CN110568625B - Polarization-adjustable laser beam-expanding collimator - Google Patents
Polarization-adjustable laser beam-expanding collimator Download PDFInfo
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- CN110568625B CN110568625B CN201910759281.1A CN201910759281A CN110568625B CN 110568625 B CN110568625 B CN 110568625B CN 201910759281 A CN201910759281 A CN 201910759281A CN 110568625 B CN110568625 B CN 110568625B
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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
- G02B27/09—Beam shaping, e.g. changing the cross-sectional area, not otherwise provided for
- G02B27/0938—Using specific optical elements
- G02B27/095—Refractive optical elements
- G02B27/0955—Lenses
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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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- 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
- G02B27/30—Collimators
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/005—Optical devices external to the laser cavity, specially adapted for lasers, e.g. for homogenisation of the beam or for manipulating laser pulses, e.g. pulse shaping
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Abstract
In order to overcome the defect that the polarization of an input laser beam cannot be accurately regulated and maintained by the existing beam expansion collimator, the invention provides the polarization-adjustable laser beam expansion collimator for a magneto-optical trap, an optical trap and other structural cold atom physical experiment systems, and a polarization prism and a slide, the polarization axes of which can be independently and accurately regulated, are arranged in a light path, so that the polarization state of a light beam input by a polarization maintaining optical fiber can be accurately regulated and maintained, fluctuation of laser power is reduced, the polarization state change of an emergent light beam caused by the polarization maintaining optical fiber is eliminated, and the requirement of high-quality ultra-cold atom preparation is met.
Description
Technical Field
The invention relates to a polarization-adjustable laser beam expansion collimator capable of converting laser transmitted by an optical fiber into a large-diameter parallel laser beam, wherein the laser beam generated by the laser beam expansion collimator is used for generating cold atomic groups with large atomic number, stable number and ultralow temperature, and can be used for a cold atomic physical experiment system.
Background
In cold atom physical experiments and instruments and equipment taking cold atoms as working media, the acquisition of ultra-low temperature atomic groups with stable atomic numbers is a primary technical problem to be solved. The most effective method for obtaining the super-cooled atoms at present is to prepare the super-cooled atoms by adopting the interaction of laser beams and atoms, and according to a laser cooling theory, the common method for cooling the atoms by laser mainly comprises an optical trap and a magneto-optical trap, wherein the two ways generate the super-cooled atoms by a polarization gradient cooling method, but the optical trap mode does not need to be externally provided with a gradient magnetic field (generated by adopting a pair of anti-Helmholtz coils), and only needs to concentrate three linearly polarized laser beams (linearly polarized light) which are aligned and have mutually orthogonal polarization into a vacuum bin filled with hot atom steam, so that cold atomic groups can be obtained at the light beam convergence position; the polarization state of the three aligned and directly opposed laser beams used in the magneto-optical trap mode is circular polarization quadrature (sigma + -sigma), and a gradient magnetic field is additionally applied to capture cold radicals (see J.Dalibard and C.Cohen-Tannoudji, J.Opt.Soc.Am.B, vol.6, no.11, november 1989). However, whichever type of trap is used, an important premise is that the polarization distribution across the cross-section of the laser beam in the trap system should be very uniform, while the beam diameter should be large enough and strictly parallel, so that a high quality ultra-cold atom cloud with a large number of atoms and a low temperature can be obtained from the trap. In general, before the laser generated by the laser system for preparing the cold atoms finally enters the magneto-optical trap and the optical trap system, the laser is firstly divided into six beams by a beam splitter, and then the six polarization maintaining optical fibers are respectively input into six beam expanding collimators to form parallel beams and then enter the magneto-optical trap or the optical trap, so that the performance of the laser beam expanding collimator is directly related to the quality of the prepared cold atomic groups, however, the existing laser beam expanding collimator has the following defects:
1) Only a slide in an optical path of the existing polarization maintaining optical fiber input type beam expanding collimator can rotate, so that the polarization of an input laser beam cannot be accurately regulated and maintained, the power and the polarization state of an output laser beam can be obviously changed along with environmental changes, and the polarization maintaining optical fiber input type beam expanding collimator is very unfavorable for generating ultra-low temperature cold atomic groups with stable atomic numbers.
2) The large length of the existing beam expansion collimator is one of the main factors which prevent the miniaturization of the whole cold atom physical system.
3) The existing beam expansion collimator is generally connected with an optical fiber through a six-dimensional adjusting frame, and the position and the direction of a guided laser beam are adjusted, the six-dimensional adjusting frame is easily affected by vibration of the external environment, so that the input position parameters of the laser beam are changed, the quality of the prepared cold atomic groups is affected, and the reliability of the whole cold atomic physical system is further reduced.
Disclosure of Invention
In order to overcome the defect that the polarization of an input laser beam cannot be accurately regulated and maintained by the existing beam expansion collimator, the invention provides the polarization-adjustable laser beam expansion collimator for a magneto-optical trap, an optical trap and other structural cold atom physical experiment systems.
The technical scheme of the invention is as follows:
The polarization-adjustable laser beam expansion collimator comprises a lens barrel, and a laser input collimation system, a polarization adjustment system and a beam expansion system which are sequentially arranged along the laser transmission direction;
the polarization adjusting system and the beam expanding system are arranged in the lens barrel;
the special feature is that:
The polarization adjustment system comprises a rotary support base, a polarization prism and a glass slide, wherein the polarization prism and the glass slide are sequentially arranged along a light beam propagation path; the polarizing prism is used for regulating the polarization state of the collimated laser output by the laser input collimation system;
The rotary support base is a cylinder with a circular light-passing hole in the center, circular grooves are formed in two end faces of the cylinder, and two opposite positions on the side wall of the cylinder are concave to form arc surfaces with symmetrical shapes;
The circular groove is internally provided with a first rotary mounting seat and a second rotary mounting seat which are independent and can rotate relative to the rotary support base respectively, and the circular groove is axially limited by a first limiting plate and a second limiting plate which are fixedly connected with the rotary support base and are provided with round holes in the center; the rotation axes of the first rotary mounting seat and the second rotary mounting seat are collinear;
The polarizing prism and the glass slide are respectively arranged in the first rotary mounting seat and the second rotary mounting seat;
The side wall of the first rotary mounting seat is provided with a plurality of first rotary adjusting holes uniformly distributed along the same circumference, and the side wall of the second rotary mounting seat is provided with a plurality of second rotary adjusting holes uniformly distributed along the same circumference; the first rotation adjusting hole and the second rotation adjusting hole are used for inserting a spanner so as to facilitate the angle adjustment of the first rotation mounting seat and the second rotation mounting seat;
the inner concave cambered surface on the side wall of the rotary support base is provided with a second locking screw hole, a third locking screw hole, a second locking screw and a third locking screw which are matched with the second locking screw hole and the third locking screw, and the second locking screw is used for locking the rotation of the first rotary mounting seat and the second rotary mounting seat;
Windows are formed in two symmetrical positions on the side wall of the cylinder body in the middle of the lens cone, so that the side walls of the first rotary mounting seat and the second rotary mounting seat are exposed in the windows.
Further, the laser input collimation system comprises an optical fiber coupling head, a direction adjusting plate and a direction adjusting base which are sequentially connected along the laser input direction; the main body of the direction adjusting plate is cylindrical, the middle part of the backlight surface of the direction adjusting plate is provided with a hemispherical rotating head protruding outwards, the middle part of the backlight surface of the direction adjusting plate is provided with an inclined mounting plate, and the middle part of the direction adjusting plate is provided with a circular light through hole penetrating the hemispherical rotating head, the cylindrical main body and the inclined mounting plate; the included angle between the installation surface of the inclined installation plate for installing the optical fiber coupling head and the end surface of the direction adjustment plate is theta, and the value range of theta is 2-8 degrees; the optical fiber coupling head is fixedly arranged on the mounting surface; the center of the hemispherical rotating head coincides with the center of the light-emitting end face of the polarization maintaining optical fiber inserted in the optical fiber coupling head; the direction adjusting base is cylindrical as a whole, one end is opened, and the other end is closed; a round hole is formed in the middle of the closed end, and the side wall of the round hole is matched with the spherical surface of the hemispherical rotating head; an arc-shaped slit is formed in the side wall of the direction adjusting base, the middle of the arc-shaped slit is cut along the axial direction to form a longitudinal slit, two raised lug seats are arranged at the two ends of the longitudinal slit, and a first locking screw hole is formed in each lug seat; one end of the lens barrel is inserted into the direction adjusting base, the direction adjusting base can adjust the position along the axial direction of the lens barrel, and the position of the direction adjusting base is locked with the first locking screw through the first locking screw hole; the direction adjusting plate is driven by a plurality of direction adjusters uniformly distributed along the same circumference, and the pitch/deflection angles of the laser incidence points can be changed by adjusting the direction adjusters along the optical axis in a gradual manner, and the displacement of the direction adjusting plate along the optical axis direction of the lens barrel is realized.
Further, the direction regulator is a screw with a spherical structure at the top end and a locking ring at the tail end, and a ceramic column base is arranged at the corresponding contact position between the direction regulating base and the spherical structure and used as a support of the direction regulator; the lock ring is used to lock the position of the direction regulator.
Further, the ceramic column base is bonded to the orientation adjustment base by a high temperature, low outgassing epoxy.
Further, the first rotary mount and the second rotary mount each have a knurled edge and a 360 dial.
Further, the beam expanding system comprises a concave lens, a convex lens and a diaphragm which are sequentially arranged along the beam transmission path, and the concave lens is overlapped with the focus of the convex lens; the concave lens is fixed in the lens barrel through a first pressing ring; the convex lens is fixed in the lens barrel through a gasket and a second pressing ring; the diaphragm is fixed in the lens barrel through a third pressing ring; the light passing hole in the center of the diaphragm is a round hole and is used for cutting off the useless edge part light of the collimated parallel laser beams according to the ring shape.
Further, the convex lens may be replaced by a group of convex lenses or a double cemented convex lens.
Further, the diameter of the light passing hole in the center of the diaphragm is 1/e 2 of the diameter corresponding to the light intensity of the parallel laser beams after beam expansion.
Further, a length scale is arranged on a cylinder part matched with the laser input collimation system on the lens barrel.
Further, the device also comprises a 45-degree rectangular plane mirror arranged on the optical path between the polarization adjustment system and the beam expanding system; the lens cone is L-shaped.
The invention has the following technical effects:
1. The polarization prism and the glass slide, the polarization axes of which can be independently and precisely adjusted, are arranged in the light path, so that the polarization state of the light beam input by the polarization maintaining optical fiber can be precisely adjusted and maintained, fluctuation of laser power is reduced, the polarization state change of the emergent light beam caused by the polarization maintaining optical fiber is eliminated, and the requirement of high-quality super-cooled atom preparation is met.
2. The optical system of the laser beam expansion collimator provided by the invention adopts a short focal length design, and can be further optimized into a folded optical path, so that the length of the laser beam expansion collimator is obviously reduced, the occupied space of a magneto-optical trap/optical trap system is greatly reduced, and the miniaturization of the whole cold atomic system is facilitated.
3. The laser input collimation system in the laser beam expansion collimator provided by the invention adopts a new structural design, ensures that the position and the direction of the guided laser beam are precisely adjusted, reduces the adjustment difficulty, can lock the adjusting element after the adjustment is finished, and improves the reliability of the system.
Drawings
Fig. 1 is a schematic view of the arrangement of optical elements of embodiment 1 (straight line type) of the present invention.
Fig. 2 is an exploded view of an optical machine according to embodiment 1 of the present invention.
Fig. 3 is an exploded view of the laser input collimation system in embodiment 1 of the present invention.
Fig. 4 is an exploded view of the optical machine structure of the polarization adjustment system in embodiment 1 of the present invention.
Fig. 5 is a schematic cross-sectional view of the structure of embodiment 1 of the present invention.
Fig. 6 is a schematic view showing the arrangement of optical elements in embodiment 2 (folded type) of the present invention.
Fig. 7 is an exploded view of the optical machine structure of embodiment 2 of the present invention.
Fig. 8 is a schematic cross-sectional view of the structure of embodiment 2 of the present invention.
Reference numerals illustrate:
100-laser input collimation system, 110-direction adjustment base, 112-round hole, 113-arc slit, 114-first locking screw hole, 115-first locking screw, 130-optical fiber coupling head, 131-screw, 120-direction adjustment plate, 121-hexagon socket screw, 122-direction regulator, 125-hemispherical rotating head, 126-inclined mounting plate;
200-polarization adjustment system, 210-first limiting plate, 211-first screw, 212-first screw hole, 220-first rotation mounting seat, 222-first rotation adjustment hole, 221-polarization prism, 230-rotation support base, 232-second locking screw hole, 233-second locking screw, 234-third locking screw hole, 235-third locking screw, 240-second rotation mounting seat, 241-slide, 242-slide press ring, 243-second rotation adjustment hole, 250-second limiting plate, 251-second screw, 252-second screw hole;
300 beam expanding system, 301-concave lens, 302-convex lens; 303-a first clamping ring, 304-a gasket, 305-a second clamping ring, 306-a diaphragm, 307-a third clamping ring; 310-a planar mirror, which is arranged to be parallel to the plane of the mirror,
400-Lens cone, 401-window, 402-third screw hole, 405-length scale, 410-limit ring, 421-support plate, 422-back cover plate, 423-third screw, 424-fourth screw, 425-outer frame, 426-fifth screw, 427-sixth screw.
Detailed Description
The invention is further described below with reference to examples and figures.
Example 1
As shown in fig. 2, the polarization-adjustable laser beam expansion collimator of the present embodiment includes a lens barrel 400, and a laser input collimation system 100, a polarization adjustment system 200, and a beam expansion system 300, which are sequentially arranged along the laser transmission direction.
The lens barrel 400 is used for placing the polarization adjustment system 200 and the beam expanding system 300; the laser input collimation system 100 is used for guiding and collimating a laser beam; the polarization adjustment system 200 is used for precisely adjusting and maintaining the polarization state of the collimated laser beam; the beam expanding system is used for expanding the laser beam after the polarization state is adjusted.
As shown in fig. 3, the laser input alignment system 100 includes an optical fiber coupling head 130, a direction adjustment plate 120, and a direction adjustment base 110 sequentially disposed along a laser input direction, the optical fiber coupling head 130 being mounted on the direction adjustment plate 120;
The main body of the direction adjusting plate 120 is cylindrical, the middle part of the backlight surface of the main body is provided with a hemispherical rotating head 125 protruding outwards, the middle part of the backlight surface of the main body is provided with an inclined mounting plate 126, and the middle part of the backlight surface of the main body is provided with a circular light passing hole penetrating through the hemispherical rotating head 125, the cylindrical main body and the inclined mounting plate 126; the included angle between the installation surface of the inclined installation plate 126 for installing the optical fiber coupling head 130 and the end surface of the direction adjustment plate 120 is θ, the value range of θ is 2-8 degrees, and the value is 4 degrees according to the inclination angle of the optical fiber end surface;
the optical fiber coupling head 130 is fixedly mounted on the mounting surface of the inclined mounting plate 126 through four screws 131; the polarization maintaining optical fiber for transmitting laser is inserted into the optical fiber coupling head 130, and the incident angle of the laser and the spatial position of the incident point M can be adjusted by adjusting the direction adjusting plate 120, so that the laser beam direction coincides with the optical axis of the lens barrel 400, and the incident point M coincides with the focal point S of the optical system composed of the concave lens 301 and the convex lens 302, see fig. 1.
The center of the hemispherical rotating head 125 coincides with the center position of the light emitting end surface of the polarization maintaining fiber at the point M (M is also the incident point), so that the incident point position of the laser beam is always unchanged when the direction adjusting plate 120 rotates, but the direction of the beam is changed;
The direction adjustment base 110 is cylindrical as a whole, and has one end open and the other end closed; a round hole 112 is formed in the middle of the closed end, the side wall of the round hole 112 is a curved surface, the curvature of the curved surface is the same as that of the hemispherical rotating head 125 on the direction adjusting plate 120, and the curved surface and the hemispherical rotating head 125 form spherical fit, so that transverse offset on a horizontal plane possibly generated by the direction adjusting plate 120 during adjustment is prevented, and the adjustment dimension of the whole laser input collimation system 100 is reduced to 4 dimensions;
An arc slit 113 is formed on the side wall of the direction adjustment base 110, and the length of the arc slit 113 is about 1/2 of the circumference of the cylinder of the direction adjustment base 110. The arc slit 113 is cut in the middle of a semicircular girdle cut out on the direction adjustment base 110 along the axial direction to form a longitudinal slit, two raised ear seats are arranged at two ends of the longitudinal slit, and locking screw holes 114 are formed in the ear seats; the purpose of providing the arc-shaped slit 113 and the longitudinal slit is to form a flexible locking structure such that the lens barrel 400 forms a cylindrical fit with the direction adjustment base 110 when a portion of the lens barrel 400 is inserted into the direction adjustment base 110, as shown in fig. 5; the direction adjustment base 110 can be adjusted in a longitudinal direction relative to the lens barrel 400 by moving in the optical axis direction (longitudinal direction) of the lens barrel 400, and is position-locked with the first locking screw 115 through the first locking screw hole 114.
The direction adjusting plate 120 is connected with the direction adjusting base 110 through three socket head cap screws 121, and the screw positions are close to the edge of the direction adjusting plate 120 and are circumferentially distributed at 120 degrees;
The direction adjusting plate 120 is driven by three direction adjusters 122, the positions of the three direction adjusters 122 are circumferentially distributed on the direction adjusting plate 120 at 120 degrees and are staggered with the three hexagon socket head cap screws 121, the pitch/yaw angles of the laser incident points can be changed by adjusting the three direction adjusters 122 along the optical axis in a quantity-by-quantity manner, and meanwhile, the direction adjusting plate 120 can be displaced along the optical axis direction of the lens barrel 400 by adjusting the three direction adjusters 122, and the translational range along the optical axis direction of the lens barrel 400 in the embodiment is +/-1.0 mm.
To facilitate distinguishing between the direction adjusters that have been or will be used, three direction adjusters 122 may be labeled, such as Z1, Z2, or Z3, respectively. In this embodiment, the three direction adjusters 122 are all precision screws.
Under the condition of higher requirements on adjustment precision and stability, the direction regulator 122 can be optimized to be a screw with a spherical structure at the top end and a locking ring at the tail end, and a ceramic column base is arranged at the corresponding contact position between the direction regulating base 110 and the spherical top end of the direction regulator 122 to be used as a support; the ceramic column base is bonded to the orientation adjustment base 110 by a high temperature, low outgassing epoxy to provide a stable, wear resistant motion system; after the final direction adjustment is completed, the position of the direction adjustment plate 120 may be locked by tightening a lock ring at the end of the direction adjuster 122.
As shown in fig. 4, the polarization adjustment system 200 includes a rotation support base 230, a polarization prism 221 and a slide 241 mounted on the rotation support base 230, and the polarization prism 221 and the slide 241 are sequentially disposed along a beam propagation path;
The rotary support base 230 is a cylinder with a circular light-passing hole in the center, circular grooves are formed in two end faces of the cylinder, and two opposite positions on the side wall of the cylinder are concave to form arc surfaces with symmetrical shapes;
The circular grooves on the two end surfaces of the rotation support base 230 are respectively provided with a first rotation mounting seat 220 and a second rotation mounting seat 240 which are independent and can rotate relative to the rotation support base 230, and the rotation axes of the first rotation mounting seat 220 and the second rotation mounting seat 240 are collinear; the polarizing prism 221 is installed in the first rotary mount 220, and the slide 241 is fixed in the second rotary mount 240 by a slide press ring 242;
The first rotary mount 220 and the second rotary mount 240 each have a knurled edge and a 360 degree dial (2 degree index, set on the upper disc surface edge of the rotary mount, i.e., the upper disc surface edge perpendicular to the knurled edge); the knurled edges facilitate adjustment of the rotary mounting seat; the dial is used for precise and repeatable positioning and fine angular adjustment. Six first rotation adjusting holes 222 uniformly distributed along the same circumference are formed in the knurled edge of the first rotation mounting seat 220, and six second rotation adjusting holes 243 uniformly distributed along the same circumference are formed in the knurled edge of the second rotation mounting seat 240; the first rotation adjustment hole 222 and the second rotation adjustment hole 243 are used for inserting a wrench to facilitate the angular adjustment of the first rotation mount 220 and the second rotation mount 240;
The concave cambered surface on the side wall of the rotation support base 230 is provided with a second locking screw hole 232 and a third locking screw hole 234, and a second locking screw 233 and a third locking screw 235 matched with the second locking screw hole and the third locking screw hole for locking the rotation of the first rotation mounting seat 220 and the second rotation mounting seat 240.
After the first rotary mounting seat 220 and the second rotary mounting seat 240 are mounted on the rotary support base 230, axial limitation is performed by the first limiting plate 210 and the second limiting plate 250 with round holes in the center, so that the first rotary mounting seat 220 and the second rotary mounting seat 240 can only rotate around respective central axes; the first limiting plate 210 is fixedly connected with the rotation support base 230 through a first screw 211 and a first screw hole 212, and the second limiting plate 250 is fixedly connected with the rotation support base 230 through a second screw 251 and a second screw hole 252.
As shown in fig. 2, the beam expanding system 300 includes a concave lens 301, a convex lens 302, and a diaphragm 306, which are sequentially disposed along a beam transmission path, the concave lens 301 coinciding with a focal point of the convex lens 302; the convex lens 302 may also be optimized as a set of convex lenses or as a doublet convex lens for better elimination of spherical aberration.
The concave lens 301 is placed in the lens barrel 400 and fixed by the first press ring 303;
The convex lens 302 is placed in the lens barrel 400 and fixed by a washer 304 and a second press ring 305;
the diaphragm 306 is placed in the lens barrel 400 and fixed by a third pressing ring 307;
The light passing hole in the center of the diaphragm 306 is a circular hole, and is used for cutting off the useless edge part light of the collimated parallel laser beams according to the ring shape, and the diameter of the light passing hole in the center of the diaphragm 306 is the diameter corresponding to the 1/e 2 light intensity of the expanded parallel laser beams.
As shown in fig. 2 and 5, the polarization adjustment system 200 and the beam expansion system 300 are disposed inside the lens barrel 400; a third screw hole 402 is formed in the cylinder body in the middle of the lens barrel 400, and is used for arranging screws to fix the position of the polarization adjustment system 200 in the lens barrel 400; a limiting ring 410 is arranged in the lens barrel 400 and is used for limiting the polarization adjustment system 200;
Rectangular windows 401 are formed in two symmetrical positions on the side wall of the cylinder in the middle of the lens barrel 400, so that knurled edges of the first rotary mounting seat 220 and the second rotary mounting seat 240 in the polarization adjustment system 200 are exposed in the rectangular windows 401, and the polarization axis and the polarization state of the laser beam can be adjusted by rotating the first rotary mounting seat 220 and/or the second rotary mounting seat 240 manually or through an adjusting rod;
The barrel 400 is provided with a length scale 405 on a cylindrical portion thereof which is engaged with the direction adjustment base 110 in the laser input alignment system 100, and the length scale 405 has an indication function when the longitudinal (along the optical axis direction of the barrel 400) position of the laser input alignment system 100 is finely adjusted every 1mm of the length scale 405.
After the assembly is completed, the optical elements of the present embodiment are distributed in a linear manner, and the polarizing prism 221, the slide 241, the concave lens 301, and the convex lens 302 are sequentially arranged along the beam propagation direction, as shown in fig. 1; the conical space laser beam emitted by the polarization maintaining optical fiber sequentially passes through the polarizing prism 221 and the glass slide 241, reaches the concave lens 301, and then reaches the convex lens 302 after being expanded by the concave lens 301, and is converted into parallel light beams to be emitted.
Example 2:
Referring to fig. 7 and 8, compared with embodiment 1, the structure, function and adjustment manner of the laser input collimating system 100, the polarization adjusting system 200 and the beam expanding system 300 are exactly the same as those of embodiment 1, except that embodiment 2 incorporates a 45-degree rectangular plane mirror 310 and its mechanical fixing and adjusting structure in the optical path, and the lens barrel 400 becomes "L" shape according to the characteristics of the optical path.
The 45-degree rectangular plane reflecting mirror 310 is fixedly connected to the supporting plate 421 through glue or screws, the supporting plate 421 is fixedly connected with the rear cover plate 422 through three third screws 423, the three third screws 423 are distributed at 120 degrees on a plane, the rear cover plate 422 is fixedly connected with the outer frame 425 through four fourth screws 424, and the outer frame 425 is fixedly connected with the L-shaped lens barrel 400 through two fifth screws 426 and two sixth screws 427.
After the assembly is completed, the optical elements of the present embodiment are distributed in an "L" shape, and the polarizing prism 221, the glass slide 241, the 45-degree rectangular plane mirror 310, the concave lens 301, and the convex lens 302 are sequentially arranged along the beam propagation path, as shown in fig. 6; the conical space laser beam emitted by the polarization maintaining optical fiber sequentially passes through the polarizing prism 221 and the glass slide 241, then passes through the 45-degree rectangular plane reflecting mirror 310 to turn by 90 degrees, reaches the concave lens 301, then passes through the concave lens 301 to expand the beam, reaches the convex lens 302, and is converted into parallel light beams to be emitted.
The screws used in the above embodiments of the present invention are all made of nonmagnetic metal materials, such as titanium and nonmagnetic stainless steel.
The interaction of laser and atoms is needed for capturing, trapping and cooling atoms by a magneto-optical trap or an optical trap, but the magnetic field is needed for capturing atoms by the magneto-optical trap, and the optical trap is purely optical and does not need a magnetic field. Thus, if the invention is used in a magneto-optical trap, slide 241 is a lambda/4 wave plate; if the invention is used in an optical trap, the slide 241 is a lambda/2 wave plate, which can be configured according to actual needs.
The application method of the invention is as follows:
taking the embodiment 1, i.e. the linear polarization adjustable laser beam expansion collimator, as an example for linear polarization gradient cooling, three groups of lasers used in the linear polarization gradient cooling are linear polarized light, so that λ/2 wave plates with corresponding laser wavelengths need to be placed in the second rotary mounting seats 240 of the laser beam expansion collimators corresponding to the six embodiments 1.
The linearly polarized laser transmitted through the polarization maintaining fiber is introduced into the polarization-tunable laser beam expansion collimator of embodiment 1 by the fiber coupling head 130 and then becomes spatial beam transmission,
The direction adjustment plate 120 is adjusted to make the angle between the light output angle of the optical fiber and the optical axis of the optical system composed of the concave lens 301 and the convex lens 302 be zero, and then the base 110 is adjusted to move back and forth to make the laser incident point M coincide with the focal point S of the optical system composed of the concave lens 301 and the convex lens 302, as shown in fig. 1, the outgoing beam of the laser beam expansion collimator described in embodiment 1 becomes a parallel beam with an increased spot radius.
The polarization prism 221 is rotated to make the transmission direction consistent with the polarization direction of the space beam, the transmitted beam energy is the largest at this time, the space beam is polarized to become linear polarized light, then the third locking screw 235 in the third locking screw hole 234 is adjusted to fix the orientation of the polarization prism 221, the linear polarized light then passes through the lambda/2 wave plate (glass slide 241), the lambda/2 wave plate (glass slide 241) is rotated to adjust the polarization direction of the beam to a required angle, and then the second locking screw 233 in the second locking screw hole 232 is adjusted to fix the orientation of the lambda/2 wave plate (glass slide 241), thus obtaining the required parallel laser beam with fixed polarization state.
The same method is adopted to adjust the six polarization-adjustable laser beam expansion collimators described in the embodiment 1 so that the output beams are parallel laser beams of the expanded beams;
The parallel laser beams generated by the two polarization-adjustable laser beam expansion collimators and incident to the atom trapping region are collinearly opposed, the polarization directions of the collinearly opposed laser beams are orthogonalized by adjusting a lambda/2 wave plate (glass slide 241) in the collinearly opposed laser beams, then another two groups of collinearly opposed parallel laser beams with orthogonalized polarization directions are obtained by adopting the same method, and atoms can be trapped, trapped and cooled by forming three groups of mutually orthogonalized linear T-line lasers by six laser beams.
Sigma + -sigma-polarization gradient cooling is different from linear polarization gradient cooling principle, but the working process is similar.
When the linear polarization adjustable laser beam expansion collimator is used for sigma+ -sigma-polarization gradient cooling, only the slide 241 in the second rotary mounting seat 240 of the six beam expansion collimators is replaced by a lambda/4 wave plate with corresponding laser wavelength, and the rest of the adjustment steps of capturing, trapping and cooling atoms are the same.
In embodiment 2, namely, when the folded polarization-adjustable laser beam expansion collimator is used for linear-type linear polarization gradient cooling, the glass slides 241 in the second rotary mounting seats 240 of the six laser beam expansion collimators are lambda/2 wave plates with corresponding laser wavelengths, and the rest of the adjustment steps for capturing, trapping and cooling atoms are the same as those of the linear polarization-adjustable laser beam expansion collimator.
When the folded polarization-adjustable laser beam expansion collimator is used for sigma+ -sigma-polarization gradient cooling, two forms exist:
1) The glass slide 241 in the second rotary mounting seat 240 of the six laser beam expansion collimators is a lambda/2 wave plate with corresponding laser wavelength, and only one lambda/2 wave plate is bonded on the diaphragm 306;
2) The glass slide 241 of the second rotary mount 240 of the six laser beam expansion collimators becomes a lambda/4 wave plate for the corresponding laser wavelength; the rest of the steps of trapping, trapping and cooling atoms are the same as those of the linear polarization-adjustable laser beam expansion collimator.
Claims (10)
1. The polarization-adjustable laser beam expansion collimator comprises a lens barrel (400), a laser input collimation system (100), a polarization adjustment system (200) and a beam expansion system (300), wherein the laser input collimation system (100), the polarization adjustment system (200) and the beam expansion system (300) are sequentially arranged along the laser transmission direction;
the polarization adjustment system (200) and the beam expansion system (300) are arranged in the lens barrel (400);
The method is characterized in that:
The polarization adjustment system (200) comprises a rotation support base (230), a polarization prism (221) and a slide (241) which are sequentially arranged along the light beam propagation path; the polarizing prism (221) is used for adjusting the polarization state of the collimated laser output by the laser input collimation system (100);
The rotary support base (230) is a cylinder with a circular light-passing hole in the center, circular grooves are formed in two end faces of the cylinder, and two opposite positions on the side wall of the cylinder are concave to form arc surfaces with symmetrical shapes;
The circular groove is internally provided with a first rotary mounting seat (220) and a second rotary mounting seat (240) which are independent and can rotate relative to the rotary support base (230) respectively, and the circular groove is axially limited by a first limiting plate (210) and a second limiting plate (250) which are fixedly connected with the rotary support base (230) and are provided with round holes at the center; the rotation axes of the first rotary mounting seat (220) and the second rotary mounting seat (240) are collinear;
the polarizing prism (221) and the glass slide (241) are respectively arranged in the first rotary mounting seat (220) and the second rotary mounting seat (240);
a plurality of first rotation adjusting holes (222) uniformly distributed along the same circumference are formed in the side wall of the first rotation mounting seat (220), and a plurality of second rotation adjusting holes (243) uniformly distributed along the same circumference are formed in the side wall of the second rotation mounting seat (240); the first rotation adjustment hole (222) and the second rotation adjustment hole (243) are used for inserting a wrench so as to perform angle adjustment on the first rotation mounting seat (220) and the second rotation mounting seat (240);
The inner concave cambered surface on the side wall of the rotary support base (230) is provided with a second locking screw hole (232) and a third locking screw hole (234) as well as a second locking screw (233) and a third locking screw (235) matched with the second locking screw hole and the third locking screw, which are used for locking the rotation of the first rotary mounting seat (220) and the second rotary mounting seat (240);
Windows (401) are formed in two symmetrical positions on the side wall of the middle cylinder body of the lens cone (400), so that the side walls of the first rotary mounting seat (220) and the second rotary mounting seat (240) are exposed in the windows (401).
2. The polarization-tunable laser beam expanding collimator of claim 1, wherein:
The laser input collimation system (100) comprises an optical fiber coupling head (130), a direction adjusting plate (120) and a direction adjusting base (110) which are sequentially connected along the laser input direction;
the main body of the direction adjusting plate (120) is cylindrical, the middle part of the backlight surface of the main body is provided with a hemispherical rotating head (125) protruding outwards, the middle part of the backlight surface of the main body is provided with an inclined mounting plate (126), and the middle part of the backlight surface of the main body is provided with a circular light-transmitting hole penetrating through the hemispherical rotating head (125), the cylindrical main body and the inclined mounting plate (126);
The included angle between the installation surface of the inclined installation plate (126) for installing the optical fiber coupling head (130) and the end surface of the direction adjustment plate (120) is theta, and the value range of theta is 2-8 degrees; the optical fiber coupling head (130) is fixedly arranged on the mounting surface;
the sphere center of the hemispherical rotating head (125) is overlapped with the center position of the light-emitting end face of the polarization maintaining optical fiber inserted in the optical fiber coupling head (130);
The direction adjustment base (110) is cylindrical as a whole, one end is opened, and the other end is closed; a round hole (112) is formed in the middle of the closed end, and the side wall of the round hole (112) is matched with the spherical surface of the hemispherical rotating head (125);
an arc-shaped slit (113) is formed in the side wall of the direction adjustment base (110), the middle of the arc-shaped slit (113) is cut along the axial direction to form a longitudinal slit, two raised lug seats are arranged at two ends of the longitudinal slit, and a first locking screw hole (114) is formed in each lug seat;
one end of the lens barrel (400) is inserted into the direction adjustment base (110), and the direction adjustment base (110) can adjust the position along the axial direction of the lens barrel (400) and is locked with the first locking screw (115) through the first locking screw hole (114);
the direction adjusting plate (120) is driven by a plurality of direction adjusters (122) uniformly distributed along the same circumference, the pitch/yaw angle of the laser incidence point can be changed by adjusting the direction adjusters (122) along the optical axis in a quantity-by-quantity mode, and the displacement of the direction adjusting plate (120) along the optical axis direction of the lens barrel (400) is realized.
3. The polarization-tunable laser beam expanding collimator of claim 2, wherein:
the direction regulator (122) is a screw with a spherical structure at the top end and a locking ring at the tail end, and a ceramic column base is arranged on the corresponding contact position of the direction regulating base (110) and the spherical structure and used as a support of the direction regulator (122); the lock ring is used to lock the position of the direction regulator (122).
4. A polarization-tunable laser beam expanding collimator according to claim 3, wherein:
The ceramic column base is bonded to the orientation adjustment base (110) by a high temperature, low outgassing epoxy.
5. The polarization-tunable laser beam expanding collimator of claim 2, wherein:
The first rotary mount (220) and the second rotary mount (240) each have a knurled edge and a 360 dial.
6. The polarization-tunable laser beam expanding collimator of claim 1, wherein:
the beam expanding system (300) comprises a concave lens (301), a convex lens (302) and a diaphragm (306) which are sequentially arranged along a beam transmission path, wherein the concave lens (301) is overlapped with the focus of the convex lens (302);
The concave lens (301) is fixed in the lens barrel (400) through a first pressing ring (303);
the convex lens (302) is fixed in the lens barrel (400) through a gasket (304) and a second pressing ring (305);
the diaphragm (306) is fixed in the lens barrel (400) through a third pressing ring (307);
The light passing hole in the center of the diaphragm (306) is a round hole and is used for cutting off the useless edge part light of the collimated parallel laser beams according to the ring shape.
7. The polarization-tunable laser beam expanding collimator of claim 6, wherein: the convex lens (302) may be replaced by a set of convex lenses or a doublet convex lens.
8. The polarization-tunable laser beam expanding collimator of claim 6, wherein: the diameter of the light passing hole in the center of the diaphragm (306) is the diameter corresponding to 1/e 2 light intensity of the parallel laser beam after beam expansion.
9. The polarization-tunable laser beam expanding collimator of claim 1, wherein:
A length scale (405) is arranged on a cylinder part of the lens barrel (400) matched with the laser input collimation system (100).
10. The polarization-tunable laser beam expanding collimator according to any one of claims 1to 9, wherein:
the system also comprises a 45-degree rectangular plane mirror (310) arranged on the optical path between the polarization adjustment system (200) and the beam expanding system (300); the lens barrel (400) is L-shaped.
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| CN112327502B (en) * | 2020-09-28 | 2022-07-19 | 南京核安核能科技有限公司 | Detector collimator with opening adjustment |
| CN113433706B (en) * | 2021-06-21 | 2023-05-05 | 深圳市大族数控科技股份有限公司 | Debugging and checking method for laser shaping light path |
| CN113376750B (en) * | 2021-06-24 | 2022-05-24 | 中国计量科学研究院 | High-precision optical fiber coupler |
| CN113791472A (en) * | 2021-11-18 | 2021-12-14 | 之江实验室 | Optical fiber coupler capable of being precisely adjusted in multiple dimensions |
| CN114488551B (en) * | 2021-12-10 | 2024-02-23 | 华中光电技术研究所（中国船舶重工集团公司第七一七研究所） | Optical fiber beam splitting module for atomic interferometer |
| CN114545644A (en) * | 2022-02-22 | 2022-05-27 | 湖北优光科学仪器有限公司 | High-precision corner-adjustable optical fiber collimation system |
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| CN101806946B (en) * | 2010-03-05 | 2011-04-06 | 中国科学院上海光学精密机械研究所 | Optical beam expanding collimation system |
| CN104808344B (en) * | 2015-05-19 | 2017-03-08 | 中国科学院武汉物理与数学研究所 | The beam expanding lens system of multiple different polarization states laser beams is exported simultaneously can |
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