CN113839303A - Third harmonic generation system and method - Google Patents
Third harmonic generation system and method Download PDFInfo
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- CN113839303A CN113839303A CN202111217255.XA CN202111217255A CN113839303A CN 113839303 A CN113839303 A CN 113839303A CN 202111217255 A CN202111217255 A CN 202111217255A CN 113839303 A CN113839303 A CN 113839303A
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- 230000003287 optical effect Effects 0.000 claims abstract description 145
- 239000013307 optical fiber Substances 0.000 claims abstract description 81
- 230000010287 polarization Effects 0.000 claims abstract description 64
- 230000008569 process Effects 0.000 claims abstract description 17
- 239000000758 substrate Substances 0.000 claims abstract description 14
- 238000001312 dry etching Methods 0.000 claims abstract description 9
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 24
- 239000004065 semiconductor Substances 0.000 claims description 15
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/10—Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region
- H01S5/1042—Optical microcavities, e.g. cavity dimensions comparable to the wavelength
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- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/35—Non-linear optics
- G02F1/353—Frequency conversion, i.e. wherein a light beam is generated with frequency components different from those of the incident light beams
- G02F1/354—Third or higher harmonic generation
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/02—Structural details or components not essential to laser action
- H01S5/022—Mountings; Housings
- H01S5/0225—Out-coupling of light
- H01S5/02251—Out-coupling of light using optical fibres
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/06—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium
- H01S5/0604—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium comprising a non-linear region, e.g. generating harmonics of the laser frequency
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/06—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium
- H01S5/062—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium by varying the potential of the electrodes
- H01S5/06233—Controlling other output parameters than intensity or frequency
- H01S5/06236—Controlling other output parameters than intensity or frequency controlling the polarisation, e.g. TM/TE polarisation switching
Abstract
The embodiment of the invention discloses a third harmonic generation system and a method. The device comprises a wavelength-adjustable light source, a polarization controller, an optical fiber and an optical microcavity; the wavelength-adjustable light source provides pump light, and the pump light is coupled into the optical fiber; the optical fiber extends from the output end of the polarization controller to the optical microcavity, and the optical fiber extending to the optical microcavity is coupled with the optical microcavity through a cone-shaped structure; the optical microcavity comprises a substrate, a support column and a microdisk cavity; the pump light is coupled into the optical microcavity through the cone-shaped structure; the polarization controller adjusts the polarization state of the pump light in the optical fiber; the wavelength, power and polarization state of the pump light and the distance between the cone-shaped structure and the optical microcavity are adjusted, so that the pump light meets the phase matching condition of third harmonic when being transmitted in the optical microcavity, and the third harmonic is generated. According to the technical scheme of the embodiment of the invention, after the high-quality factor optical microdisk is obtained through dry etching, the continuous light is used for directly pumping the optical microdisk to generate the third harmonic, so that the complex process of generating the third harmonic is simplified.
Description
Technical Field
The embodiment of the invention relates to a laser technology, in particular to a third harmonic generation system and a method.
Background
The whispering gallery mode optical microcavity has an ultrahigh quality factor and a small volume mode, can greatly enhance the interaction between light and a substance, and is an ideal platform for researching nonlinear frequency conversion. Third harmonic generation is a typical third-order nonlinear effect, producing light at three times the frequency of the incident pump light. The third harmonic wave can be used for directly establishing the relation between the near infrared communication wave band and the visible light wave band, so that the method is widely applied to expanding the emission wavelength of a laser light source.
Silica is considered a good carrier for third harmonic generation due to its durability and low optical loss over a wide range of visible spectra in the communications band. However, the conventional silicon oxide microcavity integrated on a chip has problems of low third harmonic conversion efficiency and high threshold. The types of the silicon oxide micro-cavities can be divided into micro-ring core cavities, micro-sphere cavities and micro-disk cavities, laser backflow needs to be introduced for preparation of the micro-ring core cavities and the micro-sphere cavities, the sizes of the micro-ring core cavities and the micro-sphere cavities cannot be controlled, dispersion control is not facilitated, accurate phase matching cannot be achieved, and conversion efficiency is low. The current quality factor of the microdisk cavity is not high and the threshold value is high, and the size of the microdisk cavity is difficult to accurately control by adopting a wet etching process.
Disclosure of Invention
The embodiment of the invention provides a third harmonic generation system and a third harmonic generation method, so that the third harmonic can be generated without adding an additional modulation device, and the process flow for generating the third harmonic is simplified.
In a first aspect, an embodiment of the present invention provides a third harmonic generation system, including a wavelength-tunable light source, a polarization controller, an optical fiber, and an optical microcavity;
the wavelength tunable light source is used for providing pump light, and the pump light is coupled into the optical fiber;
the optical fiber is connected with the input end of the polarization controller;
the optical fiber extends from the output end of the polarization controller to the optical microcavity, the optical fiber extending to the optical microcavity comprises a tapered structure, and the optical fiber is coupled with the optical microcavity through the tapered structure;
the optical microcavity comprises a substrate, a supporting column and a microdisk cavity, wherein the supporting column and the microdisk cavity are positioned on one side of the substrate;
the pump light is coupled into the optical microcavity through the cone-shaped structure;
the polarization controller is used for adjusting the polarization state of the pump light in the optical fiber;
and adjusting the wavelength, power and polarization state of the pump light and the distance between the cone-shaped structure and the optical microcavity, so that the pump light meets the phase matching condition of third harmonic when being transmitted in the optical microcavity, and the third harmonic is generated.
Optionally, the micro disc cavity is shaped as a circular truncated cone;
the included angle between the generatrix of the circular truncated cone and the bottom surface of the circular truncated cone is greater than or equal to 30 degrees and less than or equal to 60 degrees.
Optionally, the third harmonic generation system further includes a first coupler, a photodetector, an oscilloscope, a first spectrometer, and a second spectrometer;
the optical fiber extending from the optical microcavity is connected with the input end of the first coupler, the first output end of the first coupler is connected with the photoelectric detector, the photoelectric detector is connected with the oscilloscope, the second output end of the first coupler is connected with the first spectrometer, and the third output end of the first coupler is connected with the second spectrometer;
the oscilloscope is used for outputting the time domain waveform detected by the photoelectric detector, the first spectrometer is used for measuring the spectrum of the third harmonic, and the second spectrometer is used for measuring the spectrum of the pump light.
Optionally, the third harmonic generation system further includes an optical amplifier disposed on a light path between the wavelength tunable light source and the polarization controller, and configured to amplify the pump light.
Optionally, the optical amplifier is a semiconductor optical amplifier;
the third harmonic generation system further comprises a first collimator, an optical isolator and a second collimator;
the first collimator, the semiconductor optical amplifier, the optical isolator and the second collimator are sequentially arranged between the wavelength-tunable light source and the polarization controller along a light path;
the input end of the first collimator is coupled with the output end of the wavelength-adjustable light source and is used for collimating the pump light and then inputting the collimated pump light into the semiconductor optical amplifier;
the semiconductor optical amplifier is used for amplifying the pump light;
the optical isolator is used for enabling the amplified pump light to be transmitted in a single direction;
the output end of the second collimator is connected with the optical fiber connected to the input end of the polarization controller, and the second collimator is used for coupling the amplified pump light into the optical fiber.
Optionally, the optical amplifier is an optical fiber amplifier;
the wavelength tunable light source is connected with the optical fiber amplifier through the optical fiber;
the optical fiber amplifier is connected with the polarization controller through the optical fiber.
Optionally, the optical system further comprises a second coupler and a power meter;
the input end of the second coupler is connected with the output end of the polarization controller through the optical fiber, the first output end of the second coupler is connected with the power meter, and the optical fiber extends to the optical microcavity through the second output end of the second coupler.
Optionally, the optical system further includes an attenuator, an input end of the attenuator is connected to an output end of the polarization controller through the optical fiber, and an output end of the attenuator extends to the optical microcavity through the optical fiber.
Optionally, the substrate material of the optical microcavity comprises silicon, and the material of the microdisk cavity comprises silicon dioxide;
the optical microcavity is prepared by a dry etching process.
In a second aspect, an embodiment of the present invention further provides a third harmonic generation method, for outputting a third harmonic by using the third harmonic generation system, including:
the wavelength-adjustable light source outputs pump light, and the pump light is coupled into the optical microcavity through an optical fiber;
and adjusting the wavelength, power and polarization state of the pump light and the distance between the cone-shaped structure and the optical microcavity, so that the pump light meets the phase matching condition of third harmonic when being transmitted in the optical microcavity, and the third harmonic is generated.
The third harmonic generation system provided by the embodiment of the invention comprises a wavelength-adjustable light source, a polarization controller, an optical fiber and an optical microcavity; the wavelength-tunable light source can provide pump light, and the pump light is coupled into the optical fiber; the optical fiber passes through the optical microcavity after passing through the polarization controller, wherein the optical microcavity comprises a substrate, a support column and a microdisk cavity, the optical fiber comprises a cone-shaped structure, the pump light and the cone-shaped structure are coupled and enter the optical microcavity, and the polarization controller can adjust the polarization state of the pump light in the optical fiber. The method comprises the steps that an electric signal of 2Vpp and 10Hz is applied to a laser to obtain a wavelength scanning signal with the wavelength adjustable light source being continuous in a small range near a central wavelength, so that the scanning from short wave to long wave is realized, the central wavelength in the wavelength adjustable light source is changed, and a mode of a high-quality factor is further obtained; and then, the wavelength, power and polarization state of the pump light and the distance between the cone-shaped structure and the optical microcavity are adjusted, so that the conditions of high quality factor and strong matching degree of a pump mode and a third harmonic mode are met in the transmission process of the optical microcavity of the pump light, and the third harmonic is generated in a third harmonic system. In the third harmonic generation system provided by this embodiment, after the high-quality factor optical microdisk is obtained by dry etching, the infrared band continuous light is used to directly pump the optical microdisk to generate the third harmonic, and the third harmonic can be generated without additionally adding a modulation device, so that the complex process of generating the third harmonic is simplified, and the theoretical threshold of the third harmonic and the cost of generating the third harmonic are reduced.
Drawings
Fig. 1 is a schematic structural diagram of a third harmonic generation system according to an embodiment of the present invention;
FIG. 2 is a schematic structural diagram of an optical microcavity according to an embodiment of the present invention;
fig. 3 is a schematic structural diagram of another third harmonic generation system according to an embodiment of the present invention;
FIG. 4 is a schematic structural diagram of another third harmonic generation system according to an embodiment of the present invention;
FIG. 5 is a schematic diagram of another third harmonic generation system according to an embodiment of the present invention;
fig. 6 is a schematic structural diagram of another third harmonic generation system according to an embodiment of the present invention;
FIG. 7 is a schematic diagram of another third harmonic generation system according to an embodiment of the present invention;
FIG. 8 is a schematic diagram of another third harmonic generation system according to an embodiment of the present invention;
FIG. 9 is a schematic diagram of the quality factor of an optical microcavity provided in accordance with an embodiment of the present invention;
FIG. 10 is a schematic diagram of an alternative third harmonic generation system according to an embodiment of the present invention;
fig. 11 is a schematic flow chart of a third harmonic generation method according to an embodiment of the present invention;
FIG. 12 is a schematic spectrum diagram of pump light and third harmonic in an embodiment of the present invention;
fig. 13 is an optical micrograph of a microdisk cavity for third harmonic generation provided by an embodiment of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not limiting of the invention. It should be further noted that, for the convenience of description, only some of the structures related to the present invention are shown in the drawings, not all of the structures.
The terminology used in the embodiments of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. It should be noted that the terms "upper", "lower", "left", "right", and the like used in the description of the embodiments of the present invention are used in the angle shown in the drawings, and should not be construed as limiting the embodiments of the present invention. In addition, in this context, it is also to be understood that when an element is referred to as being "on" or "under" another element, it can be directly formed on "or" under "the other element or be indirectly formed on" or "under" the other element through an intermediate element. The terms "first," "second," and the like, are used for descriptive purposes only and not for purposes of limitation, and do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.
Efficient generation of third harmonic in optical microcavities requires phase matching conditions, which can be further expressed as conservation of momentum and conservation of energy. The condition satisfied by conservation of momentum is to find a mode whose wave number kTHIs the wave number k of the pumping modepOne third of (i.e., k)TH＝3kpHowever, in the case of conservation of momentum, since material dispersion usually exists in the optical microcavity, the energy conservation condition is difficult to satisfy if only the fundamental mode is considered, i.e., ω isTH＝3ωpWherein, ω isTHAnd ωpRepresenting the third harmonic and the angular frequency of the pump light, respectively. In order to satisfy the energy conservation condition, it is necessary to compensate the material dispersion by cavity mode dispersion, so that the phase matching with the pump optical mode can be achieved by using the higher-order mode of the third harmonic. An optical microcavity with a high quality factor and a small volume mode is sought, so that the threshold value of generation of third harmonic can be effectively reduced, and on-chip integration is realized.
In the prior art, the end of a half-tapered optical fiber is melted by arc discharge to produce a silica microsphere cavity with a diameter of 57 ± 1 μm and a quality factor of about 107. Three different wavelength third harmonic signals obtained in different microspheres by changing the pump wavelength. However, the microsphere cavity is difficult to control dispersion accurately, and on-chip integration cannot be realized by the manufacturing process based on the optical fiber.
In another prior art, the micro-ring core cavity is manufactured by a laser reflow method, so that the pump light of 1553.9nm generates a third harmonic signal of 517.4nm in the micro-ring core cavity. A third order sum frequency signal of 542nm is generated by inputting 1553nm and 1674nm pump light simultaneously into the micro-ring core cavity. However, the micro-core cavity also has the problems of not being able to control the dispersion precisely and requiring an additional laser reflow process, increasing the complexity of the process.
In another prior art, a microdisk cavity (quality factor of about 10) is fabricated using a wet etch process6) Continuous light output by the infrared tunable laser is modulated into pulse light with low duty ratio and 20ns pulse width, and then the micro-disk cavity is pumped by amplification. Resulting in third harmonic signals with different wavelengths from 512nm to 520nm (the different signals are spaced about 2.5nm apart). However, the quality factor of the microdisk cavities using wet etching is low and it is difficult to precisely control the sample size. The introduction of additional modulation devices also adds significant complexity to the system, which is detrimental to on-chip integration and increases cost.
In order to overcome the defects of the third harmonic generation method based on the silicon oxide microcavity, the embodiment of the invention provides a third harmonic generation system, and the silicon oxide microdisk cavity prepared by a dry etching process overcomes the problems, and firstly, on-chip integration is realized without the steps of changing the size of the microcavity, such as laser reflux and the like; compared with a wet etching process, the quality factor is improved on the basis of small size, and the theoretical threshold of third harmonic is reduced.
Fig. 1 is a schematic structural diagram of a third harmonic generation system according to an embodiment of the present invention. Referring to fig. 1, the third harmonic system provided in this embodiment includes a wavelength tunable light source 10, a polarization controller 20, an optical fiber 30, and an optical microcavity 40; the wavelength tunable light source 10 is used for providing pump light, and the pump light is coupled into the optical fiber 30; the optical fiber 30 is connected with the input end of the polarization controller 20; the optical fiber 30 extends from the output end of the polarization controller 20 to the optical microcavity 40, the optical fiber 30 extending to the optical microcavity 40 including a tapered structure (not shown in fig. 1), the optical fiber 30 being coupled with the optical microcavity 40 through the tapered structure; the optical microcavity 40 includes a substrate 41, and a support pillar 42 and a microdisk cavity 43 located on one side of the substrate; the pump light is coupled into the optical microcavity 40 through the tapered structure; the polarization controller 20 is used for adjusting the polarization state of the pump light in the optical fiber 30; the wavelength, power and polarization state of the pump light and the distance between the cone-shaped structure and the optical microcavity 40 are adjusted, so that the pump light meets the phase matching condition of third harmonic when being transmitted in the optical microcavity 40, and the third harmonic is generated.
The wavelength tunable light source 10 is capable of outputting a continuously tunable pump light within a predetermined wavelength range, for example, a pump light in 1550nm band. The wavelength tunable light source 10, the polarization controller 20, and the optical microcavity 40 can all be connected by an optical fiber 30. The optical microcavity 40 is an on-chip integrated device, which can be integrated on a silicon chip as a substrate, and it can be understood that light transmitted in the optical fiber 30 generates an evanescent field in a tapered structure, so as to realize coupling between the optical microcavity 40 and the optical fiber 30, and the tapered structure can be obtained by melting and tapering the optical fiber. The coupling efficiency of the pump light and the optical microcavity 40 can be adjusted by adjusting the state of the polarization controller 20, wherein the polarization controller 20 may adopt a three-ring or embedded polarization controller, which is not limited in the embodiment of the present invention.
Optionally, the microdisk cavity 43 is shaped as a circular truncated cone; the included angle between the generatrix of the circular truncated cone and the bottom surface of the circular truncated cone is more than or equal to 30 degrees and less than or equal to 60 degrees.
Fig. 2 is a schematic structural diagram of an optical microcavity according to an embodiment of the present invention. Referring to fig. 2, the optical microcavity 40 includes a substrate 41 and support posts 42 and a microdisk cavity 43 located on one side of the substrate. In the present embodiment, the microdisk cavity 43 is in the shape of a truncated cone, and the truncated cone is coupled to the optical fiber 30 through a tapered structure of the optical fiber. The included angle between the generatrix of the circular truncated cone and the bottom surface of the circular truncated cone is more than or equal to 30 degrees and less than or equal to 60 degrees.
The wavelength, power and polarization state of the pump light and the distance between the cone-shaped structure and the optical microcavity are adjusted, so that the pump light is transmitted in the optical microcavity to meet the phase matching condition of third harmonic, the third harmonic is generated, and the wavelength-adjustable light source can be a laser. Firstly, outputting pump light through a laser, setting the pump light to be coupled into an optical microcavity at low power, and applying an electric signal of 2Vpp and 10Hz on the laser to enable a wavelength-tunable light source to carry out continuous wavelength scanning in a small range near a central wavelength; secondly, scanning the central wavelength of the laser to obtain a mode with a high quality factor; thirdly, continuously adjusting the polarization of the pump light and the coupling between the microcavity and the fiber cone until the mode is in a right coupling state; and finally, closing the wavelength scanning of the pump light, setting the wavelength of the laser at a blue detuning position far away from the pump mode, and gradually increasing the wavelength of the laser after increasing the power of the pump light until a stable third harmonic signal is generated.
Specifically, the high quality factor can be obtained by turning on the wavelength scanning of the laser, so that the laser continuously and repeatedly scans in a small range near the central wavelength λ, and observing the transmission line on the oscilloscope under the condition of keeping the scanning frequency at 10 Hz. In the range of one rising edge, the laser can scan from short to long wavelengths, and when the wavelength and cavity mode are matched, the Lorentzian transmission spectrum can be observed on an oscilloscope. The center wavelength is changed to search for a mode with a narrower half-height width, so that a mode with a high quality factor is determined. The quality factor can be expressed by a Q value. The Q value can be expressed as the ratio of the resonance wavelength to the full width at half maximum at that location.
The just-coupled state refers to a state in which the coupling position of the optical fiber and the microdisc cavity, and the polarization state of the pump light are adjusted so that the lowest point of the transmission peak is 0.
According to the technical scheme of the embodiment, the pump light is provided by the wavelength-adjustable light source, the pump light enters the optical microcavity through the coupling of the conical structure in the optical fiber, the polarization state of the pump light is adjusted by the polarization controller, so that the coupling efficiency of the pump light and the optical microcavity is changed, and the continuous wavelength scanning signal of the wavelength-adjustable light source in a small range near the central wavelength is obtained by applying electric signals of 2Vpp and 10Hz on the laser, so that the scanning from short wave to long wave is realized, the central wavelength in the wavelength-adjustable light source is changed, and the mode of a high-quality factor is further obtained; and then, the wavelength, power and polarization state of the pump light and the distance between the cone-shaped structure and the optical microcavity are adjusted, so that the conditions of high quality factor and strong matching degree of a pump mode and a third harmonic mode are met in the transmission process of the optical microcavity of the pump light, and the third harmonic is generated in a third harmonic system. The complex process of generating the third harmonic is simplified, and the theoretical threshold value of the third harmonic and the cost of generating the third harmonic are reduced.
On the basis of the above technical solution, fig. 3 is a schematic structural diagram of another third harmonic generation system provided in the embodiment of the present invention. Referring to fig. 3, optionally, the third harmonic generation system further comprises a first coupler 50, a photodetector 60, an oscilloscope 70, a first spectrometer 80, and a second spectrometer 90; the optical fiber 30 extending from the optical microcavity 40 is connected to the input end of the first coupler 50, the first output end of the first coupler 50 is connected to the photodetector 60, the photodetector 60 is connected to the oscilloscope 70, the second output end of the first coupler 50 is connected to the first spectrometer 80, and the third output end of the first coupler 50 is connected to the second spectrometer 90; the oscilloscope 70 is used to output the time domain waveform detected by the photodetector 60, the first spectrometer 80 is used to measure the spectrum of the third harmonic, and the second spectrometer 90 is used to measure the spectrum of the pump light.
It can be understood that, in order to verify whether the third harmonic system provided in the embodiment of the present invention generates the third harmonic, a test is required to be performed to determine whether the third harmonic is generated by observing the time domain waveform of the oscilloscope 70 and the spectrum measured by the first spectrometer 80, and to determine the signal of the pump light by the spectrum measured by the second spectrometer 90. In practical implementation, with reference to fig. 3, the first coupler 50 may be a three-port fiber coupler, and the magnitudes of the splitting ratios of the first output port, the second output port, and the third output port are not limited. Fig. 4 is a schematic structural diagram of another third harmonic generation system according to an embodiment of the present invention. Referring to fig. 4, the first coupler 50 may be replaced by a combination of two three-port sub-couplers, a first sub-coupler 51 and a second sub-coupler 52. In the embodiment of the present invention, the first coupler 50 formed in two ways functions in the same way in the specific implementation process.
Fig. 5 is a schematic structural diagram of another third harmonic generation system according to an embodiment of the present invention. Referring to fig. 5, optionally, the third harmonic system further includes an optical amplifier 11 disposed on the optical path between the wavelength tunable light source 10 and the polarization controller 20, for amplifying the pump light.
It is understood that in practical implementation, the power of the pump light output by the wavelength tunable light source 10 may be small and may not reach the threshold power for exciting the pump light that can generate the third harmonic, and therefore, the optical amplifier 11 may be disposed on the optical path between the wavelength tunable light source 10 and the polarization controller 20 to amplify the power of the pump light to be above the threshold power.
Fig. 6 is a schematic structural diagram of another third harmonic generation system according to an embodiment of the present invention. Referring to fig. 6, optionally, the optical amplifier is a semiconductor optical amplifier; the third harmonic generation system further includes a first collimator 12, an optical isolator 13, and a second collimator 14; the first collimator 12, the semiconductor optical amplifier, the optical isolator 13 and the second collimator 14 are sequentially arranged along a light path between the wavelength-tunable light source 10 and the polarization controller 20; the input end of the first collimator 12 is coupled with the output end of the wavelength-tunable light source 10, and is used for collimating the pump light and inputting the collimated pump light into the semiconductor optical amplifier; the semiconductor optical amplifier is used for amplifying the pump light; the optical isolator 13 is used for unidirectional transmission of the amplified pump light; the output of the second collimator 14 is connected to an optical fiber 30 connected to the input of the polarization controller 20, and the second collimator 14 is used to couple the amplified pump light into the optical fiber 30.
It can be understood that the semiconductor optical amplifier generally transmits a light beam in a free space, the wavelength tunable light source 10 can output pump light through the optical fiber 30, the pump light is converted into parallel light in the free space after passing through the first collimator 12, the pump light is gain-amplified after the optical power is increased by the semiconductor optical amplifier, the amplified pump light can only be transmitted along the forward direction after passing through the optical isolator 13, the semiconductor optical amplifier is prevented from being damaged by back-reflected light, and the free space parallel light after power amplification is re-coupled into the optical fiber 30 for continuous transmission after passing through the second collimator 14.
In another embodiment, optionally, the optical amplifier 11 is a fiber amplifier; the wavelength tunable light source 10 is connected to the optical fiber amplifier through an optical fiber 30; the fiber amplifier is connected to the polarization controller 20 through an optical fiber 30.
It is understood that the optical amplifier 11 may also be a fiber amplifier, and the optical path is transmitted only in the optical fiber 30, so as to reduce the coupling difficulty of the optical path. In other embodiments, other types of optical amplifiers may also be selected, which is not limited in this embodiment of the present invention.
Fig. 7 is a schematic structural diagram of another third harmonic generation system according to an embodiment of the present invention. Referring to fig. 7, optionally, the third harmonic generation system further includes a second coupler 100 and a power meter 110; the input end of the second coupler 100 is connected to the output end of the polarization controller 20 through the optical fiber 30, the first output end of the second coupler 100 is connected to the power meter 110, and the optical fiber 30 extends to the optical microcavity 40 through the second output end of the second coupler 100.
It is understood that the second coupler 100 is located after the polarization controller 20 and before the optical microcavity 40, the output end of the second coupler may be connected to the power meter 110, and the second coupler 100 may select a different fiber coupler according to practical situations, which is not limited in the embodiment of the present invention. The power meter 110 may detect the power of the pump light after passing through the second coupler 100.
Fig. 8 is a schematic structural diagram of another third harmonic generation system according to an embodiment of the present invention. Referring to FIG. 8, optionally, the third harmonic generation system further includes an attenuator 120, an input of the attenuator 120 is connected to an output of the polarization controller 20 through an optical fiber 30, and an output of the attenuator 120 extends through the optical fiber to the optical microcavity 40.
It will be appreciated that the attenuator 120 may be used to adjust the output power of the pump light provided by the wavelength tunable light source 10.
Optionally, the substrate 41 material of the optical microcavity 40 in the third harmonic generation system comprises silicon, and the material of the microdisk cavity 43 comprises silicon dioxide; the optical microcavity 40 is fabricated using a dry etching process.
It can be understood that the silicon oxide material has the specific low absorption energy consumption, can obtain better quality factors, reduces the threshold value generated by third harmonic, can be integrated on a chip, and is applied to the field of integrating silicon oxide microcavities on the chip. The microdisk cavity 43 is made of a silicon dioxide material that can be well matched to the frequency of the pump light provided by the wavelength tunable light source. The quality factor of the optical microcavity 40 prepared by the dry etching process can be improved by one order of magnitude, the mode area is reduced to 2/3, and the theoretical threshold of the third harmonic wave is reduced by more than three orders of magnitude without considering the mode matching; in addition, the repeatability of the dry etching process is strong, and the size of the optical microcavity 40 is controllable and consistent.
Illustratively, fig. 9 is a schematic quality factor diagram of an optical microcavity provided by an embodiment of the present invention. Referring to fig. 9, the thickness of the silicon dioxide microdisk cavity prepared by the dry etching process is 2 μm, the diameter of the silicon dioxide microdisk cavity is 80 μm, and the included angle between the circular truncated cone generatrix of the microdisk cavity and the bottom surface of the circular truncated cone is 45 °. Quality factor of optical microcavity 40 (about 1.5 × 10)7) The black line is a curve obtained by Lorentz fitting.
It should be noted that the foregoing are only exemplary embodiments of the present invention, and in practical implementation, a combination of optical devices may be selected according to practical requirements to meet practical application requirements. Illustratively, fig. 10 is a schematic diagram of a system for generating third harmonic according to an embodiment of the present invention. The present embodiment provides a specific example based on the above embodiments. Referring to fig. 10, the third harmonic generation system includes a wavelength tunable light source 10, an amplifier 11, a polarization controller 20, an optical fiber 30, an optical microcavity 40, a first coupler 50, a photodetector 60, an oscilloscope 70, a first spectrometer 80, a second spectrometer 90, a second coupler 100, a power meter 110, and an attenuator 120. The wavelength-tunable light source 10 is a 1550nm tunable external cavity diode laser (ECDL, New Focus TBL6328), the optical amplifier 11 is an erbium-doped fiber amplifier (EDFA), the pump light sequentially passes through the optical amplifier 11 to amplify the power of the pump light, sequentially passes through the polarization controller 20(FPC), the attenuator 120(VOA) and the optical microcavity 40, the attenuator 120 divides the pump light into two paths through the second coupler 100, one path is connected with the dynamometer to collect the power of the pump light, and the other path enters the optical microcavity 40. The optical microcavity 40 is a silica microdisk cavity with a diameter of 80 μm, a thickness of 2 μm, and an inclination angle of about 45 °. The pump light passing through the optical microcavity 40 is output in three paths after passing through the first coupler 50. The first path is detected by a photodetector 60(PD), and the oscilloscope 70(OSC) is used to monitor the power change of the transmitted pump laser, the second path is used to collect the spectrum of the third harmonic by a first spectrometer 80, and the third path is used to collect the pump light signal and the generated raman laser signal by a second spectrometer 90.
Fig. 11 is a schematic flow chart of a third harmonic generation method according to an embodiment of the present invention, where the third harmonic is generated by any one of the third harmonic generation systems according to the above embodiments, and referring to fig. 11, the third harmonic generation method includes:
and S110, outputting pump light by the wavelength-adjustable light source, wherein the pump light is coupled into the optical microcavity through an optical fiber.
And S120, adjusting the wavelength, power and polarization state of the pump light and the distance between the cone-shaped structure and the optical microcavity, so that the pump light meets the phase matching condition of third harmonic when being transmitted in the optical microcavity, and the third harmonic is generated.
Illustratively, in one embodiment of the present invention, first, a laser outputs pump light, the pump light is configured to be coupled into the optical microcavity at low power, and a 2Vpp, 10Hz electrical signal is applied to the laser, so that the wavelength tunable light source performs continuous wavelength scanning in a small range around the center wavelength; secondly, scanning the central wavelength of the laser to obtain a mode with a high quality factor; thirdly, continuously adjusting the polarization of the pump light and the coupling between the microcavity and the fiber cone until the mode is in a right coupling state; and finally, closing the wavelength scanning of the pump light, setting the wavelength of the laser at a blue detuning position far away from the pump mode, and gradually increasing the wavelength of the laser after increasing the power of the pump light until a stable third harmonic signal is generated. FIG. 12 is a diagram showing the spectra of the pump light and the third harmonic in an embodiment of the present invention, in which the wavelength of the pump light is 1561.0nm, and the wavelength of the generated third harmonic is 520.06nm, which is different from the expected wavelength of the third harmonic (520.33nm) by only 0.05%. Fig. 13 is an optical micrograph of a microdisk cavity for generating a third harmonic wave according to the present embodiment, wherein a portion of the third harmonic wave can be observed.
It is to be noted that the foregoing is only illustrative of the preferred embodiments of the present invention and the technical principles employed. It will be understood by those skilled in the art that the present invention is not limited to the particular embodiments described herein, but is capable of various obvious changes, rearrangements and substitutions as will now become apparent to those skilled in the art without departing from the scope of the invention. Therefore, although the present invention has been described in greater detail by the above embodiments, the present invention is not limited to the above embodiments, and may include other equivalent embodiments without departing from the spirit of the present invention, and the scope of the present invention is determined by the scope of the appended claims.
Claims (10)
1. A third harmonic generation system is characterized by comprising a wavelength-tunable light source, a polarization controller, an optical fiber and an optical microcavity;
the wavelength tunable light source is used for providing pump light, and the pump light is coupled into the optical fiber;
the optical fiber is connected with the input end of the polarization controller;
the optical fiber extends from the output end of the polarization controller to the optical microcavity, the optical fiber extending to the optical microcavity comprises a tapered structure, and the optical fiber is coupled with the optical microcavity through the tapered structure;
the optical microcavity comprises a substrate, a supporting column and a microdisk cavity, wherein the supporting column and the microdisk cavity are positioned on one side of the substrate;
the pump light is coupled into the optical microcavity through the cone-shaped structure;
the polarization controller is used for adjusting the polarization state of the pump light in the optical fiber;
and adjusting the wavelength, power and polarization state of the pump light and the distance between the cone-shaped structure and the optical microcavity, so that the pump light meets the phase matching condition of third harmonic when being transmitted in the optical microcavity, and the third harmonic is generated.
2. The third harmonic generation system of claim 1 wherein the microdisk cavity is shaped as a circular truncated cone;
the included angle between the generatrix of the circular truncated cone and the bottom surface of the circular truncated cone is greater than or equal to 30 degrees and less than or equal to 60 degrees.
3. A third harmonic generation system according to claim 1, further comprising a first coupler, a photodetector, an oscilloscope, a first spectrometer, and a second spectrometer;
the optical fiber extending from the optical microcavity is connected with the input end of the first coupler, the first output end of the first coupler is connected with the photoelectric detector, the photoelectric detector is connected with the oscilloscope, the second output end of the first coupler is connected with the first spectrometer, and the third output end of the first coupler is connected with the second spectrometer;
the oscilloscope is used for outputting the time domain waveform detected by the photoelectric detector, the first spectrometer is used for measuring the spectrum of the third harmonic, and the second spectrometer is used for measuring the spectrum of the pump light.
4. A third harmonic generation system according to claim 1 further comprising an optical amplifier optically disposed between the wavelength tunable light source and the polarization controller for amplifying the pump light.
5. A third harmonic generation system as in claim 4 wherein the optical amplifier is a semiconductor optical amplifier;
the third harmonic generation system further comprises a first collimator, an optical isolator and a second collimator;
the first collimator, the semiconductor optical amplifier, the optical isolator and the second collimator are sequentially arranged between the wavelength-tunable light source and the polarization controller along a light path;
the input end of the first collimator is coupled with the output end of the wavelength-adjustable light source and is used for collimating the pump light and then inputting the collimated pump light into the semiconductor optical amplifier;
the semiconductor optical amplifier is used for amplifying the pump light;
the optical isolator is used for enabling the amplified pump light to be transmitted in a single direction;
the output end of the second collimator is connected with the optical fiber connected to the input end of the polarization controller, and the second collimator is used for coupling the amplified pump light into the optical fiber.
6. A third harmonic generation system according to claim 4 wherein the optical amplifier is a fiber amplifier;
the wavelength tunable light source is connected with the optical fiber amplifier through the optical fiber;
the optical fiber amplifier is connected with the polarization controller through the optical fiber.
7. A third harmonic generation system according to claim 1 further comprising a second coupler and a power meter;
the input end of the second coupler is connected with the output end of the polarization controller through the optical fiber, the first output end of the second coupler is connected with the power meter, and the optical fiber extends to the optical microcavity through the second output end of the second coupler.
8. A third harmonic generation system as in claim 1 further comprising an attenuator, an input of the attenuator being connected to an output of the polarization controller through the optical fiber, an output of the attenuator extending through the optical fiber to the optical microcavity.
9. A third harmonic generation system as in claim 1 wherein the substrate material of the optical microcavity comprises silicon, and the material of the microdisc cavity comprises silicon dioxide;
the optical microcavity is prepared by a dry etching process.
10. A third harmonic generation method for outputting a third harmonic by using the third harmonic generation system according to any one of claims 1 to 9, comprising:
the wavelength-adjustable light source outputs pump light, and the pump light is coupled into the optical microcavity through an optical fiber;
and adjusting the wavelength, power and polarization state of the pump light and the distance between the cone-shaped structure and the optical microcavity, so that the pump light meets the phase matching condition of third harmonic when being transmitted in the optical microcavity, and the third harmonic is generated.
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115981070A (en) * | 2022-12-29 | 2023-04-18 | 南京大学 | Echo wall mode microcavity, dispersion control method thereof and octave optical comb generation device |
Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2015103622A1 (en) * | 2014-01-06 | 2015-07-09 | Ipg Photonics Corporation | Ultra-high power single mode green fiber laser operating in continuous wave and quasi-continuous wave regimes |
| CN104977775A (en) * | 2015-07-09 | 2015-10-14 | 华中科技大学 | Optical microcavity optical frequency comb generation apparatus and generation method based on injected seed light |
| CN109672075A (en) * | 2019-02-18 | 2019-04-23 | 哈尔滨工程大学 | A kind of preparation method of multi-wavelength optical fiber laser and its curing nickel mode-locking device |
| CN109739060A (en) * | 2019-03-11 | 2019-05-10 | 南京大学 | A kind of optical frequency com generation system |
| CN111600192A (en) * | 2020-06-15 | 2020-08-28 | 南京大学 | Optical soliton generating system |
| CN112882310A (en) * | 2021-02-25 | 2021-06-01 | 电子科技大学 | Kerr optical comb-based arbitrary high-order modulation format signal phase regeneration method |
| CN216016001U (en) * | 2021-10-19 | 2022-03-11 | 南京大学 | Third harmonic generation system |
-
2021
- 2021-10-19 CN CN202111217255.XA patent/CN113839303A/en active Pending
Patent Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2015103622A1 (en) * | 2014-01-06 | 2015-07-09 | Ipg Photonics Corporation | Ultra-high power single mode green fiber laser operating in continuous wave and quasi-continuous wave regimes |
| CN104977775A (en) * | 2015-07-09 | 2015-10-14 | 华中科技大学 | Optical microcavity optical frequency comb generation apparatus and generation method based on injected seed light |
| CN109672075A (en) * | 2019-02-18 | 2019-04-23 | 哈尔滨工程大学 | A kind of preparation method of multi-wavelength optical fiber laser and its curing nickel mode-locking device |
| CN109739060A (en) * | 2019-03-11 | 2019-05-10 | 南京大学 | A kind of optical frequency com generation system |
| CN111600192A (en) * | 2020-06-15 | 2020-08-28 | 南京大学 | Optical soliton generating system |
| CN112882310A (en) * | 2021-02-25 | 2021-06-01 | 电子科技大学 | Kerr optical comb-based arbitrary high-order modulation format signal phase regeneration method |
| CN216016001U (en) * | 2021-10-19 | 2022-03-11 | 南京大学 | Third harmonic generation system |
Non-Patent Citations (1)
| Title |
|---|
| 向望华;李楠;崔宇;任芳;白扬博;张贵忠;: "Er~(3+)-Yb~(3+)共掺杂光纤环型腔被动谐波锁模激光器", 强激光与粒子束, no. 11, 15 November 2008 (2008-11-15) * |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115981070A (en) * | 2022-12-29 | 2023-04-18 | 南京大学 | Echo wall mode microcavity, dispersion control method thereof and octave optical comb generation device |
| CN115981070B (en) * | 2022-12-29 | 2023-12-12 | 南京大学 | Whispering gallery mode microcavity, dispersion control method thereof and octave optical comb generating device |
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