CN116526289A - Structure for realizing line width narrowing of blue light semiconductor laser - Google Patents
Structure for realizing line width narrowing of blue light semiconductor laser Download PDFInfo
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- CN116526289A CN116526289A CN202310281819.9A CN202310281819A CN116526289A CN 116526289 A CN116526289 A CN 116526289A CN 202310281819 A CN202310281819 A CN 202310281819A CN 116526289 A CN116526289 A CN 116526289A
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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
- H01S5/00—Semiconductor lasers
- H01S5/10—Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region
- H01S5/14—External cavity lasers
- H01S5/141—External cavity lasers using a wavelength selective device, e.g. a grating or etalon
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Abstract
The invention discloses a structure for realizing line width narrowing of blue semiconductor laser, which belongs to the technical field of semiconductor laser and solves the problems of small effective thickness, laser self-emission and poor line width narrowing effect of VBG in the prior art. According to the invention, by arranging the structure of the binary Bragg grating, the problem that the large thickness is difficult to realize due to the self process of the binary Bragg grating is effectively solved, the influence of secondary peaks is filtered, the problem of laser self-irradiation is effectively solved, the spectral characteristics of semiconductor laser are optimized, and the further narrowing of the laser linewidth is realized.
Description
Technical Field
The invention belongs to the technical field of semiconductor lasers, and particularly relates to a structure for realizing the line width narrowing of a blue semiconductor laser.
Background
The high-power blue light semiconductor laser can be used as one of RGB laser display light sources, and can be combined with red light and green light to generate white light, so that the high-power blue light semiconductor laser can be applied to the field of laser display. The laser is used as a display light source, and has the advantages of wide color gamut, long service life, extremely high light energy utilization rate, energy conservation, environmental protection and the like. In addition, in the laser processing field, the optical fiber laser with the wavelength of 1064nm is adopted to cut, weld, clad and 3D print nonferrous metals such as gold, copper and the like, and the high-reflectivity material has low near infrared light absorption efficiency, so that the problems of splashing, spheroidization, poor weld joint forming and the like are very easy to generate, and the blue light laser has high absorption efficiency, so that blue light can be adopted to replace the traditional near infrared laser for nonferrous metal laser processing.
However, since the spectral linewidth of a free-running blue semiconductor laser is usually 3 to 5nm, and a wide spectral width affects the laser display and the laser processing effect, it is necessary to narrow the spectral linewidth of the blue semiconductor laser by technical means.
The blue light semiconductor laser chip with the front cavity surface for reflection increase provides a gain medium and a rear cavity surface of a resonant cavity, a Volume Bragg Grating (VBG) is used as the front cavity surface of the resonant cavity, particle number inversion is realized under the action of electric excitation, VBG feedback light is used as seed light, narrow linewidth laser output is formed by amplifying the VBG, and single-path adjustment is realized by using the VBG, so that the requirement on the light emission consistency of a blue light semiconductor laser unit device is low, and meanwhile, the wavelength selection characteristic of the VBG enables the semiconductor laser to resonate at the VBG diffraction wavelength, so that the screening of the semiconductor laser wavelength and the line width narrowing are realized.
The invention provides a structure for realizing further narrowing of blue light semiconductor laser linewidth based on a volume Bragg grating external cavity feedback technology.
Disclosure of Invention
The invention aims to overcome the defects in the prior art, and provides a structure for realizing the line width narrowing of a blue light semiconductor laser, which increases the effective thickness of a VBG, solves the problem of laser self-excitation and further narrows the line width.
In order to achieve the technical purpose, the structure for realizing the line width narrowing of the blue semiconductor laser adopts the following technical scheme:
the utility model provides an realize structure that blue light semiconductor laser linewidth is narrowed, includes coaxial blue light semiconductor laser, fast axis collimating mirror, slow axis collimating mirror, first body Bragg grating and the second body Bragg grating that sets gradually, fast axis collimating mirror collimates the laser divergence angle of fast axis direction, slow axis collimating mirror collimates the laser divergence angle of slow axis direction, first body Bragg grating carries out first linewidth narrowing and locking to laser, second body Bragg grating diffraction wavelength matches with the wavelength after the first linewidth locking, the distance of second body Bragg grating and first body Bragg grating is 1 ~ 3mm.
Preferably, the front cavity surface of the blue light semiconductor laser is an anti-reflection type.
Preferably, the first body Bragg grating is arranged at the right side of the slow axis collimating mirror by 1-5 mm along the light-emitting direction.
Preferably, the diffraction efficiency of the first volume bragg grating is 10±3%, and the diffraction efficiency of the second volume bragg grating is 10±3%.
Compared with the prior art, the invention has the beneficial effects that:
according to the invention, by arranging the structure of the binary Bragg grating, the problem that the high-power semiconductor laser linewidth narrowing effect is reduced due to the fact that the large thickness is difficult to realize due to the self process of the binary Bragg grating is effectively solved; the first body Bragg grating is utilized for external cavity feedback, so that the spectrum linewidth is narrowed, the center wavelength is similar to the diffraction wavelength of the first body Bragg grating, laser is initially locked, and the influence of the red shift phenomenon on the center wavelength of the laser after external cavity feedback is reduced; the influence of secondary peaks is filtered through the external cavity feedback of the two Bragg gratings, so that the problem of laser self-excitation is effectively solved, the spectral characteristics of semiconductor laser are optimized, and the further narrowing of the laser linewidth is realized.
Drawings
FIG. 1 is a schematic diagram of a prior art structure;
fig. 2 is a schematic structural view of the present invention.
In the figure: 1. a blue semiconductor laser; 2. a fast axis collimator lens; 3. a slow axis collimating mirror; 4. a first body bragg grating; 5. and a second volume bragg grating.
Detailed Description
The invention is further described below with reference to the drawings and detailed description:
as shown in fig. 1, a structure for realizing line width narrowing of a blue semiconductor laser in the prior art comprises a blue semiconductor laser, a fast axis collimating mirror, a slow axis collimating mirror and a volume bragg grating which are coaxially arranged in sequence, wherein a laser chip in the blue semiconductor laser emits laser and then is compressed and shaped through the fast axis collimating mirror and the slow axis collimating mirror, so that the divergence angle of the semiconductor laser is compressed to mrad magnitude, and the Volume Bragg Grating (VBG) has angle selectivity, so that the smaller the divergence angle of incident light is, the better the diffraction effect is, the more favorable the line width narrowing is, the shaped laser is incident on the VBG, and the semiconductor laser and the VBG form an external cavity structure, thereby realizing spectrum line width narrowing.
For a VBG of thickness d, its ideal narrowing spectral linewidth narrowing can be expressed as:
Δλ FWHM ＝0.3(λ B ) 2 /d，
wherein Deltalambda FWHM Represents the spectral width lambda after locking B Represents the VBG diffraction wavelength, and d represents the VBG thickness.
Therefore, when the thickness of the VBG is larger, the line width is narrower after the VBG is compressed, but the prior art is limited by the processing technology of the VBG material and the grating design processing technology, so that the thickness of the VBG is generally 1-3 mm, the VBG with larger thickness is obviously improved from the technical angle or the cost angle compared with the conventional VBG, the VBG is difficult to popularize and apply, and the phenomenon of red shift is generated when the center wavelength of the free-running semiconductor laser is injected along with the current, namely, the wavelength moves towards the long wavelength direction. After the diffraction wavelength of the VBG is usually selected, although the current injection change is smaller, the difference between the semiconductor laser center wavelength and the VBG diffraction wavelength is different under different currents, the closer the laser center wavelength is to the VBG diffraction wavelength, the better the locking effect is, namely, only one main peak with a narrow linewidth is provided, no other secondary peaks are provided, when the difference between the two is larger, the semiconductor laser self-excitation effect is serious, the secondary peaks are obvious, and the final linewidth narrowing effect is influenced.
As shown in fig. 2, the structure for realizing the line width narrowing of the blue semiconductor laser comprises a blue semiconductor laser 1, a fast axis collimating mirror 2, a slow axis collimating mirror 3, a first bulk bragg grating 4 and a second bulk bragg grating 5 which are coaxially and sequentially arranged, wherein the front cavity surface of the blue semiconductor laser 1 is an anti-reflection type, the fast axis collimating mirror 2 collimates the laser divergence angle in the fast axis direction, the slow axis collimating mirror 3 collimates the laser divergence angle in the slow axis direction, the first bulk bragg grating 4 performs first line width narrowing and locking on the laser, the diffraction wavelength of the second bulk bragg grating 5 is matched with the wavelength after the first line width locking, the distance between the second bulk bragg grating 5 and the first bulk bragg grating 4 is 1-3 mm, and the first bulk bragg grating 4 is arranged on the right side of the slow axis collimating mirror along the light outlet direction.
In the present invention, the diffraction efficiency of the first bulk bragg grating 4 is 10±3%, and the diffraction efficiency of the second bulk bragg grating 5 is 10±3%.
After the front cavity surface of the blue light semiconductor laser 1 is anti-reflection, a laser chip provides a gain medium and the rear cavity surface of a resonant cavity, laser sequentially passes through a fast axis collimating mirror 2 and a slow axis collimating mirror 3 to respectively collimate laser divergence angles in two directions of a fast axis and a slow axis, after collimation, the divergence angles can be compressed to mrad magnitude, a first Bragg grating 4 is used as the front cavity surface of the resonant cavity, particle number inversion is realized under the effect of electric excitation, the feedback light of the first Bragg grating 4 is used as seed light, the resonant cavity is amplified, so that the collimated laser forms narrow linewidth laser output, the laser after narrowing still has the influence of self-excitation phenomenon and secondary peak under different working currents, but the main laser power is concentrated on a main peak at the moment, under different working currents, the center wavelength of the laser after line width narrowing is near the diffraction wavelength of the first body Bragg grating 4, the red shift phenomenon generated by the semiconductor laser has small influence on the center wavelength of the laser after external cavity feedback of the first body Bragg grating 4, the laser after preliminary locking is subjected to secondary external cavity feedback through the second body Bragg grating 5, the center wavelength and the spectral line width of the incident laser are effectively controlled after the first body Bragg grating 4 is primarily locked, the spectral line width is narrow, the center wavelength is close to the diffraction wavelength of the first body Bragg grating 4, and the incident laser at the moment is subjected to secondary external cavity feedback through the second body Bragg grating 5, so that the influence of a secondary peak can be effectively filtered; meanwhile, the structure of the double-body Bragg grating increases the effective thickness of the grating, so that the problem that the single-piece large thickness cannot be provided by the body Bragg grating due to the self process is solved, and the laser linewidth is further narrowed.
Example 1
The utility model provides a realize structure that blue light semiconductor laser linewidth is narrowed, includes coaxial blue light semiconductor laser, fast axis collimating mirror, slow axis collimating mirror, first body Bragg grating and the second body Bragg grating that sets gradually, blue light semiconductor laser front chamber face is anti-reflection, fast axis collimating mirror collimates the laser divergence angle of fast axis direction, slow axis collimating mirror collimates the laser divergence angle of slow axis direction, first body Bragg grating carries out first linewidth narrowing and locking to laser, the wavelength phase-match after second body Bragg grating diffraction wavelength and the first linewidth locking, the distance of second body Bragg grating and first body Bragg grating is 1 ~ 3mm, first body Bragg grating sets up in slow axis collimating mirror right side 1 ~ 5mm along the light-emitting direction.
Specifically, taking the example of blue semiconductor laser output light propagation with the laser wavelength of 450nm and the unit power of 5W, after output laser is collimated by a fast axis collimating mirror with the divergence angle of 50 degrees and a slow axis collimating mirror with the divergence angle of 10 degrees, the divergence angles of the fast axis and the slow axis are smaller than 6mrad, and the smaller the divergence angle of incident laser is, the higher the feedback efficiency is, so that the first body Bragg grating is placed at the position of 1-5 mm on the right side of the slow axis collimating mirror along the light outlet direction for first line width narrowing, the diffraction efficiency of the first body Bragg grating is 10+/-3%, the diffraction wavelength is 449.9 +/-0.1 nm, and the thickness is 1mm, and the first body Bragg grating is utilized for preliminary optimization of the laser center wavelength and the spectrum line width. And then, carrying out secondary external cavity feedback on the laser after preliminary optimization through a second volume Bragg grating, wherein the diffraction efficiency of the second volume Bragg grating is 10+/-3%, the diffraction wavelength is matched with the wavelength after the first line width locking, namely, if the central wavelength after the first time locking is 449.950nm, the diffraction wavelength of the second volume Bragg grating is 449.950 +/-0.01 nm, the thickness is 3mm, and the optimal distance between the second volume Bragg grating and the first volume Bragg grating is 1-3 mm. Through the external cavity structure of the binary Bragg grating, the influence of secondary peaks can be filtered, and the effective thickness formed by the binary Bragg grating is 4mm, so that the further narrowing of the laser linewidth is facilitated.
In summary, the present invention is not limited to the preferred embodiments, but includes all equivalent changes and modifications in shape, construction, characteristics and spirit according to the scope of the claims.
Claims (4)
1. A structure for realizing the line width narrowing of a blue light semiconductor laser is characterized in that: the laser comprises a blue semiconductor laser, a fast axis collimating mirror, a slow axis collimating mirror, a first body Bragg grating and a second body Bragg grating, wherein the blue semiconductor laser, the fast axis collimating mirror, the slow axis collimating mirror, the first body Bragg grating and the second body Bragg grating are coaxially and sequentially arranged, the fast axis collimating mirror collimates the laser divergence angle of the fast axis direction, the slow axis collimating mirror collimates the laser divergence angle of the slow axis direction, the first body Bragg grating narrows and locks the line width of laser for the first time, the diffraction wavelength of the second body Bragg grating is matched with the wavelength after the first line width is locked, and the distance between the second body Bragg grating and the first body Bragg grating is 1-3 mm.
2. The structure for realizing line width narrowing of blue semiconductor laser according to claim 1, wherein: the front cavity surface of the blue light semiconductor laser is an anti-reflection type.
3. The structure for realizing line width narrowing of blue semiconductor laser according to claim 1, wherein: the first body Bragg grating is arranged at the right side of the slow axis collimating mirror by 1-5 mm along the light-emitting direction.
4. The structure for realizing line width narrowing of blue semiconductor laser according to claim 1, wherein: the diffraction efficiency of the first volume Bragg grating is 10+/-3%, and the diffraction efficiency of the second volume Bragg grating is 10+/-3%.
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| CN202310281819.9A CN116526289A (en) | 2023-03-22 | 2023-03-22 | Structure for realizing line width narrowing of blue light semiconductor laser |
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| CN202310281819.9A CN116526289A (en) | 2023-03-22 | 2023-03-22 | Structure for realizing line width narrowing of blue light semiconductor laser |
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