Loss element for laser

Abstract

A laser beam loss element includes an attenuator containing multiple openings, which can be selectively placed in the path of a photon beam. The openings are arranged as parallel slots. When the attenuator is positioned in the photon beam's path, the width of each slot is wider than the width of the photon beam that strikes the attenuator.

Description

LOSS ELEMENT FOR LASERCROSS-REFERENCE TO REALTED APPLICATIONS

[0001] This application claims priority to US Application No. 63 / 730,858, filed December 11, 2024, titled LOSS ELEMENT FOR LASER, which is incorporated herein by reference in its entirety.TECHNICAL FIELD

[0002] The embodiments provided herein generally relate to a loss element for a laser.BACKGROUND

[0003] Gas discharge lasers are used in photolithography to manufacture semiconductor integrated circuits. As semiconductor manufacturing has progressed to requiring smaller and smaller feature sizes, gas discharge lasers that provide shorter wavelength and narrower bandwidth are used to support higher resolution. Excimer lasers are one type of gas discharge laser used in photolithography that can operate in the ultraviolet (UV) spectral region at high average output power to generate nanosecond pulses at reduced spectral bandwidth. A loss element, or an attenuator, may be used to reduce the optical power of the laser beam without significantly affecting other properties of the beam, such as its wavelength, coherence, or polarization.SUMMARY

[0004] In some embodiments, a loss element for a laser beam is disclosed. The loss element may comprise an attenuator including a plurality of openings configured to be movably positioned in a path of a photon beam. The plurality of openings may include multiple slots arranged parallel to each other. When the attenuator is positioned in the path of the photon beam, a width of each slot of the multiple slots may be greater than the width of the photon beam that impinges on the attenuator.

[0005] In some embodiments, a non-transitory computer readable medium that stores a set of instructions that is executable by at least on processor of a computing device to cause the computing device to perform operations is disclosed. The operations may comprise activating a laser source to output a laser beam having a first power, and activating an attenuator to reduce a power of the laser beam to a second power lower than the first power. The attenuator may include multiple slots arranged parallel to one another. Activating the attenuator may include moving the attenuator into a path of a photon beam in the laser source such that a width of each slot of the multiple slots is greater than the width of the photon beam that impinges on the attenuator.

[0006] In some embodiments, a method of varying a power of a laser beam output from a laser source is disclosed. The method may comprise activating the laser source to output a laser beam having a first power, and activating an attenuator to reduce the power of the laser beam to a second power lower than the first power. The attenuator may include multiple slots arranged parallel to oneanother. Activating the attenuator may include moving the attenuator into a path of a photon beam in the laser source such that a width of each slot of the multiple slots is greater than the width of the photon beam that impinges on the attenuator.

[0007] Other advantages of the embodiments of the present disclosure will become apparent from the following description taken in conjunction with the accompanying drawings wherein are set forth, by way of illustration and example, certain embodiments of the present invention.BRIEF DESCRIPTION OF FIGURES

[0008] The above and other aspects of the present disclosure will become more apparent from the description of exemplary embodiments, taken in conjunction with the accompanying drawings.

[0009] FIGs. 1A and IB illustrate an exemplary laser source, consistent with some embodiments of the present disclosure.

[0010] FIG. 2 illustrate an exemplary photolithography system featuring a laser source, consistent with some embodiments of the present disclosure.

[0011] FIGs. 3A and 3B illustrate portions of an exemplary laser source, consistent with some embodiments of the present disclosure.

[0012] FIGs. 4-9 illustrate exemplary laser sources, consistent with some embodiments of the present disclosure.

[0013] FIGs. 10A and 10B illustrate portions of an exemplary laser source, consistent with some embodiments of the present disclosure.

[0014] FIGs. 11A and 1 IB illustrate an exemplary attenuation system that may be used with a laser source consistent with some embodiments of the present disclosure.

[0015] FIGs. 12A-12D illustrate the irradiance pattern of photon beam on a downstream optical component in a laser source without an attenuation system.

[0016] FIG. 13 is an exemplary attenuator having an array of vertically extending racetrack-shaped openings in an attenuation system consistent with some embodiments of the present disclosure.

[0017] FIGs. 14A-14D illustrate the irradiance pattern of photon beam on a downstream optical component in a laser source using the attenuator of FIG. 13.

[0018] FIGs. 15A and 15B illustrate an exemplary attenuator of an attenuation system consistent with some embodiments of the current disclosure.

[0019] FIG. 16A is an enlarged view of a portion of the attenuator of FIG. 15 A.

[0020] FIGs. 16B-16D illustrate exemplary attenuators of attenuation systems consistent with some embodiments of the current disclosure.

[0021] FIGs. 17A-17D illustrate the irradiance pattern of photon beam on a downstream optical component in a laser source using the attenuator of FIG. 15 A.

[0022] FIGs. 18A-18F illustrate exemplary attenuators of attenuation systems consistent with some embodiments of the current disclosure.

[0023] FIGs. 19A-19C illustrate exemplary attenuation systems consistent with some embodiments of the current disclosure.

[0024] FIG. 20 is a flow chart of an exemplary method of varying the power of a laser beam using an attenuation system of the current disclosure.DETAILED DESCRIPTION

[0025] Reference will now be made in detail to exemplary embodiments, examples of which are illustrated in the accompanying drawings. The following description refers to the accompanying drawings in which the same numbers in different drawings represent the same or similar elements unless otherwise represented. The implementations set forth in the following description of exemplary embodiments do not represent all implementations. Instead, they are merely examples of apparatuses and methods consistent with aspects related to the disclosed embodiments as recited in the appended claims.

[0026] FIGs. 1A and IB are schematic illustration of an excimer laser source 10, which generates a pulsed laser beam 60 in accordance with some embodiments of the present disclosure. Excimer lasers belong to a class of pulsed lasers that operate in the ultraviolet region of the light spectrum. With reference to FIGs. 1A and IB, source 10 includes a resonator cavity 12 enclosing a discharge chamber 20. Inside the discharge chamber 20 is a gas mixture 25, which consists of a high-pressure blend of a rare gas (such as krypton, argon, or xenon) and a halogen gas (such as fluorine or krypton or chlorine) and a pair of spaced electrodes 30. In general, a rapid electrical discharge through the gas mixture 25, facilitated by the electrodes 30, results in an excitation of the gas blend to produce a plasma that includes excimer (or exciplex) combinations such as KrF, KrCl, or ArF. This excited gas blend serves as a lasing medium. The excimer combinations can decay with the emission of a photon. With proper arrangement and tuning of the resonator cavity 12 and the chamber 20, the emitted photons form the laser beam 60. Specifically, the plasma discharge produced by applying a high-frequency voltage across the electrodes 30 dissociates the excimer molecules in the gas mixture 25, leading to the emission of photons at a specific wavelength that collectively form the laser beam 60. The particular combination of the rare gas and halogen in the gas mixture 25 determines the laser's output wavelength. For instance, an argon fluoride gas mixture (ArF) produces a wavelength of 193 nm, a krypton fluoride gas mixture (KrF) results in a wavelength of 248 nm, a xenon chloride gas mixture (XeCl) yields a wavelength of 308 nm, and a xenon fluoride gas mixture (XeF) generates a wavelength of 351 nm.

[0027] A portion of the photons generated by the dissociation of the gas mixture 25 in chamber 20 is reflected back and forth through the gas mixture 25 by optical elements 42 and 44, positioned on opposite sides of the chamber. As these reflected photons (or light) traverse the gas mixture 25, they cause nearby excimer molecules to dissociate, producing additional photons in the same direction. The arrangement of optical elements 42 and 44 can differ based on the application. For example,element 42 might be a line narrowing module, while element 44 could be a partially reflective mirror or vice versa. This module includes optical components such as gratings, etalons, and prisms, which work together to select a desired wavelength and bandwidth for the output laser beam 60. The power of the laser beam 60 is influenced by several factors, including the design of the laser and its operating conditions, such as gas composition, pressure, and the amount of energy delivered to the gas mixture 25 via the electrodes 30, etc.

[0028] In some embodiments, the laser source 10 includes a loss element, or an attenuation system 52, designed to quickly reduce the power of laser beam 60 without varying its operating conditions (e.g., voltage directed to electrodes 30, gas pressure, etc.). Attenuation system 52 includes an attenuator 54 that can be removably or selectively positioned in the path of the photon beam (or light beam or laser beam) between optical elements 42 and 44. When the attenuator 54 is positioned in the photon path as illustrated in FIG. IB, it intercepts or engages the photon beam. When the attenuator 54 is thus engaged with the photon beam (or is positioned in the path of the photon beam), some photons pass (or transmit) through the attenuator 54 while others are reflected or absorbed by the attenuator 54, leading to a reduction in the power of the output laser beam 60.

[0029] The photons reflected by the attenuator 54 may be directed to a section of the laser housing wall, such as the inner wall of the resonator cavity 12, which absorbs these photons. This inner wall may have a coating of nickel or another material suitable for absorbing specific wavelengths of the laser beam (e.g., 193 nm, 248 nm, etc.). Additionally, or alternatively, the laser source 10 may incorporate a beam dump (see FIG. 1 IB) to absorb reflected photons from the attenuator 54. In some embodiments, the housing wall or the beam dump may be cooled using methods such as liquid cooling or air cooling to manage the heat resulting from the absorption of photons and thereby enhance performance.

[0030] When the attenuator 54 is removed or withdrawn from the path of the photon beam between optical elements 42 and 44 as illustrated in FIG. 1A, the photon beam passes freely between the optical elements 42 and 44, and the source 10 produces a higher-powered laser beam 60. Conversely, when the attenuator 54 is in the path of the photon beam, the emitted laser beam 60 has reduced power. For example, when the attenuator 54 is not in the path of the photon beam, the output laser beam 60 may have full power (e.g., 100%) and when the attenuator 54 is positioned in the path of the photon beam, the output laser beam may have reduced power (e.g., 50%, 60%, etc.). In some embodiments, the attenuation system 52 may be configured to vary the amount of attenuation applied to the output laser beam 60. For example, when the attenuator 54 is set at a first configuration (e.g., position, orientation, etc.) in the path of the photon beam, the laser beam 60 may have a first reduced power level (e.g., 50%), and when the attenuator 54 is set at a second configuration in the beam path, the laser beam 60 may have a second reduced power level (e.g., 70%) and so on. Such adjustments of laser power can be made either discretely or continuously.

[0031] Although not shown in FIGs. 1A and IB, attenuation system 52 may include actuators that enable the selective movement of the attenuator 54 into and out of the path of the photon beam. (See, e.g., FIGs. 11A and 1 IB.) These actuators may enable the attenuator 54 to be moved in any manner (e.g., rotated around the optical axis, translated perpendicular to the photon beam into and out of the path of the photon beam, etc.) to apply attenuation to the laser beam 60. Further details on the attenuation system 52 and its attenuator 54 is provided below.

[0032] FIG. 2 illustrates a photolithography system 100 that features a deep ultraviolet light or laser source 110, such as an excimer light source, which generates a pulsed laser beam 160 that is directed to a lithography exposure apparatus 165. Upon entering apparatus 165, the laser beam 160 passes through optics 167, which may include a reticle or mask to fdter the beam. The modified beam is then projected onto a prepared wafer 169, allowing for a pattern from the mask to be patterned onto photoresist for subsequent etching and cleaning. The lithography exposure apparatus can function as either an immersion lithography or dry system, depending on the specific application. System 100 is equipped with a control system 170 that interfaces with the components of the laser source 110 and the lithography exposure apparatus 165. This control system 170 manages various operations throughout the system 100, ensuring efficient coordination and functionality of the interconnected elements.

[0033] In the example depicted in FIG. 2, the laser source 110 features a dual chamber design that consists of a master oscillator (MO) 112, which generates a seed laser beam 124, and a power amplifier (PA) 130, configured as a regenerative ring resonator. The master oscillator 112 allows for precise tuning of parameters like center wavelength and bandwidth of the laser beam while maintaining relatively low output pulse energies. The power amplifier 130 amplifies the output (laser beam 124) from the master oscillator 112 to achieve the required power levels for the lithography apparatus 165.

[0034] The master oscillator 112 comprises a discharge chamber 114 that features two elongated electrodes 115, a gas mixture 25 as the gain medium, and a fan to circulate gas between the electrodes 115. A resonator is established between a line narrowing module 116 on one side and an output coupler 118 on the opposite side of chamber 114. The line narrowing module 116 may incorporate a diffractive optic, like a grating, for fine-tuning the spectral output of chamber 114. Additionally, the laser source 110 includes a line center analysis module 120 and a beam modification optical system 122 to adjust the size or shape of the seed laser beam 124. As previously explained with reference to FIGS. 1A and IB, the gas mixture 25 produces an ultraviolet laser beam when energized by high- voltage pulses applied to the electrodes 115.

[0035] The power amplifier 130 features a beam modification optical system 132 that receives the seed laser beam 124 from the master oscillator 112 and directs it through a discharge chamber 140 to a beam turning optical element 150, which alters the beam's direction, sending it back into the discharge chamber. If configured as a regenerative ring resonator, the laser beam circulates within thepower amplifier. The discharge chamber 140 contains elongated electrodes 141 and a gas mixture 25 serving as the gain medium, with a fan to circulate the gas. The optical system 132 facilitates the coupling of the seed laser beam 124 into the resonator and allows a portion of the amplified radiation to be extracted as the output laser beam 160. This output laser beam 160 can be analyzed for various parameters through a bandwidth analysis module 162 and may also pass through a pulse stretcher to adjust performance properties for the lithography apparatus 165.

[0036] The power amplifier 130 also features an attenuation system 152 (similar to attenuation system 52 of FIGs. 1A and IB) designed to decrease the power of the output laser beam 160. As previously explained with reference to attenuation system 52 of FIG. 1, attenuation system 152 includes an attenuator 154 (not illustrated) that can be selectively positioned into or out of the path of the photon beam within the amplifier 130 to deflect or absorb some photons — either toward the housing wall or a beam dump — and reduce the power of the output laser beam 160. The pulse energies produced by the master oscillator 112 and power amplifier 130 are influenced by their respective gains and the losses occurring within their chambers which are affected by the operating voltages applied to their discharge electrodes 115, 141. The attenuation system 152 allows adjustments to the power of the output laser beam 160 without altering the operating voltages or requiring changes to the gain medium or chamber design. The attenuation system 152 enables attenuation to be applied to the laser beam 160 while ensuring that the voltage needed for the electrodes 115 of the master oscillator 112 and the voltage needed for the electrodes 141 of the power amplifier 130 remain within acceptable limits. The control system 170 may control the attenuation system 152 and the output power of the laser beam 160.

[0037] FIGs. 3A and 3B depict an example of a power ring amplifier 130 with the attenuation system 152 positioned at an exemplary location within the amplifier. In the illustrated examples, the power ring amplifier 130 is designed as a regenerative ring resonator, which incorporates a tilted double -pass optical path through the discharge chamber 140 with an optical coupler 234 that facilitates regenerative amplification of the seed laser beam 124 from the master oscillator 112 (of FIG. 2). This optical coupler 234 serves as both the entry point and exit point for the ring resonator, with a reflectivity between about 10% to 60%, enabling pulse intensity buildup through the excited gain medium in the discharge chamber 140 during electrical discharge.

[0038] The photon beam passing through the optical coupler 234 is reflected by a mirror 236 toward the discharge chamber 140. This mirror can be configured with high reflectivity, exceeding 90% at or near the desired wavelength and polarization angle. The beam then travels through the discharge chamber 140 and reaches a beam turning optical element 150, implemented as prism 251. The photon beam reflects off two surfaces of the prism 251, re-entering the discharge chamber 140 along a different path. Some of the photons that then reach the optical coupler 234 are reflected back into the ring resonator, while some are transmitted as the output laser beam 160. The beam turning optical system 150 consists of precision devices made from optical materials like calcium fluoride (CaF2)with finely finished surfaces. While a prism 251 is depicted, this system can include various optical devices that redirect the beam back into the discharge chamber 140.

[0039] Before entering the discharge chamber 140, the photon beam is typically compressed to match the gain medium's transverse size. Upon exiting, the beam is expanded. A beam magnification / de-magnification system 238, positioned between the discharge chamber 140 and the optical components, facilitates this compression and expansion, utilizing multiple optical elements such as prisms. One specific configuration of the beam magnification / de-magnification system 238 is illustrated in FIG. 3B. This system comprises three prisms: first prism 242, second prism 244, and third prism 246. The first and third prisms 242, 246 work in tandem to compress the incoming laser beam 124, with the third prism 246 also aligning the beam with the windows of the discharge chamber 140. The third prism 246 also redirects the reflected outgoing photon beam from the discharge chamber 140 to the second prism 244, which then magnifies the beam before it reaches the optical coupler 234, where a portion of the beam is reflected back into the ring resonator and the remainder is transmitted as the output laser beam 160. The optical components, including the optical coupler 234, mirror 236, prisms 242, 244, 246, 251, and the chamber windows, are typically made of a crystalline material designed to efficiently transmit high-energy light or laser pulses at deep ultraviolet wavelengths with minimal loss. Common materials used for these components include calcium fluoride (CaF2), magnesium fluoride (MgF2), and fused silica.

[0040] In the power ring amplifier 130 depicted in FIG. 3A, the attenuation system 152 is positioned so that it may operate between the discharge chamber 140 and the beam modification optical system 132. However, this placement is merely illustrative. FIGs. 4-9 illustrate various exemplary positions for the attenuation system 152 within the power ring amplifier 130. In different figures, the attenuation system 152 is mounted along various points in the path of the photon beam, allowing it to selectively deflect a portion of the photons in the photon beam and reduce the power of the output laser beam 160. For example, in FIG. 4, the attenuation system 152 is placed inside the beam modification optical system 132 so that it may operate in the path of the photon beam as it travels from the mirror 236 toward the beam magnification / de-magnification system 238. In FIG. 5, the attenuation system 152 is placed inside the beam modification optical system 132 so that it may operate in the path of the photon beam as it travels from the beam magnification / de-magnification system 238 toward the optical coupler 234. In FIG. 6, the attenuation system 152 is placed inside the beam modification optical system 132 so that it may operate in the path of the photon beam as it travels from the discharge chamber 140 toward the beam magnification / de-magnification system 238. In FIG. 7, the attenuation system 152 is placed so that it may operate in the path of the photon beam as it travels from the discharge chamber 140 toward the prism 251. In FIG. 8, the attenuation system 152 is placed so that it may operate in the path of the photon beam as it travels from the beam magnification / de-magnification system 238 toward the discharge chamber 140. In FIG. 9, theatenuation system 152 is placed so that it may operate in the path of the photon beam within the beam magnification / de-magnification system 238.

[0041] An atenuation system 152 may also be positioned within a component of power ring amplifier 130. For example, FIGs. 10A and 10B illustrate an atenuation system 152 positioned within the beam magnification / de-magnification system 238 of the power ring amplifier 130 so that it may operate along the path of the photon beam traveling from the first prism 242 to the third prism 246. In FIG. 10A, the atenuator 154 of the atenuation system 152 is shown withdrawn from the path of the photon beam (or disengaged with the photon beam), allowing the photon beam to pass through freely, resulting in full (100%) power for the output laser beam 160. In contrast, FIG. 10B shows the atenuator 154 positioned in the path of photon beam, causing some photons to be deflected, thereby lowering the power of the output laser beam 160. As previously explained, atenuation system 152 features an actuator 156 that responds to signals from the control system 170, enabling the atenuator 154 to be adjusted between various positions. For instance, the atenuator 154 may be set to an engaged position where the atenuator 154 is in the path of the photon beam and a disengaged (or unengaged) position where the atenuator 154 is not in the path of the photon beam. In some embodiments, the actuator 156 may move the atenuator 154 between multiple engaged positions to provide varying levels (e.g., 50%, 60%, 70%, etc.) of atenuation of the output laser beam.

[0042] While a single atenuation system 152 is shown in the exemplary embodiments of FIGs. 2- 10B, in some applications, a laser source may feature multiple atenuation systems 152. Additionally, although FIGs. 2-10B depict the atenuation system 152 as being located in the power ring amplifier 130 of a dual chamber laser source 110, one or more atenuation systems 152 may additionally or alternatively be positioned in the master oscillator 112. These atenuation systems 152 can be placed anywhere within the laser source to provide atenuation as needed. Regardless of the number of atenuation systems 152 present or their placement within the laser source, each atenuation system 152 includes an atenuator 154 that can be selectively moved into the path of a photon beam to reflect a portion of the photons, thereby reducing the power of the output laser beam 160.

[0043] FIGs. 11A and 1 IB illustrate an exemplary atenuation system 252 of the current disclosure. Atenuation system 252 may be used with any type of laser source (including but not limited to laser source 10 in FIG. 1, laser source 110 in FIG. 2, etc.). Atenuation system 252 is illustrated as being positioned to modify a photon beam 500, shown as propagating in a +Z direction. Atenuation system 252 consists of an atenuator 254 connected to an actuator 256, which is designed to move the atenuator 254 between a disengaged position (shown in FIG. 11A) and an engaged position (shown in FIG. 1 IB). In the disengaged position, the atenuator 254 is located outside the path of the photon beam 500, while in the engaged position, it is placed in the path of the photon beam 500. It should be noted that although FIGs. 11A and 1 IB show the atenuator moving vertically up and down (e.g., along the Y-axis) between its engaged and disengaged positions, this is only exemplary. In general,the attenuator 254 may move in any manner (e.g., side-side, rotate, etc.) between its engaged and disengaged positions.

[0044] The attenuator 254 features a plate 258 with a pattern of holes or openings 260 that selectively allow photons passing through the openings 260 to continue, while blocking those photons that strike the material (e.g., surface) of the plate 258. The plate 258 may be constructed from an opaque material that blocks photons from passing through. In some embodiments, the material of the plate may block all wavelengths of light, while in other embodiments, it may be selectively opaque to a specific wavelength or range of wavelengths (e.g., the wavelength of a UV laser).

[0045] The plate 258 may reflect photons that strike its surface away from the beam path. For example, photons that hit the surface of the plate 258 could be redirected towards the inner walls of the enclosure housing the attenuation system 252 or to a beam dump 261 designed to absorb these photons. As mentioned earlier, in some embodiments, the enclosure walls or the beam dump 261 may be cooled to manage heat that results from the absorption of the photons. The surface of the plate 258 that interacts with the photon beam 500 may be highly reflective to minimize heating due to photon absorption. It is also contemplated that, in some embodiments, the plate 258 may be cooled (e.g., liquid cooling, air cooling, etc.). In some embodiments, the surface of the plate 258 may be polished (e.g., polished aluminum) to achieve the desired reflectivity. In some embodiments, the surface roughness of the plate 258 may be less than or equal to (<)30 microns (or < 20 microns in some cases). To ensure sufficient reflectivity, in some embodiments, the portion of the plate surface that interacts with the photon beam 500 may have a roughness of < about 10 microns.

[0046] As used in this disclosure, the term “about” indicates that the quoted value (e.g., roughness in this case) is approximate and allows for practical variations resulting from manufacturing processes. For example, manufacturing processes often introduce variations that cause the actual value (e.g., roughness value in this case) to differ slightly from the quoted value due to factors like material properties, tooling precision, and production techniques. Tolerance stack-ups can also impart some variability. The term about is used to cover such expected variations in a quoted value.

[0047] In some implementations, plate 258 may be made from a metallic, conductive material to enhance heat dissipation. For instance, a polished copper substrate may be used, onto which a reflective coating, such as aluminum, is applied. In some implementations, the plate 258 may be made of aluminum. To prevent oxidation, a protective overcoat may be added over the reflective layer. This overcoat can be made from materials that reflect or transmit light at the central wavelength, such as dielectric layers or magnesium fluoride. For light at 193 nm (or the wavelength of the laser beam), aluminum can achieve 90% reflectance, while magnesium fluoride can increase reflectance to over 95%. In some embodiments, only the frontside (e.g., the side that receives the photon beam) of the plate 258 may be coated. In some embodiments, the backside (e.g., the side facing the downstream optical component) of the plate 258 may also be coated to reflect any additional beams, such as Fresnel beams from other optics within the power amplifier 130.

[0048] When a light beam or a photon beam passes through the holes in a plate (e.g., openings 260 in plate 258), it produces a diffraction pattern due to the way light waves behave as they spread out and interact with each other. This phenomenon occurs because each hole acts as a source of light waves, causing the waves to spread and overlap as they propagate beyond the plate 258. When two light waves meet and have the same frequency and phase — meaning they oscillate at the same rate and reach their maximum amplitude at the same time — their wave amplitudes combine, resulting in constructive interference. This reinforcement creates areas where the intensity of the light is stronger. On the other hand, when two light waves are out of phase by half a period (e.g., one wave is at its minimum while the other is at its maximum), they cancel each other out, leading to destructive interference, where the intensity of the light is weakened or completely canceled.

[0049] As the photon beam 500 passes through the holes 260 in the plate 258, this interplay of constructive and destructive interference generates a diffraction pattern, which causes the intensity of the beam to vary along its path. In areas where constructive interference occurs, the peak irradiance which is the maximum radiant energy per unit area — can be significantly higher than the original input irradiance. This localized increase in energy can be problematic, as the high peak irradiance may exceed the damage threshold of downstream optical components in the system, potentially leading to overheating, degradation, or permanent damage to these components (e.g., bum optical coatings, etc.) particularly when high-power lasers are involved.

[0050] The diffraction pattern of a photon beam passing through openings on a plate (e.g., openings 260 in plate 258) is strongly influenced by the pattern (e.g., arrangement, shape, size, and spacing) of the openings. Variations in any of these parameters (e.g., arrangement, shape, size, and spacing) of the openings 260 affects how the light waves spread out and interfere after passing through the openings 260, which in turn determines the structure of the resulting irradiance pattern and peak irradiance at a downstream location (e.g., on the downstream optical component that receives the photon beam from the attenuator 254).

[0051] FIGs . 12A- 12D depict the irradiance pattern of a 1 -watt photon beam having a top-hat intensity profile at the location of a downstream optical component. FIG. 12A is a contour plot that visually represents the light intensity distribution across a two-dimensional area perpendicular to the photon beam, while FIG. 12B zooms in on the irradiance pattern within a selected region A in FIG. 12A. FIGs. 12C and 12D are graphs of the irradiance (in Watts / mm2) along the lines X1-X2 and Y1-Y2 marked in FIG. 12B. Note that the peaks seen at the edges of the beam profile in FIGs. 12C and 12D are artifacts caused by edge effects from a top-hat beam profile. The actual beam profile irradiance falls off at the edges so these peaks can be disregarded. Based on these figures, the peak irradiance in the center region of the photon beam is approximately 30 milli Watts per mm2(mW / mm2).

[0052] FIG. 13 illustrates an exemplary attenuator 354 featuring an array of rectangular or racetrackshaped openings 360 extending along the Y-axis (or vertically extending racetrack-shaped openings). FIGs. 14A-14D illustrate the irradiance pattern at a downstream optical element when the attenuator354 of FIG. 13 is placed upstream of this optical element. The power and profde of the input photon beam (in FIGs. 14A-14D) is comparable to that in Figures 12A-12D — a 1-watt photon beam with a top-hat intensity profde. FIG. 14A shows a contour plot of irradiance on a plane perpendicular to the photon beam at the optical element, while FIG. 14B focusses on the irradiance pattern within region A of FIG. 14A. FIGs. 14C and 14D are plots of the irradiance along lines X1-X2 and Y1-Y2 in FIG. 14B. Ignoring edge artifacts, FIGs. 14C and 14D indicate that the peak irradiance (Ipeak) at the center region of the beam has increased to around 46 mW / mm2(up from 30 mW / mm2without the attenuator 354). This translates to a 57% increase in peak intensity at the downstream optical element, potentially leading to damage and a reduced lifespan of the optical component. For instance, if a beam reverser prism is the downstream optical element, the 57% rise in peak intensity could decrease the prism’s lifespan by a factor of approximately 2.5.

[0053] The intensity distribution and peak irradiance (Ipeak) of a photon beam at a downstream optical component are significantly affected by the arrangement, shape, size, and spacing (these parameters are individually or collectively referred to herein as “pattern”) of the openings in the attenuator. In attenuation system of the current disclosure, the pattern of openings in the attenuator are such, in addition to providing the desired attenuation of the output laser beam 160, the peak irradiance (Ipeak) at a downstream optical component (e.g., the optical component that receives the photon beam from the attenuator) is below its damage threshold. In some embodiments, the pattern of openings in the attenuator are specifically designed such that the peak irradiance at the downstream optical component does not increase due to the presence of the attenuator (e.g., IPeak(wlth atenuator)< Ipeak(wlthoutattenuator) [n someembodiments, the pattern of openings in the attenuator are specifically designed such that the peak irradiance at the downstream optical component does not substantially increase due to the presence of the attenuator (e.g., Ipeak(wlth attenuator) < lpeak<wlthoutattenuator) + | %.Or +5% or +10% or +25% or +40%). In some embodiments, the peak irradiance at the downstream optical component may be unaffected by the presence of the attenuation system 252 in the beam path (e.g., Ipeak(wlthattenuator) ~ ipeak(without attenuator)) |n someembodiments, when using an attenuator of the current disclosure, the diffraction pattern at the location of the downstream optical component may be largely uniform. Numerical simulations or experiments may be used to determine the specific pattern of openings in the attenuator that result in the above-described acceptable peak irradiance at the downstream optical component.

[0054] FIGs. 15A and 15B illustrate an exemplary attenuator 254 of an attenuation system 252 (e.g., of FIGs. 11A-1 IB) consistent with some embodiments of the current disclosure. Note that the actuator (256 of FIGs. 11A-1 IB) and features (e.g., screw holes, grooves, etc.) of the attenuator 254 that engage with the actuator are not shown in FIGs. 15A and 15B. FIG. 15A illustrates the disengaged position of the attenuator 254 where it is located outside the path of a photon beam 500, and FIG. 15B illustrates its engaged position where it is placed in the path of the photon beam 500. As previously explained with reference to FIGs. 11A and 1 IB, attenuator 254 includes a plate 258 with a plurality ofopenings 260 that selectively allow photons passing through the openings 260 to continue, while blocking those photons that strike the surface of the plate 258. The openings 260 may be evenly distributed on the plate 258. In various embodiments, each of the openings may have the shape of a slot. In various embodiments, the openings may all have the same dimensions. The number of openings may be selected based on the application (e.g., 5-10 openings, 10-15 openings, 15-20 openings, 20-25 openings, 25-30 openings, 25-35 openings, 20-50 openings, 40-100 openings). The pattern of openings 260 may also be configured to provide the desired attenuation of the power of the output laser beam (laser beam 160 of FIG. 2) and result in an acceptable peak irradiance at the downstream optical component. For example, the arrangement, shape, size, and spacing of the openings 260 may be such that, in addition to providing the desired level of attenuation of the output laser beam from the laser source, the presence of the attenuator 254 does not cause an increase in peak irradiance (e.g., Ipeak(wlth attenuator)< |peaki"ithout attenuator^at adownstreamoptical component that receives the photon beam from the attenuator 254.

[0055] The attenuation of the output laser beam 160 (see FIG. 2) by the attenuator 254 is a function of the ratio of the area of the openings 260 (or the total open area of the plate 258) to the overall area of the attenuator 254 where the photon beam 500 strikes. As illustrated in FIG. 15B, the total area refers to the beam profile area on the attenuator 254 in a plane perpendicular to the photon beam, while the area of the openings represents the fraction of this total area occupied by the openings 260. For instance, if the photon beam 500 travels through the attenuator 254 without any loss (e.g., 100% transmission), the transmission factor is 1 and attenuation factor is 0. Conversely, if the area of the openings 260 constitute half of the total area covered by the beam profile, the transmission and attenuation factors would be 0.5. Therefore, the attenuation and transmission factors can range from 0 to 1, where an attenuation factor of 1 (or a transmission factor of 0) signifies complete blockage (100% loss) of the beam, and an attenuation factor of 0 (or a transmission factor of 1) indicates no loss, allowing the beam to pass through entirely.

[0056] In some embodiments, pattern of openings 260 in the attenuators 254 of the current disclosure may be such that they provide an attenuation factor between 0.2-0.5 (or a transmission factor between 0.5-0.8), or an attenuation factor between 0.3-0.4 (or a transmission factor between 0.6-0.7). In some embodiments, the pattern of openings 260 may be such that the resulting attenuation factor is 0.35-0.4 or about 0.37 (e.g., 0.36-0.38). An attenuation factor of about 0.37 means that in the engaged configuration of the attenuator 254, roughly 63% of the photon beam 500 that strikes the attenuator 254 passes through its openings 260, while the remaining approximately 37% is reflected by the plate 258.

[0057] As explained with reference to FIGs. 13 and 14A-14D, an attenuator 354 with an array of vertically extending (e.g., extending along the Y-axis) racetrack-shaped openings results in a 57% increase in the peak intensity on a downstream component, which may lead to a reduction in life of the component. The pattern (e.g., arrangement, shape, size, and spacing) of openings 260 in attenuator254 of FIGs. 15A-15B is such that the peak irradiance (Ipeak) on the downstream optical component is not increased (e.g., [pcak<" 'th attenuator <Ipeak(without attenuator))

[0058] FIG. 16A is an enlarged view of the attenuator 254 of FIG. 15A showing a plurality of adjacent openings 260 defined on the plate 258 of the attenuator 254. As shown in FIG. 16A, the openings 260 may be slots or slits that extend along the X-axis (or extend horizontally). In some embodiments, these horizontally extending openings 260 may be substantially rectangular in shape. “Substantially” rectangular openings refer to openings that are primarily rectangular in shape but may (but not necessarily) feature rounded comers instead of sharp angles. In various embodiments, the slots may all have the same height and / or the same width. The height (H) (or the distance in the Y direction) of each opening 260 may vary from 0.43-0.47 mm, and the pitch (P) of the openings 260 (or the center-center distance of adjacent openings in the Y direction) may vary from 0.68-0.75 mm. In some embodiments, the height (H) of the openings 260 may be between 0.44-0.46 mm (or about 0.45 mm), and the pitch (P) may be between 0.70-0.72 mm (or about 0.71 mm). Simulations or experiments indicate that, for a 193 nm laser, an attenuator 254 having substantially rectangular openings 260 with height (H) and pitch (P) within the above-described range ensures that the peak irradiance (Ipeak) on the downstream optical component is not increased (e.g., Ipeak(wlth attenuator)< IPeak(wlthout attenuator)), thus preserving the reliability and lifespan of the component despite the presence of the attenuator 254.

[0059] In general, as illustrated in FIG. 15B, the width (W) of openings 260 is greater than the width of the photon beam 500, and this width can vary depending on the application. For example, the plurality of openings 260 are slots arranged parallel to each other with the width (W) of each slot greater than a width of the photon beam 500 that impinges on the attenuator 254. In some embodiments, as shown in FIG. 16A, the openings 260 may extend substantially across the entire width of the attenuator 254. The term “substantially” in this context indicates that while the openings 260 do not reach the edges of the attenuator 254, they occupy most of the width, framed by narrow sections (or frame 262) of the plate 258 to preserve structural integrity. For example, a slot may have a width that is 70%, 75%, 80%, 85%, 90%, 95%, 99% of the width of the attenuator, or may have a width between these values (e.g. between 70% and 75%, between 75% and 80%, between 80% and 85%, between 85% and 90%, between 90% and 95%, between 95% and 99%). It is also possible for only one side of the openings 260 to have a frame 262, as depicted in FIG. 16B. In FIG. 16B, the same end of each opening 260 is shown as having a frame 262, while the opposite end is open. In some embodiments, adjacent openings 260 may have their opposite ends open.

[0060] Additionally, or alternatively, as shown in FIG. 16A, the bottom end of the array of openings 260 may also feature a narrow framing section (frame 264) to support the structure. In some instances, like in FIG. 16C, the height (S) of frame 264 can be half the height of the plate material between other openings 260. Conversely, as illustrated in FIG. 16D, the bottom-most opening 260 might be entirely open at its bottom end. These configurations of openings 260 are merely exemplary. In general, aplurality of horizontally extending openings 260 may be arranged in any manner on the attenuator 254.

[0061] FIGs. 17A-17D depict the irradiance pattern of a 1-watt photon beam with a top-hat intensity profde on a downstream optical element when an attenuator 254 (e.g., of FIGs. 15A-15B) is positioned upstream of the optical element. In this example, the downstream optical element is located at a distance of 1370 cm away from the attenuator 354. With reference to FIG. 16A, the attenuator 254 includes a plurality of horizontally extending slot-like openings 260 having a height (H) between 0.44-0.46 mm and pitch (P) between 0.70-0.72 mm. This pattern of openings 260 provides an attenuation of about 37% (or an attenuation factor of 0.37). FIG. 17A shows the contour plot of irradiance on the optical element, while FIG. 17B shows the irradiance pattern within region A of FIG. 17A. Meanwhile, FIGs. 17C and 17D plot the irradiance along lines X1-X2 and Y1-Y2 of FIG. 17B. From these figures, the peak irradiance (Ipeak) in the center region of the beam profile is measured at 28 mW / mm2, reflecting a 6.67% reduction from the 30 mW / mm2peak irradiance observed without the attenuator. Thus, in addition to providing the desired level of attenuation (e.g., about 37%), the use of attenuator 254 reduces the peak irradiance on the downstream optical component (e.g., Ipcak<" nh attenuator; <Ipeak(without attenuator))

[0062] The above described pattern of openings 260 in the attenuator 254 ensures that the peak irradiance on the downstream optical element does not increase for a 193 nm laser. However, different laser configurations (e.g., wavelengths of the laser beam, designs of the source, different placement of optical components, etc.) may necessitate a different pattern of attenuator openings to ensure that the peak irradiance on the downstream optical element does not increase for that specific laser configuration. For instance, to maintain consistent peak irradiance for a 248 nm laser, the suitable height (H) of the attenuator openings may range from 0.4-0.7 mm (or 0.5-0.6 mm), while the suitable pitch (P) could be between 0.8-1.2 mm. The shape of the attenuator openings may also necessitate changes (e.g., from horizontally extending substantially rectangular openings to a different shape of openings) to ensure that the peak intensity does not increase for different laser configurations (e.g., for a 248 nm laser).

[0063] For example, as illustrated in FIGs. 18A-18F, the attenuator may include circular openings (single size or multiple sizes of circular openings), oval openings, horizontal racetrack openings, vertical openings, a mix or different shapes of openings, etc.). Suitable opening patterns for different laser configurations may be determined using simulations or experiments. Regardless of the specific laser configuration, the openings may be evenly distributed on the attenuator and have a pattern that provides the desired level of attenuation (e.g., 37%, etc.) of the output laser beam while keeping the peak irradiance on the downstream optical element less than or equal to than that observed without the attenuator (e.g., Ipeak(wlth attenuator)< |peaki"ithout attenuator;) jn t ebeampath, or less than some limited value above the peak irradiance observed without the attenuator. In some embodiments, the pattern of theopenings may be designed to keep the peak irradiance on the downstream optical element below the damage threshold of that component.

[0064] In the previous discussion, an attenuator was employed to deliver a single level of attenuation to the output laser beam 160. For instance, when the attenuator 254 is disengaged from the photon beam 500 (as shown in FIG. 15 A), the output laser beam 160 operates at full power, while engaging the attenuator 254 (seen in FIG. 15B) results in reduced power. In some embodiments, an attenuator can offer multiple attenuation levels for the output laser beam 160, while ensuring that the peak irradiance on a downstream optical element remains equal to or less than that observed without the attenuator.

[0065] In FIG. 19A, an attenuator 554 with an array of openings 560 is positioned in the path of a photon beam 500 (e.g., using an actuator as described previously). The attenuator 554 may be rotated about an axis 580 perpendicular to the photon beam 500 (e.g., about an axis 580 extending along the X-axis) to change the attenuation factor. For example, as illustrated in FIG. 19A, when the attenuator 554 is perpendicular to the photon beam 500, a smaller area of the openings 560 (e.g., a smaller number of horizontally extending openings) is in the path of the photon beam 50. And when the attenuator 554 is rotated, a larger area of the openings 560 (e.g., a greater number of horizontally extending openings) is exposed to the photon beam 500. By positioning the attenuator 554 at different angles with respect to the photon beam 500, the attenuation factor may be continuously varied.

[0066] FIG. 19B illustrates an attenuator 654 that may be rotated about an axis 680 extending parallel to the optical axis of the photon beam 500 (e.g., the Z-axis) to change the attenuation of the output laser beam 160. Attenuator 654 includes multiple sets of openings 660A-660D each having a different pattern. For example, openings 660A may be a first set of horizontally extending openings (see, e.g., FIG. 16A) having a first value of height (H) and pitch (P), openings 660B may be a second set of horizontally extending openings having a second value of height (H) and pitch (P), etc. Rotating the attenuator 654 to engage different sets of openings 660A-660D with the photon beam 500 changes the attenuation of the laser beam. Attenuator 654 may also include an opening 660C that allows the photon beam 500 to pass through without any attenuation. Rotating the attenuator 654 (about axis 680) such that opening 660C is in the path of the photon beam 500 will allow the output laser beam 160 to have full power. Thus, in some embodiments, attenuator 654 may not be removed from the path of the photon beam 500 to disengage it from the photon beam 500. Instead, the attenuator 654 may be rotated such that opening 660C is in the path of the photon beam 500.

[0067] In FIG. 19C, an attenuator 754 may include two plates 758A and 758B, each having a plurality of openings 760A and 760B. The plates 758 A and 758B may be slidably coupled together to enable relative movement (e.g., along the Y-axis, along the X-axis, etc.) between them. When the attenuator 754 is engaged with a photon beam, the photon beam passes through passageways formed by the aligned openings 760A, 760B of both the plates 758A, 758B. For example, a passageway is formed by an aligned pair of openings 760A, 760B. Sliding the plates 758A, 758B relative to oneanother (e.g., along the Y-axis) changes the size of the passageway through which the beam passes. When the attenuator 754 is engaged with a photon beam, different levels of attenuation may be applied by sliding the plates 758 A, 758B relative to one another. A control system (e.g., control system 170 of FIG. 2) may be used to activate (e.g., rotate, move, etc.) the attenuators 554, 654, 754 and provide the desired level of attenuation of the output laser beam.

[0068] Although the loss element of the laser source is described as an attenuator with a plurality of openings in the discussion above, this is only exemplary. In some embodiments, an optical beam splitter (e.g., a partially reflective optical component) may be used as the loss element. For example, to achieve an attenuation of 37%, a beam splitter that transmits 63% of the photons in a photon beam and reflects the remaining 37% of the photons may be positioned in the path of the photon beam. The beam splitter will not produce diffraction of the beam downstream of the beam splitter, and the peak irradiance may be reduced by the reflectivity of the beam splitter. The beam splitter may be positioned at any location in the laser source. For example, a beam splitter may be positioned at location where an attenuation system 252 may be positioned. In some embodiments, as described with reference to the attenuator 254, the beam splitter may be selectively positioned in the path of the photon beam to reduce the power of the output laser beam 160 when needed. For example, the beam splitter may be placed in the path of the photon beam (e.g., using an actuator) to reduce the power of the laser beam and removed from the path of the photon beam when full power of the beam is desired. The beam splitter may be made from any material and have any construction (e.g., reflective coatings, etc.) that can reliably and efficiently transmit the desired percentage (e.g., 63%) of deep UV light and reflect the remainder (e.g., 37%). For example, in some embodiments, materials such as calcium fluoride (CaF2) or fused silica may be used to construct the beam splitter.

[0069] FIG. 20 is a flow chart of an exemplary method 800 that may be used to vary the power of the output laser beam (e.g., laser beam 160) of a laser source (e.g., laser source 10, 110, etc.). The method 800 can be executed using systems and devices described above. In step 810, the laser source may be activated to output a laser beam having full (e.g., 100%) power. For example, high voltage electric pulses may be applied to a gain medium (e.g., gas mixture 25) through electrodes (e.g., electrodes 30, 141, etc.) in a discharge chamber (e.g., chamber 20, 140, etc.) to generate photon beam (e.g., photon beam 500) and output a laser beam (e.g., laser beam 160).

[0070] In step 820, a loss element may be activated to reduce the power of the output laser beam (e.g., laser beam 160). In some embodiments, in step 820, an actuator (e.g., actuator 256) may be activated to move the attenuator (e.g., attenuator 154, 254, 454A-454F, 554, 654, 754) of an attenuation system (e.g., attenuation system 252) and position it in the path of the photon beam. The attenuator includes a plurality of openings (e.g., openings 260) having a pattern that provides the desired level of attenuation (e.g., 37%, etc.) of the output laser beam while keeping the peak irradiance on a downstream optical element (that receives the photon beam from the attenuator) less than or equal to the peak intensity on that component without the attenuator in the beam path (e.g.,Ipeak(wlth attenuator)< ipeak(wlthout attenuator>). in some embodiments, step 820 may also include activating the attenuator to change the attenuation of the laser beam. For example, the attenuator may be moved (e.g., translated, rotated, etc.) to change the pattern of openings in the path of the photon beam and change the attenuation of the output laser beam.

[0071] In some embodiments, in step 820, a beam splitter may be moved into the path of the photon beam to reduce the power of the output laser beam. The beam splitter may transmit a portion and reflect a portion of the incident photon beam to reduce the power of the output laser beam.

[0072] In some embodiments of the current disclosure, a non-transitory computer readable medium may be provided that stores instructions for a processor of a controller or control system (e.g., control system 170 of FIG. 2) to carry out, among other things, operations associated with the methods described herein (including the operations associated with method 800 of FIG. 20). Common forms of non-transitory media include, for example, a floppy disk, a flexible disk, hard disk, solid state drive, magnetic tape, or any other magnetic data storage medium, a Compact Disc Read Only Memory (CD- ROM), any other optical data storage medium, any physical medium with patterns of holes, a Random Access Memory (RAM), a Programmable Read Only Memory (PROM), and Erasable Programmable Read Only Memory (EPROM), a FLASH-EPROM or any other flash memory, Non-Volatile Random Access Memory (NVRAM), a cache, a register, any other memory chip or cartridge, and networked versions of the same.

[0073] The embodiments may further be described using the following clauses:1. A loss element for a laser beam, comprising: an attenuator including a plurality of openings configured to be movably positioned in a path of a photon beam, the plurality of openings including multiple slots arranged parallel to each other, wherein, when the attenuator is positioned in the path of the photon beam, a width of each slot of the multiple slots is greater than the width of the photon beam that impinges on the attenuator.2. The loss element of clause 1, wherein the multiple slots comprises a set of 25-35 slots having substantially equal heights and widths.3. The loss element of any one of clauses 1 -2, wherein each of the multiple slots extend substantially across a width of the attenuator.4. The loss element of clause 1, wherein a height of each slot of the multiple slots in a direction perpendicular to the width is between 0.43-0.47 mm.5. The loss element of clause 1, wherein a height of each slot of the multiple slots is between 0.44-0.46 mm.6. The loss element of clause 5, wherein the height of each slot of the multiple slots is about 0.45 mm.7. The loss element of any one of clauses 1-2 and 4-6, wherein a pitch of the multiple slots in a direction perpendicular to the width is between 0.68-0.75 mm.8. The loss element of clause 7, wherein the pitch is between 0.70-0.72 mm.9. The loss element of clause 8, wherein the pitch is about 0.71 mm.10. The loss element of any one of clauses 1-2 and 4-6, further comprising a mount that enables removal and reinsertion of the attenuator from the path of the photon beam.11. The loss element of any one of clauses 1 -2 and 4-6, further comprising an actuator coupled to the attenuator, wherein the actuator is configured to move the attenuator into the path of the photon beam and remove the attenuator from the path of the photon beam.12. The loss element of any one of clauses 1-2 and 4-6, wherein the attenuator includes a plate with the plurality of openings defined thereon, the plate being configured to reflect photons of the photon beam that impinges on a surface of the plate.13. The loss element of clause 12, wherein the surface of the plate has a roughness less than or equal to about 30 microns.14. The loss element of clause 13, wherein the surface of the plate has a roughness less than or equal to about 20 microns.15. The loss element of clause 14 wherein the surface of the plate has a roughness less than or equal to about 10 microns.16. The loss element of clause 12, wherein the plate includes aluminum.17. The loss element of clause 12, wherein the plate includes copper coated with aluminum.18. A non-transitory computer readable medium that stores a set of instructions that is executable by at least on processor of a computing device to cause the computing device to perform operations, the operations comprising: activating a laser source to output a laser beam having a first power; and activating an attenuator to reduce a power of the laser beam to a second power lower than the first power, the attenuator including multiple slots arranged parallel to one another, wherein activating the attenuator includes moving the attenuator into a path of a photon beam in the laser source such that a width of each slot of the multiple slots is greater than the width of the photon beam that impinges on the attenuator.19. The non-transitory computer readable medium of clause 18, wherein the operations further comprise reactivating the attenuator to move the attenuator out of the path of the photon beam to increase the power of the laser beam to the first power.20. The non-transitory computer readable medium of clause 18, wherein the operations further comprise reactivating the attenuator to change the power of the laser beam to a third power different from the first power and the second power.21. The non-transitory computer readable medium of clause 18, wherein the multiple slots comprises a set of 25-35 slots having substantially equal heights and widths.22. The non-transitory computer readable medium of any of clauses 18-21, wherein each of the multiple slots extend substantially across a width of the attenuator.23. The non-transitory computer readable medium of clause 18, wherein a height of each slot of the multiple slots in a direction perpendicular to the width is between 0.43-0.47 mm.24. The non-transitory computer readable medium of clause 23, wherein the height of each slot of the multiple slots is between 0.44-0.46 mm.25. The non-transitory computer readable medium of clause 24, wherein the height of each slot of the multiple slots is about 0.45 mm.26. The non-transitory computer readable medium of any of clauses 18-21 and 23-25, wherein a pitch of the multiple slots in a direction perpendicular to the width is between 0.68-0.75 mm.27. The non-transitory computer readable medium of clause 26, wherein the pitch is between 0.70-0.72 mm.28. The non-transitory computer readable medium of clause 27, wherein the pitch is about 0.71 mm.29. The non-transitory computer readable medium of any of clauses 18-21 and 23-25, wherein activating the attenuator includes energizing an actuator to move the attenuator into the path of the photon beam.30. The non-transitory computer readable medium of any of clauses 18-21 and 23-25, wherein the attenuator includes a plate with the multiple slots defined thereon, and wherein moving the attenuator into the path of the photon beam includes reflecting photons of the photon beam that impinges on a surface of the plate.31. The non-transitory computer readable medium of clause 30, wherein the surface of the plate has a roughness less than or equal to about 10 microns.32. The non-transitory computer readable medium of clause 30, wherein the plate includes aluminum.33. The non-transitory computer readable medium of clause 30, wherein the plate includes copper coated with aluminum.34. A method of varying a power of a laser beam output from a laser source, comprising: activating the laser source to output a laser beam having a first power; and activating an attenuator to reduce the power of the laser beam to a second power lower than the first power, the attenuator including multiple slots arranged parallel to one another, wherein activating the attenuator includes moving the attenuator into a path of a photon beam in the laser source such that a width of each slot of the multiple slots is greater than the width of the photon beam that impinges on the attenuator.35. The method of clause 34 further comprising reactivating the attenuator to move the attenuator out of the path of the photon beam to increase the power of the laser beam to the first power.36. The method of clause 34 further comprising reactivating the attenuator to change the power of the laser beam to a third power different from the first power and the second power.37. The method of clause 34, wherein the multiple slots comprises a set of 25-35 slots having substantially equal heights and widths.38. The method of any of clauses 34-37, wherein each of the multiple slots extend substantially across a width of the attenuator.39. The method of clause 34, wherein a height of each slot of the multiple slots in a direction perpendicular to the width is between 0.43-0.47 mm.40. The method of clause 39, wherein the height of each slot of the multiple slots is between 0.44- 0.46 mm.41. The method of clause 40, wherein the height of each slot of the multiple slots is about 0.45 mm.42. The method of any of clauses 34-37 and 39-41, wherein a pitch of the multiple slots in a direction perpendicular to the width is between 0.68-0.75 mm.43. The method of clause 42, wherein the pitch is between 0.70-0.72 mm.44. The method of clause 43, wherein the pitch is about 0.71 mm.45. The method of any of clauses 34-37 and 39-41, wherein activating the attenuator includes energizing an actuator to move the attenuator into the path of the photon beam.46. The method of any of clauses 34-37 and 39-41, wherein the attenuator includes a plate with the multiple slots defined thereon, and wherein moving the attenuator into the path of the photon beam includes reflecting photons of the photon beam that impinges on a surface of the plate.47. The method of clause 46, wherein the surface of the plate has a roughness less than or equal to about 10 microns.48. The method of clause 46, wherein the plate includes aluminum.49. The method of clause 46, wherein the plate includes copper coated with aluminum.

[0074] Block diagrams in the figures may illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer hardware or software products according to various exemplary embodiments of the present disclosure. In this regard, each block may represent one or multiple arithmetical or logical operation processing that may be implemented using hardware such as an electronic circuit. Blocks may also represent modules, segments, or portions of code that comprises one or more executable instructions for implementing the specified logical functions. It should be understood that in some alternative implementations, functions indicated in a block may occur out of the order noted in the figures. For example, two blocks shown in succession may be executed or implemented substantially concurrently, or two blocks may sometimes be executed in reverse order, depending upon the functionality involved. Some blocks may also be omitted. It should also be understood that each block of the block diagrams, and combination of the blocks, may be implemented by special purpose hardware -based systems that perform the specified functions or acts, or by combinations of special purpose hardware and computer instructions.

[0075] It should be appreciated that the embodiments of the present disclosure are not limited to the exact construction that has been described above and illustrated in the accompanying drawings, and that various modifications and changes may be made without departing from the scope thereof. The present disclosure has been described in connection with various embodiments, other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims.

Claims

CLAIMS1. A loss element for a laser beam, comprising: an attenuator including a plurality of openings configured to be movably positioned in a path of a photon beam, the plurality of openings including multiple slots arranged parallel to each other, wherein, when the attenuator is positioned in the path of the photon beam, a width of each slot of the multiple slots is greater than the width of the photon beam that impinges on the attenuator.

2. The loss element of claim 1, wherein the multiple slots comprises a set of 25-35 slots having substantially equal heights and widths.

3. The loss element of any one of claims 1-2, wherein each of the multiple slots extend substantially across a width of the attenuator.

4. The loss element of claim 1, wherein a height of each slot of the multiple slots in a direction perpendicular to the width is between 0.43-0.47 mm.

5. The loss element of claim 1, wherein a height of each slot of the multiple slots is between 0.44-0.46 mm.

6. The loss element of claim 5, wherein the height of each slot of the multiple slots is about 0.45 mm.

7. The loss element of any one of claims 1-2 and 4-6, wherein a pitch of the multiple slots in a direction perpendicular to the width is between 0.68-0.75 mm.

8. The loss element of claim 7, wherein the pitch is between 0.70-0.72 mm.

9. The loss element of claim 8, wherein the pitch is about 0.71 mm.

10. The loss element of any one of claims 1-2 and 4-6, further comprising a mount that enables removal and reinsertion of the attenuator from the path of the photon beam.

11. The loss element of any one of claims 1-2 and 4-6, further comprising an actuator coupled to the attenuator, wherein the actuator is configured to move the attenuator into the path of the photon beam and remove the attenuator from the path of the photon beam.

12. The loss element of any one of claims 1-2 and 4-6, wherein the attenuator includes a plate with the plurality of openings defined thereon, the plate being configured to reflect photons of the photon beam that impinges on a surface of the plate.

13. The loss element of claim 12, wherein the surface of the plate has a roughness less than or equal to about 30 microns.

14. The loss element of claim 13, wherein the surface of the plate has a roughness less than or equal to about 20 microns.

15. The loss element of claim 14 wherein the surface of the plate has a roughness less than or equal to about 10 microns.

16. The loss element of claim 12, wherein the plate includes aluminum.

17. The loss element of claim 12, wherein the plate includes copper coated with aluminum.

18. A non-transitory computer readable medium that stores a set of instructions that is executable by at least on processor of a computing device to cause the computing device to perform operations, the operations comprising: activating a laser source to output a laser beam having a first power; and activating an attenuator to reduce a power of the laser beam to a second power lower than the first power, the attenuator including multiple slots arranged parallel to one another, wherein activating the attenuator includes moving the attenuator into a path of a photon beam in the laser source such that a width of each slot of the multiple slots is greater than the width of the photon beam that impinges on the attenuator.

19. A method of varying a power of a laser beam output from a laser source, comprising: activating the laser source to output a laser beam having a first power; and activating an attenuator to reduce the power of the laser beam to a second power lower than the first power, the attenuator including multiple slots arranged parallel to one another, wherein activating the attenuator includes moving the attenuator into a path of a photon beam in the laser source such that a width of each slot of the multiple slots is greater than the width of the photon beam that impinges on the attenuator.

20. The method of claim 19 further comprising reactivating the attenuator to move the attenuator out of the path of the photon beam to increase the power of the laser beam to the first power.

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