CN215989629U - Narrow linewidth external cavity laser device based on semi-confocal cavity - Google Patents
Narrow linewidth external cavity laser device based on semi-confocal cavity Download PDFInfo
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- CN215989629U CN215989629U CN202122433720.5U CN202122433720U CN215989629U CN 215989629 U CN215989629 U CN 215989629U CN 202122433720 U CN202122433720 U CN 202122433720U CN 215989629 U CN215989629 U CN 215989629U
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Abstract
The embodiment of the utility model discloses a narrow linewidth external cavity laser device based on a semi-confocal cavity. The laser device includes: a seed light source for outputting a seed light beam; the semi-confocal cavity is used for reflecting the seed light beam internally and then feeding back the seed light beam to the seed light source to form a feedback light path, and the semi-confocal cavity meets the external cavity self-injection locking condition to form frequency-locked laser; the semi-confocal cavity comprises a reflecting plane and a reflecting spherical surface which are opposite to each other, the reflecting spherical surface is convex towards one side departing from the reflecting plane, and the reflecting plane is positioned on the focal plane of the reflecting spherical surface; the reflecting plane is inclined relative to the light path of the seed light beam, the focus of the reflecting spherical surface on the reflecting plane is positioned on the light path of the seed light beam, and the seed light beam is emitted from the original light path after being circularly reflected for multiple times between the reflecting plane and the reflecting spherical surface. The utility model solves the problem of larger volume of the existing narrow linewidth laser device, realizes narrow linewidth frequency-locked laser, simultaneously enables the volume of the feedback external cavity to be smaller, and is beneficial to the miniaturization of the laser device.
Description
Technical Field
The embodiment of the utility model relates to the technical field of laser, in particular to a narrow linewidth external cavity laser device based on a semi-confocal cavity.
Background
The laser is a device capable of emitting laser, the light emitted by the laser is pure in quality and stable in spectrum, and compared with a common light source, the laser has superior coherence and monochromaticity and is widely applied to different fields of national defense, communication, buildings and the like. In order to meet intercity and space laser coherent communication with further improved performance in the future, the requirements of artificial intelligent environment sensing-oriented frequency modulation continuous wave laser radar, space gravitation detection, atomic molecule measurement and the like are met, and higher requirements are provided for the line width, the volume power consumption, the production cost and the like of the laser.
The laser comprises an excitation source, a gain medium and a resonant cavity, wherein the excitation source provides energy in the laser generation process, the light amplification process is realized in the gain medium, photons move in random directions after being generated in the gain medium, and if the photons are not limited, only common light beams can be obtained, so that the resonant cavity is required to be added to control the light beams to obtain different laser outputs so as to meet different applications.
An important parameter of the laser is the line width, the line width of the laser is mainly affected by external factors such as spontaneous radiation of excited atoms or ions of the laser, phase noise, mechanical vibration of a resonant cavity, temperature jitter and the like, and the smaller the line width value is, the higher the purity of the spectrum is, namely, the better the monochromaticity of the laser is, the stronger the coherence is, and the extremely long coherence length is represented.
Currently, narrow linewidth lasers include solid state narrow linewidth lasers, fiber narrow linewidth lasers, and semiconductor narrow linewidth lasers. The line width of the solid or optical fiber narrow line width laser can reach 1-kHz level, but the solid or optical fiber narrow line width laser has large volume, limited covering wavelength, high production cost and unsmooth performance. The semiconductor laser can be produced in batches at low cost, has small volume and low power consumption, covers light in a wavelength range, and is widely favored. However, the eigenfrequency of semiconductor lasers is very noisy and the best distributed feedback lasers are also on the order of hundreds of kHz.
SUMMERY OF THE UTILITY MODEL
The utility model provides a narrow linewidth external cavity laser device based on a semi-confocal cavity, which is used for reducing the volume of a resonant cavity and reducing the size of external cavity laser on the premise of meeting the requirement of narrow linewidth.
The embodiment of the utility model provides a narrow linewidth external cavity laser device based on a semi-confocal cavity, which comprises:
a seed light source for outputting a seed light beam;
the semi-confocal cavity is used for reflecting the seed light beam internally and feeding back the seed light beam to the seed light source to form a feedback light path, and the semi-confocal cavity meets the external cavity self-injection locking condition to form frequency-locked laser;
the semi-confocal cavity comprises a reflecting plane and a reflecting spherical surface, the reflecting spherical surface is convex towards one side deviating from the reflecting plane, and the reflecting plane is positioned on the focal plane of the reflecting spherical surface;
the reflecting plane is inclined relative to the light path of the seed light beam, the focus of the reflecting spherical surface on the reflecting plane is located on the light path of the seed light beam, and the seed light beam is emitted from the original light path after being circularly reflected for multiple times between the reflecting plane and the reflecting spherical surface.
Optionally, the semi-confocal cavity comprises a plano-convex lens, and the plano-convex lens comprises the reflecting plane and the reflecting spherical surface.
Optionally, the semi-confocal cavity comprises a plane mirror and a spherical mirror, the plane mirror comprises the reflecting plane, and the spherical mirror comprises the reflecting spherical surface.
Optionally, on the light path of the seed light beam, the reflective spherical surface is located on a side of the reflective plane away from the seed light source, and the reflectivity of the reflective spherical surface is greater than that of the reflective plane;
or, on the light path of the seed light beam, the reflection plane is located on one side of the reflection spherical surface away from the seed light source; the reflectivity of the reflecting plane is larger than that of the reflecting spherical surface.
Optionally, the laser further includes a phase adjusting module, located on the optical path of the seed light beam, and configured to adjust the phase of the seed light beam, so that the semi-confocal cavity meets an external cavity self-injection locking condition, and forms a frequency-locked laser.
Optionally, the phase adjustment module includes a temperature-controlled optical element for changing a refractive index of the temperature-controlled optical element according to a temperature change to adjust the phase of the seed beam, or an electro-optical effect optical element for changing the refractive index of the electro-optical effect to adjust the phase of the seed beam.
Optionally, the laser device further comprises a cavity length adjusting module, wherein the cavity length adjusting module is configured to change a length of a circular reflection path of the seed beam in the semi-confocal cavity to generate frequency-locked lasers with different frequencies.
Optionally, the laser device further comprises an optical cavity position adjusting module, wherein the optical cavity position adjusting module is configured to change a position of the semi-confocal cavity on an optical path of the seed light beam to generate frequency-locked lasers with different frequencies.
Optionally, the optical system further comprises a light beam coupling module, wherein the light beam coupling module is configured to couple the seed light beam into the semi-confocal cavity, and is further configured to couple a feedback light beam of the semi-confocal cavity into the seed light source.
Optionally, the seed light source comprises a semiconductor laser; or, the seed light source comprises a gain chip and an optical filter, and the optical filter is located on the light path of the seed light beam.
The narrow linewidth external cavity laser device based on the semi-confocal cavity comprises a seed light source and the semi-confocal cavity, wherein the seed light source is used for outputting a seed light beam, the semi-confocal cavity is used for reflecting the seed light beam internally and then feeding the reflected seed light beam back to the seed light source to form a feedback light path, and the semi-confocal cavity meets the external cavity self-injection locking condition to form frequency-locked laser. The semi-confocal cavity comprises a reflecting plane and a reflecting spherical surface, the reflecting spherical surface is convex towards one side departing from the reflecting plane, and the reflecting plane is positioned on the focal plane of the reflecting spherical surface; the reflecting plane is inclined relative to the light path of the seed light beam, the focus of the reflecting spherical surface on the reflecting plane is positioned on the light path of the seed light beam, and the seed light beam is emitted from the original light path after being circularly reflected for multiple times between the reflecting plane and the reflecting spherical surface, so that the resonance of the laser external cavity is realized. The embodiment of the utility model solves the problem of larger volume of the existing narrow linewidth laser device, utilizes the reflection plane and the reflection spherical surface to form a semi-confocal cavity, and uses the semi-confocal cavity as a feedback external cavity, thereby realizing narrow linewidth frequency-locked laser, and simultaneously, the feedback external cavity structure formed by two surface-shaped structures of the plane and the spherical surface has smaller volume, is more convenient for the layout of the feedback external cavity, and is beneficial to the miniaturization of the narrow linewidth laser device. In addition, the semi-confocal cavity can reduce the number of spherical surfaces relative to a spherical cavity, reduce the processing difficulty of a feedback outer cavity, improve the control capability of the cavity length precision and be more beneficial to practical application.
Drawings
Fig. 1 is a schematic structural diagram of a narrow linewidth external cavity laser device based on a semi-confocal cavity according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of the incident feedback path of the semi-confocal cavity shown in FIG. 1;
fig. 3 is a schematic structural diagram of another narrow linewidth external cavity laser device according to an embodiment of the present invention;
fig. 4 is a schematic structural diagram of another narrow linewidth external cavity laser device according to an embodiment of the present invention;
fig. 5 is a schematic structural diagram of another narrow linewidth external cavity laser device according to an embodiment of the present invention;
fig. 6 is a schematic structural diagram of another narrow linewidth external cavity laser device according to an embodiment of the present invention;
FIG. 7 is a schematic diagram illustrating an incident feedback path of another semi-confocal cavity provided in an embodiment of the present invention;
fig. 8 is a schematic structural diagram of another narrow linewidth laser apparatus according to an embodiment of the present invention;
fig. 9 is a schematic structural diagram of another narrow linewidth laser device according to an embodiment of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the utility model and are not limiting of the utility model. It should be further noted that, for the convenience of description, only some of the structures related to the present invention are shown in the drawings, not all of the structures.
Research shows that the resonant cavity can remarkably narrow the line width of the semiconductor laser by using a high-quality factor (also called Q value, reflecting the relation between the energy storage and the loss of the resonant cavity, wherein the lower the loss of the cavity, the longer the average life of photons in the cavity and the narrower the line width). The FP cavity is used as a high Q optical cavity, so that the heat absorption and nonlinear effects can be obviously reduced, and narrow linewidth laser is realized.
The confocal cavity has the advantage of insensitivity to incident light angle and mode field, and the incident light can be obliquely incident, is favorable to forming the characteristics of feedback. Common FP confocal cavity forms include a parallel plane cavity and a spherical cavity, however, the existing parallel plane cavity has a large mode volume, laser radiation in the cavity does not have a focusing phenomenon, but diffraction loss is high, and the difficulty in adjusting the mirror surface is high. The spherical confocal cavity needs the two spherical reflectors with the same curvature radius, the length of the optical axis is equal to the curvature radius, if deviation exists, the fineness of the resonant cavity is affected, and the conditions are harsh. In addition, the surface of the spherical reflector needs to be polished and ground, the processing difficulty is high, the spherical surface with the smaller curvature radius has higher processing difficulty, the precision requirement on the optical axis length is also high, the size of the self-injection external cavity laser used for optical fiber sensing has more severe requirement, and the traditional spherical cavity is not beneficial to the miniaturization of laser products.
In view of the above-mentioned drawbacks, an embodiment of the present invention provides a narrow linewidth external cavity laser device based on a semi-confocal cavity, and fig. 1 is a schematic structural diagram of a narrow linewidth external cavity laser device based on a semi-confocal cavity provided in an embodiment of the present invention, and referring to fig. 1, the narrow linewidth external cavity laser device includes: a seed light source 10 for outputting a seed light beam 100; the semi-confocal cavity 20 is used for reflecting the seed light beam 100 internally and then feeding back the reflected seed light beam to the seed light source 10 to form a feedback light path, and the semi-confocal cavity 20 meets the external cavity self-injection locking condition to form frequency-locked laser; the semi-confocal cavity 20 comprises a reflecting plane 21 and a reflecting spherical surface 22 which are opposite to each other in reflecting surface, the reflecting spherical surface 22 is convex towards one side away from the reflecting plane 21, and the reflecting plane 21 is positioned on the focal plane of the reflecting spherical surface 22; the reflection plane 21 is inclined with respect to the optical path of the seed light beam 100, the focal point f of the reflection spherical surface 22 on the reflection plane 21 is located on the optical path of the seed light beam 100, and the seed light beam 100 is emitted from the original optical path after being circularly reflected for multiple times between the reflection plane 21 and the reflection spherical surface 22.
For the structure of the semi-confocal cavity 20 provided in the embodiment of the present invention, firstly, as can be known by those skilled in the art, the focal length F of the reflective spherical surface 22 is equal to one-half of the curvature radius R thereof, and the reflective plane 21 is disposed on the focal plane of the reflective spherical surface 22 in the embodiment of the present invention, and the reflective plane 21 is substantially disposed at a position half of the curvature radius R of the reflective spherical surface 22, that is, the central distance L between the reflective plane 21 and the reflective spherical surface 22 and the curvature radius R of the reflective spherical surface 22 satisfy: and L is R/2. At this time, the light beam reflected by the reflecting spherical surface 22 is focused on the reflecting plane 21. Further, fig. 2 is a schematic diagram of an incident feedback optical path of the semi-confocal cavity shown in fig. 1, referring to fig. 1 and fig. 2, the reflection plane 21 is disposed to be inclined with respect to the optical path of the seed light beam 100, and the focal point f of the reflection spherical surface 22 on the reflection plane 21 is located on the optical path of the seed light beam 100, and the seed light source 10 is substantially disposed to emit toward the focal point f of the reflection spherical surface 22 on the reflection plane 21, it can be understood that, since the seed light beam 100 passes through the focal point f of the reflection spherical surface 22, when the seed light beam enters the reflection plane (position a) of the reflection spherical surface 22, the light beam will undergo a first reflection along the direction perpendicular to the reflection plane 21, and when the reflection plane 21 (position b) is reached, the reflection plane 21 will undergo a second reflection along the original path, and then, at the same position (position a) of the reflection spherical surface 22, the light beam will undergo a third reflection towards the focal point f of the reflection plane 21, the reflected light beam is reflected for the fourth time at the focal position f of the reflecting plane 21, and the reflected light beam after the fourth reflection is reflected in a mirror image manner at the reflecting plane 21 and the lower half part of the reflecting spherical surface 22 (at the position c of the reflecting spherical surface 22 and at the position d of the reflecting plane 21) and returns to the focal position f of the reflecting plane 21 again in a similar reflection manner as described above. Thus, the seed beam 100 is substantially circularly reflected between the reflection plane 21 and the reflection sphere 22 along the path of a-b-a-f-c-d-c-f-a in sequence after being incident to the focal point f, thereby forming resonance. It should be noted that, in the embodiment of the present invention, the reflection plane 21 may be configured to have a partially transmissive and partially reflective capability at least the position f, that is, when the reflected light beam in the cavity is incident from the position a to the position f, a part of the light beam is transmitted by the reflection plane 21 and fed back to the seed light source 10 along the original path of the seed light beam 100, so as to form an external cavity resonance.
In this embodiment, the semi-confocal cavity 20 is substantially an external cavity of the seed light source 10, and is responsible for reflecting the seed light beam 100 internally and feeding back the reflected seed light beam to the seed light source 10 along the original path, so that the seed light beam 100 generates resonance in the external cavity, and forms external cavity frequency self-injection locking. In this process, the semi-confocal cavity 20 serves as an external cavity to resonate the seed light beam 100, so that the frequency self-injection locking of the external cavity is realized, and at the same time, the semi-confocal cavity serves as an FP cavity with a high Q value, and the self-resonance is utilized to form the frequency self-injection locking. The high-Q confocal cavity 20 can further narrow the line width of the seed beam 100 by cooperating with the self-injection locking of the frequency thereof on the basis of the self-injection locking of the frequency of the external cavity to narrow the line width of the seed beam 100.
The narrow linewidth external cavity laser device based on the semi-confocal cavity comprises a seed light source and the semi-confocal cavity, wherein the seed light source is used for outputting a seed light beam, the semi-confocal cavity is used for reflecting the seed light beam internally and then feeding the seed light beam back to the seed light source to form a feedback light path, and the semi-confocal cavity meets the external cavity self-injection locking condition to form frequency-locked laser. The semi-confocal cavity comprises a reflecting plane and a reflecting spherical surface, the reflecting spherical surface is convex towards one side departing from the reflecting plane, and the reflecting plane is positioned on the focal plane of the reflecting spherical surface; the reflecting plane inclines relative to the light path of the seed light beam, the focus of the reflecting spherical surface on the reflecting plane is positioned on the light path of the seed light beam, and the seed light beam is emitted from the original light path after being circularly reflected for multiple times between the reflecting plane and the reflecting spherical surface, so that the resonance of the laser external cavity is realized. The embodiment of the utility model solves the problem of larger volume of the existing narrow linewidth laser device, utilizes the reflection plane and the reflection spherical surface to form a semi-confocal cavity, and uses the semi-confocal cavity as a feedback external cavity, thereby realizing narrow linewidth frequency-locked laser, and simultaneously, the feedback external cavity structure formed by two surface-shaped structures of the plane and the spherical surface has smaller volume, is more convenient for the layout of the feedback external cavity, and is beneficial to the miniaturization of the narrow linewidth laser device. In addition, the semi-confocal cavity can reduce the number of spherical surfaces relative to a spherical cavity, reduce the processing difficulty of a feedback outer cavity, improve the control capability of the cavity length precision and be more beneficial to practical application.
It should be noted that, in the above-mentioned embodiment of fig. 1, the reflective spherical surface 22 is disposed on the optical path of the seed light beam 100 on the side of the reflective plane 21 away from the seed light source 10, which is only one embodiment of the present invention, and on the basis of satisfying that the seed light beam is obliquely incident on the focal point of the reflective spherical surface on the reflective plane, the positions of the reflective plane and the reflective spherical surface can be reversed in a front-back mirror image manner, in other words, the solution that the reflective plane is disposed on the optical path of the seed light beam on the side of the reflective spherical surface away from the seed light source also falls within the protection scope of the present invention.
The narrow linewidth external cavity laser device based on the semi-confocal cavity of the present invention is described in two specific embodiments below. Fig. 3 is a schematic structural diagram of another narrow linewidth external cavity laser device according to an embodiment of the present invention, referring to fig. 3, in this embodiment, a semi-confocal cavity 20 includes a plano-convex lens 200, and the plano-convex lens 200 includes a reflective plane 21 and a reflective spherical surface 22.
In this embodiment, the plane and the spherical surface of the planoconvex lens 200 have the ability of transmitting light, and simultaneously can also realize the function of internal multiple reflection, that is, the plane and the spherical surface of the planoconvex lens 200 can be used as the reflection plane 21 and the reflection spherical surface 22 in the above embodiments. The plano-convex lens 200 is a single solid structure and has the reflecting plane 21 and the reflecting spherical surface 22 to realize a semi-confocal cavity, so that the number of optical elements of the laser device is reduced, and the processing process of the optical elements is simplified.
It should be noted that, in the case of the plano-convex lens 200, when the seed beam 100 is incident on the focal point f of the reflection plane 21, there is at least partial energy transmission, and the transmitted light enters the interior of the plano-convex lens 200 and forms a circular reflection between the reflection plane 21 and the reflection spherical surface 22. Meanwhile, partial energy transmission is generated at the reflection position of the reflection plane 21 and the reflection spherical surface 22 in the process. At this time, a transmitted beam can be selected as the frequency-locked laser output according to the laser light emitting direction, and of course, a beam splitting device for outputting the frequency-locked laser can be additionally arranged on the optical path of the seed beam. Fig. 4 is a schematic structural diagram of another narrow linewidth external cavity laser device provided in an embodiment of the present invention, and comparing fig. 3 and fig. 4, in an embodiment of the present invention, a beam splitter 30 may be disposed on an optical path of the seed light beam 100, and is configured to split the seed light beam 100 into two beams as a frequency-locked laser output, and a reflected light of the beam splitter may be specifically configured to be used as the frequency-locked laser output (as shown in fig. 3), or a transmitted light of the beam splitter 30 may be specifically configured to be used as the frequency-locked laser output (as shown in fig. 4).
Fig. 5 is a schematic structural diagram of another narrow linewidth external cavity laser device according to an embodiment of the present invention, referring to fig. 5, in this embodiment, a semi-confocal cavity 20 includes a plane mirror 210 and a spherical mirror 220, the plane mirror 210 includes a reflective plane 21, and the spherical mirror 220 includes a reflective spherical surface 22.
In this embodiment, the plane mirror 210 and the spherical mirror 220 are separately prepared optical elements, and at this time, the reflectivity of the reflection plane 21 and the reflection spherical surface 22 and whether the optical elements have light transmission capability may be separately designed, for example, a reflection film or an antireflection film may be coated on the surface or the back surface of the plane mirror 210 and the spherical mirror 220, so as to optimize the external cavity resonance of the semi-confocal cavity 20, improve the energy utilization rate, and improve the output energy of the frequency-locked laser.
Further, in the embodiment of the present invention, the optional seed light source includes a semiconductor laser, or the seed light source includes a gain chip and an optical filter, and the optical filter is located on the optical path of the seed light beam.
Referring to fig. 1, a seed light source 10, which is essentially an optical cavity with gain, may be selected from a semiconductor laser 11 to generate a seed beam with a wider linewidth. Fig. 6 is a schematic structural diagram of another narrow linewidth external cavity laser device according to an embodiment of the present invention, referring to fig. 6, the seed light source 10 may also adopt a combination of a gain chip 12 and a filter 13, where the gain chip 12 has a higher gain for a specific wavelength band (for example, C-band), and the filter 13 may select a laser wavelength within a gain spectral range (several tens of nm) of the gain chip 12.
With continuing reference to fig. 3 and 5, an optional embodiment of the present invention further includes a beam coupling module 40, where the beam coupling module 40 is configured to couple the seed beam 100 into the confocal semi-cavity 20 and further configured to couple the feedback beam from the confocal semi-cavity 20 into the seed light source 10. The beam coupling module 40 is illustrated in fig. 3 and 5 as comprising a focusing lens 41, i.e. the light beam is coupled through the lens. The focusing lens 41 will match the light field distribution of the incident light to the semi-confocal cavity 20 with the light field distribution of the resonance mode of the semi-confocal cavity 20, and the focusing lens 41 is used to optimize the light field distribution of the feedback laser light of the semi-confocal cavity 20, so that the feedback laser light can be better coupled with the seed light source 10.
As shown in fig. 2, when the reflection plane and the reflection spherical surface have both reflection capability and transmission capability, the intracavity energy output of the whole semi-confocal cavity includes five positions a, b, c, d and f as shown in fig. 2, and the remaining three positions a, c and f have outputs in two directions except for the position b and d on the reflection plane 21, so that the intracavity energy output of the semi-confocal cavity has 8 ports in total, and the output energy fed back along the original path of the seed light beam 100 at the position f has only 1/8 at most. Based on this, in consideration of the feedback energy for the seed beam in the semi-confocal cavity, the reflectivity and the transmissivity of the reflecting plane and the reflecting spherical surface can be designed respectively in the embodiment of the utility model.
Fig. 7 is a schematic diagram of an incident feedback optical path of another semi-confocal cavity provided in an embodiment of the present invention, referring to fig. 7, in the semi-confocal cavity of this embodiment, in an optical path of the seed light beam 100, the reflective spherical surface 22 is located on a side of the reflective plane 21 away from the seed light source 10, and a reflectivity of the reflective spherical surface 22 is greater than a reflectivity of the reflective plane 21.
At this time, when the seed light beam 100 enters the semi-confocal cavity 20, the reflectivity of the light beam in the cavity on the reflective spherical surface 22 is greater than that of the reflective plane 21, so that the reflectivity of the light beam on the reflective spherical surface 22 can be improved, the transmission of the light beam on the reflective spherical surface 22 can be reduced, and the light beam energy is concentrated on the reflective plane 21 to exit. More specifically, the reflectivity of the reflecting spherical surface may be set to be much larger than that of the reflecting plane, or the reflecting spherical surface may be set to have no transmission capability. At this time, there is only light reflection and no light transmission at the positions a and c of the reflection sphere, which reduces the energy output ports of the 4 semi-confocal cavities 20 and increases the energy of the laser light fed back from the position f along the original path of the seed light beam 100 to 1/4.
It should be noted that the reflectivity design of the reflective spherical surface and the reflective flat surface needs to be determined according to the positions of the reflective spherical surface and the reflective flat surface on the seed beam optical path. It can be understood that the embodiment of the present invention aims to improve the laser energy fed back, and therefore, when the reflection plane is located on the side of the reflection spherical surface far away from the seed light source in the optical path of the seed light beam, the reflectivity of the reflection plane is optionally greater than that of the reflection spherical surface. At the moment, the reflecting spherical surface is a transmission surface for feeding back laser, the reflecting capacity of the reflecting plane is relatively increased, the light transmission capacity of the reflecting plane is reduced, more energy in the cavity can be transmitted by the reflecting spherical surface, and the energy of the laser fed back is improved.
Further, in view of practical applications, the embodiments of the present invention provide more specific structural examples for the narrow linewidth laser apparatus described above. Fig. 8 is a schematic structural diagram of another narrow linewidth laser apparatus according to an embodiment of the present invention, and referring to fig. 8, on the basis of the above embodiment, the narrow linewidth laser apparatus further includes a phase adjustment module 50, where the phase adjustment module 50 is located on an optical path of the seed beam 100 and is used for adjusting a phase of the seed beam 100, so that the semi-confocal cavity 20 satisfies an external-cavity self-injection locking condition to form a frequency-locked laser.
Specifically, the phase adjustment module 50 may include a temperature-controlled optical element or an electro-optical effect optical element (not shown in fig. 8) disposed on the optical path of the seed light beam 100, the temperature-controlled optical element being configured to change the refractive index thereof according to a temperature change to adjust the phase of the seed light beam, and the electro-optical effect optical element being configured to change the refractive index thereof according to an electro-optical effect to adjust the phase of the seed light beam. The change of the refractive index can substantially change the optical path of the light beam, namely, the phase adjustment of the light beam is realized, so that the whole laser device meets the external cavity self-injection locking condition, and the frequency-locked laser is formed. Further, a detection unit (not shown in fig. 8), such as a beam splitter and an optical detection element, may be added to the phase adjustment module 50 for detecting the intensity of the seed light beam 100 entering the semi-confocal cavity 20 and the feedback laser light emitted from the semi-confocal cavity 20, so as to determine the frequency locking position of the feedback light peak of the semi-confocal cavity 20, and thus serve as a basis for adjusting the feedback phase.
On the basis of the above embodiments, the narrow linewidth laser device provided in the embodiments of the present invention may further include a frequency continuous adjustment function. Fig. 9 is a schematic structural diagram of another narrow linewidth laser apparatus according to an embodiment of the present invention, referring to fig. 9, the narrow linewidth laser apparatus further includes a cavity length adjusting module 60, and the cavity length adjusting module 60 is configured to change a length of a circular reflection path of the seed beam 100 in the semi-confocal cavity 20 to generate frequency-locked lasers with different frequencies.
As can be known to those skilled in the art, for the FP cavity, the cavity length thereof determines the resonant frequency to a certain extent, and here the cavity length adjusting module 60 changes the cavity length of the semi-confocal cavity 20, so as to dynamically adjust the frequency resonance state of the semi-confocal cavity 20 and change the frequency of the frequency-locked laser, thereby enabling the whole narrow-linewidth laser device to output narrow-linewidth frequency-locked lasers with different frequencies. It should be noted that the cavity length of the semi-confocal cavity 20 herein does not refer to the center-to-center distance between the reflection plane and the reflection sphere, but refers to the length of the circular reflection inside the semi-confocal cavity 20, and can also be understood as the optical path length of the light beam in the semi-confocal cavity 20. The cavity length adjusting module 60 of the semi-confocal cavity 20 may be a piezoelectric ceramic or an electronic control position device, for example, the piezoelectric ceramic or the electronic control position device may be used to adjust the tilt angle of the semi-confocal cavity 20, at this time, the reflection path of the seed light beam 100 in the semi-confocal cavity 20 changes, the reflection positions on the reflection plane and the reflection spherical surface, except for the focal point f, both move, and the optical path of the light beam in the semi-confocal cavity 20 changes. In addition, the cavity length adjusting module 60 can also be set as a temperature control device, and the optical path of the semi-confocal cavity 20 can be changed by changing the refractive index of the medium in the semi-confocal cavity 20, so as to change the resonance state thereof and adjust the frequency-locked laser frequency.
In addition to adjusting the frequency of the entire frequency-locked laser by changing the frequency-locked state of the semi-confocal cavity, the embodiment of the present invention can also optionally adjust the external cavity to adjust the frequency of the entire frequency-locked laser. With continued reference to fig. 9, the narrow linewidth laser apparatus may further include an optical cavity position adjusting module 70, where the optical cavity position adjusting module 70 is configured to change the position of the semi-confocal cavity 20 on the optical path of the seed beam 100 to generate the frequency-locked laser with different frequencies.
The laser device may also be a piezoelectric ceramic or an electric control position device, and the piezoelectric ceramic or the electric control position device may translate the whole semi-confocal cavity 20 on the light path of the seed light beam 100, at this time, the external cavity structure of the laser device changes, and the optical path changes, so as to adjust the external cavity resonance state, change the external cavity resonance frequency, and adjust the frequency-locked laser frequency.
It should be noted that, when the frequency of the entire frequency-locked laser is adjusted, the embodiments of the present invention not only need to synchronously adjust the resonant frequencies of the semi-confocal cavity and the external cavity to generate the cooperative resonance of the semi-confocal cavity resonance and the external cavity resonance, but also need to adjust the eigen frequency of the seed light source, and by making the frequencies of the three in a substantially aligned state, the frequency-locked laser device can satisfy the frequency-locked laser of the entire laser device and dynamically output the laser with different frequencies. The phase adjusting module, the cavity length adjusting module and the optical cavity position adjusting module provided in the above embodiments can respectively adjust the resonance state of the external cavity or the semi-confocal cavity, and based on the above at least two adjusting modules, the semi-confocal cavity and the external cavity can be adjusted in synchronous frequency, and the frequency-locked laser frequency of the whole laser device can be adjusted corresponding to the eigen frequency of the seed light source.
It is to be noted that the foregoing is only illustrative of the preferred embodiments of the present invention and the technical principles employed. It will be understood by those skilled in the art that the present invention is not limited to the particular embodiments described herein, but is capable of various obvious modifications, rearrangements, combinations and substitutions as will now become apparent to those skilled in the art without departing from the scope of the utility model. Therefore, although the present invention has been described in greater detail by the above embodiments, the present invention is not limited to the above embodiments, and may include other equivalent embodiments without departing from the spirit of the present invention, and the scope of the present invention is determined by the scope of the appended claims.
Claims (10)
1. A narrow linewidth external cavity laser device based on a semi-confocal cavity is characterized by comprising:
a seed light source for outputting a seed light beam;
the semi-confocal cavity is used for reflecting the seed light beam internally and feeding back the seed light beam to the seed light source to form a feedback light path, and the semi-confocal cavity meets the external cavity self-injection locking condition to form frequency-locked laser;
the semi-confocal cavity comprises a reflecting plane and a reflecting spherical surface, wherein the reflecting plane and the reflecting spherical surface are opposite, the reflecting spherical surface is convex towards one side departing from the reflecting plane, and the reflecting plane is positioned on the focal plane of the reflecting spherical surface;
the reflecting plane is inclined relative to the light path of the seed light beam, the focus of the reflecting spherical surface on the reflecting plane is located on the light path of the seed light beam, and the seed light beam is emitted from the original light path after being circularly reflected for multiple times between the reflecting plane and the reflecting spherical surface.
2. The narrow linewidth external cavity laser device according to claim 1, wherein the semi-confocal cavity comprises a plano-convex lens comprising the reflective plane and the reflective spherical surface.
3. The narrow linewidth external cavity laser device according to claim 1, wherein the semi-confocal cavity comprises a plane mirror and a spherical mirror, the plane mirror comprising the reflecting plane and the spherical mirror comprising the reflecting sphere.
4. The narrow linewidth external cavity laser device according to claim 1, wherein the reflective spherical surface is located on a side of the reflective plane away from the seed light source in an optical path of the seed light beam, and a reflectivity of the reflective spherical surface is greater than a reflectivity of the reflective plane;
or, on the light path of the seed light beam, the reflection plane is located on one side of the reflection spherical surface away from the seed light source; the reflectivity of the reflecting plane is larger than that of the reflecting spherical surface.
5. The narrow linewidth external cavity laser device according to claim 1, further comprising a phase adjustment module, located on the optical path of the seed beam, for adjusting the phase of the seed beam, so that the semi-confocal cavity satisfies an external cavity self-injection locking condition to form a frequency-locked laser.
6. The narrow linewidth external cavity laser device according to claim 5, wherein the phase adjustment module comprises a temperature-controlled optical element for changing a refractive index thereof according to a temperature change to adjust the phase of the seed beam or an electro-optical effect optical element for changing a refractive index thereof according to an electro-optical effect to adjust the phase of the seed beam.
7. The narrow linewidth external cavity laser device according to claim 1, further comprising a cavity length adjusting module for changing a length of a circulating reflection path of the seed beam in the semi-confocal cavity to generate frequency-locked laser light of different frequencies.
8. The narrow linewidth external cavity laser device according to claim 1, further comprising an optical cavity position adjusting module for changing the position of the semi-confocal cavity on the optical path of the seed beam to generate the frequency-locked laser light with different frequencies.
9. The narrow linewidth external cavity laser device according to claim 1, further comprising a beam coupling module for coupling the seed beam into the semi-confocal cavity and for coupling a feedback beam from the semi-confocal cavity into the seed light source.
10. The narrow linewidth external cavity laser device of claim 1, wherein the seed light source comprises a semiconductor laser; or, the seed light source comprises a gain chip and an optical filter, and the optical filter is located on the light path of the seed light beam.
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