CN112928587A - Laser oscillator for generating light spots in any shapes - Google Patents
Laser oscillator for generating light spots in any shapes Download PDFInfo
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- CN112928587A CN112928587A CN202110097932.2A CN202110097932A CN112928587A CN 112928587 A CN112928587 A CN 112928587A CN 202110097932 A CN202110097932 A CN 202110097932A CN 112928587 A CN112928587 A CN 112928587A
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- 238000003384 imaging method Methods 0.000 claims abstract description 25
- 230000003287 optical effect Effects 0.000 claims description 15
- 150000002500 ions Chemical class 0.000 claims description 6
- 230000003595 spectral effect Effects 0.000 claims description 4
- 238000001228 spectrum Methods 0.000 claims description 4
- 239000000919 ceramic Substances 0.000 claims description 2
- 239000013078 crystal Substances 0.000 claims description 2
- 239000000087 laser glass Substances 0.000 claims description 2
- 230000008646 thermal stress Effects 0.000 abstract description 8
- 239000002131 composite material Substances 0.000 description 8
- 238000010586 diagram Methods 0.000 description 8
- 239000011248 coating agent Substances 0.000 description 6
- 238000000576 coating method Methods 0.000 description 6
- 238000005086 pumping Methods 0.000 description 6
- 230000000694 effects Effects 0.000 description 4
- 239000010408 film Substances 0.000 description 4
- 230000035882 stress Effects 0.000 description 3
- 230000010355 oscillation Effects 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000008358 core component Substances 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 238000002207 thermal evaporation Methods 0.000 description 1
- 239000010409 thin film Substances 0.000 description 1
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
- H01S3/08—Construction or shape of optical resonators or components thereof
- H01S3/081—Construction or shape of optical resonators or components thereof comprising three or more reflectors
- H01S3/0813—Configuration of resonator
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
- H01S3/08—Construction or shape of optical resonators or components thereof
- H01S3/08059—Constructional details of the reflector, e.g. shape
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Abstract
本发明提供一种激光振荡器，采用成像系统作为谐振腔，结合异形增益介质，产生与激光增益介质形似的任意形状激光光斑，同时具有释放热应力、改善激光波前，以及避免鬼像等作用。成像系统的谐振腔可以减少高阶模的衍射损耗(高频空间信息损耗)，使得高阶模可以与低阶模无差别的在腔内形成振荡，这点与传统激光器只有低阶横模可以振荡截然不同，因此可以根据增益介质的形状产生的任意与增益介质形状相似的激光光斑。这种任意光斑形状的激光可以用于特殊激光加工或者激光医疗领域等。
The present invention provides a laser oscillator, which adopts an imaging system as a resonant cavity, combined with a special-shaped gain medium to generate a laser spot of any shape similar to the laser gain medium, and has the functions of releasing thermal stress, improving laser wavefront, and avoiding ghost images. . The resonator of the imaging system can reduce the diffraction loss of the high-order mode (high-frequency spatial information loss), so that the high-order mode can oscillate in the cavity indistinguishable from the low-order mode, which is completely different from the traditional laser that only the low-order transverse mode can oscillate. Therefore, any laser spot similar to the shape of the gain medium can be generated according to the shape of the gain medium. This laser with any spot shape can be used in special laser processing or laser medical fields.
Description
Technical Field
The invention relates to the field of laser, in particular to a laser oscillator for generating a light spot with any shape.
Background
At present, a facula laser with any shape is generally generated by end mirror coating or inserting a binary optical element in or out of a cavity, the two ways can affect the laser efficiency, and along with the improvement of laser energy density, the thermal effect of a gain medium is very obvious, such as wavefront distortion and thermal stress, which causes the quality reduction of laser beams and even stress cracks.
Disclosure of Invention
Based on the defects of the traditional laser for generating laser spots in any shapes, the invention provides a laser oscillator for generating laser spots in any shapes, which adopts a laser resonant cavity with an imaging structure and a special-shaped gain medium. The traditional laser only can generate oscillation in a low-order transverse mode due to serious diffraction loss, and the position of the low-order transverse mode is more concentrated in the middle position of the gain medium, so that the traditional laser cannot be provided with holes or special-shaped structures in the laser gain medium regardless of a laser oscillator or a laser amplifier.
The concrete technical scheme of the invention is as follows:
a laser resonant cavity for generating light spots in any shapes comprises a laser resonant cavity with an imaging structure, a special-shaped gain medium and a pumping source, wherein the gain medium is the special-shaped gain medium, and the special shape or doping distribution of the special-shaped gain medium is utilized to combine the special-shaped gain medium and the special-shaped gain medium into an imaging laser resonant cavity to generate any laser spots similar to the special-shaped gain medium in shape.
The imaging structure resonant cavity is a flat cavity or an imaging system with a lens or other binary optical elements. Generally, the object plane, the image plane and the spectral plane (4F system), but may also be composed of the object plane and the spectral plane (half/multi 4F system) or composed of the object plane and the image plane (flat cavity). In the imaging systems with the structures, the loss difference between the high-order mode and the low-order mode of the flat cavity is large, while the loss difference between the high-order mode and the low-order mode is reduced due to the introduction of the lens in the 4F system, and the output power ratio between the modes is almost the same.
The special-shaped gain medium is used for generating laser photons; is a cylinder with a hole structure or a cuboid, or other polyhedrons and other shapes. The holes may be of various shapes and sizes.
The special-shaped gain medium can be any medium capable of generating laser, and comprises a single crystal gain medium, a laser ceramic gain medium, a laser glass gain medium and the like.
The special-shaped gain medium can be a composite structure or a composite structure with holes. The composite structure means that laser doped ions in the laser gain medium can be distributed to a certain extent, for example, the middle part of the laser gain medium is not doped with the laser ions, and the periphery is doped; and for example, the end caps at both ends of the laser gain medium are undoped laser ions, and so on.
The pumping source is used for exciting the laser gain medium and can adopt a side pumping mode or an end pumping mode.
The coating of the optical element in the laser oscillator can be selected according to the actual situation, for example, a special-shaped gain medium, preferably a laser film with anti-reflection function on laser can be coated at both ends, and if an end-face pumping structure is selected, a laser film with high transmission on pumping light can be also selected. The coating on the laser reflector can be a full-coating reflecting film or a local coating according to the shape of the gain medium
The laser oscillator also comprises elements such as an electro-optical switch, a wave plate, a polarizer and the like, and is used for Q-switching output.
The resonant cavity of the imaging structure can adjust the cut-off frequency in the cavity on a frequency spectrum plane.
Compared with the prior art, the invention has the beneficial effects that:
1) the imaging resonant cavity structure allows the loss of the high-order mode to be smaller than that of the low-order mode even so that the special-shaped laser gain medium can be used and a light spot shape which is highly similar to the shape structure of the special-shaped gain medium is generated.
2) Compared with the use of a laser cavity mirror coating or a binary optical element, the hole in the gain medium structure or the use of a composite structure has a good effect on releasing thermal stress, so that the laser efficiency is not influenced, the larger laser power can be output, and the special-shaped gain medium can not be influenced by ghost images of various stages in the resonant cavity.
3) Has the functions of releasing thermal stress, improving laser wavefront, avoiding ghost image, etc. The resonant cavity of the imaging system can reduce the diffraction loss (high-frequency spatial information loss) of a high-order mode, so that the high-order mode can form oscillation in the cavity without difference from a low-order mode, which is completely different from the situation that only a low-order transverse mode of a traditional laser can oscillate, and therefore any laser spot with the shape similar to that of a gain medium can be generated according to the shape of the gain medium. The laser with any spot shape can be used for special laser processing or laser medical fields and the like.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 is a simplified schematic diagram of the present invention
FIG. 2: laser schematic diagram of any spot shape of 4F structure
FIG. 3: cylindrical circular hole laser gain medium, front view (a), side view (b)
FIG. 4: cylindrical round hole laser gain medium laser output facula (a) and one-dimensional distribution (b)
FIG. 5: thermal stress relief (a) stress distribution of conventional non-porous gain medium, and (b) thermal stress distribution of porous gain medium
FIG. 6: composite structure laser gain medium with undoped central region
FIG. 7: composite structure laser gain medium with end caps at two ends, no doping of end caps, and hole in central region
FIG. 8 is a schematic view of a gain medium (a) petal-shaped gain medium (b) two-dimensional distribution of petal-shaped laser spots (c) one-dimensional distribution of petal-shaped laser spots
FIG. 9: schematic diagram for avoiding ghost image influence
FIG. 10: oscillator schematic using binary optical element as lens
FIG. 11: frequency adjustment diagram of frequency spectrum plane
FIG. 12: after the filter holes are added, laser spots generated by the cylindrical gain medium with holes are distributed in two dimensions (a) and divided in one dimension (b)
FIG. 13: laser Q-switching structure schematic diagram of any light spot shape
1, an imaging cavity; 2: a profiled gain medium; 3: a pump source; 4: a total reflection mirror; 5: a lens f 1; 6: a lens f 2; 7: an output mirror; 8: a binary optical element 1; 9: a binary optical element 2; 10: a filter aperture; 11: a film polarizer TPF; 1/4 wave plate; 13: an electro-optical switch.
Detailed Description
In order to make the technical solutions of the present invention better understood, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. The invention will be further illustrated and described with reference to the drawings and preferred embodiments of the description, without thereby limiting the scope of the invention.
The core components of the present invention are the imaging cavity + the heterotropic gain medium and the pump source, which are exemplified in the examples that follow.
Example 1:
this embodiment is a laser oscillator of a 4F imaging cavity, as shown in fig. 2. The resonant cavity 1 of the imaging structure consists of a total reflection mirror, an output mirror and lenses, wherein the object plane is the total reflection mirror, the image plane is the output mirror, and the two lenses are used as frequency domain conversion elements. Fig. 3 shows the anisotropic gain medium selected for use in this embodiment, with an opening in the middle region. Although the center of the shaped gain medium (or elsewhere) is empty, in a 4F imaging cavity, the gain medium is located between the lens and the object plane, and thus the shape of the gain medium can be imaged in the imaging plane, and thus the shape of the gain medium can determine the shape of the output spot. The higher the cut-off frequency of the 4F imaging system is, the more high-order modes can be accommodated, and the loss of the high-order modes and the loss of the low-order modes are determined by the structure of the imaging cavity. Fig. 4 is a laser spot produced in this embodiment, and it can be seen that the shape is consistent with that of the gain medium. FIG. 5 is a graph showing that, in the case of laser thermal deposition of 10W, a Nd: YAG rod with a length of 115mm is simulated, the thermal stress generated by the normal laser rod is 70N at the maximum, the diameter of the middle opening of the anisotropic gain medium is 1mm, the maximum stress is 57N, the reduction is 20%, and the thermal stress is obviously improved.
FIG. 6 is a schematic diagram of a composite structure gain medium with no doping in the central region
FIG. 7 shows a composite laser gain medium with end caps at both ends, the end caps being undoped, and the central region being perforated
FIG. 8 is a schematic view of a petaloid gain medium and its laser output spot
Fig. 9 is a schematic diagram of the present invention for avoiding ghost effects. The ghost image is usually formed due to the residual reflection of the optical device in the optical path, and particularly after the residual reflection of the lens or the residual reflection of other devices passes through the lens, a focus point is easily generated, and if the focus point falls on the optical device including the gain medium, the beam distribution is affected and even optical damage is caused. For a degenerate laser cavity of a near 4f system or a 4f system, the ghost image is generally located on the central axis, and the middle region of the shaped gain medium is hollow, so that even if the ghost image is formed, the special-shaped gain medium is not seriously affected, which is different from the common degenerate laser cavity.
Example 2:
fig. 10 is a schematic diagram of an embodiment in which a binary optical element 1(8) and a binary optical element 2(9) are used instead of a normal lens. The binary optical lens has the effect of Fourier change as the traditional lens, and can completely replace the traditional lens to carry out frequency transformation to form a frequency domain surface. Other embodiments are also within the scope of the patent claims, which can generate frequency domain surfaces instead of lenses.
Example 3:
as shown in fig. 11, in the first embodiment, a filter hole is added to a spectrum plane to perform mode limiting, and the shape of the filter hole is circular. The generated laser spot is shown in fig. 12, and it can be seen that the edge of the laser spot has no burr relative to the laser spot generated without the pinhole, which indicates that the high-frequency information (the edge of the object) has been filtered by the filtering pinhole.
Example 4:
this embodiment is an example of a multi-wavelength Q-switched laser, and as shown in fig. 13, an electro-optical switch, 1/4 wave plate, and a thin film polarizer TPF are added for Q-switching. The mode of Q adjustment can also be changed, for example, at TPF, the design of an inverted cavity is adopted, and the output mirror can be replaced by a total reflection mirror; for example, the method can be realized by directly using an electro-optical switch without using a wave plate; other ways of adjusting Q are also within the scope of the patent claims.
Claims (8)
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| CN202110097932.2A CN112928587B (en) | 2021-01-25 | 2021-01-25 | Laser oscillator for generating light spot with any shape |
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| CN202110097932.2A CN112928587B (en) | 2021-01-25 | 2021-01-25 | Laser oscillator for generating light spot with any shape |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116646808A (en) * | 2023-06-06 | 2023-08-25 | 四川大学 | Method for realizing continuous optical degenerate cavity laser by utilizing thermal lens effect |
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