WO2021246531A1 - 2つの異なる波長を選択的に用いるモード同期方法、および、当該方法を用いたレーザー装置 - Google Patents
2つの異なる波長を選択的に用いるモード同期方法、および、当該方法を用いたレーザー装置 Download PDFInfo
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- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 3
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- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
- H01S3/11—Mode locking; Q-switching; Other giant-pulse techniques, e.g. cavity dumping
- H01S3/1106—Mode locking
- H01S3/1112—Passive mode locking
- H01S3/1115—Passive mode locking using intracavity saturable absorbers
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- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
- H01S3/06—Construction or shape of active medium
- H01S3/063—Waveguide lasers, i.e. whereby the dimensions of the waveguide are of the order of the light wavelength
- H01S3/067—Fibre lasers
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- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
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- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
- H01S3/06—Construction or shape of active medium
- H01S3/063—Waveguide lasers, i.e. whereby the dimensions of the waveguide are of the order of the light wavelength
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- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
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- H01S3/08—Construction or shape of optical resonators or components thereof
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- H01S3/08022—Longitudinal modes
- H01S3/08027—Longitudinal modes by a filter, e.g. a Fabry-Perot filter is used for wavelength setting
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- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
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- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/14—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range characterised by the material used as the active medium
- H01S3/16—Solid materials
- H01S3/1601—Solid materials characterised by an active (lasing) ion
- H01S3/1603—Solid materials characterised by an active (lasing) ion rare earth
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- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
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- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/09—Processes or apparatus for excitation, e.g. pumping
- H01S3/091—Processes or apparatus for excitation, e.g. pumping using optical pumping
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- H01S3/0941—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light of a laser diode
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- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/14—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range characterised by the material used as the active medium
- H01S3/16—Solid materials
- H01S3/1601—Solid materials characterised by an active (lasing) ion
- H01S3/1603—Solid materials characterised by an active (lasing) ion rare earth
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- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/14—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range characterised by the material used as the active medium
- H01S3/16—Solid materials
- H01S3/1601—Solid materials characterised by an active (lasing) ion
- H01S3/1603—Solid materials characterised by an active (lasing) ion rare earth
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- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/14—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range characterised by the material used as the active medium
- H01S3/16—Solid materials
- H01S3/1601—Solid materials characterised by an active (lasing) ion
- H01S3/1603—Solid materials characterised by an active (lasing) ion rare earth
- H01S3/1616—Solid materials characterised by an active (lasing) ion rare earth thulium
Definitions
- the present invention relates to a method and a laser device that easily realizes self-starting mode synchronization by selectively using two different wavelengths.
- Patent Document 1 US8416817
- Patent Document 2 US7940816
- a mode-synchronized fiber laser In a laser device that generates picosecond or femtosecond pulsed laser light, it is preferable to oscillate a mode-synchronized laser by a simple method and stabilize it in a short time.
- mode-synchronized fiber lasers with small fiber size, low cost, and excellent environmental stability have been used in many industrial applications.
- a mode-synchronized fiber laser (ANDiMLFL: AllNormalDispersionMode-Locked) that is composed of a polarization-maintaining fiber (PMF) with excellent environmental stability and uses only optical components that show normal dispersion at the oscillation wavelength of the laser. Since the Fiber Laser) can output high pulse energy, it is suitable for applications such as microfabrication.
- the choice of laser oscillation wavelength is wide, but in the mode-synchronized laser, the selectivity of the oscillation wavelength is low, and it is difficult to obtain the mode-synchronized laser oscillation at a wavelength having a small stimulated emission cross-sectional area.
- a mode-synchronized pulsed light generation filter that easily realizes self-starting mode synchronization is provided, and by providing the mode-synchronized pulsed light generation filter (filter unit), picoseconds and femtoseconds are provided.
- a laser device that generates pulsed laser light.
- the laser device may include an amplification unit that amplifies and outputs the laser beam in the resonator.
- the mode-synchronized pulsed light generation filter may be provided in the resonator.
- the pass wavelength characteristic of the mode-synchronized pulsed light generation filter may have a maximum value at at least two or more wavelengths.
- the mode-synchronized pulsed light generation filter may selectively pass the wavelength component of light according to the passing wavelength characteristic.
- the pass wavelength characteristics of the mode-synchronized pulse light generation filter are the first pass band that selectively passes the first wavelength component, which is the wavelength component of the oscillation wavelength of the laser light, and the second wavelength, which is a wavelength component different from the oscillation wavelength. It may have a second pass band through which the components are selectively passed.
- the filter unit may be one filter provided at one place in the propagation path of the laser light.
- the filter unit may have two or more filters provided at different locations. Both the first pass band and the second pass band may be set in one bandpass filter.
- An optical fiber Bragg grating referred to as an FBG that selects the first pass band and an FBG that selects the second pass band may be provided in the propagation path of the laser beam.
- the passing wavelength characteristic of the filter unit may have a minimum value between the two maximum values.
- the minimum value may be a value attenuated by -10 dB or more as compared with the lower maximum value.
- the minimum value may be attenuated by ⁇ 20 dB or more as compared with the maximum value.
- the minimum value may be attenuated by -30 dB or more as compared with the maximum value.
- the passing wavelength characteristic of the filter unit may be connected between the two maximum values.
- the passing wavelength characteristic of the filter unit does not have to be connected between the two maximum values.
- the pass wavelength characteristic of the filter unit may have other components between the first pass band and the second pass band. The other component may be a linear component.
- the size of the second wavelength component may be 10% or less of the first wavelength component.
- the pass bandwidth of the second filter unit may be narrower than the pass bandwidth of the first filter unit.
- the pass bandwidth of the second filter unit may be 0.2 nm or more.
- the pass bandwidth of the second filter unit may be 4.6 nm or less.
- the attenuation factor of the second filter unit with respect to the second wavelength component may be larger than the attenuation factor of the first filter unit with respect to the first wavelength component.
- the wavelength difference between the first center wavelength of the pass band of the first filter unit and the second center wavelength of the pass band of the second filter unit may be 18 nm or less.
- the wavelength difference may be 9 nm or more.
- the amplification unit may include Yb fiber. Both the first center wavelength and the second center wavelength may be 1020 nm or more and 1100 nm or less.
- the amplification unit may include Er fiber.
- the first center wavelength and the second center wavelength may both be 1530 nm or more and 1555 nm or less, or 1555 nm or more and 1600 nm or less.
- the amplification unit may include Nd fiber.
- the first center wavelength and the second center wavelength may both be 1080 nm or more and 1080 nm or less, or 888 nm or more and 914 nm or less.
- the amplification unit may include Tm fiber.
- the first center wavelength and the second center wavelength may both be 1960 nm or more and 2020 nm or less, or 1860 nm or more and 1960 nm or less.
- the first pass band and the second pass band may be variable.
- the width of the first pass band may be increased.
- the width of the second pass band may be reduced.
- the attenuation factor in the second pass band may be increased.
- the laser device may be equipped with a polarizer that converts the laser light into linearly polarized light.
- the laser device may include a polarization-retaining fiber that propagates the laser beam.
- the laser device may include a NALM that functions as a saturable absorber.
- the amplification unit may be a planar waveguide containing rare earths such as Yb and Er.
- the laser device may include a laser input unit that combines the laser light transmitted through the optical transmission unit and the excitation laser light.
- the laser input unit may be a WDM (wavelength division multiplexing) coupler.
- the laser device may include a laser output unit that outputs a predetermined ratio of the laser light transmitted through the optical transmission unit.
- An optical isolator that defines the circumferential direction of the laser beam may be provided between the laser input unit and the laser output unit.
- the laser device may include a coupling unit that couples the optical transmission unit and the saturable absorption unit.
- the coupling portion may separate the laser beam input to the loop of the NALM into a component that propagates the loop clockwise and a component that propagates the loop counterclockwise.
- the laser device may include a reflecting unit that reflects the laser beam.
- the second filter unit, the first filter unit, and the reflection unit may be arranged in this order from the configuration closest to the amplification unit.
- the reflecting unit may reflect the laser light of the first wavelength component that has passed through the first filter unit to the first filter unit.
- a mode synchronization method for mode-synchronizing a laser beam in the path through which the laser light propagates, the wavelength component of the light is selectively passed according to the passing wavelength characteristic having a maximum value at at least two or more wavelengths, and the laser light is mode-synchronized.
- FIG. 1 is a diagram showing a configuration example of a laser device 100 according to an embodiment of the present invention.
- the laser device 100 is a device that generates laser light having a wavelength component in a predetermined oscillation band.
- the laser device 100 may generate laser light having a pulse width on the order of picoseconds (eg, 1 picosecond to 1000 picoseconds) or femtoseconds (eg, 1 femtosecond to 1000 femtoseconds).
- the first wavelength or oscillation wavelength
- the component having the first wavelength is referred to as the first wavelength component.
- the oscillation band may be a band centered on the first wavelength.
- the laser device 100 includes a filter unit 10, an amplification unit 20, and a saturable absorption unit 102 provided in the path through which the laser light propagates.
- the saturable absorption unit 102 absorbs the wavelength of the time component having a relatively low intensity in the incident laser light. Further, the saturable absorption unit 102 propagates the relatively high-intensity time component without absorbing it. That is, the saturable absorption unit 102 absorbs the low-intensity hem portion of the time waveform of the laser beam and passes the high-intensity peak portion to narrow the band of the laser beam in the time axis.
- the laser light can be shortened.
- the filter unit 10 and the amplification unit 20 may be configured to include an optical fiber, or may be configured to be connected to an optical fiber.
- the filter unit 10 and the amplification unit 20 may be arranged in a loop in which the laser beam circulates, or may be arranged in a path in which the laser beam reciprocates.
- each of the filter unit 10, the amplification unit 20, and the saturable absorption unit 102 may be a single component or circuit arranged at a specific location in the laser device 100, and may be dispersedly arranged in the laser device 100. It may be composed of a plurality of parts or circuits.
- the laser device 100 may function as a filter unit 10, an amplification unit 20, or a saturable absorption unit 102 as a whole.
- each component such as an optical fiber of the laser device 100 may be combined to function as a filter unit 10, an amplification unit 20, or a saturable absorption unit 102.
- the optical fiber propagating the laser light in the laser apparatus 100 may be at least a part of a polarization-retaining fiber (PMF). All the optical fibers constituting the laser device 100 may be polarization-retaining fibers.
- the common component may function as at least two of the filter unit 10, the amplification unit 20, and the saturable absorption unit 102.
- the amplification unit 20 may perform at least a part of the function of the filter unit 10
- the saturable absorption unit 102 may perform at least a part of the function of the filter unit 10.
- the amplification unit 20 amplifies the intensity of the passing laser light.
- the amplification unit 20 may have an optical fiber to which impurities such as rare earths have been added.
- the impurity is, for example, ytterbium (Yb), but is not limited thereto.
- the material of the optical fiber is, for example, quartz glass, but the material is not limited thereto.
- the amplification unit 20 may have a planar waveguide containing rare earths such as Yb and Er (erbium).
- the filter unit 10 has a predetermined passing wavelength characteristic, and selectively passes a wavelength component of light (in this example, natural radiation amplified light or laser light) according to the passing wavelength characteristic.
- the passing wavelength characteristic is a characteristic indicating the ratio of the intensity of light to be passed to the intensity of incident light at each wavelength.
- the filter unit 10 is a bandpass filter that attenuates wavelength components other than a predetermined pass band.
- the passing wavelength characteristic of the filter unit 10 has a maximum value at at least two or more wavelengths.
- the filter unit 10 of this example functions as a filter for passing a mode-synchronized pulse for starting the oscillation of the laser beam.
- the laser device 100 may have a polarizer that linearly polarizes the laser light propagating in the optical fiber.
- the intensity of the laser light transmitted from the filter unit 10 to the polarizer may be adjusted by adjusting the polarization axis of the polarization-retaining fiber between the polarizer and the filter unit 10.
- FIG. 2 is a diagram showing an example of the passing wavelength characteristics of the filter unit 10.
- the horizontal axis in FIG. 2 indicates the wavelength of the light propagating through the filter unit 10, and the vertical axis indicates the transmittance of each wavelength in the filter unit 10.
- the transmittance is the ratio of the light intensity after passing through the filter unit 10 to the light intensity before passing through the filter unit 10.
- the passing wavelength characteristic of the filter unit 10 may be the passing wavelength characteristic of the entire laser device 100.
- the passing wavelength characteristic of the filter unit 10 may be the passing wavelength characteristic when the laser light goes around the loop path once.
- the passing wavelength characteristic of the filter unit 10 may be the passing wavelength characteristic when the laser light reciprocates once in the path.
- the passing wavelength characteristic of the filter unit 10 may be the characteristic of the filter.
- An explicit filter is a component having a structure known as a filter, such as FBG.
- the passing wavelength characteristic has at least two maximum values (maximum value 201 and maximum value 202 in this example).
- the wavelength of the maximum value 201 corresponds to the oscillation wavelength of the laser apparatus 100 (referred to as the first wavelength ⁇ 1).
- the wavelength of the maximum value 201 does not have to exactly match the oscillation wavelength.
- the wavelength having the maximum value 202 (referred to as the second wavelength ⁇ 2) is a wavelength different from the oscillation wavelength.
- the passing wavelength characteristic of this example has a chevron characteristic with each maximum value as the apex, but may have a flat characteristic showing a continuous maximum value in a predetermined wavelength width.
- the filter unit 10 has a first pass band 301 including the first wavelength ⁇ 1 and a second pass band 302 including the second wavelength ⁇ 2.
- FIG. 2 shows an example in which the first wavelength ⁇ 1 is larger than the second wavelength ⁇ 2, the first wavelength ⁇ 1 may be smaller than the second wavelength ⁇ 2.
- each pass band is a band having a transmittance of half or more of the maximum value.
- the first pass band 301 is a band including the first wavelength ⁇ 1 (oscillation wavelength). That is, the first pass band 301 selectively passes the first wavelength component, which is the wavelength component of the oscillation band, among the incident natural emission amplified light or the laser light.
- the second pass band 302 is a band including a second wavelength ⁇ 2 different from the first wavelength ⁇ 1.
- the component of the second wavelength ⁇ 2 contained in the naturally radiated amplified light or the laser light propagating in the path is referred to as a second wavelength component.
- the second pass band 302 selectively passes the second wavelength component, which is a wavelength component different from the oscillation band, among the incident natural emission amplified light or the laser light.
- the filter unit 10 may be one filter provided at one place in the propagation path of the laser light (that is, in the resonator of the laser light), and has two or more filters provided at different places. You may. As an example, both the first pass band 301 and the second pass band 302 may be set in one bandpass filter. In another example, an optical fiber Bragg grating (referred to as an FBG) that selects the first passband 301 and an FBG that selects the second passband 302 may be provided in the propagation path of the laser beam.
- an FBG optical fiber Bragg grating
- the passing wavelength characteristic of the filter unit 10 may have a minimum value of 203 between the two maximum values.
- the minimum value 203 may be a value attenuated by -10 dB or more as compared with the lower maximum value.
- the minimum value 203 may be attenuated by ⁇ 20 dB or more, or may be attenuated by ⁇ 30 dB or more as compared with the maximum value.
- the passing wavelength characteristic of the filter unit 10 may or may not be connected between the two maximum values.
- the connection between the two maximum values is, for example, when the minimum value 203 is 10% or more of the lower maximum value.
- the pass wavelength characteristic of the filter unit 10 may have another component 204 between the first pass band 301 and the second pass band 302.
- Component 204 may be, for example, a linear component.
- the laser light includes a first wavelength component and a second wavelength component in at least a part of the propagation path of the laser light. Since the laser light contains a second wavelength component different from the first wavelength component (oscillation wavelength), oscillation at the first wavelength ⁇ 1 can be induced, and oscillation at the first wavelength ⁇ 1 is stabilized in a short time. be able to.
- FIG. 3 is a diagram illustrating the energy level of the electron of the optical fiber to which Yb is added in the amplification unit 20.
- an example including an optical fiber to which Yb is added is shown, but the laser medium is not limited to this, and an optical fiber to which other rare earths are added may be used, and LINBO3 to which rare earths are added or a fused silica phosphate system.
- a quartz glass-based planar waveguide may be used.
- the excitation level and the laser upper level may be the same, and the energy level is not limited to this.
- the electrons in the amplification unit 20 are in a state of population inversion in which the number of electrons in the upper laser level is larger than that in the lower laser levels 1 and 2.
- Laser light contains various wavelength components due to the transition of electrons in the upper level of the laser to various levels.
- the laser lower level corresponding to the first wavelength ⁇ 1 is the laser lower level 1
- the laser lower level corresponding to the second wavelength ⁇ 2 is the laser lower level 2.
- FIG. 4 is a diagram showing a stimulated emission cross section of the Yb fiber used in the amplification unit 20.
- the horizontal axis is the wavelength and the vertical axis is the cross-sectional area.
- the optical fiber contains Yb is shown, but the material of the optical fiber is not limited to this.
- the first wavelength ⁇ 1 in the filter unit 10 is set to a wavelength whose induced emission cross section is equal to or higher than a certain wavelength in the distribution characteristic of the wavelength component shown in FIG. By selectively passing the first wavelength ⁇ 1 through, it becomes easier to oscillate at the first wavelength ⁇ 1.
- the second wavelength ⁇ 2 in the filter unit 10 is also set to a wavelength whose induced emission cross section is equal to or higher than a certain wavelength in the distribution characteristic of the wavelength component.
- the second wavelength ⁇ 2 may be set to a wavelength in which the cross-sectional area in the distribution characteristic of the wavelength component is larger than that of the first wavelength ⁇ 1.
- FIG. 5 is a conceptual diagram illustrating that the oscillation at the first wavelength ⁇ 1 can be stabilized in a short time by having the second pass band 302.
- the time waveforms of the first wavelength component and the second wavelength component included in the laser light transmitted through the amplification unit 20 are shown separately.
- the electron amount of the laser lower level 2 described in FIG. 3 increases.
- the population inversion between the upper laser level and the lower laser level 2 becomes smaller, and the second wavelength component becomes smaller with time.
- the population inversion is maintained between the upper laser level and the lower laser level 1.
- the first wavelength component is appropriately amplified, and oscillation at the first wavelength is likely to occur in a short time.
- FIG. 6 is a diagram showing the time waveform and wavelength distribution of the excitation laser and the laser beam when the first pass band 301 is provided and the second pass band 302 is not provided.
- the laser light is a laser light output by the laser device 100.
- step S502 Increases the intensity of the excitation laser light in step 501.
- an oscillation component having a high intensity is generated in the laser light (step S502).
- step S503 When the intensity of the excitation laser beam is maintained, a plurality of mode-synchronized pulses are generated in the time waveform (step S503). If the intensity of the excitation laser light is lowered in this state, a mode-synchronized pulse having a predetermined oscillation wavelength remains (step S504).
- the intensity of the excitation laser beam is greatly increased to cause Q-switch oscillation that generates a very high intensity pulse (step). S502).
- the high-intensity pulse is divided into a plurality of pulses to enter a state called multi-pulse oscillation in which one or more pulses exist in the oscillator (step S503).
- step S504 stable single pulse oscillation is realized (step S504). Therefore, it may take several minutes to generate the laser light having a predetermined oscillation wavelength.
- FIG. 7 is a diagram showing the time waveform and wavelength distribution of the excitation laser and the laser beam when the first pass band 301 and the second pass band 302 are provided.
- the second pass band 302 oscillation at the first wavelength ⁇ 1 becomes possible.
- oscillation at the first wavelength ⁇ 1 is started without going through the state of multi-pulse oscillation (S603).
- the first wavelength ⁇ 1 was set to 1040 nm and the second wavelength ⁇ 2 was set to 1030 nm using a Yb fiber, laser light could be generated within 2 seconds on average.
- FIG. 8 is a diagram showing a configuration example of the laser device 100.
- the laser device 100 of this example has an optical transmission unit 101 and a saturable absorption unit 102.
- the optical transmission unit 101 includes a filter unit 10, a long fiber unit 23 that functions as an amplification unit 20, an amplification unit 21, a laser input unit 30, a laser output unit 40, an optical fiber 50, an optical isolator 60, and a coupling unit 70.
- Each component of the optical transmission unit 101 is connected by an optical fiber 50.
- the laser light loops in the optical transmission unit 101.
- the optical transmission unit 101 may be an all-fiber device in which each component is formed of an optical fiber.
- the optical transmission unit 101 of this example is connected to the saturable absorption unit 102 by an optical fiber 50, and laser light reciprocates between the optical transmission unit 101 and the saturable absorption unit 102.
- a non-linear amplification loop mirror (Nonliner Amplifiering Loop Mirror: NALM) is used as the saturable absorption unit 102.
- Excitation laser light is input to the laser input unit 30.
- the laser input unit 30 combines the laser light transmitting the optical transmission unit 101 with the excitation laser light to transmit the optical fiber 50.
- the laser input unit 30 is, for example, a WDM (wavelength division multiplexing) coupler.
- the amplification unit 21 of this example is provided between the laser input unit 30 and the laser output unit 40.
- the space between the configuration A and the configuration B refers to a region from the configuration A to the configuration B in the circumferential direction of the laser beam.
- the amplification unit 21 may have an optical fiber (YDF) to which Yb is added.
- the long fiber portion 23 is provided between the laser input portion 30 and the laser output portion 40.
- the fiber unit 23 of this example is provided between the amplification unit 21 and the laser output unit 40.
- the fiber portion 23 may have a non-polarization holding fiber (Non-PMF). Only one of the fiber portion 23 and the amplification portion 21 may be provided.
- the fiber unit and the amplification unit 21 amplify the intensity of the laser light transmitted through the optical transmission unit 101 by the excitation laser light.
- the arrangement of the long fiber portion 23 and the amplification portion 21 is not limited to the example of FIG.
- An optical isolator 60 that defines the circumferential direction of the laser beam may be provided between the laser input unit 30 and the laser output unit 40.
- the optical isolator 60 of this example is provided between the amplification unit 21 and the long fiber unit 23.
- the laser output unit 40 of this example is arranged between the long fiber unit 23 and the filter unit 10.
- the laser output unit 40 outputs a predetermined ratio of the laser light transmitted through the optical transmission unit 101.
- the laser output unit 40 outputs about 10% to 80% of the passing laser light to the outside as output laser light.
- the lower limit of the ratio of the output laser light to the laser light passing through the laser output unit 40 may be smaller than 10% (for example, 1%). Further, the upper limit of the ratio may be about 90%.
- the remaining laser light is transmitted to the optical transmission unit 101.
- the laser output unit 40 is, for example, an OC (output coupler).
- the filter unit 10 passes the wavelength component of the set pass band among the laser light transmitted through the optical transmission unit 101, and attenuates the wavelength component outside the pass band.
- the filter unit 10 of this example is an optical bandpass filter in which the first pass band 301 and the second pass band 302 described in FIGS. 1 to 7 are set.
- An optical isolator 60 may be provided between the filter unit 10 and the laser output unit 40.
- the coupling unit 70 couples the optical transmission unit 101 and the saturable absorption unit 102.
- the coupling portion 70 of this example separates the laser beam input to the loop of the NALM into a component that propagates the loop clockwise and a component that propagates the loop counterclockwise.
- the coupling portion 70 of this example is arranged between the fiber portion 23 and the laser output portion 40, but the arrangement of the coupling portion 70 is not limited to this.
- the saturable absorption unit 102 receives the laser light that has passed through the laser input unit 30 and absorbs the wavelength component that constitutes the time component of the pulse having a predetermined intensity or less.
- the saturable absorption unit 102 inputs to the optical transmission unit 101 a wavelength component higher than a predetermined intensity of the laser light received from the optical transmission unit 101.
- the saturable absorption unit 102 of this example causes a phase difference between the component propagating clockwise and the component propagating counterclockwise according to the intensity difference.
- the laser light is propagated from the saturable absorption unit 102 to the optical transmission unit 101 with transmission characteristics corresponding to the phase difference between the two components. Therefore, the saturable absorption unit 102 attenuates the relatively low-intensity time component and propagates the relatively high-intensity time component in the clockwise direction of the optical transmission unit 101.
- the saturable absorption unit 102 of this example has an amplification unit 103, an optical fiber 106, and a laser input unit 104. Each component of the saturable absorber 102 is connected in a loop by an optical fiber 106.
- the laser input unit 104 combines the excitation laser light with the laser light transmitted counterclockwise through the saturable absorption unit 102.
- the amplification unit 103 is arranged in a clockwise path from the coupling unit 70 to the laser input unit 104, and amplifies the laser light.
- the amplification unit 103 is, for example, an optical fiber doped with Yb.
- FIG. 9A is a diagram showing an example of the first pass band 301 and the second pass band 302 set in the filter unit 10 of FIG.
- the vertical axis of FIG. 9A shows the ratio of the intensity of the laser light output by the filter unit 10 to the intensity of the laser light input to the filter unit 10. That is, when the intensity is 1, the attenuation in the filter unit 10 is 0 dB.
- the first pass band 301 of this example has a center wavelength (first wavelength) of 1040 nm and a bandwidth of 1.8 nm.
- the second pass band 302 has a center wavelength (second wavelength) of 1030 nm and a bandwidth of 1.5 nm.
- the first pass band 301 has a Gaussian shape and the second pass band 302 has a rectangular shape, but the shapes of the first pass band 301 and the second pass band 302 have a Gaussian shape and a rectangular shape, respectively. Either of the above may be selected.
- FIG. 9B is a diagram showing the wavelength distribution of the laser light output by the laser device 100 when the first pass band 301 and the second pass band 302 shown in FIG. 9A are used.
- the laser light having the wavelength distribution shown in FIG. 9B was obtained instantly (within 5 seconds) after the excitation laser light was applied.
- the laser light having the wavelength distribution shown in FIG. 9B can be obtained about 20 minutes after the excitation laser light is applied. rice field. That is, it can be seen that by setting the second pass band 302, the laser light oscillated at the first wavelength can be obtained instantly.
- the size P2 of the second wavelength component may be 10% or less of the size P1 of the first wavelength component.
- P2 may be 1% or less of P1 and may be 0.1% or less.
- the pass bandwidth of the second pass band 302 may be smaller than the pass bandwidth of the first pass band 301.
- the width of the pass band of the filter unit 10 may be the width of the wavelength band in which the intensity of the wavelength component of the input laser light is half or less. That is, it may be the width of the wavelength band in which the transmittance of the filter unit 10 is 50% or more.
- the pass bandwidth of the second pass band 302 may be 90% or less, 70% or less, or 50% or less of the pass bandwidth of the first pass band 301.
- FIG. 10A is a diagram showing other examples of the first pass band 301 and the second pass band 302.
- the first pass band 301 of this example has a center wavelength (first wavelength) of 1048 nm and a bandwidth of 3.5 nm.
- the second pass band 302 is the same as the example of FIG. 9A.
- FIG. 10B is a diagram showing the wavelength distribution of the laser light output by the laser device 100 when the first pass band 301 and the second pass band 302 shown in FIG. 10A are used.
- the laser light having the wavelength distribution shown in FIG. 10B was obtained.
- the laser light oscillated at the first wavelength could not be obtained.
- FIG. 11A is a diagram showing another example of the first pass band 301 and the second pass band 302.
- the first pass band 301 of this example is the same as the example of FIG. 9A.
- the second pass band 302 has a center wavelength (second wavelength) of 1030 nm and a bandwidth of 1.8 nm. However, the second pass band 302 is attenuated by ⁇ 1.5 dB at the second wavelength. On the other hand, in the first pass band 301, the attenuation at the first wavelength is 0 dB.
- FIG. 11B is a diagram showing the wavelength distribution of the laser light output by the laser device 100 when the first pass band 301 and the second pass band 302 shown in FIG. 11A are used. Also in this example, a laser beam having the wavelength distribution shown in FIG. 11B was obtained when at least about 10 seconds had passed after the excitation laser beam was applied.
- the attenuation rate of the second pass band 302 with respect to the second wavelength component may be larger than the attenuation rate of the first pass band 301 with respect to the first wavelength component.
- the attenuation rate of the second pass band 302 with respect to the second wavelength component may be 90% or less, 70% or less, or 50% or less of the attenuation rate of the first pass band 301 with respect to the first wavelength component. You may. This makes it easier to suppress the second wavelength component in the laser light output from the laser device 100.
- FIG. 12A is a diagram showing another example of the first pass band 301 and the second pass band 302.
- the first pass band 301 of this example is the same as the example of FIG. 9A.
- the second pass band 302 has a center wavelength (second wavelength) of 1030 nm and a bandwidth of 4.6 nm.
- FIG. 12B is a diagram showing the wavelength distribution of the laser light output by the laser device 100 when the first pass band 301 and the second pass band 302 shown in FIG. 12A are used. Also in this example, a laser beam having the wavelength distribution shown in FIG. 12B was obtained when at least about 10 seconds had passed after the excitation laser beam was applied. However, by increasing the bandwidth of the second pass band 302, a part of the laser beam has passed through the second pass band 302. On the other hand, the wavelength component of the laser light that has passed through the first pass band 301 is greatly expanded by the self-phase modulation effect in the laser apparatus 100.
- the bandwidth of the second pass band 302 is preferably 4.6 nm or less.
- the bandwidth of the second pass band 302 is preferably 0.2 nm or more.
- the bandwidth of the second pass band 302 is changed, but even if the bandwidth of the first pass band 301 is changed, the laser beam of the first wavelength can be obtained in the same manner.
- the bandwidth of the first pass band 301 may be 0.8 nm or more.
- the bandwidth of the first pass band 301 may be 50% or more of the second pass band 302.
- FIG. 13A is a diagram showing other examples of the first pass band 301 and the second pass band 302.
- the first pass band 301 of this example is the same as the example of FIG. 9A.
- the second pass band 302 has a center wavelength (second wavelength) of 1033 nm and a bandwidth of 1.5 nm.
- FIG. 13B is a diagram showing the wavelength distribution of the laser light output by the laser device 100 when the first pass band 301 and the second pass band 302 shown in FIG. 13A are used. Also in this example, a laser beam having the wavelength distribution shown in FIG. 13B was obtained when at least about 10 seconds had passed after the excitation laser beam was applied. However, by reducing the wavelength difference between the second pass band 302 and the first pass band 301, the spectral component that has passed through the second pass band 302 has expanded due to the self-phase modulation effect after passing through the first pass band 301. It tends to interfere with the spectral components. Therefore, as shown in FIG. 13B, the noise component is large in the band of 1033 nm to 1040 nm. In the example of FIG. 13A, the second wavelength of the second pass band 302 is changed, but the laser light of the first wavelength can be obtained even if the first wavelength of the first pass band 301 is changed.
- the wavelength difference between the center wavelength of the first pass band 301 (first wavelength) and the center of the second pass band 302 (second wavelength) is preferably 9 nm or more.
- the wavelength difference may be 10 nm or more.
- the value obtained by subtracting half of the bandwidth of each pass band from the difference in the center wavelength may be 7.35 nm.
- the wavelength difference between the first wavelength and the second wavelength is preferably 18 nm or less.
- the wavelength difference may be 15 nm or less, and may be 12 nm or less.
- the value obtained by subtracting half of the bandwidth of each pass band from the difference in the center wavelength may be 16.35 nm or less.
- FIG. 14A is a diagram showing another example of the first pass band 301 and the second pass band 302.
- the second pass band 302 of this example is the same as the example of FIG. 9A.
- the first pass band 301 has a center wavelength (first wavelength) of 1040 nm and a bandwidth of 1.8 nm. However, the first pass band 301 is attenuated by -2.8 dB at the first wavelength.
- FIG. 14B is a diagram showing the wavelength distribution of the laser light output by the laser device 100 when the first pass band 301 and the second pass band 302 shown in FIG. 14A are used. Also in this example, a laser beam having the wavelength distribution shown in FIG. 14B was obtained when at least about 10 seconds had passed after the excitation laser beam was applied. However, by increasing the attenuation factor of the first pass band 301, the relative size of the second wavelength component (1030 nm) is larger than that in the example of FIG. 9B. Therefore, the attenuation rate of the first pass band 301 at the first wavelength may be 50% or more, 70% or more, or 90% or more of the attenuation rate of the second pass band 302 at the second wavelength. There may be.
- the first pass band 301 and the second pass band 302 are preferably bands according to the material of the optical fiber of the amplification unit 20. That is, as described with reference to FIG. 4, it is preferable that each pass band is set in a wavelength band in which the intensity of the laser light generated by the optical fiber is equal to or higher than a certain level.
- both the first wavelength and the second wavelength are 1020 nm or more and 1050 nm or less.
- the first wavelength and the second wavelength are preferably 1530 nm or more, 1555 nm or less, or 1555 nm or more and 1600 nm or less.
- One wavelength may be 1530 nm or more and 1555 nm or less, and the other wavelength may be 1555 nm or more and 1600 nm or less.
- the first wavelength and the second wavelength are preferably 1080 nm or more and 1080 nm or less or 888 nm or more and 914 nm or less.
- One wavelength may be 1080 nm or more and 1080 nm or less, and the other wavelength may be 888 nm or more and 914 nm or less.
- the first wavelength and the second wavelength are preferably 1960 nm or more, 2020 nm or less, or 1860 nm or more, and 1960 nm or less.
- One wavelength may be 1960 nm or more and 2020 nm or less, and the other wavelength may be 1860 nm or more and 1960 nm or less.
- the first pass band 301 and the second pass band 302 may be variable. That is, the center wavelength and bandwidth of each passband may be variable.
- the center wavelength (first wavelength) of the first pass band 301 may be changed according to the wavelength of the laser light to be generated.
- the filter unit 10 increases the bandwidth difference between the center wavelength (first wavelength) of the first pass band 301 and the center wavelength (second wavelength) of the second pass band 302, and the bandwidth of the first pass band 301. May be increased. Increasing the wavelength difference makes it difficult to induce the first wavelength component, but increasing the bandwidth of the first passband 301 can promote oscillation at the first wavelength.
- the bandwidth of the second pass band 302 may be reduced.
- the ratio of the second wavelength component interfering with the first pass band 301 increases, but by reducing the bandwidth of the second pass band 302, the interference can be suppressed.
- the attenuation rate at the second wavelength of the second pass band 302 may be increased. This also suppresses the interference.
- FIG. 15 is a diagram showing another configuration example of the filter unit 10.
- the filter unit 10 of this example is connected to the loop-shaped optical fiber 50 via the coupling unit 80.
- the coupling unit 80 propagates the laser light that orbits the loop-shaped optical fiber 50 to the filter unit 10, and propagates the light from the filter unit 10 to the loop-shaped optical fiber 50.
- the filter unit 10 of this example has a first filter unit 10-2 that selects and propagates light in the first pass band 301 and a second filter unit 10-2 that selects and propagates light in the second pass band 302. Has.
- the first filter unit 10-1 and the second filter unit 10-2 of this example are FBGs.
- the first filter unit 10-1 and the second filter unit 10-2 are provided in series with the coupling unit 80. Which of the first filter unit 10-1 and the second filter unit 10-2 may be provided near the coupling unit 80.
- FIG. 16 is a diagram showing another configuration example of the optical transmission unit 101.
- the optical transmission unit 101 of this example is different from the optical transmission unit 101 described with reference to FIG. 8 or 15 in that it does not have the amplification unit 20, the amplification unit 21, the laser input unit 30, and the optical isolator 60.
- Other structures are similar to the example of FIG. 8 or FIG.
- the optical fiber 50 may function as the amplification unit 20 or the amplification unit 21.
- the filter unit 10 of this example is arranged between the laser output unit 40 and the coupling unit 70.
- the filter unit 10 may be connected to the optical fiber 50 via the coupling unit 80, as in the example of FIG.
- the saturable absorption unit 102 was NALM, but the saturable absorption unit 102 may use an absorber such as a semiconductor saturable absorption mirror (SESAM). Further, a unsaturated absorption mechanism using a non-linear optical loop mirror (Nonliner Optical Loop Mirror; NOLM) or a non-linear polarization rotation (NPR) may be used.
- SESAM semiconductor saturable absorption mirror
- NOLM non-linear optical loop mirror
- NPR non-linear polarization rotation
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Abstract
Description
特許文献1 US8416817号
特許文献2 US7940816号
Claims (13)
- レーザー光を生成するレーザー装置であって、
前記レーザー光が伝搬する経路に設けられ、前記レーザー光を増幅して出力する増幅部と、
前記経路に設けられ、通過波長特性が少なくとも2つ以上の波長において極大値を有し、前記通過波長特性に応じて、光の波長成分を選択的に通過させるフィルタ部と
を備えるレーザー装置。 - 前記フィルタ部の前記通過波長特性は、いずれかの前記極大値の波長を含み、前記レーザー光の発振波長の波長成分である第1波長成分を選択的に通過させる第1通過帯域と、いずれかの前記極大値の波長を含み、前記発振波長とは異なる波長成分である第2波長成分を選択的に通過させる第2通過帯域とを有する
請求項1に記載のレーザー装置。 - 前記レーザー装置が出力する前記レーザー光において、前記第2波長成分の大きさは、前記第1波長成分の10%以下である
請求項2に記載のレーザー装置。 - 前記第2通過帯域の幅は、前記第1通過帯域の幅よりも狭い
請求項2または3に記載のレーザー装置。 - 前記増幅部はYbファイバーを含み、
前記第1通過帯域の中心波長および前記第2通過帯域の中心波長が、ともに1020nm以上、1100nm以下である
請求項2から4のいずれか一項に記載のレーザー装置。 - 前記増幅部はErファイバーを含み、
前記第1通過帯域の中心波長および前記通過帯域の第2中心波長が、ともに1530nm以上、1555nm以下もしくは1555nm以上、1600nm以下である
請求項2から4のいずれか一項に記載のレーザー装置。 - 前記増幅部はNdファイバーを含み、
前記第1通過帯域の中心波長および前記第2通過帯域の中心波長が、ともに1060nm以上、1080nm以下もしくは888nm以上、914nm以下である
請求項2から4のいずれか一項に記載のレーザー装置。 - 前記増幅部はTmファイバーを含み、
前記第1通過帯域の中心波長および前記第2通過帯域の中心波長が、ともに1960nm以上、2020nm以下もしくは1860nm以上、1960nm以下である
請求項2から4のいずれか一項に記載のレーザー装置。 - 前記第1通過帯域および前記第2通過帯域は可変であり、
前記第1通過帯域の中心波長および前記第2通過帯域の中心波長の波長差を増加させた場合に、前記第1通過帯域の幅を増加させる
請求項2から8のいずれか一項に記載のレーザー装置。 - 前記第1通過帯域および前記第2通過帯域は可変であり、
前記第1通過帯域の中心波長および前記第2通過帯域の中心波長の波長差を減少させた場合に、前記第2通過帯域の幅を減少させるか、または、前記第2通過帯域における減衰率を増加させる
請求項2から8のいずれか一項に記載のレーザー装置。 - 前記レーザー光を伝搬する偏波保持ファイバーを更に備える
請求項1から10のいずれか一項に記載のレーザー装置。 - 可飽和吸収体として機能するNALMを更に備える
請求項1から11のいずれか一項に記載のレーザー装置。 - レーザー光をモード同期させるモード同期方法であって、
前記レーザー光が伝搬する経路において、少なくとも2つ以上の波長において極大値を有する通過波長特性に応じて、光の波長成分を選択的に通過させて、前記レーザー光をモード同期させるモード同期方法。
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CN202180038897.5A CN115699481A (zh) | 2020-06-05 | 2021-06-04 | 选择性使用两个不同波长的锁模方法、以及使用了该方法的激光装置 |
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- 2021-06-04 JP JP2022528923A patent/JPWO2021246531A1/ja active Pending
- 2021-06-04 KR KR1020227043563A patent/KR20230009975A/ko not_active Application Discontinuation
- 2021-06-04 WO PCT/JP2021/021465 patent/WO2021246531A1/ja unknown
- 2021-06-04 EP EP21817936.4A patent/EP4160832A4/en active Pending
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2022
- 2022-12-04 US US18/061,471 patent/US20230099615A1/en active Pending
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Also Published As
Publication number | Publication date |
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CN115699481A (zh) | 2023-02-03 |
KR20230009975A (ko) | 2023-01-17 |
JPWO2021246531A1 (ja) | 2021-12-09 |
US20230099615A1 (en) | 2023-03-30 |
EP4160832A1 (en) | 2023-04-05 |
EP4160832A4 (en) | 2023-12-13 |
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