CN115706390A - A frequency-modulated external cavity laser device - Google Patents

Abstract

The embodiment of the invention discloses a frequency modulation external cavity laser device, which comprises a seed light source, a feedback loop external cavity, a light source frequency adjusting module, an FP (Fabry-Perot) cavity frequency adjusting module and an external cavity frequency adjusting module, wherein the seed light source is connected with the feedback loop external cavity through a frequency modulation filter; the feedback loop outer cavity comprises an FP cavity; the light source frequency adjusting module is used for adjusting the eigenfrequency of the seed light beam; the FP cavity frequency adjusting module is used for adjusting the resonant frequency of the FP cavity; the external cavity frequency adjusting module is used for adjusting the resonant frequency of the external cavity of the feedback loop; the light source frequency adjusting module, the FP cavity frequency adjusting module and the outer cavity frequency adjusting module are cooperatively modulated, so that the eigen frequency of the seed light beam, the resonance frequency of the FP cavity and the resonance frequency of the outer cavity of the feedback loop meet the outer cavity self-injection locking condition, and the frequency-locked laser is formed. The embodiment of the invention solves the problem of small frequency modulation range of the existing narrow linewidth laser, can greatly improve the frequency modulation range, constructs the external cavity narrow linewidth laser with rapid large-range continuous frequency modulation, and expands the application field of the laser device.

Description

A frequency-modulated external cavity laser device

technical field

Embodiments of the present invention relate to laser technology, and in particular to a frequency-modulated external cavity laser device.

Background technique

The linewidth of the laser is directly related to the quality factor of the laser cavity, and the quality factor of the optical cavity of the semiconductor laser is limited by the material properties and process is usually low. Frequency-tunable single-frequency narrow-linewidth lasers have important applications in lidar, optical frequency domain reflectometer, quantum and other fields. At present, the method of frequency-tunable laser devices to reduce the laser linewidth usually uses the external cavity feedback method, one of which is to use a grating to selectively feed back light of a specific wavelength to return to the laser, and the other is to use an external reflector. At the same time, in order to avoid long light The multi-longitudinal mode effect of the cavity, using an interference filter to select a single longitudinal mode. The above two external cavity lasers can be frequency modulated by rotating gratings or interference filters. However, due to the low quality factor of the external cavity, the obtained laser linewidth is usually on the order of tens to hundreds of kilohertz, and narrower lines cannot be obtained. Width.

At present, although various external cavity laser schemes using high-Q external cavity can achieve ultra-narrow linewidth, their fast frequency modulation range is limited to hundreds of megahertz to gigahertz. In fields such as frequency-modulated continuous wave lidar and optical frequency domain reflectometer, the ranging accuracy is inversely proportional to the frequency modulation range, and in many quantum applications, the use of multiple absorption spectra of atoms also requires ultra-narrow lines with large frequency modulation wide laser. Current laser devices cannot meet the application requirements in these fields.

Contents of the invention

The invention provides a frequency-modulated external cavity laser device to realize a large-scale high-speed continuous frequency-modulated external-cavity laser solution through a high-Q value FP optical cavity, obtain an ultra-narrow line width and obtain a larger range of rapid continuous frequency modulation.

An embodiment of the present invention provides a frequency-modulated external cavity laser device, including a seed light source and a feedback loop external cavity, the feedback loop external cavity includes an FP cavity, and the cavity length of the FP cavity is less than or equal to 10 cm;

The seed light source is used to output a seed beam;

The FP cavity is used to filter the seed beam to form a transmitted beam;

The external cavity of the feedback loop is used to feed back the transmitted light beam to the seed light source to form a feedback optical path;

The frequency-modulated external cavity laser device also includes a light source frequency adjustment module, an FP cavity frequency adjustment module, and an external cavity frequency adjustment module;

The light source frequency adjustment module is used to adjust the eigenfrequency f1 of the seed beam;

The FP cavity frequency adjustment module is used to adjust the resonant frequency f2 of the FP cavity;

The external cavity frequency adjustment module is used to adjust the resonant frequency f3 of the external cavity of the feedback loop;

The frequency adjustment module of the light source, the frequency adjustment module of the FP cavity and the frequency adjustment module of the external cavity are cooperatively modulated so that the eigenfrequency f1 of the seed beam, the resonant frequency f2 of the FP cavity and the feedback loop The resonant frequency f3 of the external cavity satisfies the self-injection locking condition of the external cavity, forming a frequency-locked laser.

Optionally, the external cavity self-injection locking condition includes:

The difference between the eigenfrequency f1 of the seed beam and the resonant frequency f2 of the FP cavity is smaller than the external cavity self-injection locking range of the feedback loop external cavity;

The difference between the resonant frequency f2 of the FP cavity and the resonant frequency f3 of the feedback loop external cavity is less than or equal to half of the free spectral range of the feedback loop external cavity.

Optionally, the frequency adjustment module of the FP cavity and the frequency adjustment module of the external cavity are electronically controlled displacement modules; the electronically controlled displacement module is respectively assembled in at least one optical component of the external cavity of the feedback loop and the FP cavity superior;

The electronically controlled displacement module is used to change the cavity length of the feedback loop external cavity or the FP cavity, or the electrically controlled displacement module is used to change the optical path of the light beam in the optical assembly to adjust the Feedback loop external cavity or resonant frequency of the FP cavity.

Optionally, the feedback loop external cavity and the FP cavity respectively include at least one reflection unit, and the electronically controlled displacement module is assembled on the reflection unit;

The electronically controlled displacement module is used to change the cavity length of the feedback loop external cavity or the FP cavity according to the formula Δf/f=ΔL/L, so as to adjust the resonance frequency of the feedback loop external cavity or the FP cavity ;

Wherein, f is the current resonance frequency of the feedback loop external cavity or the FP cavity, Δf is the change amount of the resonance frequency of the feedback loop external cavity or the FP cavity, and L is the feedback loop external cavity or the FP cavity The current cavity length of the FP cavity, ΔL is the change amount of the cavity length of the external cavity of the feedback loop or the FP cavity.

Optionally, the feedback loop external cavity and the FP cavity respectively include at least one prism unit, and the electronically controlled displacement module is assembled on the prism unit;

The electronically controlled displacement module is used to change the optical path of the light beam in the optical assembly according to the formula Δf/f=n1*ΔL/(n2*L), so as to adjust the feedback loop external cavity or the FP cavity Resonant frequency;

Wherein, f is the current resonance frequency of the feedback loop external cavity or the FP cavity, Δf is the variation of the feedback loop external cavity or the resonance frequency of the FP cavity, and n2*L is the feedback loop external cavity Or the total optical path of the FP cavity, n1*ΔL is the optical path change of the external cavity of the feedback loop or the FP cavity.

Optionally, the FP cavity frequency adjustment module and the external cavity frequency adjustment module are respectively electrically controlled refractive index modules or thermally controlled refractive index modules; the electrically controlled refractive index modules or the thermally controlled refractive index modules are respectively located at The feedback loop external cavity or the FP cavity;

The electrically controlled refractive index module is used to change the refractive index through the electro-optical effect, and the thermally controlled refractive index module is used to change the refractive index through the thermo-optic effect to adjust the light beam in the electrically controlled refractive index module or the thermally controlled The optical path in the refractive index module, thereby adjusting the resonance frequency of the external cavity of the feedback loop or the FP cavity.

Optionally, the seed light source includes a first end and a second end; the seed light beam is output from the first end of the seed light source, and the transmitted light beam is input from the first end of the seed light source;

The feedback loop external cavity also includes a first collimation unit, a one-way transmission unit and a reflection unit;

The first collimation unit is used to collimate the seed beam;

The one-way transmission unit is used to transmit the seed beam to the FP cavity, and prevent the reflected beam of the FP cavity from entering the seed light source;

The reflection unit is used to reflect the transmitted light beam of the FP cavity back to the seed light source to form a feedback light path.

Optionally, the first collimation unit includes a first lens, and the one-way transmission unit includes a polarization beam splitter, a first quarter-wave plate, a second quarter-wave plate, and a second lens in sequence, The reflection unit includes a first reflection mirror;

The FP cavity is located between the first quarter wave plate and the second quarter wave plate; the second lens is located between the FP cavity and the second quarter wave plate between or between the second quarter-wave plate and the first mirror.

Optionally, the seed light source includes a first end and a second end; the seed light beam is output from the first end of the seed light source, and the transmitted light beam is input from the first end of the seed light source; or, the The seed light beam is output from the first end of the seed light source, and the transmitted light beam is input from the second end of the seed light source;

The feedback loop outer cavity also includes a one-way transmission unit and a light steering unit;

The one-way transmission unit is used to transmit the seed beam to the FP cavity, and prevent the reflected beam of the FP cavity from entering the seed light source;

The light turning unit is used to change the transmission direction of the transmitted light beam of the FP cavity, so that the transmitted light beam is fed back to the seed light source to form a feedback light path.

Optionally, the one-way transmission unit includes a circulator, and the light turning unit includes a second reflector, a third reflector, and a fourth reflector;

The beam transmission path in the frequency-modulated external cavity laser device is:

The seed light beam is output from the first end of the seed light source, input from the first end of the circulator, and then output from the second end of the circulator, and enters the FP cavity for transmission, forming the A transmitted light beam; the transmitted light beam is incident on the third end of the circulator after being reflected by the second reflector, the third reflector and the fourth reflector in sequence, and is transmitted from the first end of the circulator The output at one end is fed back to the seed light source.

Optionally, the one-way transmission unit includes an isolator, and the light turning unit includes a fifth reflector, a sixth reflector, a seventh reflector, and an eighth reflector;

The beam transmission path in the frequency-modulated external cavity laser device is:

The seed light beam is output from the first end of the seed light source, input from the first end of the isolator, and then output from the second end of the isolator, and enters the FP cavity for transmission, forming the A transmitted light beam; the transmitted light beam is incident on the second end of the seed light source after being reflected by the fifth reflector, the sixth reflector, the seventh reflector and the eighth reflector in sequence.

Optionally, the one-way transmission unit further includes at least one isolator, and at least one isolator is located between the seed light source and the FP cavity.

Optionally, the FP cavity includes a ninth reflector and a tenth reflector parallel to each other, the seed beam is incident on the ninth reflector and exits from the tenth reflector;

Alternatively, the FP cavity includes an eleventh reflector, a twelfth reflector, and a thirteenth reflector, the seed beam is incident on the eleventh reflector, and passes through the twelfth reflector and the thirteenth reflector in turn. After being reflected by the thirteenth reflector, it emerges from the eleventh reflector.

Optionally, the seed light source includes a semiconductor laser; or, the seed light source includes a combination of a gain chip and an optical filter, and the optical filter is located at any position of the external cavity of the feedback loop.

In the embodiment of the present invention, by setting the seed light source and the external cavity of the feedback loop, and setting a short FP cavity with a cavity length less than or equal to two centimeters in the external cavity of the feedback loop, the seed light source is used to emit the seed beam, and the FP cavity with a high Q value is used Filter the seed beam to form a transmitted beam, and then use the external cavity of the feedback loop to feed the transmitted beam back to the seed light source to form a feedback optical path, realizing an ultra-narrow linewidth frequency-locked laser. In addition, in this embodiment, three frequency adjustment modules are also set up to coordinately modulate the frequencies of the three optical cavities, so as to ensure that the frequencies of the three optical cavities meet the self-injection locking conditions of the external cavity, forming a frequency-locked laser, and realizing a super-wide range High-speed continuous frequency modulation. The embodiment of the present invention solves the problem that the frequency modulation range of the existing narrow-linewidth laser is small, and uses the FP short cavity with high Q value to participate in the frequency locking of the feedback external cavity, and at the same time performs frequency control on the three optical cavities in the frequency modulation external cavity laser device. The coordinated modulation can increase the frequency modulation range to tens to hundreds of GHZ, and build a fast and large-scale continuous frequency modulation external cavity narrow linewidth laser, so that the frequency modulation external cavity laser device can improve the frequency modulation continuous wave laser radar, optical frequency domain reflectometer and other fields. At the same time, for the quantum application field, the frequency-modulated external cavity laser of the present invention can meet the requirements of using multiple absorption spectra of atoms, thereby expanding the application field of the laser device.

Description of drawings

Figure 1 and Figure 2 are simplified structural schematic diagrams of two kinds of frequency-modulated external cavity laser devices provided by the embodiments of the present invention;

Fig. 3 and Fig. 4 are respectively the spectrum diagram of optical cavity in Fig. 1 and Fig. 2;

Fig. 5 is a schematic structural diagram of another frequency-modulated external cavity laser device provided by an embodiment of the present invention;

Fig. 6 is a schematic structural diagram of another frequency-modulated external cavity laser device provided by an embodiment of the present invention;

Fig. 7 and Fig. 8 are structural schematic diagrams of two kinds of frequency-modulated external cavity laser devices provided by the embodiment of the present invention;

Fig. 9 is a schematic structural diagram of another frequency-modulated external cavity laser device provided by an embodiment of the present invention;

Fig. 10 is a schematic structural diagram of another frequency-modulated external cavity laser device provided by an embodiment of the present invention.

Detailed ways

Terms used in the embodiments of the present invention are only for the purpose of describing specific embodiments, and are not intended to limit the present invention. It should be noted that the orientation words such as "up", "down", "left", and "right" described in the embodiments of the present invention are described from the angles shown in the drawings, and should not be interpreted as a reference to the implementation of the present invention. Example limitations. Also in this context, it also needs to be understood that when it is mentioned that an element is formed "on" or "under" another element, it can not only be directly formed "on" or "under" another element, but also can be formed "on" or "under" another element. Formed "on" or "under" another element indirectly through intervening elements. The terms "first", "second", etc. are used for descriptive purposes only, do not indicate any order, quantity or importance, but are used to distinguish different components. Those of ordinary skill in the art can understand the specific meanings of the above terms in the present invention according to specific situations.

As mentioned in the background technology section, various external cavity schemes using high-Q optical cavities have appeared in recent years, which can obtain ultra-narrow linewidth lasers at and below the kilohertz range, such as using high-quality factor whispering gallery optical cavity as a filter construction Composite optical cavity can realize laser with a linewidth of 100 Hz or even Hz level, but its fast tuning range is only a few hundred megahertz using piezoelectric ceramics; or using an on-chip ring cavity, its static thermal frequency tuning range can reach 9 GHz, but the pressure The fast frequency modulation of electric ceramics only has a modulation frequency of 1GHz@12kHz; in addition, there are laser solutions using optical fiber optical cavities or high-Q FP optical cavities, however, their fast frequency modulation range is also small.

In view of this, an embodiment of the present invention provides a frequency modulated external cavity laser device. Figures 1 and 2 are simplified structural schematic diagrams of two kinds of frequency-modulated external cavity laser devices provided by the embodiments of the present invention. Referring to Figures 1 and 2, the frequency-modulated external cavity laser devices include a seed light source 10 and a feedback loop external cavity 30, and the feedback loop The outer cavity 30 includes the FP cavity 20, and the cavity length of the FP cavity 20 is less than or equal to 10 cm. The seed light source 10 is used to output the seed beam; the FP cavity 20 is used to filter the seed beam to form a transmitted beam; the feedback loop external cavity 30 is used to feed back the transmitted beam to the seed light source 10 to form a feedback optical path.

The FM external cavity laser device also includes a light source frequency adjustment module, an external cavity frequency adjustment module and an FP cavity frequency adjustment module (not shown in the figure); the light source frequency adjustment module is used to adjust the eigenfrequency f1 of the seed beam; the external cavity frequency adjustment The module is used to adjust the resonant frequency f3 of the external cavity of the feedback loop; the FP cavity frequency adjustment module is used to adjust the resonant frequency f2 of the FP cavity; the light source frequency adjustment module, the FP cavity frequency adjustment module and the external cavity frequency adjustment module coordinate modulation to make the The intrinsic frequency f1 of the beam, the resonant frequency f2 of the FP cavity and the resonant frequency f3 of the external cavity of the feedback loop satisfy the self-injection locking condition of the external cavity, forming a frequency-locked laser.

Wherein, the seed light source 10 belongs to an optical cavity with gain in essence, and it can select a semiconductor laser for use, which can produce a seed beam with a wider linewidth, or a combination of a gain chip and an optical filter. band) have high gain, and the filter can select the laser wavelength within the gain spectrum range (tens of nm) of the gain chip. The feedback loop external cavity 30 is used to make the seed beam form an external cavity self-injection locking. The feedback loop external cavity 30 is essentially a low-Q optical cavity, which can reduce the laser linewidth to a certain extent. The feedback loop outer cavity 30 may be an optical cavity coaxially returning along the original path, or a feedback loop formed by a steering component, such as a ring feedback loop. However, in the embodiment of the present invention, an FP cavity 20 is provided in the external cavity 30 of the feedback loop. The FP cavity 20 is essentially a high-Q optical cavity, and the laser beam after the feedback is filtered through the FP cavity 20, which can form the external cavity self-injection locking, and at the same time It can narrow the original line width of the laser.

It should be noted that in the present invention, the cavity length of the FP cavity 20 is set to be less than or equal to 10 cm, and its essence is to use a short FP cavity, and use the FP cavity to realize a fast frequency on the premise of using a high Q value to realize an ultra-narrow linewidth laser. , Large-scale frequency modulation. Compared with other solid-state optical cavities, the modulation range can be expanded by using the short FP cavity, and the modulation range can be increased by several orders of magnitude. For example, when a short FP cavity with a cavity length of 2mm is used, the reflectivity of the cavity mirror reaches more than 99.992%, and when the Q value exceeds 10 ⁸ , by changing the cavity length by 2um, the cavity length of the FP cavity can be changed by one-thousandth , the optical cavity frequency can be changed by about 200 GHz around 1550 nm (corresponding to an optical frequency of 200 THz). Compared with high-Q external cavity lasers such as fiber lasers, whispering gallery optical cavities, and on-chip micro-ring cavities, the optical cavity frequency adjustment range of this embodiment can be improved. 1 to 2 orders of magnitude. For another example, when the cavity length of the FP cavity is 2cm, by changing the cavity length of 2μm, that is, changing one ten-thousandth of the cavity length, for frequency adjustment, a large-scale frequency modulation of 20GHz@1550nm can be achieved. Some high-Q external cavity lasers can also greatly increase the frequency modulation range.

The embodiment of the present invention essentially uses three optical cavities to form a composite external cavity laser, and the necessary condition for forming an effective external cavity self-injection locking is that the frequencies of the three optical cavities must be aligned as much as possible. Therefore, it can be understood that in this embodiment In the frequency modulation process of the external cavity laser device, the three optical cavities need to be coordinated to ensure that the frequencies of the three optical cavities always meet the self-injection locking conditions of the external cavity, thereby dynamically forming a frequency-locked laser. Specifically, in the embodiment of the present invention, a light source frequency adjustment module, an FP cavity frequency adjustment module, and an external cavity frequency adjustment module are provided to adjust the frequencies of the three optical cavities synchronously or proportionally to ensure the frequency of the three optical cavities. Alignment, so that the self-injection locking condition of the external cavity can still be satisfied during the dynamic frequency modulation process, forming a frequency-locked laser. Figure 3 and Figure 4 are the spectrum diagrams of the optical cavity in Figure 1 and Figure 2 respectively, as shown in Figure 3 and Figure 4, the vertical black solid line represents the intrinsic frequency f1 of the seed light source; the narrower periodic dotted line represents FP The transmission spectrum of the cavity, the transmission peak frequency close to the intrinsic frequency f1 of the seed light source is the resonant frequency f2 of the FP cavity; the wider Lorentzian solid line represents the transmission spectrum of the external cavity of the feedback loop, which is close to the intrinsic frequency of the seed light source The transmission peak frequency of the characteristic frequency f1 is the resonant frequency f3 of the external cavity of the feedback loop. In order to ensure effective self-injection locking of the three optical cavities, the intrinsic frequency f1 of the seed light source, the transmission peak frequency f2 of the FP cavity, and the transmission peak frequency f3 of the external cavity of the feedback loop need to be aligned as much as possible in the spectrum. When the frequency-modulated external cavity laser device is frequency-modulated, for example, when the resonant frequency of the FP cavity changes, that is, when the narrower periodic dotted line moves left and right, in order to maintain effective self-injection locking, the transmission peak frequency f3 of the feedback loop external cavity and the seed light source The eigenfrequency f1 of the FP cavity must be kept moving synchronously with the transmission peak frequency f2 of the FP cavity, that is, it is necessary to ensure the coordinated modulation of the three optical cavities, so as to avoid loss of self-injection locking and mode hopping.

In addition, it should be noted that the three frequency adjustment modules can use the same control device for frequency modulation control to realize the coordinated modulation of the three optical cavities. Those skilled in the art can design according to the actual situation, and there is no limitation here. In addition, the three frequency adjustment modules can be additional frequency adjustment structures. For example, for the FP cavity, the corresponding frequency adjustment module can be a piezoelectric ceramic PZT, which can be adjusted by changing the length of the FP cavity by using the piezoelectric ceramic PZT. The resonant frequency can also be the frequency adjustment component of the seed light source 10, the feedback loop outer cavity 30 and the FP cavity 20 itself. Taking the seed light source 10 as a DFB distributed feedback laser as an example, it itself has a frequency adjustment component Bragg grating, which can be By changing the current injected into the DFB, the frequency of the output beam of the distributed feedback laser is adjusted by using the Bragg grating.

In the embodiment of the present invention, by setting the seed light source and the external cavity of the feedback loop, and setting a short FP cavity with a cavity length less than or equal to two centimeters in the external cavity of the feedback loop, the seed light source is used to emit the seed beam, and the FP cavity with a high Q value is used Filter the seed beam to form a transmitted beam, and then use the external cavity of the feedback loop to feed the transmitted beam back to the seed light source to form a feedback optical path, realizing an ultra-narrow linewidth frequency-locked laser. In addition, in this embodiment, three frequency adjustment modules are also set up to coordinately modulate the frequencies of the three optical cavities, so as to ensure that the frequencies of the three optical cavities meet the self-injection locking conditions of the external cavity, forming a frequency-locked laser, and realizing a super-wide range High-speed continuous frequency modulation. The embodiment of the present invention solves the problem that the frequency modulation range of the existing narrow-linewidth laser is small, and uses the FP short cavity with high Q value to participate in the frequency locking of the feedback external cavity, and at the same time performs frequency control on the three optical cavities in the frequency modulation external cavity laser device. The coordinated modulation can increase the frequency modulation range to tens to hundreds of GHZ, and build a fast and large-scale continuous frequency modulation external cavity narrow linewidth laser, so that the frequency modulation external cavity laser device can improve the frequency modulation continuous wave laser radar, optical frequency domain reflectometer and other fields. At the same time, for the quantum application field, the frequency-modulated external cavity laser of the present invention can meet the requirements of using multiple absorption spectra of atoms, thereby expanding the application field of the laser device.

Aiming at the specific conditions of the frequency co-modulation of the above three optical cavities, the embodiment of the present invention provides a detailed solution. Continuing to refer to Figures 1-4, further optional external cavity self-injection locking conditions include: the difference between the eigenfrequency f1 of the seed beam and the resonant frequency f2 of the FP cavity is less than the external cavity self-injection locking range of the feedback loop external cavity; the FP cavity The difference between the resonance frequency f2 of the feedback loop external cavity and the resonance frequency f3 of the feedback loop external cavity is less than or equal to half of the free spectral range of the feedback loop external cavity.

Among them, for the resonant frequency f2 of the FP cavity and the resonant frequency f3 of the external cavity of the feedback loop, it can be seen from the frequency spectrum that the difference should not exceed half of the free spectral range FSR3 of the external cavity of the feedback loop. At this time, the resonant frequency f2 is located in the free spectral range FSR3 of the external cavity of the feedback loop, which means that the resonant frequency f2 of the FP cavity can be basically aligned with the resonant frequency f3 of the external cavity of the feedback loop. For the eigenfrequency f1 of the seed beam and the resonant frequency f2 of the FP cavity, taking a conventional distributed feedback laser chip as an example, the self-injection locking range of the external cavity is several hundred megahertz to several gigahertz under appropriate feedback conditions. Hertz, in order to ensure self-injection locking, the difference between the eigenfrequency f1 of the seed beam and the resonant frequency f2 of the FP cavity should be smaller than the above-mentioned external cavity self-injection locking range. At this time, the position of the eigenfrequency f1 of the seed beam on the frequency spectrum is close to the resonant frequency f2. Based on the frequency f1, f2 and f3 in the process of dynamic frequency modulation can be guaranteed to be close to each other or in the range of mutual alignment in the frequency spectrum, therefore, the self-injection locking condition of the external cavity can be satisfied, and a frequency-locked laser can be formed.

On the basis of the above, the embodiment of the present invention also provides a variety of ways to adjust the frequency of the optical cavity. Specifically, optionally, the FP cavity frequency adjustment module and the external cavity frequency adjustment module are electronically controlled displacement modules; the electronically controlled displacement modules are respectively assembled in On at least one optical component of the external cavity of the feedback loop and the FP cavity; the electronically controlled displacement module is used to change the cavity length of the external cavity of the feedback loop or the FP cavity, or the electronically controlled displacement module is used to change the optical path of the light beam in the optical component, To adjust the resonance frequency of the feedback loop external cavity or FP cavity.

In addition, the frequency adjustment module of the FP cavity and the frequency adjustment module of the external cavity can also be selected as an electronically controlled refractive index module or a thermally controlled refractive index module; Middle; the electronically controlled refractive index module is used to change the refractive index through the electro-optical effect, and the thermally controlled refractive index module is used to change the refractive index through the thermo-optic effect to adjust the light beam in the electrically controlled refractive index module or the thermally controlled refractive index module range, thereby adjusting the resonant frequency of the feedback loop external cavity or FP cavity.

Firstly, a detailed example of the above-mentioned scheme for adjusting the frequency of the optical cavity by the electronically controlled displacement module is introduced. Fig. 5 is a schematic structural diagram of another frequency-modulated external cavity laser device provided by an embodiment of the present invention. Referring to Fig. 5, the feedback loop external cavity 30 and the FP cavity 20 respectively include at least one reflection unit, and the electronically controlled displacement module 40 is assembled on the reflection unit Above; the electronically controlled displacement module 40 is used to change the cavity length of the feedback loop external cavity 30 or the FP cavity 20 according to the formula Δf/f=ΔL/L, so as to adjust the resonance frequency of the feedback loop external cavity 30 or the FP cavity 20; wherein, f is the current resonance frequency of the feedback loop external cavity 30 or the FP cavity 20, Δf is the variation of the resonance frequency of the feedback loop external cavity 30 or the FP cavity 20, L is the current cavity length of the feedback loop external cavity 30 or the FP cavity 20, ΔL is the cavity length variation of the feedback loop outer cavity 30 or the FP cavity 20 .

It should be noted that the scheme of adjusting the frequency of the optical cavity by the electronically controlled displacement module can be applied to different composite external cavity laser structures. Taking the composite external cavity laser structure shown in FIG. 5 as an example, in this embodiment, the seed light source 10 includes the first One end 1 and the second end 2; the seed beam is output from the first end 1 of the seed light source 10, and the transmitted light beam is input from the first end 1 of the seed light source 10; the feedback loop external cavity 30 also includes a first collimation unit 31, a single To the transmission unit 32 and the reflection unit 33; the first collimation unit 31 is used to collimate the seed beam; the one-way transmission unit 32 is used to transmit the seed beam to the FP cavity 20, and block the reflected beam of the FP cavity 20 from entering the seed light source 10. The reflection unit 33 is used to reflect the transmitted beam of the FP cavity 20 back to the seed light source 10 to form a feedback optical path.

More specifically, the first collimation unit 31 can be set to include a first lens 311, and the one-way transmission unit 32 includes a polarization beam splitter 321, a first quarter-wave plate 322, a second quarter-wave plate 323 and The second lens 324, the reflection unit 33 includes the first mirror 331; the FP cavity 20 is located between the first quarter wave plate 322 and the second quarter wave plate 323, and the second lens 324 is located between the FP cavity 20 and the second quarter wave plate 323. between the second quarter wave plate 323 .

The FP cavity can be a hollow FP cavity or a solid FP cavity. The hollow FP cavity can be a parallel cavity, a flat concave cavity or a concave-concave cavity. Specifically, the FP cavity 20 may be configured to include a ninth mirror 21 and a tenth mirror 22 parallel to each other. The seed beam is incident on the ninth mirror 21 and emitted from the tenth mirror 22 .

In this frequency-modulated external cavity laser device, the feedback optical path is specifically: the seed light source 10 emits a seed beam, which is collimated by the first lens 311 and passes through the polarization beam splitter 321, and the polarization beam splitter 321 transmits and reflects the P parallel polarization component of the seed beam S vertically polarized component. The P parallel polarization component passes through the first quarter-wave plate 322, transforms it into circularly polarized light, couples out through the FP cavity and is collimated by the second lens 324, and then transforms it into The first linearly polarized light, the first linearly polarized light is perpendicular to the polarization direction of the P parallel polarization component; the first linearly polarized light is reflected by the first mirror 331 and then converted into circularly polarized light by the second quarter-wave plate 323, After passing through the FP cavity, it is converted into the second linearly polarized light by the first quarter-wave plate 322, and the polarization direction of the second linearly polarized light is the same as that of the above-mentioned P parallel polarization component. At this time, the second linearly polarized light can pass through the polarization beam splitter 321 , and finally feed back to the seed light source 10 through the first lens 311 .

It should be noted that in this embodiment, the polarizing beam splitter 321, the first quarter-wave plate 322, the second quarter-wave plate 323 and the second lens 324 essentially form the one-way transmission unit 32, which can be used To block the beam reflected by the FP cavity, and ensure that the beam in the external cavity of the feedback loop returns coaxially to the original path. Specifically, it can be understood that when the circularly polarized light transformed by the first quarter-wave plate 322 passes through the FP cavity 20, it will form reflected light toward the seed light source 10 on the reflective structure in the FP cavity 20, if the reflected Light directly entering the seed light source 10 will affect the self-injection locking of the entire external cavity. In the structure of this embodiment, by setting the first quarter-wave plate 322 and the polarizing beam splitter 321, the reflected light will form a third linearly polarized light after passing through the first quarter-wave plate 322, and the third linearly polarized light and The polarization direction of the above-mentioned P parallel polarization component is vertical. At this time, the third linearly polarized light will be reflected when passing through the polarization beam splitter 321, but cannot be transmitted through the polarization beam splitter 321, thereby effectively blocking the reflected light feedback formed by the FP cavity to the seed light source.

In this embodiment, the electronically controlled displacement module 40 corresponding to the feedback loop outer cavity 30 is the first electrically controlled displacement module 41, as shown in the figure, it can be installed on the back of the reflecting unit 33, that is, the first reflecting mirror 331, and of course It can be installed on the side or front of the first reflector 331 . The electronically controlled displacement module 40 may specifically be a piezoelectric ceramic PZT or a voice coil motor or the like. Those skilled in the art can understand that under the control of electrical signals, the piezoelectric ceramic PZT or the voice coil motor can accurately move the position of the reflection unit 33, thereby adjusting the cavity length of the feedback loop external cavity 30, in other words, it can be achieved through the first The electronically controlled displacement module 41 changes the cavity length to adjust the resonant frequency f3 of the external cavity 30 of the feedback loop. Similarly, for the FP cavity 20 , the corresponding electronically controlled displacement module 40 is the second electronically controlled displacement module 42 , which may also be a piezoelectric ceramic PZT or a voice coil motor. As shown in the figure, the second electronically controlled displacement module 42 can be arranged on the back of the tenth reflector 22, or can be installed on the side or front of the tenth reflector 22, etc., and can also be precisely moved by piezoelectric ceramic PZT or voice coil motor The position of the tenth mirror 22 can adjust the resonant frequency f2 of the FP cavity 20 .

In this embodiment, the electronically controlled displacement module 40 is mainly responsible for moving the position of a certain component of the optical cavity, thereby adjusting the cavity length of the optical cavity, and changing the frequency of the optical cavity by using the cavity length. Therefore, when adjusting the length of the optical cavity, it is necessary to ensure the coordinated modulation of the frequency of the three optical cavities. Specifically, the ratio of the change in cavity length to the current cavity length is equal to the ratio of the change in frequency to the current frequency to change the external cavity of the feedback loop. 30 or the cavity length of the FP cavity 20 guides the adjustment of the resonant frequency of the external cavity 30 or the FP cavity 20 of the feedback loop.

Fig. 6 is a schematic structural diagram of another frequency-modulated external cavity laser device provided by an embodiment of the present invention. Compared with Fig. 5 and Fig. 6, the second lens 324 in the optional one-way transmission unit 32 is located on the second quarter-wave plate 323 and between the first mirror 331. Wherein, the frequency-modulated external cavity laser device shown in FIG. 6 is essentially a modification of FIG. 5. In the structure of the laser device shown in FIG. 331, thereby reducing the accuracy and difficulty of angular alignment of the first mirror 331.

Embodiments of the present invention also provide other composite external cavity laser structures for the solution of adjusting the frequency of the optical cavity by the electronically controlled displacement module. Figures 7 and 8 are structural schematic diagrams of two other frequency-modulated external cavity laser devices provided by the embodiments of the present invention. Referring to Figures 7 and 8, in these two embodiments, the seed light source 10 includes a first end 1 and a second end 2; the seed light beam is output from the first end 1 of the seed light source 10, and the transmitted light beam is input from the first end 1 of the seed light source 10; or, the seed light beam is output from the first end 1 of the seed light source 10, and the transmitted light beam is input from the first end 1 of the seed light source 10 The second end 2 is input; the feedback loop external cavity 30 also includes a one-way transmission unit 32 and a light turning unit 35; the one-way transmission unit 32 is used to transmit the seed beam to the FP cavity 20, and block the reflected beam of the FP cavity 20 from entering the The seed light source 10 ; the light turning unit 35 is used to change the transmission direction of the transmitted light beam of the FP cavity 20 , so that the transmitted light beam is fed back to the seed light source 10 to form a feedback light path.

Specifically, referring to FIG. 7 , in this embodiment, the seed light beam is output from the first end 1 of the seed light source 10 , and the transmitted light beam is input from the first end 1 of the seed light source 10 . The one-way transmission unit 32 includes a circulator 325 , and the light turning unit 35 includes a second reflector 351 , a third reflector 352 and a fourth reflector 353 . The beam transmission path in the frequency-modulated external cavity laser device is: the seed beam is output from the first end 1 of the seed light source 10, input by the first end 1 of the circulator 325, output by the second end 2 of the circulator 325, and incident to The FP cavity 20 transmits to form a transmitted light beam; the transmitted light beam is incident on the third end 3 of the circulator 325 after being reflected by the second reflector 351, the third reflector 352 and the fourth reflector 353 in sequence, and is transmitted from the circulator 325 The output of the first terminal 1 is fed back to the seed light source 10 .

Referring to FIG. 8 , in this embodiment, the seed light beam is output from the first end 1 of the seed light source 10 , and the transmitted light beam is input from the second end 2 of the seed light source 10 . The one-way transmission unit 32 includes an isolator 326 , and the light turning unit 35 includes a fifth reflector 354 , a sixth reflector 355 , a seventh reflector 356 and an eighth reflector 357 . The beam transmission path in the FM external cavity laser device is: the seed beam is output from the first end 1 of the seed light source 10, input by the first end 1 of the isolator 326, output by the second end 2 of the isolator, and incident on the FP The cavity transmits to form a transmitted beam; the transmitted beam is reflected by the fifth reflector 354 , sixth reflector 355 , seventh reflector 356 and eighth reflector 357 in sequence, and then enters the second end 2 of the seed light source 10 .

In the two embodiments shown in Fig. 7 and Fig. 8, the first electronically controlled displacement module 41 corresponding to the external chamber 30 of the feedback loop can be installed on the back of any reflector in the light turning unit 35, by adjusting the position, the cavity length of the external cavity 30 of the feedback loop can be changed, thereby adjusting the frequency of the optical cavity. For the FP cavity 20, the second electronically controlled displacement module 42 can be arranged on the back of the tenth reflector 22, and the position of the tenth reflector 22 can be precisely moved by a piezoelectric ceramic PZT or a voice coil motor, which can adjust the resonant frequency of the FP cavity 20 f2 to adjust.

In addition, for the composite external cavity laser structure provided in the four embodiments shown in Figures 5 to 8, those skilled in the art can optionally add at least one isolator to the above-mentioned one-way transmission unit, and the isolator is located between the seed light source and the FP cavity between. At this time, the isolator can further block the reflected light of the FP cavity, effectively reducing the influence of the direct reflected light of the FP cavity on the frequency locking of the entire external cavity.

FIG. 9 is a schematic structural diagram of another frequency-modulated external cavity laser device provided by an embodiment of the present invention. Referring to FIG. 9 , this embodiment provides another implementation mode for the structure of an FP cavity. As shown in FIG. 9, the FP cavity 20 may include an eleventh reflector 23, a twelfth reflector 24, and a thirteenth reflector 25. The seed beam is incident on the eleventh reflector 23, and passes through the twelfth reflector in turn. 24 and the thirteenth reflector 25, and then emerge from the eleventh reflector 23.

In this embodiment, the FP cavity 20 is essentially a ring-shaped FP cavity composed of three highly reflective mirrors, and the cavity length modulation of the ring-shaped FP cavity is realized by piezoelectric ceramic PZT on one cavity mirror. The seed beam is reflected and coupled into the ring-shaped FP cavity 20 through a reflector provided in the external cavity of the feedback loop. After passing through the eleventh reflector 23, the seed beam passes through the twelfth reflector 24, the eleventh reflector 23, The reflections of the thirteenth reflector 25 , the eleventh reflector 23 , and the twelfth reflector 24 are emitted by the eleventh reflector 23 to form a transmitted light beam, which returns to the seed light source 10 along the original path. The cavity length of the external cavity of the feedback loop is realized by arranging piezoelectric ceramic PZT on the reflector therein, which will not be repeated here.

In the frequency-modulated external-cavity laser devices of the above-mentioned embodiments, in addition to deforming the external cavity of the feedback loop and the FP cavity, the seed light source can also be implemented in different ways. Taking the embodiment shown in Figures 5-9 as an example, the optional seed light source 10 is a semiconductor laser 11; or, the seed light source 10 can also be set to include a combination of a gain chip 12 and an optical filter 13, and the optical filter 13 can be arranged at Any position of the external cavity 30 of the feedback loop.

In addition, those skilled in the art can understand that the frequency-locked laser light of the above-mentioned frequency-modulated external cavity laser devices has different light output methods, as shown in Figures 5 and 6, the frequency-locked laser light can be reflected upward by the polarization beam splitter 321, as shown in Figure 9 As with the laser device shown in FIG. 10 , the frequency-locked laser can be output from the ring FP cavity 20 . As for the laser device shown in FIG. 7 , a beam splitter can be optionally provided on the optical path between the third reflector 352 and the fourth reflector 353 , and the frequency-locked laser can be output by using the beam splitter. Similarly, for the laser device shown in FIG. 8 , a beam splitter can be optionally provided on the optical path between the sixth reflector 355 and the seventh reflector 356 , and the frequency-locked laser can be output through the beam splitter.

In other embodiments of the present invention, the electronically controlled displacement module can also be used to adjust the frequency of the optical cavity with different principles. FIG. 10 is a schematic structural diagram of another frequency-modulated external cavity laser device provided by an embodiment of the present invention. Referring to FIG. 10, in this embodiment, the feedback loop external cavity 30 and/or the FP cavity 20 respectively include at least one prism unit 50, and The displacement control module 40 is assembled on the prism unit 50; the electronic displacement module 40 is used to change the optical path of the light beam in the optical assembly according to the formula Δf/f=n1*ΔL/(n2*L), so as to adjust the external cavity of the feedback loop 30 or the resonant frequency of the FP cavity 20. At this time, f is the current resonant frequency of the feedback loop external cavity or FP cavity, Δf is the variation of the resonance frequency of the feedback loop external cavity or FP cavity, n2*L is the total optical path length of the feedback loop external cavity or FP cavity, n1 *ΔL is the optical path change of the feedback loop external cavity or FP cavity.

Among them, the prism unit 50 is set in the feedback loop external cavity 30 and/or the FP cavity 20, so that the seed beam has a part of the optical path in the prism unit 50, and since the prism unit 50 has a certain refractive index n1, through the piezoelectric ceramic PZT or The electronically controlled displacement module 40 such as a voice coil motor can adjust the position of the prism unit 50 , conversely, can adjust the relative position of the beam in the prism unit 50 , thereby changing the optical path of the beam in the prism unit 50 . Wherein, the optical path in the prism unit 50 can be represented by n1*L. When the prism unit 50 moves along the direction perpendicular to the light beam, the light path L and the optical path n1*L in the prism unit 50 can be changed. In this embodiment, the cavity length of the feedback loop external cavity 30 or FP cavity 20 can also be changed according to the ratio of the optical path variation to the current optical path equal to the ratio of the frequency variation to the current frequency to guide and adjust the feedback loop external cavity 30 or the resonant frequency of the FP cavity 20 . The electronically controlled displacement module 40 can be installed on the side of the prism unit 50 as shown in the figure, and those skilled in the art can also install it at any other position according to the actual design, and there is no limitation here.

It should be noted that the structure of the FP cavity and the feedback loop external cavity shown in Figure 10 is only one of the implementation methods, and those skilled in the art can refer to the composite external cavity structure shown in Figures 5-9 for the FP The cavity and the external cavity of the feedback loop are reasonably deformed, which will not be repeated here. It should also be noted that since the optical path of the optical cavity has a linear relationship with the phase (θ=2πL/λ), the use of the optical path as an adjustment factor in the above-mentioned embodiments is only an expression, and those skilled in the art can understand , the phase of the optical cavity can also be adjusted through the above-mentioned prism unit and the electronically controlled displacement module. Therefore, on the basis of the above-mentioned embodiments, those skilled in the art design to adjust the frequency of the optical cavity by changing the phase, which is essentially the same as adjusting the frequency of the optical cavity by changing the optical path in the embodiment of the present invention, which belongs to the above-mentioned embodiment Reasonable deformation on the basis, thus will not depart from the protection scope of the present invention.

For the scheme of adjusting the frequency of the optical cavity by the electronically controlled refractive index module or the thermally controlled refractive index module provided by the embodiment of the present invention, based on the above-mentioned scheme of the prism unit and the electrically controlled displacement module, those skilled in the art can understand that the optical path of the optical cavity changes Not only depends on the path L of the light beam in the optical component, but also depends on the refractive index n of this optical component. Based on this, in the embodiments of the present invention, the electro-optical effect or thermo-optic effect can be used to set corresponding electronically controlled refractive index modules and thermally controlled refractive index modules in the external cavity of the feedback loop or the FP cavity respectively. The refractive index control module changes the optical path by changing the refractive index, thereby adjusting the resonance frequency of the external cavity of the feedback loop and the FP cavity. It can be understood that the composite external cavity structure provided in the above embodiments is also applicable to the scheme of adjusting the frequency of the optical cavity by an electronically controlled refractive index module or a thermally controlled refractive index module, and those skilled in the art can design according to the actual situation. No more examples here.

Note that the above are only preferred embodiments of the present invention and applied technical principles. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described here, and various obvious changes, readjustments, mutual combinations and substitutions can be made by those skilled in the art without departing from the protection scope of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and can also include more other equivalent embodiments without departing from the concept of the present invention, and the present invention The scope is determined by the scope of the appended claims.

Claims (14)

1. A frequency-modulated external cavity laser device, characterized in that it comprises a seed light source and a feedback loop external cavity, the feedback loop external cavity comprises a FP cavity, and the cavity length of the FP cavity is less than or equal to 10cm; The seed light source is used to output a seed beam; The FP cavity is used to filter the seed beam to form a transmitted beam; The external cavity of the feedback loop is used to feed back the transmitted light beam to the seed light source to form a feedback optical path; The frequency-modulated external cavity laser device also includes a light source frequency adjustment module, an FP cavity frequency adjustment module, and an external cavity frequency adjustment module; The light source frequency adjustment module is used to adjust the eigenfrequency f1 of the seed beam; The FP cavity frequency adjustment module is used to adjust the resonant frequency f2 of the FP cavity; The external cavity frequency adjustment module is used to adjust the resonant frequency f3 of the external cavity of the feedback loop; The frequency adjustment module of the light source, the frequency adjustment module of the FP cavity and the frequency adjustment module of the external cavity are cooperatively modulated so that the eigenfrequency f1 of the seed beam, the resonant frequency f2 of the FP cavity and the feedback loop The resonant frequency f3 of the external cavity satisfies the self-injection locking condition of the external cavity, forming a frequency-locked laser. 2. The frequency-modulated external cavity laser device according to claim 1, wherein the external cavity self-injection locking condition comprises: The difference between the eigenfrequency f1 of the seed beam and the resonant frequency f2 of the FP cavity is smaller than the external cavity self-injection locking range of the feedback loop external cavity; The difference between the resonant frequency f2 of the FP cavity and the resonant frequency f3 of the feedback loop external cavity is less than or equal to half of the free spectral range of the feedback loop external cavity. 3. The frequency-modulated external cavity laser device according to claim 1, characterized in that, The frequency adjustment module of the FP cavity and the frequency adjustment module of the external cavity are electronically controlled displacement modules; the electrically controlled displacement modules are respectively assembled on at least one optical component of the feedback loop external cavity and the FP cavity; The electronically controlled displacement module is used to change the cavity length of the feedback loop external cavity or the FP cavity, or the electrically controlled displacement module is used to change the optical path of the light beam in the optical assembly to adjust the Feedback loop external cavity or resonant frequency of the FP cavity. 4. The frequency-modulated external cavity laser device according to claim 3, characterized in that, The feedback loop external cavity and the FP cavity respectively include at least one reflection unit, and the electronically controlled displacement module is assembled on the reflection unit; The electronically controlled displacement module is used to change the cavity length of the feedback loop external cavity or the FP cavity according to the formula Δf/f=ΔL/L, so as to adjust the resonance frequency of the feedback loop external cavity or the FP cavity ; Wherein, f is the current resonance frequency of the feedback loop external cavity or the FP cavity, Δf is the change amount of the resonance frequency of the feedback loop external cavity or the FP cavity, and L is the feedback loop external cavity or the FP cavity The current cavity length of the FP cavity, ΔL is the change amount of the cavity length of the external cavity of the feedback loop or the FP cavity. 5. The frequency-modulated external cavity laser device according to claim 3, characterized in that, The feedback loop external cavity and the FP cavity respectively include at least one prism unit, and the electronically controlled displacement module is assembled on the prism unit; The electronically controlled displacement module is used to change the optical path of the light beam in the optical assembly according to the formula Δf/f=n1*ΔL/(n2*L), so as to adjust the feedback loop external cavity or the FP cavity Resonant frequency; Wherein, f is the current resonance frequency of the feedback loop external cavity or the FP cavity, Δf is the variation of the feedback loop external cavity or the resonance frequency of the FP cavity, and n2*L is the feedback loop external cavity Or the total optical path of the FP cavity, n1*ΔL is the optical path change of the external cavity of the feedback loop or the FP cavity. 6. The frequency-modulated external cavity laser device according to claim 1, characterized in that, The FP cavity frequency adjustment module and the external cavity frequency adjustment module are respectively electrically controlled refractive index modules or thermally controlled refractive index modules; the electrically controlled refractive index modules or the thermally controlled refractive index modules are respectively located in the feedback loop the outer cavity or the FP cavity; The electrically controlled refractive index module is used to change the refractive index through the electro-optical effect, and the thermally controlled refractive index module is used to change the refractive index through the thermo-optic effect to adjust the light beam in the electrically controlled refractive index module or the thermally controlled The optical path in the refractive index module, thereby adjusting the resonance frequency of the external cavity of the feedback loop or the FP cavity. 7. The frequency-modulated external cavity laser device according to claim 1, characterized in that, The seed light source includes a first end and a second end; the seed light beam is output from the first end of the seed light source, and the transmitted light beam is input from the first end of the seed light source; The feedback loop external cavity also includes a first collimation unit, a one-way transmission unit and a reflection unit; The first collimation unit is used to collimate the seed beam; The one-way transmission unit is used to transmit the seed beam to the FP cavity, and prevent the reflected beam of the FP cavity from entering the seed light source; The reflection unit is used to reflect the transmitted light beam of the FP cavity back to the seed light source to form a feedback light path. 8. The frequency-modulated external cavity laser device according to claim 7, characterized in that, The first collimation unit includes a first lens, the one-way transmission unit includes a polarization beam splitter, a first quarter-wave plate, a second quarter-wave plate, and a second lens in turn, and the reflection unit including a first reflector; The FP cavity is located between the first quarter wave plate and the second quarter wave plate; the second lens is located between the FP cavity and the second quarter wave plate between or between the second quarter-wave plate and the first mirror. 9. The frequency-modulated external cavity laser device according to claim 1, wherein: The seed light source includes a first end and a second end; the seed light beam is output from the first end of the seed light source, and the transmitted light beam is input from the first end of the seed light source; or, the seed light beam is output from the first end of the seed light source The first end of the seed light source is output, and the transmitted light beam is input from the second end of the seed light source; The feedback loop outer cavity also includes a one-way transmission unit and a light steering unit; The one-way transmission unit is used to transmit the seed beam to the FP cavity, and prevent the reflected beam of the FP cavity from entering the seed light source; The light turning unit is used to change the transmission direction of the transmitted light beam of the FP cavity, so that the transmitted light beam is fed back to the seed light source to form a feedback light path. 10. The frequency modulated external cavity laser device according to claim 9, characterized in that, The one-way transmission unit includes a circulator, and the light turning unit includes a second reflector, a third reflector and a fourth reflector; The beam transmission path in the frequency-modulated external cavity laser device is: The seed light beam is output from the first end of the seed light source, input from the first end of the circulator, and then output from the second end of the circulator, and enters the FP cavity for transmission, forming the A transmitted light beam; the transmitted light beam is incident on the third end of the circulator after being reflected by the second reflector, the third reflector and the fourth reflector in sequence, and is transmitted from the first end of the circulator The output at one end is fed back to the seed light source. 11. The frequency-modulated external cavity laser device according to claim 9, characterized in that, The one-way transmission unit includes an isolator, and the light turning unit includes a fifth reflector, a sixth reflector, a seventh reflector, and an eighth reflector; The beam transmission path in the frequency-modulated external cavity laser device is: The seed light beam is output from the first end of the seed light source, input from the first end of the isolator, and then output from the second end of the isolator, and enters the FP cavity for transmission, forming the A transmitted light beam; the transmitted light beam is incident on the second end of the seed light source after being reflected by the fifth reflector, the sixth reflector, the seventh reflector and the eighth reflector in sequence. 12. The frequency-modulated external cavity laser device according to any one of claims 7-11, characterized in that, The one-way transmission unit further includes at least one isolator, and at least one isolator is located between the seed light source and the FP cavity. 13. The frequency modulated external cavity laser device according to claim 1, characterized in that, The FP cavity includes a ninth reflector and a tenth reflector parallel to each other, the seed beam is incident on the ninth reflector and exits from the tenth reflector; Alternatively, the FP cavity includes an eleventh reflector, a twelfth reflector, and a thirteenth reflector, the seed beam is incident on the eleventh reflector, and passes through the twelfth reflector and the thirteenth reflector in turn. After being reflected by the thirteenth reflector, it emerges from the eleventh reflector. 14. The frequency modulated external cavity laser device according to claim 1, characterized in that, The seed light source includes a semiconductor laser; or, the seed light source includes a combination of a gain chip and an optical filter, and the optical filter is located at any position of the external cavity of the feedback loop.

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