CN102608826B - Device and method for suppressing stimulated Brillouin scattering of pulse laser by use of rotating wave plate - Google Patents
Device and method for suppressing stimulated Brillouin scattering of pulse laser by use of rotating wave plate Download PDFInfo
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- CN102608826B CN102608826B CN201210082401.7A CN201210082401A CN102608826B CN 102608826 B CN102608826 B CN 102608826B CN 201210082401 A CN201210082401 A CN 201210082401A CN 102608826 B CN102608826 B CN 102608826B
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Abstract
A device for suppressing stimulated Brillouin scattering of pulse laser by use of a rotating wave plate comprises a wave plate turntable, wherein the wave plate turntable includes a wave plate rotating around a rotating shaft, a plurality of half-wave plates distributed symmetrically in relative to the rotating shaft on a round plane formed by the wave plate rotating one circle around the rotating shaft, and an air space or a full-wave plate between adjacent half-wave plates. The device is characterized in that the half-wave plate is identical to the full-wave plate or the air space between the half-wave plates in shape and size, and rotates at a uniform velocity in relative to the wave plate turntable, so that the two vertical polarization states of a pulse laser passing through the wave plate turntable respectively account for 50% the pulse length.
Description
Technical field
The present invention relates to stimulated Brillouin scattering, belong to photoelectron technology field.
Background technology
Stimulated Brillouin scattering belongs to technology known in the art, be widely used in phase conjugation compensation, laser acquisition, and the field such as optical communication, requirement for the scattering of excited Brillouin in different application is also different, in the application of laser acquisition and phase conjugation compensation, generally all need high-intensity stimulated Brillouin scattering signal, generally now all to amplify as much as possible stimulated Brillouin scattering signal to obtain best effect, but be the intensity that need to control stimulated Brillouin scattering in some field of optical communication etc., not the generation of the stimulated Brillouin scattering of simple pursuit maximum yet, and next in other situation be to wish to suppress the generation of stimulated Brillouin scattering, because the stimulated Brillouin scattering signal occurring may produce destructive influences to the medium of wherein transmission, or can in the signal of transmission, increase noise, in the face of such technical matters, people have proposed various control or have suppressed the method and apparatus of stimulated Brillouin scattering signal intensity, Chinese patent application 201010602554.0 discloses a kind of like this inhibition method and apparatus of stimulated Brillouin scattering.Its central idea is to utilize the wave plate of rotation to make laser beam on front and back position, have different polarization directions, preferably orthogonal, can well suppress the amplification of the stimulated Brillouin optical that laser below produces front end, but this patent has just proposed a kind of so method, it is mathematical that the method has certain inhibiting effect for Brillouin scattering, but how this application realizes good inhibiting effect for specific laser beam but do not relate to, for example, pulse laser beam, as long as can realize certain inhibiting effect although make laser beam there is orthogonal polarization state on front and back position, but be unknown to those skilled in the art but how to realize good inhibiting effect, the present invention puts forward for this problem.
Summary of the invention
The present invention solves above-mentioned technical matters to have proposed a kind of method and apparatus that utilizes rotating wave plate suppressor pulse laser beam stimulated Brillouin scattering, uses the method and device can realize for the good inhibiting effect of pulse laser beam.
Under regard to principle of work of the present invention and be described in detail, wherein Fig. 1 and Fig. 2 show the stimulated Brillouin scattering restraining device in Chinese patent application 201010602554.0.Shown in Fig. 1 is wave plate rotating disk (3) in Fig. 2, wave plate rotating disk (3) and wave plate turntable rotation support (2) and laser instrument (1) have formed this stimulated Brillouin scattering restraining device jointly, wherein said wave plate rotating disk (3) can be around the turning axle rotation of described wave plate turntable rotation support (2), and in rotary course, can make to have different polarization states through the front and back adjacent part of the linearly polarized laser bundle of the marginal portion of this center of turntable periphery.In Fig. 1, this wave plate rotating disk is disc, this disk has multiple fan-shaped half-wave plates of putting centered by the center of circle, and between every two adjacent fan-shaped half-wave plates, be air or full-wave plate, as shown in Figure 1, if first of central authorities tops the right of disk fan-shaped be half-wave plate, rotate clockwise, next fan-shaped is exactly air or full-wave plate, more next fan-shaped just or half-wave plate, more next fan-shaped be exactly air or full-wave plate.If laser instrument (1) is pulsed laser, the pulse laser beam of laser instrument (1) transmitting is passed after the wave plate rotating disk in rotation status, the polarization state of laser beam will become two kinds of polarization states from original single linear polarization, according to the rotating speed of the size of every half of wave plate and wave plate rotating disk, after the wave plate rotating disk of the pulse laser beam of linear polarization through rotation, roughly there will be as the situation of Fig. 3 a-3h.
First come 3a with the aid of pictures and 3b, when wave plate rotating disk is during in halted state, pulse laser beam is through after wave plate rotating disk, it still keeps single linear polarization, or be S polarization, or be P polarization, also in whole pulse length, only have S polarization or P polarization, now the signal intensity of excited Brillouin is maximum, is also that wave plate rotating disk does not produce effect for the stimulated Brillouin scattering of pulse laser beam.
Then come 3c with the aid of pictures and 3d, in whole pulse length, only have the polarization state of the laser beam of a little part to be changed, conceivablely be, now wave plate rotating disk has just played certain effect for the inhibition of stimulated Brillouin scattering, because when pulse laser beam is by after wave plate rotating disk now, at least on that of end-of-pulsing is a bit of, the polarization direction of polarization state and previous section is orthogonal, situation shown in Fig. 3 c and Fig. 3 d is with respect to the situation shown in Fig. 3 a and Fig. 3 b, there is the inhibiting effect of stimulated Brillouin scattering, but, be appreciated that, its inhibiting effect is certainly not the strongest.
Come again 3e with the aid of pictures and Fig. 3 f, wherein a kind of polarization state has occupied 1/3rd of whole pulse length, another polarization state has occupied 2/3rds of whole pulse length, the polarization state that both differences are just to occupy whole pulse length 2/3rds is continuous distribution or spaced apart, Fig. 3 e is continuous distribution, Fig. 3 f is spaced apart, and the inhibition of the conceivable Fig. 3 of being e and the shown situation of Fig. 3 f is better than the inhibition of Fig. 3 c and Fig. 3 d.
3g the most with the aid of pictures and Fig. 3 h, in these two figure, any polarization state has all occupied the half of whole pulse length, also be that whole pulse length is by two kinds of orthogonal polarization state averaged occupations, difference is that one is the half that has occupied continuously pulse, another one is the half that has occupied pulse in the mode of interleaved, and problem has also just been come so, and now Fig. 3 g compares with the shown inhibition of Fig. 3 f than Fig. 3 e with the shown inhibition of Fig. 3 h well or be bad.
In order to solve the above problems, we analyze stimulated Brillouin scattering on prior theory.We know, the signal intensity of stimulated Brillouin optical
wherein I
srepresent the signal intensity of stimulated Brillouin scattering light, I
prepresent the laser beam intensity of incident, g
0represent stimulated Brillouin scattering gain coefficient, l represents the interaction length between stimulated Brillouin scattering light and the laser of incident.
For general nanosecond and femtosecond or picosecond laser, what its pulse length was the longest should be nanosecond laser, for the laser beam of several nanosecond pulse length, its pulse length having is about 2 meters of left and right (for example common water, the transmission mediums such as optical fiber), so wherein the longest interaction length is also the half (because stimulated Brillouin scattering light is contrary with the direction of propagation of former laser beam) of pulse length, also be 1 meter of left and right, in this length or shorter distance, for common optical transmission medium used, can ignore the decay of laser beam, also think I
pbe a constant, stimulated Brillouin scattering gain coefficient g
0only relevant with the material behavior of Laser Transmission medium, it is a constant, and we suppose that the occupied pulse length of S (or P) polarization state is x, and the actual interaction length of this polarization state should be so
and the occupied length of P (or S) polarization state should be just
its actual interaction length is
wherein c represents the light velocity, and n represents the medium refraction index that laser beam is propagated therein, the pulse width that T is pulse laser beam, and the stimulated Brillouin scattering light that this pulse laser beam produces in medium is so strong
wherein I
ssrepresent total stimulated Brillouin scattering intensity that intrafascicular two polarization states of this pulse laser (P polarization and S polarization state) produce,
the stimulated Brillouin scattering light that expression S (or P) polarization state produces is strong,
the stimulated Brillouin scattering light that expression P (or S) polarization state produces is strong, to I
ssdifferentiate obtains extreme value and can obtain, when
time pulse laser beam total excited Brillouin light intensity of producing obtain extreme value, carrying out mathematical analysis according to analysis above, can to obtain this extreme value be minimum value, can draw so such conclusion, a half that occupies whole pulse length when a kind of polarization state (S or P polarization state) can obtain best inhibition, is also Fig. 3 g and the shown situation of Fig. 3 h.
Therefore, for paired pulses laser beam realizes good stimulated Brillouin scattering inhibition, we just should make pulse laser beam pass wave plate rotating disk to occur Fig. 3 h or the shown effect of Fig. 3 g afterwards in using wave plate rotating disk to carry out stimulated Brillouin scattering inhibition, when pulse laser beam is through after wave plate rotating disk, orthogonal two polarization states have occupied the half of pulse laser beam length separately, the laser beam with this polarization state distribution has had stimulated Brillouin scattering inhibit feature, in the time that transmitting in the transmission mediums such as optical fiber, such laser beam can play good inhibiting effect to the stimulated Brillouin scattering in transmission medium.
The present invention includes:
A kind of device that utilizes rotating wave plate suppressor pulse laser stimulated Brillouin scattering, comprise wave plate rotating disk, described wave plate rotating disk comprises the wave plate rotating around turning axle, rotate a circle on formed disk around turning axle at described wave plate, described wave plate rotating disk comprises the half-wave plate that several distribute about axisymmetry, and between adjacent half-wave plate, there is airspace or full-wave plate, it is characterized in that: the full-wave plate between half-wave plate and half-wave plate or air-gap have identical shape and size, then at the uniform velocity wave plate rotating disk is rotated, make pulse laser beam pass orthogonal two linear polarization after wave plate rotating disk to occupy separately the half of pulse laser pulse length.
According to one of them embodiment, the wherein said half that occupies separately pulse length is the continuous half that occupies pulse length of each polarization state.
According to one of them embodiment, the wherein said half that occupies separately pulse length is two orthogonal linear polarization have occupied pulse length separately half in the mode of alternative arrangement.
One is utilized wave plate rotating disk suppressor pulse laser stimulated Brillouin scattering method, make pulse laser beam pass the at the uniform velocity wave plate rotating disk of rotation, described wave plate rotating disk comprises the wave plate rotating around turning axle, rotate a circle on formed disk around turning axle at described wave plate, described wave plate rotating disk comprises the half-wave plate that several distribute about axisymmetry, and between adjacent half-wave plate, there is airspace or full-wave plate, full-wave plate between half-wave plate and half-wave plate or air-gap have identical shape and size, when pulse laser beam is through after wave plate rotating disk, orthogonal two polarization states occupy the half of pulse length separately.
According to one of them embodiment, the wherein said half that occupies separately pulse length is the continuous half that occupies pulse length of each polarization state.
According to one of them embodiment, the wherein said half that occupies separately pulse length is two orthogonal polarization states have occupied pulse length separately half in the mode of alternative arrangement.
Brief description of the drawings
Fig. 1 is the schematic diagram of the embodiment of a wave plate rotating disk in prior art;
Fig. 2 is the apparatus structure schematic diagram of controlling stimulated Brillouin scattering in prior art;
Fig. 3 a-3h is the schematic diagram that in the present invention, two kinds of polarization states (S and P) occupy different length in the pulse length of pulse laser beam.
Embodiment
We can obtain analysis by above, in order to obtain the inhibition of good stimulated Brillouin scattering in the whole pulse length of laser beam, what need to accomplish is exactly to make pulse laser beam in the half that is pulse laser beam pulse length through orthogonal two occupied length of polarization state after wave plate rotating disk.
Occupy separately the half of pulse laser beam length in order to realize two orthogonal two polarization states, the most effective the simplest method is exactly that full-wave plate or air-gap between half-wave plate and the half-wave plate first making on wave plate rotating disk has identical shape and size, then at the uniform velocity wave plate rotating disk is rotated.Certainly, half-wave plate also can have different shapes and size from full-wave plate or air-gap, but now just need accurately to control the speed of wave plate rotating disk, to ensure that laser beam is the same through half-wave plate with the time of passing full-wave plate or air-gap, could realize like this two polarization states to occupy separately the half of pulse length.
There is identical shape and size with the full-wave plate between half-wave plate and half-wave plate or air-gap, then describe at the uniform velocity wave plate rotating disk is rotated to obtain the embodiment that orthogonal polarization state occupies half length separately, which comprises two kinds:
One is: use controller (for example digital delay controller) accurately to control for the pulse laser outgoing time of laser instrument and the rotation of wave plate rotating disk, wave plate rotating disk at the uniform velocity rotates, make front half pulse of pulse laser beam through half-wave plate (or full-wave plate or air-gap), rear half pulse is just in time through full-wave plate or air-gap (or half-wave plate), and what such mode realized is the shown situation of Fig. 3 g.For this situation, slightly more complex in control, but the benefit of bringing is also apparent, because in this mode, the polarization state of pulse laser beam is not through changing frequently, substantially application that can paired pulses laser beam exerts an influence, because may require in some applications to change too frequently the polarization state of laser beam.
Another is: half-wave plate and full-wave plate (or air-gap) all have less area, and the rotational speed of wave plate rotating disk is higher, when pulse laser beam is when the wave plate rotating disk, the polarization state of change laser beam that can be repeatedly, is also the shown situation of Fig. 3 h.Make in this way, only need to be at pulse laser beam through wave plate rotating disk before wave plate rotating disk in High Rotation Speed state, the benefit of this mode is exactly the rotating speed that does not need accurately to control wave plate rotating disk, and do not need to coordinate the outgoing time of laser beam yet, relatively simple in control, but the problem of bringing is also clearly, that is to say the polarization state that need to change frequently laser beam, this may cause cannot using in some applications.
In the middle of actual, use which kind of mode, need according to the application requirements of laser beam and be controlled to originally to select.
Claims (1)
1. one kind is utilized wave plate rotating disk to suppress several ps pulsed laser and ns pulsed laser stimulated Brillouin scattering methods, make pulse laser beam pass the at the uniform velocity wave plate rotating disk of rotation, described wave plate rotating disk comprises the wave plate rotating around turning axle, rotate a circle on formed disk around turning axle at described wave plate, described wave plate rotating disk comprises the half-wave plate that several distribute about axisymmetry, and between adjacent half-wave plate, there is airspace or full-wave plate, full-wave plate between half-wave plate and half-wave plate or air-gap have identical shape and size, for the laser beam of several nanosecond pulse length, in this length or shorter distance, for common optical transmission medium used, ignore the decay of laser beam, T is the pulse width of pulse laser beam, the stimulated Brillouin scattering light that this pulse laser beam produces in medium is so strong
wherein I
ssrepresent total stimulated Brillouin scattering intensity that intrafascicular two polarization states of this pulse laser produce,
represent that the stimulated Brillouin scattering light that a kind of polarization state produces is strong,
represent that the stimulated Brillouin scattering light that another polarization state produces is strong, wherein c represents the light velocity, and n represents the medium refraction index that laser beam is propagated therein, and wherein the occupied pulse length of a kind of polarization state is x, to I
ssdifferentiate obtains extreme value and can obtain, when
time pulse laser beam total excited Brillouin light intensity of producing obtain extreme value, use digital delay controller accurately to control for the pulse laser outgoing time of laser instrument and the rotation of wave plate rotating disk, wave plate rotating disk at the uniform velocity rotates, make front half pulse of pulse laser beam just in time pass full-wave plate or air-gap through half-wave plate and rear half pulse, or front half pulse is passed full-wave plate or air-gap and rear half pulse through half-wave plate, when pulse laser beam is through after wave plate rotating disk, orthogonal two linear polarization occupy the half of pulse length separately, there is best stimulated Brillouin scattering inhibit feature through pulse laser beam after described wave plate rotating disk.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201210082401.7A CN102608826B (en) | 2012-03-22 | 2012-03-22 | Device and method for suppressing stimulated Brillouin scattering of pulse laser by use of rotating wave plate |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201210082401.7A CN102608826B (en) | 2012-03-22 | 2012-03-22 | Device and method for suppressing stimulated Brillouin scattering of pulse laser by use of rotating wave plate |
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| Publication Number | Publication Date |
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| CN102608826A CN102608826A (en) | 2012-07-25 |
| CN102608826B true CN102608826B (en) | 2014-09-10 |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| FI74371C (en) * | 1982-06-04 | 1988-01-11 | British Telecomm | Optical transmission. |
| CN102087452B (en) * | 2010-12-13 | 2013-02-06 | 华北电力大学（保定） | Device and method for suppressing stimulated Brillouin scattering by using rotating wave plate |
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