CN115963058A - Swept-frequency laser and optical coherence tomography system - Google Patents
Swept-frequency laser and optical coherence tomography system Download PDFInfo
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- CN115963058A CN115963058A CN202111193379.9A CN202111193379A CN115963058A CN 115963058 A CN115963058 A CN 115963058A CN 202111193379 A CN202111193379 A CN 202111193379A CN 115963058 A CN115963058 A CN 115963058A
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Abstract
The application discloses sweep frequency laser and optical coherence tomography imaging system, wherein sweep frequency laser includes: a light beam generating device; the first acousto-optic deflection frequency-selecting component comprises a first acousto-optic deflector, a first ultrasonic generator and a first frequency-selecting reflecting device, wherein the first acousto-optic deflector is used for receiving a first light beam and a first ultrasonic and outputting a second light beam, and the first frequency-selecting reflecting device is used for reflecting a third light beam obtained by frequency selection to the first acousto-optic deflector; and the second sound light deflection frequency selection assembly comprises a second sound light deflector, a second ultrasonic wave generator and a second frequency selection reflection device, the second sound light deflector is used for receiving the third light beam and the second ultrasonic wave and outputting a fourth light beam, and the second frequency selection reflection device is used for reflecting the fifth light beam obtained through frequency selection to the second sound light deflector. The propagation direction of the ultrasonic waves relative to the light beam in the first acousto-optic deflector is opposite to the propagation direction of the ultrasonic waves relative to the light beam in the second acousto-optic deflector.
Description
Technical Field
The application belongs to the technical field of laser, and particularly relates to a frequency-swept laser and an optical coherence tomography system.
Background
Optical Coherence Tomography (OCT) is a novel non-destructive Optical imaging technique. The OCT imaging procedure is generally as follows: firstly, fast wavelength scanning is carried out through a frequency scanning laser, and then intensity detection is carried out on interference signals of the wavelength by matching with a point detector to obtain an interference spectrum; and finally, carrying out Fourier transform on the interference spectrum to obtain microstructure information of the object, and obtaining the chromatographic image of the sample to be detected.
Among them, the swept-frequency laser is used as the light source of OCT, and needs to meet the requirement of faster and more stable frequency selection. Currently, a swept-frequency laser generally adopts a mechanical frequency selection, for example, a rotating polygon mirror to implement the frequency selection. However, mechanical frequency selection has at least the following two problems: on one hand, the speed of a mechanical mode is limited, so that the frequency sweeping speed of the frequency sweeping laser is low; on the other hand, mechanical abrasion inevitably exists in a mechanical mode, so that the sweep frequency stability of the sweep frequency laser is poor.
Disclosure of Invention
The application aims at providing a frequency-swept laser and an optical coherence tomography system, and at least solves the problems that in the prior art, the frequency-swept laser adopts mechanical frequency selection, the frequency-swept speed is low, and the frequency-swept stability is poor.
In order to solve the technical problem, the present application is implemented as follows:
in a first aspect, an embodiment of the present application provides a swept-frequency laser, including:
a beam generating device for generating a first beam;
the first acousto-optic deflection frequency-selecting component comprises a first acousto-optic deflector, a first ultrasonic wave generator and a first frequency-selecting reflecting device, the first ultrasonic wave generator is used for outputting first ultrasonic waves, the first acousto-optic deflector is used for receiving the first light beam and the first ultrasonic waves and outputting a second light beam, the first frequency-selecting reflecting device is used for carrying out frequency selection on the second light beam and reflecting a third light beam obtained through frequency selection to the first acousto-optic deflector;
the second ultrasonic wave generator is used for outputting second ultrasonic waves, the second ultrasonic wave deflector is used for receiving the third light beam and the second ultrasonic waves and outputting a fourth light beam, and the second frequency-selecting reflecting device is used for carrying out frequency selection on the fourth light beam and reflecting a fifth light beam obtained by frequency selection to the second ultrasonic wave deflector;
wherein the light beam generating device is further configured to receive the fifth light beam returned by the second acousto-optic deflector, and the propagation direction of the ultrasonic wave in the first acousto-optic deflector relative to the light beam is opposite to the propagation direction of the ultrasonic wave in the second acousto-optic deflector relative to the light beam.
In a second aspect, an embodiment of the present application provides an optical coherence tomography system, which includes the swept-frequency laser in the first aspect.
In the embodiment of the application, the frequency selection of the sweep laser is realized by the first acousto-optic deflection frequency selection component and the second acousto-optic deflection frequency selection component, wherein the propagation direction of the ultrasonic wave relative to the light beam in the first acousto-optic deflector is opposite to the propagation direction of the ultrasonic wave relative to the light beam in the second acousto-optic deflector. In this way, on the one hand, since the propagation direction of the ultrasonic wave relative to the light beam in the first acousto-optic deflector is opposite to the propagation direction of the ultrasonic wave relative to the light beam in the second acousto-optic deflector, the doppler shifts generated by the two acousto-optic deflectors can be mutually cancelled, and the frequency selection of the swept laser is not adversely affected. On the other hand, the first acousto-optic deflection frequency-selecting component and the second acousto-optic deflection frequency-selecting component are optical devices for realizing frequency selection by adopting an acousto-optic deflection principle, and mechanical motion is not involved in the working process, so that the frequency sweeping laser can have higher scanning frequency and better frequency sweeping stability.
Additional aspects and advantages of the present application will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the present application.
Drawings
The above and/or additional aspects and advantages of the present application will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:
FIG. 1 is a schematic diagram of Doppler shift;
fig. 2 is a schematic structural diagram of a swept-frequency laser provided in an embodiment of the present application;
fig. 3 is a fourier domain mode locking diagram.
Detailed Description
Reference will now be made in detail to the embodiments of the present application, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the drawings are exemplary only for the purpose of explaining the present application and are not to be construed as limiting the present application. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
In the description and claims of this application the expressions first, second, third etc. are used only to distinguish one feature from another, and do not indicate any limitation of the features.
Before describing the technical solutions provided in the embodiments of the present application, in order to facilitate understanding of the embodiments of the present application, the present application first specifically describes problems existing in the prior art.
As previously mentioned, the OCT imaging process is generally as follows: firstly, fast wavelength scanning is carried out through a frequency scanning laser, and then intensity detection is carried out on interference signals of the wavelength by matching with a point detector to obtain an interference spectrum; and finally, carrying out Fourier transform on the interference spectrum to obtain microstructure information of the object, and obtaining a chromatographic image of the sample to be detected.
Among them, the swept-frequency laser is used as the light source of OCT, and needs to meet the requirement of faster and more stable frequency selection. Currently, a swept-frequency laser generally adopts a mechanical frequency selection, for example, a rotating polygon mirror to implement the frequency selection. However, the swept-frequency laser adopting the mechanical frequency selection at least has the problems of low sweep-frequency speed and poor sweep-frequency stability.
In view of the above problems of the prior swept-frequency laser, the inventor focuses on providing a frequency selection method with faster sweep frequency speed and better sweep frequency stability. The inventor specifically studies the following:
the inventor finds that certain limitation exists in the sweep frequency speed and the sweep frequency stability of the sweep frequency laser at present, which is determined by the characteristics of the mechanical frequency selection mode, firstly, the repetition frequency of mechanical motion is low, generally reaches 20kHz as fast as possible, and thus the sweep frequency speed cannot be too fast; secondly, mechanical abrasion exists in the mechanical motion for a long time, and in addition, the mechanical motion is needed in the frequency selection process, so that the stability of the frequency sweep cannot be good.
For the above reasons, the inventor hopes to find a feasible non-mechanical frequency selection way to realize the frequency selection of the swept-frequency laser.
At present, the acousto-optic deflection principle can realize non-mechanical frequency selection, and the acousto-optic deflection principle is also called acousto-optic effect, and the principle is as follows: if ultrasonic waves are generated in an ultrasonic medium such as transparent glass and crystals, periodic refractive index changes are caused to form a phase type diffraction grating, if a laser beam is made to enter the ultrasonic medium, the laser beam is diffracted, and the intensity and direction of diffracted light change with the state of the intensity and frequency of the ultrasonic wave, so that frequency selection is realized.
However, the inventors have found that the beam passes through the acousto-optic deflector with a doppler shift. Fig. 1 shows a schematic diagram of doppler shift, which can be understood as that the frequency of the ultrasonic signal 103 transmitted in the acousto-optic deflector 102 is superimposed on the frequency of the incident light beam 101, so that the frequency of the incident light beam 101 changes (increases or decreases), as shown in fig. 1. When the propagation direction of the incident light beam 101 (e.g., Y1' direction in fig. 1) and the propagation direction of the ultrasonic signal (e.g., Y direction in fig. 1) are "the same direction", the frequency of the incident light beam 101 increases; when the propagation direction of the incident light beam 101 (e.g., the Y2' direction in fig. 1) is "opposite" to the propagation direction of the ultrasonic signal, the frequency of the incident light beam 101 decreases.
Because the acousto-optic deflector has Doppler frequency shift, if the acousto-optic deflector is simply adopted to realize frequency selection of the frequency-swept laser, the line width of laser output by the frequency-swept laser is widened, the coherence length of the laser is shortened, and the scanning range of the laser output by the frequency-swept laser is further narrowed.
In the face of the above-mentioned problems, the inventors have further studied and analyzed to provide a swept-frequency laser provided in the embodiments of the present application. The technical idea of the swept-frequency laser is as follows: the frequency selection is realized by a first acousto-optic deflection frequency selection component and a second acousto-optic deflection frequency selection component, wherein the propagation direction of ultrasonic waves relative to the light beam in the first acousto-optic deflector is opposite to the propagation direction of ultrasonic waves relative to the light beam in the second acousto-optic deflector. In this way, on one hand, since the propagation direction of the ultrasonic wave relative to the light beam in the first acousto-optic deflector is opposite to the propagation direction of the ultrasonic wave relative to the light beam in the second acousto-optic deflector, the doppler shifts generated by the two acousto-optic deflectors can be mutually cancelled, so that the adverse effect of the doppler shift on frequency selection can be eliminated, and the realization of frequency selection by adopting the acousto-optic deflection principle becomes possible. On the other hand, the first acousto-optic deflection frequency-selecting component and the second acousto-optic deflection frequency-selecting component are optical devices for realizing frequency selection by adopting an acousto-optic deflection principle, and mechanical motion is not involved in the working process, so that the frequency sweeping laser can have higher scanning frequency and better frequency sweeping stability.
The swept-frequency laser provided in the embodiments of the present application is described below.
Fig. 2 shows a schematic structural diagram of a swept-frequency laser, and as shown in fig. 2, the swept-frequency laser includes a light beam generating device 21, a first acousto-optic deflection frequency-selecting component 22 and a second acousto-optic deflection frequency-selecting component 23.
The beam generating device 21 may be configured to generate the first beam S1, and the beam generating device 21 may be, for example, an assembly including a laser gain medium and a pump source, and may also be a laser gain chip (SOA).
The first acousto-optic deflection frequency selective assembly 22 may include a first acousto-optic deflector 221, a first ultrasonic generator 222 and a first frequency selective reflective device 223. The first ultrasonic generator 222 is configured to output a first ultrasonic wave Y1, the first acousto-optic deflector 221 is located on a propagation path of the first light beam S1, and is configured to receive the first light beam S1 and the first ultrasonic wave Y1 and output a second light beam S2, and the first frequency-selective reflecting device 223 is located on a propagation path of the second light beam S2, and is configured to frequency-select the second light beam S2 and reflect a third light beam S3 obtained by frequency selection to the first acousto-optic deflector 221. Illustratively, the first Acousto-optic deflector 221 (AOD) may be an Acousto-optic crystal, and the first frequency selective reflecting device 223 may be an Optical grating.
The second sound light deflecting and frequency selecting assembly 23 may include a second sound light deflector 231, a second ultrasonic wave generator 232, and a second frequency selecting and reflecting device 233, the second ultrasonic wave generator 232 is configured to output the second ultrasonic wave Y2, the second sound light deflector 231 is located on a propagation path of the third light beam S3, and is configured to receive the third light beam S3 and the second ultrasonic wave Y2 and output the fourth light beam S4, and the second frequency selecting and reflecting device 233 is located on a propagation path of the fourth light beam S4, and is configured to frequency-select the fourth light beam S4 and reflect the frequency-selected fifth light beam S5 to the second sound deflector 231. Illustratively, the second acoustic-optic deflector 231 may be an acousto-optic crystal and the second frequency selective reflective device 233 may be a grating.
The light beam generating device 21 is also used for receiving the fifth light beam S5 returned by the second acoustic light deflector 231, i.e. the light beam generating device 21 is located on the propagation path of the fifth light beam S5.
The two acousto-optic deflection frequency selection components meet the following conditions: the propagation direction of the ultrasonic waves with respect to the light beam in the first acousto-optic deflector 221 is opposite to the propagation direction of the ultrasonic waves with respect to the light beam in the second acousto-optic deflector 231.
As previously mentioned, when the propagation direction of the light beam is "in the same direction" as the propagation direction of the ultrasonic signal, the frequency of the light beam increases; when the propagation direction of the beam is "opposite" to the propagation direction of the ultrasonic signal, the frequency of the beam decreases. Thus, by making the propagation directions of the ultrasonic waves in the two acousto-optic deflectors opposite to each other with respect to the beam, the frequency of the beam increased in one acousto-optic deflector is the same as the frequency decreased in the other acousto-optic deflector, which enables the frequency changes produced by the two acousto-optic deflectors to cancel each other out, thereby eliminating the Doppler shift as a whole.
Besides the above conditions, the two acousto-optic deflection frequency selecting assemblies can be made to be consistent in other performances, or the first acousto-optic deflection frequency selecting assembly 22 and the second acousto-optic deflection frequency selecting assembly 23 can be made to be symmetrical. Illustratively, the first acousto-optic deflector 221 is symmetrical to the second acousto-optic deflector 231 and has the same performance parameters, the first ultrasonic wave generator 222 is symmetrical to the second ultrasonic wave generator 232 and has the same performance parameters, and the first frequency-selective reflecting device 223 is symmetrical to the second frequency-selective reflecting device 233 and has the same performance parameters.
Illustratively, the first acousto-optic deflector 221 includes a first surface a1, a second surface a2 and a third surface a3, the first surface a1 and the third surface a3 are opposite surfaces, and the first light beam S1 may be incident to the first acousto-optic deflector 221 through the first surface a 1. The first ultrasonic wave generator 222 may be disposed at a side facing the second surface a2, and the first ultrasonic wave Y1 may be transmitted to the first acousto-optic deflector 221 through the second surface a 2. Driven by the first ultrasonic wave Y1, the first beam S1 is diffracted by the first acousto-optic deflector 221 to obtain a diffracted light of the first beam S1, i.e., a second beam S2. The first frequency-selective reflector 223 may be disposed on a side facing the third surface a3, the second light beam S2 is emitted to the first frequency-selective reflector 223 through the third surface a3, the first frequency-selective reflector 223 performs frequency selection on the second light beam S2 to obtain a third light beam S3, and the third light beam S3 is reflected to the first acousto-optic deflector 221 through the third surface a3 and is emitted through the first surface a 1.
The second optical deflector 231 includes a fourth face a4, a fifth face a5, and a sixth face a6, the fourth face a4 and the sixth face a6 are opposite faces, and the third light beam S3 may be incident to the second optical deflector 231 through the fourth face a 4. The second ultrasonic wave generator 232 may be disposed on a side facing the fifth surface a5, and the second ultrasonic wave Y2 may be propagated to the second acoustic light deflector 231 through the fifth surface a 5. The third light beam S3 is diffracted by the second acoustic optical deflector 231 by the second ultrasonic wave Y2 to obtain a fourth light beam S4 which is diffracted light of the third light beam S3. The second frequency-selective reflecting device 233 may be disposed on a side facing the sixth surface a6, the fourth light beam S4 is emitted to the second frequency-selective reflecting device 233 through the sixth surface a6, the second frequency-selective reflecting device 233 performs frequency selection on the fourth light beam S4 to obtain a fifth light beam S5, and the fifth light beam S5 is reflected to the second acoustic optical deflector 231 through the sixth surface a6 and is emitted through the fourth surface a 4.
In some embodiments, the first acousto-optic deflection frequency selective assembly 22 further includes a first collimating beam expander 224 and the second acousto-optic deflection frequency selective assembly 23 further includes a second collimating beam expander 234. The first collimating beam expander 224 is located at the front end of the first acousto-optic deflector 221, and is configured to collimate and expand the first light beam S1 before inputting the first acousto-optic deflector 221; the second collimated beam expander 234 is located at the front end of the second acoustic optical deflector 231, and is configured to collimate and expand the third light beam S3 before being input to the second acoustic optical deflector 231. Illustratively, the first collimating beam expander 224 and the second collimating beam expander 234 are each collimating lenses.
In the embodiment, the front ends of the two acousto-optic deflectors are respectively provided with the corresponding collimating beam expanders, so that light beams to be incident to the acousto-optic deflectors can be converted into parallel light by scattered light, the parallelism is better, more light beams are incident to the acousto-optic deflectors, the quality of the light beams for frequency selection is improved, and the frequency selection effect is improved.
The swept-frequency laser according to the embodiment of the application can also be a swept-frequency laser based on a Fourier Domain Mode Locking (FDML) principle. Fig. 3 shows a diagram of the fourier domain mode locking principle, which generally includes a ring-shaped laser resonator, a gain module (gain medium), a narrow-band optical filter module (optical bandwidth), and a dispersion compensated delay module (dispersion compensated optical delay), as shown in fig. 3.
The following describes a swept-frequency laser based on the fourier domain mode locking principle provided in an embodiment of the present application.
As shown in fig. 2, a swept-frequency laser includes a light beam generating device 21, a coupler 24, a first acousto-optic deflection frequency-selecting component 22, a second acousto-optic deflection frequency-selecting component 23 and a dispersion compensation delay component 25, the light beam generating device 21, the coupler 24, the first acousto-optic deflection frequency-selecting component 22, the second acousto-optic deflection frequency-selecting component 23 and the dispersion compensation delay component 25 are connected by an optical fiber to form a ring-shaped laser resonator 26, wherein the coupler 24 is located on a light beam propagation path from the light beam generating device 21 to the first acousto-optic deflection frequency-selecting component 22, and the dispersion compensation delay component 25 is located on a light beam propagation path from the coupler 24 to the light beam generating device 21. Wherein the coupler 24 may be used for swept output, the dispersion compensating delay element 25 may be used for dispersion compensating and delaying the beam, and the remaining components or elements may be as described above.
Illustratively, when the first acousto-optic deflection frequency-selecting assembly 22 includes the first acousto-optic deflector 221, the first ultrasonic wave generator 222 and the first frequency-selecting reflection device 223, and the second acousto-optic deflection frequency-selecting assembly 23 includes the second acousto-optic deflector 231, the second ultrasonic wave generator 232 and the second frequency-selecting reflection device 233, the light beam generating device 21, the coupler 24, the first acousto-optic deflector 221, the second acousto-optic deflector 231 and the dispersion compensation delay assembly 25 may be connected by optical fibers to form the ring-shaped laser resonator 26.
For another example, when the first acousto-optic deflection frequency-selecting assembly 22 includes the first collimating beam expander 224, the first acousto-optic deflector 221, the first ultrasonic wave generator 222 and the first frequency-selecting reflection device 223, and the second acousto-optic deflection frequency-selecting assembly 23 includes the second collimating beam expander 234, the second acousto-optic deflector 231, the second ultrasonic wave generator 232 and the second frequency-selecting reflection device 233, the beam generating device 21, the coupler 24, the first collimating beam expander 224, the second collimating beam expander 234 and the dispersion compensation delay assembly 25 may be connected by optical fibers to form the ring-shaped laser cavity 26. In addition, the first collimating beam expander 224 may be connected to the first acousto-optic deflector 221 through an optical fiber, and the second collimating beam expander 234 may be connected to the second acousto-optic deflector 231 through an optical fiber.
In this embodiment, the above devices are connected in sequence by optical fibers to form a ring-shaped laser resonator 26, i.e., a swept-frequency laser based on the fourier domain mode-locking principle is formed. The light beam generating device 21 corresponds to a gain module in the fourier domain mode locking principle, the first acousto-optic deflection frequency selecting component 22 and the second acousto-optic deflection frequency selecting component 23 correspond to a narrow-band optical filter module in the fourier domain mode locking principle, and the dispersion compensation delay component 25 corresponds to a dispersion compensation delay module in the fourier domain mode locking principle.
By forming the swept-frequency laser based on the Fourier domain mode locking principle, the performance of the Fourier domain mode-locked laser can be realized, and more times of laser circulation and narrower laser coherence length can be achieved.
In theory, the beam generating device 21 is followed by the coupler 24 in the direction of the ring laser resonator 26, and the order of the remaining components can be flexibly changed as desired.
In some embodiments, as shown in fig. 2, the ring-shaped laser resonator 26 may be formed by connecting optical fibers in order of the beam generating device 21, the coupler 24, the first acousto-optic deflection frequency-selecting component 22, the dispersion compensation delay component 25, and the second acousto-optic deflection frequency-selecting component 23. In this example, a dispersion compensation delay unit 25 is disposed on the light beam propagation path between the first acousto-optic deflection frequency-selective unit 22 and the second acousto-optic deflection frequency-selective unit 23, and is used for performing dispersion compensation and delay on the light beam output from the first acousto-optic deflector 221.
In some embodiments, the dispersion compensating delay assembly 25 includes a first chirped bragg grating 251, a second chirped bragg grating 252, and a polarization maintaining delay fiber 253, wherein the first chirped bragg grating 251 and the second chirped bragg grating 252 are used for sequentially performing dispersion compensation on the optical beam, and the polarization maintaining delay fiber 253 is used for performing polarization maintaining delay on the optical beam to provide the delay required by the fourier domain mode locking principle. Illustratively, the first chirped bragg grating 251 and the second chirped bragg grating 252 are disposed adjacent to each other.
In this embodiment, a set of Chirped Fiber Bragg Gratings (CFBG) is used to provide dispersion compensation, which not only compensates the dispersion of the optical Fiber device in the ring laser resonator 26, but also compensates the dispersion introduced by the reflection of the frequency-selective reflector device by the light with different wavelengths in the deflected beam of the acousto-optic deflector, thereby further achieving better performance of the fourier-domain mode-locked laser.
In some embodiments, the first acousto-optic deflection frequency selective assembly 22 is connected to the ring laser resonator 26 through a first fiber optic circulator 261;
the second sound deflection frequency selecting assembly 23 is connected to the ring-shaped laser resonator 26 through a second fiber circulator 262.
Illustratively, when the first acousto-optic deflection frequency-selective assembly 22 includes the first acousto-optic deflector 221, the first ultrasonic wave generator 222 and the first frequency-selective reflection device 223 and the second acousto-optic deflection frequency-selective assembly 23 includes the second acousto-optic deflector 231, the second ultrasonic wave generator 232 and the second frequency-selective reflection device 233, the first acousto-optic deflector 221 may be connected to the ring-shaped laser resonator 26 through the first fiber circulator 261 and the second acousto-optic deflector 231 may be connected to the ring-shaped laser resonator 26 through the second fiber circulator 262.
For another example, when the first acousto-optic deflection frequency-selective assembly 22 includes a first collimating beam expander 224, a first acousto-optic deflector 221, a first ultrasonic generator 222 and a first frequency-selective reflecting device 223, and the second acousto-optic deflection frequency-selective assembly 23 includes a second collimating beam expander 234, a second acousto-optic deflector 231, a second ultrasonic generator 232 and a second frequency-selective reflecting device 233, the first collimating beam expander 224 may be connected to the ring laser resonator 26 through a first fiber circulator 261, and the second collimating beam expander 234 may be connected to the ring laser resonator 26 through a second fiber circulator 262.
In some embodiments, the first chirped bragg grating 251 is connected to the ring laser cavity 26 via a third fiber circulator 263 and the second chirped bragg grating 252 is connected to the ring laser cavity 26 via a fourth fiber circulator 264.
In the above embodiments, the relevant devices are connected to the ring laser resonant cavity 26 through the optical fiber circulator, so that the light beam can be ensured to be transmitted along the direction of the ring laser resonant cavity 26 all the time, and the light beam transmission effect is improved.
It should be noted that the schematic structural diagram of the swept-frequency laser shown in fig. 2 corresponds to only a specific example of the swept-frequency laser based on the fourier domain mode locking principle, and the swept-frequency laser provided in the embodiment of the present application is not necessarily based on the fourier domain mode locking principle. When the swept-frequency laser is not a swept-frequency laser based on the fourier-domain mode-locking principle, the dispersion compensation delay element 25 and the ring laser resonator 26 shown in fig. 2 may be replaced by other beam propagation elements to achieve beam propagation from the beam generating element 21 to the first acousto-optic deflection frequency-selecting element 22, to the second acousto-optic deflection frequency-selecting element 23, and then to the beam generating element 21.
The embodiment of the present application further provides an optical coherence tomography system, which includes any of the swept-frequency lasers of the above embodiments.
It should be noted that the implementation manner of the embodiment of the swept-frequency laser is also applicable to the embodiment of the optical coherence tomography system, and can achieve the same technical effect, and details are not described herein again.
In the description of the present specification, reference to the description of "one embodiment," "some embodiments," "an illustrative embodiment," "an example," "a specific example," or "some examples" or the like means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present application. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
While embodiments of the present application have been shown and described, it will be understood by those of ordinary skill in the art that: various changes, modifications, substitutions and alterations can be made to the embodiments without departing from the principles and spirit of the application, the scope of which is defined by the claims and their equivalents.
Claims (10)
1. A swept-frequency laser, comprising:
a beam generating device for generating a first beam;
the first acousto-optic deflection frequency-selecting component comprises a first acousto-optic deflector, a first ultrasonic wave generator and a first frequency-selecting reflecting device, wherein the first ultrasonic wave generator is used for outputting first ultrasonic waves, the first acousto-optic deflector is used for receiving the first light beam and the first ultrasonic waves and outputting a second light beam, and the first frequency-selecting reflecting device is used for performing frequency selection on the second light beam and reflecting a third light beam obtained through frequency selection to the first acousto-optic deflector;
a second sound light deflection frequency selection assembly, which comprises a second sound light deflector, a second ultrasonic wave generator and a second frequency selection reflection device, wherein the second ultrasonic wave generator is used for outputting second ultrasonic waves, the second sound light deflector is used for receiving the third light beam and the second ultrasonic waves and outputting a fourth light beam, and the second frequency selection reflection device is used for carrying out frequency selection on the fourth light beam and reflecting a fifth light beam obtained by frequency selection to the second sound light deflector;
wherein the light beam generating device is further configured to receive the fifth light beam returned by the second acousto-optic light deflector, and a propagation direction of the ultrasonic wave in the first acousto-optic light deflector relative to the light beam is opposite to a propagation direction of the ultrasonic wave in the second acousto-optic light deflector relative to the light beam.
2. The swept-frequency laser of claim 1, wherein the first acousto-optic deflection frequency selective component further comprises:
the first collimating beam expander is positioned at the front end of the first acousto-optic deflector and used for collimating and expanding the first light beam and inputting the first light beam to the first acousto-optic deflector;
the second acoustic light deflection frequency selection assembly further includes:
and the second collimation beam expander is positioned at the front end of the second sound optical deflector and used for carrying out collimation and beam expansion on the third light beam and inputting the third light beam to the second sound optical deflector.
3. The swept laser of claim 1, further comprising a coupler and a dispersion compensating delay element, wherein the beam generating device, the coupler, the first acousto-optic deflection frequency selective element, the second acousto-optic deflection frequency selective element and the dispersion compensating delay element are connected by optical fibers to form a ring laser resonator, wherein the coupler is located in a beam propagation path from the beam generating device to the first acousto-optic deflection frequency selective element, and the dispersion compensating delay element is located in a beam propagation path from the coupler to the beam generating device.
4. The swept laser of claim 3, wherein the dispersion compensating delay component is located in a beam propagation path between the first acousto-optic deflection frequency selective component and the second acousto-optic deflection frequency selective component for dispersion compensating and delaying the beam output by the first acousto-optic deflector.
5. The swept-frequency laser of claim 3, wherein the dispersion-compensating delay component comprises a first chirped Bragg grating, a second chirped Bragg grating and a polarization-maintaining delay fiber, wherein the first chirped Bragg grating and the second chirped Bragg grating are used for sequentially performing dispersion compensation on the light beam, and the polarization-maintaining delay fiber is used for performing polarization-maintaining delay on the light beam.
6. The swept-frequency laser of claim 3, wherein the first acousto-optic deflection frequency-selective component is connected to the ring laser resonator through a first fiber optic circulator;
and the second sound light deflection frequency selection component is connected with the annular laser resonant cavity through a second optical fiber circulator.
7. The swept-frequency laser of claim 5, wherein the first chirped Bragg grating is connected to the ring laser cavity through a third fiber circulator and the second chirped Bragg grating is connected to the ring laser cavity through a fourth fiber circulator.
8. The swept-frequency laser of claim 5, wherein the first chirped Bragg grating and the second chirped Bragg grating are disposed adjacent to one another.
9. The swept-frequency laser of claim 1, wherein the first frequency-selective reflecting device is a first grating and the second frequency-selective reflecting device is a second grating.
10. An optical coherence tomography system comprising the swept-frequency laser of any one of claims 1 to 9.
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| CN202111193379.9A CN115963058A (en) | 2021-10-13 | 2021-10-13 | Swept-frequency laser and optical coherence tomography system |
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