CN102985870B - Depolarizer - Google Patents
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- CN102985870B CN102985870B CN201180008637.XA CN201180008637A CN102985870B CN 102985870 B CN102985870 B CN 102985870B CN 201180008637 A CN201180008637 A CN 201180008637A CN 102985870 B CN102985870 B CN 102985870B
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- G—PHYSICS
- G02—OPTICS
- 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
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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, particularly relate to a kind of secondary color depolarizer.
Background technology
Depolarizer is used for light linearly polarized light or oval thickness being converted into low degree of polarization, namely exports light energy even distribution on each polarization direction.Depolarizer is widely used in the middle of optical fiber communication and sensing measurement, is used for eliminating the polarization-dependent effects in optical transmission process or in detection process.Such as in raman amplifier, flashlight only has could amplify consistent with pump light polarization direction, and when both are vertical, gain is zero, so pump light needs depolarization.The frequency spectrum of laser always has certain width, can regard secondary color light source as, so secondary color depolarizer has a wide range of applications.
To polychromatic light depolarization, the depolarizer of Lyot type uses one of the most general depolarizer.It is applicable to polychromatic light, can to arbitrary line polarisation, oval thickness depolarization.The depolarization method of this depolarizer is based on the light beam of different wave length by phase delay disperse during depolarizer, thus on wavelength domain, realize the principle of depolarization.Have the incident light of different wave length, by producing different phase delay after birefringence device, emergent light becomes the elliptically polarized light with different ellipse inclined rates, and whole light beam is exactly the synthesis of this random state, makes output light present depolarization characteristic.This depolarizer is in series by two birefringence devices, and birefringence device can realize also can realizing with polarization maintaining optical fibre with wave plate, and thickness (or length) ratio of two devices 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 1480nm raman pump light, bandwidth is that 1nm, Lyot depolarizer at least wants more than 20 meters panda protecting polarized light fibers, or the lithium columbate crystal more than 10 centimetres could realize low degree of polarization.And birefringece crystal or polarization maintaining optical fibre are all costly.
Also useful one section of birefringece crystal or polarization maintaining optical fibre produce phase delay, as the day for announcing be on January 8th, 2003, notification number is the Chinese patent " a kind of polarisation of light closes ripple and depolarized hybrid device " of CN2530368Y.Although this depolarizer is than the few birefringece crystal of Lyot depolarizer or polarization maintaining optical fibre, volume is point also, can only to specific polarization state depolarization.If needed multiple laser instrument depolarization in a system, then volume and cost do not have advantage.And it still will use birefringece crystal or polarization maintaining optical fibre, cost is not cheap yet.
Summary of the invention
The technical problem to be solved in the present invention is for complex structure in prior art, volume is large and cost is high defect, provides that a kind of structure is simple, volume is little and the depolarizer that cost is low.
The technical solution adopted for the present invention to solve the technical problems is: provide a kind of depolarizer, comprises spectro-film and is arranged on leaded light component and the polarization optically-active device of described spectro-film the same side; Wherein,
The reflectivity of described spectro-film is 25% ~ 43%, and incident light is divided into the first reflected light and the first transmitted light at incidence point place, spectro-film is not orthogonal to incident light;
Described first transmitted light is led back to described incidence point by described leaded light component;
Described polarization optically-active device is arranged in the light path between described spectro-film and described leaded light component, and by the odd-multiple of the polarization state half-twist of described first transmitted light, error margin is +/-22 °;
Wherein meet:
Be back to the first transmitted light of described incidence point by forming the second reflected light and the second transmitted light after described spectro-film; Described second transmitted light spatially overlaps with described first reflected light of homonymy, merges into the part exporting light; Described second reflected light enters circulation along the light path of described first transmitted light;
The optical path difference of described second transmitted light and described first reflected light is greater than the coherent length of incident light.
In the depolarizer of the foundation embodiment of the present invention, described leaded light component comprises the catoptron that two become angles, is back to described incidence point after the reflection of described first transmitted light by two described catoptrons.
In the depolarizer of the foundation embodiment of the present invention, two described catoptrons are respectively level crossing and concave mirror.
In the depolarizer of the foundation embodiment of the present invention, described leaded light component comprises catoptron and is arranged on the condenser lens between described spectro-film and described catoptron; Described spectro-film and described catoptron lay respectively at described condenser lens both sides object plane and picture plane on; Described first transmitted light is by being back to described incidence point after the refraction of described condenser lens and the reflection of catoptron.
In the depolarizer of the foundation embodiment of the present invention, described condenser lens is GRIN Lens, and length is 0.49 pitch; Catoptron is made up of deielectric-coating, and direct plating is at GRIN Lens that end face away from spectro-film; And also having a double-fiber collimator in the incident side of spectro-film, the exiting surface of collimating apparatus is towards spectro-film.
In the depolarizer of the foundation embodiment of the present invention, described leaded light component comprises catoptron and is arranged on the rhombus wedge between described catoptron and described spectro-film, and described first transmitted light is by being back to described incidence point after the refraction of described rhombus wedge and the reflection of catoptron.
In the depolarizer of the foundation embodiment of the present invention, described catoptron is level crossing or concave mirror.
In the depolarizer of the foundation embodiment of the present invention, described leaded light component is isosceles triangle wedge, and the bottom surface of described isosceles triangle wedge is parallel with described spectro-film; Described first transmitted light is reflected back described incidence point by the central plane that waits of described isosceles triangle wedge.
According in the depolarizer of the embodiment of the present 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 present invention, when described polarization optically-active device is gyrotropi crystal, described gyrotropi crystal is quartzy optical rotation plate.
According in the depolarizer of the embodiment of the present invention, when described polarization optically-active device is magnetic rotation device, described magnetic rotation device is the faraday rotator of band magnetic tube.
The beneficial effect that the present invention produces is: the present invention utilizes spectro-film the polarized light of incidence to be divided into the infinite multi beam of strength decrease, by optically-active device by each bundle polarization state different rotation angle, finally with guiding device, all light beams are combined output again, make to export light to distribute 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 therefore structure is simple and cost is low; In addition, the optical path difference of structure on the demand fulfillment two-beam of depolarizer is greater than coherent length, and therefore volume is little.
Accompanying drawing explanation
Below in conjunction with drawings and Examples, the invention will be further described, in accompanying drawing:
Fig. 1 is the structural representation of the depolarizer according to the embodiment of the present invention 1;
Fig. 2 is the structural representation of the depolarizer according to the embodiment of the present invention 2;
Fig. 3 is the structural representation of the depolarizer according to the embodiment of the present invention 3;
Fig. 4 is the structural representation of the depolarizer according to the embodiment of the present invention 4;
Fig. 5 is the structural representation of the depolarizer according to the embodiment of the present invention 5;
Fig. 6 is the structural representation of the depolarizer according to the embodiment of the present invention 6;
Fig. 7 is the structural representation of the depolarizer according to the embodiment of the present invention 7;
Fig. 8 is the structural representation of the depolarizer according to the embodiment of the present invention 8;
Embodiment
In order to make object of the present invention, technical scheme and advantage clearly understand, 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, be not intended to limit the present invention.
As shown in Figure 1, the depolarizer according to the embodiment of the present invention comprises spectro-film 1, leaded light component 2 and polarization optically-active device 3, and leaded light component 2 and polarization optically-active device 3 are all arranged on the same side of spectro-film 1.Wherein, spectro-film 1 selects spectro-film conventional on the market, 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(such as angle at a certain angle
) when inciding on spectro-film 1 incidence point A, a part of light beam forms the first reflected light R at the surface reflection of spectro-film 1
1, reflection angle is equal with incident angle, and residue light beam forms the first transmitted light T through spectro-film 1 with certain angle of transmission generation transmission
1.Now transmission/the reflectance of spectro-film 1 is 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 for guiding the light beam T come in from spectro-film 1 transmission
1by polarization optically-active device 3 and the incidence point A be back on spectro-film 1, thus this light beam is made to complete a light path circulation.Be back to the light beam I of the incidence point A of spectro-film 1
1a part there is transmission through spectro-film 1, thus form the second transmitted light T
2penetrate (i.e. outgoing beam) from spectro-film 1, this second transmitted light T
2with the first reflected light R of homonymy
1synthesize a branch of, form the output beam of 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 by under the effect of leaded light component 2 by polarization optically-active device 3 with once light path circulation on carrying out, now transmission/reflectance is still 75: 25 ~ 57: 43, is preferably 2: 1.As can be seen from the above, light beam will be had at spectro-film 1, between leaded light component 2 and polarization optically-active device 3, constantly carry out light path circulation.In the setting up procedure of leaded light component 2, demand fulfillment outgoing beam T
2with folded light beam R
1optical path difference be greater than incident light I
0coherent length, i.e. the light path of transmitted light beam light path circulation is greater than above-mentioned coherent length, therefore as the first transmitted light T
1spectro-film 1 is again transmitted to form outgoing beam, itself and folded light beam R after the circulation of repeatedly light path
1optical path difference also must be greater than coherent length.Polarization optically-active device 3 is arranged in the light path between spectro-film 1 and leaded light component 2, can be gyrotropi crystal or chiral liquid crystal or magnetic rotation device, angle that the polarization state of light beam for passing through rotates (90 °+N*180 ° of +/-22 °), wherein N is positive integer, in other words, by the odd-multiple of the polarization state half-twist of light beam passed through, tolerance is +/-22 °.Now, light beam can pass through polarization optically-active device 3 one or many, thus makes the polarization state anglec of rotation of light beam different.Meanwhile, the number of times that also should pass through according to light beam and angle, select the suitable polarization optically-active device with different optically-active angle.
The structure of depolarizer will be specifically discussed in an embodiment below.First, for leaded light component 2, in first group of embodiment (embodiment 1-3), leaded light component 2 comprises multiple catoptron, 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 spectro-film 1, and now polarization optically-active device 3 is such as gyrotropi crystal or chiral liquid crystal or magnetic rotation device.
Embodiment 1
Fig. 1 is the structural representation of the depolarizer according to the embodiment of the present invention 1.As shown in Figure 1, leaded light component 2 comprises two level crossings 21 and 22 formed an angle, and polarization optically-active device 3 is arranged between spectro-film 1 and two level crossings 21,22.First transmitted light T
1after level crossing 21,22 liang of secondary reflections, between spectro-film 1 and leaded light component 2, be formed as the light path of isosceles triangle, be then back into exit point A and produce the second reflected light R
2with the second transmitted light T
2.Second transmitted light T
2with the first reflected light R
1spatially overlap, merge into light beam; Second reflected light R
2with the first transmitted light T
1spatially overlap, along T
1track constantly circulates.Finally all energy are gone out from spectro-film 1 transmission and are merged into output light.
Embodiment 2
Certainly, leaded light component 2 also can be adopt other to arrange, as shown in Figure 2.Fig. 2 is the structural representation of the depolarizer according to the embodiment of the present invention 2, wherein, leaded light component 2 comprises level crossing 21 and concave mirror 23, and both are equipped with, make the light path between spectro-film 1 and leaded light component 2 be isosceles triangle, thus transmitted light beam can be back into exit point A.And similar in the setting of polarization optically-active device 3 and embodiment 1, repeat no more.
Embodiment 3
Certainly, leaded light component 2 also can comprise the catoptron of more than three or three, as shown in Figure 3.Fig. 3 is the structural representation of the depolarizer according to the embodiment of the present invention 3, and be with the difference of embodiment 1, leaded light component 2 also comprises the concave mirror 23 be arranged between level crossing 21,22 and spectro-film 1, and the minute surface of concave mirror 23 and level crossing 21,22 in opposite directions.And similar in the setting of polarization optically-active device 3 and embodiment 1, repeat no more.Only in such an embodiment, the position by arranging polarization optically-active device 3 makes light beam by polarization optically-active device 3 twice or three times or four times.Light beam shown in Fig. 3 is back and forth through polarization optically-active device 3 three times.
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, and light beam incidence is all reflected afterwards, and catoptron is level crossing herein, also can be concave mirror or convex mirror.Condenser lens is arranged between spectro-film 1 and catoptron, can be GRIN Lens or convex lens.Any position in the light path of polarization optically-active device 3 between spectro-film 1 and catoptron, if light beam by.The device 3 of polarization optically-active herein the best is magnetic rotation device.
Embodiment 4
As shown in Figure 4, leaded light component 2 comprises level crossing 21 and is arranged on the convex lens 25 between level crossing 21 and spectro-film 1, and spectro-film 1 and level crossing 21 are placed on the both sides thing of these convex lens 25 and the position of picture respectively, meet general lens image formation rule.The light planoconvex lens 25 of spectro-film A point scattering converges at level crossing 21 place, namely images on level crossing 21.The angle of adjustment level crossing 21, makes the first transmitted light T
1get back to A point after 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 25 in Fig. 4 are replaced by GRIN Lens 29.The length of GRIN Lens 29 is 0.49 pitch, and refractive index tapers off along the center of circle distribution, and light is inside as shown in the figure along curve.This external mirror 21 is made up of deielectric-coating, and it is by the end face of direct plating in GRIN Lens 29.Finally, spectro-film 1 is also plated on collimating apparatus GRIN Lens exiting surface.Faraday's sheet 32 and magnetic tube 321 remain unchanged.Comparison diagram 4, has also added a double-fiber collimator 4 and has made tail fiber type depolarizer.Collimating apparatus 4 is made up of the GRIN Lens 42 of two optical fiber, 41,0.25 pitch and stationary installation 43, and usual stationary installation 43 is bondd by a glass capillary and a glass tube and forms.Depolarizer incident light, by a wherein optical fiber input, exports light and (comprises R
1, T
2, T
3, T
4) be coupled into an other optical fiber.More than only giving several example, 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 only includes wedge.The device of polarization optically-active herein 3 is gyrotropi crystal or chiral liquid crystal or magnetic rotation device, similar with arranging in the above embodiment, repeats no more.
Embodiment 6
As shown in Figure 6, leaded light component 2 comprises concave mirror 22 and is arranged on the rhombus wedge 27 between spectro-film 1 and concave mirror 22.Transmitted light beam gets back to initial point after the transmission of rhombus wedge 27 and the reflection of concave mirror 22, completes a light path circulation.
Embodiment 7
As shown in Figure 7, leaded light component only includes an isoceles triangle glass wedge 26.Wedge 26 is made by transparency material, as BK7 glass.Two of wedge 26 wait central planes to serve as reflective mirror, and light to incide etc. on central plane and is totally reflected, and waits central plane to play the effect of mirror.Polarization optically-active device is magnetic rotation device 32, between spectro-film 1 and the wedge 26 of far-end, as long as light beam by.
Embodiment 8
As shown in Figure 8, leaded light component only includes an isoceles triangle glass wedge 26.Wedge 26 is made by transparency material, as BK7 glass.Two of wedge 26 wait central planes to serve as reflective mirror, and light to incide etc. on central plane and is totally reflected, and waits central plane to play the effect of mirror.Polarization optically-active device is made up of two panels gyrotropi crystal 331 and 332.Gyrotropi crystal 331 and 332 optical direction is contrary, and one is levorotatory crystal, and one is right-handed crystal, and both respectively rotate 45 °.Gyrotropi crystal 331 and 332 is between spectro-film 1 and the wedge 26 of far-end, and in a circulation, light with contrary direction respectively by gyrotropi crystal 331,332 once.
Certainly, wedge not only can coordinate catoptron to use, and wedge also can coordinate 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 multiple optical device, by arranging the combination of optical device, light beam is back on spectro-film 1 after a light path circulation.Above embodiment is only used as example, and be not limitation of the present invention, leaded light component 2 can also be the vibrational power flow of other type, therefore distortion on this basis and equivalent all should within protection scope of the present invention.In a practical situation, from cost and realize angle, should be that structure is the simplest, cost is minimum and the most easily realize for optimum.
For polarization optically-active device 3, for embodiment 1, when adopting quartzy optical rotation plate 31, for the polarization state half-twist of light beam, in Fig. 1, light beam by quartzy optical rotation plate once, and optically-active angle therefore now should be selected to be the quartzy optical rotation plate of 90 °.If in the opposite direction respectively by quartzy optical rotation plate once, then pass twice through rear optically-active effect and cancel out each other, quartzy optical rotation plate does not play a role light beam, and the clean number of pass times being equivalent to light beam is 0.Again for the light beam shown in embodiment 3, Fig. 3 by quartzy optical rotation plate 31 3 times, the clean number of pass times being equivalent to light beam is 1, therefore still selects optically-active angle to be the quartzy optical rotation plate of 90 °.Therefore will guarantee in arranging that light beam is greater than zero by the clean number of pass times of quartzy optical rotation plate, for convenience of description, represents k=m-n by clean number of pass times, wherein m and n is nonnegative integer, represents the number of times of light beam in opposite directions through quartzy optical rotation plate respectively.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 engineering, optically-active angular range is that (90 °+N*180 °-22 °)/k is to (90 °+N*180 °+22 °)/k.Certainly, the device of polarization optically-active in the present embodiment 3 also can select chiral crystal or magnetic rotation device (faraday rotator such as with magnetic tube), wherein chiral crystal and gyrotropi crystal similar, repeat no more.Faraday rotator with magnetic tube is then different, for embodiment 5, when adopting the faraday rotator 32 of band magnetic tube 321, the optically-active angle of faraday rotator 32 can be expressed as (90 °+N*180 °)/(m+n), wherein m and n is nonnegative integer, represents the number of times of light beam in opposite directions through faraday rotator respectively.If tolerance in the middle of consideration engineering, optically-active angular range is that (90 °+N*180 °-22 °)/(m+n) is to (90 °+N*180 °+22 °)/(m+n).Such as, for the polarization state half-twist of light beam, when light beam secondary (i.e. m+n=2) is by faraday rotator, optically-active angle should be selected to be the faraday rotator of 45 ° herein.
Polarization optically-active device discussed above is single assembly, and polarization optically-active device also can be the combination of multiple optical rotation plate, such as, in embodiment 8.As shown in Figure 8, polarization optically-active device comprises two panels crystal optical rotation plate, 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, as left-handed 45 degree of dextrorotation 45 degree; Or left-handed 30 degree of dextrorotation 60 degree etc.And wherein one piece of 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.In different embodiments, different parts can also be added and specifically apply requirement to meet.Such as in raman amplifier, depolarizer needs to be with tail optical fiber, can add double-fiber collimator and make tail fiber type depolarizer, as shown in Figure 5 in the side of spectro-film.
Further depict in embodiment 1, Fig. 1 according to the light path schematic diagram in the depolarizer of the embodiment of the present invention.Carrying out in the process of depolarization light beam, initial incident light is with incident angle
to be injected on spectro-film 1, transmission angle is β, wherein
β > 0.For convenience of description and identify, 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.
First transmitted light T
1spectro-film 1 is come back to by leaded light component 2 reflection after leaving spectro-film 1, middle through polarization optically-active device 3, polarization state half-twist.Through the first transmitted light T after polarization optically-active device 3
1be marked as I
1to distinguish the change of polarization state, I
1get back to spectro-film 1, reflection and transmission occur, thus complete a light path circulation.The feature of light path circulation: I
1incident angle be β, and T
1transmission angle is equal; I
1incidence point and T
1eye point overlaps, and is all A point, and I
1, I
1incident normal and T
1on a plane.I
1by forming the second folded light beam R after spectro-film 1
2with the second transmitted light beam T
2.Due to I
1incident angle be β, incidence point is A point, and I
1, I
1normal and T
1on a plane, therefore the second transmitted light T
2will with the first reflected light R
1spatially overlap and synthesize a branch of, the second reflected light R
2along the first transmitted light T
1track advance, enter light path circulation next time, and constantly to circulate, thus have I
2, T
3, R
3, I
3, T
4, R
4, I
4, T
5, R
5..., by that analogy.
Principle of work and the effect of this novel depolarizer can be derived accurately with multiple-beam interference, but process more complicated.Explain depolarization effect by coherent length theory below, process simply but do not affect the accuracy of result.It is longer than the coherent length Lc of incident polarization light source that the structural design of depolarizer ensures that light walks the light path L of a circulation, thus spectro-film reflection and the light that repeatedly transmission comes irrelevant, can not consider that the relation of phase place directly carries out power addition.
For the optimum transmission rate of spectro-film 1 for 2/3, suppose all there is no loss in light path, and hypothesis incident light is oval thickness.Oval thickness major axis is X-axis, and the energy of X-direction polarization is a; Minor axis is Y-axis, and Y direction resonance energy is b.Light is often advanced one and is circulated, and polarization optically-active device 3 will the energy exchange in XY direction once, and 2/3 luminous energy is gone out from spectro-film 1 transmission, leaves 1/3 continuation circulation.Following table is the luminous energy when each incident, reflection and transmission.In table 1, the summation of each beam energy of each output terminal is exactly light energy output, and wherein subscript i represents the number of times of carried out light path circulation, and such as, i=1 represents that carrying out first time light path circulates.
Table 1
So exporting light at the energy of X-direction polarization is:
Can show that exporting light at Y direction polarization state energy is by calculating equally:
PY=a/2+b/2 （2）
As b=0, incident light is line polarisation; As a=b, incident light is rotatory polarization.Institute with the formula (1) and (2) can represent any incident polarized light.In addition, above, in one section, incident light is decomposed into X-axis Y-axis component along the fast and slow axis of oval thickness, and the definition of this XY axle not necessarily in fact.The luminous energy of random polarization can be decomposed into two vertical arbitrarily components, and these two vertical direction are X-axis and Y-axis, and two points of energy are a and b, and above-mentioned analysis and formula (1) and (2) are still set up in this case.So the conclusion integrated is, no matter incident light is line polarisation, oval thickness or rotatory polarization, and it is all impartial for exporting the energy of light on any one polarization direction, and that is emergent light is dominant without any polarization direction, successfully achieves depolarization.
But in the engineer applied of reality, splitting ratio and optically-active angle have no idea to accomplish absolute to equal ideal value 1/3 and 90 °, the present invention does not need absolute exact value yet, contrary the present invention has very wide tolerance limit and makes can easily realize in the middle of engineering, thus adds reliability and reduce cost.The following will discuss when spectro-film 1 be other reflectivity or optically-active angle accurately cannot reach 90 ° time situation.
The depolarization effect of depolarizer can represent with output polarization degree, and its numerical range is [0,1].0 represents complete depolarization, and 1 represents do not have depolarization completely, if be 0.1, represents light or the polarized light of 10%, is less than can thinks the effect reaching depolarization within 20% 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, is exporting termination analyzer.Continuous adjustment input light polarization direction, often changes and a bit inputs light polarization direction, rotated a circle by analyzer, record one group of maximum/minimum analyzer output power.Input light polarization direction rotates 180 °, picks out maximum output intensity I inside data
max, minimum output intensity I
minthe degree of polarization DOP of device is
(referring to Song Shixia, " research of monochromatic light depolarizer and wave plate fevering sodium effect " the 8th page, Qufu Normal University's master thesis, 2009).Birefringent material is not had, so to input light polarization direction isotropy, only Water demand analyzer rotates, and in other words analyzes polarized component in all directions in depolarizer of the present invention.
First, when the transmissivity of spectro-film 1 is still 2/3 of the best, but when optically-active angle accurately cannot reach 90 °, incident light I is supposed
0for linearly polarized light, and there is not loss in light path in transmission.Now, the output light according to the depolarizer of the embodiment of the present 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, T=0.667, Lr=Lc=0 in analysis herein.φ is value between 0 to 180 °, can obtain I according to formula (3)
maxand I
min, thus degree of polarization DOP when drawing certain optically-active device rotation angle (θ), change rotation angle θ obtains following table 2.As can be seen from Table 2, θ is in the scope of 68 °-112 °, and DOP is less than 20%, wherein 90 ° time, DOP is 0.Certainly, θ also can within the scope of 248 ° ~ 292 °, and this angle represents and turns clockwise 68 °-112 °, and the depolarization effect obtained 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 2/3 of the best, but other value, but when optically-active angle accurately reaches 90 °, suppose incident light I
0for linearly polarized light, and there is not loss in light path in transmission.Table 3 can be calculated according to same formula (3).As can be seen from Table 3, when reflectivity R is in the scope of 25% to 43%, degree of polarization DOP is lower than 0.2, and close about 33.3% time, degree of polarization DOP is minimum, and depolarization effectiveness comparison is desirable in general.
Table 3
As can be seen from the above, according in depolarizer of the present invention, employing be all the conventional optical devices such as catoptron, condenser lens and/or wedge, structure is simple, cost is low and volume is little; In addition, as can be seen from the principle of depolarizer, this depolarizer is applicable to line polarisation, oval thickness or rotatory polarization, applied widely.
Should be understood that, for those of ordinary skills, can be improved according to the above description or convert, and all these improve and convert the protection domain that all should belong to claims of the present invention.
Claims (11)
1. a depolarizer, is characterized in that, comprises spectro-film (1) and is arranged on leaded light component (2) and the polarization optically-active device (3) of described spectro-film (1) the same side; Wherein,
The reflectivity of described spectro-film (1) is 25% ~ 43%, at incidence point (A) place by incident light (I
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 by described first transmitted light (T
1) lead back to described incidence point (A);
Described polarization optically-active device (3) is arranged in the light path between described spectro-film (1) and described leaded light component (2), by described first transmitted light (T
1) the odd-multiple of polarization state half-twist, error margin is +/-22 °;
Wherein meet:
Be back to the first transmitted light (T of described incidence point (A)
1) form the second reflected light (R afterwards by described spectro-film (1)
2) and the second transmitted light (T
2); Described second transmitted light (T
2) with the described first reflected light (R of homonymy
1) spatially overlap, merge into the part exporting light; Described second reflected light (R
2) along described first transmitted light (T
1) light path enter circulation;
Described second transmitted light (T
2) and described first reflected light (R
1) optical path difference be greater than incident light (I
0) coherent length.
2. depolarizer according to claim 1, is characterized in that, described leaded light component (2) comprises the catoptron that two become angle, described first transmitted light (T
1) be back to described incidence point (A) after reflection by two described catoptrons.
3. depolarizer according to claim 2, is characterized in that, two described catoptrons are respectively level crossing and concave mirror (23).
4. depolarizer according to claim 1, it is characterized in that, described leaded light component (2) comprises catoptron (21) and is arranged on the condenser lens (25) between described spectro-film (1) and described catoptron (21); Described spectro-film (1) and described catoptron (21) lay respectively at described condenser lens both sides object plane and picture plane on; Described first transmitted light (T
1) by being back to described incidence point (A) after the refraction of 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 up of deielectric-coating, and direct plating is at GRIN Lens (29) that end face away from spectro-film (1); And also having a double-fiber collimator (4) in the incident side of spectro-film (1), the exiting surface of collimating apparatus (4) is towards spectro-film (1).
6. depolarizer according to claim 1, it is characterized in that, described leaded light component (2) comprises catoptron and is arranged on the rhombus wedge (27) between described catoptron and described spectro-film (1), described first transmitted light (T
1) by being back to described incidence point (A) after the refraction of 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, it 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 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) is for gyrotropi crystal, described gyrotropi crystal is quartzy optical rotation plate.
11. depolarizers according to claim 9, is characterized in that, when described polarization optically-active device (3) is for magnetic rotation device, described magnetic rotation device is the faraday rotator of band magnetic tube.
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| 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 |
| CN2530368Y (en) * | 2001-12-26 | 2003-01-08 | 武汉邮电科学研究院 | Mixed component of light polarized composite wave and depolarization |
| 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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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| 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 |
| CN2530368Y (en) * | 2001-12-26 | 2003-01-08 | 武汉邮电科学研究院 | Mixed component of light polarized composite wave and depolarization |
| 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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