JP2004146681A - Fiber for light amplification, light amplifier, light source device, optical treatment device, and exposure device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fiber for light amplification and a light amplifier capable of realizing the high power of an output light, the suppression of the generation of any non-linear optical phenomenon and compact storage. <P>SOLUTION: An excitation light outputted from an excitation light source 50 is supplied through an optical coupler 40 and a fiber 20 for connection to a fiber 10 for light amplification. A light inputted to an input terminal 1a is made incident through the optical coupler 40 and the fiber 20 for connection to the fiber 10 for light amplification, and light-amplified by the fiber 10 for light amplification. The light-amplified light is transmitted through the fiber 30 for connection, and outputted from an output terminal 1b. The fiber 10 for light amplification is provided with a core area added with rare earth elements and a clad area surrounding the core area whose refractive index is lower than the core area, and the outer diameter of the core area is set so as to be 10 μm or more to 30 μm or less, and the outer diameter of the clad area is set so as to be 75 μm or more to 200 μm or less, and the specific refractive index difference of the core area to the clad area is set so as to be 0.5% or more to 2.0% or less. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an optical amplification fiber capable of optically amplifying light and an optical amplification device.
[0002]
[Prior art]
The optical amplifying device uses an optical amplifying fiber in which a rare earth element is added to a core region as an optical amplifying medium, and supplies excitation light to the optical amplifying fiber, thereby amplifying the signal light in the optical amplifying fiber. can do. For example, an optical amplifying device using an optical amplifying fiber to which an Er element is added as an optical amplifying medium can optically amplify a signal light in a wavelength band of 1.55 μm generally used in an optical communication system. It is provided in the optical repeater of the system.
[0003]
On the other hand, use of such an optical amplifier as a high-output light source for generating ultraviolet light by wavelength conversion is also being studied. For example, in the technique described in Non-Patent Document 1, high-output infrared light output from an optical amplifier is incident on a nonlinear optical crystal, and a harmonic is generated in the nonlinear optical crystal. This is to output ultraviolet light from the linear optical crystal.
[0004]
[Non-patent document 1]
Tomoko Otsuki, "High Efficiency Ultraviolet Light Source by Fiber Amplifier and Wavelength Conversion," Laser Research, Vol. 29, No. 2, pp. 94-98, February 2001
[0005]
[Problems to be solved by the invention]
In the applications described in Non-Patent Document 1, the optical amplifying device has a large output optical power, suppresses the occurrence of nonlinear optical phenomena in the optical amplifying fiber, and has a compact optical amplifying fiber. It is required that storage be possible.
[0006]
However, when trying to increase the output light power, the nonlinear optical phenomenon is likely to occur in the optical amplification fiber. That is, there is a trade-off between increasing the power of the output light and suppressing the occurrence of the nonlinear optical phenomenon.
[0007]
To suppress the occurrence of nonlinear optical phenomena, the effective core area of the optical amplification fiber may be increased. However, the bending loss of the optical amplification fiber increases, and the optical amplification fiber becomes compact. Storage becomes difficult. That is, there is a trade-off between suppression of the nonlinear optical phenomenon and compact storage of the optical amplification fiber.
[0008]
SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has an optical amplification fiber capable of increasing output light power, suppressing the occurrence of non-linear optical phenomena, and compactly storing the light. It is an object to provide a light amplification device and a light source device using a fiber, and a phototherapy device and an exposure device using the light source device.
[0009]
[Means for Solving the Problems]
The optical amplification fiber according to the present invention has a core region to which a rare earth element is added, and a cladding region surrounding the core region and having a lower refractive index than the core region, and the outer diameter of the core region is 10 μm or more and 30 μm or less. The outer diameter of the cladding region is 75 μm or more and less than 200 μm, and the relative refractive index difference of the core region with respect to the cladding region is 0.5% or more and 2.0% or less. Preferably, the outer diameter of the core region is 15 μm or more and 27 μm or less, the outer diameter of the cladding region is 110 μm or more and less than 150 μm, or the relative refractive index difference of the core region with respect to the cladding region is 0.7% or more. 1.5% or less. The optical amplifying fiber thus configured can increase the power of output light, suppress the occurrence of non-linear optical phenomena, and store it compactly.
[0010]
In the optical amplification fiber according to the present invention, the rare earth element added to the core region is preferably an Er element, and the concentration of the Er element added to the core region is 800 wt. It is preferably at least ppm, and the absorption loss peak near a wavelength of 1530 nm is preferably at least 20 dB / m and at most 80 dB / m. In this case, the optical amplifying fiber can amplify and output the light in the wavelength band of 1.5 to 1.6 μm.
[0011]
An optical amplifying device according to the present invention includes the optical amplifying fiber according to the present invention for optically amplifying light, and pumping light supply means for supplying pumping light to the optical amplifying fiber. According to this optical amplification device, the excitation light is supplied to the optical amplification fiber by the excitation light supply means, and the light is amplified in the optical amplification fiber.
[0012]
In the optical amplifying device according to the present invention, a connecting fiber is provided between the input fiber provided on the light incident side of the optical amplifying fiber and the optical amplifying fiber, and the mode field diameter of the connecting fiber has an Preferably, it is larger than the mode field diameter of the optical fiber and smaller than the mode field diameter of the optical amplification fiber. Further, a connection fiber is provided between the emission fiber provided on the light emission side of the optical amplification fiber and the light amplification fiber, and the mode field diameter of the connection fiber is larger than the mode field diameter of the emission fiber. Preferably, it is large and smaller than the mode field diameter of the optical amplification fiber. In this case, the change in the mode field diameter at any end of the optical amplification fiber is stepwise, and the loss of the amplified light or the pump light due to the discontinuity of the mode field diameter is reduced, Also in this respect, high power light can be output.
[0013]
In the optical amplification device according to the present invention, it is preferable that the optical amplification fiber is wound in a coil shape, and the minimum bending radius of the optical amplification fiber is 15 mm or more. In this case, the optical amplifier becomes compact. Further, at this time, since the optical amplification fiber is the one according to the present invention, an increase in bending loss is suppressed, and the output optical power becomes stable and high.
[0014]
A light source device according to the present invention is a light source device including a signal generator that generates an electric signal, a semiconductor laser that generates laser light based on the electric signal, and an optical fiber amplifier that amplifies laser light from the semiconductor laser. An optical fiber amplifier includes the optical amplification fiber according to the present invention. Further, the electric signal is pulse-like, the semiconductor laser generates pulsed light, and it is preferable that another optical fiber amplifier is provided before the optical fiber amplifier.
[0015]
The light treatment device according to the present invention includes the light source device according to the present invention described above, a wavelength converter that converts irradiation light emitted from an outlet of the light source device into treatment irradiation light having a predetermined wavelength, and a wavelength converter. And an irradiation optical system for guiding the converted irradiation light to the treatment site for irradiation.
[0016]
The exposure apparatus according to the present invention is provided with the light source device according to the present invention described above, a wavelength converter that converts irradiation light emitted from an outlet of the light source device into irradiation light having a predetermined wavelength, and a predetermined exposure pattern. A mask supporting unit for holding the photomask, an object holding unit for holding an exposure object, and an illumination optical system for irradiating the irradiation mask converted by the wavelength converter to the photomask held by the mask supporting unit. And a projection optical system for irradiating the exposure object held by the object holding unit with the irradiation light irradiated to the photomask via the illumination optical system and passing therethrough.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same elements will be denoted by the same reference symbols, without redundant description.
[0018]
(Embodiment of optical amplification device and optical amplification fiber)
First, an embodiment of an optical amplification device and an optical amplification fiber according to the present invention will be described. FIG. 1 is a configuration diagram of an optical amplification device 1 according to the present embodiment. The optical amplifying device 1 shown in FIG. 1 amplifies light input to an input terminal 1a and outputs the optically amplified light from an output terminal 1b. , A connection fiber 30, an optical coupler 40, and an excitation light source 50.
[0019]
The optical amplification fiber 10 is mainly composed of quartz glass, and has a core region to which a rare earth element is added and a cladding region surrounding the core region. In particular, in the optical amplification fiber 10, it is preferable that an Er element as a rare earth element is added to the core region, and the addition concentration of the Er element in the core region is 800 wt. It is preferably at least ppm, and the absorption loss peak near a wavelength of 1530 nm is preferably at least 20 dB / m and at most 80 dB / m. It is also preferable that the optical amplification fiber 10 has an Al element or a La element co-doped in the core region. In addition, as described later, the mode field diameter of the optical amplification fiber 10 is larger than a normal one. The optical amplification fiber 10 is wound in a coil shape and has a minimum bending radius of 15 mm or more.
[0020]
In the optical amplification fiber 10, a connection fiber 20 is fusion-spliced to the input end 1a side, and the output end (generally, a standard single mode optical fiber) of the optical coupler 40 is connected through the connection fiber 20. It is connected. The connection fiber 20 is provided between the optical amplification fiber 10 and the output end of the optical coupler 40. The mode field diameter of the connection fiber 20 is larger than the mode field diameter at the output end of the optical coupler 40 and smaller than the mode field diameter of the optical amplification fiber 10.
[0021]
The optical amplification fiber 10 has a connection fiber 30 fusion-spliced on the output end 1b side, and is connected to the output end 1b via the connection fiber 30. The connection fiber 30 is provided between the optical fiber (generally a standard single mode optical fiber) connected to the output end 1 b and the optical amplification fiber 10. The mode field diameter of the connection fiber 30 is larger than the mode field diameter of the optical fiber connected to the output end 1b, and smaller than the mode field diameter of the optical amplification fiber 10.
[0022]
The optical coupler 40 outputs the light input to the input terminal 1 a to the optical amplification fiber 10, and also outputs the excitation light output from the excitation light source 50 to the optical amplification fiber 10. The excitation light source 50 outputs excitation light having a wavelength capable of exciting the rare earth element added to the optical amplification fiber 10. The optical coupler 40 and the excitation light source 50 constitute excitation light supply means for supplying excitation light to the optical amplification fiber 10. For example, when the rare earth element added to the optical amplification fiber 10 is an Er element, the wavelength of the excitation light is around 1.48 μm or around 0.98 μm, and the wavelength of the light to be amplified is 1.5 to 1.5 μm. It is a 1.6 μm band.
[0023]
This optical amplifier 1 operates as follows. The excitation light output from the excitation light source 50 is supplied to the optical amplification fiber 10 via the optical coupler 40 and the connection fiber 20, and excites the rare earth element added to the optical amplification fiber 10. The light input to the input terminal 1a enters the optical amplification fiber 10 via the optical coupler 40 and the connection fiber 20, and is optically amplified in the optical amplification fiber 10. The optically amplified light is output from the output end 1b via the connection fiber 30. In this embodiment, since the connection fibers 20 and 30 are used, the change in the mode field diameter at both ends of the optical amplification fiber 10 becomes stepwise, which is caused by the discontinuity of the mode field diameter. The loss of the amplified light or the pump light is reduced, and in this regard, light with high power can be output.
[0024]
FIG. 2 is an explanatory diagram of the optical amplification fiber 10 according to the present embodiment. FIG. 1A shows a cross section of the optical amplification fiber 10 when cut along a plane perpendicular to the optical axis, and FIG. 1B shows a refractive index profile of the optical amplification fiber 10. As shown in this figure, the optical amplification fiber 10 has a core region 11 to which a rare earth element is added, and a cladding region 12 surrounding the core region 11 and having a lower refractive index than the core region 11. The outer diameter 2a of the core region 11 is 10 μm or more and 30 μm or less, the outer diameter 2b of the cladding region 12 is 75 μm or more and less than 200 μm, and the relative refractive index difference Δ of the core region 11 with respect to the cladding region 12 is 0.5%. Not less than 2.0%. Further, the outer diameter 2a of the core region 11 is preferably 15 μm or more and 27 μm or less, the outer diameter 2b of the cladding region 12 is preferably 110 μm or more and less than 150 μm, and the core region 11 It is preferable that the relative refractive index difference Δ be 0.7% or more and 1.5% or less. The optical amplification fiber 10 according to the present embodiment has such a configuration, so that it is possible to increase the power of the output light, suppress the occurrence of nonlinear optical phenomena, and compactly store the light. As described above, even if the optical amplification fiber 10 is wound in a coil shape, the bending loss is sufficiently small if the minimum bending radius is 15 mm or more.
[0025]
FIG. 3 is a configuration diagram of an evaluation system 100 that evaluates the optical amplification device 1 and the optical amplification fiber 10 according to the present embodiment. The evaluation system 100 shown in the figure includes a DFB laser light source 110, a preamplifier 120, a lens 131, a quarter-wave plate 141, a half-wave plate 142, a filter 151, a lens 132, a lens 133, a filter 152, and a photodetector. 140 are provided in order. The evaluation system 100 amplifies light output from the DFB laser light source 110 by a preamplifier 120 and collimates the light by a lens 131. After adjusting the polarization state of the collimated light with the ４ wavelength plate 141 and the 波長 wavelength plate 142, the evaluation system 100 allows the filter 151 to transmit only light of a specific wavelength component, and transmits the transmitted light to a lens. The light is condensed by 132 and input to the input terminal of the optical amplifier 1. Then, the evaluation system 100 collimates the light output from the output end of the optical amplifying device 1 by the lens 133, transmits only the light of the specific wavelength component by the filter 152, and determines the power of the transmitted light by the photodetector 140. Is detected by
[0026]
FIG. 4 is a table summarizing the data of each of the examples and comparative examples of the optical amplification fiber 10 according to the present embodiment. In each of the optical amplification fibers of the example and the comparative example, the core region 11 is doped with an Er element, the outer diameter 2b of the cladding region is 125 μm, and the length is 2 m. In these optical amplification fibers, glass particles containing Ge as a main component and containing quartz glass are deposited on the inner wall of a glass tube by an MCVD method, and then Er and Al elements are added by a solution impregnation method, and this is added to a transparent glass. The optical fiber preform was manufactured by drawing and solidifying the optical fiber preform. This figure shows the outer diameter 2a of the core region, the relative refractive index difference Δ, the concentration of Er added, the absorption loss peak α, and the maximum output peak power for each of the example and the comparative example. The maximum output peak power was evaluated using the evaluation system 100 shown in FIG. The wavelength of the excitation light was 1.48 μm.
[0027]
The optical amplification fiber of the comparative example is a single mode optical fiber having a normal core diameter, the outer diameter of the core region is 6.2 μm, the relative refractive index difference Δ is 1.1%, and the concentration of Er added. Is 1500 wt. ppm, and the absorption loss peak α near the wavelength of 1530 nm was 27.1 dB / m. In the optical amplifying fiber of the embodiment, the outer diameter 2a of the core region is larger than usual and 13 μm, the relative refractive index difference Δ is 1.2%, and the Er added concentration is 1500 wt. ppm, and the absorption loss peak α near the wavelength of 1530 nm was 37.0 dB / m.
[0028]
FIG. 5 is a graph showing the relationship between the pump power and the output peak power in the optical amplification fibers of the example and the comparative example. In the optical amplifying fiber of the comparative example, as the pumping power is increased, the generation of noise light due to the nonlinear optical phenomenon becomes remarkable, and the power distribution to the noise light increases. Therefore, in the optical amplifying fiber of the comparative example, even when the pumping power was larger than about 1 W, the output peak power tended to be saturated at about 5 kW. On the other hand, in the optical amplifying fiber of the example, when the pumping power was 4 W or more, the output peak power was 15 kW or more, and the maximum output peak power was 24 kW.
[0029]
The efficiency η of noise light generation due to nonlinear optical phenomena is proportional to the square of the fiber length L and inversely proportional to the square of the effective core area. In many cases, the Er element-doped optical amplification fiber is used with the absorption length product (product of the absorption loss peak α and the fiber length L) caused by the Er element being set to a predetermined value. The effective core area is proportional to the square of the mode field diameter MFD. In this case, the nonlinear noise light generation efficiency η is 1 / (α ² × MFD ⁴ )
Is proportional to
[0030]
FIG. 6 is a graph showing the relationship between the core diameter 2a and the nonlinear noise light generation efficiency η for each value of the relative refractive index difference Δ. FIG. 7 is a graph showing the relationship between the relative refractive index difference Δ and the nonlinear noise light generation efficiency η for each value of the core diameter 2a. In each figure, the nonlinear noise light generation efficiency η is shown as a relative value based on the value in the optical amplification fiber of the comparative example. As can be seen from these figures, when the core diameter 2a is increased, the nonlinear noise light generation efficiency η can be reduced to about 1/10 to 1/100. In order to suppress the noise light generation level at which there is no practical problem, the relative value of the nonlinear noise light generation efficiency η needs to be 0.4 or less (more preferably 0.3 or less). The core outer diameter 2a needs to be 12 μm or more (more preferably 15 μm or more), and the relative refractive index difference Δ needs to be 2% or less (more preferably 1.5% or less). is there.
[0031]
The optical amplifying fiber having a relative refractive index difference Δ of greater than 0.7% showed no fluctuation or reduction in output power even when housed in a coiled state with a bending radius of 15 mm. Even if the optical amplification fiber having a relative refractive index difference Δ of less than 0.7% was stored in a state of being wound in a coil shape having a bending radius of 50 mm or more, no fluctuation or reduction in output power was observed. However, in the optical amplifying fiber having the relative refractive index difference Δ of less than 0.5%, even in a state where it is kept in a substantially linear state, a fluctuation or a decrease in the output power was observed only by applying a slight vibration. . From the above, in order to stabilize the output power, the relative refractive index difference Δ is preferably 0.5% or more, and the relative refractive index difference Δ is more preferably 0.7% or more. It turns out that it is suitable.
[0032]
Similarly, when the cladding outer diameter 2b is smaller than 110 μm, the output power fluctuates greatly when the optical amplification fiber is coiled. When the clad outer diameter 2b is less than 150 μm, it becomes easy to fusion splice this optical amplification fiber with another optical fiber having a usual clad outer diameter of 125 μm.
[0033]
FIG. 8 is a graph showing the relationship between the core diameter 2a and the number of propagable modes for each value of the relative refractive index difference Δ. The optical amplifying fiber having 30 or less propagating modes did not show any change or decrease in output power even when housed in a coil shape with a bending radius of 15 mm. Even if the optical amplifying fiber having more than 30 propagable modes is housed in a coil shape having a bending radius of 50 mm or more, no fluctuation or decrease in output power is observed. However, in the optical amplifying fiber having more than 200 modes that can be propagated, the output power fluctuated or decreased even when a slight vibration was applied, even in a state where it was maintained in a substantially linear state. From the above, it can be seen that for stabilization of output power, the number of propagable modes is preferably 200 or less, and more preferably 130 or less. Further, from this, it is understood that the core diameter 2a is preferably 30 μm or less, and the core diameter 2a is more preferably 27 μm or less.
[0034]
The optical amplifying device 1 shown in FIG. 1 was constructed using the same fiber as the optical amplifying fiber of the above embodiment, and the performance of the optical amplifying device 1 was evaluated. The used optical amplification fiber 10 had 50 propagable modes. The connection fiber 20 provided between the optical amplification fiber 10 and the optical coupler 40 had a core diameter of 18 μm, a relative refractive index difference of 0.6%, and 50 propagating modes. The power of the pump light having a wavelength of 1.48 μm was 6 W, and stable output pulse light having a peak output power of about 20 kW or more was obtained.
[0035]
(Embodiment of light source device)
Next, an embodiment of the light source device according to the present invention will be described. FIG. 9 is a configuration diagram of a light source device 200 according to the present embodiment. The light source device 200 includes the optical amplification fiber according to the above-described embodiment, and is a pulse light source that outputs pulse light.
[0036]
The pulse light source 200 according to this embodiment includes a pulse generator 201 that generates a rectangular electric pulse signal, a laser diode 202 that generates a rectangular optical pulse based on the electric pulse signal, a polarization controller 203, Erbium-doped fiber amplifier (EDFA) 204, a band-pass filter 205 for removing ASE (noise) light, and a second erbium-doped fiber amplifier 206 including the optical amplification optical fiber according to the above-described embodiment. It has.
[0037]
In the pulse light source 200, a rectangular electric pulse signal generated by a pulse generator 201 is converted into a rectangular light pulse by a laser diode 202. The optical pulse output from the laser diode 202 is input to a first erbium-doped fiber amplifier (EDFA) 204 via a polarization controller 203, amplified, and output as amplified pulse light. The amplified pulse light from the first erbium-doped fiber amplifier 204 has ASE (noise) light removed by a band-pass filter 205 and is input to a second erbium-doped fiber amplifier 206 according to the present embodiment and amplified. Pulse light having a high peak power is output.
[0038]
According to the pulse light source 200 of this embodiment, since the optical amplifying fiber according to the present embodiment is used, the occurrence of the nonlinear optical phenomenon can be suppressed, and a high-output pulsed light can be obtained.
[0039]
Hereinafter, an embodiment of the phototherapy apparatus and the exposure apparatus of the present invention using the pulse light source 200 will be described.
[0040]
(Embodiment of phototherapy device)
Next, an embodiment of the phototherapy device according to the present invention will be described below with reference to FIGS. The phototherapy device according to the present embodiment is configured using the above-described pulse light source 200 according to the present embodiment. This phototherapy device irradiates a cornea with laser light to perform ablation of the surface (PRK: Photorefractive Keratectomy) or ablation inside the incised cornea (LASIK: Laser Intrastromal Keratomileesis) to correct the curvature or irregularity of the cornea. This is a device for performing treatment such as astigmatism.
[0041]
FIG. 10 is a schematic diagram illustrating a configuration of the phototherapy device 300 according to the present embodiment. As shown in this figure, the phototherapy device 300 basically includes the above-described pulse light source 200 and a laser beam amplified and output by the pulse light source 200 in a device housing 351 having a desired wavelength. A wavelength conversion device 360 that converts the laser light into laser light, an irradiation optical device 370 that guides the laser light whose wavelength has been converted by the wavelength conversion device 360 to the surface (treatment site) of the cornea HC of the eye EY and irradiates the laser light, and observes the treatment site. And an observation optical device 380 for performing the measurement. The base unit 352 of the device housing 351 is disposed on the XY moving table 353, and the entire device housing 351 is moved by the XY moving table 353 in the direction of arrow X in FIG. It is possible to move in the Y direction perpendicular to the paper surface.
[0042]
FIG. 11 is a schematic diagram illustrating a configuration of a wavelength conversion device 360 included in the phototherapy device 300. The pulse light source 200 has the configuration as described above, and the laser light output from the output end 347 of the pulse light source 200 has a desired wavelength in the wavelength conversion device 360 (in this device, the wavelength is 193 nm suitable for corneal treatment, and an ArF excimer laser (The same wavelength as the light). A fundamental wave having a predetermined wavelength (1.544 μm in this embodiment) emitted from the output end 347 of the pulse light source 200 is wavelength-converted into an eighth harmonic (harmonic) using a non-linear optical crystal, and is converted into an ArF excimer. An example of a configuration for generating 193 nm ultraviolet light having the same wavelength as a laser is shown. The fundamental wave having a wavelength of 1.544 μm (frequency ω) output from the output terminal 347 is transmitted through the nonlinear optical crystals 361, 362, and 363 from left to right in the figure and output. Note that condenser lenses 364 and 365 are provided between the nonlinear optical crystals 361, 362 and 363 as shown in the figure.
[0043]
When these fundamental waves pass through the nonlinear optical crystal 361, the second harmonic generation generates a double wave of the frequency ω of the fundamental wave, that is, a double wave of a frequency 2ω (the wavelength is ７７ of 772 nm). The generated second harmonic travels rightward and enters the next nonlinear optical crystal 362. Here, the second harmonic is generated again, and a fourth harmonic having a frequency 4ω (wavelength is 1/4 of 386 nm) which is twice the frequency 2ω of the incident wave, that is, four times the fundamental wave is generated. The generated fourth harmonic further proceeds to the right non-linear optical crystal 363, where the second harmonic is generated again, and has a frequency 8ω twice the frequency 4ω of the incident wave, ie, eight times the fundamental wave. A harmonic (wavelength is 1/8 of 193 nm) is generated.
[0044]
As the nonlinear optical crystal used for the wavelength conversion, for example, a non-linear optical crystal 361 for converting a fundamental wave to a second harmonic wave includes LiB. ₃ O ₅ The (LBO) crystal is converted to a non-linear optical crystal 362 for converting a second harmonic to a fourth harmonic by using LiB. ₃ O ₅ The non-linear optical crystal 363 for converting the (LBO) crystal from the fourth harmonic to the eighth harmonic has Sr. ₂ Be ₂ B ₂ O ₇ (SBBO) crystals are used respectively. Here, in order to convert a fundamental wave to a second harmonic wave using an LBO crystal, an angle shift between the fundamental wave and the second harmonic in a method of adjusting the temperature of the LBO crystal for phase matching for wavelength conversion ( Since Walk-off does not occur, conversion to a second harmonic wave can be performed with high efficiency, and the generated second harmonic wave is advantageous because it is not subjected to beam deformation due to Walk-off.
[0045]
The laser light having a wavelength of 193 nm (laser light having the same wavelength as that of the ArF excimer laser light), which is wavelength-converted and output by the wavelength conversion device 360 in this manner, is guided to the surface of the cornea HC of the eye EY and irradiated thereon. The irradiation optical device 370 and the observation optical device 380 to be performed will be described with reference to FIG. In the pulse light source 200, the solid-state laser is composed of a DFB semiconductor laser or a fiber laser having an oscillation wavelength in the range of 1.51 μm to 1.59 μm. The laser light having the wavelength is converted into a laser light having the eighth harmonic within the range of 189 nm to 199 nm and output. As described above, this laser light is a laser light having substantially the same wavelength as the ArF excimer laser light, but the repetition frequency of the pulse oscillation is as high as 100 kHz.
[0046]
FIG. 12 is a schematic diagram showing the configuration of the irradiation optical device 370 and the observation optical device 380 that constitute the phototherapy device 300. The irradiation optical device 370 is provided with a condensing lens 371 for condensing laser light having a wavelength of 193 nm obtained by wavelength-converting the light from the pulse light source 200 by the wavelength converter 360 into a narrow beam, and condensing light in this manner. And a dichroic mirror 372 for reflecting the beam-shaped laser beam and irradiating the surface of the cornea HC of the eye EY to be treated. As a result, the surface of the cornea HC is irradiated with laser light as spot light, and the portion is evaporated. At this time, the entire device housing 351 is moved in the X and Y directions by the XY movement table 353 to scan and move the laser light spot irradiated on the surface of the cornea HC, and ablation of the corneal surface is performed. Treatment of myopia, astigmatism, hyperopia, etc.
[0047]
Such treatment is performed by an operator such as an ophthalmologist controlling the operation of the XY movement table 353 while visually observing the observation optics via the observation optical device 380. The observation optical device 380 includes an illumination lamp 385 that illuminates the surface of the cornea HC of the eyeball EY to be treated, and an objective lens that receives light from the cornea HC illuminated by the illumination lamp 385 through the dichroic mirror 372. 381, a prism 382 that reflects light from the objective lens 381, and an eyepiece 383 that receives the light, so that an enlarged image of the cornea HC can be observed through the eyepiece 383.
[0048]
(Embodiment of exposure apparatus)
Next, an embodiment of an exposure apparatus according to the present invention will be described. FIG. 13 is a schematic diagram illustrating a configuration of an exposure apparatus 400 according to the present embodiment. The exposure apparatus 400 is configured using the above-described pulse light source 200, and is used in a photolithography process which is one of the semiconductor manufacturing processes. The exposure apparatus used in the photolithography process is in principle the same as photolithography, in which a device pattern precisely drawn on a photomask (reticle) is converted to a semiconductor wafer or glass substrate coated with photoresist. The image is transferred by optical projection. The exposure apparatus 400 includes the above-described pulse light source 200, wavelength conversion apparatus 401, illumination optical system 402, mask support 403 supporting photomask (reticle) 410, projection optical system 404, and semiconductor wafer 415. The apparatus is provided with a mounting table 405 for mounting and holding, and a driving device 406 for horizontally moving the mounting table 405.
[0049]
In the exposure apparatus 400, the laser light output from the output end of the pulse light source 200 as described above is input to the wavelength conversion device 401, where the laser light having the wavelength required for exposing the semiconductor wafer 415 is converted into a wavelength. Is converted. The laser light whose wavelength has been converted in this way is input to an illumination optical system 402 including a plurality of lenses, and passes therethrough to irradiate the entire surface of a photomask 410 supported by a mask support 403. The light that has been irradiated and passed through the photomask 410 has an image of the device pattern drawn on the photomask 410, and this light is mounted on the mounting table 405 via the projection optical system 404. A predetermined position of the semiconductor wafer 415 is irradiated. At this time, the image of the device pattern on the photomask 410 is reduced on the semiconductor wafer 415 by the projection optical system 404, and the image is exposed.
[0050]
(Other embodiments)
The present invention is not limited to the above embodiment, and various modifications are possible. For example, an optical fiber preform for manufacturing an optical amplification fiber by drawing is not limited to the MCVD method, and may be manufactured by another manufacturing method (VAD method, OVD method, PCVD method, sol-gel method, etc.). Good.
[0051]
Although the above embodiment has been described with reference to an optical fiber doped with erbium Er, it may be applied to an optical fiber doped with another rare earth element such as Yb or Nd. Further, the relative refractive index difference of the core region may not be uniform, and in such a case, the numerical values shown in the above embodiment may be considered to be effective values. Further, the rare earth element may not be added to the entire core region.
[0052]
Further, the light source device of the present invention is not limited to a pulse light source, and may be applied to a CW light source that outputs continuous light.
[0053]
【The invention's effect】
As described above in detail, the optical amplification fiber according to the present invention has a core region to which a rare earth element is added, and a cladding region surrounding the core region and having a lower refractive index than the core region. The diameter is 10 μm or more and 30 μm or less, the outer diameter of the cladding region is 75 μm or more and less than 200 μm, and the relative refractive index difference between the cladding region and the core region is 0.5% or more and 2.0% or less. This optical amplifying fiber is capable of both increasing the output light power, suppressing the occurrence of nonlinear optical phenomena, and compact storage.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of an optical amplification device 1 according to the present embodiment.
FIG. 2 is an explanatory diagram of an optical amplification fiber 10 according to the present embodiment.
FIG. 3 is a configuration diagram of an evaluation system for evaluating the optical amplifying device 1 and the optical amplifying fiber 10 according to the present embodiment.
FIG. 4 is a table summarizing the data of an example and a comparative example of the optical amplification fiber 10 according to the present embodiment.
FIG. 5 is a graph showing the relationship between the pump power and the output peak power in each of the optical amplification fibers of the example and the comparative example.
FIG. 6 is a graph showing the relationship between the core diameter 2a and the nonlinear noise light generation efficiency η for each value of the relative refractive index difference Δ.
FIG. 7 is a graph showing the relationship between the relative refractive index difference Δ and the nonlinear noise light generation efficiency η for each value of the core diameter 2a.
FIG. 8 is a graph showing the relationship between the core diameter 2a and the number of propagable modes for each value of the relative refractive index difference Δ.
FIG. 9 is a configuration diagram of a light source device 200 according to the present embodiment.
FIG. 10 is a schematic diagram illustrating a configuration of a phototherapy device 300 according to the present embodiment.
FIG. 11 is a schematic diagram illustrating a configuration of a wavelength conversion device 360 included in the phototherapy device 300.
FIG. 12 is a schematic diagram showing a configuration of an irradiation optical device 370 and an observation optical device 380 which constitute the phototherapy device 300.
FIG. 13 is a schematic diagram illustrating a configuration of an exposure apparatus 400 according to the present embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Optical amplification apparatus, 10 ... Optical amplification fiber, 20, 30 ... Connection fiber, 40 ... Optical coupler, 50 ... Excitation light source, 200 ... Pulse light source, 300 ... Phototherapy device, 360 ... Wavelength conversion device, 370 ... Irradiation optical device, 380 observation optical device, 400 exposure device, 401 wavelength conversion device, 402 illumination optical system, 403 mask support base, 404 projection optical system, 410 photomask (reticle), 415 semiconductor Wafer.

Claims (15)

A core region to which the rare earth element is added, and a cladding region surrounding the core region and having a lower refractive index than the core region;
An outer diameter of the core region is 10 μm or more and 30 μm or less,
The outer diameter of the cladding region is 75 μm or more and less than 200 μm,
A relative refractive index difference between the core region and the cladding region is 0.5% or more and 2.0% or less;
A fiber for optical amplification characterized by the above. 2. The optical amplification fiber according to claim 1, wherein an outer diameter of the core region is 15 μm or more and 27 μm or less. The optical fiber according to claim 1, wherein an outer diameter of the cladding region is 110 m or more and less than 150 m. The optical amplification fiber according to claim 1, wherein a relative refractive index difference between the core region and the cladding region is 0.7% or more and 1.5% or less. 2. The optical amplification fiber according to claim 1, wherein the rare earth element added to the core region is an Er element. When the addition concentration of the Er element in the core region is 800 wt. The optical amplification fiber according to claim 5, wherein the amount is not less than ppm. 6. The optical amplification fiber according to claim 5, wherein an absorption loss peak near a wavelength of 1530 nm is not less than 20 dB / m and not more than 80 dB / m. 2. An optical amplification device comprising: the optical amplification fiber according to claim 1 for optically amplifying light; and an excitation light supply unit configured to supply excitation light to the optical amplification fiber. A connection fiber is provided between the incident fiber provided on the light incident side of the optical amplification fiber and the optical amplification fiber,
The mode field diameter of the connection fiber is larger than the mode field diameter of the incident fiber, and smaller than the mode field diameter of the optical amplification fiber.
The optical amplifying device according to claim 8, wherein: A connection fiber is provided between the emission fiber provided on the light emission side of the optical amplification fiber and the optical amplification fiber,
The mode field diameter of the connection fiber is larger than the mode field diameter of the output fiber, and smaller than the mode field diameter of the optical amplification fiber.
The optical amplifying device according to claim 8, wherein: The optical amplification device according to claim 8, wherein the optical amplification fiber is wound in a coil shape, and the minimum bending radius of the optical amplification fiber is 15 mm or more. A light source device including a signal generator that generates an electric signal, a semiconductor laser that generates a laser beam based on the electric signal, and an optical fiber amplifier that amplifies a laser beam from the semiconductor laser,
The optical fiber amplifier comprises the optical amplification fiber according to any one of claims 1 to 7,
A light source device characterized by the above-mentioned. 13. The light source device according to claim 12, wherein the electric signal has a pulse shape, the semiconductor laser generates pulsed light, and another optical fiber amplifier is provided in a stage preceding the optical fiber amplifier. A light source device according to claim 12 or 13,
A wavelength converter that converts irradiation light emitted from the outlet of the light source device into irradiation light for treatment having a predetermined wavelength,
An irradiation optical system that guides the irradiation light converted by the wavelength converter to the treatment site and irradiates the irradiation light,
A phototherapy device comprising: A light source device according to claim 12 or 13,
A wavelength converter that converts irradiation light emitted from an outlet of the light source device to irradiation light of a predetermined wavelength,
A mask support for holding a photomask provided with a predetermined exposure pattern,
An object holding unit that holds an exposure object,
An illumination optical system for irradiating the irradiation light converted by the wavelength converter to the photomask held by the mask support,
A projection optical system that irradiates the exposure object held by the object holding unit with irradiation light that has been irradiated to the photomask and passed therethrough via the illumination optical system,
An exposure apparatus comprising:

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