CN102985870A - Depolarizer - Google Patents
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- CN102985870A CN102985870A CN201180008637XA CN201180008637A CN102985870A CN 102985870 A CN102985870 A CN 102985870A CN 201180008637X A CN201180008637X A CN 201180008637XA CN 201180008637 A CN201180008637 A CN 201180008637A CN 102985870 A CN102985870 A CN 102985870A
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- G—PHYSICS
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- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
- G02B27/28—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00 for polarising
- G02B27/286—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00 for polarising for controlling or changing the state of polarisation, e.g. transforming one polarisation state into another
Abstract
The invention discloses a depolarizer includes a light splitting film, and a light guiding module and a polarization rotator provided at the same side of the light splitting film. The reflective index of the light splitting film is 25%~43%. The light splitting film can split the incident lightinto a first reflected light and a first transmitted light at an incidence point. The light splitting film is not perpendicular to the incident light. The light guiding module can guide the first transmitted light back to the incidence point. The polarization rotator is provided in the light path between the light splitting film and the light guiding module; the polarization state of the first transmitted light can be rotated odd times of 90 DEG , and the error margin is +/-22 DEG . By passing through the light splitting film, the first transmitted light which has returned to the incidence point is splitted into a second reflected light and a second transmitted light. The second transmitted light and the first reflected light is combined into an output light. The second reflected light is cycled along the light path of the first transmitted light. The optical path difference between the second transmitted light and the first reflected light is longer than the coherent length of the incident light. The depolarizer can be realized by using less common optical elements, and has the advantages of simple structure, low cost and small volume.
Description
Technical field
The present invention relates to optical device, relate in particular to a kind of secondary color depolarizer.
Background technology
Depolarizer is used for linearly polarized light or ellipse polarisation are converted into the light that hangs down degree of polarization, namely exports light energy even on each polarization direction and distributes.Depolarizer is widely used in the middle of optical fiber communication and the sensing measurement, is used for eliminating the polarization-dependent effects in the optical transmission process or in the detection process.Such as in raman amplifier, flashlight only has could amplify consistent with the pump light polarization direction, and gain is zero when both are vertical, so pump light needs depolarization.The frequency spectrum of laser always has certain width, can regard the secondary color light source as, so the secondary color depolarizer has a wide range of applications.
To the polychromatic light depolarization, the depolarizer of Lyot type is to use one of the most general depolarizer.It is applicable to polychromatic light, can be to arbitrarily line polarisation, ellipse polarisation depolarization.The depolarization method of this depolarizer is based on the phase delay disperse by depolarizer time of different wave length bundle, thereby realizes the principle of depolarization at wavelength domain.Incident light with different wave length, by producing different phase delay behind the birefringence device, emergent light becomes the elliptically polarized light with different ellipse inclined to one side rates, and whole light beam is exactly the synthetic of this random state, makes output light present the depolarization characteristic.This depolarizer is in series by two birefringence devices, and the birefringence device can realize also can realizing with polarization maintaining optical fibre that with wave plate the thickness of two devices (or length) ratio is 2:1, and the angle of feature axis is miter angle.The shortcoming of Lyot depolarizer is that volume is large, and such as the 1480nm raman pump light, bandwidth is 1nm, and the Lyot depolarizer is wanted panda protecting polarized light fiber more than 20 meters at least, or could realize low degree of polarization above 10 centimetres lithium columbate crystal.And birefringece crystal or polarization maintaining optical fibre are all relatively more expensive.
Also useful one section birefringece crystal or polarization maintaining optical fibre produce phase delay, as the day for announcing be January 8, notification number in 2003 Chinese patent that is CN2530368Y " a kind of polarisation of light closes ripple and depolarized hybrid device ".Although this depolarizer lacks with birefringece crystal or polarization maintaining optical fibre than the Lyot depolarizer, volume is point also, can only be to specific polarization state depolarization.If need in the system a plurality of laser instrument depolarizations, then volume and cost do not have advantage.And it still will use birefringece crystal or polarization maintaining optical fibre, and cost is not cheap yet.
Summary of the invention
The technical problem to be solved in the present invention is for complex structure in the prior art, volume is large and cost is high defective, and a kind of simple in structure, volume is little and cost is low depolarizer is provided.
The technical solution adopted for the present invention to solve the technical problems is: provide a kind of depolarizer, the leaded light component and the polarization optically-active device that comprise spectro-film and be arranged on described spectro-film the same side; Wherein,
The reflectivity of described spectro-film is 25% ~ 43%, at the incidence point place incident light is divided into the first reflected light and the first transmitted light, and spectro-film is not orthogonal to incident light;
Described leaded light component leads back to described incidence point with described the first transmitted light;
Described polarization optically-active device is arranged on the light path between described spectro-film and the described leaded light component, and with the odd-multiple of the polarization state half-twist of described the first transmitted light, error margin is+/-22 °;
Wherein satisfy:
Be back to the first transmitted light of described incidence point by forming the second reflected light and the second transmitted light behind the described spectro-film; Described the second transmitted light spatially overlaps with described first reflected light of homonymy, merges into the part of output light; Described the second reflected light enters circulation along the light path of described the first transmitted light;
Described the second transmitted light and the described first catoptrical optical path difference are greater than the coherent length of incident light.
In the depolarizer of the foundation embodiment of the invention, described leaded light component comprises two catoptrons that become angle, is back to described incidence point after the reflection of described the first transmitted light by two described catoptrons.
In the depolarizer of the foundation embodiment of the invention, two described catoptrons are respectively level crossing and concave mirror.
In the depolarizer of the foundation embodiment of the invention, described leaded light component comprise catoptron and be arranged on described spectro-film and described catoptron between condenser lens; Described spectro-film and described catoptron lay respectively on the object plane and picture plane of described condenser lens both sides; Described the first transmitted light by described condenser lens refraction and the reflection of catoptron after be back to described incidence point.
In the depolarizer of the foundation embodiment of the invention, described condenser lens is GRIN Lens, and length is 0.49 pitch; Catoptron is made of deielectric-coating, directly is plated in GRIN Lens away from that end face of spectro-film; And the light inlet side at spectro-film also has a double-fiber collimator, and the exiting surface of collimating apparatus is towards spectro-film.
In the depolarizer of the foundation embodiment of the invention, described leaded light component comprise catoptron and be arranged on described catoptron and described spectro-film between the rhombus wedge, described the first transmitted light by described rhombus wedge refraction and the reflection of catoptron after be back to described incidence point.
In the depolarizer of the foundation embodiment of the invention, described catoptron is level crossing or concave mirror.
In the depolarizer of the foundation embodiment of the invention, described leaded light component is the isosceles triangle wedge, and the bottom surface of described isosceles triangle wedge is parallel with described spectro-film; Described the first transmitted light is reflected back described incidence point by the central plane that waits of described isosceles triangle wedge.
In the depolarizer of the foundation embodiment of the invention, described polarization optically-active device is gyrotropi crystal or chiral liquid crystal or magnetic rotation device.
In the depolarizer of the foundation embodiment of the invention, when described polarization optically-active device was gyrotropi crystal, described gyrotropi crystal was quartzy optical rotation plate.
In the depolarizer of the foundation embodiment of the invention, when described polarization optically-active device was the magnetic rotation device, described magnetic rotation device was the faraday rotator with magnetic tube.
The beneficial effect that the present invention produces is: the present invention utilizes spectro-film the polarized light of incident to be divided into the infinite multi beam of strength decrease, by the optically-active device each is restrainted the polarization state different rotation angle, at last with guiding device all light beams are combined output again, so that output light distributes in the energy even of all directions polarization, reach the effect of depolarization.Depolarization principle of the present invention is simple, only has spectro-film, leaded light component and polarization optical rotation plate in the structure of depolarizer, and is therefore simple in structure and cost is low; In addition, the optical path difference that only need to satisfy two-beam on the structure of depolarizer gets final product greater than coherent length, so volume is little.
Description of drawings
The invention will be further described below in conjunction with drawings and Examples, in the accompanying drawing:
Fig. 1 is the structural representation according to the depolarizer of the embodiment of the invention 1;
Fig. 2 is the structural representation according to the depolarizer of the embodiment of the invention 2;
Fig. 3 is the structural representation according to the depolarizer of the embodiment of the invention 3;
Fig. 4 is the structural representation according to the depolarizer of the embodiment of the invention 4;
Fig. 5 is the structural representation according to the depolarizer of the embodiment of the invention 5;
Fig. 6 is the structural representation according to the depolarizer of the embodiment of the invention 6;
Fig. 7 is the structural representation according to the depolarizer of the embodiment of the invention 7;
Fig. 8 is the structural representation according to the depolarizer of the embodiment of the invention 8;
Embodiment
In order to make purpose of the present invention, technical scheme and advantage clearer, below in conjunction with drawings and Examples, the present invention is further elaborated.Should be appreciated that specific embodiment described herein only in order to explain the present invention, is not intended to limit the present invention.
As shown in Figure 1, comprise spectro-film 1, leaded light component 2 and polarization optically-active device 3 according to the depolarizer of the embodiment of the invention, leaded light component 2 and polarization optically-active device 3 all are arranged on the same side of spectro-film 1.Wherein, spectro-film 1 selects spectro-film commonly used on the market to get final product, and it is plated to by materials such as silicon dioxide, tantalum oxide and zirconias usually.The reflectivity of spectro-film 1 is 25%～43%, and namely transmitance is 57%～75%, as incident beam I
0(angle for example at a certain angle
) when inciding the incidence point A on the spectro-film 1, a part of light beam forms the first reflected light R at the surface reflection of spectro-film 1
1, reflection angle equates that with incident angle the residue light beam passes spectro-film 1 and forms the first transmitted light T with certain angle of transmission generation transmission
1This moment, the transmission/reflectance of spectro-film 1 was 75: 25～57: 43, and preferred transmission/reflectance is 2: 1, and namely reflectivity is 33.3%.Leaded light component 2 comprises one or more optical device, such as catoptron, wedge and/or condenser lens etc., and concrete structure arranges and will be described in an embodiment.Leaded light component 2 is used for the light beam T that guiding is come in from spectro-film 1 transmission
1By polarization optically-active device 3 and be back to incidence point A on the spectro-film 1, thereby make this light beam finish a light path circulation.Be back to the light beam I of the incidence point A of spectro-film 1
1A part pass spectro-film 1 transmission occur, thereby form the second transmitted light T
2Penetrate (being outgoing beam), this second transmitted light T from spectro-film 1
2The first reflected light R with homonymy
1Synthetic a branch of, the output beam of formation depolarizer; Be back to the light beam I of the incidence point A of spectro-film 1
1Another part reflect to form the second reflected light R
2, and will be under the effect of leaded light component 2 by polarization optically-active device 3 to carry out next time light path circulation, this moment, transmission/reflectance was 75: 25～57: 43 still, was preferably 2: 1.As can be seen from the above, will there be light beam between spectro-film 1, leaded light component 2 and polarization optically-active device 3, constantly to carry out the light path circulation.In the setting up procedure of leaded light component 2, need to satisfy outgoing beam T
2With folded light beam R
1Optical path difference greater than incident light I
0Coherent length, i.e. the light path of light path of transmitted light beam circulation is greater than above-mentioned coherent length, therefore as the first transmitted light T
1Through again transmiting spectro-film 1 after the circulation of light path repeatedly when forming irradiating light beam, itself and folded light beam R
1Optical path difference also inevitable greater than coherent length.Polarization optically-active device 3 is arranged on the light path between spectro-film 1 and the leaded light component 2, can be gyrotropi crystal or chiral liquid crystal or magnetic rotation device, polarization state rotation (90 °+N*180 °+/-22 °) angle that is used for the light beam that to pass through, wherein N is positive integer, in other words, the odd-multiple of the polarization state half-twist of the light beam that will pass through, tolerance be+/-22 °.At this moment, light beam can pass through polarization optically-active device 3 one or many, thereby so that the polarization state anglec of rotation of light beam is different.Simultaneously, number of times and the angle that also should pass through according to light beam are selected the suitable polarization optically-active device with different optically-active angles.
The below will specifically discuss the structure of depolarizer in an embodiment.At first, for leaded light component 2, in first group of embodiment (embodiment 1-3), leaded light component 2 comprises a plurality of catoptrons, and this catoptron is high reflective mirror.Catoptron comprises level crossing and/or concave mirror herein.Polarization optically-active device 3 is wherein between at least one catoptron and the spectro-film 1, and polarization optically-active this moment device 3 for example is gyrotropi crystal or chiral liquid crystal or magnetic rotation device.
Fig. 1 is the structural representation according to the depolarizer of the embodiment of the invention 1.As shown in Figure 1, leaded light component 2 comprises two level crossings 21 and 22 that form an angle, and polarization optically-active device 3 is arranged between spectro-film 1 and two level crossings 21,22.The first transmitted light T
1Process level crossing 21,22 liang of secondary reflections form the light path of isosceles triangle afterwards between spectro-film 1 and leaded light component 2, then be back into exit point A and produce the second reflected light R
2With the second transmitted light T
2The second transmitted light T
2With the first reflected light R
1Spatially overlap, merge into light beam; The second reflected light R
2With the first transmitted light T
1Spatially overlap, along T
1Track constantly circulates.All energy are gone out from spectro-film 1 transmission and are merged into output light at last.
Certainly, leaded light component 2 also can be to adopt other setting, as shown in Figure 2.Fig. 2 is the structural representation according to the depolarizer of the embodiment of the invention 2, wherein, leaded light component 2 comprises level crossing 21 and concave mirror 23, and both are equipped with, so that the light path between spectro-film 1 and the leaded light component 2 is isosceles triangle, thereby transmitted light beam can be back into exit point A.And similar among the setting of polarization optically-active device 3 and the embodiment 1, repeat no more.
Certainly, leaded light component 2 also can comprise the catoptron more than three or three, as shown in Figure 3.Fig. 3 is the structural representation according to the depolarizer of the embodiment of the invention 3, be with the difference of embodiment 1, leaded light component 2 also comprise be arranged on level crossing 21,22 and spectro-film 1 between concave mirror 23, concave mirror 23 and level crossing 21,22 minute surface are in opposite directions.And similar among the setting of polarization optically-active device 3 and the embodiment 1, repeat no more.Only in this structure, the position by polarization optically-active device 3 is set so that light beam by polarization optically-active device 3 twice or three times or four times.Light beam shown in Fig. 3 passes through polarization optically-active device 3 three times back and forth.
In second group of embodiment (embodiment 4 and 5), leaded light component 2 comprises a catoptron and a condenser lens.Catoptron is high reflective mirror, all reflects after the light beam incident, and catoptron is level crossing herein, also can be concave mirror or convex mirror.Condenser lens is arranged between spectro-film 1 and the catoptron, can be GRIN Lens or convex lens.Any position of polarization optically-active device 3 on the light path between spectro-film 1 and the catoptron is as long as light beam can pass through.The device of polarization optically-active herein 3 the bests are the magnetic rotation device.
As shown in Figure 4, leaded light component 2 comprise level crossing 21 and be arranged on level crossing 21 and spectro-film 1 between convex lens 25, spectro-film 1 and level crossing 21 are placed on respectively both sides thing and the position of image place of these convex lens 25, satisfy general lens image formation rule.The light planoconvex lens 25 of spectro-film A point scattering converges at level crossing 21 places, namely images on the level crossing 21.Adjust the angle of level crossing 21, so that the first transmitted light T
1Get back to the A point behind the planoconvex lens 25, form the light path that circulates as previously mentioned.Polarization optically-active device 3 is realized by faraday's sheet 32, and a magnet ring 321 in the outer surface cover of faraday's sheet 32.
Embodiment 5
As shown in Figure 5, the convex lens among Fig. 4 25 are replaced by GRIN Lens 29.The length of GRIN Lens 29 is 0.49 pitch, the refractive index distribution that tapers off along the center of circle, and light is inside as shown in the figure along curve.This external mirror 21 is made of deielectric-coating, and it directly is plated in the end face of GRIN Lens 29.At last, spectro-film 1 also is plated on the collimating apparatus GRIN Lens exiting surface.Faraday's sheet 32 and magnetic tube 321 remain unchanged.Comparison diagram 4 has also been added a double-fiber collimator 4 and has been made the tail fiber type depolarizer.Collimating apparatus 4 is made of GRIN Lens 42 and the stationary installation 43 of two optical fiber 41,0.25 pitch, and stationary installation 43 is formed by a glass capillary and a glass tube bonding usually.The depolarizer incident light is by wherein optical fiber input, and output light (comprises R
1, T
2, T
3, T
4) be coupled into an other optical fiber.Below only having provided several examples, is not limitation of the present invention, and relevant combination is multiple in addition, is not described in detail herein.
In the 3rd group of embodiment, a kind of situation is that leaded light component 2 comprises catoptron and wedge, and wherein wedge is between at least one catoptron and spectro-film 1; Another kind of situation is that leaded light component 2 includes only wedge.The device of polarization optically-active herein 3 is gyrotropi crystal or chiral liquid crystal or magnetic rotation device, and is similar with arranging among the above embodiment, repeats no more.
Embodiment 6
As shown in Figure 6, leaded light component 2 comprise concave mirror 22 and be arranged on spectro-film 1 and concave mirror 22 between rhombus wedge 27.Get back to initial point after the transmission of transmitted light beam process rhombus wedge 27 and the reflection of concave mirror 22, finish a light path circulation.
Embodiment 7
As shown in Figure 7, leaded light component includes only an isoceles triangle glass wedge 26.Wedge 26 is made by transparency material, such as BK7 glass.Two of wedge 26 wait central planes to serve as reflective mirror, and light incides etc. on the central plane total reflection occurs, and waits central plane to play the effect of mirror.Polarization optically-active device is magnetic rotation device 32, between the wedge 26 of spectro-film 1 and far-end, as long as light beam can pass through.
Embodiment 8
As shown in Figure 8, leaded light component includes only an isoceles triangle glass wedge 26.Wedge 26 is made by transparency material, such as BK7 glass.Two of wedge 26 wait central planes to serve as reflective mirror, and light incides etc. on the central plane total reflection occurs, and waits central plane to play the effect of mirror.Polarization optically-active device is made of two gyrotropi crystals 331 and 332.Gyrotropi crystal 331 is opposite with 332 optical directions, and one is levorotatory crystal, and one is right-handed crystal, and both respectively rotate 45 °.Gyrotropi crystal 331 and 332 is between the wedge 26 of spectro-film 1 and far-end, and light with opposite direction respectively by gyrotropi crystal 331,332 once in a circulation.
Certainly, wedge not only can cooperate catoptron to use, and wedge also can cooperate the multiple optical device such as catoptron and/or condenser lens together to use.
As can be seen from the above, leaded light component 2 can comprise a plurality of optical device, by the combination setting to optical device, so that light beam is back on the spectro-film 1 after circulating through a light path.Above embodiment is not limitation of the present invention only as example, and leaded light component 2 can also be the structure setting of other type, therefore on this basis distortion and be equal to all should be within protection scope of the present invention.In actual conditions, from cost with realize angle, should be that structure is the simplest, cost is minimum and the easiest realization for optimum.
For polarization optically-active device 3, take embodiment 1 as example, when adopting quartzy optical rotation plate 31, take the polarization state half-twist of light beam as example, among Fig. 1 light beam by quartzy optical rotation plate once, therefore should select the optically-active angle this moment is 90 ° quartzy optical rotation plate.If light beam respectively by quartzy optical rotation plate once, is then cancelled out each other by rear optically-active effect for twice in the opposite direction, quartzy optical rotation plate does not play a role, and the clean number of pass times that is equivalent to light beam is 0.Again take embodiment 3 as example, the light beam shown in Fig. 3 is by quartzy optical rotation plate 31 3 times, and the clean number of pass times that is equivalent to light beam is 1, and therefore still selecting the optically-active angle is 90 ° quartzy optical rotation plate.Therefore will guarantee in arranging that clean number of pass times that light beam passes through quartzy optical rotation plate greater than zero, for convenience of description, represents k=m-n with clean number of pass times, wherein m and n are nonnegative integer, represent respectively the in the opposite direction number of times by quartzy optical rotation plate of light beam.The optically-active angle of so quartzy optical rotation plate can be expressed as (90 °+N*180 °)/k, if consider tolerance in the middle of the engineering then the optically-active angular range is (90 °+N*180 °-22 °)/k to (90 °+N*180 °+22 °)/k.Certainly, in the present embodiment polarization optically-active device 3 also can be selected chiral crystal or magnetic rotation the device faraday rotator of magnetic tube (for example with), and wherein chiral crystal and gyrotropi crystal are similar, repeat no more.Faraday rotator with magnetic tube is then different, take embodiment 5 as example, when employing during with the faraday rotator 32 of magnetic tube 321, the optically-active angle of faraday rotator 32 can be expressed as (90 °+N*180 °)/(m+n), wherein m and n are nonnegative integer, represent respectively the in the opposite direction number of times by faraday rotator of light beam.If tolerance in the middle of the consideration engineering then optically-active angular range are (90 °+N*180 °-22 °)/(m+n) to (90 °+N*180 °+22 °)/(m+n).For example, take the polarization state half-twist of light beam as example, when light beam secondary (being m+n=2) was by faraday rotator herein, should select the optically-active angle was 45 ° faraday rotator.
Polarization optically-active device discussed above is single assembly, and polarization optically-active device also can be the combination of a plurality of optical rotation plates, for example in embodiment 8.As shown in Figure 8, polarization optically-active device comprises two crystal optical rotation plates, and a slice is levorotatory crystal 331, and a slice is right-handed crystal 332 in addition.Both anglec of rotation sums (not considering direction) are 90 degree, such as left-handed 45 degree dextrorotation, 45 degree; Or left-handed 30 degree dextrorotation, 60 degree etc.And wherein a crystal can also be faraday's sheet, as long as the resultant effect of the two optically-active is 90 degree.
The above is the most basic depolarizer.Among the different embodiment, can also add different parts to satisfy specific application requirements.Need to be with tail optical fiber such as depolarizer in raman amplifier, can add double-fiber collimator in a side of spectro-film and make the tail fiber type depolarizer, as shown in Figure 5.
Take embodiment 1 as example, also described among Fig. 1 according to the light path synoptic diagram in the depolarizer of the embodiment of the invention.Light beam is being carried out in the process of depolarization, initial incident light is with incident angle
Be injected on the spectro-film 1, the transmission angle is β, wherein
β＞0.For convenience of description and identification, incident light is labeled as I
0, the first reflected light is labeled as R
1, the first transmitted light is labeled as T
1
The first transmitted light T
1Leave spectro-film 1 rear the reflection by leaded light component 2 and come back to spectro-film 1, middle polarization optically-active device 3, the polarization state half-twist of seeing through.Through the first transmitted light T behind the polarization optically-active device 3
1Be marked as I
1With the variation of difference polarization state, I
1Get back to spectro-film 1, reflection and transmission occur, thereby finish a light path circulation.The feature of light path circulation: I
1Incident angle be β, and T
1The transmission angle equates; I
1Incidence point and T
1Eye point overlaps, and all is the A point, and I
1, I
1Incident normal and T
1On a plane.I
1By spectro-film 1 rear formation the second folded light beam R
2With the second transmitted light beam T
2Because I
1Incident angle be β, incidence point is the A point, and I
1, I
1Normal and T
1On a plane, so the second transmitted light T
2Will with the first reflected light R
1Spatially overlap and synthetic a branch of the second reflected light R
2Along the first transmitted light T
1Track advance, enter next time the light path circulation, and constantly circulation, thereby I arranged
2, T
3, R
3, I
3, T
4, R
4, I
4, T
5, R
5..., by that analogy.
The principle of work of this novel depolarizer and effect can be derived accurately with multiple-beam interference, but the process more complicated.The below explains the depolarization effect with the coherent length theory, and process simply but do not affect result's accuracy.The structural design of depolarizer guarantees that the light path L that light walks a circulation is longer than the coherent length Lc of incident polarization light source, so in the spectro-film reflection with repeatedly the light that comes of transmission is irrelevant, can not consider that the relation of phase place is directly carried out the power addition.
Take the optimum transmission rate of spectro-film 1 as 2/3 as example, supposing does not all have loss in the light path, and the hypothesis incident light is ellipse polarisation.Ellipse polarisation major axis is X-axis, and the energy of X-direction polarization is a; Minor axis is Y-axis, and Y direction polarization energy is b.Light is whenever advanced one and is circulated, and polarization optically-active device 3 will be the energy exchange of XY direction once, and 2/3 luminous energy is gone out from spectro-film 1 transmission, stays 1/3 and continues circulation.Following table is the luminous energy in the time of each time incident, reflection and transmission.The summation of each beam energy of each output terminal is exactly light energy output in the table 1, the number of times of the subscript i light path circulation that represents to carry out wherein, and for example, i=1 represents to carry out first time light path and circulates.
Table 1
So output light at the energy of X-direction polarization is:
Can draw output light by same calculating at Y direction polarization state energy is:
PY=a/2+b/2 （2）
When b=0, incident light is the line polarisation; When a=b, incident light is rotatory polarization.So formula (1) and (2) can represent any incident polarized light.In addition, incident light is decomposed into X-axis Y-axis component along the fast and slow axis of ellipse polarisation in one section in the above, and the definition of this XY axle not necessarily in fact.The luminous energy of random polarization can be decomposed into arbitrarily two vertical components, and these two vertical direction are X-axis and Y-axis, and two minutes energy are a and b, and still set up above-mentioned analysis and formula (1) and (2) in this case.So the conclusion that integrates is, no matter incident light is line polarisation, ellipse polarisation or rotatory polarization, and the energy of output light on any one polarization direction all is impartial, that is to say that emergent light is dominant without any the polarization direction, successfully realized depolarization.
Yet in the engineering of reality is used, splitting ratio and optically-active angle have no idea to accomplish absolute ideal value 1/3 and 90 ° of equaling, the present invention does not need absolute exact value yet, opposite the present invention has very wide tolerance limit so that can easily realize in the middle of the engineering, thereby has increased reliability and lowered cost.The below will discuss the situation when spectro-film 1 can't accurately reach 90 ° for other reflectivity or optically-active angle in detail.
The depolarization effect of depolarizer can represent that with the output polarization degree its numerical range is [0,1].The complete depolarization of 0 expression, 1 expression does not have depolarization fully, if be 0.1 then expression 10% light or polarized light, can think the effect that reached depolarization less than 20% with interior at degree of polarization.Below adopt the degree of polarization with full polarization state extinction ratio method of testing calculating device.Ultimate principle is linearly polarized light for input light, at output termination analyzer.Constantly adjust the input light polarization direction, light polarization direction is a bit inputted in every change, and analyzer is rotated a circle, and records one group of maximum/minimum analyzer output power.Input light polarization direction Rotate 180 ° is picked out the maximum output intensity I in data the inside
Max, minimum output intensity I
MinThe degree of polarization DOP of device is
(seeing Song Shixia for details, " research of monochromatic light depolarizer and wave plate fevering sodium effect " the 8th page, Qufu Normal University's master thesis, 2009).Do not have birefringent material in the depolarizer of the present invention, so to input light polarization direction isotropy, only need to analyze the analyzer rotation and get final product, analyze in other words that polarized component gets final product on all directions.
At first, when the transmissivity of spectro-film 1 still is best 2/3, but when the optically-active angle can't accurately reach 90 °, suppose incident light I
0Be linearly polarized light, and do not have loss in the light path in the transmission.At this moment, the output light according to the depolarizer of the embodiment of the invention at arbitrarily angled φ polarization state energy is:
Wherein R is the reflectivity of spectro-film 1, and T is the transmissivity of spectro-film 1, and Lr is the first reflected light loss, and Lc is each circulation light loss, and θ is optically-active device rotation angle, and φ is the angle between analyzer and the polarizer.R=0.333 in the analysis herein, T=0.667, Lr=Lc=0.φ is value between 0 to 180 °, can obtain I according to formula (3)
MaxAnd I
MinThereby the degree of polarization DOP when drawing certain optically-active device rotation angle (θ) changes rotation angle θ and obtains following table 2.As can be seen from Table 2, θ is in 68 °-112 ° scope, and DOP is less than 20%, and wherein 90 ° the time, DOP is 0.Certainly, θ also can be in 248 ° ~ 292 ° scopes, and this angle represents to turn clockwise 68 °-112 °, and the depolarization effect that obtains is the same.
Table 2
| θ（°） | 65 | 68 | 75 | 85 | 90 | 95 | 105 | 112 | 115 |
| DOP | 0.228 | 0.198 | 0.132 | 0.044 | 0 | 0.044 | 0.132 | 0.198 | 0.228 |
In addition, when the transmissivity of spectro-film 1 is not best 2/3, but other value, but when the optically-active angle accurately reaches 90 °, suppose incident light I
0Be linearly polarized light, and do not have loss in the light path in the transmission.Can calculate table 3 according to same formula (3).As can be seen from Table 3, when reflectivity R was in 25% to 43% scope, degree of polarization DOP was lower than 0.2, and degree of polarization DOP is minimum near 33.3% left and right sides time, and the depolarization effect is more satisfactory in general.
Table 3
As can be seen from the above, according in the depolarizer of the present invention, employing all be the common optical device such as catoptron, condenser lens and/or wedge, simple in structure, cost is low and volume is little; In addition, can find out that from the principle of depolarizer this depolarizer is applicable to line polarisation, ellipse polarisation or rotatory polarization, and is applied widely.
Should be understood that, for those of ordinary skills, can be improved according to the above description or conversion, and all these improvement and conversion all should belong to the protection domain of claims of the present invention.
Claims (11)
1. a depolarizer is characterized in that, the leaded light component (2) and the polarization optically-active device (3) that comprise spectro-film (1) and be arranged on described spectro-film (1) the same side; Wherein,
The reflectivity of described spectro-film (1) is 25% ~ 43%, and (A) locates incident light (I at incidence point
0) be divided into the first reflected light (R
1) and the first transmitted light (T
1), spectro-film (1) is not orthogonal to incident light (I
0);
Described leaded light component (2) is with described the first transmitted light (T
1) lead back to described incidence point (A);
Described polarization optically-active device (3) is arranged on the light path between described spectro-film (1) and the described leaded light component (2), with described the first transmitted light (T
1) the odd-multiple of polarization state half-twist, error margin is+/-22 °;
Wherein satisfy:
Be back to the first transmitted light (T of described incidence point (A)
1) by forming the second reflected light (R behind the described spectro-film (1)
2) and the second transmitted light (T
2); Described the second transmitted light (T
2) with the described first reflected light (R of homonymy
1) spatially overlap, merge into the part of output light; Described the second reflected light (R
2) along described the first transmitted light (T
1) light path enter circulation;
Described the second transmitted light (T
2) and described the first reflected light (R
1) optical path difference greater than incident light (I
0) coherent length.
2. depolarizer according to claim 1 is characterized in that, described leaded light component (2) comprises two catoptrons that become angle, described the first transmitted light (T
1) be back to described incidence point (A) after the reflection by two described catoptrons.
3. depolarizer according to claim 2 is characterized in that, two described catoptrons are respectively level crossing (21) and concave mirror (23).
4. depolarizer according to claim 1 is characterized in that, described leaded light component (2) comprise catoptron (21) and be arranged on described spectro-film (1) and described catoptron (21) between condenser lens (25); Described spectro-film (1) and described catoptron (21) lay respectively on the object plane and picture plane of described condenser lens both sides; Described the first transmitted light (T
1) be back to described incidence point (A) after the refraction by described condenser lens (25) and the reflection of catoptron (21).
5. depolarizer according to claim 4 is characterized in that, described condenser lens is GRIN Lens (29), and length is 0.49 pitch; Catoptron (21) is made of deielectric-coating, directly is plated in GRIN Lens (29) away from that end face of spectro-film (1); And the light inlet side at spectro-film (1) also has a double-fiber collimator (4), and the exiting surface of collimating apparatus (4) is towards spectro-film (1).
6. depolarizer according to claim 1 is characterized in that, described leaded light component (2) comprise catoptron and be arranged on described catoptron and described spectro-film (1) between rhombus wedge (27), described the first transmitted light (T
1) be back to described incidence point (A) after the refraction by described rhombus wedge (27) and the reflection of catoptron.
7. depolarizer according to claim 6 is characterized in that, described catoptron is level crossing or concave mirror.
8. depolarizer according to claim 1 is characterized in that, described leaded light component (2) is isosceles triangle wedge (26), and the bottom surface of described isosceles triangle wedge (26) is parallel with described spectro-film (1); Described the first transmitted light (T
1) be reflected back described incidence point (A) by the central plane that waits of described isosceles triangle wedge (26).
9. depolarizer according to claim 1 is characterized in that, described polarization optically-active device (3) is gyrotropi crystal or chiral liquid crystal or magnetic rotation device.
10. depolarizer according to claim 9 is characterized in that, when described polarization optically-active device (3) was gyrotropi crystal, described gyrotropi crystal was quartzy optical rotation plate.
11. depolarizer according to claim 9 is characterized in that, when described polarization optically-active device (3) was the magnetic rotation device, described magnetic rotation device was the faraday rotator with magnetic tube.
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| CN106772916A (en) * | 2016-12-14 | 2017-05-31 | 上海伟钊光学科技股份有限公司 | Miniature Faraday speculum |
| CN115903250A (en) * | 2021-09-23 | 2023-04-04 | 曲阜师范大学 | Quartz crystal optical rotation and double refraction polarization independent polychromatic light depolarizer |
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| CN112683796A (en) * | 2020-12-15 | 2021-04-20 | 中国科学院合肥物质科学研究院 | Differential absorption spectrometer optical system based on geosynchronous orbit observation |
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| US6831778B2 (en) * | 2001-12-26 | 2004-12-14 | Wuhan Research I.O.P. And Telecom | Hybrid component and method for combining two pumping lights and depolarizing them simultaneously and optical amplifier therefor |
| US7259914B2 (en) * | 2005-08-30 | 2007-08-21 | Coherent, Inc. | Attenuator for high-power unpolarized laser beams |
| CN101726799A (en) * | 2009-12-22 | 2010-06-09 | 上海大学 | Single degree of freedom optical fiber ring depolarization method |
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| CN1201153A (en) * | 1997-05-01 | 1998-12-09 | 鸿海精密工业股份有限公司 | Optical depolarizing device and method of depolarizing light-beam |
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| US6831778B2 (en) * | 2001-12-26 | 2004-12-14 | Wuhan Research I.O.P. And Telecom | Hybrid component and method for combining two pumping lights and depolarizing them simultaneously and optical amplifier therefor |
| US7259914B2 (en) * | 2005-08-30 | 2007-08-21 | Coherent, Inc. | Attenuator for high-power unpolarized laser beams |
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| CN106772916A (en) * | 2016-12-14 | 2017-05-31 | 上海伟钊光学科技股份有限公司 | Miniature Faraday speculum |
| CN115903250A (en) * | 2021-09-23 | 2023-04-04 | 曲阜师范大学 | Quartz crystal optical rotation and double refraction polarization independent polychromatic light depolarizer |
| CN115903250B (en) * | 2021-09-23 | 2024-04-19 | 曲阜师范大学 | Quartz crystal optical rotation and double refraction polarization independent polychromatic light depolarizer |
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