Coherent light generators – Particular pumping means – Electrical
Reexamination Certificate
2000-02-24
2004-06-01
Porta, David (Department: 2878)
Coherent light generators
Particular pumping means
Electrical
C372S055000, C372S064000
Reexamination Certificate
active
06744802
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a laser oscillating apparatus for generating a laser beam by introducing an electromagnetic wave from a waveguide into a laser tube through a plurality of fine slots formed in the waveguide wall and, for example, to a laser oscillating apparatus using a microwave as an electromagnetic wave for exciting a laser gas, an exposure apparatus using the same, and a device fabrication method using the same.
BACKGROUND OF THE INVENTION
Recently, a so-called excimer laser has attracted attention as the only high-output laser which oscillates in the ultraviolet region. This excimer laser is expected to be applied to the electronic, chemical, and energy industries, particularly processing and chemical reactions of metals, resins, glass, ceramics, and semiconductors.
The principle of function of an excimer laser oscillator will be described below. First, laser gases such as Ar, Kr, Ne, F
2
, He, Xe, and Cl
2
contained in a laser tube are excited by electron beam irradiation or discharge. Excited F atoms bond to inert Kr and Ar atoms in the ground state to generate KrF
+
and ArF
+
as molecules existing only in an excited state. These molecules are called excimers. Since excimers are unstable, they immediately emit ultraviolet rays and fall to the ground state. This phenomenon is called spontaneous emission. An excimer laser oscillator uses this to amplify as an in-phase beam in an optical resonator constructed of a pair of reflecting mirrors and extract as a laser beam.
In the case of excimer laser emission, microwaves are mainly used as a laser gas exciting source. Microwaves are electromagnetic waves having an oscillation frequency of a few hundred MHz to several tens of GHz. In this case, a microwave is introduced from a waveguide into a laser tube through a slot formed in the waveguide wall, thereby exciting a laser gas in the laser tube into a plasma.
Even if the intensity distribution of microwaves emitted through the slots is uniform, a slot array structure in which a plurality of slots are arrayed in the long-axis direction of a resonator must be formed in order to supply a microwave to a long space meeting the resonator length of a laser beam. This structure is shown in FIG.
22
. Referring to
FIG. 22
, a plurality of fine slots
302
are formed at equal intervals in a waveguide wall
301
. For convenience, the interior of a laser tube is schematically shown as an emission space.
When this slot array structure is used, regions (hatched elliptic regions in
FIG. 22
) between adjacent slots
302
are necessarily microwave non-irradiation regions. Accordingly, when a laser gas existing in the emission space is to be excited by a microwave, the existence of these non-irradiation regions produces variations in the microwave intensity. This generates plasma discharge having a nonuniform distribution as a whole.
SUMMARY OF THE INVENTION
The present invention has been made in consideration of the above problem, and has as its object to realize, for example, almost uniform electromagnetic wave radiation as a whole over the length of a laser tube in a slot array structure, thereby allowing almost uniform laser emission with minimum energy loss.
A laser oscillating apparatus according to the first aspect of the present invention comprises a waveguide in which a plurality of slots are formed and a laser tube to excite a laser gas in the laser tube by supplying an electromagnetic wave from the waveguide into the laser tube through the slot and generate a laser beam by resonating light generated by excitation of the laser gas, wherein electromagnetic waves with in-phase electric fields are supplied to the laser tube through the plurality of slots.
In the laser oscillating apparatus according to the first aspect of the present invention, the plurality of slots may be formed in a long end face or short end face of the waveguide.
Preferably, in the laser oscillating apparatus, wherein the plurality of slots and the laser tube are spaced apart from each other by a predetermined distance, and the laser oscillating apparatus further comprises a passage for guiding electromagnetic waves from the plurality of slots to the laser tube. The distance between the plurality of slots and the laser tube is preferably an integral multiple of a half-wave length. It is preferable that the width of the passage be substantially equal to a width of the slot. Preferably, the width of the passage is an integral multiple of a half-wave length of an electromagnetic wave supplied from the wave guide to the laser tube. A portion through which the passage communicates with the laser tube preferably has one or a plurality of slit portions each having a predetermined width and extending over a length of the laser tube. For example, a portion through which the passage communicates with the waveguide preferably has a width larger than a width of a portion through which the passage communicates with the laser tube.
In the laser oscillating apparatus according to the first aspect of the present invention, the passage is preferably filled with a dielectric substance. The waveguide is preferably filled with a dielectric substance. The plurality of slots are filled with a dielectric substance. In this case, the plurality of slots are preferably filled with the dielectric substance such that a surface in which the plurality of slots are formed is flattened.
In the laser oscillating apparatus according to the first aspect of the present invention, the pair of waveguides are arranged to sandwich the laser tube.
The laser oscillating apparatus according to the first aspect of the present invention preferably further comprises, for example, an adjusting portion for adjusting an impedance of each of the plurality of slots. The adjusting portion preferably includes a minute metal member attached to the short end face of the waveguide.
According to the second aspect of the present invention, there is provided a laser oscillating apparatus which includes a waveguide in which a plurality of slots are formed and a laser tube to excite a laser gas in the laser tube by supplying an electromagnetic wave from the waveguide into the laser tube through the slot, and generate a laser beam by resonating light generated by excitation of the laser gas, wherein the plurality of slots are formed in a long end face of the waveguide, and the plurality of slots are arranged at a predetermined pitch along a central line in a longitudinal direction of the long end face to be alternately located on left and right sides of the central line and spaced apart from the central line by a predetermined distance.
In the laser oscillating apparatus according to the second aspect of the present invention, electromagnetic waves with in-phase electric fields are preferably supplied to the laser tube through the plurality of slots.
In the laser oscillating apparatus according to the second aspect of the present invention, the predetermined pitch is preferably determined such that electromagnetic waves with in-phase electric fields are supplied to the laser tube through the plurality of slots.
Preferably, in the laser oscillating apparatus according to the second aspect of the present invention, the plurality of slots and the laser tube are spaced apart from each other by a predetermined distance, and the laser oscillating apparatus further comprises a passage for guiding electromagnetic waves from the plurality of slots to the laser tube. The distance between the plurality of slots and the waveguide is preferably an integral multiple of a half-wave length. Preferably, the width of the passage is substantially equal to a width of the slot. The width of the passage is preferably an integral multiple of a half-wave length of an electromagnetic wave supplied from the waveguide to the laser tube. A portion through which the passage communicates with the laser tube preferably has, for example, one or a plurality of slit portions having a predetermined width and extending over a length of the laser tube. A port
Hirayama Masaki
Ohmi Tadahiro
Ohsawa Hiroshi
Shinohara Toshikuni
Suzuki Nobumasa
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Monbleau Davienne
Porta David
LandOfFree
Laser oscillating apparatus with slotted waveguide does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Laser oscillating apparatus with slotted waveguide, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Laser oscillating apparatus with slotted waveguide will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3363991