WO2016117506A1 - Laser resonator device, laser device provided with same, and variable bandpass filter device - Google Patents

Abstract

A laser resonator device (1), provided with an optical system (2), an optical waveguide (3), a first resonance element (4), and a driving device (5). The optical system (2) collects light onto an optical axis (A). The optical waveguide (3) includes a gain medium. The gain medium emits light having a wavelength range greater than a single wavelength. The optical waveguide (3) causes light emitted by the gain medium to enter the optical system (2). The first resonance element (4) has an entry surface (4a) for reflecting some of the light collected by the optical system (2). The driving device (5) varies the position of the entry surface (4a) of the first resonance element (4) along the optical axis (A). Light having a wavelength corresponding to the position of the entry surface (4a) of the first resonance element (4) returns from the first resonance element (4) to the optical waveguide (3) via the optical system (2). Laser light (6) is thereby oscillated.

Description

Laser resonance device, laser device including the same, and variable bandpass filter device

The present invention relates to a laser resonance device, a laser device including the same, and a variable bandpass filter device.

Conventionally, in each field such as medical treatment, drug discovery, and optical measurement, a wavelength tunable laser capable of changing the wavelength (oscillation wavelength) of laser light is used. The wavelength tunable laser can change the wavelength of the laser beam while maintaining the coherence characteristic of the laser beam.

A general wavelength tunable laser includes a laser medium (gain medium) having a broad emission wavelength characteristic (wideband gain) and a spectroscope. A general tunable laser operates as follows. That is, first, light in a wide wavelength range (spontaneously emitted light) is emitted from the laser medium. Light emitted from the laser medium is spatially spread and dispersed for each wavelength by a spectroscope such as a diffraction grating or a prism. Light having a desired wavelength is selected from the spatially dispersed light and returned to the laser medium. As a result, laser light having a desired wavelength oscillates.

ス リ ッ ト A slit (transmission window with a wide space) and an angle adjustment mechanism are used as the mechanism for selecting light. Specifically, the slit is disposed in front of the diffraction grating or the prism. Light that has passed through the slit is incident on the diffraction grating or the prism. The angle adjusting mechanism adjusts the angle of the diffraction grating or the prism. Alternatively, the angle adjustment mechanism adjusts the angle of the output mirror that returns light to the laser medium. By adjusting the angle, only light having a desired wavelength out of spatially dispersed light is returned to the laser medium.

For example, Patent Document 1 discloses a wavelength tunable laser that changes the wavelength of laser light by adjusting the angle of a prism. Specifically, Patent Document 1 discloses that a blue semiconductor laser is used as an excitation light source and light in a wide wavelength range is emitted from a Pr ³⁺ (praseodymium) -added fluoride glass fiber. Patent Document 1 discloses that light emitted from a Pr ³⁺ -added fluoride glass fiber is spatially spread and dispersed for each wavelength using a prism. Patent Document 1 discloses that only light having a desired wavelength is returned to the Pr ³⁺ doped fluoride glass fiber by rotating the prism, that is, adjusting the angle of the prism.

As another wavelength tunable laser, a wavelength tunable laser using an etalon is known. The etalon includes two mirrors arranged in parallel. Light having a wavelength equivalent to the distance between the two mirrors resonates, and laser light oscillates. When the etalon is used, the wavelength of the laser beam can be changed by adjusting the distance between the two mirrors.

International Publication No. 2010/004882

However, a wavelength tunable laser using a diffraction grating or a prism needs to disperse light spatially. For this reason, it has been difficult to reduce the size of the laser resonator. In addition, a complicated operation is required to calibrate the position of each optical element such as a diffraction grating or a prism. Furthermore, in order to select a wavelength appropriately in a wavelength tunable laser using a diffraction grating or a prism, feedback control is necessary for adjusting the angle. For this reason, the configuration is complicated.

On the other hand, a wavelength tunable laser that uses an etalon does not need to spatially disperse light, so that the laser resonator can be miniaturized. However, it is necessary to adjust the distance between the two mirrors so that the distance between the two mirrors is equal to the desired wavelength. For this reason, it was necessary to adjust the distance between the two mirrors on the nanometer (nm) order. Furthermore, the wavelength tunable laser using the etalon requires a feedback control to adjust the distance between the two mirrors, and the configuration is complicated.

An object of the present invention is to provide a laser resonator capable of changing a wavelength to be selected with a simple configuration, a laser device including the laser resonator, and a variable bandpass filter device.

A laser resonance apparatus according to the present invention includes an optical system, an optical waveguide, a first resonance element, and a drive device. The optical system collects light on the optical axis. The optical waveguide includes a gain medium that emits light in a wavelength range wider than a single wavelength, and the light emitted from the gain medium is incident on the optical system. The first resonance element has an incident surface that reflects part of the light collected by the optical system. The drive device changes the position of the incident surface along the optical axis. Or the said drive device changes the position of the optical element which comprises the said optical system along the said optical axis. Light having a wavelength corresponding to the position of the incident surface or the position of the optical element returns from the first resonant element to the optical waveguide through the optical system. Thereby, a laser beam oscillates.

In one embodiment, the optical system includes two condenser lenses as the optical element. The drive device changes the position of the incident surface. Alternatively, the driving device changes the position of the condensing lens closer to the first resonance element among the two condensing lenses.

In one embodiment, the optical system includes a single gradient index lens as the optical element. The drive device changes the position of the incident surface. Alternatively, the driving device changes the position of the gradient index lens.

In one embodiment, the first resonance element has a saturable absorption characteristic.

In one embodiment, the laser resonance apparatus further includes a second resonance element that transmits excitation light and reflects light emitted from the gain medium. The optical waveguide is an optical fiber, and the optical fiber includes an incident end on which the excitation light is incident. The second resonance element is provided at the incident end, and the gain medium is contained in a core portion of the optical fiber.

In one embodiment, the gain medium includes an ionized rare earth element, an ionized transition element, or bismuth.

In one embodiment, the rare earth element is cerium, praseodymium, neodymium, samarium, europium, ytterbium, erbium, or thulium. The transition element is copper or tin.

In one embodiment, the optical fiber includes fluoride glass. In this case, the gain medium may include ionized praseodymium.

In one embodiment, the core portion of the optical fiber includes quartz glass to which an ionized rare earth element, an ionized transition element, or bismuth is added using zeolite. In this case, the gain medium may include ionized neodymium or ytterbium. The length of the optical fiber may be 1 mm or more.

In one embodiment, the optical waveguide is a semiconductor laser.

A laser apparatus according to the present invention includes the above laser resonance apparatus and an excitation light source. The excitation light source generates excitation light incident on the optical waveguide.

The variable band-pass filter device according to the present invention includes an optical system, a first optical waveguide, and a driving device. The optical system collects light on the optical axis. The first optical waveguide has an incident end to which light collected by the optical system is irradiated. The drive device changes the position of the incident end of the first optical waveguide or the position of the optical element constituting the optical system along the optical axis. Light having a wavelength corresponding to the position of the incident end of the first optical waveguide or the position of the optical element is incident on the inside of the first optical waveguide from the incident end of the first optical waveguide.

In one embodiment, the variable bandpass filter device further includes a second optical waveguide. The second optical waveguide emits light toward the optical system. In this case, at least one of the first optical waveguide and the second optical waveguide may include a gain medium.

According to the present invention, the wavelength to be selected can be changed with a simple configuration.

(A) is a figure which shows the structure of the laser resonance apparatus which concerns on 1st Embodiment of this invention. (B) is sectional drawing of the optical fiber which concerns on 1st Embodiment of this invention. It is a front view which shows the output mirror and drive device which concern on 1st Embodiment of this invention. (A) is a figure which shows the axial chromatic aberration of the condensing lens which concerns on 1st Embodiment of this invention. (B) is a figure which shows the relationship between the position of the output mirror which concerns on 1st Embodiment of this invention, and the oscillation wavelength of a laser beam. (C) is a figure which shows the other relationship between the position of the output mirror which concerns on 1st Embodiment of this invention, and the oscillation wavelength of a laser beam. It is a figure which shows the structural example of the laser apparatus which concerns on 1st Embodiment of this invention. It is a figure which shows the structure of the laser resonance apparatus which concerns on 2nd Embodiment of this invention. It is a graph which shows the wavelength dependence characteristic of the focal position of the gradient index lens which concerns on 2nd Embodiment of this invention. It is a figure which shows the structure of the laser resonance apparatus which concerns on 3rd Embodiment of this invention. It is a front view which shows the condensing lens and drive device which concern on 3rd Embodiment of this invention. (A) is a figure which shows the relationship between the position of the condensing lens which concerns on 3rd Embodiment of this invention, and the oscillation wavelength of a laser beam. (B) is a figure which shows the other relationship between the position of the condensing lens which concerns on 3rd Embodiment of this invention, and the oscillation wavelength of a laser beam. It is a figure which shows the structure of the laser resonance apparatus which concerns on 4th Embodiment of this invention. It is a figure which shows the structure of the variable type band pass filter apparatus concerning 5th Embodiment of this invention. It is a graph which shows the measurement result which concerns on the Example of this invention. It is a graph which shows the measurement result which concerns on the Example of this invention. It is a graph which shows the measurement result which concerns on the Example of this invention. It is a graph which shows the measurement result which concerns on the Example of this invention. It is a graph which shows the measurement result which concerns on the Example of this invention. It is a graph which shows the measurement result which concerns on the Example of this invention. It is a graph which shows the measurement result which concerns on the Example of this invention. It is a graph which shows the measurement result which concerns on the Example of this invention. It is a graph which shows the measurement result which concerns on the Example of this invention. It is a graph which shows the measurement result which concerns on the Example of this invention. It is a graph which shows the measurement result which concerns on the Example of this invention. It is a graph which shows the measurement result which concerns on the Example of this invention. It is a graph which shows the measurement result which concerns on the Example of this invention. It is a graph which shows the measurement result which concerns on the Example of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, in the figures, the same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated. In order to facilitate understanding, the drawings schematically show each component as a main component. The materials, shapes, dimensions, etc. shown in the following embodiments are merely examples, and are not particularly limited.

[First Embodiment]
First, with reference to FIG. 1A, the configuration of the laser resonator 1 according to the first embodiment will be described. FIG. 1A is a diagram illustrating a configuration of the laser resonator 1 according to the first embodiment. As shown in FIG. 1A, the laser resonance apparatus 1 includes an optical system 2, an optical fiber 3 (an example of an optical waveguide), an output mirror 4 (an example of a first resonance element), and a drive device 5. . In the following description, the optical system 2 may be referred to as the first optical system 2.

The first optical system 2 collects light on the optical axis A. The optical fiber 3 includes a gain medium that emits light in a wavelength range wider than a single wavelength, and the light emitted from the gain medium enters the optical system 2. The output mirror 4 has an incident surface 4 a that reflects a part of the light collected by the first optical system 2. The driving device 5 changes the position of the incident surface 4 a of the output mirror 4 along the optical axis A. Light having a wavelength corresponding to the position of the incident surface 4 a of the output mirror 4 returns from the output mirror 4 to the optical fiber 3 via the first optical system 2. Thereby, the laser beam 6 having the wavelength of the light returned to the optical fiber 3 oscillates.

As described above, the wavelength of the light returned to the optical fiber 3 can be changed with a simple configuration in which the driving device 5 changes the position of the incident surface 4a of the output mirror 4 along the optical axis A. That is, the wavelength of the laser beam 6 can be changed. Hereinafter, the laser resonance apparatus 1 according to the first embodiment will be described in detail.

The laser resonance apparatus 1 according to the first embodiment further includes a dielectric multilayer film 8 (an example of a second resonance element). The dielectric multilayer film 8 is provided at the incident end of the optical fiber 3. The laser resonator 1 according to the first embodiment oscillates the laser light 6 when the excitation light 7 is incident on the incident end of the optical fiber 3 via the dielectric multilayer film 8. The laser beam 6 is a continuous wave (CW: Continuous Wave). The output of the laser light 6 depends on the output of the excitation light 7. The output of the laser beam 6 can be about several millimeters to several tens of millimeters.

The optical fiber 3 includes a core portion 3a and a clad portion 3b. The core part 3a contains a laser medium (gain medium). The laser medium of the present embodiment has a broadband emission wavelength characteristic (wideband gain). That is, the laser medium of the present embodiment emits light (spontaneously emitted light) in a wavelength range wider than a single wavelength when the excitation light 7 is irradiated. The refractive index of the core portion 3a is larger than that of the cladding portion 3b. The clad part 3b is provided around the core part 3a.

One end (left end in FIG. 1) of the optical fiber 3 is an incident end on which the excitation light 7 is incident. The incident end of the optical fiber 3 can be polished at a right angle. From the incident end of the optical fiber 3, one end face of each of the core part 3a and the clad part 3b is exposed.

The dielectric multilayer film 8 is formed in close contact with the incident end of the optical fiber 3. The dielectric multilayer film 8 transmits the excitation light 7 and reflects the light emitted from the core portion 3a. The dielectric multilayer film 8 preferably has a reflectivity of 100% with respect to the light emitted from the core portion 3a in order to improve the laser output efficiency. Specifically, the dielectric multilayer film 8 is designed so as to have a reflectance of 100% with respect to light having a wavelength within the variable range in accordance with the variable range of the wavelength (oscillation wavelength) of the laser light 6. It is preferable.

When the excitation light 7 enters the core portion 3a through the dielectric multilayer film 8, the core portion 3a emits light. Light (spontaneously emitted light) emitted from the core portion 3a is emitted from the other end (right end in FIG. 1) of the optical fiber 3. Therefore, the other end of the optical fiber 3 is an emission end from which light emitted from the core portion 3a is emitted. The exit end of the optical fiber 3 can be polished at a right angle. From the output end of the optical fiber 3, the other end face of each of the core part 3a and the clad part 3b is exposed.

The first optical system 2 and the output mirror 4 are arranged in this order along the optical axis A of the light emitted from the exit end of the optical fiber 3 in front of the exit end of the optical fiber 3. In the first embodiment, the first optical system 2 includes a pair of condenser lenses 2a and 2b (an example of an optical element). Therefore, the exit end of the optical fiber 3, the pair of condensing lenses 2 a and 2 b constituting the first optical system 2, and the output mirror 4 are arranged along the optical axis A. Hereinafter, the condenser lens 2a may be referred to as a first condenser lens 2a, and the condenser lens 2b may be referred to as a second condenser lens 2b.

The light emitted from the exit end of the optical fiber 3 is applied to the first condenser lens 2a to become parallel light. The parallel light is applied to the second condenser lens 2b and is condensed toward the focal position of the second condenser lens 2b. The focal position of the second condenser lens 2b exists on the optical axis A. Accordingly, the parallel light is condensed on the optical axis A by the second condenser lens 2b. The output mirror 4 reflects a part of the light collected by the second condenser lens 2b and transmits the remaining light. The output mirror 4 can be a dielectric mirror. The light reflected by the output mirror 4 returns to the optical fiber 3 via the first optical system 2 (a pair of condensing lenses 2a and 2b).

The driving device 5 can change the position of the output mirror 4 along the optical axis A. When the drive device 5 changes the position of the output mirror 4, the position of the incident surface 4 a (surface on the second condenser lens 2 b side) of the output mirror 4 changes along the optical axis A. In the first embodiment, of the light returning to the optical fiber 3, only light having a wavelength (color) corresponding to the position of the incident surface 4a of the output mirror 4 is incident on the core portion 3a. That is, only light having a wavelength corresponding to the position of the incident surface 4a of the output mirror 4 is condensed on the end surface of the core portion 3a (the surface on the emission end side of the optical fiber 3) by the first condenser lens 2a. As a result, only light having a wavelength corresponding to the position of the incident surface 4 a of the output mirror 4 reciprocates between the dielectric multilayer film 8 and the output mirror 4. Therefore, the laser beam 6 having a wavelength (oscillation wavelength) corresponding to the position of the incident surface 4 a of the output mirror 4 oscillates, and part of the oscillated laser beam 6 passes through the output mirror 4. Thus, the wavelength of the laser beam 6 can be changed only by linear movement of the output mirror 4 along the optical axis A. Therefore, the wavelength of the laser beam 6 can be changed with a simple configuration. In addition, the wavelength of the laser beam 6 can be selected with a simple configuration.

The distance L1 from the exit end of the optical fiber 3 to the incident surface 4a of the output mirror 4 (hereinafter referred to as the optical system length L1) is mainly the maximum moving distance of the output mirror 4 by the drive device 5 and a pair of collecting points. It is determined by the thickness of each of the optical lenses 2a and 2b and the focal length f. The maximum moving distance of the output mirror 4 is, for example, about 100 μm to 130 μm. In the present embodiment, the dielectric multilayer film 8 and the output mirror 4 constitute a laser resonator. In the present embodiment, the distance L2 from the dielectric multilayer film 8 to the output mirror 4 (hereinafter referred to as the resonator length L2) mainly includes the optical system length L1 and the length L3 of the optical fiber 3 (hereinafter referred to as “resonator length L2”). It is described as fiber length L3).

FIG. 1B is a cross-sectional view of the optical fiber 3. The diameter D1 of the core part 3a may be 2 μm or more and 100 μm or less. The diameter D2 of the clad 3b (the diameter of the optical fiber 3) can be 50 μm or more and 2000 μm or less. By setting the diameter D1 of the core portion 3a to 2 μm or more and 100 μm or less, it is possible to select the wavelength of light to be oscillated. The optical fiber 3 of the present embodiment is a single mode fiber. However, the optical fiber 3 is not limited to a single mode fiber. The optical fiber 3 may be a multimode fiber or a double clad fiber. Glass materials such as quartz glass and fluoride glass can be used for the material of the core portion 3a and the cladding portion 3b. Or resin may be used for the material of the core part 3a and the clad part 3b.

The core portion 3a contains an ionized rare earth element, an ionized transition element, or bismuth (Bi) as a laser medium. Examples of ionized rare earth elements include cerium (Ce ³⁺ ), praseodymium (Pr ³⁺ ), neodymium (Nd ³⁺ ), samarium (Sm ³⁺ ), europium (Er ³⁺ ), ytterbium (Yb ³⁺ ). , Erbium (Er ³⁺ ), or Thulium (Tm ³⁺ ) may be doped into the core portion 3a. Further, copper (Cu ⁺ ) or tin (Sn ²⁺ ) can be doped into the core portion 3a as an ionized transition element. By using cerium (Ce ³⁺ ), praseodymium (Pr ³⁺ ), samarium (Sm ³⁺ ), europium (Er ³⁺ ), copper (Cu ⁺ ), or tin (Sn ²⁺ ) as the laser medium The wavelength can be changed (selected) within the visible light range. Further, by using neodymium (Nd ³⁺ ), ytterbium (Yb ³⁺ ), erbium (Er ³⁺ ), thulium (Tm ³⁺ ), or bismuth (Bi) as the laser medium, the near infrared range It is possible to change (select) the wavelength within. Erbium (Er ³⁺ ) also allows for wavelength changes (selection) within the mid-infrared range.

FIG. 2 is a front view showing the output mirror 4 and the driving device 5. As shown in FIG. 2, the output mirror 4 is supported by a first mirror holder 9. Therefore, the laser resonator 1 described with reference to FIG. 1A further includes a first mirror holder 9.

The first mirror holder 9 is fixed to the driving device 5. As the driving device 5, a stage capable of position control on the order of micrometers (μm) can be used. For example, the driving device 5 is a slide type single-axis stage.

Subsequently, the wavelength variable mechanism of the laser beam 6 in the first embodiment will be described with reference to FIGS. 3 (a) to 3 (c). In the specific example described with reference to FIGS. 3A to 3C, the second condenser lens 2b is a plano-convex lens, but the second condenser lens 2b is limited to a plano-convex lens. is not.

In this embodiment, the oscillation wavelength of the laser beam 6 is changed by utilizing the axial chromatic aberration that the lens generally has. On-axis chromatic aberration indicates the property of a lens that the focal position (imaging position) of light on the optical axis differs for each wavelength (color) of light.

FIG. 3A is a diagram showing the axial chromatic aberration of the second condenser lens 2b. As shown in FIG. 3A, when the light S1 having the wavelength W1 is incident on the second condenser lens 2b, the light S1 is condensed at a position P1 on the optical axis A. Further, when the light S2 having the wavelength W2 is incident on the second condenser lens 2b, the light S2 is condensed at the position P2 on the optical axis A. The position P2 is a position different from the position P1. In general, the shorter the wavelength, the higher the refractive index. Therefore, when a general lens is used for the second condenser lens 2b, the wavelength W1 of the light S1 condensed at the position P1 is shorter than the wavelength W2 of the light S2 condensed at the position P2.

FIG. 3B is a diagram showing the relationship between the position of the output mirror 4 and the oscillation wavelength of the laser beam 6. Specifically, FIG. 3B shows the position of the output mirror 4 for oscillating the laser beam 6 having the wavelength W1. As shown in FIG. 3B, when the position of the incident surface 4a of the output mirror 4 is positioned at the position P1, only the light S1 having the wavelength W1 returns to the end surface of the core portion 3a described with reference to FIG. . That is, only the light S1 having the wavelength W1 is incident (returned) into the core portion 3a. As a result, the laser beam 6 having the wavelength W1 oscillates. When the position of the incident surface 4a of the output mirror 4 is positioned at the position P1, the light S2 (wavelength W2) does not form an image on the end surface of the core portion 3a. In other words, the light S <b> 2 reflected by the output mirror 4 becomes a blurred image at the exit end of the optical fiber 3.

FIG. 3C is a diagram showing another relationship between the position of the output mirror 4 and the oscillation wavelength of the laser beam 6. Specifically, FIG. 3C shows the position of the output mirror 4 for oscillating the laser beam 6 having the wavelength W2. As shown in FIG. 3C, when the laser beam 6 having the wavelength W2 is oscillated, the output mirror 4 is moved along the optical axis A so that the position of the incident surface 4a of the output mirror 4 is a position P2. Position to. At this time, the position of the incident surface 4a of the output mirror 4 can be positioned at the position P2 by moving the output mirror 4 on the order of μm.

When the position of the incident surface 4a of the output mirror 4 is positioned at the position P2, only the light S2 having the wavelength W2 returns to the end surface of the core portion 3a described with reference to FIG. That is, only the light S2 having the wavelength W2 enters (returns) into the core portion 3a. Therefore, the laser beam 6 having the wavelength W2 oscillates. When the position of the incident surface 4a of the output mirror 4 is positioned at the position P2, the light S1 (wavelength W1) does not form an image on the end surface of the core portion 3a. In other words, the light S <b> 1 reflected by the output mirror 4 becomes a blurred image at the exit end of the optical fiber 3.

Next, an example of a laser device 10 that can be configured using the laser resonator 1 shown in FIG. 1A will be described with reference to FIG. FIG. 4 is a diagram illustrating a configuration example of the laser device 10. As shown in FIG. 4, the laser device 10 includes a laser resonance device 1. The laser device 10 further includes an excitation light source 11, a second optical system 12, and a ferrule 13.

The excitation light source 11 generates and emits the excitation light 7 described with reference to FIG. The excitation light source 11 is selected according to the type of laser medium contained in the core portion 3a of the optical fiber 3. Specifically, when the laser medium is praseodymium (Pr ³⁺ ), a blue semiconductor laser that emits laser light (excitation light 7) having a wavelength of 430 nm or more and 480 nm or less is used as the excitation light source 11. When the laser medium is neodymium (Nd ³⁺ ), a near-infrared semiconductor laser that emits laser light having a wavelength of 800 nm (excitation light 7) is used as the excitation light source 11. When the laser medium is ytterbium (Yb ³⁺ ) or erbium (Er ³⁺ ), a near-infrared semiconductor laser that emits laser light having a wavelength of 975 nm (excitation light 7) is used as the excitation light source 11. When the laser medium is thulium (Tm ³⁺ ), a near-infrared semiconductor laser that emits laser light (excitation light 7) having a wavelength of 780 nm is used as the excitation light source 11.

The excitation light 7 emitted from the excitation light source 11 is incident on one end of the ferrule 13 via the second optical system 12. The optical fiber 3 is fixed in the ferrule 13. The excitation light 7 incident on the ferrule 13 is applied to the dielectric multilayer film 8 to excite the core portion 3a. As a result, the core portion 3a emits light. In the present embodiment, the second optical system 12 is an optical fiber. However, the second optical system 12 is not limited to an optical fiber. The second optical system 12 may be composed of one or a plurality of optical elements (for example, lenses and mirrors). In this case, the ferrule 13 can be omitted.

As described above, according to the first embodiment, the wavelength of the laser beam 6 can be changed by moving the output mirror 4 along the optical axis A. In addition, the wavelength of the laser beam 6 can be selected. Therefore, it is not necessary to spatially disperse the light emitted from the optical fiber 3 (spontaneously emitted light emitted from the laser medium), so that the laser resonator can be miniaturized. Furthermore, since the optical system length L1 can be shortened, the resonator length L2 can be shortened.

Further, in a general wavelength tunable laser that disperses light using a diffraction grating or a prism, complicated work is required for calibration of the position of each optical element such as the diffraction grating or the prism. On the other hand, in the first embodiment, the optical elements of the emission end of the optical fiber 3, the condensing lenses 2a and 2b constituting the first optical system 2, and the output mirror 4 are arranged along the optical axis A. The Accordingly, calibration of the position of each optical element such as the exit end of the optical fiber 3 is facilitated. Specifically, each of the output ends of the optical fiber 3 is confined so that the reflected light from the output mirror 4 is confined within the divergence angles of the condenser lenses 2a and 2b and the numerical aperture (NA) of the optical fiber 3. It is only necessary to calibrate the position of the optical element.

Further, in a general wavelength tunable laser using a diffraction grating or a prism and a general wavelength tunable laser using an etalon, feedback control is required, and the configuration becomes complicated. On the other hand, according to the first embodiment, it is only necessary to move the output mirror 4 on the order of μm along the optical axis A (positioning is required), and the wavelength of the laser light 6 is changed with a simple configuration. Can be made.

Also, in a general wavelength tunable laser using an etalon, it is necessary to adjust the distance between two mirrors on the order of nm. On the other hand, according to the first embodiment, it is only necessary to move the output mirror 4 along the optical axis A on the order of μm (it is sufficient to position it), and high-precision positioning is not required.

As described above, according to the first embodiment, the wavelength of the laser beam 6 can be changed with a simple configuration. Therefore, the number of parts can be reduced. In addition, the laser resonator can be miniaturized. Furthermore, maintenance becomes easy. Therefore, it is possible to provide a tunable laser that is small and robust and low in cost.

In addition, the laser resonance apparatus 1 and the laser apparatus 10 of the first embodiment can be applied to various fields such as a medical field, a laser measurement field, a laser measurement field, and an optical communication field by appropriately selecting a laser medium. .

Further, according to the first embodiment, the drive device 5 continuously changes the position of the output mirror 4 so that automatic wavelength sweeping is possible. The wavelength automatic sweep function is a useful function in various fields such as the medical field and the laser measurement field.

Furthermore, according to the first embodiment, it is possible to further shorten the resonator length L2 by using the optical fiber 3 having a short fiber length L3.

For example, the use of a weatherproof fluoralumino-aluminate glass fiber (WPFGF) to which praseodymium (Pr ³⁺ ) is added as the optical fiber 3 can shorten the fiber length L3. . Hereinafter, the weather-resistant fluoroaluminate glass fiber to which Pr ³⁺ is added is referred to as Pr: WPFGF. Fluoroaluminate glass is a kind of fluoride glass.

Specifically, the fiber length L3 of Pr: WFGF can be set to 40 mm. Therefore, by using Pr: WPFGF having a fiber length L3 of 40 mm as the optical fiber 3, the resonator length L2 can be further shortened.

For example, 3000 ppm of Pr ³⁺ is added to the core portion 3a of Pr: WPFGF. In addition, the diameter D1 of the core portion 3a of Pr: WPFGF may be 8 μm. The diameter of Pr: WPFGF (the diameter D2 of the cladding part 3b) may be 300 μm. As the excitation light 7 for Pr: WFGF, for example, blue laser light (quasi-continuous wave) emitted from a gallium nitride semiconductor laser is used. Pr: WPFGF can oscillate blue-green, green, and red laser beams 6. Therefore, by using Pr: WPFGF, the wavelength can be varied in the visible light band.

Further, by using a quartz glass fiber (Nd-doped silica fiber) added with neodymium (Nd ³⁺ ) as the optical fiber 3, the fiber length L3 can be further shortened. Hereinafter, the quartz glass fiber added with Nd ³⁺ is referred to as an Nd ^{3 +} -added quartz glass fiber.

Specifically, the fiber length L3 of the Nd ³⁺ added quartz glass fiber can be shortened to 1 mm. Therefore, by using the Nd ³⁺ doped quartz glass fiber as the optical fiber 3, the resonator length L2 can be further shortened.

Nd ^{3+ -added} quartz glass (hereinafter referred to as Nd ³⁺ core glass), which is a material of the core portion 3a of the Nd ^{3 +} -added quartz glass fiber, can be produced by a zeolite method. Zeolite methods are described, for example, in literature 1 “Y. Fujimoto, M. Nakatsuka,“ A novel method for uniform form of the earth earth in SiO ₂ glass using Zeol 15th year, J. Vol. 182-191. Also, an Nd ^{3 +} -added silica glass fiber having a fiber length L3 of 4 mm is described in Reference 2: “Motoichiro Murakami et al.,“ Short-length fiber laser oscillation in 4 ”. -Mm Nd-doped Silica fiber fabricated by zeolite method ", ptics Communications, 2014 year, # 328, Volume, are described in the 121-123 pages ".

As the excitation light source 11 for the Nd ³⁺ doped quartz glass fiber, a semiconductor laser that emits laser light having a wavelength of 810 nm can be used. The laser beam 6 oscillated from the Nd ³⁺ doped quartz glass fiber is a near infrared laser. Therefore, by using the Nd ³⁺ doped quartz glass fiber, the wavelength can be varied in the near infrared band.

Nd ³⁺ core glass can be produced by the following method (zeolite method). That is, first, sodium (Na) ions of the X-type zeolite are replaced with neodymium ions by an ion exchange method. Next, the substituted X-type zeolite and colloidal quartz are mixed. Then water is added to form a slurry. Then, the slurry is stirred and dried. Thereby, a dry powder can be obtained. Finally, the dried powder can be sintered at 1800 ° C. to obtain Nd ³⁺ core glass. The composition of the Nd ³⁺ core glass is, for example, 1.25 wt% of the acid value neodymium (Nd ₂ O ₃ ), 2.72 wt% of aluminum oxide (Al ₂ O ₃ ), and 96.03 wt. Of silicon dioxide (SiO ₂ ). %. The composition of the Nd ³⁺ core glass can be measured by X-ray emission analysis.

The Nd ³⁺ doped quartz glass fiber can be manufactured by a rod-in-tube method. That is, first, Nd ³⁺ core glass is formed into a rod shape. The diameter of the Nd ³⁺ core glass formed into a rod shape is, for example, 1 mm. Next, the Nd ³⁺ core glass formed into a rod shape is inserted into a quartz glass tube to form a base material. For example, the inner diameter of the quartz glass tube is 1 mm, and the outer diameter of the quartz glass tube is 12 mm. Thereafter, by drawing the base material, an Nd ³⁺ added quartz glass fiber can be obtained. The diameter D1 of the core portion 3a of the Nd ³⁺ added quartz glass fiber can be 12 μm. The diameter of the Nd ³⁺ doped quartz glass fiber (the diameter D2 of the cladding part 3b) may be 144 μm. The refractive index of the clad portion 3b of the Nd ³⁺ added quartz glass fiber is, for example, 1.4545, and the refractive index of the core portion 3a of the Nd ³⁺ added quartz glass fiber is, for example, 1.4499. The refractive index of the core portion 3a and the cladding portion 3b of the Nd ³⁺ added quartz glass fiber can be measured by a spectroscopic ellipsometer.

Note that ytterbium (Yb ³⁺ ) may be used instead of neodymium (Nd ³⁺ ). Even when ytterbium (Yb ³⁺ ) is used, a quartz glass fiber capable of shortening the fiber length L3 to 1 mm can be produced.

[Second Embodiment]
Next, the second embodiment will be described. However, items different from the first embodiment will be described, and descriptions of the same items as the first embodiment will be omitted. The laser resonance device 1 and the laser device 10 according to the second embodiment are different from the first embodiment in the first optical system 2.

FIG. 5 is a diagram showing a configuration of the laser resonance apparatus 1 according to the second embodiment. As shown in FIG. 5, in the laser resonance apparatus 1 according to the second embodiment, the first optical system 2 includes a single gradient index (GRIN) lens 2c as an optical element.

FIG. 6 is a graph showing the wavelength dependence characteristics of the focal position of the gradient index lens 2c. In FIG. 6, the horizontal axis indicates the wavelength [nm] of light incident on the gradient index lens 2c, and the vertical axis indicates the focal position shift amount [μm] along the optical axis A. Specifically, FIG. 6 shows values calculated by optical analysis software (CODE V).

As shown in FIG. 6, in the wavelength range of 600 nm to 700 nm, the focal position shifts approximately 130 μm substantially linearly along the optical axis A. Therefore, as in the first embodiment, the wavelength (oscillation wavelength) of the laser light 6 can be changed by positioning the incident surface 4a of the output mirror 4 at the focal position at each wavelength. Specifically, when the output mirror 4 is moved (shifted) by 1.3 μm, the wavelength of the laser beam 6 changes by 1 nm.

According to the second embodiment, by using the gradient index lens 2c, the first optical system 2 can be configured by a single lens. The diameter of the gradient index lens 2c is about 2 mm to 3 mm, and the length of the gradient index lens 2c is about 5 mm to 6 mm. Therefore, the optical system length L1 can be shortened, and hence the resonator length L2 can be shortened. For example, by using Pr: WFGF with a fiber length L3 of 40 mm as the optical fiber 3, the resonator length L2 can be reduced to about 5 cm to 6 cm. Further, by using an Nd ³⁺ doped silica glass fiber having a fiber length L3 of 4 mm as the optical fiber 3, the resonator length L2 can be set to about 1 cm to 2 cm.

In addition, by using the gradient index lens 2c, the output of the laser beam 6 can be several tens of milliwatts.

[Third Embodiment]
Next, a third embodiment will be described. However, items different from the first embodiment will be described, and descriptions of the same items as the first embodiment will be omitted. The laser resonance apparatus 1 and the laser apparatus 10 according to the third embodiment are different from the first embodiment in that the second condenser lens 2b is moved (shifted) to change the wavelength.

FIG. 7 is a diagram showing a configuration of the laser resonance apparatus 1 according to the third embodiment. As shown in FIG. 7, in the laser resonance apparatus 1 according to the third embodiment, the driving device 5 transmits the position of the condenser lens 2b closer to the output mirror 4 out of the two condenser lenses 2a and 2b. Change along axis A.

FIG. 8 is a front view showing the second condenser lens 2b and the driving device 5 according to the third embodiment. As shown in FIG. 8, the second condenser lens 2 b is supported by the second mirror holder 21. Therefore, the laser resonator 1 shown in FIG. 7 further includes the second mirror holder 21. The second mirror holder 21 is fixed to the driving device 5.

Subsequently, the wavelength variable mechanism of the laser beam 6 in the third embodiment will be described with reference to FIGS. Also in the third embodiment, as in the first embodiment, the wavelength (oscillation wavelength) of the laser beam 6 is changed using the axial chromatic aberration that the lens generally has. In the specific example described with reference to FIGS. 9A and 9B, the second condenser lens 2b is a plano-convex lens, but the second condenser lens 2b is limited to a plano-convex lens. is not.

FIG. 9A is a diagram showing the relationship between the position of the second condenser lens 2b and the oscillation wavelength of the laser light 6. FIG. Specifically, FIG. 9A shows the position of the second condenser lens 2b for oscillating the laser beam 6 having the wavelength W11. As shown in FIG. 9A, when the light S11 having the wavelength W11 is condensed on the incident surface 4a of the output mirror 4 by the second condenser lens 2b, only the light S11 having the wavelength W11 is shown in the core shown in FIG. Return to the end surface of the portion 3a (surface on the output end side of the optical fiber 3). That is, only the light S11 having the wavelength W11 enters (returns) the core portion 3a. As a result, the laser beam 6 having the wavelength W11 oscillates. At this time, the light S12 having the wavelength W12 different from the light S11 does not form an image on the end face of the core portion 3a. In other words, the light S12 reflected by the output mirror 4 becomes a blurred image at the exit end of the optical fiber 3.

FIG. 9B is a diagram showing another relationship between the position of the second condenser lens 2 b and the oscillation wavelength of the laser light 6. Specifically, FIG. 9B shows the position of the second condenser lens 2b for oscillating the laser beam 6 having the wavelength W12. As shown in FIG. 9B, when the laser beam 6 having the wavelength W12 is oscillated, the second condenser lens 2b is moved along the optical axis A so that the light S12 having the wavelength W12 is output mirror. 4 is focused on the incident surface 4a. Thereby, only the light S12 having the wavelength W12 returns to the end face of the core portion 3a shown in FIG. That is, only the light S12 having the wavelength W12 enters (returns) into the core portion 3a. As a result, the laser beam 6 having the wavelength W12 oscillates. At this time, the light S11 does not form an image on the end face of the core portion 3a. In other words, the light S11 reflected by the output mirror 4 becomes a blurred image at the exit end of the optical fiber 3.

In the third embodiment, the first optical system 2 includes two condensing lenses 2a and 2b. However, the configuration of the first optical system 2 is not limited to this configuration. As described in the second embodiment, the first optical system 2 may be configured by a single gradient index lens 2c. In this case, the driving device 5 changes the position of the gradient index lens 2c along the optical axis A.

[Fourth Embodiment]
Next, a fourth embodiment will be described. However, items different from the first embodiment will be described, and descriptions of the same items as the first embodiment will be omitted. The laser resonance apparatus 1 and the laser apparatus 10 according to the fourth embodiment are different from the first embodiment in that the output mirror 4 has saturable absorption characteristics.

FIG. 10 is a diagram showing a configuration of the laser resonance apparatus 1 according to the fourth embodiment. As shown in FIG. 10, in the laser resonator 1 according to the fourth embodiment, a saturable absorber (SA) 22 is installed on the incident surface 4 a of the output mirror 4. Thereby, a saturable absorption characteristic can be imparted to the output mirror 4. For the saturable absorber 22, carbon nanotubes, graphene, or the like can be used. Since the output mirror 4 has saturable absorption characteristics, a pulse laser by a Q switch or a mode lock can be configured.

In addition, although the form which installs the saturable absorber 22 in the entrance plane 4a of the output mirror 4 is demonstrated in 4th Embodiment, the output mirror 4 itself may have a saturable absorption characteristic. For example, by using a semiconductor saturable absorber mirror (SESAM) as the output mirror 4, the output mirror 4 itself can have saturable absorption characteristics.

In the above, embodiments of the laser resonator device and the laser device according to the present invention have been described with reference to the drawings. However, the laser resonator according to the present invention is not limited to the above embodiment, and can be implemented in various modes without departing from the gist thereof.

For example, in the embodiments of the laser resonator device and the laser device according to the present invention, the form in which the optical fiber 3 is used as the optical waveguide including the gain medium has been described. However, the optical waveguide including the gain medium is not limited to the optical fiber 3. The optical waveguide including the gain medium can be, for example, a semiconductor laser. By using a semiconductor laser as an optical waveguide including a gain medium, an external resonant semiconductor laser capable of changing the wavelength can be configured. When configuring an external resonant semiconductor laser, a semiconductor laser that emits laser light in a wavelength range wider than a single wavelength is used, and the reflected light from the output mirror 4 is fed back into the internal resonator of the semiconductor laser. In this case, the second resonance element (dielectric multilayer film 8) can be omitted.

In the laser resonator device and the laser device according to the embodiment of the present invention, the form in which the dielectric multilayer film 8 is used as the second resonator element has been described. However, the second resonator element is not limited to the dielectric multilayer film 8. The second resonant element may be a dielectric mirror. The dielectric mirror is a mirror on which a dielectric multilayer film is formed. The dielectric mirror is preferably in close contact with the incident end of the optical fiber 3 in order to prevent light leakage from the incident end of the optical fiber 3.

[Fifth Embodiment]
Next, an embodiment of a variable bandpass filter device according to the present invention will be described. FIG. 11 is a diagram illustrating a configuration of the variable bandpass filter device 30 according to the present embodiment. The variable band-pass filter device 30 can change the wavelength of light transmitted through the first optical fiber 31 (an example of the first optical waveguide) using axial chromatic aberration that a lens generally has.

As shown in FIG. 11, the variable bandpass filter device 30 includes an optical system 2, a drive device 5, a first optical fiber 31, and one end portion (end portion on the incident end side) of the first optical fiber 31. And a supporting member 32 for supporting.

In the present embodiment, the optical system 2 and the incident end of the first optical fiber 31 are arranged in this order along the optical axis A of the light 34 emitted from the emission end (right end in FIG. 11) of the second optical fiber 33. . The second optical fiber 33 includes a core part 33a and a clad part 33b. Light 34 having a wavelength range wider than a single wavelength is incident on the incident end (left end in FIG. 11) of the second optical fiber 33. The second optical fiber 33 transmits the light 34 and emits the light 34 from the emission end toward the optical system 2 (first condenser lens 2a).

The first optical fiber 31 includes a core part 31a and a clad part 31b. The incident end of the first optical fiber 31 is irradiated with light 34 condensed by the optical system 2 (second condenser lens 2b).

The support member 32 is fixed to the driving device 5. The drive device 5 changes the position of the incident end of the first optical fiber 31 along the optical axis A by changing the position of the support member 32 along the optical axis A.

According to this embodiment, the wavelength of light transmitted through the first optical fiber 31 can be changed by changing the position of the incident end of the first optical fiber 31 along the optical axis A.

That is, as described in the first embodiment, the position (focal position) at which light is collected by the second condenser lens 2b is different for each wavelength of light due to axial chromatic aberration. Therefore, the wavelength of the light transmitted through the first optical fiber 31 can be changed by changing the position of the incident end of the first optical fiber 31 between the focal positions at the respective wavelengths. That is, only light having a wavelength corresponding to the position of the incident end of the first optical fiber 31 is condensed on the core portion 31a of the first optical fiber 31 by the second condenser lens 2b. Therefore, when the position of the incident end of the first optical fiber 31 coincides with the focal position of light having a certain wavelength, only that light is incident on the core portion 31a of the first optical fiber 31 and is transmitted through the first optical fiber 31. .

In addition, the core part 31a of the first optical fiber 31 may include a gain medium. Therefore, the first optical fiber 31 may be the optical fiber 3 described in the first embodiment. Further, the variable bandpass filter device 30 may include a second optical fiber 33 (an example of a second optical waveguide). In this case, the core part 33a of the second optical fiber 33 may include a gain medium. Therefore, the second optical fiber 33 can be the optical fiber 3 described in the first embodiment. The variable bandpass filter device 30 may include a semiconductor laser that emits laser light in a wavelength range wider than a single wavelength as the second optical waveguide.

The embodiment of the variable bandpass filter device according to the present invention has been described above with reference to the drawings. However, the variable band-pass filter device according to the present invention is not limited to the above-described embodiment, and can be implemented in various modes without departing from the gist thereof.

For example, in the embodiments of the variable bandpass filter device according to the present invention, the first optical waveguide is an optical fiber (optical fiber 31), but the first optical waveguide is not limited to an optical fiber. The first optical waveguide can be, for example, a semiconductor optical waveguide. Similarly, the mode in which the second optical waveguide that does not include the gain medium is an optical fiber (the optical fiber 33 that does not include the gain medium) has been described. However, the second optical waveguide that does not include the gain medium is not limited to the optical fiber. The second optical waveguide that does not include the gain medium may be, for example, a semiconductor optical waveguide.

The embodiments of the laser resonator device, the laser device, and the variable band-pass filter device according to the present invention have been described above, but the items described in the embodiments of the present invention can be combined as appropriate.

For example, in the laser resonator 1 of the fourth embodiment described with reference to FIG. 10, the first optical system 2 includes two condenser lenses 2a and 2b as optical elements, but the present invention is not limited to this. Not. In the laser resonator 1 of the fourth embodiment, the first optical system 2 may include a single gradient index lens 2c as described in the second embodiment.

Further, for example, in the variable bandpass filter device 30 of the fifth embodiment described with reference to FIG. 11, the drive device 5 changes the position of the incident end of the first optical fiber 31, but the present invention is not limited to this. Not. In the variable bandpass filter device 30 of the fifth embodiment, the drive device 5 is the one closer to the incident end of the first optical fiber 31 of the two condenser lenses 2a and 2b, as described in the third embodiment. The position of the condenser lens 2b may be changed along the optical axis A.

Hereinafter, examples of the present invention will be described. However, the present invention is not limited to the following examples.

In this example, the configuration of the laser apparatus 10 shown in FIG. 4 was used. As the excitation light source 11, a gallium nitride semiconductor laser (manufactured by Nichia Chemical Co., Ltd., product name: NDB7875E, production number: BA2898) is used. -Continuous wave) was emitted. The wavelength of the excitation light 7 (blue) was 442 nm and the output was 1.6 W. Further, as the second optical system 12, an optical fiber manufactured by Sumita Optical Glass Co., Ltd. was used.

For the optical fiber 3, Pr: WPFGF having a fiber length L3 of 40 mm was used. The diameter D1 of the core part 3a was 8 μm, and the diameter D2 of the optical fiber 3 (cladding part 3b) was 300 μm. Praseodymium (Pr ³⁺ ) was added at 3000 ppm. The dielectric multilayer film 8 had a reflectance of 99% to 99.5% with respect to a wavelength of 550 μm to 650 μm and a transmittance of 90% to 95% with respect to a wavelength of 400 μm to 480 μm.

An aspherical lens (manufactured by Edmund Optics, serial number: # 49104, NA: 0.33, focal length f: 37.5 mm) was used for each condenser lens 2a, 2b. The distance from the output end of the optical fiber 3 to the first condenser lens 2a is set to 37.5 mm, the distance between the pair of condenser lenses 2a and 2b is set to 76 mm, and the output mirror 4 from the second condenser lens 2b. The distance to the initial setting position was set to 37.5 mm.

The output mirror 4 used was a “short pass filter (manufacturing number: # 64603)” manufactured by Edmund Optics. The output mirror 4 had a reflectance of 90% to 99.5% for wavelengths of 550 μm to 650 μm and a transmittance of 0.5% to 10% for wavelengths of 550 μm to 650 μm.

The output mirror 4 is shifted along the optical axis A in a direction away from the second condenser lens 2b by 10 μm from the initial setting position, and the wavelength (oscillation spectrum) of the laser light 6 transmitted through the output mirror 4 is changed to an optical spectrum analyzer. (Measured by Ocean Optics, product name: HR2000). The measurement results are shown in FIGS.

12 to 25 show oscillation spectra measured by shifting the output mirror 4 by 10 μm from the initial setting position (location 37.5 mm away from the second condenser lens 2b), respectively. 12 to 25, the horizontal axis indicates the wavelength (oscillation spectrum) of the laser light 6. FIG. The vertical axis indicates the intensity of the laser beam 6. In this embodiment, the laser beam 6 is a continuous wave.

FIG. 12 shows an oscillation spectrum obtained when the output mirror 4 is located at the initial setting position. As shown in FIG. 12, when the output mirror 4 is located at the initial setting position, the peak wavelength is about 603.5 nm.

FIG. 13 shows an oscillation spectrum obtained when the output mirror 4 is shifted by 10 μm from the initial setting position. As shown in FIG. 13, when the output mirror 4 is shifted by 10 μm from the initial setting position, the peak wavelength is about 603.7 nm.

FIG. 14 shows an oscillation spectrum obtained when the output mirror 4 is shifted 20 μm from the initial setting position. As shown in FIG. 14, when the output mirror 4 is shifted by 20 μm from the initial setting position, the peak wavelength is about 604.8 nm.

FIG. 15 shows an oscillation spectrum obtained when the output mirror 4 is shifted by 30 μm from the initial setting position. As shown in FIG. 15, when the output mirror 4 was shifted by 30 μm from the initial setting position, two peak wavelengths were observed. Specifically, a peak wavelength of about 605.5 nm and a peak wavelength of about 606.3 nm were observed. This is because the shift width of the focal position due to the axial chromatic aberration of the second condenser lens 2b with respect to the light having the wavelength of about 605.5 nm and the light having the wavelength of about 606.3 nm is small, and the wavelength of about 605.5 nm. This is considered to be because both of the light and the light having a wavelength of about 606.3 nm have returned to the core portion 3 a of the optical fiber 3.

FIG. 16 shows an oscillation spectrum obtained when the output mirror 4 is shifted by 40 μm from the initial setting position. As shown in FIG. 16, when the output mirror 4 was shifted by 40 μm from the initial setting position, the peak wavelength was about 607.6 nm.

FIG. 17 shows an oscillation spectrum obtained when the output mirror 4 is shifted by 50 μm from the initial setting position. As shown in FIG. 17, when the output mirror 4 is shifted by 50 μm from the initial setting position, the peak wavelength is about 609.3 nm.

FIG. 18 shows an oscillation spectrum obtained when the output mirror 4 is shifted by 60 μm from the initial setting position. As shown in FIG. 18, when the output mirror 4 was shifted by 60 μm from the initial setting position, two peak wavelengths were observed. Specifically, a peak wavelength of about 610.7 nm and a peak wavelength of about 611.9 nm were observed. This is because the shift width of the focal position due to the axial chromatic aberration of the second condenser lens 2b with respect to the light having the wavelength of about 610.7 nm and the light having the wavelength of about 611.9 nm is small, and the wavelength of about 610.7 nm. This is considered to be because both of the light and the light having a wavelength of about 611.9 nm have returned to the core portion 3 a of the optical fiber 3.

FIG. 19 shows an oscillation spectrum obtained when the output mirror 4 is shifted by 70 μm from the initial setting position. As shown in FIG. 19, when the output mirror 4 is shifted by 70 μm from the initial setting position, the peak wavelength is about 613.1 nm.

FIG. 20 shows an oscillation spectrum obtained when the output mirror 4 is shifted by 80 μm from the initial setting position. As shown in FIG. 20, when the output mirror 4 is shifted by 80 μm from the initial setting position, the peak wavelength is about 614.4 nm.

FIG. 21 shows an oscillation spectrum obtained when the output mirror 4 is shifted by 90 μm from the initial setting position. As shown in FIG. 21, when the output mirror 4 is shifted by 90 μm from the initial setting position, the peak wavelength is about 616.8 nm.

FIG. 22 shows an oscillation spectrum obtained when the output mirror 4 is shifted by 100 μm from the initial setting position. As shown in FIG. 22, when the output mirror 4 is shifted by 100 μm from the initial setting position, the peak wavelength is about 619.1 nm.

FIG. 23 shows an oscillation spectrum obtained when the output mirror 4 is shifted 110 μm from the initial setting position. As shown in FIG. 23, when the output mirror 4 is shifted from the initial setting position by 110 μm, the peak wavelength is about 620.2 nm.

FIG. 24 shows an oscillation spectrum obtained when the output mirror 4 is shifted by 120 μm from the initial setting position. As shown in FIG. 24, when the output mirror 4 is shifted by 120 μm from the initial setting position, the peak wavelength is about 622.1 nm.

FIG. 25 shows an oscillation spectrum obtained when the output mirror 4 is shifted by 130 μm from the initial setting position. As shown in FIG. 25, when the output mirror 4 is shifted by 130 μm from the initial setting position, the peak wavelength is about 624.7 nm.

Therefore, as shown in FIGS. 12 to 25, by setting the movement range (maximum movement distance) of the output mirror 4 to 130 μm, a wavelength variable characteristic of 20 nm or more could be obtained.

The laser resonance apparatus and laser apparatus of the present invention can be applied to medical lasers. Specifically, it can be used as a light source for a laser knife, a light source for photodynamic therapy, a light source for OCT (Optical Coherence Tomography), and the like. Further, the laser resonance apparatus and laser apparatus of the present invention can be applied to a measurement laser. Specifically, it can be used for a light source of LIDAR (Laser Detection and Ranging), a light source of an atmospheric remote sensor, and the like. Further, the laser resonance apparatus and laser apparatus of the present invention can be applied to a laser for measuring fine particles. Specifically, it can be used as a light source for Raman spectroscopy, a light source for flow cytometry, and the like. The laser resonance apparatus and laser apparatus of the present invention can be used as a light source for measuring physical properties such as solar cells. Moreover, the laser resonance apparatus and laser apparatus of the present invention can be used as a light source for optical communication.

DESCRIPTION OF SYMBOLS 1 Laser resonance apparatus 2 1st optical system 2a Condensing lens 2b Condensing lens 2c Refractive index distribution type lens 3 Optical fiber 3a Core part 3b Clad part 4 Output mirror 4a Incident surface 5 Drive apparatus 6 Laser light 7 Excitation light 8 Dielectric multilayer Film 10 Laser device 30 Variable bandpass filter device A Optical axis

Claims (15)

1. An optical system that focuses light on the optical axis;
   An optical waveguide including a gain medium that emits light in a wavelength range wider than a single wavelength, and the light emitted from the gain medium is incident on the optical system;
   A first resonant element having an incident surface that reflects a portion of the light collected by the optical system;
   A drive device that changes the position of the incident surface or the position of the optical element constituting the optical system along the optical axis;
   A laser resonance apparatus in which laser light oscillates when light having a wavelength corresponding to the position of the incident surface or the position of the optical element returns from the first resonance element to the optical waveguide through the optical system. .
2. The optical system includes two condenser lenses as the optical element,
   2. The laser resonance apparatus according to claim 1, wherein the driving device changes a position of the incident surface or a position of the condenser lens closer to the first resonance element of the two condenser lenses. .
3. The optical system includes a single gradient index lens as the optical element,
   The laser resonator according to claim 1, wherein the driving device changes a position of the incident surface or a position of the gradient index lens.
4. The laser resonator according to any one of claims 1 to 3, wherein the first resonance element has a saturable absorption characteristic.
5. A second resonant element that transmits the excitation light and reflects the light emitted by the gain medium;
   The optical waveguide is an optical fiber;
   The optical fiber includes an incident end on which the excitation light is incident,
   The second resonance element is provided at the incident end,
   The laser resonator according to any one of claims 1 to 4, wherein the gain medium is contained in a core portion of the optical fiber.
6. 6. The laser resonance apparatus according to claim 1, wherein the gain medium includes an ionized rare earth element, an ionized transition element, or bismuth.
7. The rare earth element is cerium, praseodymium, neodymium, samarium, europium, ytterbium, erbium, or thulium;
   The laser resonator according to claim 6, wherein the transition element is copper or tin.
8. The laser resonator according to claim 5, wherein the optical fiber includes fluoride glass.
9. 9. The laser resonator according to claim 8, wherein the gain medium includes ionized praseodymium.
10. 6. The laser resonator according to claim 5, wherein the core portion includes an ionized rare earth element, an ionized transition element, or quartz glass to which bismuth is added using zeolite.
11. The gain medium comprises ionized neodymium or ytterbium;
    The laser resonator according to claim 10, wherein a length of the optical fiber is 1 mm or more.
12. The laser resonator device according to any one of claims 1 to 4, wherein the optical waveguide is a semiconductor laser.
13. A laser resonator according to any one of claims 1 to 11,
    A laser apparatus comprising: an excitation light source that generates excitation light incident on the optical waveguide.
14. An optical system that focuses light on the optical axis;
    A first optical waveguide having an incident end irradiated with light condensed by the optical system;
    A drive device for changing a position of an incident end of the first optical waveguide or a position of an optical element constituting the optical system along the optical axis;
    A variable band in which light having a wavelength corresponding to the position of the incident end of the first optical waveguide or the position of the optical element is incident on the inside of the first optical waveguide from the incident end of the first optical waveguide. Pass filter device.
15. A second optical waveguide that emits light toward the optical system;
    The variable band-pass filter device according to claim 14, wherein at least one of the first optical waveguide and the second optical waveguide includes a gain medium.

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