CN115000806A - Tunable ultra-narrow linewidth laser system based on optical frequency comb - Google Patents
Tunable ultra-narrow linewidth laser system based on optical frequency comb Download PDFInfo
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- CN115000806A CN115000806A CN202210617838.XA CN202210617838A CN115000806A CN 115000806 A CN115000806 A CN 115000806A CN 202210617838 A CN202210617838 A CN 202210617838A CN 115000806 A CN115000806 A CN 115000806A
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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
- H01S5/068—Stabilisation of laser output parameters
- H01S5/0683—Stabilisation of laser output parameters by monitoring the optical output parameters
- H01S5/0687—Stabilising the frequency of the laser
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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
- H01S5/005—Optical components external to the laser cavity, specially adapted therefor, e.g. for homogenisation or merging of the beams or for manipulating laser pulses, e.g. pulse shaping
- H01S5/0085—Optical components external to the laser cavity, specially adapted therefor, e.g. for homogenisation or merging of the beams or for manipulating laser pulses, e.g. pulse shaping for modulating the output, i.e. the laser beam is modulated outside the laser cavity
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Abstract
An optical frequency comb based tunable ultra-narrow linewidth laser system comprising: a tunable laser for emitting laser light; a light splitting device that splits the laser light into transmitted light and reflected light; the frequency shift device is used for adjusting the frequency of the transmitted light to obtain experimental light; the adjusting device is used for adjusting the power of frequency comb light and the power of reflected light from the optical frequency comb, so that the adjusted frequency comb light and the adjusted reflected light generate beat frequency to obtain a target beat frequency electric signal; the signal processing device is used for carrying out power amplification on the target beat frequency electric signal to obtain a first reference signal and obtaining the frequency of the target beat frequency electric signal according to the first reference signal; the microwave signal source is used for sending out a frequency-adjustable microwave signal; the servo device is used for controlling the tunable laser in a feedback mode according to the frequency of the microwave signal, so that the frequency of the target beat frequency electric signal is locked on the frequency of the microwave signal, and the frequency of the experimental light is further controlled; and the signal control device is used for controlling the microwave signal source, the servo device and the frequency shift device.
Description
Technical Field
The invention relates to the technical field of tunable laser, in particular to a tunable ultra-narrow linewidth laser system based on an optical frequency comb.
Background
A narrow linewidth tunable laser is a laser with a narrow linewidth and a continuously tunable frequency. . In experiments such as atom, molecule and optics, the narrow linewidth tunable laser has very important application. However, since the frequency variation range of the tunable laser with a narrow line width is far beyond the detection range of the conventional electronic device, the system for implementing the frequency sweeping function of the tunable laser with a narrow line width has more or less problems of complicated device, insufficient frequency continuity, small frequency adjustment range, and the like.
Disclosure of Invention
It is therefore a primary object of the present invention to provide an optical frequency comb based tunable ultra narrow linewidth laser system, which is intended to at least partially solve at least one of the mentioned technical problems.
According to an embodiment of the present invention, there is provided a tunable ultra-narrow linewidth laser system based on an optical frequency comb, including:
a tunable laser adapted to emit laser light;
a light splitting device adapted to split the laser light into transmitted light and reflected light;
the frequency shift device is suitable for adjusting the frequency of the transmitted light to obtain experimental light;
the adjusting device is suitable for adjusting the power of frequency comb light and the power of reflected light from the optical frequency comb, and enabling the adjusted frequency comb light and the adjusted reflected light to generate beat frequency to obtain a target beat frequency electric signal;
the signal processing device is suitable for performing power amplification on the target beat frequency electric signal, obtaining a first reference signal and obtaining the frequency of the target beat frequency electric signal according to the first reference signal;
the microwave signal source is suitable for emitting a microwave signal with adjustable frequency, wherein the difference between the initial frequency of the microwave signal and the frequency of the target beat frequency electric signal is within a preset range;
the servo device is suitable for feedback control of the tunable laser according to the frequency of the microwave signal, so that the frequency of the target beat frequency electric signal is locked on the frequency of the microwave signal, and the frequency of the experimental light is further controlled; and
the signal control device is suitable for controlling the microwave signal source, the servo device and the frequency shift device;
the frequency of the microwave signal is continuously adjusted by using a microwave signal source, so that the frequency of the experimental light is continuously changed under the feedback control of the servo device until the servo device is in a state close to the unlocking state, under the condition that the servo device is in the state close to the unlocking state, the signal control device is configured to adjust the tunable laser by controlling the servo device, so that the frequency of the laser is hopped, and further the frequency of the transmission light is hopped, and the signal control device controls the frequency shifting device to adjust the frequency of the transmission light hopped, so that the frequency of the hopped transmission light is compensated, and the experimental light with continuous frequency is obtained.
According to an embodiment of the invention, the adjustment device comprises:
the power adjusting unit is suitable for adjusting the power of the frequency comb light to obtain first power adjusting frequency comb light;
the adjustable attenuation sheet is suitable for adjusting the power sum of the reflected light to obtain power-adjusted reflected light;
a beam combining unit adapted to combine the first power-modulated frequency comb light and the power-modulated reflected light;
and the photoelectric detection unit is suitable for adjusting the frequency combing light and the reflected light according to the first power to obtain an initial beat frequency electric signal comprising a target beat frequency electric signal.
According to an embodiment of the present invention, a photodetecting unit includes:
and the light splitting module is suitable for splitting the first power adjustment frequency beam light to obtain second power adjustment frequency comb light, and the second power adjustment frequency comb light and the power adjustment reflected light generate beat frequency to obtain beat frequency light.
According to an embodiment of the present invention, the photodetecting unit further comprises:
a fiber collimator adapted to couple beat light;
an optical fiber adapted to transmit beat light;
and the first photoelectric detector is suitable for detecting the beat frequency light from the optical fiber to obtain an initial beat frequency electric signal comprising a target beat frequency electric signal.
According to an embodiment of the present invention, the photodetecting unit further comprises:
the aperture diaphragm is suitable for filtering beat frequency light;
and the second photoelectric detector is used for detecting the filtered beat frequency light to obtain an initial beat frequency electric signal comprising a target beat frequency electric signal.
According to an embodiment of the present invention, a signal control apparatus includes:
the time sequence control and voltage output unit is suitable for synchronizing the frequency of the microwave signal source and the frequency of the target beat frequency electric signal, controlling the servo device and outputting a control instruction of the frequency shift device under the condition that the servo device is in a state close to an unlocking state;
and the voltage-controlled oscillator controls the frequency shift device according to the control instruction of the frequency shift device output by the time sequence control and voltage output unit.
According to the embodiment of the invention, the timing control and voltage output unit is an NI board card, an analog card, a signal generator, or an arbitrary wave generator.
According to an embodiment of the present invention, a signal processing apparatus includes:
the filter is suitable for filtering the initial beat frequency electric signal comprising the target beat frequency electric signal to obtain a target beat frequency electric signal;
the radio frequency amplifier is suitable for amplifying the power of the target beat frequency electric signal;
a power divider adapted to divide a power-amplified target signal into a first reference signal and a second reference signal;
and the spectrum analyzer is suitable for detecting the frequency of the second reference signal so as to obtain the power of the target beat frequency electric signal.
According to an embodiment of the invention, the frequency shifting means is an acousto-optic modulator or an electro-optic modulator.
According to an embodiment of the invention, the beam splitting device is a planar glass plate or a second depolarizing beam splitting plate.
According to the embodiment of the invention, the transmission light obtained by the laser emitted by the tunable laser through the light splitting device and the external frequency comb light are adjusted by the adjusting device to obtain the target beat frequency signal, and the signal control device controls the microwave signal source, the servo device and the frequency shifting device to obtain the experimental light with continuously changing frequency according to the frequency information in the target beat frequency signal. The invention is based on frequency combing light and some simple photoelectronic devices, and realizes the ultra-narrow line width tunable laser with wide frequency adjusting range and continuously variable frequency.
According to the embodiment of the invention, the servo device is utilized to perform feedback control on the tunable laser according to the frequency of the microwave signal, so that the frequency of the target beat frequency electrical signal is locked on the frequency of the microwave signal (i.e. the frequency of the tunable laser is locked on the frequency comb light), and as the frequency comb light has the property of ultra-narrow line width, the laser generated by the tunable laser also has the property of ultra-narrow line width (namely, the order of magnitude of less than or equal to 10 kHz). After locking, the frequency stability of the frequency comb light and the laser generated by the tunable laser is in the same magnitude, and the line width can even reach the sub-hertz magnitude.
According to the embodiment of the invention, the frequency of the microwave signal is continuously adjusted through the microwave signal source, so that the frequency of the experimental light is continuously changed under the feedback control of the servo device until the servo device is in a state close to the unlocking state, under the condition that the servo device is in the state close to the unlocking state, the signal control device controls the servo device to adjust the tunable laser, the frequency of the laser jumps, and further the frequency of the transmission light jumps, and meanwhile, the signal control device controls the frequency shift device to adjust the frequency of the transmission light which jumps, so that the frequency of the transmission light which jumps is compensated, the experimental light with continuous frequency is obtained, and the whole frequency sweeping process is completed. Because the servo device is always in a working state in the frequency sweeping process, the laser frequency emitted by the tunable laser is always actively locked, and the tunable laser is ensured to have the property of ultra-narrow line width in the tuning process.
According to the tunable ultra-narrow linewidth laser system based on the optical frequency comb, the frequency of the tunable laser can be continuously tuned at high speed until the tunable laser jumps to the mode. If the self-limit of the tunable laser is not considered, the technical scheme provided by the invention can provide the tunable laser with wider frequency tuning range.
The tunable ultra-narrow linewidth laser system based on the optical frequency comb provided by the embodiment of the invention is suitable for all tunable lasers.
According to the tunable ultra-narrow linewidth laser system based on the optical frequency comb, laser emitted by the tunable laser passes through the light splitting device to obtain transmitted light, the transmitted light and external frequency comb light are adjusted through the adjusting device to obtain a target beat frequency signal, then the signal control device controls the microwave signal source, the servo device and the frequency shift device to obtain experimental light with continuously changing frequency according to frequency information in the target beat frequency signal, and the ultra-narrow linewidth tunable laser with the wide frequency adjusting range and the continuously changing frequency is achieved.
Drawings
In order to more clearly illustrate the embodiments or technical solutions of the present invention, the drawings used in the embodiments or technical solutions of the present invention will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without creative efforts.
Fig. 1 schematically illustrates an optical path diagram of a tunable ultra-narrow linewidth laser system based on an optical frequency comb;
fig. 2 schematically shows an optical path diagram of the photodetecting unit; and
fig. 3 schematically shows a process diagram of the frequency variation in the frequency domain of a tunable laser based on an optical frequency comb.
Reference numerals:
1-tunable laser
2-light splitting device
3-frequency shift device
4-regulating device
41-Power regulating Unit
42-tunable attenuation sheet
43-beam combining unit
44-photodetector Unit
441-light splitting module
442-optical fiber collimator
443-optical fiber
444-first photodetector
5-Signal processing device
51-filter
52-radio frequency amplifier
53-Power splitter
54-Spectrum analyzer
6-servo device
7-Signal control device
71-timing control and voltage output unit
72-voltage controlled oscillator
8-microwave signal source
Detailed Description
Embodiments of the present invention will be described below with reference to the accompanying drawings. It is to be understood that such description is merely illustrative and not intended to limit the scope of the present invention. In the following detailed description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the embodiments of the invention. It may be evident, however, that one or more embodiments may be practiced without these specific details. Moreover, in the following description, descriptions of well-known structures and techniques are omitted so as to not unnecessarily obscure the concepts of the present invention.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The terms "comprises," "comprising," and the like, as used herein, specify the presence of stated features, steps, operations, and/or components, but do not preclude the presence or addition of one or more other features, steps, operations, or components.
All terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art unless otherwise defined. It is noted that the terms used herein should be interpreted as having a meaning that is consistent with the context of this specification and should not be interpreted in an idealized or overly formal sense.
Where a convention analogous to "at least one of A, B and C, etc." is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., "a system having at least one of A, B and C" would include but not be limited to systems that have a alone, B alone, C alone, a and B together, a and C together, B and C together, and/or A, B, C together, etc.). Where a convention analogous to "A, B or at least one of C, etc." is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., "a system having at least one of A, B or C" would include but not be limited to systems that have a alone, B alone, C alone, a and B together, a and C together, B and C together, and/or A, B, C together, etc.).
The invention provides a tunable ultra-narrow linewidth laser system, aiming at the problems that in the prior tunable laser technology, when the frequency variation range of a narrow linewidth tunable laser is far beyond the detection range of the prior electronic equipment, a system for realizing the frequency sweeping function of the narrow linewidth tunable laser is more or less complicated in device, insufficient in frequency continuity emitted by the narrow linewidth tunable laser, small in frequency adjusting range of the narrow linewidth tunable laser and the like. The tunable ultra-narrow linewidth laser system obtains the transmitted light by passing the laser emitted by the tunable laser through the light splitting device, and adjusts the transmitted light and the external frequency comb light through the adjusting device to obtain the target beat frequency signal, and then the signal control device obtains the experimental light with continuously changed frequency by controlling the microwave signal source, the servo device and the frequency shifting device according to the frequency information in the target beat frequency signal, thereby realizing the ultra-narrow linewidth tunable laser with wide frequency adjusting range and continuously changed frequency.
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the accompanying drawings in combination with the embodiments.
Fig. 1 schematically illustrates an optical path diagram of an optical frequency comb based tunable ultra-narrow linewidth laser system.
According to some embodiments of the present invention, as shown in fig. 1, an optical path of a tunable ultra-narrow linewidth laser system includes: the device comprises a tunable laser 1, a light splitting device 2, a frequency shift device 3, an adjusting device 4, a signal processing device 5, a microwave signal source 8, a servo device 6 and a signal control device 7. The tunable laser 1 is adapted to emit laser light, and the tunable laser 1 may be any tunable laser, such as an external cavity semiconductor laser. The light splitting means 2 is adapted to split the laser light into transmitted light and reflected light, wherein the power of the transmitted light is larger than the power of the reflected light. The frequency shifting device 3 is suitable for adjusting the frequency of the transmitted light to obtain the experimental light. The adjusting device 4 is adapted to adjust the power of the frequency comb light and the power of the reflected light from the optical frequency comb, and beat the adjusted frequency comb light and the adjusted reflected light to obtain a target beat frequency electric signal. The signal processing device 5 is adapted to perform power amplification on the target beat frequency electrical signal, obtain a first reference signal, and obtain the frequency of the target beat frequency electrical signal according to the first reference signal. The microwave signal source 8 is adapted to emit a frequency-tunable microwave signal, wherein a difference between an initial frequency of the microwave signal and a frequency of the target beat frequency electrical signal is within a preset range, that is, the initial frequency of the microwave signal is substantially the same as the frequency of the target beat frequency electrical signal. The servo means 6 is adapted to feedback-control the tunable laser in accordance with the frequency of the microwave signal, so that the frequency of the target beat frequency electrical signal is locked to the frequency of the microwave signal (i.e. so that the frequency of the target beat frequency electrical signal is equal to the frequency of the microwave signal), thereby controlling the frequency of the experimental light. The signal control means 7 are adapted to control the microwave signal source, the servo means and the frequency shifting means.
According to the embodiment of the invention, the frequency of the microwave signal is continuously adjusted by using a microwave signal source, so that the frequency of the experimental light is continuously changed under the feedback control of the servo device until the servo device is in a state close to the unlocking state (when the locking function of the servo device fails, the servo device is in the unlocking state), and under the condition that the servo device is in the state close to the unlocking state, the signal control device is configured to adjust the tunable laser by controlling the servo device, so that the frequency of the laser jumps, and further the frequency of the transmission light jumps, and the signal control device controls the frequency shifting device to adjust the frequency of the transmission light which jumps, so that the frequency of the jumps is compensated, and the experimental light with continuous frequency is obtained.
According to the tunable ultra-narrow linewidth laser system based on the optical frequency comb, the laser emitted by the tunable laser passes through the light splitting device to obtain the transmitted light, the transmitted light and the external frequency comb light are adjusted through the adjusting device to obtain the target beat frequency signal, then the signal control device controls the microwave signal source, the servo device and the frequency shifting device to obtain the experimental light with continuously changing frequency according to the frequency information in the target beat frequency signal, and the ultra-narrow linewidth tunable laser with the wide frequency adjusting range and the continuously changing frequency is achieved. In addition, the frequency comb light has a wider frequency spectrum range, and the frequency comb light parameters do not need to be changed in the tuning process, so that tunable lasers with different frequency variation ranges can be simultaneously locked on the same frequency comb light, and the tunable lasers with different frequency variation ranges can realize independent frequency sweeping.
According to an embodiment of the present invention, as shown in fig. 1, the adjusting device 4 includes: a power adjusting unit 41, an adjustable attenuation sheet 42, a beam combining unit 43 and a photo-detection unit 44. The power adjusting unit 41 is adapted to adjust the power of the frequency-comb light to obtain a first power-adjusted frequency-comb light. The adjustable attenuation sheet 42 is adapted to adjust the power sum of the reflected light to obtain a power adjusted reflected light. The beam combining unit 43 is adapted to combine the first power conditioning frequency comb light and the power conditioning reflected light beam. The photodetection unit 44 is adapted to comb the light according to the first power adjustment frequency and adjust the reflected light according to the power, resulting in an initial beat frequency electrical signal comprising a target beat frequency electrical signal.
According to the embodiment of the present invention, the power adjusting unit 41 includes a half-wave plate and a polarization beam splitter sequentially disposed along the optical path, wherein the half-wave plate is used for adjusting the polarization direction of the external frequency comb light; and the polarization beam splitter is used for combining the half-wave plate and adjusting the power of the frequency comb light.
According to the embodiment of the present invention, the beam combining unit 43 may be any device for combining the light beams, for example, the beam combining unit 43 may be a depolarizing beam splitter or a fiber beam splitter.
Fig. 2 schematically shows an optical path diagram of the photodetecting unit.
According to an embodiment of the present invention, a photodetecting unit includes: a light splitting module 441, a fiber collimator 442, an optical fiber 443, and a first photodetector 444. The light splitting module 441 is adapted to split the first power adjustment frequency beam light to obtain a second power adjustment frequency comb light, and the second power adjustment frequency comb light and the power adjustment reflected light generate beat frequency to obtain beat frequency light. The fiber collimator 442 is adapted to couple beat light. The optical fiber 443 is adapted to transmit beat light. The first photodetector 444 is adapted to detect the beat light from the optical fiber, resulting in an initial beat electrical signal comprising the target beat electrical signal. Alternatively, the photodetection unit 44 further includes: an aperture stop (not shown) and a second photodetector. The aperture pair is adapted to filter beat frequency light. And the second photoelectric detector detects the filtered beat frequency light to obtain an initial beat frequency electric signal comprising a target beat frequency electric signal.
Since the frequency comb light of the optical frequency comb has multiple frequencies, the beat light obtained based on the frequency comb light of the optical frequency comb and the laser of the tunable laser also has multiple frequencies, that is, the initial beat electrical signal has multiple frequencies, and a target beat electrical signal can be selected from the initial beat electrical signals according to needs, for example, the target beat electrical signal can be the initial beat electrical signal with the lowest frequency, or can be the beat electrical signal with any other frequency.
When the target beat frequency electric signal is the initial beat frequency electric signal with the lowest frequency, the frequency of the laser is in the middle of the frequencies of the two comb teeth of the frequency comb light, or the frequency of the laser is coincident with the frequency of the frequency comb light, and the servo device is in an unlocking state. The servo device is close to the out-of-lock state only when the frequency of the laser is close to the middle of the frequencies of the two comb teeth of the frequency comb light or the frequency difference between the frequency of the laser and the nearest comb tooth of the frequency comb light is smaller than a preset threshold (for example, the preset threshold may be 0.5MHz or less).
According to an embodiment of the present invention, as shown in fig. 1, the signal control device 7 includes a timing control and voltage output unit 71 and a voltage controlled oscillator 72, or the signal control device 7 includes the timing control and voltage output unit 71.
The timing control and voltage output unit 71, when the servo device 6 is in the state close to losing lock, the timing control and voltage output unit 71 is suitable for synchronizing the frequency of the microwave signal source and the frequency of the target beat frequency electric signal, controlling the servo device 6 and outputting a control instruction to the frequency shift device 3; when the servo device 6 is in the state of losing lock and approaching to losing lock, the frequency of the microwave signal emitted by the microwave source stops changing, and the timing control and voltage output unit 71 outputs a pulse signal to guide the laser to jump over the position which is to approach to losing lock and controls 3 to supplement the jumping frequency. The voltage-controlled oscillator 72 controls the frequency shifter 3 in accordance with the control command for the frequency shifter 3 output from the timing control and voltage output unit, and when the output power of the timing control and voltage output unit 71 is sufficient, the voltage-controlled oscillator 72 may not be used.
Fig. 3 schematically shows a process diagram of the frequency variation in the frequency domain of a tunable laser based on an optical frequency comb. In fig. 3, a0-a5 respectively represent spectral lines of the frequency comb light at different frequencies in the frequency domain, and the frequencies at a0-a5 increase from left to right. b. c and d represent the change process of the frequency of the tunable laser in the frequency domain when the frequency of the target beat frequency electric signal is in different conditions.
According to the embodiment of the present invention, as shown in fig. 3, when the frequency of the tunable laser is locked at the spectral line position a1 of the comb light, the microwave signal source 8 performs a frequency adjustment on the microwave signal, and at this time, there is a frequency of the comb light that is closer to the frequency of the tunable laser in the target beat frequency electrical signal, and the servo system is in the active locking state. At this time, the voltage signal output by the signal control device 7 is zero, and the servo device 6 controls the current of the tunable laser and the voltage of the piezoelectric ceramic on the tunable laser in a feedback manner according to the zero voltage signal input by the signal control device 7, the frequency input by the microwave signal source 8 and the target beat frequency electric signal input by the power divider 53, so that the frequency of the tunable laser moves from the spectral line position a1 of the comb light to the spectral line position a2 of the comb light, thereby realizing the change process b of the frequency of the tunable laser in the frequency domain once, and further controlling the frequency of the experimental light to move correspondingly. When the servo device is not in the near-out-of-lock state, the microwave signal source continuously adjusts the frequency of the microwave signal, so that the frequency of the experimental light is continuously changed under the feedback control of the servo device.
According to the embodiment of the invention, as shown in fig. 3, when the frequency of the tunable laser is locked at the spectral line position a2 of the frequency comb light, the microwave signal source 8 performs a primary adjustment on the frequency of the microwave signal, and at this time, a plurality of frequencies of the frequency comb light close to the frequency of the tunable laser exist in the target beat frequency electrical signal, and the servo system is in a near out-of-lock state. At this time, the signal control device 7 outputs a single pulse voltage signal, and at the same time, synchronizes the time sequence of the microwave signal source to control the microwave signal source to stop changing, the servo device 6 controls the current related to the tunable laser and the voltage of the piezoelectric ceramic in a feedback manner according to the single pulse voltage signal input by the signal control device 7, the frequency input by the microwave signal source 8 and the target beat frequency electrical signal input by the power divider 53, the frequency of the tunable laser jumps from the spectral line position a2 of the frequency comb light to the spectral line position a3 of the frequency comb light, so that the change process c of the frequency of the tunable laser in the frequency domain is realized, at the same time, the signal control device 7 controls the frequency shift device 3 to perform frequency adjustment on the transmitted light in which the jump occurs by controlling the voltage controlled oscillator, so that the frequency of the transmission light with jumping is compensated, and the experimental light with continuously changing frequency is obtained. Wherein the signal control device 7 resets the frequency shift device 3 while controlling the microwave signal source 8, the servo device 6 and the frequency shift device 3 to obtain the experimental light with continuous frequency, so as to prepare for the compensation of the next frequency jump.
According to the embodiment of the present invention, as shown in fig. 3, when the frequency of the tunable laser is locked at the spectral line position a4 of the frequency comb light, the microwave signal source 8 performs a primary adjustment on the frequency of the microwave signal, and at this time, the frequency of the frequency comb light equal to the frequency of the tunable laser exists in the target beat frequency electrical signal, and the servo system is in a near out-of-lock state. At this time, the control process of the tunable laser for jumping the frequency from the spectral line position a4 of the comb light to the spectral line position a5 of the comb light is the same as the control process of the tunable laser for jumping the frequency from the spectral line position a2 of the comb light to the spectral line position a3 of the comb light, the control signal output by the signal control device 7 is the same, and the control signals are all not zero. The process that the frequency of the tunable laser jumps from the spectral line position a4 of the comb light to the spectral line position a5 of the comb light is the change process d of the frequency of the tunable laser in the frequency domain.
According to the embodiment of the present invention, when the servo system is in the near out-of-lock state, the timing control and voltage output unit 71 in the signal control device 7 synchronizes the frequency of the microwave signal source and the frequency of the target beat frequency electrical signal, controls the servo device 6, and outputs a control instruction to the frequency shift device 3, so that the frequency of the experimental light continuously changes when the servo system is in the near out-of-lock state.
According to the embodiment of the invention, the timing control and voltage output unit is an NI board card, an analog card, a signal generator or an arbitrary wave generator.
According to an embodiment of the present invention, the signal processing device 5 includes: a filter 51, a radio frequency amplifier 52, a power divider 53 and a spectrum analyzer 54.
The filter 51 is adapted to filter an initial beat signal comprising a target signal to obtain a target beat signal. The filter 51 is a low-pass filter when the target beat frequency electric signal is the initial beat frequency electric signal having the lowest frequency, and may be a band-pass filter or a combination of a low-pass filter and a high-pass filter when the target beat frequency electric signal is the initial beat frequency electric signal having other frequencies. And a radio frequency amplifier 52 adapted to amplify the power of the target beat frequency electrical signal. A power divider 53 adapted to divide the power-amplified target beat frequency electrical signal into a first reference signal and a second reference signal. And a spectrum analyzer 54 adapted to detect the frequency of the second reference signal to obtain the power of the target beat signal.
According to an embodiment of the invention, the frequency shifting means 3 is an acousto-optic modulator or an electro-optic modulator.
According to an embodiment of the invention, the beam splitting means 2 is a flat glass plate or a second depolarizing beam splitting plate.
According to an embodiment of the present invention, the servo device 6 may control the frequency of the tunable laser by feedback controlling the current associated with the tunable laser and the voltage of the piezoelectric ceramic.
According to the embodiment of the invention, in the tunable ultra-narrow linewidth laser system, the reflecting mirror can be added according to the practical application condition to change the propagation direction of the laser light path.
The optical path and the circuit device in the tunable ultra-narrow linewidth laser system provided by the embodiment of the invention are simple and economical, for example, a frequency shift device with a wide working range, a microwave signal source with a wide working range and the like are not required to be used.
The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are only exemplary embodiments of the present invention and are not intended to limit the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. A tunable ultra-narrow linewidth laser system based on an optical frequency comb, comprising:
a tunable laser (1) adapted to emit laser light;
a light splitting device (2) adapted to split the laser light into transmitted light and reflected light;
the frequency shifting device (3) is suitable for adjusting the frequency of the transmitted light to obtain an experimental light;
the adjusting device (4) is suitable for adjusting the power of frequency comb light from the optical frequency comb and the power of the reflected light, and enabling the adjusted frequency comb light and the adjusted reflected light to generate beat frequency to obtain a target beat frequency electric signal;
the signal processing device (5) is suitable for performing power amplification on the target beat frequency electric signal to obtain a first reference signal, and obtaining the frequency of the target beat frequency electric signal according to the first reference signal;
the microwave signal source (8) is suitable for emitting a microwave signal with adjustable frequency, wherein the difference between the initial frequency of the microwave signal and the frequency of the target beat frequency electric signal is within a preset range;
the servo device (6) is used for controlling the tunable laser in a feedback mode according to the frequency of the microwave signal, so that the frequency of the target beat frequency electric signal is locked on the frequency of the microwave signal, and the frequency of the experimental light is further controlled; and
a signal control device (7) adapted to control said microwave signal source, said servo device and said frequency shifting device;
the frequency of the microwave signal is continuously adjusted by a microwave signal source, so that the frequency of the experimental light is continuously changed under the feedback control of the servo device until the servo device is in a state close to the unlocking state, under the condition that the servo device is in the state close to the unlocking state, the signal control device is configured to adjust the tunable laser by controlling the servo device, so that the frequency of the laser jumps, and further the frequency of the transmission light jumps, and the signal control device controls the frequency shift device to adjust the frequency of the transmission light which jumps, so that the frequency of the transmission light which jumps is compensated, and the experimental light with continuous frequency is obtained.
2. The tunable ultra narrow linewidth laser system of claim 1, wherein the adjusting means (4) comprises:
the power adjusting unit (41) is suitable for adjusting the power of the frequency comb light to obtain first power adjusting frequency comb light;
the adjustable attenuation sheet (42) is suitable for adjusting the power sum of the reflected light to obtain power-adjusted reflected light;
a beam combining unit (43) adapted to combine the first power conditioning frequency comb light and the power conditioning reflected light beam;
and the photoelectric detection unit (44) is suitable for obtaining an initial beat frequency electric signal comprising the target beat frequency electric signal according to the first power adjustment frequency combing light and the power adjustment reflected light.
3. The tunable ultra narrow linewidth laser system of claim 2, wherein the photodetection unit (44) comprises:
and the light splitting module (441) is suitable for splitting the first power adjustment frequency beam light to obtain second power adjustment frequency comb light, and the second power adjustment frequency comb light and the power adjustment reflected light generate beat frequency to obtain beat frequency light.
4. The tunable ultra narrow linewidth laser system of claim 3, wherein the photodetection unit (44) further comprises:
a fiber collimator (442) adapted to couple the beat light;
an optical fiber (443) adapted to transmit the beat light;
a first photodetector (444) adapted to detect the beat light from the optical fiber, resulting in an initial beat electrical signal comprising the target beat electrical signal.
5. The tunable ultra narrow linewidth laser system of claim 3, wherein the photodetection unit (44) further comprises:
an aperture diaphragm adapted to filter the beat light;
and the second photoelectric detector is used for detecting the filtered beat light to obtain an initial beat electrical signal comprising the target beat electrical signal.
6. The tunable ultra narrow linewidth laser system of claim 1, wherein the signal control means (7) comprises:
a timing control and voltage output unit (71), wherein the timing control and voltage output unit (71) is suitable for synchronizing the frequency of the microwave signal source and the frequency of the target beat frequency electric signal, controlling the servo device (6) and outputting a control instruction to the frequency shift device (3) under the condition that the servo device is in the state of close to losing lock;
and the voltage-controlled oscillator (72) controls the frequency shifting device according to the control instruction for the frequency shifting device output by the time sequence control and voltage output unit.
7. The tunable ultra-narrow linewidth laser system of claim 6, wherein the timing control and voltage output unit is an NI board card, an analog card, a signal generator, or an arbitrary wave generator.
8. The tunable ultra narrow linewidth laser system of claim 1, wherein the signal processing means (5) comprises:
a filter (51) adapted to filter an initial beat frequency electrical signal comprising a target beat frequency electrical signal, resulting in the target beat frequency electrical signal;
a radio frequency amplifier (52) adapted to amplify the power of the target beat frequency electrical signal;
a power splitter (53) adapted to split the power amplified target signal into a first reference signal and a second reference signal;
and the spectrum analyzer (54) is suitable for detecting the frequency of the second reference signal so as to obtain the power of the target beat frequency electric signal.
9. The tunable ultra-narrow linewidth laser system of claim 1, wherein the frequency shifting device is an acousto-optic modulator or an electro-optic modulator.
10. The tunable ultra narrow linewidth laser system of claim 1, wherein the beam splitting device (2) is a planar glass plate or a second depolarizing beam splitting plate.
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