CN102292883A

CN102292883A - Two-stage brightness converter

Info

Publication number: CN102292883A
Application number: CN2010800052788A
Authority: CN
Inventors: J-N·马兰; S·沙蒂格尼
Original assignee: Coractive High Tech Inc
Current assignee: Coractive High Tech Inc
Priority date: 2009-01-23
Filing date: 2010-01-19
Publication date: 2011-12-21
Also published as: CA2749988C; WO2010083595A1; JP2012516040A; CA2749988A1

Abstract

There is provided a two-stage brightness converter. A first brightness conversion stage has a laser cavity having a first optical waveguide doped with an active ion defining a first optical band with optical absorption, a second optical band with optical absorption and optical gain, and a third optical band with optical gain. The first laser cavity is pumped with a pump power having a wavelength in the first optical band to generate an intermediate optical signal in the second optical band. A second brightness conversion stage which is in cascade with the first brightness conversion stage comprises a second optical waveguide doped with the same active ion. The second brightness conversion stage is pumped with the intermediate optical signal to obtain a high brightness optical signal in the third optical band.

Description

Twin-stage luminance transformation device

The cross reference of related application

The application requires the priority of the U.S. Provisional Application 61/146,812 of submission on January 23rd, 2009, by reference its specification is incorporated herein.

Technical field

This specification relates to the generation of light signal, more specifically, relates to luminance transformation.

Background technology

Nowadays, fiber laser is owing to its compactedness, reliability, operating efficiency and high-output power level thereof develop into the most strong solid-state laser technology.Fiber laser can be regarded as single-stage luminance transformation device.

A kind of approach of design luminance transformation device uses laser cavity (referring to " 1.3kW Yb-doped fiber laser with excellent beam quality " Proc.of CLEO 2004 of people such as for example A.Liem, CPDD2, Vol.2, pp.1067-1068, (2004)).In such luminance transformation device, use conic optic fiber beam (TFB) that a large amount of multimode pumping diode-coupled are arrived in the rear-earth-doped doubly clad optical fiber (DCOF), wherein known TFB also is the pumping wave multiplexer.Use Fiber Bragg Grating FBG (FBG) to form laser cavity by each end place to produce laser effect at DCOF.Usually, use high reflectance FBG, and use antiradar reflectivity FBG, so that only partly reflected signal and permission are extracted part power from this chamber in output place of laser cavity in the input of laser cavity.By the doping core absorptive pumping power of DCOF, and produce the high-luminance light signal.In theory, output power of laser is directly proportional with pump power.

The another kind of approach of design luminance transformation device uses master oscillator power amplifier (MOPA) (referring to for example Y.Jeong, people such as J.K.Sahu " Ytterbium-doped large-core fiberlaser with 1.36kW continuous-wave output power; " Optics Express, V.12no.25, pp 6088-6092, (2004)).Owing to need more multi-part, the MOPA configuration is more complicated luminance transformation device.MOPA is made of laser diode, and this laser diode is known as seed (seed), is coupled to the cascade image intensifer level of given number.Typically inserting optical isolator between the laser diode and the first image intensifer level and between each image intensifer level, avoiding any meeting with protection laser diode and each amplifier stage and cause the back reflection that damages.The principle of MOPA does not rely on laser effect.Cascade by amplifier stage is exaggerated from the light signal of laser diode, up to the power output that obtains to wish.Each image intensifer level typically is made of the doped optical waveguide of using a plurality of pump diode pumpings, uses TFB and described a plurality of pump diodes are coupled to fiber waveguide.

These two kinds of configurations have been used to make fiber laser, and nowadays, the fiber laser with power output of thousands of watts becomes a reality.Yet these configurations have some restrictions.

About the configuration based on laser cavity, a shortcoming of this technology relates to the physical constraints of the Maximum pumping that can be used for this system, and this is conclusive in high-capacity optical fiber laser.The high-high brightness that this restriction has two cause: TFB and produced by single emission pump diode.TFB realizes that the pump power that will propagate is coupled to the optics in the single optical fiber (being called signal optical fibre) in a plurality of optical fiber (being called the pumping arm).Yet, the number of spendable pumping arm is had theoretical restriction.The prior art state is set at 31 with this value.Though can increase the number of pumping arm by two TFB of cascade, the maximum of available pumping arm is restricted to 49 at this moment.This restriction of the number of pumping arm is caused restriction to available Maximum pumping, consider the state of the single emission pump diode of prior art, this available Maximum pumping is near 1kW.Another restriction relevant with TFB is its thermal limit.TFB causes inserting loss.The pump power of loss is followed packed absorption and is caused temperature to raise, and the temperature rising causes component failure.Usually, when the insertion loss of TFB was about 0.1dB, the Maximum pumping that can be used for safety operation was about 1kW.At last, the brightness of pump diode has also limited Maximum pumping.The original intensity of pump diode should carefully be chosen as to have efficiently and powerful system.Can pay more powerful pump diodes is that commerce can get, but sizable (that is) transmission optical fiber, 600 μ m or higher, the brightness of these pump diodes is low having.This make efficiently and the development of powerful fiber laser complicated.

Another shortcoming based on the configuration of laser cavity is the Shu Pinzhi that can get.Ratio between the area of the absorption of the pump power of propagating in the inner cladding of DCOF and the area of its core and its inner cladding is proportional.In order to adapt to the use to the low-light level pump diode, the radius of inner cladding should increase, this thereby reduced the pump light absorption.For this effect of contending with, can increase the radius of fiber core.Unfortunately, this solution causes the deterioration of the Shu Pinzhi of signal.

At last, another shortcoming based on the configuration of laser cavity relates to heat management.In fact, have propagation loss in DCOF, this produces heat.In laser cavity luminance transformation device, usually in the surrounding layer of DCOF, use the suitable numerical aperture (NA) of low refractive index polymer to realize to realize with silicon dioxide.Though pure silicon dioxide can be handled high to 1500 ℃ and higher temperature, low refractive index polymer only can be handled the highest about 120 ℃ temperature.Therefore, pump power can not be risen to above the specific limited of polymer with without undergoing the damage that causes by heat.

Above-mentioned about based on the configuration of laser cavity the restricted luminance transformation device configuration that also is applicable to based on MOPA.In addition, existence is from other restrictions of the complexity of system.At first, owing to MOPA is made of the cascade of amplifier stage, compare with the laser cavity configuration, it is more expensive usually.Secondly, should be especially carefully to control the gain of each amplifier stage fully, so that obtain optimum and operation efficiently.The 3rd, also should use optical isolator that each amplifier stage is isolated from each other.Yet, at present, do not have the commercial available isolator that can handle the optical power that surpasses tens watts.When reaching such power level, MOPA does not utilize isolator and works, and this finally can cause significant inefficacy.

Consider the defective of above-mentioned prior art, exist and use the low-light level pump diode to realize the demand of the luminance transformation device of good Shu Pinzhi allowing.

Summary of the invention

According on the one hand, provide a kind of twin-stage luminance transformation device.The first luminance transformation level has first laser cavity, described first laser cavity has first fiber waveguide that is doped with active ion, and described active ion limits has first optical band of light absorption, the 3rd optical band that has second optical band of the light absorption and the gain of light and have the gain of light.Apparatus has described first laser cavity of the pump power pumping of the wavelength in described first optical band, to produce the light signal between two parties in described second optical band.Comprise second fiber waveguide that is doped with identical active ion with the second luminance transformation level of the described first luminance transformation level cascade.With the described second luminance transformation level of described light signal between two parties pumping, to obtain the high-luminance light signal in described the 3rd optical band.

According on the other hand, a kind of luminance transformation device is provided, it comprises: the first luminance transformation level has the Shu Pinzhi of laser cavity with raising low-light level pump signal, thereby the light signal between two parties with high efficiency and good heat management is provided; And the second luminance transformation level, be used for described converting optical signals is between two parties become to have the high-luminance light signal of high efficiency and good heat management.

The twin-stage luminance transformation device that is provided allows to utilize the low-light level pump diode to produce the light signal with good Shu Pinzhi when keeping the high-efficiency heat pipe reason.

According to an embodiment, the described second level of described twin-stage luminance transformation device is laser cavity, and according to another embodiment, the configuration based on master oscillator power amplifier (MOPA) is used in the described second level of described twin-stage luminance transformation device.

Under specific circumstances, described twin-stage luminance transformation device uses full glass doubly-clad optical fiber (DCOF).Owing in DCOF, do not use low refractive index polymer, so they can withstand high temperatures.

In addition, the twin-stage luminance transformation device that is provided allows to use utmost point low-light level pump diode.Therefore, compared with prior art, twin-stage luminance transformation device allows to increase maximum available pump power.

The luminance transformation device that is provided also allows to use single pumping source, thereby only needs one to be used for the launch point of pump power and to have eliminated needs to conic optic fiber beam (TFB) or any other pumping wave multiplexer.

According on the other hand, provide a kind of pumping generator that is used to produce diode pumping power.Described pumping generator comprises laser cavity, and described laser cavity has the fiber waveguide that is doped with active ion.Described fiber waveguide contains first optical band with light absorption, the 3rd optical band that has second optical band of the light absorption and the gain of light and have the gain of light.Described pumping generator also comprises the pumping source that is coupled to described laser cavity, and the main pump Pu power that described pumping source is used for producing described first optical band is with the described laser cavity of pumping, so that produce the diode pumping power in described second optical band.Described fiber waveguide is a multimode at the wavelength place corresponding to described diode pumping power, so that described diode pumping power is propagated in described fiber waveguide with multimode.

According to another aspect, provide a kind of method that is used to produce the high-luminance light signal.Described method comprises: i) have the laser cavity of first fiber waveguide that is doped with active ion with the pump power pumping, described active ion limits has first optical band of light absorption, the 3rd optical band that has second optical band of the light absorption and the gain of light and have the gain of light.Described pump power has the wavelength in described first optical band; Ii) in described laser cavity, produce the light signal between two parties in described second optical band as the result of described pumping; Iii) be doped with second fiber waveguide of identical active ion with the pumping of described light signal between two parties; Iv), in described second fiber waveguide, obtain the high-luminance light signal in described the 3rd optical band as result with the pumping of described light signal between two parties; And v) export described high-luminance light signal from described second fiber waveguide.

Description of drawings

Fig. 1 is that example goes out the schematic diagram based on the twin-stage luminance transformation device of the cascade of two laser cavities;

Fig. 2 is the sectional view of the general example of doubly clad optical fiber (DCOF);

Fig. 3 is the schematic diagram of the relative size of the fiber waveguide of delivery optical fiber, the first order of the pump diode of the example luminance transformation device that goes out Fig. 1 and partial fiber waveguide;

Fig. 4 illustrates the emission cross section of emission cross section figure and rare earth ion ytterbium and the figure of absorption cross-section;

Fig. 5 is the figure that illustrates along the distribute power of the fiber waveguide of the doping of the first order of exemplary luminance transformation device;

Fig. 6 is the figure that illustrates along the particle beams counter-rotating of the fiber waveguide of the doping of the first order of exemplary luminance transformation device;

Fig. 7 is the figure that illustrates along the intrinsic gain spectral concentration of the fiber waveguide of the doping of the first order of exemplary luminance transformation device;

Fig. 8 is the figure that illustrates along the distribute power of the fiber waveguide of the partial doping of exemplary luminance transformation device;

Fig. 9 A is that example goes out the schematic diagram based on the twin-stage luminance transformation device of the cascade of two laser cavities separating by mould field adapter (MFA);

Fig. 9 B is the schematic diagram of the example of example depanning field adapter (MFA);

Figure 10 A is the schematic diagram based on the luminance transformation device of MOPA that example goes out to use cascade amplifier; And

Figure 10 B is the publish picture schematic diagram of one of amplifier of cascade of converter of 10A of example in more detail.

Notice that in institute's drawings attached kind, similar reference number is represented similar feature.

Embodiment

Before describing specific embodiment, should look back the definition of brightness.The brightness of light source is with W/ (sr.m ²) be unit representation, and be defined as follows:

B = \frac{P}{{NA}^{2} \cdot π \cdot A} - - - (1)

Wherein P is the transmitting power from the area of size A, and NA is a numerical aperture.

The state of the pump diode of prior art is typically carried the power of 20W magnitude in the optical fiber of the NA of the core diameters with about 100 μ m and about 0.15.This causes for the state of prior art pump diode typical 3.6 * 10 ¹⁰W/ (sr.m ²) brightness B.For the low-light level pump diode of carrying about 500W in the optical fiber of the NA of the diameter with about 600 μ m and about 0.22, brightness is 1.1 * 10 ¹⁰W/ (sr.m ²).The low-light level pump diode is typically carried bigger power but is had compromise to brightness, and this is main problem when using single-stage luminance transformation device.

With reference now to accompanying drawing,, Fig. 1 shows the twin-stage luminance transformation device 100 based on the cascade of the first order 102 and the second level 104, and the first order 102 and the second level 104 comprise laser cavity separately.Attention: the welding between symbol " x " the expression parts that place at the diverse location place in Fig. 1.

Use the low-light level pump diode 106 pumping first order 102, this low-light level pump diode 106 produces available pump power A at delivery optical fiber 108 places.The first order 102 uses rear-earth-doped doubly clad optical fiber (DCOF) 110 as gain media, more specifically, and ytterbium doped silica DCOF.High reflectance Fiber Bragg Grating FBG (FBG) 112 is fused in the input of DCOF 110, and antiradar reflectivity FBG 114 is fused output place at DCOF 110, to form laser cavity.Delivery optical fiber 108 is welded to FBG 112 to inject pump power A to the first order 102.The first order 102 uses pump power A to produce optical signalling B between two parties.Output place at FBG 114 can obtain optical signalling B between two parties.

The second level 104 receives the B of light signal between two parties from the first order 102, and uses between two parties that light signal B produces high-luminance light signal C as pumping.The same with the first order 102, the second level 104 comprises the rear-earth-doped DCOF 120 that is used as gain media.The rare earth ion that uses in DCOF 120 is identical with the rare earth ion that uses in DCOF 110, that is, and and ytterbium.DCOF 120 is based on silicon dioxide equally.High reflectance FBG 122 is fused in the input of DCOF 120, and antiradar reflectivity FBG 124 is fused output place at DCOF 120, to form laser cavity.The second level 104 is welded to the first order 102 to receive the B of optical signalling between two parties from the first order 102.Can obtain the high-luminance light signal C that produced in output place of FBG 124.

In whole explanation, relate to the rare earth ion ytterbium of the dopant that is used as in the gain media.Yet, note: use ytterbium herein as an example, can use other ions equally such as erbium or any other active ion.

Low-light level pump diode 106 typically produces hundreds of watts pump power A in having such as the optical fiber of 600 μ m or bigger big core diameters.By using such low-light level pump diode, in this secondary luminance transformation device 100, only need a pump diode 106, therefore do not need conic optic fiber beam (TFB).This has solved at least some problems in the intrinsic problem of these parts of discussing simultaneously in background technology.Consider to be doped with the silica optical fiber of ytterbium, the wavelength of pump diode 106 is in 915 to 976nm wave band.Attention: though the pumping in the 915-976nm wave band is more effective, the pump absorption in the optical fiber that ytterbium mixes also is being possible from about wave band of 880 to 985nm.

The first order 102 is designed in wavelength X ₁The place produces and is called as the Laser emission of light signal B between two parties.As described below, in this case, the wavelength X of light signal B between two parties ₁Be selected as being in about 1020 to 1030nm the optical band between two parties.FGB 112 and FGB 114 are at λ ₁The place all has peak reflectivity so that laser cavity is stable at this wavelength place, and, in the design of FGB 112 and FGB 114, pay special attention to all to be reflected by FGB 112 and FGB114 with all optical modes of guaranteeing to keep by multimode DCOF 110.

Attention: because the first order 102 is used to produce the light signal as the pumping in the second level 104, so the first order 102 is also referred to as the pumping generator.

The second level 104 be received in the light signal between two parties that output place of the first order 102 can get and use this between two parties light signal as pumping.The second level 104 is designed in wavelength X ₂The place produces Laser emission.The Laser emission of this high brightness and high Shu Pinzhi is called as high-luminance light signal C in this article.As described below, wavelength X in this case ₂Be selected at 1080nm.FGB 122 and FGB 124 are at λ ₂The place all has peak reflectivity to form laser cavity and wavelength stabilized laser is arrived λ ₂Attention: though the first order 102 and the second level 104 all use ytterbium doped silica DCOF as gain media, size and the characteristic of DCOF 110 and DCOF 120 differ from one another.

Before the concrete size that DCOF 110 and DCOF 120 are discussed, in Fig. 2 example the schematic diagram of general DCOF.DCOF can be considered to the stack of two waveguides, that is, and and the stack of signal wave-guides and multimode pump waveguide.DCOF comprises core 202, inner cladding 204, surrounding layer 206 and the sheath 208 that is doped with active ion.Signal wave-guides is made of core 202 and inner cladding 204, so that use inner cladding 204 steering signal in core 202.The multimode pump waveguide is made of inner cladding 204 and surrounding layer 206.Use surrounding layer 206 in inner cladding 204, to guide pump power.Sheath 208 is around surrounding layer 206.So DCOF is can be with the brightness of propagating in pump waveguide low and restraint brightness height and the high signal of Shu Pinzhi that inferior multimode pumping Power Conversion becomes to propagate in signal wave-guides.Pump power is injected in the pump waveguide, and between its propagation periods, pump power is overlapping in position that is absorbed by active ion and signal wave-guides.At last, stimulated emission takes place in signal wave-guides.

Fig. 3 shows the relative size of the DCOF 120 of the DCOF 110 of delivery optical fiber 108, the first order 102 (not shown in Fig. 3) of pump diode 106 (not shown in Fig. 3) and the second level 104 (not shown in Fig. 3).Delivery optical fiber 108 has core 302 and covering 304.DCOF110 has core 312, inner cladding 314 and surrounding layer 316.DCOF 120 has core 322, inner cladding 324 and surrounding layer 326.Attention: FBG 112 and FBG 114 have 110 matched size with DCOF, and FBG 122 and FBG 124 have 120 matched size with DCOF.For the sake of clarity, not shown FBG 112,114,122 and 124 in Fig. 3.

The pump power A that can get at delivery optical fiber 108 places is coupled to the inner cladding 314 of DCOF 110.DCOF 110 is designed to make the diameter of inner cladding 314 to mate the diameter of the core 302 of delivery optical fiber 108, so that obtain optimum coupling.In one embodiment, this diameter is 600 μ m.The diameter of core 312 is the magnitude of 100 μ m or higher.Therefore DCOF 110 is with plural mould operation.Because the diameter of the core 312 of DCOF110 is less than the diameter of the core 302 of delivery optical fiber 108, the brightness of light signal B is between two parties compared with pump power A and is improved.

In addition, the diameter of the inner cladding 324 of DCOF 120 is designed to mate the diameter of the core 312 of DCOF 110.Ratio between the area by making inner cladding 324 and the area of core 322 can make the diameter of core 322 remain enough little of to guarantee the single mode operation of DCOF 120 in tens percent scope.The single mode operation provides the light signal C of the high diffraction limited system of brightness.Attention: can use multimode DCOF 120, but should be specifically noted that this moment with single mode state of operation DCOF 120 to obtain the bundle of diffraction limited system in its output place.Partial slight plural mould operation also is possible.

Attention: the DCOF 110 of the foregoing description and 120 parameter allow with all-glass fiber be used for DCOF 110 and DCOF 120 the two.Yet, note: still can adopt the DCOF that uses low refractive index polymer or polysiloxanes.Should also be noted that: above-mentioned size provides as an example, and these vary in size are to be suitable for any other practical application.

The luminance transformation device that is provided allows the flexibility aspect the selection of the characteristic of employed fiber waveguide.When using DCOF, the numerical aperture (NA) of the core 312 of the DCOF 110 of the first order and diameter can carefully be chosen as the core that makes among the partial DCOF 120 and absorb maximum and keep the inner cladding 324 of partial DCOF 120 enough little simultaneously.It is enough little of the operation of single mode in the second level that so the core 322 of partial DCOF 120 can keep, thereby output bundle of the diffraction limited system of providing.

Fig. 4 shows the absorption cross-section 410 and the emission cross section 420 of rare earth ion ytterbium, and is used to describe the operation of the twin-stage luminance transformation device 100 of Fig. 1.Absorption cross-section 410 is relevant with the gain of light with emission cross section 420, to its research we is understood at the laser cavity internal signal and how to be exaggerated.Fig. 4 also show will be described below, corresponding to three spectral bands of first optical band 431, second optical band 432 and the 3rd optical band 433.First optical band 431 about 915 and 976nm between extend, and corresponding to the light absorption wave band.Second optical band 432 about 1020 and 1030nm between extend, wherein absorb and gain that the two all takes place.The 3rd optical band 433 is extended near the 1080nm corresponding to gain of light wave band.

In single-stage luminance transformation device, typically carry out pumping in first optical band 431 of between absorption cross-section the highest 915 and 976nm, extending.In the 3rd optical band 433, that is, set wavelength stabilization near the 1080nm then.

Yet, can notice, 1020 and 1030nm between in second optical band 432 of extending absorption cross-section can not ignore, this situation with near 1080nm the 3rd optical band is the same.In second optical band 432, absorb and gain that the two all is possible.For the twin-stage luminance transformation device 100 that uses this wave band especially, this observed result is important.In first optical band 431, that is, 915 and 976nm between, use the low-light level pump diode 106 pumping first order 102, and the first order 102 is designed to produce has second optical band 432 B of light signal between two parties of the wavelength of (promptly about 1020 and 1030nm between).Pump power A propagates in the inner cladding 314 (referring to Fig. 3) of the DCOF 110 that mixes.The B of light signal between two parties that produces in second optical band 432 propagates in core 312 (referring to Fig. 3).The B of light signal between two parties in second optical band 432 has the brightness of comparing improvement with pump power A.Because the absorption in second optical band 432 be can not ignore, the B of light signal between two parties that is produced by the first order 102 can be used to the pumping second level 104 to produce the high-luminance light signal C in the 3rd optical band 433.In addition, the brightness improving in the first order 102 allows the Guangxin core of DCOF 120 is kept enough little of to have the single mode operation in the 3rd optical band 433 (that is, at the 1080nm place).Therefore, because the operation of the single mode of DCOF 120, the second level 104 produces the laser signal of the bundle with diffraction limited system at the 1080nm place.

As mentioned above, though the pumping in 915 to 976nm wave bands is more effective, the pump absorption in the optical fiber that ytterbium mixes also is possible extend to the big wave band of 985nm from about 880nm in.Therefore, first optical band 431 also is extended to this scope.Similarly, second optical band 432 also can be extended to from about 1000nm to 1050nm, absorbs in this scope and gain all exists.The 3rd optical band 433 also is extended to from about 1060nm to 1100nm, and actual gain is possible in this scope.

Twin-stage luminance transformation device 100 has solved limiting to small part in the heat management relative restrictions with fiber laser.At first, as a rule, the DCOF 110 of doping and 120 can be manufactured to all-glass, wherein without any need for low refractive index polymer.In the single-stage luminance transformation device based on laser cavity, the DCOF of doping typically uses low refractive index polymer to mate the NA (it is about 0.46) of the delivery optical fiber of conic optic fiber beam (TFB) with the NA that increases pump waveguide.Yet the low-light level pump diode that most commerce can get has the delivery optical fiber near 0.22 NA, and, owing to do not use TFB in this embodiment, can use light in DCOF 110, to realize 0.22 NA.By in the design of

DCOF

110 and 120, avoiding using low refractive index polymer, eliminated the problem relevant with thermal failure.

In addition, twin-stage luminance transformation device 100 provides the heat management of comparing improvement with above-mentioned prior art arrangement.The quantum efficiency of single-stage luminance transformation device changes between 85% and 90%.Utilize the twin-stage luminance transformation device 100 of Fig. 1, the quantum efficiency of the first order 102 typically changes between 88% and 95%, and the quantum efficiency of the second level 104 typically changes between 88% and 94%.Because higher quantum efficiency causes lower heat to produce, therefore at

different levels

102 and 104, all realized the low-heat generation.Since DCOF 410 typically near or greater than the big core diameters of 100 μ m, realized that in the first order 102 lower heat produces.Since heat produce be inversely proportional to the core radius square, realized in the first order 102 that therefore low heat produces.

Attention: the diameter of core that is used to make the optical fiber of FBG 112 and 114 should mate the diameter of the core of DCOF 110,, typically is the magnitude of 100 μ m that is.Should note: stride across so big core carry out equably FBG write the affiliation be difficult.Yet, notice that owing to unevenly charge to the unequal reflection that causes various patterns and only cause FBG than poor efficiency, therefore striding across this core, to write FBG equably be not enforceable.

Example:

Provide example now according to the specific design of the twin-stage luminance transformation device of Fig. 1.The parameter that should be understood that the converter of stipulating below provides just to example, has many other possible designs to such twin-stage luminance transformation device.

Should carefully design the first order 102 of luminance transformation device, (promptly 1020 and 1030nm between) obtains Laser emission so that in second optical band.Should design the first order 102 for purpose in second optical band, to have the maximum gain spectral concentration, so that obtain the efficient laser emission.

The strong population inversion of utilization in the DCOF 102 of the first order 102 obtains in second optical band such efficient laser emission of (that is, 1020 and 1030nm between).In order to obtain desirable strong population inversion, use the big ratio of short cavity and core diameters and inner cladding diameter, so that obtain the strong absorption of pump power.

In order to obtain the strong absorption of pump power, wish to use heavily doped DCOF.Yet, notice that comprise the crystalization that too much rare earth ion can cause glass matrix in glass matrix, the result increases background loss.Under the situation of ytterbium, 3 * 10 ²⁶To 6 * 10 ²⁶Ion/m ³Concentration be acceptable.In this example, use 3 * 10 ²⁶Ion/m ³Concentration, fiber lengths is 1 meter.

Next, in order to obtain the efficient laser chamber, be important to the selection of the wavelength of pump power.As shown in Figure 4, first optical band 431 of the typical pumping wave band of the optical fiber that mixes corresponding to ytterbium 915 and 976nm between extend.Should note: near the wavelength of Laser emission, this laser is effective more more for the wavelength of pumping.Yet,, need the highly stable pump laser diode of wavelength near the pumping wavelength of 976nm because it is very narrow under this wavelength to absorb bandwidth.Owing to this reason, more properly select the pumping wavelength of 965nm.

Can for example carry the low-light level pump diode of the power of 1000W at 965nm in the delivery optical fiber of the NA of the core diameters with 400 μ m and 0.22 from the Laserline GmbH acquisition that is arranged in Germany.The brightness of such pump diode is 5 * 10 ¹⁰W/ (sr.m ²).

Then, for the diameter of the delivery optical fiber of mating typical low-light level laser diode, the diameter of inner cladding is that the diameter of 400 μ m and core is 100 μ m, so that core is 0.25 to the natural scale of inner cladding.

At last, optical maser wavelength is set to 1027nm.

Fig. 5 shows analog result according to the first order 102 of above-mentioned design to Fig. 7.Use rate of change equation model (rate equation modeling) to carry out this simulation (referring to Rare-Earth-Doped Fiber Lasers and Amplifiers, 2nd Edition, Michel J.F.Digonnet, Marcel Dekker Inc., 2001, p.341-344).

.). Fig. 5 shows along the distribute power of the DCOF 110 of the first order 102; Fig. 6 shows along the population inversion of DCOF 110; And Fig. 7 shows the intrinsic gain spectra density of DCOF 110.As can be seen, population inversion is near 50% in Fig. 6, and this counter-rotating than the double-clad optical fiber laser that typically is used near traditional wavelength place emission 1080nm is strong two to three times.As shown in Figure 7, reach the maximum intrinsic gain of the first order 102 at wavelength place near about 1020nm of the excitation wavelength of 1027nm.Matched well between maximum intrinsic gain and the optical maser wavelength causes 93% good lasing efficiency, and this can observe in Fig. 5.

Now, the second level 104 is transformed into high-luminance light signal C with the B of light signal between two parties at 1027nm place.The diameter of the inner cladding of the DCOF 120 of the second level 104 is selected as mating the diameter of core of the DCOF 110 of the first order 102.Correspondingly, the diameter of the inner cladding of the second level 104 is 100 μ m.In order to obtain the high-luminance light signal C of diffraction limited system, DCOF 104 is designed to single mode.The diameter of core is 15 μ m, and numerical aperture is 0.08, and this causes and 2.405 enough approaching 3.5 v number for the single mode operation of DCOF 120.Ytterbium concentration equals 3 * 10 ²⁶Ion/m ³, when background loss is remained on acceptable level, to obtain good lasing efficiency.

Fig. 8 shows the analog result according to the second level 104 of above-mentioned design.Again, use the rate of change equation model to carry out this simulation.It shows along the distribute power of DCOF 120.Observe 80% efficient in the second level 120, this causes total lasing efficiency of 75%.

The twin-stage luminance transformation device of this example produces the power of 750W, and this NA for 0.08 provides greater than 2 * 10 ¹⁴W/ (sr.m ²) brightness.This corresponding to from pump power A to high-luminance light signal C greater than 4000 times brightness improving.

Fig. 9 A shows the modification of the twin-stage luminance transformation device 100 of Fig. 1.Therefore the twin-stage luminance transformation device 900 of Fig. 9 A and the twin-stage luminance transformation device 100 of Fig. 1 are not repeated in this description similar parts much at one.Twin-stage luminance transformation device 900 comprises pump diode 906, have the first order 902 of DCOF 910 and have the second level 904 of DCOF 920.Twin-stage luminance transformation device 900 comprises additional parts,, is inserted in the mould field adapter (MFA) 930 between the first order 902 and the second level 904 that is.

In certain embodiments, the very poor brightness of pump diode 906, so that the diameter of inner cladding of DCOF 910 that need to increase the first order 902 is to obtain optimum laser effect in second optical band.In this particular context, the ratio between the area of the core of the area of the inner cladding of DCOF 910 and DCOF 920 will reduce, so that it becomes less than one, and therefore the absorption of the power among the DCOF 920 will reduce.A solution is the diameter that increases the core of DCOF 920, but therefore this will cause undesirable plural mould operation of DCOF 920.In order to overcome this problem, between at

different levels

902 and 904, insert MFA 930.As can be seen, MFA is the part of the optical fiber that reduces gradually of diameter in Fig. 9 B of the details of the MFA 930 that draws.It can liken to has large diameter optical fiber and has than the buffering between the optical fiber of minor diameter.Usually, if two diameters are enough approaching, then can seriously do not insert loss ground and realize that this is adaptive.

Attention: have at pump diode under the situation of major diameter delivery optical fiber, can be alternatively or additionally between the pump diode of the first order and DCOF, insert MFA.The minor diameter of the inner cladding of the DCOF of this permission maintenance first order.

Figure 10 A and 10B show another embodiment based on the luminance transformation device 1000 of cascade master oscillator power amplifier (MOPA).In the luminance transformation device of Figure 10 A, be amplified in the laser kind 1002 at 1080nm place by the cascade of the

amplifier

1004,1006 separated by optical isolator 1008.Attention: the number of amplifier can change.Luminance transformation device 100 is basically mainly by being used for each amplifier 1004 shown in Figure 10 B with 1006 configuration and different with the prior art state.Each

amplifier

1004 and 1006 has the first order 1010 and the second level 1020.The first order 1010 is created in the pump power under the wavelength of 1020-1030nm wave band, and it is used for the pumping second level 1020.The second level 1020 is made of the amplifier that uses the pump power that produces in the first order 1010 to amplify kind of laser 1002.

The first order 1010 comprises and is doped with active ion (in this case for ytterbium), uses low-light level pump diode 1014 that it is carried out pumping.Use high reflectance FBG 1016 and antiradar reflectivity FBG1018 to form laser cavity and the emission wavelength of laser is stabilized to the λ that is arranged in the 1020-1030nm wave band ₁Because in wavelength X ₁The laser effect at place obtains beam brightness and improves in the first order 1010, this first order with the luminance transformation device 100 of Fig. 1 is identical.The pump power that produces in the first order 1010 is used to the pumping second level 1020.The second level 1020 constitutes for MOPA and by the DCOF 1022 that is doped with active ion (being ytterbium in this case).Pump power is coupled to DCOF 1022, pumping wave multiplexer 1024.Owing to the beam brightness of the improvement that obtains from the first order 1010, DCOF 1022 can operate with single mode, causes the optimum of laser kind 1002 to amplify.The same with the embodiment of Fig. 1, the use of the twin-stage luminance transformation device in the MOPA configuration of Figure 10 A allows to overcome the pump power restriction, this is that this low-light level pump diode is the pump diode high power of delivery ratio to have better brightness typically because it uses the low-light level pump diode.In addition, the same with the embodiment of Fig. 1, can in the luminance transformation device of Figure 10 A, use full glass DCOF, improve heat management thereby compare with the configuration of prior art.At last, the configuration of Figure 10 A does not need to use TFB equally.More properly use simple pumping wave multiplexer, this has solved limiting to small part in the use relative restrictions with TFB.

Though the embodiment of Miao Shuing uses optical fiber as waveguide herein, should note: can also use the fiber waveguide of any other type, for example planar optical waveguide.

Can also be with other wavelength specific mirrors, film filter for example, substituted for optical fibers Bragg grating (FBG).

Should also be noted that: though, can also use other active ions as dopant herein with reference to the optical fiber that is doped with ytterbium.For example, erbium is spendable a kind of ion, this be because its be presented near 980nm place or the 1480nm first optical band with absorption, absorb and gain between 1520 and the 1550nm that all takes place second optical band and 1550 and 1600nm between the 3rd optical band with gain.Erbium can be used to be created in the low-light level pump diode from 980nm in the first order pumping between two parties of 1520-1550nm wave band, and can be used to by pumping between two parties by in the second level of pumping to produce the signal in the 1550-1600nm wave band.

The embodiment of Miao Shuing uses single high power low-light level pump diode as pumping source herein.Yet should note: it also is possible alternatively using a plurality of pump diodes that have low pump power and the combination of use pumping wave multiplexer separately.

The foregoing description only is intended to exemplary.Therefore, scope of the present invention is intended to only be limited by the appended claims.

Claims

1. luminance transformation device comprises:

The first luminance transformation level, it has laser cavity, described laser cavity has first fiber waveguide, described first fiber waveguide has first core that is doped with active ion, described active ion limits has first optical band of light absorption, the 3rd optical band that has second optical band of the light absorption and the gain of light and have the gain of light, apparatus has described first laser cavity of the pump power pumping of the wavelength in described first optical band, to produce the light signal between two parties in described second optical band; And

The second luminance transformation level, itself and the described first luminance transformation level cascade also have second fiber waveguide, described second fiber waveguide has second core that is doped with described active ion, with the described second luminance transformation level of described light signal between two parties pumping, to obtain the high-luminance light signal in described the 3rd optical band.

2. according to the luminance transformation device of claim 1, the wherein said second luminance transformation level comprises second laser cavity.

3. according to the luminance transformation device of claim 1 or 2, wherein said active ion is a ytterbium.

4. according to the luminance transformation device of claim 3, wherein said first optical band comprises the wavelength between 915nm and the 976nm.

5. according to the luminance transformation device of claim 4, wherein said second optical band comprise 1020 and 1030nm between wavelength.

6. according to the luminance transformation device of claim 5, wherein said the 3rd optical band comprises the wavelength of 1080nm.

7. according to each luminance transformation device in the claim 1 to 6, wherein said first fiber waveguide and described second fiber waveguide comprise full glass doubly-clad optical fiber (DCOF) separately.

8. according to each luminance transformation device in the claim 1 to 7,

Wherein said first fiber waveguide comprises first inner cladding that is used to propagate first core of described light signal between two parties and is used to propagate described pump power;

Wherein said second fiber waveguide comprises second inner cladding that is used to propagate second core of described high-luminance light signal and is used to propagate described light signal between two parties;

And the diameter of wherein said second inner cladding is substantially equal to the diameter of described first core.

9. according to each luminance transformation device in the claim 1 to 8, wherein said first fiber waveguide is a multimode when propagating described light signal between two parties, and wherein said second fiber waveguide is a single mode when propagating described high-luminance light signal.

10. according to each luminance transformation device in the claim 1 to 9, wherein said first laser cavity comprises the high reflectance Fiber Bragg Grating FBG of the input that is positioned at described first fiber waveguide and is positioned at the antiradar reflectivity Fiber Bragg Grating FBG of output place of described first fiber waveguide.

11. according to each luminance transformation device in the claim 1 to 10, further comprise the low-light level pumping source that is coupled to described first laser cavity, it is used to produce described pump power.

12. a pumping generator that is used to produce diode pumping power, described pumping generator comprises:

Laser cavity, it has the fiber waveguide that is doped with active ion, and described fiber waveguide has: have first optical band of light absorption, the 3rd optical band that has second optical band of the light absorption and the gain of light and have the gain of light; And

Be coupled to the pumping source of described laser cavity, its main pump Pu power that is used for producing described first optical band is with the described laser cavity of pumping, so that produce the diode pumping power in described second optical band;

Wherein said fiber waveguide is a multimode at the wavelength place corresponding to described diode pumping power, so that described diode pumping power is propagated in described fiber waveguide with multimode.

13. according to the pumping generator of claim 12, wherein said fiber waveguide comprises full glass doubly-clad optical fiber (DCOF).

14. according to the pumping generator of claim 12 or 13, wherein said active ion is a ytterbium.

15. according to each pumping generator in the claim 12 to 14, wherein said first optical band comprises the wavelength between 915nm and the 976nm.

16. according to the pumping generator of claim 15, wherein said second optical band comprise 1020 and 1030nm between wavelength.

17. a method that is used to produce the high-luminance light signal, described method comprises:

The laser cavity that has first fiber waveguide that is doped with active ion with the pump power pumping, described active ion limits has first optical band of light absorption, the 3rd optical band that has second optical band of the light absorption and the gain of light and have the gain of light, and described pump power has the wavelength in described first optical band;

As the described light signal between two parties that produces in described laser cavity with the result of pump power pumping in described second optical band;

Be doped with second fiber waveguide of described active ion with the pumping of described light signal between two parties; And

As the result of the described light signal between two parties of described usefulness pumping, in described second fiber waveguide, obtain the high-luminance light signal in described the 3rd optical band; And

Export described high-luminance light signal from described second fiber waveguide.

18., further be included in described first fiber waveguide with the described light signal between two parties of multimode propagation according to the method for claim 17.

19., further be included in described second fiber waveguide with the described high-luminance light signal of single mode propagation according to the method for claim 17 or 18.

20. according to each method in the claim 17 to 19, wherein said first fiber waveguide comprises having first core, the full glass doubly-clad optical fiber (DCOF) of first inner cladding and first surrounding layer, and wherein said second fiber waveguide comprises having second core, the full glass DCOF of second inner cladding and second surrounding layer, wherein said method further is included in and propagates described pump power in described first inner cladding, in described first core, propagate described light signal between two parties, in described second inner cladding, propagate described light signal between two parties and in described second core, propagate described high-luminance light signal.