JP2005174993A - Pulse fiber laser equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide ultrashort pulse fiber laser equipment having high excitation efficiency and reliability. <P>SOLUTION: Pulse fiber laser equipment is provided with an optical fiber amplification element 2 generating a laser beam, reflectors connected to the front part and the rear part of the optical fiber amplification element 2, and an energizing light source 4 for supplying excitation light to the optical fiber amplification element 2. The resonator 10 is constituted of the optical fiber amplification element 2 and the reflectors. At least one reflector is a fiber Bragg grating 3 having a saturable property. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a pulse fiber laser device for generating an ultrashort pulse laser in the picosecond range or femtosecond range. Specifically, a rare earth-doped optical fiber doped with a gain medium is used as an optical amplification element. Belongs to the technical field of pulsed fiber lasers using passive mode-locking technology.

  The mode-locked pulse fiber laser is an important technique for generating a very short pulse laser of femtosecond (fsec) or picosecond (psec). Further, in a mode-locked pulse fiber laser device, a mode-lock technique is indispensable for synchronizing the phase of the generated laser in the longitudinal mode.

  The mode-locking technology includes passive mode-locking (passive mode-locking) in which a saturable absorber is inserted in the resonator, and resonator loss and laser medium gain according to the period in which light circulates in the resonator. There are active mode lock (active mode lock) to be modulated, and hybrid mode lock using both.

  The active mode lock method has an advantage that a modulator is usually arranged in a resonator, and it has good stability and can be used in a wide wavelength band. On the other hand, the passive mode-locking method is a mode in which mode locking occurs and narrows the pulse width because the pulse is modulated by the nonlinear effect due to the electric field of the optical pulse itself when passing through the nonlinear medium. It is a system that can stably obtain the ultra-short pulse.

  In particular, it can be said that a passive mode-locked fiber laser that does not require a modulator during operation is highly practical from the technical and cost viewpoints.

  Conventionally, semiconductor saturable absorbers have been used for passive mode-locked fiber lasers. In general, in a semiconductor material, electrons are in an energy state called a valence band under normal circumstances. When the semiconductor saturable absorber absorbs light, electrons transition from the valence band to the conduction band to form electron-hole pairs. The energy difference between the valence band and the conduction band is called a band gap. When the semiconductor is irradiated with light having energy equal to or higher than the band gap energy of the semiconductor, the light energy is absorbed by the semiconductor, and some of the electrons are transferred to the conduction band, and the electron-positive A hole pair is created. Although this electron-hole pair eventually disappears, it takes a certain time. This average lifetime until disappearance is called “carrier lifetime”. There are two types of annihilation processes: radiative annihilation processes and non-radiative annihilation processes.

The radiation annihilation process involves a photon emitted at a frequency proportional to the band gap energy, and the electrons fall from the conduction band to the valence band. The annihilation process has a time constant of several nanoseconds (about 10 ^-9 seconds) that is specific to a specific semiconductor material.

  The non-radiative annihilation process is a process by combining electrons and holes without generating photons. This non-radiative annihilation process is based on defects and impurities in the semiconductor. The time constant of the non-radiative annihilation process depends on the concentration of impurities and defects and may be shorter than 1 picosecond.

  The semiconductor saturable absorber used in the mode-locked fiber laser utilizes the absorption saturation mechanism of the semiconductor. That is, as described above, when the semiconductor absorbs light, the electrons transition from the valence band to the conduction band to create electron-hole pairs. When the intensity of the incident light is high, so many transitions occur that the valence band is almost empty, the conduction band is filled, and the semiconductor's ability to absorb light is weakened. The semiconductor saturable absorber that has reached the saturation state as described above recovers through the annihilation process, but this characteristic depends on the carrier lifetime. When the carrier lifetime is shortened, the annihilation of electron-hole pairs is accelerated and the recovery of the semiconductor saturable absorber is accelerated.

  A mode-locked pulse laser using a change in light absorption ability by this semiconductor saturable absorber is disclosed (see, for example, Patent Document 1).

  However, when a semiconductor saturable absorber is used, it is necessary to individually create a semiconductor having a band gap and a carrier life that exactly match the oscillation wavelength of the laser light. Usually, a semiconductor saturable absorber is produced by a metal organic chemical vapor deposition method or the like, but it has been very difficult to strictly control the carrier lifetime. Moreover, the recovery time of the semiconductor saturable absorber has a limit in the picosecond range, and it is possible to create a semiconductor with a short carrier lifetime that can be used for a mode-locked fiber laser for an ultrashort pulse laser in the femtosecond range. It was very difficult technically.

  As an improvement measure, a passive mode-locked pulsed fiber laser using a polarizer is also disclosed (for example, see Non-Patent Document 1).

  The high light intensity pulse propagating in the resonator has a different polarization state in the entire pulse depending on the light intensity. For this reason, when the polarizer is allowed to pass, there are a portion where the pulse can pass and a portion where the pulse cannot pass. A short pulse can be generated by adjusting this with a polarization controller and passing the polarizer only in the vicinity of the pulse peak.

Since the pulse fiber laser using the polarization maintaining isolator uses the nonlinear optical effect as described above, the modulation operation does not depend on the recovery time unlike the semiconductor saturable absorber. Therefore, the pulse fiber laser can realize generation of an ultrashort pulse laser in the femtosecond range.
JP-A-9-167869 K. Tamura et al., “Self-starting additive pulse mode-locked erbium fiber ring laser”, Electronics Letters 19th Novenber 1992 Vol. 28 No. 24

  However, in the pulse fiber laser using the polarization maintaining isolator, the light that does not pass through the polarization maintaining isolator does not contribute to the oscillation, which may reduce the pumping efficiency.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a pulse fiber laser device having high excitation efficiency and reliability at low cost.

  The present invention is a passive mode-locked type pulse fiber laser device using a fiber Bragg grating instead of a saturable absorber.

  The present invention includes an optical fiber amplifying element that generates laser light, reflectors connected respectively before and after the optical fiber amplifying element, and a pumping light source that supplies pumping light to the optical fiber amplifying element, A pulse fiber laser device comprising a resonator by an optical fiber amplifying element and a reflector, wherein at least one of the reflectors is a fiber Bragg grating having a saturable characteristic. is there.

  A fiber Bragg grating that functions as a saturable body in the present invention will be described.

The fiber Bragg grating according to the present invention is typically produced by irradiating a single mode optical fiber having a predetermined length with ultraviolet rays having interference fringes. The fiber Bragg grating has a grating length L (m), a refractive index modulation width which is a difference in refractive index in the grating, Δn, a ratio of propagating light propagating through the core of the grating to η, and effective grating refraction. the rate n, when the grating period is lambda (m) the reflectivity of the fiber Bragg grating R _B is represented by the following formula 1.

In the above equation 1, n and Δn have light intensity dependency, the refractive index of the core glass is n ₀ , the nonlinear optical coefficient n ₂ , and the electric field of light is E (the absolute value of E is squared). Then, the following formula 2 holds.

In the fiber Bragg grating, when the refractive index of the portion where the refractive index is high is n ′, the above n ′ is expressed by the following formula 3. Here, n ₀ ′ is the refractive index of the core of the high refractive index portion of the grating, and n ₂ ′ is the nonlinear optical coefficient of the high refractive index portion.

  Further, the above Δn can be expressed by the following formula 4.

From each of these formulas, [Delta] n / n contained in reflectance R _B shown in Equation 1 can be transformed to claim represented by the following formula 5.

As shown in the above formula 5, the reflectivity of the fiber Bragg grating R _B, in order to vary depending on the propagation light, it expresses saturable characteristic.

  In the pulse fiber laser device, the fiber Bragg grating preferably contains a metal element.

In the pulse fiber laser device, the fiber Bragg grating preferably has a refractive index difference larger than 2 × 10 ⁻⁴ .

  In the pulse fiber laser device, the number of longitudinal modes of the oscillating laser light is set to 10 or more and 50000 or less by controlling the reflection band of the fiber Bragg grating and the resonator length of the resonator. Preferably it is.

  Further, in the pulse fiber laser device, the optical fiber amplifying element can be composed of a rare earth-doped optical fiber.

  In the above-mentioned pulse fiber laser device, all of the optical fibers and optical elements to be used have polarization maintaining properties, and it is possible to compete with the polarization maintaining fiber and the polarization maintaining element.

-Action-
In the said invention, a laser beam generate | occur | produces in an optical fiber amplifier with the excitation light supplied from the excitation light source. The laser light generated by the optical fiber amplifying element is resonated by a resonator constituted by reflectors respectively connected before and after the optical fiber amplifying element. In the present invention, since at least one of the reflectors is composed of a fiber Bragg grating having saturable characteristics, when the pulse laser is reflected by the fiber Bragg grating, it is mode-locked and has a large peak power, and Pulse laser light having an extremely narrow pulse width can be generated.

  When the fiber Bragg grating contains a metal element, the nonlinear optical effect can be improved, and laser light with low power can be effectively pulsed.

The fiber Bragg grating can improve nonlinear optical characteristics when the refractive index difference is larger than 2 × 10 ⁻⁴ , and can effectively pulse laser light with low power.

  In the above pulse fiber laser device, if the number of longitudinal modes of the oscillating laser beam is 10 or more and 50000 or less, the laser beam can be stably pulsed. That is, if the number of longitudinal modes of the laser light is less than 10, the generated laser light tends to be difficult to be pulsed, and if the number of longitudinal modes is more than 50000, the saturable body using the fiber Bragg grating is used. In this case, the mode lock may be difficult.

  The optical fiber amplifying element is composed of a rare earth-doped optical fiber, and generates fluorescence based on spontaneous emission of rare earth elements inside the fiber when excitation light is input from the excitation light source.

  In the above pulse fiber laser device, when all of the optical fibers and optical elements used have polarization maintaining properties, the stability of the pulse laser can be improved.

  According to the present invention, since a fiber Bragg grating is used as a reflector used in the resonator, the laser light is mode-locked using a nonlinear optical effect, so that it is extremely short in the picosecond range or femtosecond range. A pulsed laser can be generated.

  Further, according to the present invention, since all the laser light generated by the optical fiber amplifying element can be resonated by the fiber Bragg grating, the pumping light rate can be kept high.

  Furthermore, according to the present invention, by using the fiber Bragg grating instead of the saturable absorber, it is not necessary to prepare a saturable absorber corresponding to the oscillation wavelength unlike the semiconductor saturable absorber. Therefore, according to the present invention, a high-performance pulse fiber laser device can be provided at a low cost.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

Embodiment 1 of the Invention
A pulse fiber laser device 1 according to the present invention includes an optical fiber amplifying element that generates laser light, reflectors connected respectively before and after the optical fiber amplifying element, and pumping that supplies pumping light to the optical fiber amplifying element. And a fiber Bragg grating (hereinafter referred to as “FBG”) having at least one saturable characteristic. ").”

  FIG. 1 is a configuration diagram of a pulse fiber laser device 1 according to an embodiment of the present invention.

  The pulse fiber laser device 1 in FIG. 1 resonates spontaneous emission light generated by the spontaneous emission effect of the rare earth-doped optical fiber 2 that is an optical fiber amplifying element between two reflectors using FBGs, and outputs an output terminal. 8 outputs an ultrashort pulse laser.

  More specifically, in the rare earth-doped fiber 2, the core is doped with a rare earth element such as erbium (Er) or yttrium (Yb) as a gain medium, and the outer peripheral surface of the core is covered with a clad. An optical fiber made of quartz. In the present embodiment, the rare earth doped fiber 2 to which Yb is added as the rare earth element is used. The length of the rare earth-doped optical fiber 2 is set so as to regulate the number of longitudinal modes within a predetermined range. In this embodiment, the length of the resonator 10 is set to about 8 m, the concentration of added Yb is set to 10000 ppm, and the concentration length product is set to about 20 (kppm · m). The resonator 10 including the rare earth-doped optical fiber 2 emits 1064 nm light with respect to 980 nm excitation light.

  FBGs 3 and 3 ′ are connected to the front and rear ends of the rare earth-doped optical fiber 2 as reflectors, respectively. Each of these FBGs 3 and 3 'has a saturable characteristic. That is, the reflectivities of the FBGs 3 and 3 'vary depending on the optical power of the incident laser light. In this embodiment, the reflectance of the FBG 3 on the output end 8 side is about 5% for light with a wavelength of 1064 nm, and the reflectance of the FBG 3 ′ on the opposite side is also about 99% for light with a wavelength of 1064 nm. It is set to be the above.

  More specifically, the FBG 3 according to the present embodiment has a grating length of 20 mm and a reflectance of 99% or more.

  The FBGs 3 and 3 'are preferably doped with, for example, Sn (tin) or Pb (lead). By doping these metal elements, the nonlinear optical coefficient of the FBG increases, and even low-power laser light can be pulsed, and the efficiency of pulse laser generation can be increased. In the present embodiment, an Sn-doped fiber is used.

In the present embodiment, the refractive index difference Δn between the FBGs 3 and 3 ′ is set to be larger than 2 × 10 ⁻⁴ . Thereby, even when the power of the laser beam is small, the difference in the nonlinear optical coefficient can be easily generated.

  An optical isolator 7 is connected between the FBG 3 on the emission end side and the emission end 8. The optical isolator 7 has a function of transmitting the light from the FBG 3 to the emission end 8 as it is and conversely blocking the light from the emission end 8 to the FBG 3.

  On the other hand, a non-reflective terminal 6 is connected in front of the opposite FBG 3 '.

  An excitation light source 4 is connected between the FBG 3 ′ and the non-reflective terminal 6 via a WDM coupler 5. The excitation light source 4 incorporates a laser diode chip (hereinafter also referred to as “LD chip”), and supplies excitation light having a wavelength of 980 nm to the rare earth-doped optical fiber 2 with a predetermined output.

  Each element used in the pulse fiber laser device 1 according to this embodiment is connected by a normal single mode fiber 9. As described above, the optical fiber 9 for connecting the elements may be a normal single mode fiber as described above, but is preferably a polarization maintaining fiber in order to further stabilize the output of the pulse laser. Furthermore, from the viewpoint of the stability of the pulse laser, each element used in the pulse fiber laser device 1 is preferably a polarization maintaining element provided with polarization maintaining by an appropriate means.

  Next, the operation of the pulse fiber laser device 1 according to this embodiment will be described.

  Excitation light having a wavelength of 980 nm generated by the excitation light source 4 is introduced into the optical fiber 9 through the WDM coupler 5 and is incident on the rare earth-doped optical fiber 2. The FBG 3 'is transparent to excitation light having a wavelength of 980 nm. Therefore, the excitation light passes through the FBG 3 ′ and is introduced into the rare earth-doped optical fiber 2. The excitation light introduced into the rare earth doped optical fiber 2 excites the doped yttrium element. Then, when the excited yttrium element returns to the ground state, spontaneous emission light having a wavelength of 1064 nm is generated.

  Spontaneous emission light generated in the rare earth-doped optical fiber is resonated into laser light by a resonator composed of the rare earth-doped fiber 2 and the FBGs 3 and 3 'connected before and after the rare earth doped fiber 2. When this laser beam is reflected by the FBG, it is mode-locked by the saturable characteristic of the FBG, so that it becomes a palace laser with a high peak power and a very short pulse width. Here, in order to stabilize oscillation, temperature control may be applied to the resonator, and periodic vibrations or periodic temperature fluctuations may be applied to the fiber grating.

  A part of the pulse laser generated in the resonator in this way passes through the FBG 3 and the optical isolator 7 on the output end side and is taken out from the output end 8.

  The optical isolator 7 blocks part of the laser light reflected toward the resonator at the output end 8 and external light incident from the output end 8 to prevent damage to the resonator and unstable resonance. To do.

  A part of the pulse laser generated by the resonator passes through the opposite FBG 3 ′ and the WDM coupler 5 and is introduced into the non-reflection termination 6.

  FIG. 2 is a graph showing an output waveform of the pulse fiber laser device 1 of the present embodiment, and FIG. 3 shows an oscillation spectrum of the pulse fiber laser device 1 of the present embodiment. 2A shows an output waveform at a certain time, and FIG. 2B shows an output waveform at another time.

  As shown in FIG. 2, the pulse fiber laser device of this embodiment can generate an extremely short pulse with a pulse width of about 10 nsec (measurement limit of the measuring device).

  As shown in FIG. 3, the oscillation spectrum of the pulse fiber laser device of the present embodiment has a sufficiently wide wavelength band compared to the linear spectrum of a conventional CW (Continuous Wave) fiber laser device. I understand that. In this embodiment, when the oscillation spectrum width is 0.1 nm, the resonator length of the pulse fiber laser device is twice the fiber length used for the resonator and is about 16 m. Therefore, in this embodiment, there are about 230 longitudinal mode numbers per pulse.

  As described above, the pulse fiber laser device 1 according to the present embodiment can stably generate an ultrashort pulse laser as described above. Further, the resonator according to the present embodiment does not use a spatial optical element such as a reflecting mirror, a lens, or an optical filter, and is configured only by FGB and an optical fiber. Therefore, the pulse fiber laser device 1 has an extremely small loss of the pulse laser, exhibits a high pumping light rate and reliability, and can be manufactured at a low cost.

<< Embodiment 2 of the Invention >>
FIG. 4 is a configuration diagram of a pulse fiber laser device according to another embodiment of the present invention.

  In the present embodiment, the same elements as those in the first embodiment are denoted by the same reference numerals, and a part of the description is omitted.

  The pulse fiber laser device 10 of FIG. 4 resonates spontaneous emission light generated by the spontaneous emission effect of the rare earth-doped optical fiber 2 that is an optical fiber amplifying element between two reflectors using the total reflection mirror 12 and the FBG 13. Thus, an ultrashort pulse laser is output from the output end 8.

  More specifically, in the rare earth-doped fiber 2, the core is doped with yttrium (Yb), which is a rare earth element, as a gain medium in the core, and the outer peripheral surface of the core is covered with a cladding. An optical fiber made of quartz. The length of the rare earth-doped optical fiber 2 is set so as to regulate the number of longitudinal modes within a predetermined range. In this embodiment, the length of the rare earth doped fiber 2 is set to about 8 m, the concentration of the added Yb is set to 10000 ppm, and the concentration length product is set to about 20 (kppm · m). The rare earth-doped optical fiber 2 emits light of 1064 nm with respect to excitation light of 980 nm.

  One end of the rare earth-doped optical fiber 2 is connected to a total reflection mirror 12 as a reflector. The total reflection mirror 12 totally reflects about 93% of the light incident from the rare earth-doped optical fiber 2 and reflects it again toward the rare earth-doped optical fiber.

  The other end of the rare earth-doped optical fiber 2 is connected to a 3 dB coupler 14 via a WDM coupler 5 for pumping light incidence. In the 3 dB coupler 14, the optical fiber is branched into two, and one optical fiber is connected to the output end 8 via the optical isolator 7. The other optical fiber is connected to the FBG 13.

  The FBG 13 has saturable characteristics as in the first embodiment. That is, the reflectance of the FBG 13 changes depending on the optical power of the incident laser light. In this embodiment, the reflectance of the FBG 13 is set to be about 99% or more with respect to light having a wavelength of 1064 nm.

  The FBG 13 is preferably doped with, for example, Sn (tin) or Pb (lead). By doping these metal elements, the nonlinear optical coefficient of the FBG increases, and even low-power laser light can be pulsed, and the efficiency of pulse laser generation can be increased. In the present embodiment, an Sn-doped fiber is used.

In this embodiment, the refractive index difference Δn of the FBG 13 is set to be larger than 2 × 10 ⁻⁴ . Thereby, even when the power of the laser beam is small, the difference in the nonlinear optical coefficient can be easily generated.

  An optical isolator 7 is connected between the 3 dB coupler 14 and the emission end 8. The optical isolator 7 has a function of transmitting the light from the rare earth-doped optical fiber 2 to the emission end 8 as it is, and conversely blocking the light from the emission end 8 to the rare earth-doped optical fiber 2.

  A pumping light source 4 is connected between the rare earth-doped optical fiber 2 and the 3 dB coupler 14 via a WDM coupler 5. The excitation light source 4 includes an LD chip, and supplies excitation light having a wavelength of 980 nm to the rare earth-doped optical fiber 2 with a predetermined output.

  Each element used in the pulse fiber laser device 1 according to this embodiment is connected by a normal single mode fiber 9. As described above, the optical fiber 9 may be a normal single mode fiber as described above, but is preferably a polarization maintaining fiber in order to further stabilize the output of the pulse laser. Furthermore, from the viewpoint of the stability of the pulse laser, each element used in the pulse fiber laser device 10 is preferably a polarization maintaining element provided with polarization maintaining by an appropriate means.

  Next, the operation of the pulse fiber laser device 10 according to this embodiment will be described.

  Excitation light having a wavelength of 980 nm generated from the excitation light source 4 is emitted to the rare earth-doped optical fiber 2 through the WDM coupler 5. The excitation light introduced into the rare earth doped optical fiber 2 excites the doped yttrium element. Then, when the excited yttrium element returns to the ground state, spontaneous emission light having a wavelength of 1064 nm is generated.

  Spontaneous emission light generated in the rare earth-doped optical fiber 2 is resonated by the resonator composed of the total reflection mirror 12 and the FBG 13 to become laser light. When this laser beam is reflected by the FBG 13, it is mode-locked by the saturable characteristic of the FBG 13, so that it becomes a palace laser with a high peak power and a very short pulse width. This pulse laser is demultiplexed by the 3 dB coupler 14, passes through the optical isolator 7, and is output from the output terminal 8.

  FIG. 5 is a graph showing an output waveform of the pulse fiber laser device 10 of the present embodiment, and FIG. 6 shows an oscillation spectrum of the pulse fiber laser device 10 of the present embodiment. Each of the graphs (a) to (f) in FIG. 5 shows an output waveform at a certain time.

  As shown in FIG. 5, in the pulse fiber laser device 10 of the present embodiment, a pulse laser with an extremely short pulse width of about 500 nsec can be generated although the peak intensity of the pulse changes every moment.

  As shown in FIG. 6, the oscillation spectrum of the pulse fiber laser device of this embodiment has a sufficiently wide wavelength band as compared with the linear spectrum of a conventional CW (Continuous Wave) fiber laser device. I understand that. In the present embodiment, when the oscillation spectrum width is 0.1 nm, the resonator length of the pulse fiber laser device is twice the length of the rare earth-doped optical fiber and is about 16 m. Therefore, in this embodiment, the number of longitudinal modes is 1600 per pulse.

《Comparative example》
In order to compare with the pulse fiber laser apparatus according to the present invention, the apparatus shown in FIG. 7 was prepared as a comparative example, and the state of the output laser beam was observed. The apparatus 20 shown in FIG. 7 is obtained by replacing the FBG 13 of the pulse fiber laser apparatus shown in the second embodiment with a Fresnel reflector 22. Since other elements are the same as those used in the second embodiment, the same elements are denoted by the same reference numerals and description thereof is omitted.

  The oscillation wavelength of this device is determined by inserting a band pass filter 21. When pumping light was introduced into the rare earth-doped optical fiber 2 from the pumping light source 4 of the apparatus 20 according to the comparative example, the laser beam shown in FIG.

  The graphs (a) to (d) shown in FIG. 8 each show an output waveform at a certain time. As can be seen from each graph of FIG. 8, the laser output waveform from the apparatus 20 according to this comparative example has a beat shape with a relatively short period (approximately 5 nsec), but is not in a pulse shape. Also, the amplitude of the output intensity and the beat cycle vary greatly with time and are very unstable. Thus, it can be seen that the present apparatus using the Fresnel reflector as the resonator reflector cannot generate a stable ultrashort pulse laser.

It is a figure which shows the structure of the pulse fiber laser apparatus which concerns on one Embodiment of this invention. It is a figure which shows the output waveform of the pulse laser output from the pulse fiber laser apparatus shown in FIG. It is a figure which shows the oscillation spectrum of the pulse laser output from the pulse fiber laser apparatus shown in FIG. It is a figure which shows the structure of the pulse fiber laser apparatus which concerns on other embodiment of this invention. It is a figure which shows the output waveform of the pulse laser output from the pulse fiber laser apparatus shown in FIG. It is a figure which shows the oscillation spectrum of the pulse laser output from the pulse fiber laser apparatus shown in FIG. It is a figure which shows the structure of the fiber laser apparatus which concerns on the comparative example of this invention. It is a figure which shows the output waveform of the laser output from the fiber laser apparatus shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pulse fiber laser apparatus 2 Rare earth addition optical fiber 3, 3 'FBG (fiber Bragg grating)
4 Excitation light source 5 WDM coupler 6 Non-reflective termination 7 Optical isolator 8 Output end 9 Single mode optical fiber

Claims (6)

An optical fiber amplifying element for generating laser light; a reflector connected to the front and rear of the optical fiber amplifying element; and a pumping light source for supplying pumping light to the optical fiber amplifying element. And a pulse fiber laser device that constitutes a resonator by a reflector,
At least one of the reflectors is a fiber Bragg grating having a saturable characteristic. The pulse fiber laser device according to claim 1,
The fiber Bragg grating contains a metal element. The pulse fiber laser device according to claim 1,
The above-mentioned fiber Bragg grating has a refractive index difference larger than 2 × 10 ⁻⁴ . The pulse fiber laser device according to claim 1,
By controlling the reflection band of the fiber Bragg grating and the resonator length of the resonator, the number of longitudinal modes of the oscillating laser light is set to 10 or more and 50000 or less, and the pulse fiber laser apparatus. The pulse fiber laser device according to claim 1,
The pulse fiber laser device, wherein the optical fiber amplifying element is a rare earth doped optical fiber. The pulse fiber laser device according to claim 1,
A pulse fiber laser device comprising a polarization maintaining fiber and a polarization maintaining element.

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