CN116224496A - Optical fiber coupling system with adjustable output light power ratio for atomic physics research - Google Patents
Optical fiber coupling system with adjustable output light power ratio for atomic physics research Download PDFInfo
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- CN116224496A CN116224496A CN202310033327.8A CN202310033327A CN116224496A CN 116224496 A CN116224496 A CN 116224496A CN 202310033327 A CN202310033327 A CN 202310033327A CN 116224496 A CN116224496 A CN 116224496A
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- optical fiber
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- fiber collimator
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/26—Optical coupling means
- G02B6/27—Optical coupling means with polarisation selective and adjusting means
- G02B6/2706—Optical coupling means with polarisation selective and adjusting means as bulk elements, i.e. free space arrangements external to a light guide, e.g. polarising beam splitters
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/26—Optical coupling means
- G02B6/27—Optical coupling means with polarisation selective and adjusting means
- G02B6/2706—Optical coupling means with polarisation selective and adjusting means as bulk elements, i.e. free space arrangements external to a light guide, e.g. polarising beam splitters
- G02B6/2713—Optical coupling means with polarisation selective and adjusting means as bulk elements, i.e. free space arrangements external to a light guide, e.g. polarising beam splitters cascade of polarisation selective or adjusting operations
- G02B6/272—Optical coupling means with polarisation selective and adjusting means as bulk elements, i.e. free space arrangements external to a light guide, e.g. polarising beam splitters cascade of polarisation selective or adjusting operations comprising polarisation means for beam splitting and combining
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/26—Optical coupling means
- G02B6/27—Optical coupling means with polarisation selective and adjusting means
- G02B6/2753—Optical coupling means with polarisation selective and adjusting means characterised by their function or use, i.e. of the complete device
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- Optics & Photonics (AREA)
- Optical Modulation, Optical Deflection, Nonlinear Optics, Optical Demodulation, Optical Logic Elements (AREA)
Abstract
The invention discloses an optical fiber coupling system with adjustable output light power proportion for atomic physics research, which comprises a first optical fiber collimator, a second optical fiber collimator, a first reflecting mirror, a second reflecting mirror, a liquid crystal variable retarder, a polarization beam splitting prism, a first half wave plate and a second half wave plate, wherein the optical fiber coupling system can work in two modes of proportion-adjustable beam splitting and beam combining according to specific requirements; the laser proportion entering the first optical fiber collimator and the second optical fiber collimator can be quickly adjusted; the utilization efficiency of laser in a set of experimental system and the stability of the experimental system are improved, the space occupied by the experimental system is reduced, and a large amount of experimental resources are saved.
Description
Technical Field
The invention relates to an optical fiber coupling system of a laser application technology, in particular to an optical fiber coupling system with adjustable output light power ratio for atomic physics research.
Background
In the field of laser research, laser transmitted in space is often required to be coupled into an optical fiber, and then guided to other positions in an experimental system for flexible use. Taking the experiment of laser cooling atoms as an example, the seed laser transmitted in space can be subjected to proper frequency shift, light splitting, beam combination and the like on an optical platform through various optical devices, so as to obtain the laser frequency, intensity and polarization meeting the requirements. The corresponding laser is then directed onto a physical system via optical fibers, thereby effecting the manipulation of atoms within the vacuum chamber, as described in (Measuremen of local gravity via a cold atom interferometer.l.zhou et al, chir.Phys.lett.28.0130901 (2011)). With the development of the atomic molecular photophysics research field, the requirement for the function of laser is also more and more complex. For example, in cold atom interferometer research, it is often required to couple two or more of cooling light, pump-back light, push-loading light, raman light, probe light, quenching light and other lasers with different applications into the same optical fiber by using a single-mode polarization maintaining optical fiber, and guide the two or more of the lasers from an optical platform to a beam expander of an interferometer system, and specific requirements are required for the light intensity ratio between the lasers of the cooling light and the raman light, which are disclosed in (Test of Equivalence Principle at E-8Level by a Dual-Species Double-Diffraction Raman Atom interactometer.l.methou, et al, phys.rev.lett.115, 01304 (2015)). Achieving the above functions involves the process of splitting, combining, controlling the optical power of the laser beams at various frequencies and coupling the laser beams into the optical fiber by spatial light. The existing laser coupling technology meets the requirement on the laser coupling efficiency, but the coupling system occupies a larger space, so that the long-term stability of the optical system is also affected to a certain extent, and the laser power coupled into the optical fiber needs to be calibrated from time to time. In addition, the existing coupling mode does not control the relative change of the power of the two laser beams after splitting, and is difficult to satisfy the requirement of the current technical development in function. In view of the above-mentioned needs, there is a need to develop an optical fiber coupling system capable of coupling or outputting two lasers with an adjustable output optical power ratio.
Disclosure of Invention
The invention aims to overcome the defects of the prior art in the aspects of stability, integration level, laser use efficiency and the like of a laser coupling system and provide an optical fiber coupling system with adjustable output optical power ratio for atomic physical research.
The above object of the present invention is achieved by the following technical means:
the optical fiber coupling system with adjustable output light power ratio for atomic physics research comprises a first optical fiber collimator, a second optical fiber collimator, a first reflecting mirror, a second reflecting mirror, a liquid crystal variable retarder, a polarization beam splitter prism, a first half wave plate and a second half wave plate,
the laser is reflected by the first reflector and then enters the polarization beam splitter prism with adjustable rotation angle through the liquid crystal variable retarder,
under a first rotation angle, the polarization splitting prism divides the emergent laser of the liquid crystal variable retarder into first transmission polarized laser and first reflection polarized laser, the first reflection polarized laser is incident into the first optical fiber collimator through the first half-wave plate, the first transmission polarized laser is reflected by the second reflecting mirror and then is incident into the second optical fiber collimator through the second half-wave plate,
under a second rotation angle, the laser emitted by the liquid crystal variable retarder is transmitted by the polarization splitting prism to form second transmitted polarized laser, the other laser passes through the first optical fiber collimator and the first half-wave plate and then is reflected by the polarization splitting prism to form second reflected polarized laser, the second transmitted polarized laser and the second reflected polarized laser are combined to form combined beam light, and the combined beam light is reflected by the second reflecting mirror and then enters the second optical fiber collimator through the second half-wave plate.
The first optical fiber collimator, the second optical fiber collimator, the first reflecting mirror, the liquid crystal variable retarder, the first half wave plate and the second half wave plate are all fixed on the coupling frame base, and the polarization splitting prism is arranged on the coupling frame base through the rotating support.
Compared with the prior art, the invention has the following beneficial effects:
1. the device can work in two modes of proportionally adjustable beam splitting and beam combining according to specific requirements;
2. according to the difference of the voltages applied by the liquid crystal variable delay device, the laser proportion entering the first optical fiber collimator and the second optical fiber collimator can be quickly adjusted;
3. the ratio variation range of the transmission polarized laser and the reflection polarized laser is 1-1000;
4. the laser can be switched in two single-mode polarization maintaining optical fibers in a time-sharing way, so that the utilization efficiency of the laser is greatly improved;
5. the coupling system has extremely small long-term drift and high overall stability;
in a word, the invention enables the same laser beam to be quickly and conveniently coupled into different optical fibers in a time-sharing way, improves the utilization efficiency of the laser in one experimental system and the stability of the experimental system, reduces the space occupied by the experimental system and saves a large amount of experimental resources.
Drawings
FIG. 1 is a schematic diagram of the operation of a polarization beam splitter prism of the present invention at a first rotation angle;
fig. 2 is a schematic diagram of the operation of the polarizing beam splitter prism of the present invention at a second rotation angle.
Wherein: 0-free space laser; 1-1, a first reflecting mirror; 1-2, a second reflector; 2. a liquid crystal variable retarder; 3. a polarization beam splitter prism; 4-1, a first half wave plate; 4-2, a second half-wave plate; 5. a first fiber collimator; 6. a second fiber collimator; 7. and a coupling frame base.
Detailed Description
The present invention will be further described in detail below in conjunction with the following examples, for the purpose of facilitating understanding and practicing the present invention by those of ordinary skill in the art, it being understood that the examples described herein are for the purpose of illustration and explanation only and are not intended to limit the invention.
And (3) a step of: overall (L)
The polarization of the laser light entering the polarization splitting prism 3 is changed by controlling the amplitude of the voltage applied by the liquid crystal variable retarder 2, so that the time-sharing beam splitting coupling of the same laser light is realized.
As shown in fig. 1, the optical fiber coupling system with adjustable output light power ratio for atomic physics research comprises a first optical fiber collimator 5, a second optical fiber collimator 6, a first reflecting mirror 1-1, a second reflecting mirror 1-2, a liquid crystal variable retarder 2, a polarization splitting prism 3, a first half-wave plate 4-1 and a second half-wave plate 4-2,
the laser is reflected by the first reflector 1-1 and then enters the polarization splitting prism 3 with adjustable rotation angle through the liquid crystal variable retarder 2,
the polarization splitting prism 3 splits the outgoing laser of the liquid crystal variable retarder 2 into first transmission polarized laser and first reflection polarized laser under a first rotation angle, the first reflection polarized laser is incident to the first optical fiber collimator 5 through the first half-wave plate 4-1, the first transmission polarized laser is reflected by the second reflecting mirror 1-2 and then is incident to the second optical fiber collimator 6 through the second half-wave plate 4-2,
under a second rotation angle, the polarization splitting prism 3 transmits the laser emitted by the liquid crystal variable retarder 2 to form second transmitted polarized laser, the other laser is reflected by the polarization splitting prism 3 to form second reflected polarized laser after passing through the first optical fiber collimator 5 and the first half-wave plate 4-1, the second transmitted polarized laser and the second reflected polarized laser are combined to form combined beam, and the combined beam is reflected by the second reflecting mirror 1-2 and then enters the second optical fiber collimator 6 through the second half-wave plate 4-2.
The first optical fiber collimator 5, the second optical fiber collimator 6, the first reflecting mirror 1-1, the liquid crystal variable retarder 2, the first half wave plate 4-1 and the second half wave plate 4-2 are all fixed on the coupling frame base 7, and the polarization splitting prism 3 is arranged on the coupling frame base 7 through a rotating bracket.
The first rotation angle and the second rotation angle differ by 90 degrees.
In the present embodiment, the free space laser light is incident on the first reflecting mirror 1-1 at an angle of 45 degrees in the horizontal direction, and the reflected laser light passes through the liquid crystal variable retarder 2 vertically downward;
the radio frequency driving source is connected with the liquid crystal variable delay device 2 to realize the control of the polarization axis of the liquid crystal variable delay device 2;
according to the difference of the polarization directions of the laser, the transmission polarized laser or the reflection polarized laser of the polarization beam splitter prism 3 is selected;
the first reflected polarized laser sequentially passes through a first half-wave plate 4-1 and a first optical fiber collimator 5, and the first half-wave plate 4-1 is used for adjusting the polarization axis of the laser to be coincident with the optical fiber polarization axis; the first optical fiber collimator 5 is connected with a single-mode polarization maintaining optical fiber to realize the coupling output of the first reflected polarized laser;
the first transmission polarized laser sequentially passes through a second reflecting mirror 1-2, a second half-wave plate 4-2 and a second optical fiber collimator 6, and the second half-wave plate 4-2 is used for adjusting the polarization axis of the laser so as to coincide with the polarization axis of the optical fiber; the second optical fiber collimator 6 is connected with a single-mode polarization maintaining optical fiber to realize the coupling output of the first transmission polarized laser;
and II: functional component
Coupling frame base 7: the coupling frame base is used for fixing the optical element and is obtained by machining after the design is finished.
A first mirror 1-1 and a second mirror 1-2: the first mirror 1-1 and the second mirror 1-2 are devices for reflecting polarized laser light and changing the propagation direction thereof.
Liquid crystal variable retarder 2: the liquid crystal variable retarder 2 is a device for controlling the polarization direction of laser light passing through by applying a voltage.
Polarization beam splitter prism 3: the polarization splitting prism 3 is a device for splitting or combining linearly polarized laser light.
A first half-wave plate 4-1 and a second half-wave plate 4-2: the first half-wave plate 4-1 and the second half-wave plate 4-2 are devices for adjusting the polarization direction of the laser light.
A first fiber collimator 5 and a second fiber collimator 6: the first fiber collimator 5 and the second fiber collimator 6 are devices for coupling laser into an optical fiber or collimating laser emitted from the optical fiber into parallel beams with a certain diameter, and consist of a flange plate for fixing the optical fiber and a focusing lens.
Single mode polarization maintaining optical fiber: the single-mode polarization maintaining fiber is one kind of fiber for transmitting linearly polarized laser.
A radio frequency driving source: the radio frequency driving source can output square wave signals with certain power, and can perform frequency modulation (including Frequency Modulation (FM) and keying Frequency Shift (FSK) and Amplitude Modulation (AM)) on the signals, and the liquid crystal variable delay 2 is driven by the radio frequency driving source to control the polarization of laser.
3. Principle of operation
The working principle of the present invention is explained in detail below.
The working principle of the invention is based on a liquid crystal variable retarder (Thorlabs LCC 1411-B).
The overall structure of the liquid crystal variable retarder 2 includes a fused quartz substrate, an organic polyimide film, an insulating layer, a silk-like liquid crystal material, and the like. Transparent conductive films are plated on two parallel surfaces of the transparent box wall, and voltage can be applied on the liquid crystal box. Due to the electro-optic birefringence of the liquid crystal material, the laser phase delay caused by the liquid crystal variable retarder is proportional to the optical path difference and inversely proportional to the laser wavelength. The slow axis of which is marked on the mechanical housing and parallel to the surface of the liquid crystal variable retarder. In the case where no voltage is applied, the alignment of the liquid crystal molecules is determined by the alignment direction of the alignment film molecules at the time of manufacture. When an ac voltage is applied, the liquid crystal molecules change the alignment direction according to the applied voltage. Therefore, the delay of the liquid crystal variable delay device can be actively controlled by changing the applied voltage, so that the beam splitting ratio of the first transmission polarized laser and the first reflection polarized laser after the laser passes through the polarization beam splitting prism is changed.
The free space laser 0 is incident on the first reflecting mirror 1-1 at an angle of 45 degrees in the horizontal direction, and the reflected laser vertically passes through the liquid crystal variable retarder 2 and the polarization splitting prism 3 in order. Wherein the first reflected polarized laser light passes through a first half wave plate 4-1 and subsequently the spatial light is coupled into the optical fiber using a first fiber collimator 5. The first half wave plate 4-1 is used for adjusting the polarization axis of the laser to coincide with the polarization axis of the optical fiber; the first optical fiber collimator 5 is connected with a single-mode polarization maintaining optical fiber to realize the coupling output of the first reflected polarized laser;
the first transmitted polarized laser light of the polarization splitting prism 3 sequentially passes through the second reflecting mirror 1-2 and the second half-wave plate 4-2, and then the space light is coupled into the optical fiber by using the second optical fiber collimator 6. The second half-wave plate 4-2 is used for adjusting the polarization axis of the laser to coincide with the polarization axis of the optical fiber; the second optical fiber collimator is connected with the single-mode polarization maintaining optical fiber to realize the coupling output of the first transmission polarized laser;
the laser light intensity ratio in the single-mode polarization maintaining optical fibers connected with the rear ends of the first optical fiber collimator 5 and the second optical fiber collimator 6 in the final ratio can be quickly adjusted by changing the voltage applied by the liquid crystal variable delay device 2.
In addition, the invention can be easily modified to work in the beam combination mode. Compared with the beam splitting mode, when the beam splitting device works in the beam combining mode, the polarization beam splitting prism 3 is only required to be rotated anticlockwise by 90 degrees. After modification, one free space laser beam is incident on the first reflector 1-1 at an angle of 45 degrees in the horizontal direction, the reflected laser beam vertically propagates downwards and passes through the liquid crystal variable retarder 2, and the voltage applied by the liquid crystal variable retarder 2 is regulated, so that the polarization direction of the laser beam is consistent with the transmission polarization direction of the polarization splitting prism 3. The other laser beam is incident from the first optical fiber collimator 5, propagates along the horizontal direction and passes through the first half-wave plate 4-1, and adjusts the polarization axis direction of the first half-wave plate 4-1 so that the polarization direction of the laser beam is consistent with the reflection polarization direction of the polarization splitting prism 3. At this time, the two laser beams can be combined through the polarization beam splitter prism 3, and the laser beams after the beam combination sequentially pass through the second reflector 1-2 and the second half-wave plate 4-2 and then are coupled into the second optical fiber collimator 6.
In a word, the invention overcomes the defects of poor stability, large occupied space and the like of the traditional laser coupling system, can conveniently and stably work in a beam splitting mode and a beam combining mode with adjustable proportion, greatly improves the light path utilization efficiency and saves experimental resources.
The specific embodiments described herein are offered by way of example only to illustrate the spirit of the invention. Those skilled in the art may make various modifications or additions to the described embodiments or substitutions thereof without departing from the spirit of the invention or exceeding the scope of the invention as defined in the accompanying claims.
Claims (2)
1. The optical fiber coupling system with the adjustable output light power ratio for atomic physics research comprises a first optical fiber collimator (5), and is characterized by further comprising a second optical fiber collimator (6), a first reflecting mirror (1-1), a second reflecting mirror (1-2), a liquid crystal variable retarder (2), a polarization beam splitter prism (3), a first half-wave plate (4-1) and a second half-wave plate (4-2),
the laser is reflected by the first reflector (1-1) and then enters the polarization beam splitter prism (3) with adjustable rotation angle through the liquid crystal variable retarder (2),
under a first rotation angle, the polarization splitting prism (3) divides the emergent laser of the liquid crystal variable retarder (2) into first transmission polarization laser and first reflection polarization laser, the first reflection polarization laser enters the first optical fiber collimator (5) through the first half-wave plate (4-1), the first transmission polarization laser enters the second optical fiber collimator (6) through the second half-wave plate (4-2) after being reflected by the second reflecting mirror (1-2),
under a second rotation angle, the polarization beam splitting prism (3) transmits laser emitted by the liquid crystal variable retarder (2) to form second transmitted polarized laser, the other beam of laser is reflected by the polarization beam splitting prism (3) to form second reflected polarized laser after passing through the first optical fiber collimator (5) and the first half-wave plate (4-1), the second transmitted polarized laser and the second reflected polarized laser are combined to form combined beam, and the combined beam is reflected by the second reflecting mirror (1-2) and then enters the second optical fiber collimator (6) through the second half-wave plate (4-2).
2. The optical fiber coupling system with the adjustable output light power ratio for atomic physics research according to claim 1, wherein the first optical fiber collimator (5), the second optical fiber collimator (6), the first reflecting mirror (1-1), the liquid crystal variable retarder (2), the first half wave plate (4-1) and the second half wave plate (4-2) are all fixed on a coupling frame base (7), and the polarization splitting prism (3) is arranged on the coupling frame base (7) through a rotating bracket.
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| CN202310033327.8A CN116224496A (en) | 2023-01-10 | 2023-01-10 | Optical fiber coupling system with adjustable output light power ratio for atomic physics research |
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| CN202310033327.8A CN116224496A (en) | 2023-01-10 | 2023-01-10 | Optical fiber coupling system with adjustable output light power ratio for atomic physics research |
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