JP2008147699A - Fiber laser and fiber amplifier - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve more oscillation wavelengths in a fiber laser exciting a fiber having a core to which a rare earth element ion is added with a laser diode to generate laser beams. <P>SOLUTION: A GaN-based laser diode 11 excites the fiber 13 having the core to which Er<SP>3+</SP>is added. Laser beams 15 are generated by the transition of<SP>4</SP>S<SB>3/2</SB>→<SP>4</SP>I<SB>15/2</SB>, or<SP>2</SP>H<SB>9/2</SB>→<SP>4</SP>I<SB>13/2</SB>in the fiber 13. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fiber laser that generates a laser beam by exciting a fiber having a core added with rare earth element ions by a laser diode (semiconductor laser).

  The present invention also relates to a fiber amplifier that excites a fiber having a core added with rare earth element ions with a laser diode to generate fluorescence, and amplifies light incident on the fiber by the fluorescence.

For example, as shown in IEICE Technical Report, LQE95-30 (1995) p.30 and Optics communications 86 (1991) p.337, a fiber having a fluoride-based core doped with Pr ³⁺ is used as a laser. Fiber lasers that generate laser beams when excited by diodes are known.

Similarly, as shown in the above document, a fiber having a core to which Pr ³⁺ is added is excited by a laser diode to generate fluorescence, and light included in the wavelength region of the fluorescence is incident on the fiber to cause the fluorescence. Fiber amplifiers that amplify by the energy of the are known.

In particular, the latter document describes an Ar laser-excited Pr ³⁺ doped fiber laser, and oscillations of 491 nm, 520 nm, 605 nm, and 635 nm by 476.5 nm excitation have been confirmed.

  By the way, the above-mentioned fiber laser and fiber amplifier can generate or amplify a laser beam in the blue or green region, and thereby constitute a light source for writing a color image on a color photosensitive material. It is also possible.

  However, the Ar laser-excited fiber laser and fiber amplifier require a water cooling means when they are excited with a power of several watts to several tens of watts for writing a color image or the like. Incurs lifetime and low efficiency problems.

In view of the above circumstances, the present applicant can efficiently generate a high-power blue region or a green region laser beam in Japanese Patent Application No. 10-6370 (see Japanese Patent Application Laid-Open No. 11-204862), and can be formed in a small size. A fiber laser with high output and beam quality stability was proposed. This fiber laser is characterized by having a configuration in which a fiber having a core to which the above Pr ³⁺ is added is excited by a GaN-based laser diode.

Also, in the same Japanese Patent Application No. 10-6370, the present applicant can efficiently amplify the laser beam in the blue region and the green region, can be formed in a small size, and has high output and stability of beam quality. I also proposed an amplifier. This fiber amplifier has a configuration in which a fiber having a core to which Pr ³⁺ is added is excited by a GaN-based laser diode, and incident light having a wavelength included in a wavelength region of fluorescence generated by the excitation is amplified.

Further, the applicant of the present application is as follows in Japanese Patent Application No. 11-206817 (see Japanese Patent Application Laid-Open No. 2001-36168) and at least one of Er ³⁺ , Ho ³⁺ , Dy ³⁺ , Eu ³⁺ , Sm ³⁺ , Pm ³⁺ and Nd ^3+. A fiber laser in which a fiber having a core co-doped with Pr ³⁺ is excited by a GaN-based laser diode or a fiber similar to the above is excited by a GaN-based laser diode, and the wavelength region of fluorescence generated by this excitation We proposed a fiber amplifier that amplifies the incident light of the wavelength included in.
Japanese Patent Laid-Open No. 11-204862

  The present invention provides a fiber laser that can oscillate at many other wavelengths using a GaN-based laser diode as an excitation source, such as the fiber lasers disclosed in Japanese Patent Application Laid-Open Nos. 11-204862 and 2001-36168. For the purpose.

  Furthermore, the present invention can amplify light of many other wavelengths using a GaN-based laser diode as an excitation source, such as the fiber amplifiers disclosed in Japanese Patent Application Laid-Open Nos. 11-204862 and 2001-36168. An object is to provide a fiber amplifier.

In one fiber laser according to the present invention, a fiber having a core doped with Ho ³⁺ is excited by a GaN-based laser diode, and a transition of ⁵ S ₂ → ⁵ I ₇ or ⁵ S ₂ → ⁵ I _{8 in} the fiber is performed. It has a configuration for generating a laser beam. More specifically, this fiber laser generates a laser beam having a wavelength of 740 to 760 nm by a transition of ⁵ S ₂ → ⁵ I ₇ , or a wavelength of 540 to 560 nm by a transition of ⁵ S ₂ → ⁵ I _8. It is possible to adopt a configuration for generating a laser beam.

The excitation wavelength of the fiber having the core to which the Ho ³⁺ is added is 420 nm. And as this fiber, what added only Ho3 ⁺ to the core as a rare earth element ion can be used conveniently.

In another fiber laser according to the present invention, a fiber having a core doped with Sm ³⁺ is excited by a GaN-based laser diode, and ⁴ G _5/2 → ⁶ H _5/2 , ⁴ G _{5/2 in the} fiber is excited. → ⁶ H _7/2, or those having a structure for generating a laser beam by a transition ⁴ F _3/2 → ⁶ H _11/2. This fiber laser, more ^{particularly,} 4 _{G 5/2} → ⁶ or to wavelength generates a laser beam of 556~576nm by a transition H _5/2 or ⁴ G _5/2 → ⁶ H _7/2, A laser beam having a wavelength of 605 to 625 nm can be generated by the transition of the above, and a laser beam having a wavelength of 640 to 660 nm can be generated by the transition of ⁴ F _3/2 → ⁶ H _11/2 .

The excitation wavelength of the fiber having the core to which Sm ³⁺ is added is 404 nm. And as this fiber, what added only Sm3 ⁺ to the core as a rare earth element ion can be used conveniently.

Further, another fiber laser according to the present invention has a configuration in which a fiber having a core doped with Eu ³⁺ is excited by a GaN-based laser diode and a laser beam is generated by a transition of ⁵ D ₀ → ⁷ F _{2 in} the fiber. It is what has. More specifically, this fiber laser is ⁵ D ₀ → ⁷ F ₂ The laser beam having a wavelength of 579 to 599 nm can be generated by this transition.

The excitation wavelength of the fiber having the core to which Eu ³⁺ is added is 394 nm. And as this fiber, what added only Eu3 ⁺ to the core as a rare earth element ion can be used conveniently.

Further, according to another fiber laser of the present invention, a fiber having a core doped with Dy ³⁺ is excited by a GaN-based laser diode, and ⁴ F _9/2 → ⁶ H _13/2 or ⁴ F _{9 / in the} fiber is excited. the transition ₂ → ⁶ H _11/2 and has a structure for generating a laser beam. More specifically, this fiber laser generates a laser beam having a wavelength of 562 to 582 nm by a transition of ⁴ F _9/2 → ⁶ H _13/2 , or ⁴ F _9/2 → ⁶ H _11/2. The laser beam having a wavelength of 654 to 674 nm can be generated by the transition.

The excitation wavelength of the fiber having the core to which Dy ³⁺ is added is 390 nm. And as this fiber, what added only Dy3 ⁺ to the core as a rare earth element ion can be used conveniently.

Further, according to another fiber laser of the present invention, a fiber having a core doped with Er ³⁺ is excited by a GaN-based laser diode, and ⁴ S _3/2 → ⁴ I _15/2 or ² H _{9 / in the} fiber is excited. _The laser beam is generated by the transition of ₂ → ⁴ I _13/2 . More specifically, this fiber laser generates a laser beam having a wavelength of 530 to 550 nm by a transition of ⁴ S _3/2 → ⁴ I _15/2 , or ² H _9/2 → ⁴ I _13/2 . A structure in which a laser beam having a wavelength of 544 to 564 nm is generated by the transition can be employed.

The excitation wavelength of the fiber having the core added with Er ³⁺ is set to 406 nm or 380 nm. And as this fiber, what added only Er3 ⁺ to the core as a rare earth element ion can be used conveniently.

Further, another fiber laser according to the present invention has a configuration in which a fiber having a core doped with Tb ³⁺ is excited by a GaN-based laser diode and a laser beam is generated by a transition of ⁵ D ₄ → ⁷ F _{5 in} the fiber. It is what has. More specifically, this fiber laser can take a configuration in which a laser beam having a wavelength of 530 to 550 nm is generated by a transition of ⁵ D ₄ → ⁷ F ₅ .

The excitation wavelength of the fiber having the core to which Tb ³⁺ is added is 380 nm. And as this fiber, what added only Tb3 ⁺ to the core as a rare earth element ion can be used conveniently.

  On the other hand, in each fiber laser having the above-described configuration, a GaN-based laser diode as an excitation light source can be used more specifically, for example, having an active layer made of InGaN, InGaNAs, or GaNAs.

On the other hand, in one fiber amplifier according to the present invention, a fiber having a core doped with Ho ³⁺ is excited by a GaN-based laser diode, and ⁵ S ₂ → ⁵ I ₇ or ⁵ S ₂ → ⁵ I _{8 in} the fiber is excited. It has a configuration for amplifying incident light having a wavelength included in a wavelength region of fluorescence generated by transition. More specifically, this fiber amplifier generates fluorescence in a wavelength region of 740 to 760 nm by a transition of ⁵ S ₂ → ⁵ I ₇ to amplify incident light having a wavelength included in this region, or ⁵ S It is possible to adopt a configuration in which fluorescence in the wavelength region of 540 to 560 nm is generated by the transition of ₂ → ⁵ I ₈ and incident light having a wavelength included in this region is amplified.

The excitation wavelength of the fiber having the core to which the Ho ³⁺ is added is 420 nm. And as this fiber, what added only Ho3 ⁺ to the core as a rare earth element ion can be used conveniently.

In another fiber amplifier according to the present invention, a fiber having a core added with Sm ³⁺ is excited by a GaN-based laser diode, and ⁴ G _5/2 → ⁶ H _5/2 , ⁴ G _{5/2 in the} fiber is excited. It has a configuration that amplifies incident light having a wavelength included in a wavelength region of fluorescence generated by a transition of ⁶ H _7/2 or ⁴ F _3/2 → ⁶ H _11/2 . More specifically, this fiber amplifier generates fluorescence in a wavelength region of 556 to 576 nm by a transition of ⁴ G _5/2 → ⁶ H _5/2 , and amplifies incident light having a wavelength included in this region. Or ⁴ G _5/2 → ⁶ H _7/2 to generate fluorescence in the wavelength region of 605 to 625 nm and amplify the incident light having a wavelength included in this region, or ⁴ F _3/2 → It is possible to adopt a configuration in which fluorescence in the wavelength region of 640 to 660 nm is generated by the transition of ⁶ H _11/2 and incident light having a wavelength included in this region is amplified.

The excitation wavelength of the fiber having the core to which Sm ³⁺ is added is 404 nm. And as this fiber, what added only Sm3 ⁺ to the core as a rare earth element ion can be used conveniently.

In addition, another fiber amplifier according to the present invention excites a fiber having a core doped with Eu ³⁺ by a GaN-based laser diode, and in a wavelength region of fluorescence generated by a transition of ⁵ D ₀ → ⁷ F _{2 in} the fiber. It has a configuration for amplifying incident light having an included wavelength. This fiber amplifier is more specifically ⁵ D ₀ → ⁷ F ₂ It is possible to adopt a configuration in which fluorescence in the wavelength region of 579 to 599 nm is generated by the transition of and the incident light having the wavelength included in this region is amplified.

The excitation wavelength of the fiber having the core to which Eu ³⁺ is added is 394 nm. And as this fiber, what added only Eu3 ⁺ to the core as a rare earth element ion can be used conveniently.

Furthermore, another fiber amplifier according to the present invention excites a fiber having a core doped with Dy ³⁺ by a GaN-based laser diode, and ⁴ F _9/2 → ⁶ H _13/2 or ⁴ F _{9 / in the} fiber. which is a circuit configuration to amplify the incident light having a wavelength included in the fluorescence wavelength region generated by a transition ₂ → ⁶ H _11/2. More specifically, this fiber amplifier generates fluorescence in a wavelength region of 562 to 582 nm by a transition of ⁴ F _9/2 → ⁶ H _13/2 , and amplifies incident light having a wavelength included in this region. Alternatively, it is possible to generate fluorescence in a wavelength region of 654 to 674 nm by a transition of ⁴ F _9/2 → ⁶ H _11/2 and amplify incident light having a wavelength included in this region.

The excitation wavelength of the fiber having the core to which Dy ³⁺ is added is 390 nm. And as this fiber, what added only Dy3 ⁺ to the core as a rare earth element ion can be used conveniently.

Furthermore, another fiber amplifier according to the present invention excites a fiber having a core doped with Er ³⁺ by a GaN-based laser diode, and ⁴ S _3/2 → ⁴ I _15/2 or ² H _{9 / in the} fiber. _It has a configuration for amplifying incident light having a wavelength included in a wavelength region of fluorescence generated by a transition of ₂ → ⁴ I _13/2 . More specifically, this fiber amplifier generates fluorescence in a wavelength region of 530 to 550 nm by a transition of ⁴ S _3/2 → ⁴ I _15/2 , and amplifies incident light having a wavelength included in this region. Alternatively, it is possible to generate fluorescence in a wavelength region of 544 to 564 nm by transition of ² H _9/2 → ⁴ I _13/2 and amplify incident light having a wavelength included in this region.

The excitation wavelength of the fiber having the core added with Er ³⁺ is set to 406 nm or 380 nm. And as this fiber, what added only Er3 ⁺ to the core as a rare earth element ion can be used conveniently.

Further, another fiber amplifier according to the present invention excites a fiber having a core doped with Tb ³⁺ by a GaN-based laser diode, and in a wavelength region of fluorescence generated by a transition of ⁵ D ₄ → ⁷ F _{5 in} the fiber. It has a configuration for amplifying incident light having an included wavelength. The fiber amplifier, more specifically, ⁵ D ₄ → ⁷ by generating fluorescence in the wavelength range of 530~550nm by a transition F _5, to take a configuration to amplify the incident light having a wavelength included in the region Can do.

The excitation wavelength of the fiber having the core to which Tb ³⁺ is added is 380 nm. And as this fiber, what added only Tb3 ⁺ to the core as a rare earth element ion can be used conveniently.

  On the other hand, in each fiber amplifier having the above-described configuration, more specifically, a GaN-based laser diode as an excitation light source may be one having an active layer made of, for example, InGaN, InGaNAs, or GaNAs.

Ho ³⁺ , Sm ³⁺ , Eu ³⁺ , Dy ³⁺ , Er ³⁺ and Tb ³⁺ have an absorption band at a wavelength of 380 to 420 nm and can be excited by a GaN-based laser diode. The wavelength 380 to 430 nm is a wavelength band in which the GaN laser diode is relatively easy to oscillate, and the wavelength 400 to 410 nm is a wavelength band in which the maximum output of the currently provided GaN laser diode can be obtained. Excitation of Ho ³⁺ , Sm ³⁺ , Eu ³⁺ , Dy ³⁺ , Er ^3+, and Tb ³⁺ with a GaN-based laser diode makes it possible to secure a large amount of absorption of excitation light, thereby improving efficiency and output. Achieved.

And as mentioned above, since the wavelength band of fluorescence by these Ho ³⁺ , Sm ³⁺ , Eu ³⁺ , Dy ³⁺ , Er ³⁺ and Tb ³⁺ is in a wide range, a fiber laser that oscillates at an unprecedented wavelength. Can be obtained.

  On the other hand, the GaN-based laser diode has a thermal conductivity coefficient of 130 W / m ° C., which is extremely large compared to 4 W / m ° C. of the ZnMgSSe-based laser diode. In addition, since the transition mobility is very small as compared with the ZnMgSSe laser diode, the COD (catastrophic optical damage) is very high, and a long life and high output are easily obtained. By using the GaN-based laser diode that easily obtains a long life and high output as an excitation light source, the fiber laser of the present invention can generate a laser beam with a long life and a high output.

  In addition, as a GaN-based laser diode that is an excitation light source, a single longitudinal or transverse mode type can be used, and one or a plurality of high output types such as a broad area type, a phased array type, or a MOPA type can be used. Can be used individually. By doing so, the fiber laser of the present invention can obtain further high output, for example, high output of W (watt) class.

  All the effects described above can be obtained similarly in the fiber amplifier of the present invention. Therefore, according to the fiber amplifier of the present invention, it is possible to strongly amplify light having a wide range of wavelengths.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. First, first to sixth embodiments configured as fiber lasers will be described.

<First Embodiment>
FIG. 1 shows a fiber laser according to a first embodiment of the present invention. This fiber laser includes a laser diode 11 that emits a laser beam 10 as excitation light, a condenser lens 12 that condenses the laser beam 10 that is diverging light, and a fiber 13 that has a core doped with Ho ^3+. .

  As the laser diode 11, a broad area type GaN laser diode having an oscillation wavelength of 420 nm is used.

As shown in the cross-sectional shape of FIG. 2, the fiber 13 has a core 20 having a circular cross section, a first clad 21 having a substantially rectangular cross section disposed on the outside thereof, and a second section having a circular cross section disposed on the outside thereof. It consists of a clad 22. The core 20 is made of Zr fluoride glass doped with, for example, 1 at% of Ho ³⁺ , such as ZBLANP (ZrF ₄ —BaF ₂ —LaF ₃ —AlF ₃ —AlF ₃ —NaF—PbF ₂ ), and the first cladding 21 is an example. ZBLAN (ZrF ₄ —BaF ₂ —LaF ₃ —AlF ₃ —NaF), and the second cladding 22 is made of a polymer as an example.

Incidentally core 20 is not limited to the ZBLANP, and ZBLAN, an In / Ga system fluorides glass, e.g. IGPZCL i.e. _{(InF 3 -GaF 3 -LaF 3)} - formed with a (PbF ₂ -ZnF ₂₎ -CdF like May be.

  The laser beam 10 having a wavelength of 420 nm collected by the condenser lens 12 is input to the first cladding 21 of the fiber 13 and propagates there in a waveguide mode. That is, the first cladding 21 acts as a core for the laser beam 10 that is excitation light.

The laser beam 10 also passes through the portion of the core 20 while propagating in this way. In the core 20, Ho ³⁺ is excited by the incident laser beam 10, and fluorescence having a wavelength of 550 nm is generated by the transition of ⁵ S ₂ → ⁵ I ₈ . This fluorescence propagates through the core 20 in a guided mode.

In addition, in the core 20 made of ZBLANP, fluorescence having a wavelength of 750 nm or the like due to the transition of ⁵ S ₂ → ⁵ I ₇ can be generated. Therefore, the incident end face 13a of the fiber 13 is coated with a characteristic such that it is HR (high reflection) with respect to a wavelength of 550 nm, other fluorescence such as a wavelength of 750 nm, and AR (non-reflection) with respect to an excitation wavelength of 420 nm. A coating that transmits 1% of light having a wavelength of 550 nm is applied to the emission end face 13 b of the fiber 13.

  Thereby, the fluorescence having the wavelength of 550 nm resonates between both end faces 13a and 13b of the fiber 13 to cause laser oscillation. Thus, a green laser beam 15 having a wavelength of 550 nm is generated, and this laser beam 15 is emitted forward from the emission end face 13 b of the fiber 13.

  In this example, the laser beam 15 propagates in a single mode in the core 20, while the laser beam 10, which is excitation light, propagates in a multimode in the first cladding 21. Accordingly, it is possible to input the laser beam 10 to the fiber 13 with high coupling efficiency by applying the high output broad area type laser diode 11 as an excitation light source.

  Further, since the cross-sectional shape of the first cladding 21 is substantially rectangular, the probability that the laser beam 10 follows an irregular reflection path in the cladding cross-section and is incident on the core 20 is increased.

  In addition, since the wavelength of 420 nm is in a wavelength band where a large output of the GaN-based laser diode 11 can be obtained, the absorption amount of the laser beam 10 with a wavelength of 420 nm in the core 20 increases, and high efficiency and high output are achieved. The Specifically, in the present embodiment, when the length of the fiber 13 is 1 m, the green laser beam 15 having an output of 150 mW can be obtained using the laser diode 11 having an output of 300 mW.

When the fiber 13 having the core 20 doped with Ho ³⁺ is used, fluorescence having a wavelength of 750 nm can also be generated due to the transition of ⁵ S ₂ → ⁵ I ₇ described above, so that both end faces 13 a and 13 b of the fiber 13 can be generated. Depending on the setting of the coating to be applied, it is possible to oscillate a laser beam having a wavelength of 750 nm.

<Second Embodiment>
The fiber laser according to the second embodiment has basically the same configuration as that of the fiber laser shown in FIG. 1, and will be described below using the numbers in FIG. The same applies to the third to sixth embodiments).

  This fiber laser is different from the fiber laser shown in FIG. 1 in that the rare earth element ions doped in the core 20 of the fiber 13 and the coating applied to both end faces 13a and 13b of the fiber 13 are different.

That is, in the present embodiment, the core 20 of the fiber 13 is doped with 1 at% of Sm ³⁺ . Further, in order to generate a laser beam having a wavelength of 566 nm using the transition of ⁴ G _5/2 → ⁶ H _5/2 in the core 20, the incident end face 13 a of the fiber 13 has an HR (high reflection) with respect to the wavelength of 566 nm. ) With other ⁴ G _5/2 → ⁶ H _7/2 transition and 650 nm wavelength fluorescence due to ⁴ F _3/2 → ⁶ H _11/2 transition, and excitation wavelength 404 nm A coating having a characteristic of AR (non-reflective) is applied, and a coating that transmits 1% of light having a wavelength of 566 nm is applied to the emission end face 13 b of the fiber 13. Here, the laser diode 11 having an oscillation wavelength of 404 nm is used.

  In this configuration, when the length of the fiber 13 is 1 m, the laser beam 15 with an output of 110 mW and a wavelength of 566 nm can be obtained using the GaN-based laser diode 11 with an output of 200 mW.

In addition, when using the fiber 13 having the core 20 doped with Sm ³⁺ , the above-mentioned ⁴ G _5/2 → ⁶ H _7/2 transition of 615 nm wavelength fluorescence, ⁴ F _3/2 → ⁶ H ₁₁ Fluorescence with a wavelength of 650 nm due to the _{/ 2} transition can also be generated, so it is possible to oscillate a laser beam with a wavelength of 615 nm or a laser beam with a wavelength of 650 nm, depending on the setting of the coating applied to both end faces 13a and 13b of the fiber .

<Third Embodiment>
Compared with the fiber laser shown in FIG. 1, the fiber laser according to the third embodiment also has a rare earth element ion doped in the core 20 of the fiber 13 and a coat applied to both end faces 13a and 13b of the fiber 13. Is different.

That is, in the present embodiment, the core 20 of the fiber 13 is doped with Eu ³⁺ at 1 at%. In addition, ⁵ D ₀ → ⁷ F ₂ in the core 20 In order to generate a laser beam having a wavelength of 589 nm by the transition of, the incident end face 13a of the fiber 13 is HR (high reflection) with respect to the wavelength of 589 nm, fluorescence due to other transitions, and AR (with respect to the excitation wavelength of 394 nm) A coating having a characteristic of “non-reflective” is applied, and a coating that transmits 1% of light having a wavelength of 589 nm is applied to the emission end face 13 b of the fiber 13. Here, the laser diode 11 having an oscillation wavelength of 394 nm is used.

  In this configuration, when the length of the fiber 13 was 1 m, a laser beam 15 having a wavelength of 589 nm and an output of 40 mW could be obtained using a GaN-based laser diode 11 having an output of 100 mW.

<Fourth embodiment>
Compared with the fiber laser shown in FIG. 1, the fiber laser according to the fourth embodiment also has a rare earth element ion doped in the core 20 of the fiber 13 and a coat applied to both end faces 13a and 13b of the fiber 13. Is different.

That is, in the present embodiment, the core 20 of the fiber 13 is doped with 1 at% of Dy ³⁺ . Further, in order to generate a laser beam having a wavelength of 572 nm using the transition of ⁴ F _9/2 → ⁶ H _13/2 in the core 20, the incident end face 13 a of the fiber 13 has an HR (high) with respect to the wavelength of 572 nm. In other words, the coating of the fiber 13 is coated with a characteristic that becomes AR (non-reflective) with respect to the excitation wavelength of 390 nm, etc., as well as the fluorescence of the wavelength of 664 nm due to the other transition of ⁴ F _9/2 → ⁶ H _11/2 The exit end face 13b is coated with 1% of light having a wavelength of 572 nm. Here, the laser diode 11 having an oscillation wavelength of 390 nm is used.

  In this configuration, when the length of the fiber 13 is 1 m, a laser beam 15 with a wavelength of 572 nm and an output of 50 mW can be obtained using the GaN-based laser diode 11 with an output of 100 mW.

When the fiber 13 having the core 20 doped with Dy ³⁺ is used, fluorescence having a wavelength of 664 nm due to the above-described transition of ⁴ F _9/2 → ⁶ H _11/2 can also be generated. It is also possible to oscillate a laser beam with a wavelength of 664 nm, depending on the setting of the coating applied to 13a and 13b.

<Fifth embodiment>
Compared with the fiber laser shown in FIG. 1, the fiber laser according to the fifth embodiment also has a rare earth element ion doped in the core 20 of the fiber 13 and a coating applied to both end faces 13a and 13b of the fiber 13. Is different.

That is, in the present embodiment, the core 20 of the fiber 13 is doped with Er ³⁺ by 1 at%. Further, in order to generate a laser beam having a wavelength of 554 nm by utilizing the transition of ² H _9/2 → ⁴ I _13/2 in the core 20, the incident end face 13a of the fiber 13 has an HR (high) with respect to the wavelength of 554 nm. In the case of the reflection of the fiber 13, a coating having a characteristic of AR (non-reflective) with respect to the excitation wavelength of 406 nm and the fluorescence of the wavelength of 540 nm due to the other ⁴ S _3/2 → ⁴ I _15/2 transition, etc. The exit end face 13b is coated with 1% of light having a wavelength of 554 nm. Here, the laser diode 11 having an oscillation wavelength of 406 nm is used.

  In this configuration, when the length of the fiber 13 is 1 m, a laser beam 15 with a wavelength of 554 nm and an output of 120 mW can be obtained using the GaN-based laser diode 11 with an output of 200 mW.

When the fiber 13 having the core 20 doped with Er ³⁺ is used, fluorescence having a wavelength of 540 nm due to the above-described transition of ⁴ S _3/2 → ⁴ I _15/2 can also be generated. It is also possible to oscillate a laser beam with a wavelength of 540 nm depending on the setting of the coating applied to 13a and 13b.

Further, when the fiber 13 having the core ³ doped with Er ³⁺ is used, the excitation wavelength can be set to 380 nm in addition to the above-described 406 nm.

<Sixth Embodiment>
Compared with the fiber laser shown in FIG. 1, the fiber laser according to the sixth embodiment also has a rare earth element ion doped in the core 20 of the fiber 13 and a coating applied to both end faces 13a and 13b of the fiber 13. Is different.

That is, in the present embodiment, the core 20 of the fiber 13 is doped with 1 at% of Tb ³⁺ . Further, in order to generate a laser beam having a wavelength of 540 nm by the transition of ⁵ D ₄ → ⁷ F ₅ in the core 20, another transition is performed on the incident end face 13 a of the fiber 13 with HR (high reflection) with respect to the wavelength of 540 nm. A coating having a characteristic of AR (non-reflective) with respect to the fluorescence due to the above and an excitation wavelength of 380 nm is applied, and the output end face 13b of the fiber 13 is applied with a coating that transmits 1% of light having a wavelength of 540 nm. Here, the laser diode 11 having an oscillation wavelength of 380 nm is used.

  In this configuration, when the length of the fiber 13 is 1 m, a laser beam 15 with a wavelength of 540 nm and an output of 30 mW can be obtained using a GaN-based laser diode 11 with an output of 100 mW.

  Next, seventh to twelfth embodiments configured as fiber amplifiers will be described.

<Seventh embodiment>
FIG. 3 shows a fiber amplifier according to a seventh embodiment of the present invention. This fiber amplifier collects a laser diode 11 that emits a laser beam 10 having a wavelength of 420 nm as excitation light, a collimator lens 50 that collimates the laser beam 10 that is divergent light, and a laser beam 10 that has become parallel light. It has a light collecting lens 51 and a fiber 53 having a core doped with Ho ³⁺ .

  A beam splitter 52 is disposed between the collimator lens 50 and the condenser lens 51. An SHG (second harmonic generation) laser 56 that emits a laser beam 55 having a wavelength of 550 nm is disposed below the beam splitter 52 in the drawing. The laser beam 55 is collimated by a collimator lens 57, and the laser beam 55 that has become collimated light is incident on the beam splitter 52.

  The fiber 53 basically has the same configuration as that of the fiber 13 shown in FIG. 2, but its end faces 53a and 53b are coated with a characteristic that becomes AR (non-reflective) with respect to each wavelength described above. Is given.

  On the other hand, the SHG laser 56 makes a laser beam with a wavelength of 1100 nm emitted from a DBR (distributed Bragg reflection type) laser diode as a fundamental wave light source enter an optical waveguide made of a nonlinear optical material having a periodic domain inversion structure. A laser beam 55 having a wavelength of / 2, that is, 550 nm is obtained.

  The laser beam 55 is reflected by the beam splitter 52 and enters the fiber 53 together with the laser beam 10. As described in the first embodiment, the fiber 53 is excited by the laser beam 10 to generate fluorescence having a wavelength of 550 nm. The laser beam 55 is amplified by receiving energy from the fluorescence having the same wavelength, and is emitted forward from the emission end face 53 b of the fiber 53.

  In this embodiment, when the output of the SHG laser 56 is 1 mW, the laser beam 55 with an output of 60 mW can be extracted from the fiber 53.

  It is also possible to modulate the laser beam 55 amplified and extracted from the fiber 53 by adding a modulation function to the DBR laser diode which is the fundamental light source of the SHG laser 56.

In addition, when the fiber 53 having a core doped with Ho ³⁺ is used, fluorescence having a wavelength of 750 nm can also be generated by the above-described transition of ⁵ S ₂ → ⁵ I ₇ , so that it is applied to both end faces 53 a and 53 _{b of} the fiber 53. It is possible to amplify a laser beam with a wavelength of 750 nm depending on the setting of the coat.

<Eighth Embodiment>
The fiber amplifier according to the eighth embodiment has basically the same configuration as that of the fiber amplifier shown in FIG. 3, and will be described below using the numbers in FIG. The same applies to the embodiments 9 to 12).

  This fiber amplifier is different from the fiber amplifier shown in FIG. 3 in that the rare earth element ions doped in the core of the fiber 53 and the coating applied to both end faces 53a and 53b of the fiber 53 are different.

That is, in the present embodiment, the core of the fiber 53 is doped with Sm ³⁺ at 1 at%. In addition, here, both end faces 53a and 53b of the fiber 53 have an AR (non-reflective) characteristic with respect to the fluorescence wavelength 566 nm and excitation wavelength 404 nm generated by the transition of ⁴ G _5/2 → ⁶ H _5/2 in the core. There is a coat. As the laser diode 11, one having an oscillation wavelength of 404 nm is used.

  In this embodiment, when the output of the SHG laser 56 is 1.5 mW, the laser beam 55 with an output of 100 mW can be extracted from the fiber 53.

In addition, when using the fiber 53 having a core doped with Sm ³⁺ , fluorescence of a wavelength of 615 nm due to the above-described transition of ⁴ G _5/2 → ⁶ H _7/2 , or ⁴ F _3/2 → ⁶ H _{11 /} Fluorescence with a wavelength of 650 nm due to the transition of ₂ can also be generated, so that it is possible to amplify a laser beam with a wavelength of 615 nm or a laser beam with a wavelength of 650 nm, depending on the setting of the coating applied to both end faces 53a and 53b of the fiber 53.

<Ninth embodiment>
The fiber amplifier according to the ninth embodiment is also different from the fiber amplifier shown in FIG. 3 in the rare earth element ions doped in the core of the fiber 53 and the coating applied to both end faces 53a and 53b of the fiber 53. Is.

That is, in the present embodiment, the core of the fiber 53 is doped with Eu ³⁺ at 1 at%. In addition, here, both end faces 53a and 53b of the fiber 53 are connected to ⁵ D ₀ → ⁷ F ₂ in the core. A coating having a characteristic of AR (non-reflection) is applied to the fluorescence wavelength 589 nm and the excitation wavelength 394 nm generated by the transition. As the laser diode 11, one having an oscillation wavelength of 394 nm is used.

  In this embodiment, when the output of the SHG laser 56 is 1 mW, the laser beam 55 with an output of 50 mW can be extracted from the fiber 53.

<Tenth Embodiment>
The fiber amplifier according to the tenth embodiment is different from the fiber amplifier shown in FIG. 3 in the rare earth element ions doped in the core of the fiber 53 and the coating applied to both end faces 53a and 53b of the fiber 53. Is.

That is, in the present embodiment, the core of the fiber 53 is doped with Dy ³⁺ by 1 at%. In addition, here, both end faces 53a and 53b of the fiber 53 have an AR (non-reflective) characteristic with respect to the fluorescence wavelength 572 nm and the excitation wavelength 390 nm generated by the transition of ⁴ F _9/2 → ⁶ H _13/2 in the core. There is a coat. As the laser diode 11, one having an oscillation wavelength of 390 nm is used.

  In this embodiment, when the output of the SHG laser 56 is 1.5 mW, the laser beam 55 with an output of 80 mW can be extracted from the fiber 53.

When the fiber 53 having a core doped with Dy ³⁺ is used, fluorescence having a wavelength of 664 nm due to the above-described transition of ⁴ F _9/2 → ⁶ H _11/2 can also be generated. Depending on the setting of the coating applied to 53b, it is possible to amplify a laser beam having a wavelength of 664 nm.

<Eleventh embodiment>
The fiber amplifier according to the eleventh embodiment is also different from the fiber amplifier shown in FIG. 3 in the rare earth element ions doped in the core of the fiber 53 and the coating applied to both end faces 53a and 53b of the fiber 53. Is.

That is, in the present embodiment, the core of the fiber 53 is doped with Er ³⁺ at 1 at%. Further, here, the both end faces 53a and 53b of the fiber 53 become AR (non-reflective) with respect to the fluorescence wavelength 554 nm and the excitation wavelength 406 nm generated by the transition transition of ² H _9/2 → ⁴ I _13/2 in the core. A characteristic coat is applied. As the laser diode 11, one having an oscillation wavelength of 406 nm is used.

  In this embodiment, when the output of the SHG laser 56 is 1 mW, the laser beam 55 with an output of 80 mW can be extracted from the fiber 53.

When the fiber 53 having a core doped with Er ³⁺ is used, fluorescence with a wavelength of 540 nm due to the above-described ⁴ S _3/2 → ⁴ I _15/2 can also be generated, and thus both end faces 53a and 53b of the fiber 53 are generated. It is also possible to amplify a laser beam having a wavelength of 540 nm depending on the setting of the coating applied to the substrate.

In addition, when the fiber 53 having a core doped with Er ³⁺ is used, the excitation wavelength can be set to 380 nm in addition to the above-described 406 nm.

<Twelfth embodiment>
The fiber amplifier according to the twelfth embodiment is also different from the fiber amplifier shown in FIG. 3 in the rare earth element ions doped in the core of the fiber 53 and the coating applied to both end faces 53a and 53b of the fiber 53. Is.

That is, in the present embodiment, the core of the fiber 53 is doped with 1 at% of Tb ³⁺ . The end faces 53a of the fiber 53 in this case, in 53b, coat characteristics as the AR relative fluorescence wavelength 540nm and excitation wavelength 380nm caused by the transition of the _⁵ D ₄ → ⁷ F ⁵ in the core (nonreflective) is performed ing. As the laser diode 11, one having an oscillation wavelength of 380 nm is used.

  In this embodiment, when the output of the SHG laser 56 is 1.5 mW, the laser beam 55 with an output of 70 mW can be extracted from the fiber 53.

  The GaN-based laser diode as an excitation light source is appropriately selected from those in which an active layer is formed from an InGaN-based material, those in which an active layer is formed from an InGaNAs-based material, and those in which an active layer is formed from a GaN-based material. Can be used. In particular, when the absorption band of the fiber core is shifted to the long wavelength side, it is desirable to use an InGaNAs-type or GaNAs-type laser diode that can easily achieve longer wavelength than an InGaN-based laser diode, thereby improving the absorption efficiency. Can be improved.

1 is a schematic side view showing a fiber laser according to a first embodiment of the present invention. Sectional view of the fiber used in the fiber laser of FIG. The schematic side view which shows the fiber amplifier by the 3rd Embodiment of this invention

Explanation of symbols

10 Laser beam (excitation light)
11 InGaN laser diode
12 Condensing lens
13 Fiber
13a, 13b Fiber end face
15 Laser beam
20 cores
21 First cladding
22 Second cladding
50 Collimator lens
51 condenser lens
52 Beam splitter
53 fiber
53a, 53b Fiber end face
55 Laser beam
56 SHG laser
57 Collimator lens

Claims (10)

A fiber having a core doped with Er ³⁺ is excited by a GaN-based laser diode, and a laser beam is _{generated by} a transition of ⁴ S _3/2 → ⁴ I _15/2 or ² H _9/2 → ⁴ I _{13/2 in} the fiber. A fiber laser characterized by having a configuration for generating a laser beam. 2. The fiber laser according to claim 1, wherein a laser beam having a wavelength of 530 to 550 nm is generated by the transition of ⁴ S _3/2 → ⁴ I _15/2 . ^2. The fiber laser according to claim 1, wherein a laser beam having a wavelength of 544 to 564 nm is generated by the transition of ² H _9/2 → ⁴ I _13/2 . The fiber laser according to any one of claims 1 to 3, wherein the fiber is obtained by adding only Er ³⁺ as a rare earth element ion to the core.   The fiber laser according to any one of claims 1 to 4, wherein the GaN-based laser diode has an active layer made of InGaN, InGaNAs, or GaNAs. A fiber having a core doped with Er ³⁺ is excited by a GaN-based laser diode, and fluorescence generated by a transition of ⁴ S _3/2 → ⁴ I _15/2 or ² H _9/2 → ⁴ I _{13/2 in} the fiber. A fiber amplifier having a configuration for amplifying incident light having a wavelength included in the wavelength region of. The fluorescent light in a wavelength region of 530 to 550 nm is generated by the transition of ⁴ S _3/2 → ⁴ I _15/2 , and incident light having a wavelength included in this region is amplified. Fiber amplifier. The fluorescent light in a wavelength region of 544 to 564 nm is generated by the transition of ² H _9/2 → ⁴ I _13/2 , and incident light having a wavelength included in this region is amplified. Fiber amplifier. The fiber amplifier according to any one of claims 6 to 8, wherein the fiber is obtained by adding only Er ³⁺ as a rare earth element ion to the core.   The fiber amplifier according to any one of claims 6 to 9, wherein the GaN-based laser diode has an active layer made of InGaN, InGaNAs, or GaNAs.

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