JP2010080927A - Laser device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser deice for generating laser in a UV or visible light region by directly exciting an upper level. <P>SOLUTION: The laser device includes an exciting light source, and a resonator on which a first mirror for transmitting exciting light emitted from the exciting light source and reflecting light in a desired wavelength range excluding the wavelength of the excited light and a second mirror for reflecting light in a desired wavelength range are provided opposing each other, and which has a laser medium arranged between light paths of the first mirror and the second mirror for emitting light with the exciting light. The exciting light source is a gallium nitride semiconductor light source whose exciting light has a wavelength of 340-500 nm, and the laser medium is fluoride glass or a fluoride crystal to which at least one of Er<SP>3+</SP>, Ho<SP>3+</SP>, Sm<SP>3+</SP>, Tm<SP>3+</SP>, Dy<SP>3+</SP>, Eu<SP>3+</SP>, Tb<SP>3+</SP>, and Nd<SP>3+</SP>is added. A laser oscillation wavelength is longer than an excitation wavelength. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an apparatus for generating a laser having a short wavelength such as UV light or visible light.

  At present, lasers are used in many fields such as processing, communication, and measurement. Recently, with the progress of optical technology, lasers with shorter wavelengths such as UV and visible wavelengths are required. In particular, in the fields of semiconductor manufacturing, fluorescent microscope field, medical and biotechnology, lasers with UV to visible wavelengths are becoming indispensable.

  However, most existing high-power lasers are particularly in the near-infrared to infrared wavelength region, for example, Ti: Sapphire laser (650 nm to 1100 nm), Nd: YAG laser (1064 nm), semiconductor laser (wavelength 808 nm, 915 nm, 960 nm, 970 to 980 nm, etc.).

  There are few semiconductor lasers that directly emit light in the visible wavelength region, and there are only limited semiconductor lasers such as 380 to 500 nm, red semiconductor 635 nm, and 650 nm bands using a gallium nitride semiconductor light source. Other than these wavelengths, most visible lasers that are currently available are obtained by wavelength conversion of the high-power near-infrared laser (Non-Patent Document 1).

  For wavelength conversion, a wavelength conversion device such as a nonlinear optical crystal (BBO crystal, LBO crystal, etc.) or a polarization inversion element (PPLN, etc.) is used.

  However, when a nonlinear optical crystal is used, high-efficiency wavelength conversion cannot be obtained because the traveling directions of the fundamental wave and the harmonic wave are different (so-called walk-off). Even when a polarization reversal element is used, a loss due to non-uniformity of the periodic structure of the polarization reversal or a change in element temperature always occurs. As can be seen from the above, when a laser with a visible wavelength that does not exist is generated by wavelength conversion, a near-infrared laser as a fundamental wave is newly produced, and a nonlinear optical crystal or a polarization inversion element is newly designed. However, it is necessary to accurately adjust the temperature of the wavelength conversion device, which is extremely difficult.

  As another means for obtaining a visible light laser, there is a method using an upconversion phenomenon. This method is a method of obtaining light having a shorter wavelength by causing the rare earth ions to absorb excitation light having a wavelength longer than the desired emission wavelength in multiple stages (Non-Patent Document 2). However, since light emission by up-conversion requires a multi-step absorption process, the electronic state transitions from an intermediate level to a level other than the desired level, so the excitation energy is lost accordingly. End up.

One means for obtaining highly efficient laser oscillation is to directly excite the upper level or higher of the laser oscillation. Recently, a Pr ³⁺ doped fluoride fiber laser (laser oscillation wavelength: 635 nm) using a 445 nm wavelength gallium nitride semiconductor laser as an excitation light source has been proposed (Non-patent Document 3). The wavelength around 445 nm is exactly the same as the Pr ³⁺ ion absorption band, and the laser oscillation in the 635 nm band is a four-level laser oscillation, so there is no ground level absorption (GSA) and laser oscillation is easy. Can be made. However, in other rare earths, it is difficult to excite the upper level directly with a semiconductor laser to cause laser oscillation, and there has been no report so far.

  In Non-Patent Document 3, an anamorphic prism pair is used when shaping the beam shape of a gallium nitride based semiconductor laser. In an optical system using an anamorphic prism pair, astigmatism occurs because the optical axis is shifted by the prism. In particular, when the excitation light is condensed on an optical waveguide or the like, this astigmatism deteriorates the coupling efficiency.

  Further, as a gallium nitride semiconductor light source, in addition to a gallium nitride (GaN) semiconductor, an aluminum gallium nitride (GaAlN) semiconductor to which aluminum is added, and an indium gallium nitride (GaInN) semiconductor to which indium is added Is known, and the band gap of gallium nitride (GaN) is 360 nm. When In (indium) is added, the emission wavelength shifts to the longer wavelength side, and when Al (aluminum) is added, the emission wavelength is It is known to shift to the short wavelength side (Non-Patent Document 4).

Klaus Schneider, Stephen Schiller, Jurgen Mlynek, Markus Board, and Ingo Freitag, ‘1.1-W single-frequency 532 nm radiation by second-harmoned 21 Issue 24, pp. 1999-2001 (1996) Whitley, T.W. J. et al. , Millar, C .; A. , Wyatt, R .; Brierley, M .; C. Szebesta, D .; : ‘Upconversion pumped green lasing in erbium doped fluorozirconate fibre’, Electronics Letters, Volume 27, Issue 20, pp 1785-1786. WEICHMANN, U. , BAIER, J .; , BENGECHEA, J.A. , And MOENCH, H.M. : 'GaN-diode pumped Pr3 +: ZBLAN fiber-lasers for the visible waverange range', Proc. CLEO / Europe-IQEC, European Conference on. , Munich, Germany, 2007 Vurgaftman, I. et al. Meyer, J .; R. ‘Band parameters for nitrogen-continging semiconductors’ J. Appl. Phys. 94, 3675 (2003)

  As described above, when the emission wavelength of the laser medium is not in a desired wavelength band (UV or visible region), it is necessary to always use wavelength conversion means with loss for existing lasers in different wavelength bands. It goes without saying that there are laser wavelength bands that cannot be obtained even if the existing laser wavelength and wavelength conversion device are combined.

  Even when light emission in a desired wavelength band (UV or visible region) is obtained using the up-conversion phenomenon, some excitation energy is lost during a plurality of excitation processes, which is not efficient.

Since there is no GSA, in the laser using Pr ³⁺ that can oscillate the laser, a method of directly exciting the upper level using a gallium nitride semiconductor laser has been reported, but anamorphic is reported. Astigmatism occurs due to the use of the prism pair, and the coupling efficiency deteriorates. Further, other rare earths have not been reported to directly excite the upper level for laser oscillation, and laser devices in the UV and visible wavelength regions are limited.

  An object of the present invention is to provide a laser device capable of generating a laser in the UV light or visible light region by directly exciting the upper level without using wavelength conversion means and up-conversion phenomenon. .

  As a result of intensive studies, the present inventors have found that lasers in the UV light / visible light region can be configured using various rare earth elements without using wavelength conversion means and up-conversion phenomenon. It has come.

That is, the present invention provides an excitation light source, a first mirror that transmits excitation light emitted from the excitation light source and reflects light in a desired wavelength band excluding the wavelength of the excitation light, and light in the desired wavelength band. An excitation light source in a laser device comprising a resonator in which a second mirror to be reflected is disposed opposite to each other and a laser medium that emits light by the excitation light is disposed between the optical paths of the first mirror and the second mirror In addition, a gallium nitride semiconductor light source having a wavelength of excitation light in the range of 340 nm to 500 nm, a laser medium, at least Er ³⁺ , Ho ³⁺ , Sm ³⁺ , Tm ³⁺ , Dy ³⁺ , Eu ³⁺ , Tb ³ , or one kind is using an addition has been and fluoride glass or fluoride crystal of Nd ^3+, and provide a laser apparatus, wherein a laser oscillation wavelength is longer than the excitation wavelength Is shall.

  Furthermore, at least one optical waveguide that becomes a single mode in the desired wavelength band is inserted in the optical path of the resonator, and the laser medium is a core portion of the optical waveguide The present invention provides a laser device characterized in that an optical waveguide made of silica glass is connected to one or both ends of the laser medium.

  According to the present invention, laser oscillation in the UV light or visible light region can be obtained with high efficiency.

2 shows an example of an embodiment according to the present invention. 2 shows an example of an embodiment according to the present invention. 1 shows a first embodiment of the present invention. 2 shows an oscillation spectrum according to the first embodiment of the present invention. The output characteristic by 1st Example of this invention is shown. 2 shows a second embodiment of the present invention. 3 shows a third embodiment of the present invention.

  An example of an embodiment of the present invention is shown using FIG. 1 includes an excitation light source 101, a condenser lens 102, an excitation light transmission / laser light reflection filter 103, a rare earth-added fluoride glass fiber 104, and a laser light partial reflection mirror 105. Excitation light emitted from the excitation light source 101 is collected by the condenser lens 102 and coupled to the end face 104-a of the rare earth-added fluoride glass fiber 104. The fiber end 104-a on the excitation side is ground at a right angle and is in close contact with the excitation light transmission / laser light reflection filter 103 without a gap. The output-side fiber end 104-b is also ground at a right angle and is in close contact with the laser beam partial reflection mirror 105 without any gap.

  The excitation light coupled to the rare earth-added fluoride glass fiber 104 is absorbed while propagating through the rare earth-added fluoride glass fiber 104, and emits spontaneous emission light (ASE light). The ASE light is converted into laser light by reciprocating in the resonator constituted by the excitation light transmission / laser light reflection filter 103 and the laser light partial reflection mirror 105, and a part thereof is transmitted through the laser light partial reflection mirror 105 and output. The

  The condenser lens 102 and the excitation light transmission / laser light reflection filter 103 are preferably AR-coated at the wavelength of the excitation light. The reflectance of the laser beam partial reflection mirror 105 is desirably determined so that the laser beam transmitted through the mirror 105 is maximized.

  When an air layer is formed on the close contact surface between the fiber end face (104-a or 104-b) and the excitation light transmitting / laser light reflecting filter 103 or the laser light partial reflection mirror 105, the difference in refractive index between the core of the fiber end face and air. As a result, Fresnel reflection due to the laser beam may occur and laser oscillation may occur outside the desired wavelength band. Therefore, the polished surface of the fiber end to be in close contact with the excitation light transmission / laser light reflection filter 103 or the laser light partial reflection mirror 105 is , Preferably perpendicular to the optical axis of the fiber.

  In order to suppress laser oscillation outside the desired wavelength band due to the Fresnel reflection, the configuration shown in FIG. 2 can be adopted. 2, in addition to the configuration of FIG. 1, a collimator lens 201 is disposed between the rare earth-added fluoride glass fiber 104 and the laser beam partial reflection mirror 105. Further, the rare earth-doped fluoride glass fiber end 104-b opposite to the excitation side is obliquely polished to 8 ° or more in order to suppress the return light due to Fresnel reflection, and the collimating lens 201 is emitted from the rare earth-doped fluoride glass fiber 104. Anti-reflective coating is applied to the belt. Thereby, since the Fresnel reflection which generate | occur | produces in the rare earth addition fluoride glass fiber end 104-b opposite to the excitation side can be suppressed, laser oscillations other than a desired wavelength band can be suppressed. The Fresnel reflection suppressing means as described above can also be implemented at the fiber end 104-a on the excitation side.

  Further, in FIG. 2, instead of the collimating lens 201 and the laser beam partial reflection mirror 105, the concave surface side of the concave laser beam partial reflection mirror is disposed toward the rare earth-added fluoride glass fiber end surface 104-b, thereby providing a rare earth element. The ASE light emitted from the doped fluoride glass fiber end face 104-b can also be reflected and coupled again to the fiber end face 104-b. Even when the concave laser beam partial reflection mirror is used, the generated ASE light is reciprocated through a resonator constituted by the excitation light transmission / laser light reflection filter 103 and the concave laser beam partial reflection mirror. It becomes light and is transmitted through a partially reflecting laser beam partially reflecting mirror.

  Alternatively, in FIG. 1, instead of bringing the excitation light transmission / laser light reflection filter 103 into contact with the fiber end face, a coating having the same function may be applied directly on the fiber end face 104-a. Further, instead of bringing the laser beam partial reflection mirror 105 into contact with the fiber end surface, a coating having the same function may be applied directly on the fiber end surface 104-b.

  Although the rare earth-added fluoride glass fiber 104 is used as an example of the laser medium, the laser medium disposed at the position of the fiber 104 does not have to be a fiber shape, and the rare earth-added fluoride bulk glass or rare earth-added fluoride fiber is not necessary. Fluoride bulk crystals, or rare earth doped fluoride optical waveguides that are not in fiber form can also be used. Furthermore, an optical waveguide made of quartz glass can be connected to both ends or one end of the laser medium.

Rare earth elements to be added to the laser medium, the oscillation wavelength of the excitation light source but may be a rare earth element that absorbs light is any wavelength in the range of 340Nm～500nm, ^{particularly,} Er ^{3+, Ho} 3+, Sm ³⁺ , Tm ³⁺ , Dy ³⁺ , Eu ³⁺ , Tb ³⁺ and Nd ³⁺ are preferable.

For example, when the rare earth element added to the core is Er ³⁺ , excitation light having an oscillation wavelength in the range of 355 nm to 390 nm, 400 nm to 415 nm nm, 438 nm to 460 nm, or 477 nm to 497 nm can be used. ^{With 3+} , it is possible to use excitation light having an oscillation wavelength in a range of 340 nm to 370 nm, 380 nm to 390 nm, 410 nm to 420 nm, or 440 nm to 495 nm. With Sm ³⁺ , an oscillation wavelength of 355 nm to 380 nm, 390 nm to 390 nm to Excitation light having a wavelength in the range of 410 nm, 455 nm to 490 nm can be used. In Tm ³⁺ , excitation light having an oscillation wavelength in the range of 345 nm to 365 nm, 455 nm to 485 nm can be used, and Dy ³⁺ Then, the oscillation wavelength is 3 0Nm, can be used an excitation light within any range 440Nm～460nm, the ^{Eu 3+,} can be used excitation light emission wavelength is within any range of 390Nm～400nm, In Tb ³⁺ , an excitation light having an oscillation wavelength in any range of 340 nm to 385 nm and 475 nm to 495 nm can be used. In Nd ³⁺ , the oscillation wavelength is 340 nm to 360 nm, 425 nm to 435 nm, 445 nm to 485 nm, and 490 nm. Excitation light in the range of ~ 500 nm can be used.

  In order to efficiently use excitation light for excitation of rare earth elements to which the excitation light is added, a material having low phonon energy is preferable as the host glass of the laser medium. Therefore, fluoride glass or fluoride crystal is used as the laser medium. Is used. When quartz glass, which has a higher phonon energy than fluoride glass, is used for the core of the optical waveguide of the amplification section, the non-radiative relaxation rate is fast. Since the ratio of returning to the ground state increases, the efficiency is poor.

  The excitation light source is not particularly limited as long as the oscillation wavelength has one or more wavelengths selected from the range of 340 nm to 500 nm.

  For example, a gallium nitride semiconductor light source, a He—Cd laser, a dye laser, an Ar ion laser, a wavelength conversion laser, or the like can be used.

  However, in consideration of size and power consumption, a wavelength conversion laser or a gallium nitride semiconductor light source which is a small light source with low power consumption is preferable. Further, when attention is paid to the electrical / optical conversion efficiency, the wavelength conversion laser causes a loss when converting the wavelength of the fundamental laser, and therefore, a gallium nitride based semiconductor light source that can directly emit light having a wavelength in the vicinity of 340 nm to 500 nm is more preferable. .

  In particular, when using a gallium nitride based semiconductor laser in a gallium nitride based semiconductor light source, the emitted beam has an elliptical shape, so that the laser medium has an optical waveguide such as an optical fiber having a circular core. It is preferable to perform shaping of a beam that is transformed into a circular beam. For example, it is more desirable to use excitation light obtained by shaping a beam using a cylindrical lens.

  When a laser medium of an optical waveguide is used and an optical waveguide made of silica glass is connected to one side or both sides of the laser medium, the waveguide parameter of the optical waveguide is the connection between the waveguides to be connected. It is preferable to set the loss to be 0.2 dB or less. When the waveguide parameters are greatly different, not only loss occurs at the connection portion, but reflection due to structural mismatch may occur. More preferably, in order to suppress reflection at the connection portion, it is preferable to use fusion splicing.

  Furthermore, connecting an optical waveguide made of silica glass to the laser medium of the optical waveguide also has an effect of preventing the excitation light incident end of the laser medium from being damaged for the following reasons. When the shape of the excitation light is not a complete single mode, a part of the light is emitted outside the core of the optical waveguide when the excitation light is incident on the optical waveguide. In addition, in the end face of the optical waveguide on the excitation light incident side, if there are scratches or structural irregularities in the vicinity of the core, heat may be generated due to electric field concentration. In particular, caution is required for fluoride glass having a low glass transition temperature (about 280 ° C. for ZBLAN glass). In order to protect the end face of the laser medium, for example, in the example shown in FIG. 1, a silica-based fiber can be fusion-bonded to the end face 104-a of the rare earth-doped fluoride glass fiber on the excitation side. Since quartz glass has a higher glass transition temperature than fluoride glass, it has high resistance to heat generation.

  In addition, when the desired laser beam reciprocating in the resonator is oscillating in a multimode, a single mode optical waveguide is inserted into the optical path of the resonator by a single mode in the desired wavelength band. It is also possible to cause laser oscillation in a single mode selectively by giving loss to other components.

  In addition, the optical waveguide made of silica-based glass to be used may have a core portion of silica-based glass, but is preferably one having little absorption in the ultraviolet light to visible light region. In particular, when performing laser oscillation in the ultraviolet to blue-violet region, quartz glass to which Ge having absorption from ultraviolet to blue-violet is highly added is not preferable as the core material of the optical waveguide. For example, pure quartz glass should be used. Is preferred.

  Specific examples using the present invention are disclosed below.

FIG. 3 shows a first embodiment. The optical system shown in FIG. 3 includes a gallium nitride semiconductor laser 401 (with indium added, center wavelength 448 nm: manufactured by Nichia Corporation), an aspherical lens 402 (NA: 0.60), and a cylindrical lens as an excitation light source. 403 (f = -25 mm), cylindrical lens 404 (f = 50 mm), aspherical lens 405 (NA: 0.30), filter 406 (AR: 448 nm, HR: 470-570 nm), Er ^{3+ as} a laser medium added Fluoride glass fiber 407 (host glass: ZBLAN glass, Er ³⁺ : 3000 ppm, NA: 0.22, core diameter: 3.3 μm, fiber length: 65 cm), aspheric lens 408 (NA: 0.55), mirror 409 (Wavelength: 543 ± 10 nm, reflectivity: 76%, other wavelengths are transmitted) .

The optical components (402, 403, 404, 405, 406) through which the excitation light passes are anti-reflection coated at a wavelength of 448 nm. The optical component 408 through which the laser beam is transmitted has an antireflection coating at wavelengths of 500 nm to 600 nm, 820 nm to 880 nm, and 1500 nm to 1580 nm. Er ³⁺ doped fluoride glass fiber end face 407-a is polished perpendicularly, it was adhered without a gap to the filter 406. The Er ^{3 +} -added fluoride glass fiber end face 407-b was polished 8 ° in order to suppress Fresnel reflection. The light transmitted through the mirror 409 was coupled to a measurement fiber (core diameter: 62.5 μm, multimode GI fiber), and the wavelength spectrum thereof was measured using an optical spectrum analyzer (manufactured by ANDO: AQ-6315A).

As a result, when excitation light of 120 mW or more was applied, laser oscillation was confirmed in the wavelength 543 nm band. FIG. 4 shows the wavelength spectrum of the laser light output from the laser resonator when the excitation light 176 mW is coupled to the Er ^{3 +} -added fluoride glass fiber 407.

  Further, the optical power included in the transmitted light at a wavelength of 543 ± 10 nm was measured using a bandpass filter (transmitted wavelength: 543 ± 10 nm) and a power meter head (manufactured by Anritsu: MA9411A). FIG. 5 shows the relationship between the pumping light power input to the fiber and the obtained laser output. When excitation light of a maximum of 200 mW was input to the fiber, a laser output of a maximum of 12 mW was obtained.

FIG. 6 shows a second embodiment. The optical system shown in FIG. 6 includes a gallium nitride semiconductor laser 701 as an excitation light source (with indium added, center wavelength 448 nm: manufactured by Nichia Corporation), an aspherical lens 702 (NA: 0.60), and a cylindrical lens. 703 (f = −25 mm), cylindrical lens 704 (f = 50 mm), aspherical lens 705 (NA: 0.30), filter 706 (AR: 448 nm, HR: 470-570 nm), Er ³⁺ added as a laser medium Fluoride glass fiber 707 (host glass: ZBLAN glass, Er ³⁺ : 3000 ppm, NA: 0.22, core diameter: 3.3 μm, fiber length: 65 cm), quartz fiber 709 (Nufern 460HP, fiber length: 1 m, wavelength) Single mode at 543 nm), aspherical lens 710 (NA: 0) .55), mirror 711 (wavelength: 543 ± 10 nm, reflectance: 82%, other wavelengths are transmitted). Optical components (702, 703, 704, 705, 706) through which the excitation light passes are AR-coated at a wavelength of 448 nm. The optical component 710 through which the laser beam is transmitted has an antireflection coating at wavelengths of 520 nm to 560 nm, 830 nm to 870 nm, and 1510 nm to 1570 nm. The Er ^{3 +} -added fluoride glass fiber end face 707-a was polished at a right angle and was brought into close contact with the filter 706 without any gap. The Er ^{3 +} -added fluoride glass fiber 707 and the quartz fiber 709 are fusion spliced (fusion splicing portion 708).

The Er ^{3 +} -added fluoride glass fiber 707 that is a laser medium is desirably single mode at a desired laser wavelength (543 nm in this embodiment), but it is not necessary. In general, the emitter size of a high-power gallium nitride semiconductor light source (the emitter size of the excitation light source used this time is about 1 μm × 7 μm) is larger than the core size of a single mode fiber operating at visible wavelengths (approximately 3 μm) . Therefore, when it is desired to introduce more excitation light into the fiber core, it is more preferable to set the core diameter slightly larger.

In this embodiment, in order to use more excitation light, a rare-earth doped fiber that becomes a multimode at a desired wavelength of 543 nm is used. Further, in order to convert the laser light of 543 nm to a single mode, a single mode is used at a wavelength of 543 nm. A quartz fiber 709 is introduced. Preferably, the single mode fiber is disposed between the Er ³⁺ doped fluoride glass fiber 707 and the mirror 711 so as not to hinder the propagation of the excitation light.

When the excitation power is increased while monitoring the laser beam obtained through the partial reflection mirror 711 with an optical spectrum analyzer (ANDO: AQ-6315A), laser oscillation occurs at a wavelength of 543 nm with an excitation power of 130 mW or more. It was confirmed. Further, the optical power of the laser light transmitted through the mirror 711 was measured using a bandpass filter (transmission wavelength: 543 ± 10 nm) and a power meter head (manufactured by Anritsu: MA9411A). When 200 mW of excitation light was incident on the Er ^{3 +} -added fluoride glass fiber 707, the output of the 543 nm laser was 8 mW. In addition, since the light which permeate | transmitted the mirror 711 is radiate | emitted from the single mode fiber, it is clear that the beam shape is a single mode (LP01).

FIG. 7 shows a third embodiment. The optical system shown in FIG. 7 is a gallium nitride semiconductor laser 801 (with indium added, center wavelength 448 nm: manufactured by Nichia Corporation), an aspheric lens 802 (NA: 0.60), a cylindrical lens, which is an excitation light source. 803 (f = −25 mm), cylindrical lens 804 (f = 50 mm), aspherical lens 805 (NA: 0.30), filter 806 (AR: 448 nm, HR: 470-570 nm), Er ^{3+ as} a laser medium added Fluoride glass fiber 807 (ZBLAN, Er ³⁺ : 3000 ppm, NA: 0.22, core diameter: 3.3 μm, fiber length: 65 cm), tap coupler 809 made of quartz fiber (Nufern 460HP: single at wavelength 543 nm) Mode, branching ratio at wavelength 543nm is 9: 1), Mira -811 (wavelength: 543 ± 10 nm, reflectance: 99.5%, other wavelengths are transmitted).

The Er ^{3 +} -added fluoride glass fiber 807 is fusion-bonded with the quartz fiber 809-a (fusion-bonding portion 808). The light generated by the Er ^{3 +} -added fluoride glass fiber 807 is input to the coupler 809-a port, and is output 90% to the 809-b port and 10% to the 809-d port. Of the light output to the 809-b port, the light in the range of 543 ± 10 nm is reflected by the mirror 811 and travels in the opposite direction, and is again coupled to the coupler port 809-b. Of the light traveling in the opposite direction, 90% is coupled to the 809-a port and 10% is coupled to the 809-c port. Therefore, the laser light is output from both ports 809-c and 809-d, and the laser light taken out from the resonator corresponds to 19% of the energy stored in the resonator. Since the reflected light generated at the fiber ends of the 809-c and 809-d ports may be recombined into the resonator, the fiber end faces of the 809-c and 809-d ports are subjected to oblique cleaving. It is. In addition to the oblique cleaving process, reflected light can be suppressed by installing an optical isolator.

When the laser light obtained from the 809-c port is monitored by an optical spectrum analyzer (ANDO: AQ-6315A), 200 mW of excitation light is introduced into the Er ^{3 +} -added fluoride glass fiber 807 and the excitation power is increased. The laser oscillation was confirmed at a wavelength of 543 nm with an excitation power of 120 mW or more.
Next, the optical power of the laser light output from the ports 809-c and 809-d was measured using a band-pass filter (transmission wavelength 543 ± 10 nm) and a power meter head (manufactured by Anritsu: MA9411A). When 200 mW of the excitation light was incident on the Er ^{3 +} -added fluoride glass fiber 807, the total output of the 543 nm laser obtained from the two output ports was 11 mW. Since the light transmitted through the mirror 811 is emitted from the single mode fiber, it is clear that the beam shape is single mode (LP01).

  The present invention can be used as a light source used in the medical / biological field, an industrial inspection light source, a display light source, a projection light source, an optical gyro light source, and the like.

101: Excitation light source 102: Condensing lens 103: Excitation light transmission / laser light reflection filter 104: Rare earth-added fluoride glass fiber 104-a: Excitation side rare earth-added fluoride glass fiber end face 104-b: Opposite to excitation side Rare earth-doped fluoride glass fiber end face 105: laser beam partial reflection mirror 201: collimating lenses 401, 701, 801: gallium nitride semiconductor lasers 402, 405, 408, 702, 705, 710, 802, 805: aspherical lens 403 , 404,703,704,803,804: a cylindrical lens 406,706,806: filter 407,707,807: ^{Er 3+} doped fluoride glass fiber 407-a, 707-a: the excitation side ^{Er 3+} doped fluoride glass Fiber end face 407-b: opposite to the excitation side The ^{Er 3+} doped fluoride glass fiber end face 409,711,811: Mirror 708,808: fusion splice 709: silica fiber 809: tap coupler

Claims (4)

An excitation light source, a first mirror that transmits excitation light emitted from the excitation light source and reflects light in a desired wavelength band excluding the wavelength of the excitation light, and a second mirror that reflects light in the desired wavelength band In a laser device including a resonator in which a mirror is disposed to be opposed and a laser medium that emits light by the excitation light is disposed between optical paths of a first mirror and a second mirror,
The excitation light source has a wavelength of excitation light in the range of 340 nm to 500 nm, the gallium nitride semiconductor light source, and the laser medium have at least Er ³⁺ , Ho ³⁺ , Sm ³⁺ , Tm ³⁺ , Dy ³⁺ , Eu ³⁺ , Tb ³ , Or fluoride glass or fluoride crystals to which any one of Nd ³⁺ is added,
A laser device characterized in that the laser oscillation wavelength is longer than the excitation wavelength. 2. The laser device according to claim 1, wherein at least one optical waveguide having a single mode in the desired wavelength band is inserted in the optical path of the resonator. The laser device according to claim 1, wherein the laser medium forms a core portion of an optical waveguide. 4. The laser device according to claim 1, wherein an optical waveguide made of silica glass is connected to one end or both ends of the laser medium.

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