonic system according to any of the claims 1-8, wherein the secondwaveguide (11) comprises an remote end (38) oppositely placed from an inputend (37), where the input end is the end where the incoming beam (21) entersthe second waveguide, a second reflector (16) is mounted at the remote end of the second waveguide (11), and the second reflector is arranged to reflect beamspropagating within the second waveguide back through the second waveguide tobe coupled back into the first waveguide (9).

10. The photonic system according to any of the preceding claims, wherein the optical combiner (8) is a multiplexer, being arranged to combine the first laserpump (6) from the first laser source (2) with the second laser pump (7) from thesecond laser source (3).83690PC01 3611. The photonic system according to any of the preceding claims, wherein theevanescent coupler is a directional coupler.

12. The photonic system, according to any of the preceding claims, wherein thesize of the photonic chip comprising photonic integrated circuits (PICs) preferably is less than 20 mm2, more preferably less than 5 mm2, and even more preferably less than 3 mm2.

13. A method for frequency conversion of incoming laser pumps using a photonic system according to any of the claims 1-12, wherein the method comprises the steps: -generating (S1) a first laser pump (6) at a first frequency f1,- generating (S2) a second laser pump (7) at a second frequency f2,- coupling (S3) the first laser pump and the second laser pump intothe photonic integrated circuit,- combining (S4) the laser pumps (6, 7) by an optical combiner (8),- directing (S5) the combined laser pumps into a first waveguide (9),which is nonlinear comprising a second-order nonlinear optical susceptibility material for frequency conversion, -the first waveguide (9) frequency converting (S6) the first laserpump (6) and the second laser pump (7) generating a frequencyconverted signal (10) of a third frequency f3,- generating (S7) one or more phase-shifted signal(s) (22) by:^ phase shifting the first laser pump (6) and / or the second laserpump (7) before the first laser pump and / or the second laserpump enters the optical combiner (8), wherein the phaseshifting means (11, 12) are a first optical phase modulator (12’) and / or^ phase shifting the first laser pump (6) after entering the firstwaveguide (9), the second laser pump (7) after entering thefirst waveguide (9) and / or the frequency converted signal (10), wherein ^the phase shifting means is a second waveguide (11),83690PC01 37 ^the waveguide (11) is arranged to phase shiftthe first laser pump (6), the second laser pump (7) and / or the frequency converted signal (10) to generate phase-shifted signal(s) (22), and ^an evanescent coupler (20) is arranged to couple one,or more, of the first laser pump (6), the second laser pump (7), and / or a frequency converted signal (10) which is generated by frequency conversion of the first laser pump and the second laser pump, from the first waveguide (9) into the second waveguide (11) as incoming beam(s), and the evanescent coupler (20) isfurther arranged to couple the phase-shifted signal(s) (22) from the second waveguide into the first waveguide, and- generating (S8) an output signal (33) from the first waveguide (9),wherein the output signal is a modulated frequency converted signal (19) by: ^the first waveguide forming the modulated frequencyconverted signal (19) by optical interaction between thephase-shifted signal(s) (22) and one, or more, of the first laser pump (6), the second laser pump (7) and / or thefrequency converted signal (10).

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