Intracavity element-free high-frequency stability compact frequency stabilized laser

Abstract

The invention discloses an intracavity element-free high-frequency stability compact frequency-stabilized laser, which is characterized in that three sections of capillary tubes, namely a first capillary tube, a second capillary tube and a third capillary tube, are arranged on a microcrystalline glass block; the first capillary tube is located at the top, one end of the first capillary tube is communicated with the second capillary tube, a planar high-reflection sheet is arranged at the corresponding position of the microcrystalline glass block at the communication position, and the other end of the second capillary tube is communicated with the slotted sheet; the other end part of the first capillary tube is communicated with a third capillary tube, a frequency-stabilized optical detector is arranged at a corresponding position on the microcrystalline glass block at the communication part, and the other end of the third capillary tube is communicated with a planar output sheet; the slotted vane and the planar output piece form an optical resonant cavity; the capillary tube is filled with He-Ne gas, and high voltage is applied between the cathode and the anode to excite the gas to discharge; the getter is placed in a top end groove of the glass ceramic block; and the piezoelectric ceramic is arranged on the slotted vane. The invention has the advantages of simple and compact structure, convenience in processing, good applicability, high reliability and the like.

Description

Technical Field

[0001] The present invention mainly relates to the technical field of high-precision measuring equipment, and in particular to a high-frequency, compact, high-frequency, stable, and compact frequency-stabilized laser without intracavity components. Background Art

[0002] Lasers have good directivity, concentrated energy, and stable wavelength, making them the preferred benchmark in the field of precision length measurement. The output wavelength of a laser is affected by the laser generating medium and the length of the laser. In the field of extremely high-precision length measurement technology, temperature changes in the laser working medium or slight changes in the laser length will cause changes in the laser output wavelength, thus affecting the results of precision measurement.

[0003] By measuring the changes in laser parameters caused by changes in laser wavelength, such as light intensity, or the saturated absorption spectrum of another medium, and dynamically changing the length of the laser, the wavelength of the laser can be stabilized near a fixed value, which can improve the wavelength stability of the laser. The wavelength of light multiplied by the frequency equals the speed of light, and the speed of light is constant, so stabilizing the wavelength of the laser is equivalent to stabilizing the frequency of the laser. Lasers that work based on this mechanism are called "frequency-stabilized lasers."

[0004] Therefore, in the current specific application of high-precision length measurement technology, frequency-stabilized lasers are an important component. The frequency stability of frequency-stabilized lasers is the key to affecting measurement accuracy. In actual industrial applications, the start-up time, size, environmental adaptability, simple structure and easy production of frequency-stabilized lasers are all very important features.

[0005] like Figure 1 As shown, it is a schematic diagram of the structural principle of an existing typical frequency-stabilized laser. The frequency-stabilized laser includes a glass tube 1 and a capillary 2, in which He gas and Ne gas of a certain pressure and ratio are enclosed. When a high voltage is applied between the first anode 3 and the first cathode 4, the He-Ne gas will produce a glow. Under the selection of the resonant cavity composed of the first plane mirror 5 and the concave mirror 6, only light of a specific frequency can produce a stable laser, and a laser output is generated at the end of the first plane mirror 5. The intensity of the output laser is detected by a photodetector 7, and the first piezoelectric ceramic 8 is controlled to extend and shorten with a specific strategy, thereby changing the length of the resonant cavity, and finally stabilizing the frequency of the output laser within a certain range. In this structure, the Brewster window 9 only allows the laser of a specific polarization direction to exist, thereby obtaining a linearly polarized light output.

[0006] Based on the above typical structure, different components for measuring laser parameters can also be added to the laser to obtain the wavelength / frequency information of the laser. For example, a frequency-stabilized laser that measures the wavelength of the laser through the saturated absorption spectrum of iodine vapor is an iodine-stabilized laser. In addition to the first piezoelectric ceramic 8 in the figure, the method for controlling the length of the laser cavity can also be to heat the laser tube and control the temperature of the laser tube, thereby changing the length of the laser cavity. This frequency-stabilized laser is called a "thermal frequency-stabilized laser".

[0007] It can be seen from the above-mentioned traditional typical structure that the prior art has the following technical deficiencies: 1. The straight tube laser is longer, larger in size, and has a more complex internal structure.

[0008] 2. The straight tube laser using quartz glass tube has poor mechanical and thermal stability of the resonant cavity, and it is difficult to work stably under vibration and high and low temperature environments, making it difficult to adapt to outdoor or large temperature change and vibration application environments.

[0009] 3. Iodine-stabilized laser. Although iodine vapor has high accuracy in measuring laser wavelength, its environmental stability is poor. Therefore, iodine-stabilized laser is suitable as a standard stabilized laser in the laboratory, but it is not suitable for working outdoors or in harsh environments.

[0010] 4. Thermally stabilized lasers need to heat the resonant cavity to change the length of the cavity, so their temperature change response speed is slow. When the ambient temperature changes, it is easy to lose the locking function. Summary of the invention

[0011] The technical problem to be solved by the present invention is: in view of the technical problems existing in the prior art, the present invention provides a compact frequency-stabilized laser with high frequency stability and no intra-cavity components, which has a simple and compact structure, is easy to process, has good applicability and high reliability.

[0012] In order to solve the above technical problems, the present invention adopts the following technical solutions: A compact frequency-stabilized laser with high frequency stability and no intracavity components, comprising a microcrystalline glass block, a frequency-stabilized light detector, a planar output plate, a planar high-reflection plate, a getter, a piezoelectric ceramic, a cathode and an anode; three sections of capillaries are provided on the microcrystalline glass block, namely a first capillary, a second capillary and a third capillary; the first capillary is located at the top, one end of the first capillary is connected to the second capillary, a planar high-reflection plate is provided at a corresponding position on the microcrystalline glass block at the connection point, and the other end of the second capillary is connected to a slot plate; The other end of the first capillary is connected to the third capillary, and a frequency-stabilized light detector is provided at a corresponding position on the microcrystalline glass block at the connection point, and the other end of the third capillary is connected to the plane output plate; The groove plate and the flat output plate form an optical resonant cavity; the capillary is filled with He-Ne gas, a high voltage is applied between the cathode and the anode to stimulate gas discharge, and under the action of the resonant cavity, laser is generated through stimulated radiation; The getter is placed in the top groove of the microcrystalline glass block; the piezoelectric ceramic is arranged on the groove sheet.

[0013] As a further improvement of the present invention: the piezoelectric ceramic is fixed on the slot sheet by means of a gripper.

[0014] As a further improvement of the present invention: a tiny sinusoidal jitter signal is applied to the piezoelectric ceramic, and the elongation or shortening of the reflective surface of the slot is changed by applying a force against the center of the slot, thereby controlling the elongation or shortening of the piezoelectric ceramic and maintaining the length of the optical resonant cavity at a stable level.

[0015] As a further improvement of the present invention: the incident end of the frequency-stabilizing light detector is provided with a frequency-stabilizing light plane output plate, the frequency-stabilizing light plane output plate has optical transmittance, the transmitted laser hits the frequency-stabilizing light detector, and the output of the frequency-stabilizing light detector is used as a reference signal for frequency stabilization.

[0016] As a further improvement of the present invention: the getter is covered and protected by a getter protection sheet.

[0017] As a further improvement of the present invention: the reflecting surface of the slot sheet is a concave surface, and the other three reflecting surfaces are flat surfaces.

[0018] As a further improvement of the present invention: the slotted sheet adopts a high-reflection lens, the flat output sheet outputs a small portion of the light, and reflects most of the light back to the light path.

[0019] As a further improvement of the present invention: the glass-ceramic block is formed by an optical cold working process.

[0020] As a further improvement of the present invention: three sections of capillaries are processed on the microcrystalline glass block by drilling technology.

[0021] As a further improvement of the present invention: the top of the microcrystalline glass block is drilled downward to communicate with the first capillary located at the top; the capillary outlet end face and the top are super-polished to a surface roughness level less than nm to prepare for photoresist.

[0022] Compared with the prior art, the present invention has the following beneficial effects: 1. The compact frequency-stabilized laser with high frequency stability and no intracavity components of the present invention has a simple structure, convenient processing, good applicability and high reliability. The present invention maintains a relatively high frequency stability and meets most measurement accuracy requirements. The frequency-stabilized laser has a short start-up time, a small size, a simple structure, and is easy to produce. It has high environmental adaptability and can output a high-reliability stable light source frequency under complex environments such as temperature difference, shock, vibration, and long time. It solves the problems of existing frequency-stabilized lasers being large in size and being affected by temperature, vibration, long test time, low heating efficiency, and poor dynamic performance, and has good industrial application characteristics.

[0023] 2. The compact frequency-stabilized laser with high frequency stability and no intracavity components of the present invention is a frequency-stabilized laser with high-precision frequency stability, and can work normally under vibration, a large temperature range, and large temperature change conditions. It is small in size, light in weight, and easy to install and use inside the system.

[0024] 3. The high frequency stability compact frequency-stabilized laser without intracavity components of the present invention is processed as a whole on a piece of microcrystalline glass, so the structure is stable and can withstand certain environmental vibrations and remain stable. Microcrystalline glass has an extremely low thermal expansion coefficient, so that the frequency-stabilized laser of the present invention has good temperature stability, can meet the working requirements of a larger temperature range, and can maintain the frequency stability of the output laser under certain temperature change conditions.

[0025] 4. The high-frequency stability compact frequency-stabilized laser without intracavity components of the present invention is a folded optical path, so it has the characteristics of short length, small volume and compact structure. The frequency-stabilized laser provided by the present invention directly utilizes the coating process of folded reflection, so that the two orthogonal directions have different losses, thereby directly outputting linearly polarized light, eliminating the Brewster window in the cavity, so that the frequency-stabilized laser has a simple structure and is easy to process and produce in batches.

[0026] 5. The compact frequency-stabilized laser with high frequency stability and no intracavity components of the present invention adopts a small-jitter Lamb dip frequency stabilization method, does not rely on external special media, and has high working stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the structural principle of an existing frequency-stabilized laser.

[0028] Figure 2 It is a schematic diagram of the structural principle of a specific embodiment of the present invention from a viewing angle.

[0029] Figure 3 It is a schematic diagram of the structural principle of the present invention in another perspective in a specific embodiment.

[0030] Figure 4 It is a schematic diagram of the relationship between the intensity variation law of the output laser and the applied tiny sinusoidal jitter signal in a specific embodiment of the present invention; wherein (a) is a diagram showing the relationship between the intensity variation law of the output laser detected by the frequency-stabilized optical detector when the laser output frequency is at the Lamb dip frequency point and the applied tiny sinusoidal jitter signal; (b) is a diagram showing the relationship between the intensity variation law of the output laser and the applied tiny sinusoidal jitter signal when the laser output frequency is less than the Lamb dip frequency; (c) is a diagram showing the relationship between the intensity variation law of the output laser and the applied tiny sinusoidal jitter signal when the laser output frequency is greater than the Lamb dip frequency.

[0031] Legend: 1. Glass tube; 2. Capillary; 3. First anode; 4. First cathode; 5. First plane mirror; 6. Concave mirror; 7. Photodetector; 8. First piezoelectric ceramic; 9. Brewster window; 100. Plane high reflective film; 110. Anode; 111. Cathode; 200. Groove; 300. Grab card; 400. Getter; 500. Frequency-stabilized photodetector; 600. Frequency-stabilized light plane output film; 700. Microcrystalline glass block; 121. First capillary; 122. Second capillary; 123. Third capillary; 800. Plane output film; 900. Piezoelectric ceramic; 130. Getter protection film. DETAILED DESCRIPTION

[0032] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0033] In the description of the present invention, it should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0034] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0035] In the present invention, unless otherwise clearly specified and limited, the terms "assemble", "connect", "connect", "fix" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0036] In the description of the present invention, S-polarized light and P-polarized light refer to the following: when light penetrates the surface of an optical element (such as a beam splitter) at a non-perpendicular angle, both the reflection and transmission characteristics depend on polarization phenomena. In this case, the coordinate system used is defined by the plane containing the input and reflected light beams. If the polarization vector of the light is in this plane, it is called P polarization; if the polarization vector is perpendicular to the plane, it is called S polarization. The laser used for laser interferometry to measure length is linearly polarized light, which can improve the sharpness of the interference fringes, thereby obtaining a higher degree of length measurement accuracy.

[0037] In the description of the present invention, Lamb dip means that in a Doppler broadened single longitudinal mode gas laser, the output power always increases as the longitudinal mode frequency approaches the center frequency, but when the longitudinal mode frequency approaches the center frequency, the number of particles that can be stimulated to radiate decreases due to the overlap of two hole burning on the gain curve, so the light intensity decreases instead, and a dip appears at the center frequency. This effect is named after the person "Lamb" who discovered it.

[0038] like Figures 2 to 3 As shown, the compact frequency-stabilized laser with high frequency stability and no intracavity components of the present invention comprises a microcrystalline glass block 700, a frequency-stabilized light detector 500, a planar output plate 800, a planar high-reflection plate 100, a getter 400, a piezoelectric ceramic 900, a cathode 111 and an anode 110; The microcrystalline glass block 700 is provided with three capillaries, namely the first capillary 121, the second capillary 122 and the third capillary 123; the first capillary 121 is located at the top, one end of the first capillary 121 is connected with the second capillary 122, a plane high reflective sheet 100 is provided at the corresponding position of the microcrystalline glass block 700 at the connection point, and the other end of the second capillary 122 is connected with the groove sheet 200; The other end of the first capillary 121 is connected to the third capillary 123, and a frequency-stabilized light detector 500 is provided at a corresponding position on the microcrystalline glass block 700 at the connection point. The other end of the third capillary 123 is connected to the plane output plate 800; The slot plate 200 and the flat output plate 800 form an optical resonant cavity; the capillary is filled with He-Ne gas. A high voltage is applied between the cathode 111 and the anode 110 to stimulate gas discharge, and under the action of the resonant cavity, laser is generated through stimulated radiation.

[0039] In a specific application example, the slot plate 200 uses a high-reflection lens, and the flat output plate 800 outputs a small portion of light and reflects most of the light back into the optical path.

[0040] In a specific application example, the piezoelectric ceramic 900 is fixed on the slot sheet 200 by the gripper 300, and the elongation or shortening of the reflective surface of the slot sheet 200 is changed by applying a force against the center of the slot sheet 200.

[0041] In a specific application example, the present invention can achieve the purpose of stabilizing the high voltage current and balancing the two arms by controlling the current of the two anodes 110 .

[0042] In a specific application example, the reflective surface of the slot sheet 200 is a concave surface, and the other three reflective surfaces are flat surfaces.

[0043] In a specific application example, the plane high reflective sheet 100 has a high reflectivity. By controlling the reflective ratio of the plane high reflective sheet 100 to S light and P light, the S light is transformed into laser light and the P light is suppressed, thereby obtaining linearly polarized light output.

[0044] In a specific application example, a frequency-stabilizing light plane output plate 600 is provided at the incident end of the frequency-stabilizing light detector 500. The frequency-stabilizing light plane output plate 600 has a small optical transmittance. The transmitted laser hits the frequency-stabilizing light detector 500, and the output of the frequency-stabilizing light detector 500 is used as a reference signal for frequency stabilization.

[0045] In a specific application example, the getter 400 is placed in the top groove of the microcrystalline glass block 700 and is covered and protected by the getter protection sheet 130 .

[0046] In a specific application example, the glass-ceramic block 700 is formed by an optical cold working process.

[0047] In a specific application example, three sections of capillaries are processed on the microcrystalline glass block 700 by drilling technology.

[0048] In a specific application example, a hole is drilled downward at the top of the microcrystalline glass block 700 to communicate with the first capillary 121 at the top. Then, the capillary outlet end face and the top are super-polished to a surface roughness of less than nm to prepare for photoresist.

[0049] In a specific application example, a tiny sinusoidal jitter signal is applied to the piezoelectric ceramic 900. According to the laser Lamb dip frequency stabilization principle, if the laser output frequency is at the Lamb dip frequency point, the relationship between the intensity variation of the output laser detected by the frequency stabilization optical detector 500 and the tiny sinusoidal jitter signal applied is as follows: Figure 4 (a) If the laser output frequency is less than the Lamb dip frequency, the relationship between the intensity variation of the output laser and the applied tiny sinusoidal jitter signal is as follows: Figure 4 (b) If the laser output frequency is greater than the Lamb dip frequency, the relationship between the intensity variation of the output laser and the applied tiny sinusoidal jitter signal is as follows: Figure 4 (c) As shown in each figure, the black line is the jitter driving signal, and the other color lines are the intensity change curves of the output laser under the corresponding conditions. According to the relationship between the intensity change law of the output laser and the applied small sinusoidal jitter signal, the piezoelectric ceramic 900 is controlled to extend or shorten, and the length of the optical resonant cavity is maintained at a stable level, thereby achieving frequency stability of the output laser.

[0050] By adopting the above structure of the present invention, the entire laser is made of a whole piece of microcrystalline glass block 700. Each reflector is attached to the corresponding surface of the microcrystalline glass block 700 by optical glue process. The laser resonant cavity generates linear polarized light through the different losses of S light and P light of the plane high reflective film 100, and there is no intra-cavity optical element.

[0051] In the above structure of the present invention, a folded cavity design is adopted, that is, compared with the traditional technology, a straight cavity is designed into a turning structure. Obviously, under the condition of the same internal optical path length, the length of the folded cavity is shorter and the structure is more compact. Therefore, under the same material and temperature change conditions, the stability of the folded cavity is better. This is because the thermal expansion characteristic of the material is that the longer the structure, the greater the expansion and contraction amount for the same temperature change. However, the advantages of the folded cavity are more than that. In order to realize the folded cavity, two reflectors are required, and the reflectors are placed at 45 degrees. This makes it possible to design the reflective film system of the reflector to allow only the laser in one polarization direction to have a higher reflectivity, so that the reflected light becomes linearly polarized light. The non-folded cavity requires additional components to be added inside or outside the cavity to generate polarized light, so the folded cavity reduces the number of components, thereby reducing unstable factors, making the laser more reliable and stable. In addition, such a structure is obviously easier to assemble and produce than installing components inside and outside the cavity.

[0052] Therefore, the reason why the compact frequency-stabilized laser with high frequency stability and no intracavity components can achieve high reliability and strong environmental adaptability (anti-interference) is due to the three advantages of the above-mentioned folded cavity. First, the size is shortened and more compact. Second, no intracavity optical components are used, which reduces unstable factors. Third, it is easy to assemble and produce. In addition to the above factors, the laser uses microcrystalline glass with a coefficient of expansion close to zero, which is also the main factor in further increasing the thermal stability and structural stability of the laser. This laser also uses piezoelectric ceramics 900 fixed on the slot 200 through a gripper 300. By applying a force on the center of the slot 200 to change the elongation or shortening of the reflective surface of the slot 200, the length of the laser resonant cavity is further actively and accurately controlled, thereby achieving high frequency stability.

[0053] The above are only preferred embodiments of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should be regarded as the protection scope of the present invention.

Claims

1. A compact frequency-stabilized laser with high frequency stability and no intracavity components, characterized in that: It comprises a microcrystalline glass block, a frequency-stabilized light detector, a plane output sheet, a plane high-reflection sheet, a getter, a piezoelectric ceramic, a cathode and an anode; the microcrystalline glass block is provided with three sections of capillaries, namely a first capillary, a second capillary and a third capillary; the first capillary is located at the top, one end of the first capillary is connected with the second capillary, a plane high-reflection sheet is provided at a corresponding position on the microcrystalline glass block at the connection point, and the other end of the second capillary is connected with the groove sheet; The other end of the first capillary is connected to the third capillary, and a frequency-stabilized light detector is provided at a corresponding position on the microcrystalline glass block at the connection point, and the other end of the third capillary is connected to the plane output plate; The groove plate and the flat output plate form an optical resonant cavity; the capillary is filled with He-Ne gas, a high voltage is applied between the cathode and the anode to stimulate gas discharge, and under the action of the resonant cavity, laser is generated through stimulated radiation; The getter is placed in the top groove of the microcrystalline glass block; the piezoelectric ceramic is arranged on the groove sheet.

2. The compact frequency-stabilized laser with high frequency stability and no intracavity components according to claim 1, characterized in that: The piezoelectric ceramic is fixed on the slot plate by means of a gripper.

3. The compact frequency-stabilized laser with high frequency stability and no intracavity components according to claim 2, characterized in that: A tiny sinusoidal jitter signal is applied to the piezoelectric ceramic, and the elongation or shortening of the reflective surface of the slot is changed by applying a force against the center of the slot, thereby controlling the elongation or shortening of the piezoelectric ceramic and maintaining the length of the optical resonant cavity at a stable level.

4. The compact frequency-stabilized laser with high frequency stability and no intracavity components according to claim 1, characterized in that: The incident end of the frequency-stabilizing optical detector is provided with a frequency-stabilizing optical plane output plate, which has optical transmittance. The transmitted laser hits the frequency-stabilizing optical detector, and the output of the frequency-stabilizing optical detector is used as a reference signal for frequency stabilization.

5. The compact frequency-stabilized laser with high frequency stability and no intracavity components according to claim 1, characterized in that: The getter is covered and protected by a getter protection sheet.

6. The compact frequency-stabilized laser with high frequency stability and no intracavity components according to any one of claims 1 to 5, characterized in that: The reflecting surface of the slot sheet is a concave surface, and the other three reflecting surfaces are flat surfaces.

7. The compact frequency-stabilized laser with high frequency stability and no intracavity components according to claim 6, characterized in that: The slot plate adopts a high-reflection lens, and the flat output plate outputs a small part of the light and reflects most of the light back to the light path.

8. The compact frequency-stabilized laser with high frequency stability and no intracavity components according to any one of claims 1 to 5, characterized in that: The microcrystalline glass block is formed by an optical cold working process.

9. The compact frequency-stabilized laser with high frequency stability and no intracavity components according to claim 8, characterized in that: Three sections of capillaries are processed on the microcrystalline glass block through a drilling process.

10. The compact frequency-stabilized laser with high frequency stability and no intracavity components according to claim 8, characterized in that: The top of the microcrystalline glass block is drilled downward to communicate with the first capillary located at the top; the outlet end face of the capillary and the top are polished to prepare for light glue.

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