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EP-4740065-A1 - A METHOD OF GENERATING SUPERCONTINUUM LIGHT AND A SUPERCONTINUUM LIGHT SOURCE

EP4740065A1EP 4740065 A1EP4740065 A1EP 4740065A1EP-4740065-A1

Abstract

The invention relates to a method of generating supercontinuum light comprising : providing frequency comb pump light and auxiliary pump light, wherein an auxiliary centre frequency is spectrally detuned with respect to a comb centre frequency by an auxiliary pump detuning; pumping a nonlinear medium associated with dispersive wave generation at a dispersive wave frequency shifted by a dispersive wave detuning relative to the comb centre frequency; spectrally translating the frequency comb pump light via a cascaded four-wave mixing process induced by the auxiliary pump light to thereby generate cascaded comb light; generating a dispersive wave at the dispersive wave frequency, wherein the generation of the dispersive wave is induced by the cascaded comb light due to an integer multiple of the auxiliary pump detuning lying within a spectral range of the dispersive wave detuning; and outputting the cascaded comb light and the dispersive wave to thereby provide the supercontinuum light.

Inventors

  • PU, Minhao
  • KIM, CHANJU
  • ZHAO, Yanjing
  • YVIND, KRESTEN

Assignees

  • Danmarks Tekniske Universitet

Dates

Publication Date
20260513
Application Date
20240705

Claims (17)

  1. 1. A method of generating supercontinuum light (13), the method comprising the steps of: providing frequency comb pump light (1) and auxiliary pump light (2), wherein an auxiliary centre frequency (3) of the auxiliary pump light (2) is spectrally detuned with respect to a comb centre frequency (4) of the frequency comb pump light by an auxiliary pump detuning (5), wherein a peak power of the frequency comb pump light is at most 30 Watt; pumping a nonlinear medium (6) with the frequency comb pump light (1) and the auxiliary pump light (2) simultaneously, wherein the frequency comb pump light (1) is associated with a phase matching criterion for dispersive wave generation in the nonlinear medium (6) at a dispersive wave frequency (7) shifted by a dispersive wave detuning (8) relative to the comb centre frequency (4); spectrally translating the frequency comb pump light (1) via a cascaded four- wave mixing process in the nonlinear medium (6) induced by the auxiliary pump light (2) to thereby generate cascaded comb light (10); generating a dispersive wave (11) in the nonlinear medium (6) at the dispersive wave frequency (7), wherein the generation of the dispersive wave (11) is induced by the cascaded comb light (10) due to an integer multiple of the auxiliary pump detuning (5) lying within a spectral range (12) of the dispersive wave detuning (8), wherein the spectral range (12) is centred at the dispersive wave detuning (8) and has a width of at most half of the auxiliary pump detuning (5); and outputting the cascaded comb light (10) and the dispersive wave (11) from the nonlinear medium (6) to thereby provide the supercontinuum light (13).
  2. 2. The method according to claim 1, wherein the peak power of the frequency comb pump light is at most 20 Watt, for example at most 10 Watt, for example at most 5.0 Watt, for example at most 2.0 Watt, such as at most 1.0 Watt.
  3. 3. The method according to any of the preceding claims, wherein the nonlinear medium is a nonlinear waveguide comprising silicon nitride, lithium niobate, aluminium nitride, silica, aluminium gallium arsenide, silicon carbide, tantalum pentoxide, amorphous silicon, silicon, or gallium phosphide, preferably aluminium gallium arsenide.
  4. 4. The method according to any of the preceding claims, wherein the dispersive wave has a relative spectral peak amplitude which is at least 5 dB greater than a local spectral minimum between the dispersive wave frequency and the comb centre frequency, for example at least 10 dB greater, such as at least 15 dB greater.
  5. 5. The method according to any of the preceding claims, wherein the method comprises a step of establishing a parametric gain spectrum in the nonlinear medium, wherein the parametric gain spectrum is established by the frequency comb pump light via the step of pumping the nonlinear medium, wherein the auxiliary centre frequency is spectrally located in the parametric gain spectrum such that a parametric gain is applied to the auxiliary pump light.
  6. 6. The method according to claim 5, wherein the auxiliary centre frequency is spectrally located within a 15-dB bandwidth of a side lobe of the parametric gain spectrum, for example within a 10-dB bandwidth, such as within a 5-dB bandwidth.
  7. 7. The method according to any of the preceding claims, wherein the integer multiple of the auxiliary pump detuning corresponding to the dispersive wave detuning is from 2 to 15.
  8. 8. The method according to any of the preceding claims, wherein a relative peak amplitude of the dispersive wave is reduced by at least 20 dB when the nonlinear medium is not pumped by the auxiliary pump light.
  9. 9. The method according to any of the preceding claims, wherein a 40-dB bandwidth of the supercontinuum light is at least 80 THz, for example at least 100 THz, such as at least 120 THz.
  10. 10. The method according to claim 9, wherein the 40-dB bandwidth is reduced by at least 50 % when the nonlinear medium is not pumped by the auxiliary pump light, for example at least 65 %, such as at least 80 %.
  11. 11. The method according to any of the preceding claims, wherein the dispersive wave frequency is a first dispersive wave frequency, the dispersive wave detuning is a first dispersive wave detuning, the dispersive wave is a first dispersive wave, the integer multiple of the auxiliary pump detuning is a first integer multiple, the spectral range is a first spectral range, wherein the frequency comb pump light is associated with the phase matching criterion for dispersive wave generation at the first dispersive wave frequency and a second dispersive wave frequency, wherein the first dispersive wave frequency is shifted by the first dispersive wave detuning relative to the comb centre frequency, wherein the second dispersive wave frequency is shifted by a second dispersive wave detuning relative to the comb centre frequency, wherein the method further comprises a step of generating a second dispersive wave in the nonlinear medium at the second dispersive wave frequency, wherein the generation of the second dispersive wave is induced by the cascaded comb light due to a second integer multiple of the auxiliary pump detuning lying within a second spectral range of the second dispersive wave detuning, wherein the second spectral range is centred at the second dispersive wave detuning and has a width equal to the width of the first spectral range, wherein the step of outputting the cascaded comb light and the first dispersive wave is a step of outputting the cascaded comb light, the first dispersive wave, and the second dispersive wave from the nonlinear medium to thereby provide the supercontinuum light.
  12. 12. A supercontinuum light source (14) comprising : a frequency comb light source (15) configured to provide frequency comb pump light (1) having a comb centre frequency and a peak power of at most 30 Watt; an auxiliary light source (16) configured to provide auxiliary pump light (2) having an auxiliary centre frequency which is spectrally detuned with respect to the comb centre frequency by an auxiliary pump detuning; a nonlinear medium (6), wherein the frequency comb light source and the auxiliary light source are optically coupled to the nonlinear medium, wherein the frequency comb pump light is associated with a phase matching criterion for dispersive wave generation in the nonlinear medium at a dispersive wave frequency shifted by a dispersive wave detuning relative to the comb centre frequency, wherein the nonlinear medium is configured to spectrally translate the frequency comb pump light via a cascaded four-wave mixing process induced by the auxiliary pump light to thereby generate cascaded comb light, wherein the cascaded comb light is configured to induce generation of a dispersive wave in the nonlinear medium at the dispersive wave frequency due to an integer multiple of the auxiliary pump detuning lying within a spectral range of the dispersive wave detuning, wherein the spectral range is centred at the dispersive wave detuning and has a width of at most half of the auxiliary pump detuning, wherein the nonlinear medium is configured to output the cascaded comb light and the dispersive wave to provide supercontinuum light (13).
  13. 13. The supercontinuum light source according to claim 12, wherein the frequency comb light source comprises a primary continuous wave light source and a nonlinear resonator medium, such as a nonlinear micro-ring resonator or a Fabry-Perot resonator, which is pumped by the primary continuous wave light source to establish the frequency comb pump light.
  14. 14. The supercontinuum light source according to any of claims 12-13, wherein the frequency comb light source is integrated on a chip.
  15. 15. The supercontinuum light source according to any of claims 12-14, wherein an electrical power consumption of the frequency comb light source is at most 8.0 W, for example at most 5.0 W, such as at most 3.0 W.
  16. 16. The supercontinuum light source according to any of claims 12-15, wherein the frequency comb light source and the auxiliary light source are serially coupled to the nonlinear medium such that the frequency comb pump light passes through the auxiliary light source prior to entering the nonlinear medium.
  17. 17. The supercontinuum light source according to claim 16, wherein the auxiliary light source comprises two mirrors which are arranged to define a laser cavity of the auxiliary light source, wherein a respective transmission coefficient for each of said two mirrors is greater for light at the comb centre frequency than for light at the auxiliary centre frequency.

Description

A METHOD OF GENERATING SUPERCONTINUUM LIGHT AND A SUPERCONTINUUM LIGHT SOURCE FIELD OF THE INVENTION The present invention relates to a method of generating supercontinuum light. The invention further relates to a supercontinuum light source. BACKGROUND OF THE INVENTION Nonlinear optical processes can be utilized to generate new frequencies of light. In a simple picture, pump light can be used to pump a nonlinear medium, and a nonlinear interaction between the pump light and the nonlinear medium can, e.g ., generate frequencies of light not present in the pump light. Accordingly, nonlinear optical processes offer a host of possibilities to provide new types of light and light sources. One type of light which may be established via nonlinear processes is supercontinuum light, which can be formed by nonlinear processes acting on pump light to cause spectral broadening. Conventionally, supercontinuum light can be provided with various spectral widths, but generally, it is desirable to have a very broad supercontinuum. A broad supercontinuum can be used to study a broader range of phenomena and may permit optical stabilization of the light through f-2f interferometry. Due to the nonlinearity of nonlinear optical processes, a fundamental constraint is that high- intensity pumping light is most often required . For example, broad supercontinuum light is typically generated by pumping a nonlinear medium with a femtosecond laser having a peak power of several kilowatts. The constraint that high-intensity light is typically required to generate broad spectrum light significantly restraints utilization of supercontinuum light in practical applications. Most often, a bulky table-top or fibre-based system is required to provide adequate pump power. Accordingly, there is a need for new approaches which permit generation of broad supercontinuum light using limited input power or alternative pump light sources. SUMMARY On the above background, it is an object of preferred embodiments of the invention to provide an approach for generating broad supercontinuum light using reduced optical power in comparison with conventional solutions. It is further an object of some embodiments of the invention to provide broadband supercontinuum light based on alternative pump light sources. An additional object of some embodiments is to provide miniaturized systems capable of generating supercontinuum light, which in turn may be enabled by reduced power and/or alternative pump light sources. A first aspect of the present disclosure relates to a method of generating supercontinuum light, the method comprising the steps of: providing frequency comb pump light and auxiliary pump light, wherein an auxiliary centre frequency of the auxiliary pump light is spectrally detuned with respect to a comb centre frequency of the frequency comb pump light by an auxiliary pump detuning, wherein a peak power of the frequency comb pump light is at most 30 Watt; pumping a nonlinear medium with the frequency comb pump light and the auxiliary pump light simultaneously, wherein the frequency comb pump light is associated with a phase matching criterion for dispersive wave generation in the nonlinear medium at a dispersive wave frequency shifted by a dispersive wave detuning relative to the comb centre frequency; spectrally translating the frequency comb pump light via a cascaded four-wave mixing process in the nonlinear medium induced by the auxiliary pump light to thereby generate cascaded comb light; generating a dispersive wave in the nonlinear medium at the dispersive wave frequency, wherein the generation of the dispersive wave is induced by the cascaded comb light due to an integer multiple of the auxiliary pump detuning lying within a spectral range of the dispersive wave detuning, wherein the spectral range is centred at the dispersive wave detuning and has a width of at most half of the auxiliary pump detuning; and outputting the cascaded comb light and the dispersive wave from the nonlinear medium to thereby provide the supercontinuum light. Supercontinuum light is typically generated by pumping a nonlinear medium with a very powerful laser, such as a femtosecond laser with a peak optical power of several kilowatts, to thereby generate spectrally broad supercontinuum light. Generally, conventional teachings provide that spectrally broad supercontinuum light cannot be generated when the power is reduced, due to the constraints offered by nonlinear processes. However, the inventors of the present disclosure have realized that a specific combination of input light sources and nonlinear phenomena can be utilized to generate supercontinuum light without the necessity of high-power pump light. A general aim of examples of the present disclosure is to generate a dispersive wave in a nonlinear medium. When pump light enters a nonlinear medium, a dispersive wave can be generated if the conditions are adequate. The pump light and the nonlinear medium defi