CN115047637B - Broadband beam-splitting crystal birefringent multi-wavelength space optical bridge - Google Patents
Broadband beam-splitting crystal birefringent multi-wavelength space optical bridge Download PDFInfo
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- G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
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- G02B27/1006—Beam splitting or combining systems for splitting or combining different wavelengths
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Abstract
The broadband beam splitting crystal double-refraction multi-wavelength space optical bridge comprises an achromatic 1/4 wave plate, a first achromatic 1/2 wave plate and a second achromatic 1/2 wave plate which have the same structure, a broadband flat beam splitter, a first double-refraction optical flat plate and a second double-refraction optical flat plate which have the same structure; the main section of the first birefringent optical flat plate is parallel to the fast axis or the slow axis of the first achromatic 1/2 wave plate, the main section of the second birefringent optical flat plate is parallel to the fast axis or the slow axis of the second achromatic 1/2 wave plate, the achromatic 1/4 wave plate can perform multi-wavelength phase control, a composite beam of a signal beam and a local oscillation laser beam space with a plurality of wavelengths with a relative phase difference of 90 degrees is output, and the first achromatic 1/2 wave plate and the second achromatic 1/2 wave plate are used for adjusting the splitting ratio of the output beam. The utility model has the advantages of realizing multi-wavelength optical mixing, along with simple structure, flexible adjustment of phase and splitting ratio, easy integration of the extinction ratio of the birefringent crystal, and no image distortion of emergent light.
Description
Technical Field
The utility model relates to the technical field of coherent laser radar and the field of free space laser coherent communication, in particular to the phase adjustment of spatially compounded multi-wavelength output light in a multi-wavelength coherent laser receiving system by utilizing an achromatic 1/4 wave plate, the spatial mixing of signal beams and local oscillation beams with multiple wavelengths is carried out by utilizing a broadband flat-plate beam splitter, the flexible adjustment of the beam splitting ratio can be realized by double achromatic 1/2 wave plates, the input composite beams can be divided into beams with mutually perpendicular polarization states for output by two birefringent optical flat plates, the phase relation of the finally output four paths of composite beams can be adjusted by rotating the achromatic 1/4 wave plate and the achromatic 1/2 wave plate, and the 2X 4 spatial light mixing with 90-degree phase shift can be generated according to requirements.
Background
The coherent detection technology is an important technical means of a laser radar system and is also widely applied to an optical communication system. The coherent communication system has important application in an inter-satellite laser communication system which needs large capacity, high code rate and low power consumption. Compared with an intensity modulation direct detection laser communication system, the coherent optical communication system has the advantages that the receiving sensitivity of the system is improved by more than one order of magnitude, and the communication quality is obviously improved. The coherent detection technology adopting balanced detection can effectively inhibit the influence of common mode noise and local oscillator relative intensity noise on weak signal detection, improve anti-interference capability, improve sensitivity of coherent detection by 10-25 dB compared with direct detection sensitivity under the same condition, and remarkably improve detection capability.
One of the key components of the optical bridge as a laser radar coherent detection receiving system and a coherent optical communication system is to mix the local oscillation laser and the signal laser and generate a required phase relation to be linked into an optical receiver. The existing optical bridge is mainly divided into an optical fiber type, a waveguide type and a space type according to the structure. For the detection of free space optical signals, the optical fiber bridge has the problems of coupling loss of space light to optical fibers and crosstalk between emitted signal light and echo signals, and the transmission loss of different wavelengths in the optical fibers is different, so that the optical fiber bridge is not suitable for a multi-wavelength receiving system.
The existing scheme [1] (see document 1:Reiner B.Garreis, "90 ° optical hybrid for coherent receivers", proc. Spie, vol.1522, pp.210-219,1991) adopts a scheme of a 2×4 spatial optical bridge in which a non-polarizing beam splitter and a wave plate realize a 90 ° phase shift, but this scheme cannot realize adjustment of the splitting ratio, nor can realize multi-wavelength optical mixing. The existing scheme [2] (see document 2: liu Liren; Aimin; luan Zhu; liu Dean; sun Jianfeng; wang Lijuan; zhong Xianggong) birefringent free-space optical bridge, patent publication No. CN1844960A, patent publication No. CN 2899300Y) adopts the natural birefringence effect of the crystal and a wave plate to realize beam splitting and phase shifting, but the beam splitting ratio and phase cannot be accurately compensated. In the prior art [3] (see document 3: liu Liren; liu Dean; Aimin; luan Zhu; wang Lijuan; sun Jianfeng; zhong Xianggong, the utility model patent, publication No. CN 1844961A) adopts natural birefringence and electro-optical effect of crystals to realize optical mixing and phase shift, and the phase can be precisely controlled by adjusting the voltage, but the phase difference generated by different wavelengths is different under the same voltage due to the fact that the electro-optical effect is related to the wavelength, the multi-wavelength same-phase shift mixing cannot be realized, and in addition, each wafer needs to be applied with voltage and up to hundred volts during phase control, so that the process is complex. The existing scheme [4] (see document 4: mo Lingyu; liu Liren; photinia fraseri; zhou; sun Jianfeng; xu Nan; Aimin, utility model patent, publication number: CN 201464714U) can rotate the dual-wave plate to achieve phase control, but cannot compensate for the variation in the spectral ratio introduced by the rotating wave plate, thereby reducing SNR. The prior scheme [5] (see document 5: zhaoyi; xue Bin; ma Xiaolong; yang Jianfeng; li Ting; he Yinggong; li Fu; xuangzhou, a free space 90 DEG optical mixer, utility model patent publication No. CN 104297936A) adopts an improved transverse shearing interferometer to realize polarization beam splitting, and the output light beam is subjected to multiple reflection and transmission, so that the phase difference is difficult to ensure, the loss of light energy is increased, and the method is not applicable to a multi-wavelength radar system. The existing scheme [6] (see document 6: mo Lingyu; liu Liren; phoebe, zhou; sun Jianfeng; xu Nan; Aimin, utility model patent, CN 101561560A) can rotate the dual-band plate to realize phase control, but has the disadvantage that the light splitting ratio cannot be adjusted, and multi-wavelength broadband light mixing and phase shifting cannot be realized. In the prior art [7] (see document 7: mo Lingyu; liu Liren; sun Jianfeng; zhou; phoebe-making; luan Zhu, patent of the utility model, CN 101706616A), a birefringent crystal plate with different combinations is adopted to perform spectral synthesis on signal light and local oscillation light respectively, and the applied voltage is controlled to perform phase control, so that the optical path self-compensation and the phase independent control are possible. The prior scheme [8] (see document 8: hou Peipei; photinia, sun Jianfeng; liu Liren, free space 2 x 4 optical bridge, utility model patent, CN 102866510B) adopts polarizing beam splitter, wave plate and pentagonal prism to realize optical mixing and phase shift, and can fine tune the interval between the two beams, but cannot realize optical mixing of multiple wavelengths. In the conventional scheme [9] (see document 9: ke Xizheng; han Jianlou, high-performance crystal type 90-degree space optical bridge, utility model patent, CN110244470 a), the natural birefringence effect of the crystal and wave plate are adopted to realize light splitting and phase shifting, but when light of a plurality of wavelengths is input, as the beam off angle of o light and e light in the crystal is related to the wavelength, the deviation of the beam emitting position exists in the beam splitting and combining process, the beam splitting and combining of different wavelengths cannot be realized, and the mixing efficiency is low. The prior art scheme [10] (see document 10:Jiali Wu,Xizheng Ke,Deqiang Ding,Shangjun Yang, "Design of 90-deg hybrid based on birefringent crystal for coherent optical communication system", optical Engineering,60 (4), 045106 (2021)) uses a birefringent optical plate and a wave plate to implement a 2 x 4 spatial optical bridge with a 90 ° phase shift, and since the beam angles of the o-light and e-light in the crystal are wavelength dependent, multi-wavelength mixing and splitting cannot be implemented when multi-wavelength input, and since an achromatic wave plate is not used, the same phase shift for multiple wavelengths cannot be implemented.
In a multi-wavelength coherent receiving system, the existing scheme adopts the same number of optical 90-degree mixers and photoelectric balance detectors with the same wavelength at a receiving end, and has the defects of complex system structure, high cost and the like. The existing scheme does not realize the ultra-wideband multi-wavelength 90-degree phase shift space optical mixing function.
Therefore, the utility model introduces an optical bridge with a space structure, which has the main function of accurately synthesizing a signal laser wave front and a local oscillator laser wave front in space so as to generate a difference frequency component of the signal laser wave front and the local oscillator laser wave front. The system can be suitable for multi-wavelength laser radar receiving systems and multi-wavelength free space coherent optical communication systems in the aspects of atmospheric aerosol detection, terrain detection, ocean detection, laser countermeasure and the like.
Disclosure of Invention
The utility model aims to overcome the defects of the prior art and provide a broadband beam splitting crystal birefringence multi-wavelength space optical bridge which can be used for a multi-wavelength coherent laser radar receiving system and multi-wavelength free space laser coherent communication and has the advantages of being capable of realizing multi-wavelength optical mixing, simple in structure, flexible in phase and beam splitting ratio adjustment, easy to integrate in the extinction ratio of the birefringence crystal, and basically free of image distortion of emergent light. The method is suitable for the field of coherent laser radar detection and the field of free space optical communication.
The technical scheme of the utility model is as follows:
the device is characterized in that the device can be used for a multi-wavelength coherent laser receiving system and comprises an achromatic 1/4 wave plate, a first achromatic 1/2 wave plate, a second achromatic 1/2 wave plate, a broadband flat plate beam splitter, a first birefringent optical flat plate and a second birefringent optical flat plate, wherein the surface of the broadband flat plate beam splitter forms 45 degrees with the surface of the achromatic 1/4 wave plate, and the surface of the broadband flat plate beam splitter is used as two incident surfaces, namely a first incident surface and a second incident surface and also used as two emergent surfaces, namely a first emergent surface and a second emergent surface 12.
The first achromatic 1/2 wave plate, the achromatic 1/4 wave plate, the first incidence surface, the first emergence surface and the first birefringent optical plate of the broadband plate beam splitter are sequentially arranged along the first beam advancing directions of different wavelengths, and the second achromatic 1/2 wave plate, the second incidence surface, the second emergence surface and the second birefringent optical plate of the broadband plate beam splitter are sequentially arranged along the second beam advancing directions of different wavelengths. The main section of the first birefringent optical flat plate is parallel to the fast axis or the slow axis of the first achromatic 1/2 wave plate, and the main section of the second birefringent optical flat plate is parallel to the fast axis or the slow axis of the second achromatic 1/2 wave plate.
The broadband beam splitting crystal birefringent multi-wavelength space optical bridge is characterized in that 90-degree phase shift optical mixing of a plurality of wavelength input beams can be realized simultaneously or in a time-sharing manner.
The broadband flat beam splitter splits an incident beam into two beams with equal energy.
The achromatic 1/4 wave plate, the first achromatic 1/2 wave plate and the second achromatic 1/2 wave plate have phase retardation which can be approximately flat in the whole working wavelength range.
The fast axis or the slow axis of the achromatic 1/4 wave plate, the first achromatic 1/2 wave plate and the second achromatic 1/2 wave plate are provided with a rotating mechanism taking incident light as a central axis.
The achromatic 1/4 wave plate, the first achromatic 1/2 wave plate and the second achromatic 1/2 wave plate are wave plates with the same materials and the same dimensions.
The first birefringent optical flat plate and the second birefringent optical flat plate are formed by uniaxial birefringent crystal flat plates, and the incident surface and the emergent surface of the first birefringent optical flat plate and the second birefringent optical flat plate are optical polished surfaces.
The uniaxial birefringent crystal is calcite, yttrium vanadate or lithium niobate crystal.
The first birefringent optical flat plate and the second birefringent optical flat plate are replaced by two devices with polarization splitting capability such as broadband polarization beam splitting prisms with the same materials and structures, and space light mixing with the same function can be realized.
The utility model discloses a broadband beam splitting crystal birefringence multi-wavelength space optical bridge, which adopts a broadband flat beam splitter to realize the beam splitting synthesis of two input light beams, adopts an achromatic 1/4 wave plate to realize 90-degree phase shift, and uses a birefringent optical flat plate to split linear polarized light with mutually perpendicular vibration directions of a plurality of wavelengths to generate four light beams with 90-degree relative phase difference. The phase error between output beams caused by processing and assembly errors is further compensated by adjusting the included angles of the fast axis and the X axis of the achromatic 1/4 wave plate and the first achromatic 1/2 wave plate. The splitting ratio between the output beams can be adjusted by changing the angle between the fast axis and the X-axis of the first achromatic 1/2 wave plate or the second achromatic 1/2 wave plate.
Compared with the prior art, the utility model has the following technical effects:
1. unlike available spatial light bridge capable of realizing optical mixing phase shift in relatively narrow bandwidth, the present utility model can realize optical mixing of several wavelengths in relatively wide spectrum range simultaneously or in different time, and has obviously lowered complexity and cost and raised performance.
2. Different from the mixing beam splitting function of the existing space optical bridge, the utility model adopts the unpolarized broadband beam splitter to realize the mixing beam splitting of the incident light beam, and utilizes the crystal birefringence effect to realize the polarization beam splitting, thereby having the characteristics of high extinction ratio and easy integration.
3. Unlike available spatial light bridge with difficult phase and splitting ratio regulation, the present utility model provides flexible phase control and splitting ratio control of multi-wavelength output beam. The fast axis or the slow axis of the achromatic 1/4 wave plate and the first achromatic 1/2 wave plate are respectively rotated by taking the incident light as the axis, and the phase relation between the output light beams can be respectively adjusted; the fast axis or the slow axis of the first achromatic 1/2 wave plate and the second achromatic 1/2 wave plate are respectively rotated by taking the incident light as the axis, the split ratio between the output light beams can be adjusted, and meanwhile, the complex problem of the phase control process is also overcome.
Drawings
FIG. 1 is a schematic diagram of a broadband beam splitter crystal birefringent multiple wavelength spatial optical bridge according to example 1 of the present utility model.
Fig. 2 is a schematic view of the crystal optical axis orientation and beam deviation in the principal section of the birefringent optical plate.
Fig. 3 is a schematic structural diagram of an embodiment 2 of a broadband beam-splitting crystal birefringent multi-wavelength spatial optical bridge according to the present utility model.
Detailed Description
The present utility model will be described in further detail with reference to the drawings and examples, which should not be construed as limiting the scope of the utility model. It will be apparent that the described embodiments are only some, but not all, embodiments of the utility model. 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.
The terms first, second and the like in the description and in the claims and in the above-described figures, are used for distinguishing between different objects and not necessarily for describing a sequential or chronological order. Furthermore, the terms "comprise" and "have," as well as any variations thereof, are intended to cover a non-exclusive inclusion. For example, a process, method, system, article, or apparatus that comprises a list of steps or elements is not limited to only those steps or elements but may include other steps or elements not expressly listed.
Referring to fig. 1, the structure of an embodiment 1 of the broadband beam splitter of the present utility model includes an achromatic 1/4 wave plate 3, a first achromatic 1/2 wave plate 4, a second achromatic 1/2 wave plate 5, a broadband plate beam splitter 6, a first birefringent optical plate 7, and a second birefringent optical plate 8 as shown in fig. 1. Wherein: the input light is of wavelength lambda i First beam 1 and second beam 2 of (i=1, 2), the output light is four groups of beams: group one: beam 13, group two: beam 14 and beam 17, group three: beam 15, group four: beam 16 and beam 18. The broadband flat beam splitter 6 has a first entrance face 9 and a second entrance face 10, and a first exit face 11 and a second exit face 12. The first achromatic 1/2 wave plate 4 is placed in front of the achromatic 1/4 wave plate 3, the achromatic 1/4 wave plate 3 is placed in front of the first entrance face 9 of the broadband plate beam splitter 6, and the second achromatic 1/2 wave plate 5 is placed in front of the second entrance face 10 of the broadband plate beam splitter 6. The fast axis or slow axis of all wave plates can rotate with the incident light as the axis. The first birefringent optical plate 7 is located behind the first exit face 11 of the broadband plate beamsplitter 6 and the second birefringent optical plate 8 is located behind the second exit face 12 of the broadband plate beamsplitter 6.
The first birefringent optical plate 7 and the second birefringent optical plate 8 are uniaxial crystal optical plates, the incident surface and the emergent surface of which are perpendicular to the light traveling direction are optical polished surfaces, the crystal optical axis orientation is θ, and the included angle between the normal direction of o light waves and the optical axis is defined. The principal cross section of the birefringent optical plate is the common plane in which the crystal optical axis, o-ray and e-ray are located. The fast or slow axes of the achromatic 1/4 wave plate 3 and the first achromatic 1/2 wave plate 4 are parallel to the main section of the first birefringent optical plate 7, and the fast or slow axes of the second achromatic 1/2 wave plate 5 are parallel to the main section of the second birefringent optical plate 8.
In this embodiment 1, the incident light beam 1 and the incident light beam 2 have a wavelength λ 1 And lambda (lambda) 2 The local oscillation light 1 and the echo signal light 2 of the broadband plate beam splitter 6 are incident at 45 degrees along the direction perpendicular to the two incident surfaces of the broadband plate beam splitter 6, the local oscillation light 1 sequentially passes through a first achromatic 1/2 wave plate 4, an achromatic 1/4 wave plate 3, the broadband plate beam splitter 6 and a first birefringent optical plate 7 or a first broadband polarization beam splitter prism 7, and the echo signal light 2 sequentially passes through a second achromatic 1/2 wave plate 5, the broadband plate beam splitter 6 and a second birefringent optical plate 8 or a second broadband polarization beam splitter prism 8. The fast axis and the X axis of the first achromatic 1/2 wave plate 4 are 0 degrees, the incident local oscillation light 1 is horizontal polarized light through the first achromatic 1/2 wave plate 4, the fast axis and the X axis of the achromatic 1/4 wave plate 3 are 45 degrees, and the incident local oscillation light 1 is circularly polarized light. The fast axis and X-axis angle of the second achromatic 1/2 wave plate 5 is 22.5 degrees, the polarization direction of the incident echo signal light 2 forms 45 degrees with the X-axis through the second achromatic 1/2 wave plate 5, and the local oscillation light 1 and the signal light 2 are respectively subjected to light splitting and beam combining through the broadband flat-plate beam splitter 6. The beam splitting amounts after passing through the first birefringent optical plate 7 or the first broadband polarization beam splitter prism 7 and the second birefringent optical plate 8 or the second broadband polarization beam splitter prism 8 are equal, and finally four paths of output optical signals with equal light intensity and 90-degree phase difference can be obtained.
In embodiment 1, the local oscillation light and the signal light are linearly polarized light, and the polarization direction is set to be horizontal polarization. Let the incident wavelength lambda i The optical vectors of the local oscillation light 1 and the echo signal light 2 with i=1 and 2 are respectively as follows：
Local oscillation light 1:
echo signal light 2:
wherein: a is that S ，A L Complex amplitude phi of echo signal light and local oscillation light respectively so For the initial phase difference of the signal light at the input end of the optical bridge, phi (t) is the phase modulation of the signal light Lo For initial phase difference of local oscillation light, theta Lo The vibration direction of the incident local oscillation light is at an angle of 0 DEG and theta with the X-axis s The vibration direction of the incident signal light is at an angle of 0 DEG to the X-axis.
After passing through the first achromatic 1/2 wave plate 4, the achromatic 1/4 wave plate 3, and the second achromatic 1/2 wave plate 5, respectively, become:
wherein: beta 1 Is the angle between the fast axis and the X axis of the second achromatic 1/2 wave plate 5 and beta 1 ＝22.5°，β 2 Is the angle between the fast axis and the X axis of the first achromatic 1/2 wave plate 4 and beta 2 ＝0°，β 3 Is the angle between the fast axis and X axis of achromatic 1/4 wave plate 3 and beta 3 ＝45°。
The light field coming out from the first outgoing surface 11 and the second outgoing surface 12 after passing through the broadband flat beam splitter 6 is:
wherein: r is (r) ⊥ 、r || ，t ⊥ 、t || Broadband flat beam splitter reflection and transmission coefficients, ρ, respectively ⊥ 、ρ || ，τ ⊥ 、τ || The phase changes in reflection and transmission of the broadband plate beam splitter 6, respectively. In the ideal case of a combination of the above-mentioned,
in this embodiment 1, the main section of the first birefringent optical plate 7 and the fast or slow axis of the achromatic 1/4 wave plate 3 or the first achromatic 1/2 wave plate 4 are placed in parallel, and the main section of the second birefringent optical plate 8 and the fast or slow axis of the second achromatic 1/2 wave plate 5 are placed in parallel. Thus, the light intensity expressions of the four light fluxes outputted from the first birefringent optical plate 7 and the second birefringent optical plate 8 are respectively:
the formula is as follows:
beta will be 1 ＝22.5°，β 2 ＝0°，β 3 ＝45°，θ Lo ＝0°，θ s ＝0°，Carrying into (7), (8), (9) and (10) to obtain:
wherein I is I (λ i ) And I Q (λ i ) Is a phase difference of:
I I (λ i ) And I Q (λ i ) Ratio of maximum light intensity output (spectral ratio):
thus, the broadband beam splitting crystal birefringent multi-wavelength space optical bridge can be realized.
As can be seen from equation (17), I I (λ i ) And I Q (λ i ) The phase difference between the optical axis of the achromatic 1/4 wave plate and the X-axis 3 And an included angle beta between the optical axis of the first achromatic 1/2 wave plate and the X axis 2 Included angle theta between polarization direction of local oscillation light and X axis Lo Related to the following. As can be seen from equation (18), I I (λ i ) And I Q (λ i ) The included angle beta between the ratio of the maximum light intensity and the optical axis of the first achromatic 1/2 wave plate and the X axis 1 Included angle beta between optical axis and X-axis of achromatic 1/4 wave plate 3 The included angle beta between the optical axis of the second achromatic 1/2 wave plate and the X axis 2 Included angle theta between polarization direction of signal light and X-axis s Included angle theta between polarization direction of local oscillation light and X axis Lo The reflection and transmission coefficients of the broadband flat beam splitter and the reflection and transmission coefficients of the broadband polarization beam splitter prism.
Fine tuning of the included angle beta between the optical axis of the achromatic 1/4 wave plate and the X-axis 3 So that is beta 3 =45++δ, and fine tuning the angle β between the optical axis of the first achromatic 1/2 wave plate and the X-axis 2 So that is beta 2 =0++ε. By selecting proper delta and epsilon, the relative phase difference between the output light beams can be adjusted by rotating the included angle between the fast axis of the achromatic 1/4 wave plate and the X axis and the included angle between the fast axis of the first achromatic 1/2 wave plate and the X axis, so as to compensate the phase deviation between the output light beams caused by errors in the processing and assembling processes, and meanwhile, the required output light beam splitting ratio can be obtained. In addition, the beam splitting ratio between the output beams can also be adjusted by rotating the included angle between the fast axis and the X axis of the second achromatic 1/2 wave plate. Due to the design of the achromatic wave plate, the wavelength in the working band can simultaneously realize the phase difference and the splitting ratio of the wanted output light beam. Therefore, the broadband beam splitting crystal birefringence multi-wavelength space optical bridge has the function of flexibly adjusting the output phase and the beam splitting ratio of multi-wavelength laser.
In the present utility model, the first birefringent optical plate 7 and the second birefringent optical plate 8 may be cut by a single piece of birefringent optical plate according to thickness, wherein a schematic view of the crystal optical axis orientation and beam deviation in the main section of the birefringent optical plate is shown in fig. 2. Typically, in order to obtain a large beam deviation angle, a beam deviation maximization design is used.
When light is perpendicularly incident on the crystal interface, the optical axis orientation of the light-wave birefringent optical flat-plate crystalAnd the angle of departure of the light beam->The relation between the two is:
the corresponding beam separation distance is:
where D is the length of the birefringent optical plate along the o-ray propagation.
At maximum off angle, for negative axis crystals, the optical axis orientation is:
corresponding maximum deviation angle
Corresponding maximum separation distance
In this example 1, the first birefringent optical plate 7 and the second birefringent optical plate 8 use yttrium alum (YVO 4) crystals and are arranged at a wavelength λ 1 The maximum beam deviation design is adopted.
In this example 1, two wavelengths of input light, λ 1 1550nm, lambda 2 1064nm. The diameters of the first beam 1 and the second beam 2 are taken to be phi 3mm. The achromatic 1/4 wave plate 3, the first achromatic 1/2 wave plate 4 and the second achromatic 1/2 wave plate 5 have the same size and structure, and consist of three quartz wave plates and three magnesium fluoride (MgF 2) wave plates, and the working wavelength range of the three quartz wave plates and the three magnesium fluoride (MgF 2) wave plates is 600-2700nm through optical adhesive, and the size of the three quartz wave plates is phi 25.4mm. The broadband plate beam splitter 6 splits beams according to a splitting ratio of 50:50, the working wavelength is 600-1700nm, the size is phi 25.4mm, the structural sizes of the first birefringent optical plate 7 and the second birefringent optical plate 8 are identical, and the broadband plate beam splitter is formed by cutting a whole calcite birefringent optical plate according to thickness. The dispersion equation of yttrium alum (YVO 4) crystal is used for calculating the wavelength lambda 1 (1550 nm) principal refractive index n o ＝1.9447，n e = 2.1486 at wavelength λ 2 A principal refractive index at (1064 nm) of n o ＝1.9571，n e The dimensions of the birefringent optical plate 7 and the birefringent optical plate 8 were designed to be length×width×height=40 mm×20mm, = 2.1650, and the optical axis was oriented to beFinally, the output beams 13 and 14, 15 and 16 are separated by 3.9946mm, the output beams 13 and 17, 15 and 18 are separated by 4.044mm, and the separation between the two wavelengths e is 0.0494mm.
Referring to fig. 3, a structure of an embodiment 2 of a broadband beam splitter crystal birefringent multi-wavelength spatial optical bridge according to the present utility model is shown in fig. 3. This embodiment differs from embodiment 1 in that the first birefringent optical plate 7 and the second birefringent optical plate 8 in fig. 1 are replaced with the first broadband polarization beam splitter prism 7 and the second broadband polarization beam splitter prism 8, and spatial light mixing with the same function can be achieved.
The above embodiments are only for illustrating the technical solution of the present utility model, and are not limiting; although the utility model has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present utility model.
Claims (8)
1. A broadband beam splitting crystal double-refraction multi-wavelength space optical bridge is used for a multi-wavelength coherent laser receiving system and is characterized by comprising an achromatic 1/4 wave plate (3), a first achromatic 1/2 wave plate (4), a second achromatic 1/2 wave plate (5), a broadband flat beam splitter (6), a first double-refraction optical flat plate (7) and a second double-refraction optical flat plate (8);
the first light beams (1) with different wavelengths are transmitted through the first achromatic 1/2 wave plate (4) and the achromatic 1/4 wave plate (3) in sequence, then are incident to a first incidence surface (9) of the broadband flat beam splitter (6), are emitted through a first emission surface (11) of the broadband flat beam splitter (6), and then are incident to the first birefringent optical flat plate (7);
the second light beams (2) with different wavelengths are transmitted through the second achromatic 1/2 wave plate and then are incident to the second incidence surface (10) of the broadband flat beam splitter (6), are emitted through the second emission surface (12) of the broadband flat beam splitter (6) and then are incident to the second birefringent optical flat plate (8);
the first incident surface (9) of the broadband flat beam splitter (6) forms 45 degrees with the surface of the achromatic 1/4 wave plate (3), the main section of the first birefringent optical flat plate (7) is parallel to the fast axis or the slow axis of the first achromatic 1/2 wave plate (4), and the main section of the second birefringent optical flat plate (8) is parallel to the fast axis or the slow axis of the second achromatic 1/2 wave plate (5);
the fast axis or the slow axis of the achromatic 1/4 wave plate (3), the first achromatic 1/2 wave plate (4) and the second achromatic 1/2 wave plate (5) are provided with a rotating mechanism taking incident light as a central axis.
2. The broadband beam splitter crystal birefringent multi-wavelength spatial optical bridge according to claim 1, wherein 90 ° phase shifted optical mixing of the multiple wavelength input beams is achieved simultaneously or time-division.
3. The broadband beam splitter crystal birefringent multi-wavelength spatial optical bridge according to claim 1, wherein the broadband plate beam splitter (6) splits the incident beam into two beams of equal energy.
4. The broadband beam splitter crystal birefringent multi-wavelength spatial optical bridge according to claim 1, wherein the achromatic 1/4 waveplate (3), the first achromatic 1/2 waveplate (4), and the second achromatic 1/2 waveplate (5) have a phase retardation that is flat across the entire operating wavelength range.
5. The broadband beam splitter crystal birefringent multi-wavelength spatial optical bridge according to claim 1, wherein the achromatic 1/4 waveplate (3), the first achromatic 1/2 waveplate (4), and the second achromatic 1/2 waveplate (5) are waveplates of the same material and the same size.
6. The broadband beam splitter crystal birefringent multi-wavelength space optical bridge according to claim 1, wherein the first birefringent optical plate (7) and the second birefringent optical plate (8) are formed by uniaxial birefringent crystal plates, and the incident surface and the exit surface of the first birefringent optical plate (7) and the second birefringent optical plate (8) are optical polished surfaces.
7. The broadband beam splitter crystal birefringent multi-wavelength space optical bridge according to claim 6, wherein said uniaxial birefringent crystal is calcite, yttrium vanadate or lithium niobate crystal.
8. The broadband beam splitter crystal birefringent multi-wavelength spatial optical bridge according to claim 1, wherein the first birefringent optical plate (7) and the second birefringent optical plate (8) are replaced by two broadband polarization beam splitting prisms of the same material and structure, so that spatial optical mixing with the same function can be achieved.
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