CN1293401C - Hollow circular truncated cone laser optical fibre coupler - Google Patents

Abstract

The present invention relates to a hollow circular truncated cone laser optical fiber coupler which belongs to the technical field of high power and energy laser optical fiber coupling devices. The existing coupling devices can not be qualified of coupling optical fiber and laser of which the pulse peak power reaches a megawatt level. The present invention provides the coupler having a hollow circular truncated cone structure. The working chamber of the coupler is in the shape of a hollow circular truncated cone. The lower bottom surface of the circular truncated cone is a light incoming surface, the upper bottom surface is a light outgoing surface, and the conical surface is a reflecting surface. The light incoming surface, the light outgoing surface and the space between the light incoming surface and the light outgoing surface all use air as a medium. The light outgoing surface is coincident with the light input end surface of the optical fiber. The coupler not only automatically resists light injury but also avoids the damage of the coupling optical fiber due to the uniform power density of laser light spots coupled to the light incoming end of the optical fiber. The coupler can be used for coupling optical fiber and high power and energy laser beams which are output by high power lasers such as Nd: YAG lasers.

Description

Hollow round platform laser optical fibre coupler

Technical field

The invention belongs to high power, intensity laser optical fiber coupling device technical field.

Background technology

In the prior art, application number is that 02104969.6 Chinese patent application and the patent No. are that the ZL99227472.9 Chinese patent has been put down in writing two kinds of fiber couplers respectively, the common issue with that they will solve is geometrical axis and the laser beam optical axis coincidence that how to make optical fiber, to improve coupling efficiency.But, in these two kinds of technical schemes, all contain the common technology measure of existing laser fiber coupling, see shown in Figure 1, adopt lens 1, be placed on optical fiber light inputting end 2 before, light inputting end 2 is made solid and is had the shape of certain taper, disposable finishing when making optical fiber 3, the conical surface on every side also is a kind of workplace.Laser beam is behind lens 1 optically focused, and incident light inputting end 2 imports optical fiber 3 into, finishes coupling.Lens 1 are main coupled apparatuses, and light inputting end 2 is the coupled apparatuses of assisting.Laser beam, lens 1, light inputting end 2 and optical fiber 3 are coaxial.With the more approaching prior art of the present invention be that application number is that the disclosed key name of a Japanese application for a patent for invention of flat 4-267424 is called the technical scheme of " optically coupled device ", see shown in Figure 2, the inside of optically coupled device 5 is one and is round table-like light guide section 6, in the light guide section 6 can be air dielectric or other light-conductive medias, first opening 7 of light guide section 6 is the round platform upper bottom surface, light-emitting window for optically coupled device 5, dock with the coupled end face of optical fiber 8, the two has the bore of coupling, second opening 9 of light guide section 6 is the bottom surface of round platform, be the light inlet of optically coupled device 5, light guide section 6 is coaxial with optical fiber 8, and light source O is positioned on this axis.The technical matters that this coupling device will solve is that the coupling efficiency of the semiconductor laser dispersed and optical fiber is lower.The principal character of this technical scheme be light inlet promptly the bore of second opening 9 realize improving the purpose of coupling efficiency thus greater than the i.e. bore of first opening 7 of light-emitting window.Coupling process is that the major part of the laser that sends from light source O is reflected into into optical fiber 8 by the reflection conical surface 10 of light guide section 6, and wherein has major part can enter optical fiber 8 through twice or twice above reflection, as earlier through an A, again through a B reflection.This coupling device is just like a funnel.

Summary of the invention

Preceding two kinds of technology still can realize the coupling of continuous laser and single-mode fiber preferably.; there is such shortcoming in it; see shown in Figure 1; on the end face 4 of light inputting end 2, the power density non-uniform Distribution of incident light is the closer to the center; power density is big more; when the peak power of pulse laser reached the megawatt order of magnitude, its light injury threshold of multimode optical fiber was lower than this performance number, must cause the device damage.Sometimes this damage also can occur on the lens 1.And the third technology is not certain coupling that is fit to parallel high power, intensity laser and optical fiber.In order to realize the coupling of parallel high power, intensity laser and optical fiber, we have invented a kind of hollow round platform laser optical fibre coupler.

The present invention's scheme is seen shown in Figure 3, part same as the prior art is, its working chamber of said coupling mechanism is hollow round table-like, the round platform bottom surface is an incidence surface 11, upper bottom surface is an exiting surface 12, the conical surface is a reflecting surface 13, between incidence surface 11 and exiting surface 12 and the two all is medium with the air, exiting surface 12 overlaps with the light input end face of optical fiber 14, difference from prior art is that said coupling mechanism is used for the coupling of parallel high power, intensity laser and optical fiber 14, and, see shown in Figure 4

$\sin \mathrm{\α}=\sqrt{n_1^2-n_2^2}$

$h=\frac{D}{2}\sqrt{\frac{1+n_1^2+n_2^2}{n_1^2-n_2^2}}.$

When realizing the laser fiber coupling with the present invention's coupling mechanism, can be without lens light gathering, laser beam is the incident coupling mechanism directly.More weak edge light beam a reflexes to exiting surface 12 through reflecting surface 13 and locates near the axle center in the laser beam, the moderate intermediate beam b of laser beam intensity reflexes to exiting surface 12 through reflecting surface 13 and locates away from the axle center, edge light beam a, intermediate beam b only promptly enters optical fiber 14 through primary event, and stronger central light beam c shines directly into the centre of exiting surface 12 in the laser beam, overlap with the reflected light of more weak edge light beam a and neutralize, finally form power density near consistent hot spot at exiting surface 12, if the laser beam peak power is very high, can not surpass the light laser of its light injury threshold yet, thereby overcome the shortcoming of prior art in the local formation of optical fiber 14 light input end faces.For example, for adjusting Q pulse laser, pulse width is 10ns, and peak power reaches 10 ⁶W is 1～10 μ m with the focus diameter after the lens focus of prior art, and the average power density on the focus can reach 10 ^12～13W/cm ², higher in the focus center power density.With the present invention's hollow round platform laser optical fibre coupler, the hot spot power density that forms at exiting surface 12 places only is 10 ^8～9W/cm ², and the light injury threshold of multimode optical fiber is 10 ¹⁰W/cm ², therefore, can not damage optical fiber.

Description of drawings

Fig. 1 is existing laser fiber coupling technique synoptic diagram.Fig. 2 is it " optically coupled device " synoptic diagram of prior art.Fig. 3 is the present invention's hollow round platform laser optical fibre coupler spare and an and optical fiber coupling synoptic diagram.Fig. 4 is the present invention's one example schematic.

Embodiment

See Fig. 3, shown in Figure 4, the present invention's laser optical fibre coupler can be made of quartz, optical glass or metal.It is round table-like to be made into hollow thin-wall, and as shown in Figure 3, it is round table-like also can being made into the inner space, and it is cylindric that the outside is, and the two is coaxial, and as shown in Figure 3, second kind of scheme can be guaranteed the stability of 13 shapes of reflecting surface.Reflecting surface 13 is workplaces of coupling mechanism, requires to have the good optical reflecting properties, earlier it is processed optical mirror plane, then, according to the difference of the optical maser wavelength that is coupled, can plating reflectance coating or dielectric reflection film.The aperture D of incidence surface 11 and the aperture of laser facula are complementary, and the aperture d of exiting surface 12 and the numerical aperture sin α of optical fiber 14 are complementary.The high h of aperture D, d and hollow round platform has determined the tapering of reflecting surface 13, the core material of this tapering and optical fiber 14, the refractive index n of cladding ₁, n ₂Closely related.

Now lift example explanation the present invention, see shown in Figure 4ly, open a coaxial truncated cone-shaped hole along axis in copper cylindric blank, round platform bottom surface aperture D is of a size of 6mm, and round platform upper bottom surface aperture d is 0.5mm.The round platform conical surface is gold-plated.Ou He optical fiber 14 core material refractive index ns with it ₁Be 1.626, the cladding refractive index n ₂Be 1.510, air refraction is n ₀Coupling mechanism exiting surface 12 is coaxial with the light input end face of optical fiber 14, overlap.Laser beam edge light beam a shines on the reflecting surface 13, and (just refractive index is respectively n to its reflected light a ' at coupling mechanism exiting surface 12 as incident light ₀, n ₁Two kinds of light medium interfaces) refraction, refract light a " is respectively n as incident light in refractive index ₁, n ₂Two kinds of light medium interfaces (just optical fiber 14 core materials, two kinds of light medium interfaces of cladding) reflection, and then transmission in optical fiber 14.Realize above-mentioned smooth communication process, the last factor of the tapering of decision reflecting surface 13, just the value of the high h of hollow round platform can be tried to achieve by following derivation computation process:

∵n ₁Sinθ ₁＝n ₂， θ ₁+β＝90°

Wherein: θ ₁The be incident light a refraction angle of " incident angle, β is refract light a "

∴ $\sin \mathrm{\α}=\sqrt{n_1^2-n_2^2}$

Wherein: α is the incident angle of incident light a '

∵ again $\sin \mathrm{\α}=\frac{\frac{D}{2}}{\sqrt{{\left(\frac{D}{2}\right)}^2+h^2}}...\left(1\right)$

Then $\sqrt{n_1^2-n_2^2}=\frac{\frac{D}{2}}{\sqrt{{\left(\frac{D}{2}\right)}^2+h^2}}$

$h=\frac{D}{2}\sqrt{\frac{1+n_1^2+n_2^2}{n_1^2-n_2^2}}...\left(2\right)$

With each numerical value substitution (2) formula, the value that draws the high h of hollow round platform is 3.9238mm, should be worth substitution (1) again, the value that draws the incident angle α of incident light a ' be 37 ° 4 '.This hollow round platform laser optical fibre coupler can realize that Nd:YAG laser wavelength λ is the laser beam of 1.06 μ m and the coupling of optical fiber.

Claims (1)

1, a kind of laser optical fibre coupler, laser beam converges after by its working chamber, working chamber has conical surface workplace, its working chamber of said coupling mechanism is round table-like, and the round platform bottom surface is incidence surface (11), and upper bottom surface is exiting surface (12), the conical surface is reflecting surface (13), between incidence surface (11) and exiting surface (12) and the two all is medium with the air, and exiting surface (12) overlaps with the light input end face of optical fiber (14), it is characterized in that:

①

A, said coupling mechanism are used for the coupling of parallel high power, intensity laser and optical fiber (14),

$B,\sin \mathrm{\α}=\sqrt{n_1^2-n_2^2},$

$C,h=\frac{D}{2}\sqrt{\frac{1+n_1^2+n_2^2}{n_1^2-n_2^2}},$

In above-mentioned formula, α is the numerical aperture angle of optical fiber (14), n ₁Be the refractive index of optical fiber (14) core material, n ₂Be the refractive index of optical fiber (14) cladding, D is the aperture of incidence surface (11), and h is the height of hollow round platform;

2. working chamber is hollow, is light-conductive media with the air.

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