JP2012209510A - Optical fiber laser light source - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical fiber laser light source that has high output stability.SOLUTION: The optical fiber laser light source includes: an input side filter film (7) disposed on an output side end face of an excitation light waveguide fiber (2) and forming an input side gap (N) to an input side end face of an amplified light waveguide fiber (3), and reflecting a predetermined wavelength band of light and transmitting a predetermined wavelength band of light; an output side half mirror film (8) disposed on an output side end face of the amplified light waveguide fiber (3) and forming an output side gap (S) to an input side end face of an output light waveguide fiber (4), reflecting a predetermined wavelength band of light and transmitting a predetermined wavelength band of light, and constituting a first optical resonator (K1) up to the input side filter film (7); and a fiber Bragg grating (14) disposed in the output light waveguide fiber (4) and constituting a second optical resonator (K2) up to the input side filter film (7). The input side gap (N) and the output side gap (S) have a distance (Ln) and a distance (Ls) of 20 μm or shorter, respectively. This structure provides high output stability.

Description

  The present invention relates to an optical fiber laser light source, and more particularly to an optical fiber laser light source having high output stability.

  Conventionally, there are provided a semiconductor laser, a pumping optical waveguide that guides pumping laser light output from the semiconductor laser, and an amplification medium that outputs spontaneous emission light having a predetermined band excited by pumping laser light output from the pumping optical waveguide. Added optical waveguide, output optical waveguide that guides spontaneous emission light output from the amplification optical waveguide, and wavelength that is provided between the amplification optical waveguide and the output optical waveguide and selectively transmits light in a predetermined band A spatial coupling unit having a selection element, a lens that transmits the spontaneous emission light output from the amplification optical waveguide to the wavelength selection element, an incident-side reflection unit provided between the excitation optical waveguide and the amplification optical waveguide, and a spatial coupling unit And a light source including output side reflection means provided between the output optical waveguides are known (see, for example, Patent Documents 1 and 2).

International Publication WO2006 / 132285 JP 2007-234711 A

In the conventional light source, there is light reflection at the end face of the lens or wavelength selection element in the spatial coupling portion. That is, there are a plurality of light reflection points. For this reason, there is a problem in output stability.
Therefore, an object of the present invention is to provide an optical fiber laser light source having high output stability.

In the first aspect, the present invention provides [a] a pumping light waveguide fiber (2) for guiding pumping light output from the semiconductor pumping laser (1), and [b] output from the pumping light waveguide fiber (2). And amplifying optical waveguide fiber (3) for emitting emitted light of a predetermined wavelength band and guiding the light, and [c] light output from the amplifying optical waveguide fiber (3). An input-side gap is provided between the output optical waveguide fiber (4) to be guided and [d] the output-side end face of the pumping-light waveguide fiber (2) and the input-side end face of the amplification optical waveguide fiber (3). (N) or an input side gap (N) provided on the input side end face of the amplification optical waveguide fiber (3) and between the output side end face of the excitation light waveguide fiber (2) And reflects light of a predetermined wavelength band and transmits light of a predetermined wavelength band. Between the input side filter membrane (7) and [e] the input side end face of the output optical waveguide fiber (4) and the output side end face (S Or an output side air gap (S) provided between the output side end face of the amplified optical waveguide fiber (3) and the input side end face of the output optical waveguide fiber (4), An output-side half mirror film (8) that reflects light of a predetermined wavelength band and transmits light of a predetermined wavelength band and constitutes the first optical resonator (K1) with the input-side filter film (7). And [to] a fiber Bragg grating (14) provided in the output optical waveguide fiber (4) and constituting a second optical resonator (K2) between the input filter film (7) and [G] Distance (Ln) of the input side gap (N) and Distance serial output gap (S) (Ls) to provide an optical fiber laser source (100), characterized in that at 20μm or less.
In the optical fiber laser light source (100) according to the first aspect, the input side gap (N) in the input side filter film (7) and the output side gap (S) in the output side half mirror film (8) are two places. However, the first optical resonator (K1) is formed between the input side filter film (7) and the output side half mirror film (8). Further, the second optical resonator (K2) is formed between the input side filter film (7) and the fiber Bragg grating (14) to form a two-stage composite resonator structure. As a result, the output stability is increased. Furthermore, since the distance (Ln) of the input side gap (N) and the distance (Ls) of the output side gap (S) are 20 μm or less, the resonance wavelength interval is 30 nm or more, and mode hops are less likely to occur. Increases stability.

In a second aspect, the present invention provides the optical fiber laser light source (100) according to the first aspect, wherein the amplification optical waveguide fiber (3) includes a core (3a) to which a rare earth element is added as an amplification medium; An inner cladding (3b) having a lower refractive index than the core (3a) provided outside the core (3a), and an outer having a lower refractive index than the inner cladding (3b) provided outside the inner cladding (3b) An optical fiber laser light source (100) characterized by having a clad (3c) is provided.
In the optical fiber laser light source (100) according to the second aspect, the core (3a) and the inner cladding (3b) guide the pumping light from the semiconductor laser, and the amplification medium added to the core (3a) is the pumping light. It is excited to generate emission light, and the emission light is guided through the core (3a).

In a third aspect, the present invention provides the optical fiber laser light source (100) according to the first or second aspect, wherein the length (L3) of the amplified optical waveguide fiber (3) is in the predetermined wavelength band. Provided is an optical fiber laser light source (100) characterized in that it is adjusted to emit emitted light.
The wavelength band of the emitted light of the amplified optical waveguide fiber (3) changes according to the length (L3) of the amplified optical waveguide fiber (3).
Therefore, in the optical fiber laser light source (100) according to the third aspect, the length (L3) of the amplified optical waveguide fiber (3) is adjusted so that emitted light in a predetermined wavelength band is emitted.

In a fourth aspect, the present invention provides the optical fiber laser light source (100) according to any one of the first to third aspects, wherein the input side filter film (7) has a transmittance of 95 with respect to the excitation light. An optical fiber laser light source (100) having a reflectance of 95% or more with respect to the emitted light is provided.
In the optical fiber laser light source (100) according to the fourth aspect, the excitation light is efficiently input to the amplified optical waveguide fiber (3), and the emitted light generated by the amplified optical waveguide fiber (3) is efficiently reflected. I can do it.

In a fifth aspect, the present invention provides the optical fiber laser light source (100) according to any one of the first to fourth aspects, wherein the output-side half mirror film (8) has a reflectance with respect to the emitted light. An optical fiber laser light source (100) characterized by being 4% to 90% is provided.
The output spectrum of the first optical resonator (K1) changes according to the reflectance of the output-side half mirror film (8).
Therefore, in the optical fiber laser light source (100) according to the fifth aspect, the reflectance of the output-side half mirror film (8) is adjusted between 4% and 90% to obtain output light in a predetermined wavelength band. Like that.

In a sixth aspect, the present invention provides an optical fiber laser light source (100) according to any one of the first to fifth aspects, wherein the core (3a) of the amplified optical waveguide fiber (3) and the output optical waveguide fiber An optical fiber laser light source (100) characterized in that the center axis of the core (4a) of (4) is shifted.
As a property of the optical fiber laser light source, if the power of the semiconductor pump laser (1) is low, the amplified optical waveguide fiber (3) is not pumped (inversion distribution is unstable), and the output becomes unstable. , Noise increases. For example, in a microscope apparatus that performs fluorescence analysis, noise (rms) is required to be about several percent or less, but this requirement cannot be satisfied if the power of the semiconductor excitation laser (1) is low. For this reason, the power of the semiconductor pump laser (1) must be increased. However, if the power of the semiconductor pump laser (1) is increased, the power of the output light also increases, causing problems such as shortening the life of the SHG element to which the output light is input.
Therefore, in the optical fiber laser light source (100) according to the sixth aspect, the center axes of the core (3a) of the amplified optical waveguide fiber (3) and the core (4a) of the output optical waveguide fiber (4) are shifted to output Attenuates the power of light. As a result, the power of the semiconductor pump laser (1) can be increased to stabilize the output, and the power of the output light can be prevented from becoming too strong.

In a seventh aspect, the present invention relates to the optical fiber laser light source (100) according to any one of the first to sixth aspects, wherein the output optical waveguide fiber (4) is cut at one place and is off-axis fused. An optical fiber laser light source (100) is provided.
As a property of the optical fiber laser light source, if the power of the semiconductor pump laser (1) is low, the amplified optical waveguide fiber (3) is not pumped (inversion distribution is unstable), and the output becomes unstable. , Noise increases. For example, in a microscope apparatus that performs fluorescence analysis, noise (rms) is required to be about 2% or less, but this requirement cannot be satisfied if the power of the semiconductor excitation laser (1) is low. For this reason, the power of the semiconductor pump laser (1) must be increased. However, if the power of the semiconductor pump laser (1) is increased, the power of the output light also increases, causing problems such as shortening the life of the SHG element to which the output light is input.
Therefore, in the optical fiber laser light source (100) according to the seventh aspect, the power of the output light is attenuated by cutting at one point of the output optical waveguide fiber (4) and fusing it while shifting its axis. As a result, the power of the semiconductor pump laser (1) can be increased to stabilize the output, and the power of the output light can be prevented from becoming too strong.

In an eighth aspect, the present invention relates to an optical fiber laser light source (100) according to any one of the first to seventh aspects, wherein the output side half mirror film (8) and the fiber Bragg grating (14) are arranged. And an optical fiber laser light source (100), characterized in that it comprises polarization separation means (13).
In the optical fiber laser light source (100) according to the eighth aspect, linearly polarized wave output can be performed by installing the polarization separating means (13) in the second optical resonator (K2). It is suitable as a light source for an SHG element that converts the wavelength of only the component.

In a ninth aspect, the present invention provides the optical fiber laser light source (100) according to the eighth aspect, wherein the polarization separation means (13) is a polarization maintaining optical fiber fusion coupler type polarization separation element (13). An optical fiber laser light source (100) is provided.
In the optical fiber laser light source (100) according to the ninth aspect, since the polarization maintaining optical fiber fusion coupler type polarization separation element (13) is used, the space is smaller than the polarization separation means that sandwiches the polarizer. There is no propagation part, and it is not affected by the noise increase of the output light caused by the internal reflection point.

In a tenth aspect, the present invention provides the optical fiber laser light source (100) according to any one of the first to ninth aspects, wherein the amplified optical waveguide fiber (3) and the output optical waveguide fiber (4) are: An optical fiber laser light source (100) is provided that is a polarization maintaining optical fiber.
The optical fiber laser light source (100) according to the tenth aspect is suitable as a light source for an SHG element that converts the wavelength of only the linearly polarized wave component because it can perform linearly polarized wave output.

In an eleventh aspect, the present invention provides the optical fiber laser light source (100) according to the tenth aspect, wherein the polarization axes of the amplified optical waveguide fiber (3) and the output optical waveguide fiber (4) are 0 °. Alternatively, an optical fiber laser light source (100) characterized by being 90 ° is provided.
If the polarization axes of the amplification optical waveguide fiber (3) and the output optical waveguide fiber (4) are not 0 ° or 90 °, the linear polarization of the light reciprocating in the second optical resonator (K2) cannot be maintained. .
Therefore, in the optical fiber laser light source (100) according to the eleventh aspect, the polarization axes of the amplified optical waveguide fiber (3) and the output optical waveguide fiber (4) are adjusted to 0 ° or 90 °.

In a twelfth aspect, the present invention provides an optical fiber laser light source (100) according to any one of the first to eleventh aspects, wherein an output side end face of the pumping optical waveguide fiber (2) or the amplified optical waveguide fiber ( An optical fiber laser light source (100) is provided, wherein an antireflection film (17) is provided on the input side end face of (3) where the input side filter film (7) is not provided. .
An antireflection film (17) is provided on the surface of the output side end face of the pumping optical waveguide fiber (2) or the input side end face of the amplification optical waveguide fiber (3) where the input side filter film (7) is not provided. If not, mode hops occur due to reflection on the surface, and the oscillation wavelength may fluctuate.
In the optical fiber laser light source (100) according to the twelfth aspect, since the antireflection film (17) is provided, mode hops do not occur and fluctuations in the oscillation wavelength can be suppressed.

In a thirteenth aspect, the present invention provides an optical fiber laser light source (100) according to any one of the first to twelfth aspects, wherein an output side end face of the amplified optical waveguide fiber (3) or the output optical waveguide fiber ( An optical fiber laser light source (100) is provided, wherein an antireflection film (18) is provided on the input side end face of 4) on which the output side half mirror film (8) is not provided. To do.
An antireflection film (18) is provided on the output side end face of the amplified optical waveguide fiber (3) or the input side end face of the output optical waveguide fiber (4) on which the output side half mirror film (8) is not provided. If not provided, mode hops may occur due to reflection on the surface, and the oscillation wavelength may vary.
In the optical fiber laser light source (100) according to the thirteenth aspect, since the antireflection film (18) is provided, mode hops do not occur and fluctuations in the oscillation wavelength can be suppressed.

In a fourteenth aspect, the present invention provides the optical fiber laser light source (100) according to any one of the first to thirteenth aspects, wherein the output side end of the pumping optical waveguide fiber (2) has a ferrule (31). The input side end of the amplified optical waveguide fiber (3) is fixed to the ferrule (32), and the output side end of the amplified optical waveguide fiber (3) is fixed to the ferrule (33). An optical fiber laser light source (100) is provided, wherein an input side end of the output optical waveguide fiber (4) is fixed to a ferrule (34).
In the optical fiber laser light source (100) according to the fourteenth aspect, the ferrule (31) facilitates handling of the output side end of the pumping light waveguide fiber (2). Further, the ferrule (32) facilitates handling of the input side end of the amplified optical waveguide fiber (3). Further, the ferrule (33) facilitates handling of the output side end of the amplified optical waveguide fiber (3). Further, the ferrule (34) facilitates handling of the input side end of the output optical waveguide fiber (4).

In a fifteenth aspect, the present invention provides the optical fiber laser light source (100) according to the fourteenth aspect, wherein the ferrules (31 to 34) are made of ceramics or transparent glass. 100).
In the case of ceramics, the optical fiber laser light source (100) according to the fifteenth aspect has an advantage that zirconia used in an optical connector can be used as it is. In the case of transparent glass, since ultraviolet rays can be transmitted well, there is an advantage that an ultraviolet curable adhesive can be used for joining the fibers (2, 3, 4) and the ferrules (31, 32, 33, 34).

According to a sixteenth aspect, the present invention relates to the optical fiber laser light source (100) according to the fourteenth or fifteenth aspect, wherein the amplification optical waveguide fiber (3) is a core doped with a rare earth element as an amplification medium ( 3a), an inner cladding (3b) having a refractive index lower than that of the core (3a) provided outside the core (3a), and an inner cladding (3b) provided outside the inner cladding (3b). When the outer cladding (3c) having a low rate is included, the outer cladding (3c) in the portion inserted into the ferrule (33) at the output side end of the amplified optical waveguide fiber (3) is removed, and the inner cladding The gap between the insertion hole of the ferrule (33) and the inner cladding (3b) is filled and hardened with an adhesive (35) having a refractive index equal to or higher than that of the cladding (3b). Providing an optical fiber laser source (100).
In the optical fiber laser light source (100) according to the sixteenth aspect, the outer cladding (3c) at the output side end of the amplified optical waveguide fiber (3) is removed, and the refraction is equal to or higher than that of the inner cladding (3b). In order to fill and harden the space between the insertion hole of the ferrule (33) and the inner cladding (3b) with an adhesive (35) with a high rate, the residual excitation light propagating through the inner cladding (3b) can be efficiently leaked to the outside. I can do it. Therefore, it is possible to suppress heat from being accumulated by the residual excitation light at the junction between the output side end of the amplified optical waveguide fiber (3) and the ferrule (33). In addition, when heat accumulates, deterioration of a junction part will be accelerated. In addition, the joining state varies due to thermal expansion, and the output characteristics deteriorate.

In a seventeenth aspect, the present invention relates to an input side end of the output optical waveguide fiber (4) when the ferrule (34) is made of transparent glass in the optical fiber laser light source (100) according to the sixteenth aspect. An optical fiber laser light source (100) is provided in which a fiber insertion port of the ferrule (34) for inserting a portion is processed into a conical shape and is plated with gold or silver (36).
In the optical fiber laser light source (100) according to the seventeenth aspect, residual pumping light leaking out from the amplification optical waveguide fiber (3) (and light lost when the off-axis connection according to the sixth aspect is performed) Can be reflected and scattered to the outside by gold plating or silver plating (36). This prevents the residual excitation light (and the light lost when the off-axis connection according to the sixth aspect is performed) from entering the adhesive reservoir portion of the ferrule (34) and generating heat. Can improve the performance.

In an eighteenth aspect, the present invention provides the optical fiber laser light source (100) according to any one of the fourteenth to seventeenth aspects, wherein an output side end face of the ferrule (31) and an input side of the ferrule (32) An annular groove (27) is provided in at least one of the end faces, and an adhesive (37) is provided between the output side end face of the ferrule (31) and the input end face of the ferrule (32) outside the groove (27). And an annular groove (28) is provided in at least one of the output side end face of the ferrule (33) and the input side end face of the ferrule (34), and the output side end face of the ferrule (33) and the ferrule ( 34) An optical fiber laser light source (100) characterized in that a portion of the input side end face outside the groove (28) is bonded with an adhesive (38).
In the optical fiber laser light source (100) according to the eighteenth aspect, the groove (27) can prevent the adhesive (37) from entering the optical path. Further, the groove (28) can prevent the adhesive (38) from entering the optical path.

In a nineteenth aspect, the present invention provides the optical fiber laser light source (100) according to any one of the fourteenth to eighteenth aspects, wherein the ferrule (31) and the ferrule (32) are cylindrical with the same diameter. Both are held by a sleeve (41), the ferrule (33) and the ferrule (34) are cylindrical with the same diameter, and both are held by a sleeve (42). )I will provide a.
In the optical fiber laser light source (100) according to the nineteenth aspect, the coupling portion between the output side end portion of the pumping light waveguide fiber (2) and the amplification light waveguide fiber (3) can be protected by the sleeve (41). Further, the coupling portion between the output side end portion of the amplified optical waveguide fiber (3) and the output optical waveguide fiber (4) can be protected by the sleeve (42). If a sleeve having a large thermal conductivity and heat capacity is used, heat due to coupling loss and heat due to leakage of residual excitation light can be efficiently radiated from the coupling portion.

In a twentieth aspect, the present invention provides an optical fiber laser light source (100) according to any one of the first to nineteenth aspects, wherein the amplified optical waveguide fiber (3) and the output optical waveguide fiber (4) Provided is an optical fiber laser light source (100) characterized in that a temperature control means (10) is provided at a coupling portion.
In the optical fiber laser light source (100) according to the twentieth aspect, heat due to coupling loss and heat due to leakage of residual excitation light can be absorbed by the temperature adjusting means (10). Further, the distance (Ls) of the output side gap (S) can be controlled by controlling the temperature of the coupling portion. Note that when the distance (Ls) of the output-side gap (S) changes, the output characteristics (wavelength, power, noise) change.

In a twenty-first aspect, the present invention is the optical fiber laser light source (100) according to any one of the first to twentieth aspects, wherein temperature control means (50) for the amplified optical waveguide fiber (3) is provided. An optical fiber laser light source (100) is provided.
In the optical fiber laser light source (100) according to the twenty-first aspect, the oscillation wavelength can be controlled by controlling the temperature of the amplified optical waveguide fiber (3). That is, the oscillation wavelength can be shifted to the longer wavelength side by heating the amplified optical waveguide fiber (3), and the oscillation wavelength can be shifted to the shorter wavelength side by cooling the amplified optical waveguide fiber (3).

  According to the optical fiber laser light source (100) of the present invention, output stability can be improved.

1 is an explanatory diagram illustrating a configuration of an optical fiber laser light source 100 according to a first embodiment. 1 is an explanatory diagram showing a configuration of an optical fiber laser light source 200 including an optical fiber laser light source 100. FIG. FIG. 3 is a cross-sectional view of the amplified optical waveguide fiber 3. 6 is a chart showing parameters of an amplified optical waveguide fiber 3; 3 is a cross-sectional view showing a coupling portion between a pumping light waveguide fiber 2 and an amplification light waveguide fiber 3. FIG. 3 is a cross-sectional view showing a coupling portion between an amplified optical waveguide fiber 3 and an output optical waveguide fiber 4. FIG. It is explanatory drawing which shows the angle of the polarization axes of the amplification optical waveguide fiber 3 and the output optical waveguide fiber 4. FIG. 6 is a reflectance-wavelength characteristic diagram of the output-side half mirror film 8. FIG. 2 is an output spectrum diagram of the optical fiber laser light source 100. FIG. It is explanatory drawing of the structure which used the output side edge part of the amplification optical waveguide fiber 3 as a non-reflective terminal. FIG. 5 is an output spectrum diagram of the amplified optical waveguide fiber 3 in a configuration in which the output side end of the amplified optical waveguide fiber 3 is a non-reflective terminal 8 ′. 4 is an explanatory diagram of a configuration in which an output-side half mirror film 8 is provided at an output-side end portion of an amplification optical waveguide fiber 3. FIG. FIG. 6 is an output spectrum diagram of the amplified optical waveguide fiber 3 in a configuration in which an output-side half mirror film 8 is provided at the output side end of the amplified optical waveguide fiber 3. It is a transmittance-wavelength characteristic diagram of a parallel plate resonator (Fabry-Perot etalon filter) when the distance Ln of the input side gap N and the distance Ls of the output side gap S are 10 μm, 20 μm, and 30 μm. It is an output spectrum figure when length L3 of the amplification optical waveguide fiber 3 is 15 m and 14 m. It is an output spectrum figure in case the reflectance R of an output side half mirror film | membrane is 50% and 40%. It is an excitation LD electric current-SHG noise characteristic view. It is explanatory drawing which shows the position shift of the central axis of the insertion hole 33a of the ferrule 33, and the insertion hole 34a of the ferrule 34. FIG. It is sectional drawing which shows the part which the output optical waveguide fiber 4 cut | disconnected and it shifted and shifted the axis | shaft.

  Hereinafter, the present invention will be described in more detail with reference to embodiments shown in the drawings. Note that the present invention is not limited thereby.

Example 1
FIG. 1 is an explanatory diagram of a configuration of an optical fiber laser light source 100 according to the first embodiment.
The optical fiber laser light source 100 includes the following components.
[A] pumping optical waveguide fiber 2 which is a multimode optical fiber and guides pumping light output from the semiconductor pumping laser 1;
[B] Amplification optical waveguide fiber 3 which is a polarization-maintaining optical fiber, which inputs the pumping light output from the pumping light waveguide fiber 2 to emit the emission light of a predetermined wavelength band and guides the light;
[C] Polarization-maintaining optical fiber, an output optical waveguide fiber 4 for guiding the light output from the amplified optical waveguide fiber 3,
[D] An input-side air gap N is formed between the input-side end surface of the amplifying optical waveguide fiber 3 and provided on the output-side end surface of the pumping light waveguide fiber 2, and reflects light in a predetermined wavelength band and has a predetermined wavelength. An input side filter film 7 that transmits light in a band;
[E] An output side air gap S is formed between the output side end face of the amplified optical waveguide fiber 3 and the input side end face of the output optical waveguide fiber 4 to reflect light in a predetermined wavelength band and to have a predetermined wavelength. An output-side half mirror film 8 that transmits light in a band and constitutes the first optical resonator K1 with the input-side filter film 7,
[F] A fiber Bragg grating 14 provided in the output optical waveguide fiber 4 and constituting the second optical resonator K2 with the input-side filter film 7,
[G] The distance Ln of the input side gap N and the distance Ls of the output side gap S are 20 μm or less.
[H] Polarization-maintaining optical fiber fusion coupler type polarization separation element 13 provided in the middle of the output optical waveguide fiber 4 before the fiber Bragg grating 14;
[Li] a temperature controller 10 for adjusting the temperature of the coupling portion between the amplified optical waveguide fiber 3 and the output optical waveguide fiber 4;
[Nu] Temperature controller 50 for controlling the temperature of the amplified optical waveguide fiber 3,
[Le] a beam splitter 21 that branches a part of output light output from the output optical waveguide fiber 4;
[W] a light receiving element 22 for receiving the output light branched by the beam splitter 21;
[W] A control unit 23 that monitors the output light by the light receiving element 22 and feedback-controls the semiconductor excitation laser 1.

  Instead of the input side filter film 7 of [D], an input side gap N is formed between the input side end face of the amplification optical waveguide fiber 3 and the output side end face of the pumping optical waveguide fiber 2, An input-side filter film that reflects light in a predetermined wavelength band and transmits light in a predetermined wavelength band may be used.

  Further, instead of the output side half mirror film 8 of [e], an output side gap S is formed between the output side end face of the amplified optical waveguide fiber 3 provided on the input side end face of the output optical waveguide fiber 4, and An output-side half mirror film that reflects light in a predetermined wavelength band and transmits light in a predetermined wavelength band and constitutes the first optical resonator K1 with the input-side filter film may be used.

FIG. 2 is an explanatory diagram of a configuration of an optical fiber laser light source 200 including the optical fiber laser light source 100.
The optical fiber laser light source 200 includes the constituent elements [A] to [N] of the optical fiber laser light source 100 and the following constituent elements.
[F] SHG element 51 for outputting harmonic light of output light output from output optical waveguide fiber 4;
[Y] a beam splitter 21 that branches a part of output light output from the SHG element 51;
[T] A light receiving element 22 for receiving the output light branched by the beam splitter 21,
[L] A control unit 23 that monitors output light by the light receiving element 22 and performs feedback control of the semiconductor excitation laser 1.

FIG. 3 is a cross-sectional view of the amplified optical waveguide fiber 3.
The amplification optical waveguide fiber 3 includes a core 3a to which a rare earth element is added as an amplification medium, an inner cladding (quartz cladding) 3b having a lower refractive index than the core 3a provided outside the core 3a, and an outer side of the inner cladding 3b. This is a double clad Yb fiber having an outer clad (resin clad) 3c having a lower refractive index than the inner clad 3b provided.

FIG. 4 is a chart showing parameters of the amplified optical waveguide fiber 3.
The length L3 of the amplified optical waveguide fiber 3 is, for example, 1 to 15 m.
The rare earth element added as the amplifying medium is, for example, ytterbium ions, and is excited by excitation light having a wavelength of 915 nm to generate emission light having a wavelength band of 1000 nm to 1200 nm.

  The output optical waveguide fiber 4 is a 980PANDA fiber.

FIG. 5 is an enlarged cross-sectional view of a coupling portion between the excitation light waveguide fiber 2 and the amplification light waveguide fiber 3.
A resin coating is removed from the output side end of the excitation light waveguide fiber 2 and the outer peripheral surface of the clad is bonded to the ferrule 31 with, for example, a UV curable resin.
The ferrule 31 is made of ceramics or transparent glass.

The input side filter film 7 inserts the output side end portion of the excitation light waveguide fiber 2 into the ferrule 31, then polishes the output side end surface of the excitation light waveguide fiber 2 together with the ferrule 31, and applies a dielectric multilayer film to the polished surface. Formed and provided.
The input side filter film 7 has a transmittance of 95% or more for the excitation light and a reflectance of 95% or more for the emitted light. For example, the transmittance is 95% or more for a wavelength of 915 nm and the reflectance is 95% or more for a wavelength of 900 nm to 1200 nm.

The input side end of the amplification optical waveguide fiber 3 is inserted into a cylindrical ferrule 32, and the outer peripheral surface is bonded to the ferrule 32 with, for example, a UV curable resin.
The ferrule 32 is made of ceramics or transparent glass.
An annular groove 27 is formed on the input side end face of the ferrule 32.

  After the input side end of the amplified optical waveguide fiber 3 is inserted into the ferrule 32, the input side end surface of the amplified optical waveguide fiber 3 is polished together with the ferrule 32, and the antireflection film 17 is provided inside the groove 27 of the polished surface. . The antireflection film 17 is, for example, an AR coat corresponding to a wavelength of 950 nm to 1150 nm.

The ferrule 31 into which the output side end portion of the excitation light waveguide fiber 2 is inserted is inserted into the sleeve 41 to the middle of the metal sleeve 41.
On the other hand, the ferrule 32 into which the input side end portion of the amplification optical waveguide fiber 3 is inserted is coated with an adhesive 37 on the input side end surface outside the groove 27, inserted into the sleeve 41, and bonded to the ferrule 31.

FIG. 6 is an enlarged cross-sectional view of the coupling portion between the amplified optical waveguide fiber 3 and the output optical waveguide fiber 4.
The outer clad 3 c is removed from the output side end of the amplified optical waveguide fiber 3 and inserted into a cylindrical ferrule 33, and the outer peripheral surface of the inner clad 3 b is bonded to the ferrule 33 with an adhesive 35.
This adhesive 35 is an adhesive having a refractive index equal to or higher than that of the inner clad 3b, and is, for example, a UV curable resin having an adjusted refractive index.
The ferrule 33 is made of ceramics or transparent glass.
An annular groove 28 is formed on the output side end face of the ferrule 33.

  The output-side half mirror film 8 inserts the output-side end portion of the amplified optical waveguide fiber 3 into the ferrule 33, then polishes the output-side end surface of the amplified optical waveguide fiber 3 together with the ferrule 33, and is inside the groove 28 on the polished surface. Is provided.

The input side end of the output optical waveguide fiber 4 is removed from the resin coating, inserted into a cylindrical ferrule 34, and the outer peripheral surface of the clad is bonded to the ferrule 34 with, for example, a UV curable resin.
The ferrule 34 is made of ceramics or transparent glass.
When the ferrule 34 is made of transparent glass, the fiber insertion port of the ferrule 34 into which the input side end portion of the output optical waveguide fiber 4 is inserted is processed into a conical shape.

After the input side end portion of the output optical waveguide fiber 4 is inserted into the ferrule 34, the input side end surface of the output optical waveguide fiber 4 is polished together with the ferrule 34, and the antireflection film 18 is provided on the polished surface.
When the ferrule 34 is made of transparent glass, gold or silver plating 36 is applied to the fiber insertion port processed into a conical shape.

The ferrule 34 into which the input side end of the output optical waveguide fiber 4 is inserted is inserted into the sleeve 42 to the middle of the metal sleeve 42.
On the other hand, the ferrule 33 into which the output side end portion of the amplified optical waveguide fiber 3 is inserted is coated with an adhesive 38 on the input side end surface outside the groove 28, inserted into the sleeve 42, and adhered to the ferrule 34.

  A temperature controller 10 that controls the temperature of the coupling portion between the amplified optical waveguide fiber 3 and the output optical waveguide fiber 4 includes a Peltier element 10a and a thermistor 10b.

  Although not shown, the temperature controller 50 that regulates the temperature of the amplified optical waveguide fiber 3 includes a case that includes the Peltier element and the thermistor and that accommodates the amplified optical waveguide fiber 3.

  As shown in FIG. 7, adjustment is made so that the polarization axes of the amplified optical waveguide fiber 3 and the output optical waveguide fiber 4 are 0 ° or 90 °.

FIG. 8 is a reflectance-wavelength characteristic diagram of the output-side half mirror film 8.
The reflectance Rs of the output-side half mirror film 8 is about the broad wavelength range (wavelength 900 nm to 1200 nm) including the wavelength range of the excitation light and the range including 100 nm or more before and after the center of the wavelength band of the emitted light. 50%.

The wavelength of the fiber Bragg grating 14 is the wavelength of the desired output light.
FIG. 9 is an output spectrum diagram of the optical fiber laser light source 100 in a configuration in which the wavelength of the fiber Bragg grating 14 is, for example, a wavelength of 1112 nm.

As shown in FIG. 10, when the output side end of the amplified optical waveguide fiber 3 is a non-reflective terminal 8 ′, excitation light e having a wavelength of 915 nm is shown from the output side end of the amplified optical waveguide fiber 3 as shown in FIG. And a broad emission light r having a wavelength of 1050 nm to 1100 nm is output.
As shown in FIG. 12, when the first resonator K1 is configured by providing the output-side half mirror film 8 at the output-side end portion of the amplified optical waveguide fiber 3, the output of the output-side half mirror film 8 is as shown in FIG. The spectrum shown can be obtained.
That is, by providing the first resonator K1, output can be stabilized and noise can be reduced even in a wavelength band longer than 1100 nm.

FIG. 14A is a transmittance-wavelength characteristic diagram when the gap distance d in the parallel plate resonator (Fabry-Perot etalon) is 10 μm.
When the gap distance d is 10 μm, the transmittance peak interval is about 60 nm.
FIG. 14B is a transmittance-wavelength characteristic diagram when the gap distance d in the parallel plate resonator is 20 μm.
When the gap distance d is 20 μm, the transmittance peak interval is about 30 nm.
FIG. 14C is a transmittance-wavelength characteristic diagram when the gap distance d in the parallel plate resonator is 30 μm.
When the gap distance d is 30 μm, the transmittance peak interval is about 20 nm.
Since the input side gap N and the output side gap S in the optical fiber laser light source 100 perform the same function as the gap in the parallel plate resonator, the distance Ln between the input side gap N and the distance Ls between the output side gaps S is set to 20 μm or less. As a result, the transmittance peak interval is about 30 nm or more, mode hops are less likely to occur, and output stability can be improved.

FIG. 15A is an output-wavelength characteristic diagram of the first resonator K1 when the length L3 of the amplified optical waveguide fiber 3 is 15 m.
FIG. 15B is an output-wavelength characteristic diagram of the first resonator K1 when the length L3 of the amplified optical waveguide fiber 3 is 14 m.
The length L3 of the amplified optical waveguide fiber 3 is adjusted in order to emit emission light in a desired wavelength band.

FIG. 16A is an output-wavelength characteristic diagram of the first resonator K1 when the reflectance Rs of the output-side half mirror film 8 is about 50%.
FIG. 16B is an output-wavelength characteristic diagram of the first resonator K1 when the reflectance Rs of the output-side half mirror film 8 is about 40%.
The reflectance Rs of the output-side half mirror film 8 is adjusted in the range of 4% to 90% in order to emit emitted light in a desired wavelength band.

FIG. 17 is an SHG optical noise (rms) -excitation LD current characteristic diagram in the optical fiber laser light source 200 of FIG.
When the excitation LD current is increased, the excitation state (inversion distribution state) of Yb3 + is stabilized, and noise is reduced.
In order to suppress SHG optical noise (rms) to 2.5% or less, for example, the excitation LD current needs to be 3.3 A or more.
However, when the pumping LD current is set to 3.3 A or more, the output light power also increases, causing problems such as shortening the life of the SHG element 51.
Therefore, as shown in FIG. 18, the center axes of the fiber insertion holes of the ferrule 33 and the ferrule 34 are shifted. Then, the central axes of the core 3a of the amplified optical waveguide fiber 3 and the core 4a of the output optical waveguide fiber 4 are shifted, and the power of the output light can be attenuated.
Further, as shown in FIG. 19, the power of the output light can be attenuated by cutting at one point of the output optical waveguide fiber 4 and fusing it while shifting its axis.

  The polarization separating element 13 is arranged such that the 980 PANDA fiber 4 ′ is adjacent to the amplified optical waveguide fiber 4, the stress applying portions are arranged so as to be perpendicular to each other, softened with a flame or the like, and softened with the amplified optical waveguide. The fiber 4 and the 980 PANDA fiber 4 'are fused and drawn.

  In the polarization separation element 13, the longitudinal wave passes through the output optical waveguide fiber 4, and the transverse wave changes to the adjacent 980PANDA fiber 4 ′ and exits. As a result, only a longitudinal wave can be passed.

  In the coupling portion between the amplification optical waveguide fiber 3 and the output optical waveguide fiber 4, the temperature controller 10 is used to cool the heat due to coupling loss and the heat due to leakage of residual pumping light, and to prevent fluctuations in output characteristics due to temperature fluctuations. Adjust temperature to temperature.

  When the amplified optical waveguide fiber 3 is heated, the oscillation wavelength is shifted to the longer wavelength side, and when cooled, the oscillation wavelength is shifted to the shorter wavelength side. The temperature is adjusted by the temperature controller 50 so as to obtain a desired oscillation wavelength.

  According to the optical fiber laser light source 100 of the first embodiment, since the two-stage composite resonator structure including the first optical resonator K1 and the second optical resonator K2 is used, output stability is improved. Furthermore, since the distance Ln between the input side gap N and the distance Ls between the output side gaps S is set to 20 μm or less, mode hops are less likely to occur, and output stability is also improved in this respect.

  The optical fiber laser light source of the present invention can be used in laser microscope devices, biomedical analyzers, precision measuring devices, and the like.

DESCRIPTION OF SYMBOLS 1 Semiconductor excitation laser 2 Pumping optical waveguide fiber 3 Amplifying optical waveguide fiber 4 Output optical waveguide fiber 7 Input side filter film 8 Output side half mirror film 10 Temperature controller 13 Polarization separation element 14 Fiber Bragg grating 17, 18 Antireflection film 21 Beam splitter 22 Light receiving element 23 Control part 27, 28 Groove 35 Adhesive 37, 38 Adhesive 31, 32 Ferrule 33, 34 Ferrule 41, 42 Sleeve 50 Temperature controller 51 SHG element 100 Optical fiber laser light source 200 Optical fiber laser light source K1 1st resonator K2 2nd resonator N Input side gap S Output side gap

Claims (21)

[A] a pumping light waveguide fiber (2) for guiding pumping light output from the semiconductor pumping laser (1);
[B] An amplification optical waveguide fiber (3) that receives the excitation light output from the excitation light waveguide fiber (2), emits emission light of a predetermined wavelength band, and guides the light;
[C] an output optical waveguide fiber (4) for guiding the light output from the amplified optical waveguide fiber (3);
[D] An input side air gap (N) provided on the output side end face of the pumping optical waveguide fiber (2) and the input side end face of the amplification optical waveguide fiber (3), or the amplification An input side gap (N) is formed between the input side end face of the optical waveguide fiber (3) and the output side end face of the excitation light guide fiber (2), and reflects light in a predetermined wavelength band; An input side filter film (7) that transmits light of a predetermined wavelength band;
[E] An output side air gap (S) is formed between the output side end face of the output optical waveguide fiber (4) and the output side end face of the amplified optical waveguide fiber (3), or the amplification An output side air gap (S) is formed between the output side end face of the optical waveguide fiber (3) and the input side end face of the output optical waveguide fiber (4), and reflects light in a predetermined wavelength band; An output-side half mirror film (8) that transmits light in a predetermined wavelength band and forms a first optical resonator (K1) with the input-side filter film (7);
[F] A fiber Bragg grating (14) provided inside the output optical waveguide fiber (4) and constituting a second optical resonator (K2) with the input-side filter film (7). ,
[G] The optical fiber laser light source (100), wherein the distance (Ln) of the input side gap (N) and the distance (Ls) of the output side gap (S) are 20 μm or less. The optical fiber laser light source (100) according to claim 1,
The amplification optical waveguide fiber (3) includes a core (3a) to which a rare earth element is added as an amplification medium, and an inner cladding (3b) having a lower refractive index than the core (3a) provided outside the core (3a). And an outer cladding (3c) having a lower refractive index than the inner cladding (3b) provided outside the inner cladding (3b). The optical fiber laser light source (100) according to claim 1 or 2,
An optical fiber laser light source (100), wherein the length (L3) of the amplification optical waveguide fiber (3) is adjusted so that the emitted light of the predetermined wavelength band is emitted. In the optical fiber laser light source (100) according to any one of claims 1 to 3,
The optical fiber laser light source (100), wherein the input filter film (7) has a transmittance of 95% or more for the excitation light and a reflectance of 95% or more for the emitted light. In the optical fiber laser light source (100) according to any one of claims 1 to 4,
The optical fiber laser light source (100), wherein the output-side half mirror film (8) has a reflectance of 4% to 90% with respect to the emitted light. In the optical fiber laser light source (100) according to any one of claims 1 to 5,
An optical fiber laser light source (100), wherein the central axes of the core (3a) of the amplification optical waveguide fiber (3) and the core (4a) of the output optical waveguide fiber (4) are shifted. The optical fiber laser light source (100) according to any one of claims 1 to 6,
An optical fiber laser light source (100) characterized in that it is cut at one point of the output optical waveguide fiber (4) and fused by shifting its axis. In the optical fiber laser light source (100) according to any one of claims 1 to 7,
An optical fiber laser light source (100) comprising a polarization separation means (13) between the output-side half mirror film (8) and the fiber Bragg grating (14).   9. The optical fiber laser light source (100) according to claim 8, wherein the polarization separation means (13) comprises a polarization maintaining optical fiber fusion coupler type polarization separation element (13). (100). In the optical fiber laser light source (100) according to any one of claims 1 to 9,
An optical fiber laser light source (100), wherein the amplification optical waveguide fiber (3) and the output optical waveguide fiber (4) are polarization maintaining optical fibers.   The optical fiber laser light source (100) according to claim 10, wherein polarization axes of the amplification optical waveguide fiber (3) and the output optical waveguide fiber (4) are 0 ° or 90 °. An optical fiber laser light source (100). The optical fiber laser light source (100) according to any of claims 1 to 11,
Of the output side end face of the excitation light waveguide fiber (2) or the input side end face of the amplification optical waveguide fiber (3), an antireflection film (17) is provided on the side where the input side filter film (7) is not provided. An optical fiber laser light source (100) characterized by being provided. The optical fiber laser light source (100) according to any of claims 1 to 12,
Of the output side end face of the amplification optical waveguide fiber (3) or the input side end face of the output optical waveguide fiber (4), the antireflection film (18) is not provided on the output side half mirror film (8). An optical fiber laser light source (100) characterized in that is provided. The optical fiber laser light source (100) according to any of claims 1 to 13,
The output side end of the excitation light waveguide fiber (2) is fixed to the ferrule (31), and the input side end of the amplification light waveguide fiber (3) is fixed to the ferrule (32),
The output side end of the amplified optical waveguide fiber (3) is fixed to the ferrule (33), and the input side end of the output optical waveguide fiber (4) is fixed to the ferrule (34). An optical fiber laser light source (100). The optical fiber laser light source (100) according to claim 14,
The optical fiber laser light source (100), wherein the ferrule (31 to 34) is made of ceramics or transparent glass. The optical fiber laser light source (100) according to claim 14 or 15,
The amplification optical waveguide fiber (3) includes a core (3a) to which a rare earth element is added as an amplification medium, and an inner cladding (3b) having a refractive index lower than that of the core (3a) provided outside the core (3a). And an outer cladding (3c) having a lower refractive index than the inner cladding (3b) provided outside the inner cladding (3b),
The outer cladding (3c) of the portion inserted into the ferrule (33) at the output side end of the amplified optical waveguide fiber (3) is removed, and the refractive index is the same as or higher than that of the inner cladding (3b). An optical fiber laser light source (100), wherein the space between the insertion hole of the ferrule (33) and the inner clad (3b) is filled with an adhesive (35) and hardened. The optical fiber laser light source (100) according to claim 16,
When the ferrule (34) is made of transparent glass,
The fiber insertion port of the ferrule (34) into which the input side end of the output optical waveguide fiber (4) is inserted is processed into a conical shape and is gold-plated or silver-plated (36). Fiber laser light source (100). The optical fiber laser light source (100) according to any of claims 14 to 17,
An annular groove (27) is provided in at least one of the output side end face of the ferrule (31) and the input side end face of the ferrule (32), and the output side end face of the ferrule (31) and the input of the ferrule (32) are provided. Adhering a portion of the side end surface outside the groove (27) with an adhesive (37),
An annular groove (28) is provided in at least one of the output side end face of the ferrule (33) and the input side end face of the ferrule (34), and the output side end face of the ferrule (33) and the input of the ferrule (34) are provided. An optical fiber laser light source (100), wherein a portion of the side end face outside the groove (28) is bonded with an adhesive (38). The optical fiber laser light source (100) according to any of claims 14 to 18,
The ferrule (31) and the ferrule (32) are cylindrical with the same diameter, and both are held by a sleeve (41),
An optical fiber laser light source (100), wherein the ferrule (33) and the ferrule (34) are cylindrical with the same diameter, and both are held by a sleeve (42). The optical fiber laser light source (100) according to any of claims 1 to 19,
An optical fiber laser light source (100), characterized in that a temperature control means (10) is provided at a joint between the amplified optical waveguide fiber (3) and the output optical waveguide fiber (4). The optical fiber laser light source (100) according to any of claims 1 to 20,
An optical fiber laser light source (100) characterized in that a temperature adjusting means (50) for the amplification optical waveguide fiber (3) is provided.

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