阅读说明：本技术 带有猫眼反射器的饱和吸收光谱稳频光学系统 (Saturated absorption spectrum frequency stabilization optical system with cat eye reflector ) 是由 贾森 王先华 于 2020-06-02 设计创作，主要内容包括：本发明涉及激光器稳频技术领域,提出了一种带有猫眼反射器的饱和吸收光谱稳频光学系统,旨在解决现有的饱和吸收光谱稳频光学系统光路稳定性差的技术问题。本发明包括沿同一光轴依次设置的偏振分束器、四分之一波片、原子源玻璃泡,以及设置在偏振分束器反射光路上的光电探测器；改进之处为在原子源玻璃泡输出光路上设置有猫眼反射器,使入射光与反射光在光路上完全共线,光束准直性好,对光路中光学器件的角度失配不敏感,光路调节难度低,固定后不易受外界震动、温度等环境影响,提高了光学系统的稳定度。(The invention relates to the technical field of laser frequency stabilization, provides a saturated absorption spectrum frequency stabilization optical system with a cat eye reflector, and aims to solve the technical problem that the existing saturated absorption spectrum frequency stabilization optical system is poor in light path stability. The invention comprises a polarization beam splitter, a quarter wave plate, an atomic source glass bubble and a photoelectric detector, wherein the polarization beam splitter, the quarter wave plate and the atomic source glass bubble are sequentially arranged along the same optical axis; the improvement is that the cat eye reflector is arranged on the output light path of the atomic source glass bulb, so that incident light and reflected light are completely collinear on the light path, the collimation of the light beam is good, the light path is insensitive to the angle mismatch of optical devices in the light path, the light path adjusting difficulty is low, the cat eye reflector is not easily influenced by external vibration, temperature and other environments after being fixed, and the stability of the optical system is improved.)

1. The saturated absorption spectrum frequency stabilization optical system with the cat eye reflector comprises a polarization beam splitter (201), a quarter-wave plate (203), an atomic source glass bubble (204) and a photoelectric detector (208), wherein the polarization beam splitter (201), the quarter-wave plate (203), the atomic source glass bubble (204) and the photoelectric detector (208) are sequentially arranged along the same optical axis;

the method is characterized in that:

and the atomic source glass bubble also comprises a cat eye reflector (210) arranged on the output light path of the atomic source glass bubble (204).

2. The saturated absorption spectrum frequency stabilization optical system with the cat-eye reflector according to claim 1, characterized in that: the cat eye reflector (210) consists of a convex lens (206) and a plano-concave mirror (207); the concave surface of the plano-concave mirror (207) is opposite to the convex lens (206); the focal length of the convex lens (206), the concave curvature radius of the planoconvex lens (207) and the distance between the convex lens (206) and the planoconvex lens (207) are equal.

3. The saturated absorption spectrum frequency stabilization optical system with the cat-eye reflector according to claim 2, characterized in that: the convex lens (206) and the plano-concave mirror (207) are arranged on the same base, and the distance between the convex lens and the plano-concave mirror is adjustable and can be locked by using a locking hole.

4. The saturated absorption spectrum frequency stabilization optical system with the cat-eye reflector according to claim 1, characterized in that: the cat eye reflector (210) consists of a convex lens (206) and a plane total reflector (207B); the reflecting surface of the plane total reflector (207B) is opposite to the convex lens (206); the distance from the reflecting surface of the plane total reflector (207B) to the convex lens (206) is equal to the focal length of the convex lens (206).

5. The saturated absorption spectrum frequency stabilization optical system with the cat-eye reflector according to claim 4, characterized in that: the convex lens (206) and the plane total reflector (207B) are arranged on the same base, and the distance between the convex lens and the plane total reflector is adjustable and can be locked by using a locking hole.

6. The frequency-stabilized optical system of any one of claims 1-5 with a cat-eye reflector, characterized by: further comprising a trapezoidal prism (205); two isosceles side surfaces and the lower bottom surface of the trapezoidal prism (205) form an angle of 45 degrees;

the trapezoidal prism (205) is arranged on a front end light path of the cat eye reflector (210); the light beam transmitted by the quarter wave plate (203) passes through the atom source glass bubble (204) and then enters the trapezoidal prism (205), and the reflected light beam of the trapezoidal prism (205) enters the atom source glass bubble (204) and then enters the cat eye reflector (210).

7. The saturated absorption spectrum frequency stabilization optical system with the cat-eye reflector according to claim 6, characterized in that: the lower bottom surface of the trapezoidal prism (205), the front and rear light-passing surfaces of the quarter-wave plate (203) and the two light-passing surfaces of the convex lens (206) are respectively plated with an anti-reflection film corresponding to the passed laser wavelength; the surfaces of two isosceles side surfaces of the trapezoidal prism (205) and the concave surface of the plano-concave mirror (207) are plated with reflecting films corresponding to the reflected laser wavelength.

Technical Field

The invention relates to the technical field of laser frequency stabilization, in particular to a saturated absorption spectrum frequency stabilization optical system with a cat eye reflector, which is mainly used for laser frequency stabilization.

Background

The semiconductor laser is widely applied to the fields of precise spectrum, quantum optics, atomic cooling, atomic interference and the like. In the fields of atomic cooling and atomic interference, the frequency stabilization of a semiconductor laser is firstly carried out, and the frequency stabilization optical system which is widely applied at presentThe system is a saturated absorption spectrum frequency stabilization system which can clearly distinguish⁸⁷The main absorption peak of the Rb atom locks the frequency of the laser to the several absorption peaks where the signal is strongest. Fig. 1 shows a conventional saturated absorption spectrum frequency stabilization optical system, which mainly includes a polarization beam splitter 101, a quarter-wave plate 102 disposed on a rotary mounting base 103, an atomic source glass bubble 104, a 0-degree total reflection mirror 105, and a photodetector 106; the input linear polarization laser beam 100 sequentially passes through the polarization beam splitter 101 and the quarter wave plate 102, enters the atomic source glass bubble 104, is reflected by the 0-degree total reflection mirror 105, returns along the original path, passes through the quarter wave plate 102 again, rotates the polarization direction by 90 degrees, is reflected by the polarization beam splitter 101, and reaches the photoelectric detector 107, and the saturated absorption spectrum signal is converted into an electric signal by the photoelectric detector 107. The electrical signal is processed by a subsequent circuit to obtain a frequency discrimination signal, the frequency discrimination signal is provided for a laser servo system, and the laser is frequency-stabilized by the laser servo system, and the specific implementation method is shown in corresponding parts of figure 3 in 'appl.phys.b84, 683-690 (2006)' and figure 6.6 in 'mater wave interference in microorganisation, pp175 (2014)'.

The conventional frequency stabilization optical system with a saturated absorption spectrum shown in fig. 1 has the advantages of simple structure and easy adjustment, but in practical application, there are many problems:

1) performance is limited;

to obtain a strong signal absorption peak for frequency locking, an atomic source glass bubble with a longer length must be used, which inevitably increases the length of the optical path of the whole optical system, so that the optical system cannot meet the use requirements in the application occasions with high requirements on miniaturization and integration, and the use range of the optical system is limited.

2) The stability is poor;

the signal light reflectors all adopt 0-degree total reflection mirrors, and the stability of the light path is mainly determined by the 0-degree total reflection mirrors in the system. Due to environmental vibration and temperature change, the laser beam generates angle deflection and linear displacement on the 0-degree total reflector, the spatial coincidence degree of reflected light and incident light in the atomic source glass bubble is changed therewith, and meanwhile, the signal beam reflected to the photoelectric detector also generates angle deflection and linear displacement, and the two factors cause that the intensity of a saturated absorption signal generates large jitter, so that the frequency discrimination signal is greatly changed, and the frequency stabilization performance of the laser is poor.

3) The matching with a temperature control device is poor;

two light-passing surfaces of the atomic source glass bubble cannot be absolutely parallel and always have a certain included angle, and the atomic source glass bubble can be regarded as an optical wedge with a small wedge angle (in some embodiments, two light-passing surfaces of the atomic source glass bubble have symmetrical inclination of 4-8 degrees, and the symmetrical angles cannot be completely the same, so that the atomic source glass bubble can also be regarded as an optical wedge with a small wedge angle). Meanwhile, in many cases, a heating device needs to be installed on the atom source glass bubble, the atom source is enabled to work at the optimal temperature through temperature control, however, due to fluctuation of the ambient temperature, the atom source glass bubble in the optical path at the moment is equivalent to an optical wedge with a wedge angle changing with temperature, the spatial coincidence degree of reflected light and incident light in the atom source glass bubble can be changed, the signal beam reflected to the photoelectric detector is also subjected to angle deflection and linear displacement, and therefore the frequency discrimination signal is greatly changed, and the frequency stabilization performance of the laser is poor or even the laser is unlocked.

Disclosure of Invention

The invention provides a saturated absorption spectrum frequency stabilization optical system with a cat eye reflector, which aims to solve the technical problem that the existing saturated absorption spectrum frequency stabilization optical system is poor in light path stability.

The technical solution of the invention is as follows:

the saturated absorption spectrum frequency stabilization optical system with the cat eye reflector comprises a polarization beam splitter, a quarter-wave plate, an atomic source glass bubble and a photoelectric detector, wherein the polarization beam splitter, the quarter-wave plate and the atomic source glass bubble are sequentially arranged along the same optical axis;

the method is characterized in that:

the atomic source glass bubble output optical path is arranged on the atomic source glass bubble.

Further, the cat eye reflector consists of a convex lens and a plano-concave mirror; the concave surface of the plano-concave mirror is opposite to the convex lens; the focal length of the convex lens, the concave curvature radius of the planoconvex lens and the distance between the convex lens and the planoconvex lens are equal.

Furthermore, convex lens and plano-concave mirror set up on same base, and both's interval is adjustable and can utilize the locking hole to lock.

Furthermore, the cat eye reflector consists of a convex lens and a plane total reflector; the reflecting surface of the plane total reflector is opposite to the convex lens; the distance from the reflecting surface of the plane total reflector to the convex lens is equal to the focal length of the convex lens.

Furthermore, the convex lens and the plane total reflector are arranged on the same base, the distance between the convex lens and the plane total reflector is adjustable, and the convex lens and the plane total reflector can be locked by using a locking hole.

Further, the device also comprises a trapezoidal prism; two isosceles side surfaces of the trapezoidal prism and the lower bottom surface form an angle of 45 degrees;

the trapezoidal prism is arranged on the light path at the front end of the cat eye reflector; and the light beam transmitted by the quarter-wave plate enters the trapezoidal prism after passing through the atom source glass bubble, and the reflected light beam of the trapezoidal prism enters the atom source glass bubble and then enters the cat eye reflector.

Furthermore, the lower bottom surface of the trapezoidal prism, the front and rear light-passing surfaces of the quarter-wave plate and the two light-passing surfaces of the convex lens are plated with antireflection films corresponding to the passed laser wavelength; the surfaces of the two isosceles side surfaces of the trapezoidal prism and the concave surface of the plano-concave mirror are plated with reflecting films corresponding to the reflected laser wavelength.

The invention has the beneficial effects that:

1) the cat eye reflector is used, so that incident light and reflected light are completely collinear on the light path, the collimation of the light beam is good, the cat eye reflector is insensitive to the angle mismatch of optical devices in the light path, the light path adjustment difficulty is low, the cat eye reflector is not easily influenced by external vibration, temperature and other environments after being fixed, and the stability of an optical system is improved.

2) The invention adopts the design of a deflection light path, and the laser beam passes through the atomic source glass bubble twice, thereby increasing the effective working length of the atomic source glass bubble, so that a strong spectrum signal can be obtained under the condition of shorter length of the atomic source glass bubble, being beneficial to shortening the length size of the whole optical system and meeting the miniaturization requirement.

3) The invention utilizes the characteristic that the trapezoidal prism is insensitive to the optical path offset, and simultaneously the angle processing precision between each surface of the trapezoidal prism can reach the arc second level, thereby improving the alignment precision of the whole optical path and greatly improving the stability of the frequency discrimination signal generated by the whole frequency stabilizer.

4) The cat eye reflector is insensitive to wedge-shaped optical elements (or wedge-shaped distortion generated by the elements) in the saturated absorption light path, and the saturated absorption spectrum frequency stabilization optical system can still work normally without readjusting a plano-concave mirror in the cat eye reflector under the condition that the wedge angle of the optical wedge is not large; the optical wedge inserted in the optical path causes the angular deflection of the output light beam and the linear displacement on the plano-concave mirror to be in direct proportion to the distance between the optical wedge and the cat eye reflector, and as long as the position of the atomic source glass bubble is close to the cat eye reflector as far as possible, the angular deflection of the output light beam and the linear displacement on the plano-concave mirror can not obviously influence the saturated absorption spectrum signal, so that the fluctuation of the saturated absorption spectrum signal caused by the thermal disturbance of the atomic source glass bubble is greatly reduced, the process requirement on the manufacturing of the atomic source glass bubble is reduced, and the stability of the frequency discrimination signal generated by the whole frequency stabilizer can be improved.

5) The cat-eye reflector in the invention is composed of a convex lens and a plano-concave mirror, and the cat-eye effect of the cat-eye reflector enables the cat-eye reflector to have good reverse parallel reflectivity: a beam of light returns along the original path when being incident normally along the optical axis of the cat-eye reflector; when the light beam obliquely enters the cat-eye reflector at a certain angle, if the principal ray of the incident light beam passes through the center of the convex lens, the reflected light beam still returns along the original path. When parallel light beams obliquely enter the cat eye reflector and the plane total reflector at the same angle, only the cat eye reflector can enable the light to return along the original path. Therefore, when the frequency stabilizing optical system of the saturated absorption spectrum is disturbed by machinery, heat and the like, the plane total reflection mirror is necessarily disturbed and deviates from the alignment state, the reflected light beam and the incident light beam are not strictly collinear any more, so that the saturated absorption spectrum signal is obviously weakened, and the influence can be eliminated or weakened when the cat eye reflector is adopted in the light path. When the cat-eye reflector is formed by the convex lens and the plane total reflection mirror, the reverse parallel reflectivity of the cat-eye reflector is obviously weaker than that of the cat-eye reflector adopting the convex lens and the plane total reflection mirror. This is because the mirror reflection effect of the plane mirror makes the cat eye reflector unable to fully compensate the angular deviation if the deviation of the incident angle is too large when the laser beam is obliquely incident, so that the reflected beam cannot fully return according to the original optical path, but the cat eye reflector using the convex lens and the concave mirror structure (where the focal length of the convex lens, the radius of curvature of the concave mirror and the distance between the two mirrors are equal) does not have the problem, and even if the light beam has a large incident inclination angle, the cat eye reflector can still compensate the light beam. Therefore, the cat eye reflector composed of the convex lens and the flat concave mirror is adopted by the saturated absorption spectrum frequency stabilization optical system, and the performance is better.

Drawings

Fig. 1 is a schematic diagram of a conventional saturated absorption spectrum frequency stabilization optical system.

Fig. 2 is a schematic diagram of an optical path structure of an embodiment of a frequency stabilizing optical system with a saturated absorption spectrum according to the present invention.

Fig. 3 is a schematic diagram of an optical path structure of another embodiment of the cat-eye reflector of the present invention.

Reference numbers in fig. 1:

100-incident linear polarization laser beam, 101-Polarization Beam Splitter (PBS), 102-quarter wave plate, 103-rotary mounting seat, 104-atomic source glass bulb, 105-0 degree total reflection mirror and 106-photoelectric detector.

Reference numbers in fig. 2:

200-linear polarization laser beam, 201-polarization beam splitter, 202-rotating mounting seat, 203-quarter wave plate, 204-atomic source glass bulb, 205-trapezoidal prism, 206-convex lens, 207-plano-concave mirror, 208-photoelectric detector, 210-cat eye reflector and 207B-plane total reflector.

Detailed Description

The present invention will be further described with reference to the following specific examples and drawings, but the scope of the present invention should not be limited thereto.

As shown in fig. 2, the single-beam saturated absorption spectrum frequency stabilizing optical system with a cat-eye reflector provided in the embodiment of the present invention includes a polarizing beam splitter 201, a quarter-wave plate 203, an atomic source glass bubble 204, and a trapezoidal prism 205, which are sequentially disposed on the same optical axis; a cat-eye reflector 210 is arranged on a reflection light path of the trapezoidal prism 205; a photoelectric detector 208 is arranged on a reflected light path of the polarization beam splitter 201; the atomic source glass bubble 204 is also located on the reflection light path of the trapezoidal prism 205 and between the trapezoidal prism 205 and the cat-eye reflector 210.

The cat-eye reflector 210 is composed of a convex lens 206 and a plano-concave mirror 207, and the concave surface of the plano-concave mirror 207 is opposite to the convex lens 206; the focal length of the convex lens 206, the concave curvature radius of the plano-concave mirror 207 and the distance between the convex lens 206 and the plano-concave mirror 207 are equal. The convex lens 206 and the plano-concave mirror 207 are arranged on the same base, the distance between the convex lens 206 and the plano-concave mirror 207 can be adjusted so as to be convenient for assembly, and the convex lens and the plano-concave mirror can be locked by using locking holes after being assembled and adjusted. The "cat-eye effect" of the cat-eye reflector 210 makes it well antiparallel reflective to light beams: light rays return along the original path when being incident normally along the axis of the cat-eye reflector 210; when the light beam is obliquely incident on the cat-eye reflector 210 at an angle, if the principal ray of the incident light beam passes through the center of the convex lens 206, the reflected light beam still returns along the original path. This is not available with conventional flat mirrors. The invention utilizes the cat-eye reflector 210 as a reflector, and the antiparallel reflectivity of the cat-eye reflector is greatly helpful for improving the stability of the frequency stabilization optical system. When the saturated absorption spectrum frequency stabilization optical system is disturbed by machinery, heat and the like, the reflector is necessarily disturbed and deviates from an alignment state, but when the cat eye reflector is used as the reflector, the influence can be eliminated or weakened, so that the saturated absorption spectrum frequency stabilization optical system still works normally. In other embodiments, the cat-eye reflector 210 may also be composed of a convex lens 206 and a planar holophote 207B, and a reflection surface of the planar holophote 207B is opposite to the convex lens 206; the distance from the reflection surface of the planar total reflecting mirror 207B to the convex lens 206 is equal to the focal length of the convex lens 206, as shown in fig. 3.

A quarter wave plate 203 is provided on the rotating mount 202 with a locking mechanism.

The two isosceles side surfaces of the trapezoidal prism 205 form an angle of 45 ° with the lower bottom surface.

The lower bottom surface of the trapezoidal prism 205, the front and rear light-passing surfaces of the quarter-wave plate 203 and the two light-passing surfaces of the convex lens 206 are all plated with antireflection films corresponding to the wavelength of the passing laser.

The surfaces of the two isosceles sides of the trapezoidal prism 205 and the concave surface of the plano-concave mirror 207 are coated with a reflective film corresponding to the wavelength of the reflected laser light.

All the optical elements and the mounting seats thereof are mounted on an optical base, and the optical element mounting seats are designed and processed according to the optical center height of the whole optical path and meet the optical design requirements. The optical planes of all the optical elements are parallel to each other and the optical centers are uniform in height.

The principle of the invention is as follows:

the polarization direction of the incident linearly polarized laser beam 200 is the same as the transmission polarization axis of the polarization beam splitter 201, the linearly polarized laser beam 200 is transmitted by the polarization beam splitter 201, then is changed into a circularly polarized laser beam through the quarter-wave plate 202, then passes through the atomic source glass bubble 204, is reflected by two inclined planes of the trapezoidal prism 205, passes through the atomic source glass bubble 204 again, reaches the cat eye reflector 210, is reflected by the cat eye reflector 210 and returns in the original path, passes through the quarter-wave plate 202 again, is changed into a linearly polarized laser beam, rotates by 90 degrees in the polarization direction, and finally is reflected to the photodetector 208 through the polarization beam splitter 201. The photodetector 208 converts the received optical signal into an electrical signal that is subsequently processed by electronic circuitry as disclosed in the prior art to obtain a frequency discrimination signal for laser stabilization.

From the above principle, the light beam passes through the atom source glass bubble 204 twice in the present invention, so the length of the atom source glass bubble 204 in the present invention can be reduced to half of the length of the atom source glass bubble in the existing optical system.

In other embodiments, if the length of the whole optical system does not need to be shortened, the trapezoidal prism 205 can be omitted, and the cat-eye reflector 210 is placed on the emergent light path of the atom source glass bubble 204, i.e. the emergent light beam of the atom source glass bubble 204 is directly received and reflected by the cat-eye reflector 210.