JP2569700B2 - Optical element for laser - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a coating of an optical element for an excimer laser.

[Conventional technology]

FIG. 2 shows, for example, the magazine “Appl. Phys. Lett.” 44 (1984) 6
FIG. 58 is a configuration diagram showing what optical elements are used for an excimer laser based on the conventional excimer laser shown in 58. In the figure, (1) is a discharge part, (2) is a partial reflection mirror, (3) is a total reflection mirror, (4) is a laser beam,
(5), (6) are windows, (9a), (9b), (9c) are etalons, (10) is a beam splitter, (11) is a lens, (1)
2) is a power meter. FIG. 3 is a partially enlarged sectional view of an optical element such as a mirror, a window, a beam splitter, and a lens. (13) is scattered light, (14) is an O-ring, (51) is an optical element body (50). Here, it is a holder for holding the window.

Next, the operation will be described. When an optical resonator composed of a partial reflection mirror (2) and a total reflection mirror (3) is assembled with the discharge part (1) interposed therebetween, light generated in the discharge part (1) is amplified while going back and forth through the optical resonator. Then, a laser beam (4) is obtained. However, in the case of an excimer laser, since the wavelength width is wide, the band can be narrowed by inserting a spectral element into the optical resonator. For example, in FIG. 2, three types of etalons (9a),
(9b) and (9c) are inserted.

Although not shown, the air-gap type etalon (9b) changes the selected wavelength due to atmospheric pressure fluctuation. So, for example, the magazine “Appl. Opt.” 13 (1974) 1
As shown at 625, the airgear etalon may be placed in an airtight chamber (FIG. 4). In this case, windows (7) and (8) for passing the laser beam are required in the hermetic chamber.

If the power is monitored using a part of the laser beam, as shown in FIG. 2, the beam splitter (10), the lens (11), and the power monitor (1) are used.
2) would be necessary.

Thus, an excimer laser uses a very large number of optical elements.

By the way, how are these optical elements held? In many cases, “Laser Research” 11 (1983) 69
As shown in 4, the optical element body is held by pressing it against an elastic body such as an O-ring (FIG. 3).

[Problems to be solved by the invention]

The conventional excimer laser is constituted by many optical components as described above. However, when such a large number of elements are present, the laser beam is scattered, and the scattered light (13) flies in an unexpected direction. When this light hits an elastic body such as an O-ring, the elastic body deteriorates and impurities are generated.
For example, a commonly used elastic material is, for example, However, when scattered light of an excimer laser, that is, ultraviolet rays, is applied to CH ₂ , the bond is broken and carbon is generated. This carbon caused the optical element to become dirty.

The present invention has been made in order to solve the above-mentioned problems, and prevents laser light such as scattered light from reaching an elastic body such as an O-ring to reduce dirt on an optical element and reduce laser output. Aim to get no excimer laser.

[Means for solving the problem]

The optical element for laser according to the present invention is such that a coating film that blocks laser light incident on the elastic body is provided on a contact portion of the surface of the optical element body with the elastic body.

[Action]

The coating film in the present invention blocks incident laser light, such as scattered light, incident on the elastic body at a position in close contact with the elastic body, thereby preventing deterioration of the elastic body.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a partially enlarged cross-sectional view showing a laser optical element according to an embodiment of the present invention. (15) is a high-reflectance coating film that blocks laser light incident on an elastic body (14);
(16) is a non-reflective coating film.

Next, the operation of each unit will be described. As described in the conventional example, the excimer laser uses an extremely large number of optical elements, and the scattered light (13) from these elements is filled around the laser device. If this hits the elastic body (14) such as an O-ring between the optical element body and the holder holding the optical element, impurities are generated, and the optical element is contaminated. Therefore, it is conceivable to use a metal such as Teflon, calletz, or soft indium, which is less deteriorated by scattered light. However, these are expensive and harder than rubber having the above-described structure and the like, and there is a concern that the optical element may be distorted.

Therefore, a metal such as Al or Ti was coated on the surface of the optical element in contact with the elastic body other than the portion through which the laser beam passes. Most of the scattered light (13) is reflected by the coating film (15) and does not reach the elastic body (14).
For this reason, it has become possible to use inexpensive and soft rubber or silicon rubber as the elastic body. This coating film (15) does not need to be metal, and may be a dielectric multilayer film. It is also effective to reduce the amount of scattered light by applying a non-reflective coating film (6), which is generally used in optical equipment, instead of the coating film (15). The effect is remarkable if both are shared.

Although FIG. 1 shows a window as an optical element, an etalon, a partially reflecting mirror, a lens, a beam splitter, and the like can be provided with the same high reflectance coating film as described above.
There is an effect equivalent to that of the embodiment.

As the elastic body, the O-ring (14) is shown.
It is not limited to this.

〔The invention's effect〕

As described above, according to the present invention, a coating film that blocks laser light incident on the elastic body is applied to the contact portion of the surface of the optical element body with the elastic body, so that the laser light is emitted from any direction. Even if the light is reflected or scattered, the laser light does not reach the elastic body, so that the elastic body is prevented from being deteriorated and the optical element is less likely to be contaminated.

[Brief description of the drawings]

FIG. 1 is a partially enlarged sectional view showing a laser optical element according to an embodiment of the present invention, FIG. 2 is a configuration diagram showing a laser device using a conventional laser optical element, and FIG. 3 is a conventional laser apparatus. FIG. 4 is a partially enlarged cross-sectional view showing an optical element, and FIG. 4 is a configuration diagram showing a conventional air gear etalon. (5) Window, (50) Optical element body, (51) Holder, (13) Scattered light, (14) O-ring, (15)
... High reflectance coating film In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

(57) [Claims] An optical element body for a laser, a holder for holding the optical element body, an elastic body provided between the holder and the optical element body, and a contact portion of the surface of the optical element body with the elastic body. And a laser optical element provided with a coating film for blocking laser light incident on the elastic body.