CN112018590A - Multi-wavelength non-atomic resonance Faraday semiconductor laser - Google Patents
Multi-wavelength non-atomic resonance Faraday semiconductor laser Download PDFInfo
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- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
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- H01S3/102—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating by controlling the active medium, e.g. by controlling the processes or apparatus for excitation
- H01S3/104—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating by controlling the active medium, e.g. by controlling the processes or apparatus for excitation in gas lasers
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- H—ELECTRICITY
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- 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
- H01S3/08086—Multiple-wavelength emission
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- H—ELECTRICITY
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- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/09—Processes or apparatus for excitation, e.g. pumping
- H01S3/091—Processes or apparatus for excitation, e.g. pumping using optical pumping
- H01S3/094—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light
- H01S3/0941—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light of a laser diode
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Abstract
The invention provides a multi-wavelength non-atomic resonance Faraday semiconductor laser, which comprises a laser source, a collimating lens, a Faraday atomic filter and a reflecting mirror (6) which are sequentially arranged on a light path, wherein the laser source comprises a first laser light source (1) and a second laser light source (1a), and an atomic gas chamber (4) contains a first alkali metal atom and a second alkali metal atom; the permanent magnet (5) applies a static magnetic field to the atom air chamber (4), so that the magnetic field intensity in the atom air chamber (4) is uniformly distributed in the axial direction and is non-uniformly distributed in the radial direction, and the magnetic field intensity on each emergent light path corresponds to the magnetic field intensity required by the corresponding wavelength transmission spectrum of the Faraday atom optical filter which only comprises one non-atom resonance transmission peak. The invention makes multiple beams of light pass through corresponding magnetic field areas on respective light paths through the optical filter with the non-uniform magnetic field to obtain different magnetic field strengths, thereby realizing multi-wavelength laser output without interference light.
Description
[ technical field ] A method for producing a semiconductor device
The invention belongs to the technical field of semiconductor laser, and particularly relates to a multi-wavelength non-atomic resonance Faraday semiconductor laser with a gas chamber for mixing two alkali metal atoms.
[ background of the invention ]
In the laser field, the concept of multi-wavelength lasers has existed since the early days of lasing, but its status is still rather vague. The laser output with a plurality of wavelengths is realized on the same equipment, the application efficiency of the device can be improved, the system complexity is reduced, and the cost is reduced. As more and more applications seek new laser devices, multi-wavelength laser devices are also gaining more attention.
The multi-wavelength laser can be applied to the fields such as optical communication, wavelength division multiplexing and quantum frequency standard. Conventional multi-wavelength lasers are mainly based on fiber lasers and solid state lasers. Fiber lasers are typically constructed with a relatively long resonant cavity, which makes it difficult to obtain a single longitudinal mode at each wavelength. The multi-wavelength solid-state laser generally requires pump light to act on a laser medium, and although such a laser can achieve multi-wavelength output, the structure of the laser is complex, for example, a pump laser module, a frequency doubling module, a solid-state laser module, an output wavelength selection module, and the like need to be included. However, the multi-wavelength bandwidth achieved by these prior arts is usually in the nanometer level, and cannot be used in the field of quantum frequency standard requiring high wavelength precision of laser.
The natural linewidth of the absorption spectrum of alkali metal atoms is about several picometers, and research in this field has mainly focused on reducing the linewidth of the pump laser and locking the pump laser at the wavelength of atomic transition. Such as the widely used bulk bragg grating (VBG) semiconductor laser, has the major disadvantage of absorbing internal heating caused by optical power, resulting in wavelength detuning. Another disadvantage is that the wavelength is not accurate and must be thermally compensated. The wavelength accuracy of commercial VBGs is typically about 500 picometers of earth. There are also birefringent filters (BRFs) that facilitate narrowing the wavelength bandwidth, however, BRFs require a servo to lock the wavelength, and high power BRFs are expensive and difficult to manufacture.
In recent years, semiconductor lasers employing atomic filter mode selection have been proposed, and it has been reported that a single frequency output from such lasers is insensitive to current and temperature variations of the laser diode, and has a narrow wavelength range, typically with a fluctuation range of less than 10 picometers. There are also reports of methods using cascaded atomic filters with only one frequency transmission peak to filter light, with the laser output frequency always being a single frequency. With the development of single-wavelength atomic resonance lasers, dual-wavelength atomic resonance lasers are also proposed, and at present, two implementation methods of dual-wavelength lasers based on atomic filtering are provided, and chinese patent application CN2019109431848 discloses a first implementation method, as shown in fig. 1, including a cesium atom gas chamber and a 852nm laser source, where the dual-wavelength laser frequency is determined by two transmission peaks of the optical filter, the two transmission peaks correspond to atomic resonance wavelengths, the frequency interval is about 9GHz, and is only limited to be near the corresponding cesium atom ground state energy level interval. The second method is to use an atomic gas cell mixed with rubidium and cesium to realize dual-wavelength output of 780nm and 852nm, as shown in fig. 2, and to inject the light beams emitted from the two light sources into the rubidium and cesium mixed atomic gas cell under the same magnetic field condition, thereby outputting a laser beam including two wavelengths. However, according to the prior art, the magnetic field required for 780nm laser beam is about 203 gauss, the magnetic field required for 852nm laser beam is about 330 gauss, and in the method shown in FIG. 2, since the two beams are combined, the 780nm and 852nm lasers can only be under the same magnetic field condition, if the magnetic field is set between 200 and 300 gauss, this method can output 780nm and 852nm laser light, but according to the teaching of CN2019109431848, under the condition of the magnetic field, the transmission spectrum of the cesium atom 852nm is shown in FIG. 3, the abscissa is frequency, the ordinate is transmittance, the left graph corresponds to the transmission spectrum of the cesium atom 852nm ground state F being 3 transitions, the right graph corresponds to the transmission spectrum of the cesium atom 852nm ground state F being 4 transitions, where the frequency spacing between the ground state F3 and the ground state F4 is 9.19GHz, it can be seen that, at a magnetic field of 330 gauss, the transmission spectrum of a 852nm faraday anomalous dispersion atomic filter with cesium atoms contains two transmission and spurious peaks at the ground state F-3 transition and the ground state F-4 transition. Under the condition of the magnetic field of about 300 gauss, the output 852nm laser actually comprises two frequencies which are different by 9GHz, so the method shown in FIG. 2 cannot really realize the laser with two wavelengths of 780nm and 852nm, and at least the output 852nm laser itself comprises two frequency components, which is not preferable in the application of measuring the laser spectrum, because one of the frequency components can become interference light to influence the spectrum measurement.
It is known from the prior art that at the wavelength of 852nm, the sidebands can be suppressed by filling the cesium atom gas chamber with buffer gas and increasing the magnetic field to eliminate the interference light, so that the transmission spectrum only contains a narrow-band signal which is not in atomic resonance. At 780nm wavelength, the sideband can be suppressed by filling buffer gas without increasing the magnetic field, so that one frequency is selected for each laser wavelength to eliminate interference light. It can be seen from this that, in the structure shown in fig. 2, since the beams of two wavelengths are always under the same magnetic field condition, it is impossible to set different magnetic fields for beams of different wavelengths in the structure regardless of whether or not the buffer gas is filled in the atomic gas chamber, the 852nm and 780nm outputs of interference-free light cannot be realized by the structure shown in fig. 2. Namely, in the two methods, the dual-wavelength laser is completed under the condition of a uniform magnetic field, and each wavelength is subjected to frequency selection under the same magnetic field condition, so that the realized output shows limitation.
[ summary of the invention ]
The invention aims to overcome the defects of the prior art and provide a non-atomic resonance semiconductor laser which is simple in structure, free of interference light and stable in multi-wavelength output.
The idea of the invention is to adopt the atomic filtering technology of different wavelengths, mix different alkali metal atoms in an atomic gas chamber, and apply axially uniform and radially non-uniform static magnetic field for the atomic gas chamber, when the laser penetrates the atomic gas chamber, because the light path is located in different positions and obtains the magnetic field of different intensity, make the laser of different wavelengths carry on the frequency selection under the corresponding magnetic field condition, thus the transmission spectrum that each wavelength corresponds only has a narrow band transmission peak of non-atomic resonance, thus choose a laser mode for each wavelength, realize the double wavelength non-atomic resonance half Faraday waveguide laser of the interference-free light finally.
Based on the above thought, the present invention provides a multiwavelength non-atomic resonance faraday semiconductor laser, as shown in fig. 4, the laser includes a laser source, a collimating lens, a faraday atomic filter and a reflector 6 which are sequentially arranged on an optical path, the faraday atomic filter includes a first polarization splitting prism 3, an atomic gas chamber 4, a permanent magnet 5 for applying an axial static magnetic field to the atomic gas chamber 4, and a second polarization splitting prism 3a, and the position relationship between the first polarization splitting prism 3 and the second polarization splitting prism 3a is orthogonal;
the laser source comprises a first laser light source 1 and a second laser light source 1a, emergent light of the first laser light source 1 and emergent light of the second laser light source 1a are two beams of coherent light beams polarized in the vertical direction, the collimating lens comprises a first collimating lens 2 and a second collimating lens 2a, the first collimating lens 2 is arranged on an emergent light path of the first laser light source 1, and the second collimating lens 2a is arranged on an emergent light path of the second laser light source 1 a;
the atomic gas chamber 4 contains a first alkali metal atom and a second alkali metal atom;
the permanent magnet 5 applies a static magnetic field to the atomic gas chamber 4, so that the magnetic field strength in the atomic gas chamber 4 is uniformly distributed in the axial direction and is non-uniformly distributed in the radial direction, a first magnetic field strength on an emergent light path of the first laser light source 1 corresponds to the magnetic field strength required by a first wavelength transmission spectrum of the Faraday atomic filter, which only comprises one non-atomic resonance transmission peak, and a second magnetic field strength on an emergent light path of the second laser light source 1a corresponds to the magnetic field strength required by a second wavelength transmission spectrum of the Faraday atomic filter, which only comprises one non-atomic resonance transmission peak;
coherent light beams emitted by a first laser light source 1 and a second laser light source 1a are collimated into first parallel light and second parallel light through a first collimating lens 2 and a second collimating lens 2a respectively, most of the parallel light passes through a first polarization splitting prism 3, and a small part of the parallel light is reflected and output by the first polarization splitting prism 3, the first polarized light is subjected to frequency selection under a first magnetic field intensity after entering an atom air chamber 4 to obtain first frequency emergent light, the first frequency emergent light passes through the second polarization splitting prism 3a, is reflected back to the first semiconductor laser light source 1 by a reflector 6, oscillates and amplifies in a resonant cavity formed between a non-light-emitting end face of the first semiconductor laser light source 1 and the reflector 6 until the first frequency emergent light exceeds a laser oscillation threshold value, and first output light 8 is output from the first polarization splitting prism 3;
meanwhile, the second polarized light is incident to the atomic gas chamber 4 and then is subjected to frequency selection under the second magnetic field intensity to obtain second frequency emergent light, the second frequency emergent light is reflected to the second semiconductor laser source 1a by the reflector 6 after passing through the second polarization beam splitter prism 3a and is oscillated and amplified in a resonant cavity formed between the non-light-emitting end face of the second semiconductor laser source 1a and the reflector 6 until the oscillation threshold of the laser is exceeded, and second output light 8a is output from the first polarization beam splitter prism 3.
In the present invention, the first alkali metal atom or the second alkali metal atom is an alkali metal atom based on different magnetic fields and having a single non-atomic resonance transmission peak, and they may be selected from rubidium atom, cesium atom or potassium atom, and the first alkali metal atom is different from the second alkali metal atom.
According to a preferred embodiment, in order to obtain transmission spectra of 780nm and 852nm, the first alkali metal atom is a rubidium atom, the first magnetic field strength is 200-300 gauss, and the first transmission spectrum corresponds to a wavelength of 780 nm; the second alkali metal atom is cesium atom, the second magnetic field strength is 900-.
The magnetic field strength in the atomic gas cell 4 can be uniformly distributed in the axial direction and non-uniformly distributed in the radial direction by arranging corresponding permanent magnets outside the atomic gas cell. Specifically, these permanent magnets are arranged axially along the atomic cell 4 to ensure that an axially uniform static magnetic field is obtained, but their distribution with respect to the radial position of the atomic cell is not uniform, and a non-uniform static magnetic field can be applied to the atomic cell by changing the positions of the permanent magnets in the radial direction, or adjusting the number of permanent magnets at different positions, so that different radial positions in the atomic cell obtain different magnetic field strengths. Therefore, the two light beams with different wavelengths on different optical paths are respectively subjected to frequency selection through respective proper magnetic field conditions so as to output the multi-wavelength laser without interference light, and a beam splitter is not required.
Similarly, by adding the optical paths and adjusting the magnetic field intensity obtained by each optical path within the atomic gas cell 4, the output light can be further increased. For example, in order to realize three-wavelength output, the laser source further includes a third laser light source 1b, a third collimator lens 2b is disposed on an exit light path of the third laser light source 1b, and the collimator lens further includes a third collimator lens 2 b; three beams of parallel light respectively pass through a first polarization beam splitter prism 3 to obtain three beams of coherent light beams polarized in the vertical direction; the atomic gas chamber 4 contains a third alkali metal atom, and the third alkali metal atom is different from the first alkali metal atom or the second alkali metal atom; and the third magnetic field intensity on the emergent light optical path of the third laser light source 1b corresponds to the magnetic field intensity required by the third wavelength transmission spectrum of the Faraday atomic filter, which only comprises one non-atomic resonance transmission peak.
In order to make the transmission spectrum contain a non-atomic resonance narrow-band signal at the desired wavelength, the filling of the atomic gas cell 4 with buffer gas can be used to suppress sidebands and eliminate interfering light.
In the present invention, the buffer gas is selected from argon, xenon or helium.
Preferably, the output light end faces of the first laser light source 1, the second laser light source 1a and the third laser light source 1b are coated with antireflection films.
In the invention, the piezoelectric ceramics 7 are arranged on the reflector 6, so that the cavity length of the resonant cavity can be adjusted through the piezoelectric ceramics 7.
According to a preferred embodiment, a piezo ceramic 7 is arranged on the mirror 6, by means of which piezo ceramic 7 the cavity length of both resonant cavities is adjusted simultaneously.
Similarly to the arrangement described in CN2019109431848, by changing the positions of the laser light sources and the polarization beam splitter prism, the output position of the output light can be changed by making the laser light emitted from the plurality of laser light sources a plurality of coherent light beams (including a small part of vertically polarized light) polarized in the horizontal direction, and finally obtaining the output light from the second polarization beam splitter prism 3 a.
Experiments prove that by arranging the non-uniform axial static magnetic field, light beams with different wavelengths pass through positions with different magnetic field strengths in the optical filter, and corresponding filtering conditions can be effectively selected for different wavelengths. The transmission spectrum of each wavelength of the invention can obtain a transmission peak, thereby selecting a laser mode for each wavelength and realizing the stable output of the interference-free multi-wavelength laser.
In the invention, the competition of an inner cavity mode is eliminated by plating an antireflection film on the semiconductor laser source, the output frequency of the semiconductor laser source has good immunity to the fluctuation noise of factors such as external environment factors, the working temperature and the working current of the semiconductor laser source, and the laser of each wavelength works on the frequency corresponding to a single transmission peak of the transmission spectrum of the optical filter.
The invention creatively adopts the design that the filter of the non-uniform magnetic field is matched with a plurality of light paths, thereby realizing that a plurality of beams of light can respectively pass through corresponding magnetic field areas on respective light paths without using a beam splitter to obtain different magnetic field strengths, effectively outputting non-atomic resonance multi-wavelength and effectively eliminating interference light. When the magnetic field condition of the atomic gas chamber in the optical filter is changed, the position of the transmission peak corresponding to each wavelength of the optical filter can be changed, so that each selected laser mode is changed, and the tunability of the output wavelength of the interference-free multi-wavelength semiconductor laser is realized.
[ description of the drawings ]
FIG. 1 is a schematic diagram of a CN2019109431848 dual-wavelength laser;
101, a semiconductor laser source; 102. a collimating lens; 105. piezoelectric ceramics; 106. a mirror; 107. a permanent magnet; 108. a second polarization beam splitter prism; 109. a first polarization splitting prism; 110. an atomic gas cell;
FIG. 2 is a schematic diagram of a dual-wavelength laser of the second prior art;
201, a first laser light source; 201a, a second laser light source; 202. a first collimating lens; 202a, a second collimating lens; 206. a mirror; 207. a magnetic field; 208. a polarization splitting prism; 210. an atomic gas cell; 212. outputting light;
FIG. 3 is a transmission spectrum corresponding to 852nm of cesium atoms in a dual wavelength laser implemented using the first and second prior art techniques;
FIG. 4 is a schematic view of a multiwavelength non-atomic resonance Faraday semiconductor laser of embodiment 1 of the present invention;
FIG. 5 is a schematic diagram of a multi-wavelength non-atomic resonance Faraday semiconductor laser device according to embodiment 2 of the present invention;
the method comprises the following steps of 1, a first laser light source; 1a, a second laser light source; 1b, a third laser light source; 2. a first collimating lens; 2a, a second collimating lens; 2b, a third collimating lens; 6. a mirror; 7. a permanent magnet; 8. a first polarization beam splitter prism 8a and a second polarization beam splitter prism; 9. piezoelectric ceramics; 10. an atomic gas cell; 12. a first output laser; 12a, second output laser; 12b, and a third output laser.
FIG. 6A is a transmission spectrum corresponding to 852nm cesium atoms in a multi-wavelength laser according to an embodiment of the present invention;
FIG. 6B is a transmission spectrum corresponding to 780nm rubidium atoms in the multi-wavelength laser according to the embodiment of the invention;
fig. 6C is a transmission spectrum corresponding to 766nm potassium atoms in the multi-wavelength laser according to the embodiment of the invention.
[ detailed description ] embodiments
The following examples serve to illustrate the technical solution of the present invention without limiting it.
Example 1
As shown in fig. 4, the non-atomic resonance faraday semiconductor laser for realizing dual wavelength output includes a laser source, a collimating lens, a first polarization splitting prism 3, an atomic gas cell 4, a permanent magnet 5 for applying an axial static magnetic field to the atomic gas cell 4, a second polarization splitting prism 3a, and a reflecting mirror 6, which are sequentially disposed on a light path, wherein the placement angles of the first polarization splitting prism 3 and the second polarization splitting prism 3a are adjusted so that the positional relationship therebetween is orthogonal.
In order to realize 780nm and 852nm output, the laser is provided with two light paths which respectively correspond to a first laser light source 1 and a second laser light source 1a, the emergent light of the two light paths is two coherent light beams which are polarized in the vertical direction, and a first collimating lens 2 and a second collimating lens 2a are respectively arranged on the emergent light paths of the two light paths. And an antireflection film is plated on the output light end face of each laser light source, and a high-reflection film is plated on the other face of each laser light source.
The atomic cell 4 is filled with cesium atoms, rubidium atoms and argon gas as a buffer gas.
A plurality of permanent magnets 5 are axially arranged outside the atomic gas chamber 4, and a non-uniform axial magnetic field is obtained by adjusting the number of the permanent magnets or the radial position relation of the permanent magnets and the atomic gas chamber, so that the magnetic field intensity of the light path position of the first laser light source 1 is 300 gauss, and the magnetic field intensity of the light path position of the second laser light source 1a is 1100 gauss. And directly measuring the magnetic field intensity of the corresponding position when the atomic gas chamber is not placed by a gauss meter, and adjusting the position or the number of the permanent magnets to obtain the corresponding magnetic field intensity.
During operation, perpendicular direction polarization laser light of 780nm and 852nm emitted by the first laser light source 1 and the second laser light source 1a is collimated into two parallel light beams through the first collimating lens 2 and the second collimating lens 2a respectively, most of the two parallel light beams penetrate through the first polarization splitting prism 3 and are incident to the atomic air chamber 4 as incident light of the rubidium-cesium mixed multi-wavelength atomic filter, and a small part of the two parallel light beams are reflected and output through the first polarization splitting prism 3.
In the primary air chamber, two beams of light obtain different magnetic field strengths on different light paths to perform frequency selection, and the selected frequency components are changed into horizontal polarized light, so that the horizontal polarized light passes through the second polarization beam splitter prism 3a and then reaches the reflecting mirror 6. The mirror 6 reflects the light back to the first laser light source 1 and the second laser light source 1a in opposite directions and on the same optical path, respectively.
The filter transmits only a narrow band of non-atomic resonances at each wavelength, controlled by the magnetic field strength. Two resonant cavities are established between the non-light-emitting end surfaces of the two laser light sources and the reflector, the optical filters select respective resonant wavelengths for the first laser light source 1 and the second laser light source 1a, output lasers 12 and 12a are generated through the resonant cavities, and dual-wavelength lasers without interference light are output from the first polarization splitting prism 3.
Thus, under the condition of 900-1100 Gauss magnetic field, it is verified that the 852nm transmission spectrum of the atomic filter of the embodiment only contains a narrow-band transmission peak without atomic resonance, so that a laser mode is selected for 852nm laser, and stable output of 852nm laser without interference light is realized. Under the condition of 200-300 Gauss magnetic field, the 780nm transmission spectrum of the atomic filter of the embodiment only comprises a non-atomic resonance narrow-band transmission peak, so that a laser mode is selected for 780nm laser, and stable output of the 780nm laser without interference light is realized. The magnetic field condition of the rubidium-cesium mixed multi-wavelength atomic filter is adjusted, the frequency corresponding to the transmission peaks of different wavelengths can be changed, so that different selected laser modes are changed, and the tunability of the output wavelength of the multi-wavelength semiconductor laser is achieved.
As shown in fig. 6A, the 852nm transmission spectrum of the cesium atom has a frequency on the abscissa and a transmittance on the ordinate, and as seen from the graph, the 852nm transmission spectrum includes only one narrow band transmission peak which is not resonant with the atom and is located between the ground state F-3 transition and the ground state F-4 transition at the time of 1100 gauss. The 780nm transmission spectrum of rubidium atoms is shown in the graph on the side of fig. 6B, and it is seen from the graph that at a magnetic field of 300 gauss, the 780nm transmission spectrum only comprises a narrow-band transmission peak which is located between two ground state transitions and is not in resonance with atoms.
It can be seen that the 780nm and 852nm non-atomic resonance faraday semiconductor lasers of the present embodiment achieve different wavelength outputs and correspond to the frequencies between the two ground state transitions of 852nm cesium atoms and 780nm rubidium atoms, respectively.
Example 2
A non-atomic resonance faraday semiconductor laser that realizes three-wavelength output, as shown in fig. 5, similarly includes a laser light source, a collimator lens, a first polarization splitting prism 3, an atomic gas cell 4, and a permanent magnet 5, a second polarization splitting prism 3a, and a reflecting mirror 6 that are sequentially disposed on an optical path, and apply an axial static magnetic field to the atomic gas cell 4, wherein the placement angles of the first polarization splitting prism 3 and the second polarization splitting prism 3a are adjusted so that their positional relationships are orthogonal.
In order to realize the output of 780nm, 852nm and 766nm, the laser is provided with three light paths which respectively correspond to a first laser light source 1, a second laser light source 1a and a third laser light source 1b, the output of the three light paths is three coherent light beams polarized in the vertical direction, and a first collimating lens 2, a second collimating lens 2a and a third collimating lens 2b are respectively arranged on the light path of the emergent light of the three light paths. And an antireflection film is plated on the output light end face of each laser light source, and a high-reflection film is plated on the other face of each laser light source.
The atomic cell 4 is filled with cesium atoms, rubidium atoms, potassium atoms, and argon gas as a buffer gas.
A plurality of permanent magnets 5 are axially arranged outside the atomic gas chamber 4, and a non-uniform axial magnetic field is obtained by adjusting the number of the permanent magnets or the radial position relation of the permanent magnets and the atomic gas chamber, so that the magnetic field intensity of the light path position of the first laser light source 1 is 300 gauss, the magnetic field intensity of the light path position of the second laser light source 1a is 1100 gauss, and the magnetic field intensity of the light path position of the second laser light source 1b is 800 gauss. And directly measuring the magnetic field intensity of the corresponding position without placing the atomic gas chamber by a gauss meter so as to adjust the position or the number of the permanent magnets.
When the laser device works, 780nm, 852nm and 766nm lasers emitted by the first laser source 1, the second laser source 1a and the third laser source 1b are collimated into three beams of parallel light through the first collimating lens 2, the second collimating lens 2a and the third collimating lens 2b respectively, most of the three beams of parallel light are transmitted through the first polarization beam splitter prism 3 to be incident to the atomic gas chamber 4 and serve as incident light of the multi-wavelength atomic filter mixed with potassium, rubidium and cesium, and less of the three beams of parallel light are reflected and output through the first polarization beam splitter prism 3.
Similarly, in the atomic cell, the three beams of light are frequency-selected on different optical paths through positions of different magnetic field strengths, and the selected frequency components are changed into horizontally polarized light, thereby passing through the second polarization splitting prism 3a and then reaching the reflecting mirror 6. The mirror 6 reflects the light back to the first laser light source 1, the second laser light source 1a, and the third laser light source 1b in opposite directions and on the same optical path, respectively.
The filter transmits only a narrow band of non-atomic resonances at each wavelength. Three resonant cavities are established between the non-light-emitting end surfaces of the three laser light sources and the reflecting mirrors, the optical filters select respective resonant wavelengths for the first laser light source 1, the second laser light source 1a and the third laser light source 1b, output lasers 12, 12a and 12b are generated through the resonant cavities, and multi-wavelength lasers without interference light are output from the first polarization splitting prism 3.
Thus, under the condition of 700-900 Gaussian magnetic field, the 766nm transmission spectrum of the atomic filter of the embodiment only contains a narrow-band transmission peak without atomic resonance, so that a laser mode is selected for 766nm laser, and stable output of 766nm laser without interference light is realized. Under the condition of 900-1100 Gauss magnetic field, it is verified that the 852nm transmission spectrum of the atomic filter of the embodiment only contains a non-atomic resonance narrow-band transmission peak, so that a laser mode is selected for 852nm laser, and stable output of 852nm laser without interference light is realized. Under the condition of 200-300 Gauss magnetic field, the 780nm transmission spectrum of the atomic filter of the embodiment only comprises a non-atomic resonance narrow-band transmission peak, so that a laser mode is selected for 780nm laser, and stable output of the 780nm laser without interference light is realized. The magnetic field condition of the potassium, rubidium and cesium mixed multi-wavelength atomic filter is adjusted, so that the frequencies corresponding to the transmission peaks with different wavelengths can be changed, different selected laser modes are changed, and the tunability of the output wavelength of the multi-wavelength semiconductor laser is realized.
The 766nm transmission spectrum of potassium atoms is shown in fig. 6C, where the abscissa is frequency and the ordinate is transmittance, and it can be seen that the 766nm transmission spectrum contains only one narrow-band transmission peak, which is not an atomic resonance, at a magnetic field of 800 gauss. The 852nm transmission spectrum for cesium atoms and the 780nm transmission spectrum for rubidium atoms were the same as those of example 1, as shown in FIGS. 6A and 6B.
It can be seen that the 780nm, 852nm and 766nm nonatomic resonance faraday semiconductor laser of the present embodiment realizes a three-wavelength output and corresponds to the frequencies of potassium atoms 766nm, cesium atoms 852nm and rubidium atoms 780nm nonatomic resonance, respectively.
The invention realizes the multi-wavelength semiconductor laser by matching the multi-light-path structure with the radial non-uniform magnetic field for the first time, ensures that the magnetic field intensity on each light path corresponds to the magnetic field intensity required by the corresponding wavelength transmission spectrum of the Faraday atomic filter, which only comprises a non-atomic resonance transmission peak, thereby eliminating interference light and outputting non-atomic resonance multi-wavelength Faraday laser.
It should be noted that the present invention is not limited to the use of laser diodes as gain media, but also includes other solid gain media with an antireflection coating on the facet. The invention is not limited to rubidium, cesium and potassium atoms, and is also applicable to all other possible spectral lines such as 894nm, 795nm, 770nm and the like corresponding to various alkali metal atom filters based on different magnetic fields and having a single transmission peak.
Claims (9)
1. The multi-wavelength non-atomic resonance Faraday semiconductor laser comprises a laser source, a collimating lens, a Faraday atomic filter and a reflecting mirror (6) which are sequentially arranged on a light path, wherein the Faraday atomic filter comprises a first polarization beam splitter prism (3), an atomic gas chamber (4), a permanent magnet (5) for applying an axial static magnetic field to the atomic gas chamber (4) and a second polarization beam splitter prism (3a), and the first polarization beam splitter prism (3) and the second polarization beam splitter prism (3a) are orthogonal in position relation;
the laser source is characterized by comprising a first laser light source (1) and a second laser light source (1a), emergent light of the first laser light source (1) and emergent light of the second laser light source (1a) are two beams of coherent light beams polarized in the vertical direction, the collimating lens comprises a first collimating lens (2) and a second collimating lens (2a), the first collimating lens (2) is arranged on an emergent light path of the first laser light source (1), and the second collimating lens (2a) is arranged on an emergent light path of the second laser light source (1 a);
the atomic gas chamber (4) contains a first alkali metal atom and a second alkali metal atom;
the permanent magnet (5) applies a static magnetic field to the atomic gas chamber (4), so that the magnetic field strength in the atomic gas chamber (4) is uniformly distributed in the axial direction and is non-uniformly distributed in the radial direction, a first magnetic field strength on an emergent light path of the first laser light source (1) corresponds to the magnetic field strength required by a first wavelength transmission spectrum of the Faraday atomic filter, which only comprises one non-atomic resonance transmission peak, and a second magnetic field strength on an emergent light path of the second laser light source (1a) corresponds to the magnetic field strength required by a second wavelength transmission spectrum of the Faraday atomic filter, which only comprises one non-atomic resonance transmission peak;
two beams of polarized light in the vertical direction emitted by a first laser light source (1) and a second laser light source (1a) are collimated into a first parallel light and a second parallel light respectively through a first collimating lens (2) and a second collimating lens (2a), most of the parallel light passes through the first polarization beam splitter prism (3), and a small part of the parallel light is reflected and output by the first polarization beam splitter prism (3), the parallel light passes through the first polarization beam splitter prism (3) and enters the atom air chamber (4), then is subjected to frequency selection under a first magnetic field strength to obtain first frequency emergent light, passes through the second polarization beam splitter prism (3a), is reflected back to the first semiconductor laser source (1) by the reflector (6), oscillates and amplifies in a resonant cavity formed between the non-emergent end surface of the first semiconductor laser source (1) and the reflector (6) until the resonant frequency exceeds a laser oscillation threshold, and first output light (8) is output from the first polarization beam splitter prism (3);
meanwhile, second polarized light penetrating through the first polarization splitting prism (3) enters the atomic gas chamber (4) and is subjected to frequency selection under the second magnetic field intensity to obtain second frequency emergent light, the second frequency emergent light penetrates through the second polarization splitting prism (3a) and is reflected back to the second semiconductor laser source (1a) by the reflector (6), the second frequency emergent light is oscillated and amplified in a resonant cavity formed between the non-light-emitting end face of the second semiconductor laser source (1a) and the reflector (6) until the oscillation threshold of the laser is exceeded, and second output light (8a) is output from the first polarization splitting prism (3).
2. A multi-wavelength non-atomic resonance faraday semiconductor laser as claimed in claim 1, characterized in that the first or second alkali metal atoms are selected from potassium atoms, rubidium atoms, cesium atoms and the first alkali metal atoms are different from the second alkali metal atoms.
3. The multi-wavelength non-atomic resonance faraday semiconductor laser as claimed in claim 1, wherein the first alkali metal atom is rubidium atom, the first magnetic field strength is 200 and 300 gauss, and the wavelength corresponding to the first transmission spectrum is 780 nm; the second alkali metal atom is cesium atom, the second magnetic field strength is 900-1100 gauss, the wavelength corresponding to the second transmission spectrum is 852nm, and the temperature of the atomic gas chamber is 50-70 ℃.
4. A multi-wavelength non-atomic resonance faraday semiconductor laser according to claim 1, characterized in that the laser source further comprises a third laser light source (1b), the outgoing light of the first laser light source (1), the second laser light source (1a) and the third laser light source (1b) is three coherent light beams polarized in the vertical direction, a third collimating lens (2b) is arranged on the outgoing light path of the third laser light source (1b), the collimating lens further comprises a third collimating lens (2 b); the three parallel beams respectively pass through a first polarization beam splitter prism (3) and then reach an atomic gas chamber (4); the atomic gas chamber (4) contains a third alkali metal atom, and the third alkali metal atom is different from the first alkali metal atom or the second alkali metal atom; and a third magnetic field intensity on an emergent light optical path of the third laser light source (1b) corresponds to the magnetic field intensity required by a third wavelength transmission spectrum of the Faraday atomic filter, wherein the third wavelength transmission spectrum only comprises one non-atomic resonance transmission peak.
5. A multi-wavelength non-atomic-resonance faraday semiconductor laser according to claim 1, characterized in that the atomic gas cell (4) is filled with a buffer gas.
6. A multi-wavelength non-atomic resonance Faraday semiconductor laser according to claim 5, characterized in that the buffer gas is selected from argon, xenon or helium.
7. A multiwavelength non-atomic resonance Faraday semiconductor laser according to claim 1 or 4, characterized in that the output light end faces of the first (1), second (1a) and third (1b) laser light sources are coated with antireflection coating.
8. A multiwavelength non-atomic resonance faraday semiconductor laser according to claim 1, characterized in that a piezoelectric ceramic (7) is arranged on the mirror (6), the cavity length of the resonant cavity being adjusted by means of the piezoelectric ceramic (7).
9. A multiwavelength non-atomic resonance Faraday semiconductor laser according to claim 1 or 4, wherein the laser beam emitted by changing the position of the laser source contains a small amount of horizontally polarized light, and when the laser oscillation reaches a threshold, the output light is finally obtained from the first polarization splitting prism (3).
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