CN219532452U - Laser crystal thermal lens focal length measuring device - Google Patents
Laser crystal thermal lens focal length measuring device Download PDFInfo
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- CN219532452U CN219532452U CN202320298462.0U CN202320298462U CN219532452U CN 219532452 U CN219532452 U CN 219532452U CN 202320298462 U CN202320298462 U CN 202320298462U CN 219532452 U CN219532452 U CN 219532452U
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Abstract
The utility model relates to a laser crystal thermal lens focal length measuring device which comprises a detection light source, a pumping source, a laser crystal, a coupling system and a CCD camera, wherein the detection light source is used for emitting detection light beams and entering the laser crystal, the pumping source is used for emitting pumping light with different powers and entering the laser crystal after passing through the coupling system, and the CCD camera is used for measuring the focal point of the detection light beams emitted from the laser crystal. The utility model can realize the rapid and accurate measurement of the thermal lens focal length of the laser crystal under different pump injection powers.
Description
Technical Field
The utility model relates to the technical field of optical communication, in particular to a laser crystal thermal lens focal length measuring device.
Background
There are many methods for measuring thermal lenses, and there are probe beam methods, critical cavity methods, and the like. The method is to measure the focal position of HE-Ne laser through crystal rod to determine the focal length of the thermal lens, because the HE-Ne laser has small spot, the Rayleigh distance is long after focusing by the laser crystal, the focal position is not good, so the error of the measurement result is large, moreover, the HE-Ne laser does not participate in the radiation process of the laser crystal, even if the focal position can be found accurately, the measured thermal focal length is still different from the thermal focal length actually formed. The critical cavity method utilizes the focal length of the thermal lens as a function of the distance between the output mirror in the critical cavity and the laser crystal, finds the critical point of changing the resonant stable cavity into the unstable cavity by changing the distance between the output mirror in the resonant cavity and the laser crystal under certain pumping power, and calculates the focal length of the thermal lens of the laser crystal according to the relative distance. In the actual measurement process, because the position of the resonant cavity output mirror is changed, the resonant cavity is debugged once every time the position of the resonant cavity output mirror is changed, the process is tedious, and the influence of the stimulated radiation process on the focal length of the laser crystal thermal lens is not considered, so that the measurement result is still different from the actual situation.
Disclosure of Invention
The utility model aims to provide a laser crystal thermal lens focal length measuring device which at least can solve part of defects in the prior art.
In order to achieve the above object, the embodiment of the present utility model provides the following technical solutions: a laser crystal thermal lens focal length measuring device comprises a detection light source, a pumping source, a laser crystal, a coupling system and a CCD camera,
the detection light source is used for emitting detection light beams and entering the laser crystal,
the pumping source is used for emitting pumping light with different powers and entering the laser crystal after passing through the coupling system,
the CCD camera is used for measuring the focus of the detection light beam emitted from the laser crystal.
Further, a first spectroscope is arranged on the light path between the detection light source and the laser crystal.
Further, a light absorption barrel is arranged on the reflection light path of the first spectroscope.
Further, a matching mirror is arranged on the light path between the detection light source and the laser crystal.
Further, the coupling system comprises a first coupling mirror and a second coupling mirror, and the first coupling mirror and the second coupling mirror are sequentially arranged on the light path of the emergent pumping light.
Further, a second beam splitter is further arranged on the light path between the laser crystal and the coupling system.
Further, an attenuation component is arranged on the reflection light path of the second beam splitter, and the detection light beam emitted from the laser crystal enters the CCD camera after being reflected by the second beam splitter and attenuated by the attenuation component.
Further, the attenuation component comprises a first beam splitting prism and a second beam splitting prism, and the detection light beam sequentially passes through the first beam splitting prism and the second beam splitting prism.
Further, the attenuation component further comprises an attenuator, and the detection light beam passing through the second beam splitting prism enters the attenuator.
Further, the CCD camera is arranged on an electric sliding table with a grating ruler.
Compared with the prior art, the utility model has the beneficial effects that: the method can realize quick and accurate measurement of the thermal lens focal length of the laser crystal under different pump injection powers.
Drawings
FIG. 1 is a schematic diagram of an end-pumped laser crystal thermal lens focal length measuring device according to an embodiment of the present utility model;
in the reference numerals: 1-a first spectroscope; 2-a second beam splitter; 3-a light absorption cylinder; 4-laser crystal; a 5-attenuator; a 6-CCD camera; 7-matching mirrors; 8-a first coupling mirror; 9-a second coupling mirror; 10-a first mirror; 11-a first light splitting prism; 12-a second light splitting prism; 13-a focusing mirror; 14-a second mirror; 15-a third mirror; 16-an electric slipway; a-detecting a light source; b-pump source.
Detailed Description
The following description of the embodiments of the present utility model will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present utility model, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the utility model without making any inventive effort, are intended to be within the scope of the utility model.
Embodiment one:
referring to fig. 1, an embodiment of the utility model provides a method for measuring a focal length of an end-pumped laser crystal thermal lens, which includes fixing a position of a detection light source a, temporarily placing a first focusing lens at a certain position on the right of the detection light source a, and determining the focal length as f 1 The CCD camera 6 is used for measuring the size of the focus and the position of the focus of the detection light emitted by the detection light source A after being focused by the first focusing mirror, and the size and the position are respectively marked as w' 0 、l' 0 . And then according to the formula:
calculating the beam waist size and the beam waist position of the detection light, and marking as w 0 、l 0 。
Then the first focusing lens is taken down, the matching lens is placed at a certain position on the right side of the detection light source A, and the focal length is marked as f 2 The beam waist position of the detection light beam emitted by the detection light source A is located near the front end face of the laser crystal 4 after the beam conversion of the detection light beam by the matching mirror, and the distance from the position of the matching mirror to the beam waist position of the detection light is calculated and marked as l 01 The method comprises the steps of carrying out a first treatment on the surface of the And then according to the formula:
calculating the beam waist size and the beam waist position of the detection light passing through the matching mirror, and marking the detection light as w 1 、l 1 The method comprises the steps of carrying out a first treatment on the surface of the Then the distance between the beam waist position of the detection light passing through the matching mirror and the left end face position of the laser crystal 4 is calculated, and is marked as l 11 。
Then fixing the pump source B at a good position, and placing a first coupling lens in the coupling system at a certain position behind the pump source B so that pump light emitted by the pump source B is collimated by the first coupling lens; the second coupling lens in the coupling system is arranged at a certain position behind the first coupling lens, so that the pump light collimated by the first coupling lens is reflected and focused near the left end face of the laser crystal 4 through the first spectroscope 1. Preferably, the focal length of the first coupling lens is determined by the numerical aperture of the pump source B, and the focal length of the second coupling lens is determined by the matching of the spot sizes of the probe light and the pump light in the laser crystal 4.
Then, setting the input currents of the pump source B as A1, A2, A3, A4 and A5, and measuring the output powers of the pump source B as P1, P2, P3, P4 and P5 under the input currents by using a power meter.
Then the second beam splitter 2 is placed near the rear end face of the laser crystal 4, the second condenser Jiao Jingfang is placed at a certain position behind the second beam splitter 2, the position of the second condenser is moved to focus the probe beam emitted from the laser crystal 4, and the beam waist size and the beam waist position of the probe beam focused by the second condenser are measured by using a CCD and marked as w 2 、l 2 . According to the formula:
the beam waist position and the beam waist size of the probe light with amplified power emitted from the laser crystal 4 are calculated and marked as l' 1 、w' 1 . And then according to the formula:
finally, the thermal focal length f of the laser crystal 4 is calculated T 。
The following are specific examples:
fixing the position of the detection light source A, temporarily placing a first focusing mirror at the position 460mm on the right side of the detection light source A to focus the detection light through the first focusing mirror, and focusing the detection light by the first focusing mirror with a focal length f 1 The size of the focal point and the position of the focal point after focusing the probe light emitted from the probe light source a by the first focusing mirror are measured using the CCD camera 6, and are marked as w' 0、 l' 0 . The measurement results are: w' 0 ＝0.388mm、l' 0 =60 mm. According to the formula:
calculating the beam waist size and the beam waist position of the detection light, and marking as w 0 、l 0 . Calculating to obtain w 0 ＝0.2171mm、l′ 0 ＝24.7193mm。
The first focusing lens is removed, and as shown in FIG. 1, the matching lens is placed at 440mm right of the detection light source A, and the focal length is marked as f 2 ，f 2 The laser crystal 4 is arranged at the right 15mm position of the matching mirror, so that the beam waist position of the detection beam emitted by the detection light source A falls on the laser crystal after the beam conversion of the detection light source A by the matching mirror4, calculating the distance from the position of the matching mirror to the beam waist position of the detection light, and marking as l 01 . Calculated l 01 =460-24.7193-440= -4.7mm. And then according to the formula:
calculating the beam waist size and the beam waist position of the detection light passing through the matching mirror, and marking the detection light as w 1 、l 1 Calculated w 1 ＝0.1757mm、l 1 ＝66.2634。
Then the distance between the beam waist position of the detection light passing through the matching mirror and the left end face position of the laser crystal 4 is calculated, and is marked as l 11 ，l 11 ＝15-66.2634＝-51.2634mm。
The output optical fiber core diameter of the pump source B is 400um, and the numerical aperture is 0.22. Fixing the pump source B at a good position, placing a first coupling lens in a coupling system with a focal length of 20mm at a certain position behind the pump source B, and collimating pump light emitted by the pump source B by the first coupling lens 8; the second coupling lens in the coupling system is arranged at a certain position behind the first coupling lens 8, so that the pump light collimated by the first coupling lens 8 is transmitted and focused near the right end face of the laser crystal 4 through the second spectroscope 2, and the pump light which is absorbed is reflected to the light absorption barrel 3 by the first spectroscope 1.
The input currents of the pump source B are respectively 2A, 4A, 6A, 8A, 10A and 12A, and the output powers of the pump source B under the input currents are respectively P1, P2, P3, P4 and P5 by using a power meter.
The second beam splitter 2 is arranged near the right end face of the laser crystal 4, the second beam splitter Jiao Jingfang is arranged at a certain position behind the second beam splitter 2 and is 635mm away from the left end face of the laser crystal 4, and the focal length is marked as f 3 ，f 3 200mm, the probe beam emitted from the laser crystal 4 is focused by a second focusing mirror and measured by a CCD camera 6Measuring the beam waist size and the beam waist position of the probe light focused by the focusing lens, and marking the beam waist size and the beam waist position as w 2 、l 2 . And then according to the formula:
the beam waist position and the beam waist size of the probe light with amplified power emitted from the laser crystal 4 are calculated and marked as l' 1 、w' 1 . And then according to the formula:
finally, the thermal focal length f of the laser crystal 4 is calculated T 。
TABLE 1
Table 1 above shows w corresponding to different currents, pump powers and absorption efficiencies 2 、l 2 、l' 1 、w' 1 、f T Is a value of (2).
Embodiment two:
referring to fig. 1 in combination with the above measurement method, an embodiment of the present utility model provides a laser crystal thermal lens focal length measurement device, and specifically includes a probe light source a, a pump source B, a laser crystal 4, a coupling system, and a CCD camera 6, where the probe light source a is configured to emit probe light beams and enter the laser crystal 4, the pump source B is configured to emit pump light with different powers and enter the laser crystal 4 after passing through the coupling system, and the CCD camera 6 is configured to measure a focal point of the probe light beams emitted from the laser crystal 4. In the present embodiment, the first coupling lens 8 and the second coupling lens 9 constitute a coupling system. The detection beam is a Gaussian beam with a fundamental mode, M2 is less than 1.3, and the wavelength is 1064nm. The pump source B is an optical fiber coupling output semiconductor pump module, and pump light emitted by the pump source B is a multimode Gaussian beam. The pump light emitted upwards by the pump source B passes through the coupling system in front of the pump source B and is reflected to the right by the first 45-degree spectroscope 1 in front of the coupling system to the laser crystal 4, and the unabsorbed pump light emitted from the laser crystal 4 is reflected downwards by the second 45-degree spectroscope 2 in the right. The detection light emitted forward by the detection light source A passes through the first spectroscope 1 and then enters the laser crystal 4 behind the first spectroscope 1, and the amplified detection light emitted from the laser crystal 4 is received by the CCD on the right after passing through the second spectroscope 2, the attenuator 5 and the second focusing mirror 13 on the right of the laser crystal 4 in sequence. According to a Gaussian beam lens transformation formula, the change of the beam waist size and the beam waist position of the detection beam sequentially passing through the first focusing mirror 13, the matching mirror 7, the laser crystal 4 and the second focusing mirror 13 is accurately measured by using a CCD, and finally the thermal lens focal length of the laser crystal 4 under different pump injection powers is accurately calculated.
As an optimization scheme of the embodiment of the present utility model, referring to fig. 1, a first spectroscope 1 is disposed on an optical path between the detection light source a and the laser crystal 4. The reflection light path of the first spectroscope 1 is provided with a light absorption barrel 3. In this embodiment, the first beam splitter 1 can split the probe beam as required, and the required light is incident on the laser crystal 4, and the unwanted light is reflected to the light absorbing cylinder 3 to be absorbed.
As an optimization scheme of the embodiment of the present utility model, referring to fig. 1, a matching mirror 7 is disposed on the optical path between the detection light source a and the laser crystal 4. In this embodiment, the matching mirror 7 can select its focal length as desired. The working mode is shown in the measurement method of the first embodiment.
As an optimization scheme of the embodiment of the present utility model, referring to fig. 1, the coupling system includes a first coupling mirror 8 and a second coupling mirror 9, where the first coupling mirror and the second coupling mirror 9 are sequentially disposed on an optical path from which the pump light exits. In this embodiment, the pump light is coupled and enters the laser crystal 4 to excite the pump light. Pump light of different powers may be provided.
As an optimization scheme of the embodiment of the present utility model, referring to fig. 1, a second beam splitter 2 is further disposed on the optical path between the laser crystal 4 and the coupling system. An attenuation component is arranged on the reflection light path of the second beam splitter 2, and the detection light beam emitted from the laser crystal 4 enters the CCD camera 6 after being reflected by the second beam splitter 2 and attenuated by the attenuation component. In this embodiment, the attenuation can avoid the damage caused by the direct receiving of strong light by the CCD camera 6, and the W-level light can be attenuated to the mw-level. Preferably, the attenuation assembly includes a first beam splitter prism 11 and a second beam splitter prism 12, and the probe beam sequentially passes through the first beam splitter prism 11 and the second beam splitter prism 12. The attenuation assembly further comprises an attenuator 5, and the probe beam passing through the second beam splitter prism 12 enters the attenuator 5. The attenuation can be realized by adopting two beam splitting prisms to match with attenuation, and then the attenuator 5 is added for attenuation, so that the attenuation effect can be improved.
As an optimization scheme of the embodiment of the present utility model, referring to fig. 1, the CCD camera 6 is disposed on an electric sliding table 16 with a grating ruler. In the present embodiment, the electric slide table 16 with the grating ruler is provided so that the focus position can be found accurately.
As an optimization scheme of the embodiment of the present utility model, referring to fig. 1, the probe beam output by the second beam splitter 2 is reflected to the first beam splitter prism 11 by the first mirror 10. The probe beam from the second beam splitter prism 12 is also focused by a focusing mirror 13. And then reflected by the second mirror 14 to the third mirror 15 and finally reflected by the third mirror 15 into the CCD camera 6. The transmission direction of the light path can be changed by designing a plurality of reflecting mirrors, so that the arrangement of the device is more space-saving. The second prism 12 is also provided with a beam splitting cylinder. In the above-described optical path, a first focusing mirror, which is a temporary mirror, and a second focusing mirror, which serves to focus the probe beam emitted from the laser crystal, are also used.
Although embodiments of the present utility model have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made therein without departing from the principles and spirit of the utility model, the scope of which is defined in the appended claims and their equivalents.
Claims (10)
1. A laser crystal thermal lens focal length measuring device is characterized in that: comprises a detection light source, a pumping source, a laser crystal, a coupling system and a CCD camera,
the detection light source is used for emitting detection light beams and entering the laser crystal,
the pumping source is used for emitting pumping light with different powers and entering the laser crystal after passing through the coupling system,
the CCD camera is used for measuring the focus of the detection light beam emitted from the laser crystal.
2. A laser crystal thermal lens focal length measuring device as claimed in claim 1, wherein: and a first spectroscope is arranged on a light path between the detection light source and the laser crystal.
3. A laser crystal thermal lens focal length measuring device as claimed in claim 2, wherein: the reflection light path of the first spectroscope is provided with a light absorption barrel.
4. A laser crystal thermal lens focal length measuring device as claimed in claim 1, wherein: and a matching mirror is arranged on the light path between the detection light source and the laser crystal.
5. A laser crystal thermal lens focal length measuring device as claimed in claim 1, wherein: the coupling system comprises a first coupling mirror and a second coupling mirror, and the first coupling mirror and the second coupling mirror are sequentially arranged on an optical path of the emergent pumping light.
6. A laser crystal thermal lens focal length measuring device as claimed in claim 1, wherein: and a second beam splitter is arranged on the light path between the laser crystal and the coupling system.
7. A laser crystal thermal lens focal length measuring device as claimed in claim 6, wherein: an attenuation component is arranged on the reflection light path of the second beam splitter, and the detection light beam emitted from the laser crystal enters the CCD camera after being reflected by the second beam splitter and attenuated by the attenuation component.
8. A laser crystal thermal lens focal length measuring device as claimed in claim 7, wherein: the attenuation component comprises a first beam splitting prism and a second beam splitting prism, and the detection light beam sequentially passes through the first beam splitting prism and the second beam splitting prism.
9. A laser crystal thermal lens focal length measuring device as claimed in claim 8, wherein: the attenuation component also comprises an attenuator, and the detection light beam passing through the second beam splitting prism enters the attenuator.
10. A laser crystal thermal lens focal length measuring device as claimed in claim 1, wherein: the CCD camera is arranged on an electric sliding table with a grating ruler.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116698362A (en) * | 2023-02-23 | 2023-09-05 | 武汉华日精密激光股份有限公司 | Method and device for measuring focal length of end-pumped laser crystal thermal lens |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN116698362A (en) * | 2023-02-23 | 2023-09-05 | 武汉华日精密激光股份有限公司 | Method and device for measuring focal length of end-pumped laser crystal thermal lens |
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