JP2013045537A - Light source device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light source device with high luminous efficiency, capable of increasing a light volume which can be obtained by plasma, even if a laser beam is inexpensive with a small output.SOLUTION: In the light source device provided with an arc tube with a luminescent material sealed inside, a preliminary plasma generating means for generating plasma inside the arc tube, and a continuous wave laser beam oscillation part irradiating continuous wave laser beams inside the arc tube, using light emitted from the plasma, with the continuous wave laser beams irradiated onto plasma generated in the arc tube, the laser beam includes an induction absorption wavelength inherent in the luminescent material.

Description

  The present invention relates to a light source device that is turned on by a laser beam emitted from a laser device and that is suitable for application to an exposure apparatus or the like.

There is known a light source device in which a laser beam from a laser device is irradiated onto an arc tube enclosing a luminescent gas to excite the gas to emit light (Patent Document 1).
FIG. 14 shows a light source device disclosed in Patent Document 1.
The light source device 8 is disposed so as to face the arc tube as an arc tube 82 in which a light emitting element is enclosed, a continuous wave laser oscillation unit 83 that emits a continuous wave laser beam toward the arc tube 82, and a preliminary plasma generating means. A light source device including a pair of electrodes 81, 81.
In the light source device 8, a voltage is applied between the electrodes 81 and 81 to form an arc discharge to create a high-temperature plasma state in the arc tube.
By irradiating the plasma with a laser beam, the plasma temperature can be raised and the emission intensity can be enhanced.
Further, by applying a voltage between the electrodes, the high temperature plasma state in the arc tube 82 can be maintained, and the discharge state can be stabilized without breaking the high temperature plasma state.

JP 2010-205577 A

However, this type of light source device has a problem that a large amount of laser energy is required to increase the radiation light obtained from the plasma, and such a laser source having a large output has a problem that the device becomes large and expensive. .
Therefore, an object of the present invention is to provide a light source device with high light emission efficiency that can increase the amount of light obtained from plasma even if it is inexpensive and has a small output.

  In order to solve the above-mentioned problems, an invention according to claim 1 is directed to an arc tube in which a luminescent material is sealed, preliminary plasma generating means for generating plasma in the arc tube, and continuous wave laser light irradiation in the arc tube. In a light source device that includes a continuous wave laser oscillating unit that irradiates plasma generated in an arc tube with continuous wave laser light and uses light emitted from the plasma, the laser light has an induced absorption wavelength specific to the luminescent material. It is characterized by including.

The invention according to claim 2 is the invention according to claim 1, wherein the laser beam has a wavelength in a range having an emission intensity of 1 / e ² or more of an emission intensity of an oscillation wavelength. It includes a characteristic induced absorption wavelength.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, the laser irradiation means includes a laser diode, and includes a laser diode temperature adjustment mechanism.

  The invention according to claim 4 is the invention according to any one of claims 1 to 3, wherein the light-emitting substance is a rare gas.

  The invention described in claim 5 is characterized in that, in the invention described in claim 4, the rare gas includes any one of Xe (xenon), Ar (argon), and Kr (krypton).

  The invention according to claim 6 is the invention according to any one of claims 1 to 3, wherein the luminescent material is composed of a first luminescent material and a second luminescent material. And

  According to a seventh aspect of the invention, in the sixth aspect of the invention, the first luminescent material is a rare gas and the second luminescent material is a metal.

  The invention according to claim 8 is the invention according to claim 7, wherein the metal is Hg (mercury).

  According to a ninth aspect of the present invention, there is provided the light source device according to the fifth aspect, wherein the light emitting material is a projector made of Xe (xenon).

  According to a tenth aspect of the present invention, there is provided an exposure apparatus comprising the light source device according to the eighth aspect.

  The invention described in claim 11 is a projector including the light source device described in claim 8.

  According to a twelfth aspect of the present invention, in the first to eighth aspects of the present invention, the preliminary plasma generating means includes two or more electrodes disposed in the arc tube and a power source for applying a voltage between the electrodes. It is characterized by that.

  According to a thirteenth aspect of the present invention, in the first to eighth aspects of the present invention, the preliminary plasma generating means is a pulse laser oscillation unit that irradiates a pulse laser in the arc tube.

According to the first aspect of the present invention, the plasma formed in the arc tube is irradiated with laser light having an oscillation wavelength including the intrinsic induced absorption wavelength of the luminescent material forming the plasma, and light emission from the plasma is increased. Therefore, light emission can be increased without changing the output of the laser beam.
Furthermore, plasma emission with a wavelength different from the oscillation wavelength of the laser light can be increased, so that the light emission efficiency can be increased.

According to the second aspect of the present invention, when the laser light has a wavelength in a range having an emission intensity of 1 / e ² or more of the emission intensity of the oscillation wavelength, stronger induced absorption occurs and more light emission occurs. To increase.

  According to a third aspect of the present invention, the laser diode is provided, and the temperature adjustment mechanism of the laser diode is provided, so that the mismatch between the oscillation wavelength and the induced absorption wavelength is eliminated to some extent, and a laser beam having a suitable wavelength is emitted. The tube can be irradiated.

  According to the invention described in claim 4, since the luminescent substance is a rare gas, it is chemically inert, does not react with the arc tube material and does not color, and has various wavelengths depending on the encapsulated material. Light can be emitted.

  According to the invention described in claim 5, since the luminescent material contains any of xenon, argon, and krypton, the effect of increasing the plasma emission becomes good, and the lasing wavelength corresponding to these luminescent materials. Is easy to select.

  According to the invention described in claim 6, a plurality of light emission can be used by configuring the light emitting material from the first light emitting material and the second light emitting material different from the first light emitting material. Irradiation with a laser beam including an induced absorption wavelength specific to one of the light emitting materials can increase light emission of the other light emitting material.

  Further, according to the invention described in claim 7, by using a rare gas as the first luminescent material and a metal as the second luminescent material, the same use as that of an existing lamp capable of obtaining characteristic radiation by the metal enclosure Can be used.

  According to the eighth aspect of the present invention, ultraviolet or visible light can be used by using mercury as the metal.

  According to the invention of claim 9 or 11, a projector having excellent luminous efficiency can be realized using the light source device of the present invention.

  According to the invention described in claim 10, it is possible to realize an exposure apparatus having excellent luminous efficiency by using the light source device of the present invention.

  According to the twelfth aspect of the present invention, since the preliminary plasma generating means can be a power source for applying a voltage between two or more electrodes arranged in the arc tube and between the electrodes, a lamp-type arc tube can be used. Can be used.

According to the thirteenth aspect of the present invention, since the preliminary plasma generating means can be a pulse laser oscillation unit that irradiates a pulse laser in the arc tube, the light source device can be configured only by the laser oscillation device. Since there is no need to install an electrode in the arc tube, the electrode material does not evaporate and adhere to the tube wall of the arc tube due to the high temperature of the plasma.

1 is an overall configuration diagram of a light source device according to the present invention. The whole block diagram of the light source device using the pulse laser oscillation part is shown as another example of the preliminary | backup plasma generation means based on this invention. It is a figure which shows the result about the experiment 1 which concerns on this invention. The table | surface about the induced absorption wavelength intrinsic | native to a luminescent substance suitable as an oscillation wavelength of the laser irradiated to the arc tube of the light source device which concerns on this invention is shown. It is a figure which shows the measurement result of the experiment 2 about the absorption factor of a laser beam. The schematic diagram showing the relationship between the oscillation wavelength of the laser beam based on this invention and an induced absorption wavelength is shown. It is a figure which shows the result about the experiment 3 which concerns on this invention. It is a figure which shows the result about the experiment 4 which concerns on this invention. It is a figure which shows the result about the experiment 5 which concerns on this invention. It is a figure which shows the result about the experiment 6 which concerns on this invention. It is a figure which shows the result about the experiment 7 which concerns on this invention. It is a figure which shows the result about the experiment 8 which concerns on this invention. It is a whole block diagram of the exposure apparatus using the light source device which concerns on this invention. It is a whole block diagram of the light source device which concerns on a prior art example.

This will be described below with reference to the drawings.
FIG. 1 is an overall configuration diagram of a light source device according to the present invention.
The light source device 1 supplies power to the arc tube 2 into which laser light is incident, the preliminary plasma generating means 10 that generates plasma in the arc tube 2, the continuous wave laser oscillation unit 3 that oscillates continuous wave laser light, and the laser oscillation unit. A power supply device 5 and a control unit 4 that controls the power supply device 5 are provided.

The arc tube 2 is a sealed container made of a translucent material in which a luminescent substance is enclosed.
Laser light from the continuous wave laser oscillation unit 3 is incident on the arc tube 2 and (exit light) excitation light from the luminescent material enclosed inside is emitted to the outside of the arc tube 2. Therefore, even when incident light has a wavelength of 980 nm and output light has a wavelength different from each other, such as a wavelength of 365 nm, it is made of a member that can transmit both well, for example, quartz glass.

Various light-emitting substances are appropriately selected and sealed in the arc tube 2 in accordance with light having a wavelength desired to be used depending on the application. This will be described later.

The optical member 7 is disposed on the optical path of the laser light between the continuous wave laser oscillation unit 3 and the arc tube 2 for condensing the laser light.
The optical member 7 has a condensing function such as a condensing lens or a diffractive optical grating, and is configured to focus on the inside of the arc tube. Although FIG. 1 illustrates a beam that transmits light, a light collecting mirror or a diffraction grating may be used as long as it has a light collecting function.

Preliminary plasma generating means 10 includes those that apply a voltage to the discharge inner electrode disposed in the arc tube to form arc discharge, and those that irradiate the pulse laser by the pulse laser oscillation unit. In the present invention, Either can be used as the preliminary plasma generating means 10.
The preliminary plasma generation means 10 shown in FIG. 1 can continuously generate plasma in the arc tube by applying a voltage between the discharge electrodes 11 arranged in the arc tube 2 and causing arc discharge. .

FIG. 2 shows an overall configuration of a light source device 1 in which the preliminary plasma generation means 10 is configured by using a pulse laser oscillation unit 12, an optical member 13, and a control unit 14 as another example of the present invention.
Note that this figure is the same as FIG. 1 except that the pulse laser oscillation unit 12 and the like are used as the preliminary plasma generating means 10, and the description of the other components is omitted.
As shown in this figure, plasma that is intermittently generated in the arc tube can be generated by condensing and irradiating the pulse laser from outside the arc tube 2 to the inside of the arc tube 2. Then, plasma is continuously formed by irradiating the arc tube with a continuous wave laser in advance or by irradiating the continuous wave laser in accordance with the timing of irradiation with the pulse laser.

Returning to FIG. 1 again, the continuous wave laser oscillation unit will be described.
The continuous wave laser oscillation unit 3 is a device using, for example, a laser diode (LD) as a laser source, and continuously oscillates laser light.
The continuous wave laser oscillating unit 3 includes a power supply device 5 that supplies power to the continuous wave laser oscillating unit 3, a temperature adjusting mechanism 6 that adjusts the temperature of the laser diode, and a control unit 4 that controls these.
The controller 4 can control these by changing the temperature and current value of the laser diode.
The temperature adjustment mechanism 6 of the laser diode is based on a heating / cooling element such as a Peltier element disposed on a water-cooled cooling plate. The controller 4 adjusts the temperature of the laser diode by adjusting the current flowing from the power supply device 5 to the temperature adjusting mechanism 6.
Since the laser diode has a temperature characteristic that the oscillation wavelength shifts depending on the temperature, the oscillation wavelength can be adjusted by adjusting the temperature of the laser diode.
Generally, a laser diode has a wavelength-temperature characteristic of 0.30 to 0.25 nm / ° C. Therefore, in order to shift the oscillation wavelength by 1 nm, the temperature of the laser diode may be changed by about 4 ° C.
Thereby, a laser light source having a desired oscillation wavelength can be obtained within a certain range by using an existing laser diode that can be easily obtained.
Even if the temperature is not adjusted, the wavelength of the original laser beam can be converted into a desired wavelength by using a wavelength stabilizing element such as a volume Bragg grating (VBG) or a volume holographic grating (VHG). it can.

The following experiment was conducted using the light source device shown in FIG.
<Experiment 1>
In the experiment, a preliminary plasma is generated in an arc tube in which a luminescent material is sealed, and the emission intensity distribution is measured by irradiating the plasma with laser light from a laser oscillation unit.
Xe and Ar were sealed in the arc tube at a ratio of 1: 9. A continuous wave laser having an oscillation wavelength of 810 nm and an output of 50 W was used.
Next, a voltage was applied between the electrodes in the arc tube to form plasma by arc discharge. The applied voltage was 50 W (hereinafter, all voltages applied between the electrodes were 50 W).
Then, the temperature of the laser diode was adjusted by a temperature adjustment mechanism, and the laser oscillation wavelength was set to 806.1 nm. Laser light with adjusted wavelength was incident on the plasma, and the emission intensity distribution of the gas in the emission space was measured.

FIG. 3A is a diagram showing the emission intensity distribution of the gas in the arc tube at an oscillation wavelength of 806.1 nm. The light emission intensity indicates the magnitude of the numerical value by shading. The darker the intensity, the higher the light emission intensity.
In this figure, a pair of electrodes, each having a tip directed toward the center, are arranged opposite to each other on the left end side and the right end side of the sheet. An arc discharge is formed between these electrodes, and light emission by the plasma is observed in the central portion.
The laser light having an oscillation wavelength of 806.1 nm is incident from the near side to the back at the slightly lower right position of the left end electrode, but it can be seen that no light is emitted.
Therefore, what is observed is light emission of plasma formed only by arc discharge, and light emission due to laser irradiation was not observed.

Next, only temperature adjustment was performed while keeping the laser beam output (50 W) constant, the oscillation wavelength was changed to 810.8 nm, and the emission intensity distribution of the gas in the emission space was measured.
FIG. 3B is a diagram showing the emission intensity distribution of the gas in the arc tube at a wavelength of 810.0 nm (match).
In the same manner as described above, the laser was irradiated slightly from the left end electrode to the lower right position. Then, light emission different from the plasma by the arc discharge formed between the electrodes was observed. These two examples are the same laser output and laser irradiation position, but due to the change of the oscillation wavelength, light emission did not occur in FIG. 3 (a), whereas light emission occurred in FIG. 3 (b). Different results were obtained.
Although not shown in FIG. 3B, the laser light is transmitted through the arc tube. In the laser beam receiver that has passed through the arc tube, the output of the received laser beam has decreased.

Details of these phenomena are not clear, but are thought to be due to the following reasons.
First, since the output of the laser beam penetrating the arc tube is decreasing, it is considered that the energy of the laser beam contributes to an increase in plasma emission.
3 (a) and 3 (b) differ only in the oscillation wavelength of the laser beam, and no light emission is observed in (a), and light emission is observed only in (b). This increase is considered to be caused by a change in the oscillation wavelength of the laser beam.
Here, FIG. 4 shows a table of induced absorption wavelengths specific to each luminescent material as a key for explaining these phenomena. In this table, referring to the induced absorption wavelength of Ar, it can be seen that there is an induced absorption wavelength at 810.3693 nm.
In the experimental result shown in FIG. 3A, the oscillation wavelength of the laser beam is 806.1 nm, which does not coincide with 810.3693 nm. On the other hand, in FIG. 3B, the oscillation wavelength of the laser light is 810.0 nm, which is almost the same.
From this, it is presumed that in FIG. 3B, induced absorption of the laser light has occurred. Here, induced absorption is also simply referred to as absorption or absorption, and refers to a phenomenon in which a substance absorbs light.
That is, since there are a number of intrinsic induced absorption wavelengths in the atoms of the luminescent material sealed in the arc tube 2, as shown in FIG. 4, when any of these wavelengths matches the wavelength of the laser beam, It is thought that induced absorption occurred. And it is thought that the plasma temperature rose and the radiation from the plasma increased due to the induction absorption.
From the above experimental results, it was possible to increase the emitted light obtained from the plasma by adjusting only the oscillation wavelength of the laser so that induction absorption occurs without increasing the output of the laser as in the prior art. Further, it was found that the light emission efficiency can be improved because the light emission increases even with a low-power laser.

The table according to FIG. 4 is a table in which wavelengths having relatively large relative intensities are selected from the intrinsic induced absorption wavelengths of the luminescent materials based on the NIST database (NIST Bibliographic Datebases).
Regarding Xe, in addition to Xe (1) based on the NIST database, Xe (2) also shows literature values by Table of spectral lines (Zadel ', AN IFI-Plenum, 1970). This is because the induced absorption wavelength may vary in measured value depending on the measurement method and conditions, and the reported value varies depending on the literature.

<Experiment 2>
Next, an experiment was conducted to verify that induced absorption occurred by irradiating laser light.
Irradiation was performed while changing the wavelength based on the laser light that oscillates the above-described stimulated absorption wavelength, and the absorption rate of the induced absorption generated in the luminescent material was measured.
Xe was used as the luminescent material, and the oscillation wavelength of the laser was centered at 980 nm and 880 nm, both of which are induced absorption wavelengths of Xe, and was changed by temperature change.
The absorptance is measured with a laser power monitor using the apparatus shown in FIG. 1, with a laser power receiver installed on the opposite side of the laser oscillation part across the arc tube, that is, at a position for receiving the laser beam penetrating the arc tube. It calculated using the result.
FIG. 5 is a diagram showing the calculated absorption rate. The horizontal axis represents the wavelength (nm) of the laser beam, and the vertical axis represents the absorption rate (%). The absorptance was calculated as the amount of absorption / output by calculating the loss from the difference between the output of the oscillated laser beam and the energy of the received laser beam, and assuming that the loss contributed to the induced absorption.

In this figure, (1) is the Xe absorption rate when laser light with a wavelength of 980 nm is irradiated. The absorption at the induced absorption wavelength of 980 nm was the highest, and a distribution spreading in a mountain shape with this wavelength at the top was confirmed.
That is, the laser oscillation wavelength had the highest absorption rate when matched with the induced absorption wavelength, and the absorption rate decreased by shifting from there. This is considered to be due to the fact that the laser light actually has a fixed wavelength width instead of a single wavelength.
(2) is the absorption rate of Xe when irradiated with laser light having a wavelength of 880 nm. As in (1), the absorption wavelength is 881 nm, which is the induced absorption wavelength, and the absorption rate is the highest. That is, this tendency is the same even when the induced absorption wavelength is different.
From these facts, it is understood that it is preferable to match the oscillation wavelength with the induced absorption wavelength in order to efficiently absorb the laser beam. Further, since the phenomenon of induced absorption itself occurs even if the induced absorption wavelength is slightly deviated, it can be seen that there is an allowable range for the oscillation wavelength of the laser light within a certain wavelength range.

The preferred range of the induced absorption wavelength that has been studied from the above will be described below.
FIG. 6 is a schematic diagram showing the relationship between the oscillation wavelength of the laser beam and the induced absorption wavelength.
This figure shows the wavelength distribution of the laser beam with the wavelength (nm) on the horizontal axis and the emission intensity (arbitrary intensity) on the vertical axis, and the relationship between the distributed laser beam and the induced absorption wavelength specific to a certain substance Show.
From the results of the above <Experiment 1> and <Experiment 2>, if the laser light having a certain wavelength range includes an induced absorption wavelength, stimulated absorption occurs. That is, the induced absorption wavelength unique to the luminescent material may be included in the range of the laser light distribution.
This is because part of the distributed laser light includes the induced absorption wavelength, so that induced absorption occurs, and the energy of the laser light raises the plasma temperature and the light emission from the plasma increases.

This will be described with reference to wavelength ranges 1 and 2 of the laser beam and induced absorption wavelengths 1, 2, and 3 shown in the figure.
If the wavelength range 1 and the induced absorption wavelengths 1 and 2 shown in the figure cross each other, it can be said that there are components that cause absorption in the laser light, and the induced absorption wavelength is included. That is, the laser beam having the wavelength range 1 with respect to the induced absorption wavelengths 1 and 2 can be suitably used as the laser beam of the present invention.
Conversely, when there is a relationship such as the wavelength range 1 and the stimulated absorption wavelength 3, no induced absorption occurs, so that the laser beam having the wavelength range 1 is not suitable as the laser beam of the present invention.

Furthermore, in this figure, as a more preferable wavelength range, a wavelength range 2 having a light emission intensity that is 1 / e ² or more of the peak light emission intensity around the peak wavelength is shown.
This numerical value of 1 / e ² is a numerical value having a technical significance as a reference for a sufficient laser output so that, for example, the cross-sectional intensity distribution of the laser light has a beam diameter within a range where the output exceeds this intensity. is there.
Here, since the wavelength range 2 includes the induced absorption wavelength 1, it can be said that the present invention has a more preferable relationship than the wavelength range 1. This is because if the wavelength range 2 includes an induced absorption wavelength, stimulated absorption stronger than that in the wavelength range 1 occurs, and light emission is further enhanced.

The relationship between the laser light and the stimulated absorption wavelength as in the above wavelength ranges 1 and 2 is, for example, by actually measuring the distribution of the laser light and comparing it with the specific induced absorption wavelength for each specific luminescent material. It can be confirmed by comparing the oscillation wavelength and wavelength width, which are clarified as the specifications of the laser, with a specific induced absorption wavelength.
For example, the wavelength shown in FIG. 4 is used as the induced absorption wavelength unique to the luminescent material. In principle, an induced absorption wavelength may be used, but a wavelength with a small relative intensity causes a weak absorption and is not very practical. In this table, induced absorption wavelengths having relatively strong intensities are selected and listed, and these are suitable because they are wavelengths at which strong induced absorption occurs.
Note that the luminescent materials are examples, and application of the present invention is not limited to these luminescent materials.

A typical example of the luminescent material used for the present invention described above will be described. The light-emitting substance is not particularly limited, but a rare gas such as xenon (Xe), argon (Ar) krypton (Kr), or neon (Ne) is enclosed.
By using the rare gas, it is possible to provide a light source device that is chemically inert and does not react with the arc tube material to be colored, and emits light of various wavelengths by the encapsulated material.
In particular, xenon is enclosed mainly for the purpose of using visible light, and is used for a light source such as a projector.

In order to confirm in which wavelength range the effect of the present invention occurred when a rare gas was sealed as a luminescent substance, an emission spectrum was first measured for Xe.
<Experiment 3>
In the experiment, the apparatus shown in FIG. 1 was used, and Xe alone was sealed in the arc tube 2 at 10 atm. After forming plasma by discharge, a laser having an oscillation wavelength of 881.0 nm and an output of 44 W was irradiated.
FIG. 7 shows the emission spectrum measurement results of the radiated light obtained from the plasma in the arc tube. (A) shows the measurement results in the wavelength region of 800 to 1000 nm, and (b) shows the measurement results in the wavelength region of 350 to 750 nm.
The graph shows (1) the measurement result of only the laser beam, (2) the measurement result of the plasma synchrotron radiation when irradiating the laser with the wavelength of 876.0 nm (wavelength mismatch) in addition to the arc discharge, and (3) the addition of the arc discharge. The results of measuring the plasma synchrotron radiation when irradiating a laser with a wavelength of 881.0 nm (wavelength coincidence) are shown.

In FIG. 7A, emission peaks (1), (2), and (3) are observed at a wavelength of 881.0 nm, respectively. As described above, this point is an induced absorption wavelength, and the oscillation wavelength of the laser in (3) is adjusted according to this wavelength.
Comparing the emission peak intensities of (2) and (3) respectively, even when the emission peak of a wavelength other than 881.0 nm which is the oscillation wavelength of the laser is irradiated with a laser having the same wavelength of (3), It can be seen that the emission intensity is higher than that in the case of irradiating a laser whose wavelength does not match in (2).

Further, in FIG. 7B, a continuous spectrum is observed in the visible light range of 350 nm to 750 nm, and the emission of (3) is compared with the emission intensity of (2) for all wavelengths within this range. Strength is increasing.
From the above, it was confirmed that when the light emitting material was irradiated with laser light having an induced absorption wavelength and the laser light was absorbed, the emitted light increased not only at the laser oscillation wavelength but also at other wavelengths.

<Experiment 4>
Next, an emission spectrum was measured for Kr in order to confirm whether the same phenomenon occurs even with a light emitting material different from Xe.
In the arc tube, only Kr was sealed at 10 atm. After plasma was formed by discharge, a laser having an oscillation wavelength of 810.0 nm and an output of 50 W was irradiated. This is because Kr has some strong induced absorption around 810 nm (see FIG. 4).

FIG. 8 shows an emission spectrum measurement result of the radiated light obtained from the plasma in the arc tube. Note that the measurement result of only the laser is not shown.
The graph shows (4) plasma synchrotron radiation measurement results when irradiating a laser with a wavelength of 806.1 nm (wavelength mismatch) in addition to arc discharge, and (5) a laser with a wavelength of 810.0 nm (wavelength match) in addition to the arc discharge. ) Shows the measurement result of the plasma synchrotron radiation.
In FIG. 8, when the emission peak intensity at the wavelength of 810 nm where the emission intensity is the highest is compared, the emission intensity in the case of the wavelength coincidence in (5) is remarkably larger than the emission intensity in the case of the wavelength mismatch of (4). Recognize.
It can be said that the intensity of (5) is larger than that of (4) in the same manner as described above for other emission peaks.
From the above, it was confirmed that when Kr is irradiated with a laser having an induced absorption wavelength and the light emitting material absorbs the laser light, the emitted light increases not only at the laser oscillation wavelength but also at other wavelengths. .

<Experiment 5>
In order to investigate the case where two or more kinds of luminescent substances are encapsulated, measurement was also performed on an arc tube in which Xe and Ar were mixed and encapsulated.
First, in the case where Xe was sealed in the arc tube at 9 atm and Ar at 1 atm, that is, 9: 1, the emission spectrum was measured in the same manner as the above experiment.
As the laser light, an oscillation wavelength of 881.0 nm with an induced absorption of Xe and an output of 44 W were used.

FIG. 9 shows an emission spectrum measurement result of the radiated light obtained from the plasma in the arc tube.
The graph shows (6) plasma synchrotron radiation measurement results when irradiating a laser with a wavelength of 876.0 nm (wavelength mismatch) in addition to arc discharge, and (7) a laser with a wavelength of 881.0 nm in addition to arc discharge (wavelength match) ) Shows the measurement result of the plasma synchrotron radiation.

In FIG. 9, when the emission peak at the wavelength of 881.0 nm where the emission intensity is the highest is compared, the emission intensity in the case of wavelength matching in (7) is higher than the emission intensity in the case of wavelength mismatching in (6). Recognize.
Since the ratio of the filled gas is almost occupied by Xe, there is almost no difference from the result of Xe alone in <Experiment 2>.

<Experiment 5>
Next, in the case where Xe was sealed at 1 atmosphere and Ar was sealed at 9 atmospheres, that is, 1: 9, the emission spectrum was measured in the same manner as in the above experiment.
As the laser, an oscillation wavelength of 810.0 nm and an output of 50 W having weak induced absorption of Xe and strong induced absorption of Ar were used. The reason for changing the laser wavelength in the above <Experiment 4> is to make it easier to confirm the emission of Ar by selecting a wavelength with strong Ar absorption and making the increase in emission remarkable.

FIG. 10 shows the emission spectrum measurement result of the radiated light obtained from the plasma in the arc tube. Note that the measurement result of only the laser is not shown.
The graph shows (8) plasma synchrotron radiation measurement results when irradiating a laser with a wavelength of 806.0 nm (wavelength mismatch) in addition to arc discharge, and (9) a laser with a wavelength of 810.0 nm (wavelength matching) in addition to the arc discharge. ) Shows the measurement result of the plasma synchrotron radiation.

In FIG. 10, when the emission peak at the wavelength of 810 nm having the highest emission intensity is compared, it can be seen that the emission intensity in the case of the wavelength match in (9) is significantly higher than the emission intensity in the case of wavelength mismatch in (8). .
Moreover, when FIG. 10 and FIG. 9 are compared, the emission peak which was not observed in FIG. 9 was observed in 750 nm-850 nm. This is the light emission caused by Ar, and is considered to be due to the fact that the enclosure ratio of Ar is almost occupied.
In addition, there was Xe induced absorption at 881.0 nm, and a peak group near 881.0 nm by Xe observed in FIG. 9 and an increase in light emission were observed.
From the above, it was found that even when two or more kinds of luminescent substances are encapsulated, there is an effect of increasing the luminescence caused by each substance.

<Experiment 6>
Next, an experiment was conducted in the case where two types of luminescent materials were encapsulated and the laser oscillation wavelength was matched with only the induced absorption wavelength of one of the luminescent materials.
The arc tube 2 was filled with 10 atm of Xe and 10 mg / mm ^{3 of} Hg (mercury).
After plasma was formed by discharge in the arc tube 2, a laser having an oscillation wavelength of 881.0 nm and an output of 44 W was irradiated.

FIGS. 11A and 11B show the emission spectrum measurement results of the radiated light obtained from the plasma in the arc tube. FIG. 11A shows the measurement results in the wavelength range of 800 to 1000 nm, and FIG. 11B shows the measurement results in the wavelength range of 250 to 500 nm.
The graph shows (10) measurement result of only laser light, (11) measurement result of plasma synchrotron radiation when irradiating laser with wavelength 876.0 nm (wavelength mismatch) in addition to arc discharge, (12) addition to arc discharge The results of measuring the plasma synchrotron radiation when irradiating a laser with a wavelength of 881.0 nm (wavelength coincidence) are shown.

In FIG. 11A, the emission peaks of (10), (11), and (12) are observed at the oscillation wavelength of 881.0 nm, respectively. This wavelength is the induced absorption wavelength of Xe, and there is no strong induced absorption wavelength of mercury near this wavelength, and no emission peak is observed.
Comparing the emission peak intensities at 881.0 nm (11) and (12), respectively, it can be seen that, similarly to <Experiment 2>, the irradiation with a laser having the same wavelength of (12) is larger.

In FIG. 11B, it can be seen that in the ultraviolet region with a wavelength of 250 nm to 450 nm, the emission intensity of (12) is larger than the emission intensity of (11), but this is not the emission wavelength of Xe, but Hg Is the emission wavelength. This is presumably because Xe in the plasma absorbs the laser beam, and as a result, the plasma temperature rises and contributes to the enhancement of Hg emission intensity.
In other words, if the encapsulated substance is a substance that induces and absorbs incident laser light, the plasma temperature of the substance increases, thereby increasing the emission of other substances that do not have induced absorption of the incident laser light. Can also contribute.

  From the above, even when two types of luminescent materials are encapsulated and only one type of luminescent material is irradiated with the laser's oscillation wavelength matched to the induced absorption wavelength, stimulated absorption is achieved without increasing the laser output. It was found that the radiated light obtained from the plasma can be increased by adjusting the oscillation wavelength so as to generate.

<Experiment 7>
Finally, the emission spectrum of the arc tube enclosing Ar and Na was also measured.
Since Na has an induced absorption wavelength at 1074 nm, a laser having an oscillation wavelength of 1074 nm was used.
FIG. 12 shows the measurement results of the emission spectrum of the radiated light obtained from the plasma in the arc tube. Note that the measurement result of only the laser is not shown.

In this figure, (13) plasma synchrotron radiation measurement result when irradiated with a laser with a wavelength of 1070 nm (wavelength mismatch), and (14) plasma synchrotron radiation measurement result when irradiated with a laser with a wavelength of 1074 nm (wavelength match) are shown. .
Comparing the light emission peaks having the highest light emission intensity, it can be seen that the intensity in the case of the wavelength coincidence (14) is remarkably higher than that in the case of the wavelength mismatch of (13).
It can be said that the intensity of (14) is larger than that of (13) for the other emission peaks as well.
From the above, it has been confirmed that when Na is irradiated with a laser having an induced absorption wavelength and the light emitting material absorbs the laser light, the emitted light increases not only at the laser oscillation wavelength but also at other wavelengths. It was.

As described above, the luminescent material can be composed of a first luminescent material and a second luminescent material different from the first luminescent material.
By combining a plurality of light-emitting substances, a plurality of light emission can be used, and when one of the light-emitting substances is irradiated with a laser beam including an intrinsic absorption wavelength, the other light-emitting substance emits light. Can also be increased. In addition, you may comprise from 3 or more types of luminescent substances.
In the case where both the first luminescent material and the second luminescent material are rare gases, for example, a mixed gas of xenon and argon (Ar) is enclosed. In this case, the light emitted by xenon is mainly used as visible light.

In addition, a rare gas can be used for the first luminescent material, and a metal can be used for the second luminescent material. In this case, it can be used for the same use as an existing lamp in which characteristic radiation is obtained by the metal enclosure.
Specific examples of combinations include xenon and mercury (Hg), argon and sodium (Na), etc., which have been shown in experiments. Mercury is sealed mainly for the purpose of using ultraviolet light. More specifically, it is used for a light source such as an exposure apparatus used for photolithography.

Below, the example of the concrete use of the light source device of this invention is demonstrated.
FIG. 13 is an overall configuration diagram of an exposure apparatus 20 using the light source device according to the present invention.
When the light source device of the present invention contains a light source, particularly mercury, it can be used for the exposure device 20 as an ultraviolet light source utilizing this light emission. The ultraviolet rays used are, for example, ultraviolet rays in the region of 250 to 450 nm shown in FIG.
Even if the laser light does not include the induced absorption wavelength of mercury, it is only necessary that a gas having induced absorption of laser light, such as Xe or Ar, is enclosed in the arc tube 22 together with mercury.
In this exposure apparatus 20, a condensing mirror 28 is disposed so as to cover the light source device, and this condensing mirror 28 has a reflecting surface in which a rotation ellipse is halved with a short diameter.
The condensing mirror 28 has an opening facing downward in the drawing, and the periphery of the arc tube 22 is covered by the condensing mirror 28 having such an opening.
The condensing mirror 28 has one through-hole into which the beam from the continuous wave laser oscillation unit 23 is incident and the other through-hole through which the beam that has passed through the arc tube 22 is emitted. The arc tube 22 and the condenser mirror 28 are accommodated in a casing 29.
With such a configuration, the light source device of the present invention can be used for an exposure apparatus.

Depending on the luminescent substance, the light source device of the present invention can be used as a visible light source in a projector. The specific configuration of the apparatus will be omitted.
For example, when a 881.0 nm laser is used as the luminescent material, only xenon may be used, or mercury may be enclosed together with xenon.
Further, if there is a laser that can irradiate laser light including an induction absorption wavelength of mercury, only mercury may be used.
As shown in FIG. 7B, a broad continuous wavelength is observed in the visible light range of 350 nm to 750 nm, and this is used for projectors used for home use and office use like an ultrahigh pressure mercury lamp. It can be used as a light source, or it can be used as a light source for a projector used in a movie theater like a xenon lamp.

DESCRIPTION OF SYMBOLS 1 Light source device 2 Light emission tube 3 Continuous wave laser oscillation part 4 Control part 5 Power supply device 6 Temperature adjustment mechanism 7 Optical member 10 Preliminary plasma generation means 11 Discharge electrode 12 Pulse laser oscillation part 13 Optical member 14 Oscillation part 20 Exposure apparatus 22 Light emission tube 23 Continuous wave laser oscillator 26 Beam damper 27 Optical member 28 Condensing mirror 29 Casing 8 Light source device 81 Electrode 82 Light emitting tube 83 Continuous wave laser oscillator 84 Condensing mirror 85 Beam damper 87 Condensing member

Claims (13)

An arc tube with a luminescent material sealed inside,
Preliminary plasma generating means for generating plasma in the arc tube;
Provided with a continuous wave laser oscillating unit for irradiating continuous wave laser light in the arc tube,
In the light source device that uses the light emitted from the plasma when the plasma generated in the arc tube is irradiated with continuous wave laser light,
The light source device, wherein the laser light includes an induced absorption wavelength unique to the luminescent material. ^2. The light source device according to claim 1, wherein the laser light has a wavelength in a range having an emission intensity of 1 / e ² or more of an emission intensity of an oscillation wavelength including an induced absorption wavelength unique to the light emitting material. .   The light source device according to claim 1, wherein the continuous wave laser oscillating unit includes a laser diode and includes a temperature adjustment mechanism of the laser diode.   The light source device according to claim 1, wherein the luminescent material is a rare gas.   The light source device according to claim 4, wherein the rare gas includes any one of Xe (xenon), Ar (argon), and Kr (krypton).   The light source device according to any one of claims 1 to 3, wherein the luminescent material includes a first luminescent material and a second luminescent material.   The light source device according to claim 6, wherein the first luminescent material is a rare gas and the second luminescent material is a metal.   The light source device according to claim 7, wherein the metal is Hg (mercury).   A projector comprising the light source device according to claim 5, wherein the luminescent material is Xe (xenon).   An exposure apparatus comprising the light source device according to claim 8.   A projector comprising the light source device according to claim 8. The preliminary plasma generating means includes two or more electrodes disposed in the arc tube,
9. The light source device according to claim 1, wherein the light source device applies a voltage between the electrodes.   9. The light source device according to claim 1, wherein the preliminary plasma generating means is a pulse laser oscillation unit that irradiates a pulse laser in an arc tube.

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