JP2007525657A - Spectral analysis module of gas discharge MOPA laser - Google Patents

Abstract

Pulses of 4,000 to 8,000 pulses per second or more with very finely controlled wavelength and bandwidth on a per pulse basis and output power levels up to and beyond 30 mJ A technology for an ultra-high repetition rate gas discharge laser with a MOPA configuration is provided.
Equal to or more than 15 mJ per pulse with femtometer bandwidth accuracy and tens of femtometer bandwidth accuracy range for measuring bandwidth per pulse at a pulse repetition rate of 4000 Hz and higher. Disclosed is a wavelength meter and method for measuring bandwidth for a high repetition rate gas discharge laser with an output laser beam that includes a pulse output of a pulse of a larger sub-nanometer bandwidth tuning range, which includes focusing with a focal length The bandwidth is calculated from the lens, the optical interferometer that generates the interference fringe pattern, the optical detection means located at the focal length from the focusing lens, and the position of the interference fringe in the interference fringe pattern incident on the optical detection means. and wavelength assuming constant lambda _0, and _{D 0 = (D OD -D ID} ) / 2, and the focal distance f Wherein [Delta] [lambda] = according ^{_{λ 0 [D OD 2 -D ID}} 2] / [8f 2 -D 0 2], D ID and D _OD, i.e., a pair of first fringe boundaries within the interference pattern on the interference pattern axis And a bandwidth calculator for determining respective distances between and between the pair of second fringe boundaries.
[Selection] Figure 4

Description

The present invention has a very finely controlled wavelength and bandwidth on a pulse-by-pulse basis, and an output power level of up to and beyond 30 mJ of 4,000 to 8,000 pulses per second or more of laser light. The present invention relates to an ultrahigh repetition rate gas discharge laser having a MOPA configuration for generating pulses.
RELATED APPLICATIONS This application is a US patent application Ser. No. 10/676, entitled “Spectrum Analysis Module of Gas Discharge MOPA Laser”, filed Sep. 30, 2003, the disclosure of which is incorporated herein by reference. No. 175, US patent application Ser. No. 10 / 676,907, filed Sep. 30, 2003, entitled “Spectrum Analysis Module of Gas Discharged MOPA Laser”, and “MOPA Laser Wavemeter”, filed Sep. 30, 2003. No. 10 / 676,224 entitled "Optical Mount for" is claimed.

US Patent No. “Bandwidth Estimation Techniques for Narrow Band Lasers” granted to Das et al. On Nov. 13, 2001, based on Application No. 09 / 405,615 filed September 23, 1999. The inventor published on Oct. 24, 2002 under the publication No. 6,317,448 and publication No. 200220154668 was named Knolls et al. And named “ultra-narrow band two-chamber high repetition rate gas discharge laser system” in 2001. The inventor, published on June 26, 2003 under US Patent Application No. 10 / 012,002, publication number 20030108072, filed on November 30, is called "4 KHz gas discharge laser system" by Wittak et al. Application No. 10 / 026,676 filed on Dec. 21, 2001, publication number 2002/0154671 Inventor, published on October 24, 2009 2002 application Ser. No. 10 / 056,619, filed Jan. 23, 2002, entitled "line selection type F ₂ chamber laser system" Kunoruzu of the other, the publication number Inventor published on Dec. 19, 2002 in No. 2002019654 published application number 10 / 141,216 filed May 7, 2002 entitled "Laser lithography light source with beam delivery" by Crane et al. No. 2003012234, published on Jan. 16, 2003, is the inventor's application number 10 filed on Jun. 28, 2002, entitled "6-10 KHz or higher gas discharge laser system" by Watson et al. / 187,336, the inventor published on February 13, 2003 with the publication number 20030138019 Rirofu other September 13, 2002 of the "F _{2 2-chamber} F ₂ laser system with a line selection based on pressure" named application Ser. No. 10 / 243,102, filed, 2003 Publication No. 20030031216 Inventor published on Feb. 13 published application No. 10 / 210,761 filed Jul. 31, 2002 entitled “Control System for Two-chamber Gas Discharge Laser” by Fallon et al. And published. No. 200303099269 published on May 29, 2003 by the inventor of Elshof et al., Entitled “Timing Control for a Two-chamber Gas Discharge Laser System”, filed on Dec. 21, 2001. With the exception of these referenced patents such as / 036,727, the prior art for this application is based on existing gas discharge arrays. The and wavemeters and other measurement devices used with such lasers are not described. The patents and applications cited above are all assigned to the assignee of the present application, the disclosure of each of which is incorporated herein by reference.
Measuring instruments for repetition rates described in the above-cited applications and gas discharge lasers operating above those repetition rates, particularly such lasers configured in MOPA systems where higher power output is available There is a need for improvements.

US patent application Ser. No. 10 / 676,175 U.S. Patent Application No. 10 / 676,907 US patent application Ser. No. 10 / 676,224 US patent application Ser. No. 09 / 405,615 US Pat. No. 6,317,448 US Patent Publication No. 2002015154668 US Patent Application No. 10 / 012,002 US Patent Publication No. 20030018072 US Patent Application No. 10 / 026,676 US Patent Publication No. 2002/0154671 US patent application Ser. No. 10 / 056,619 US Patent Publication No. 20020191654 US patent application Ser. No. 10 / 141,216 US Patent Publication No. 20030012234 US patent application Ser. No. 10 / 187,336 US Patent Publication No. 20030138019 US patent application Ser. No. 10 / 243,102 US Patent Publication No. 2003031216 US patent application Ser. No. 10 / 210,761 US Patent Publication No. 20030309269 US Patent Application No. 10 / 036,727

Sub-nanometer equal to or greater than 15 mJ per pulse with femtometer bandwidth accuracy and tens of femtometer bandwidth accuracy range for measuring bandwidth per pulse at 4000 Hz and higher pulse repetition rates Disclosed is a wavelength meter and method for measuring bandwidth for a high repetition rate gas discharge laser having an output laser beam that includes a pulse output of a pulse of bandwidth tuning range, which includes a focusing lens having a focal length and interference The bandwidth is calculated from the position of the interference fringe in the interference fringe pattern incident on the optical detection means, the optical detection means arranged at the focal length from the focusing lens, and the interference fringe pattern incident on the optical detection means, and λ ₀ Is a wavelength assumed to be constant, D ₀ = (D _OD −D _ID ) / 2, and f is a focal length, the equation Δλ = λ _{In accordance with} [D _OD ² -D _ID ² ] / [8f ² -D ₀ ² ], D _ID and D _OD , that is, between the pair of first fringe boundaries in the interference pattern on the interference pattern axis and the pair of first And a bandwidth calculator that defines a respective distance between the two fringe boundaries. The optical detector can be a photodiode array. The wavemeter can have an optical interferometer with a slit function, and the slit function and focal length are selected to provide two innermost fringes of the optical interference annular pattern to the optical detector. The optical detector may include an array of pixels each having a height and width and an array having a full width, and the aperture at the light input to the optical interferometer is such that the output of the etalon is the height of each respective pixel. A portion of the light beam sufficient to illuminate the optical detector over the entire height and width can be selectively input to the optical interferometer. The optical interferometer can include an etalon with a slit function of 3 pm or smaller and a finesse of 25 or larger, and the focal length can be 1.5 meters. The second stage diffuser can be placed between the first stage diffuser and the etalon to supply narrow cone light to the etalon, and the opening between the second stage diffuser and the etalon is narrow. A thin strip of conical light can be fed to the etalon.

The present application provides a spectral analysis module (SAM) for a MOPA two-chamber laser that generates laser output pulses at frequencies exceeding 4000 Hz and pulse energies up to and beyond 30 mJ, and also controls the wavelength and bandwidth for each pulse. It relates to meeting the requirements for the measurement subsystem. Those skilled in the art will recognize the extreme requirements imposed on such MOPA laser subsystems and their functions, including many of the sub-modules required to meet the performance requirements of such MOPA lasers and their functionality. I will. The present invention is described for illustrative purposes only with respect to ArF MOPA lasers operating at a nominal wavelength of 193.350 nm, but can be applied in exactly the same way, for example, to KrF or F ₂ MOPA gas discharge laser systems.

The following acronyms used in this application shall have the following meanings.
Terminology / Acronym: Definition ABF: Ammonium Bifluoride ADC: Analog / Digital Converter Amp: Amp Amp Current AOI: Incident Angle ArF: Argon Fluoride AR: Antireflection (Coating that reduces Fresnel reflection from optical surface)
AWR: Absolute wavelength reference BARO: Barometric station for module alignment, calibration and testing Blur: Correction factor used to correct “bandwidth sawtooth” effect BW: Bandwidth CaF ₂ : Calcium fluoride DD: Diffraction Diffuser DFM: Design for manufacturing EWCM: Extended wavelength control module F ₂ : Fluorine FCP: Launch control processor FD: Focal length fm: Fentometer
FRU: field exchange unit FS: fused silica FSR: free spectral range FWHM: full width at half maximum. General metric for laser bandwidth.
GGD: Polished glass diffuser KrF: Krypton fluoride LAM: Line center analysis module LNM / LNP: Line narrowing module / line narrowing package MgF ₂ : Magnesium fluoride MOPA: Main oscillator power amplifier NIST: US standard Engineering Bureau PDA: Photodiode Array PDM: Photodetector Module pm: Picometer SAM: Spectrum Analysis Module WEB: Wavefront Engineering Box

  The measurement subsystem of a MOPA laser system that includes a SAM as described above can perform important functions such as, for example, measuring the wavelength, bandwidth, and pulse energy of the optical output from the MOPA. The overall MOPA system 20 can be seen in FIG. These performance characteristics possessed by the laser system 20 can often be important in controlling the lithographic process, for example, the end use for the laser light generated by such a laser light system 20. For example, the requirements for lithographic processing with pulse-by-pulse control, such as pulse wavelength, bandwidth, pulse energy, pulse-by-pulse burst, and more finely controlled changes are for any control system for such a laser system 20. As well as generating significant demands, the measurement part of the control system is also exposed to performance effectiveness and efficiency demands that were not seen in this field even just a year or two ago, and these demands are: It is growing further.

  The MOPA configuration as seen in FIG. 1 facilitates a much smaller bandwidth than the previous generation laser product of the assignee of the present assignee, for example the “Cymer 70XXX” series of KrF and ArF lasers. As a result, as an example, the currently required bandwidth exceeds the tracking capability of, for example, the 7000A wavemeter, and its architecture requires that this function be separated into separate modules, SAMs. . In the MOPA laser system 20 as seen in FIG. 1, the first laser chamber 22, which is the main oscillator (MO), is centered around the nominal wavelength 193.350 nm or near the equivalent wavelength through the output coupler 26. Utilizing a line narrowing package (LNP) 24 including, for example, diffractive optics, such as a diffraction grating (not shown), which produces an output after some resonance in the MO chamber of the seed laser beam 62 having an ultra-narrow bandwidth. Is very finely tuned. The MO output beam 62 is then transmitted through an MO wavefront engineering box (WEB) 40, as described in the above-mentioned application in the present patent application assigned to the assignee of the present applicant. The beam is then passed to the power amplifier WEB 42 and from here to the SAM 46 where, among other things, the majority of the MO beam is directed into the power amplifier (PA) portion 50 of the MOPA laser system 20. In the PA portion 50, the seed MO beam at or near the desired wavelength and bandwidth is amplified within the PA 50 by at least two passes through the gain medium that forms the PA 50 with the aid of the beam reflector BR54. The

The output beam 64 of the PA portion 50 of the system 20 then passes back through the SAM 46 and PA WEB 42 and into the pulse stretcher 60, where each of the output pulses of the beam 64 is, for example, T For example in an optical delay unit to improve the _IS . This affects, for example, the dose seen on the wafer during lithographic exposure of the photoresist on the wafer, and certain other characteristics of the performance of the stepper / scanner lithography tool in performing the exposure described above, for example. give.

  As seen in FIG. 2, the SAM 46 can be subdivided into an electronics portion 74 that includes, for example, an opto-mechanical portion 72 for performing the function of a bandwidth (BW) meter, and a logic assembly portion, for example. The basic optical aspects of the SAM are similar to, for example, the assignee's assignee's “70XX” product, ie a wavemeter used in the past in LAM, and partially form an embodiment of the present invention. With significant deformation. The optical layout of the bandwidth meter is, among other things, a shorter FSR etalon with a longer focal length imaging lens requiring, for example, beam homogenization in the first pass of the etalon optical circuit, as described in more detail below. With the use of. A photodetector module (PDM) 144, such as a wavemeter in “70xx LAM”, monitors pulse energy and provides a high speed photodiode signal for diagnostic and timing purposes.

  The SAM 46 is housed in a SAM housing 76 attached to the optical mounting floor (shown in FIG. 4) by a plurality of thumb screws 78. The view of the SAM housing 76 shown in FIG. 2 shows a primary beam splitter 80 that receives the beam 64 from the PA 50 on the side of the SAM housing 76 shown in FIG. 2, and the beam 64 passes through the primary beam splitter 80. Then, after partially passing through the primary beam splitter 80, it exits from the rear part of the SAM casing 76 as seen in FIG. 2, and returns to the WEB 42 of the PA as shown in FIG.

  As shown in FIGS. 3 a-3 c, the primary beam splitter 80 can include a beam splitter purge cell base 90 that forms a steering mirror mounting shelf 92 and a primary beam splitter mirror mounting platform 94 therein. For example, it can be machined from a solid part of aluminum. The platform 94 and the bottom of the cell base 90 can form a beam path opening 96 therein. The base 90 can also be formed with a sample beam exit opening 98 on one of its sidewalls. As can be seen from FIG. 3 b, the sample beam aperture 98 can be covered by the sample beam exit window 112, through which the sample beam 114 exits the primary beam splitter 80 and the remaining optical and electron of the SAM 46. Enter the element. The opposite end of the sample beam path 98 inside the base 90 can also be covered by a window 110, through which a portion of the beam 64 is reflected from the steering mirror 102 mounted on the steering mirror shelf 92, and the sample beam path Enter 98.

  FIG. 3 b also illustrates the primary beam splitter mirror 104 mounted on the primary beam splitter mirror mount 100. In operation, the beam 64 exiting the PA 50 will be incident on the primary beam splitter 80 from above along the vertical axis shown in FIG. 3b, which is also the propagation axis of the beam 64 from the PA 50, which is normally in a horizontal plane. Will be understood. The beam 64 is partially reflected by the primary beam splitter 104 and about 5% of the beam 64 is reflected and reaches the steering mirror 102 while the remaining portion passes through the mirror 104 of the primary beam splitter, FIG. As shown in FIG.

  About 5% of the beam reflected from the primary beam splitter mirror 104 is reflected from the steering mirror 102 at an incident angle of about 25 ° and exits the primary beam splitter 80 through the window 112 in the same manner as the sample beam 114, as described below. In the remainder of the SAM 46, as will be described in greater detail below. The beam 62 from the MO 22 may also enter the PA 50 in the opposite direction through the mirror 104 of the same primary beam splitter from the PA WEB 42 as part of the seed of the gain medium of the PA 50 by the MO beam 62, ie towards the PA 50. Will be understood.

FIG. 3c shows a primary beam splitter with a beam splitter cover 116 that includes a flange 118 for connection to a blower of the purge system of the PA 50, for example as described in more detail in the above-mentioned current patent-pending application. 80 is shown.
As shown in FIG. 4, which is a plan view of the SAM optics subsystem 72, the light picked up from the main beam 64 by the primary beam splitter mirror 104 and reflected from the steering mirror 102 is the primary beam as a sampled beam 114. The light is emitted from the splitter 80. The sampled beam 114 is distributed in the bandwidth meter 88 of the SAM 46 to provide two separate internal functions of the bandwidth meter 88 of the SAM 46. Fresnel reflection from A portion of the beam 114 incident on the secondary beam splitter mirror 140 is reflected onto a photodetector module (PDM) 144 as a beam 142 for pulse energy measurement and output to the electronics package 74 as a high speed photodiode signal. Is done. The bandwidth circuit, described in more detail below, receives a major portion of the beam 114 from the steering mirror through a mirror 140 that serves as a secondary beam splitter. Due to the thinness of the selected primary beam splitter mirror 104, the Fresnel reflections overlap, and the fluence on certain optics in the SAM is within an acceptable range, ie below the damage threshold for the material of the optics. Complicating the problem of keeping. This beam 114 is involved in the illumination of the etalon 162 that produces a fringe pattern that is monitored using the photodiode array PDA 182 as described in more detail below. According to an embodiment of the present invention, from the fringe pattern, the FWHM bandwidth is a simplified mathematical that increases the processing speed of the output of the PDA 182 in order to further consider the per-pulse calculation of 4000 Hz and higher. The calculation can be performed with an accuracy finer than 0.01 pm.
The SAM 46 can measure the bandwidth by the output of the PDA 182 and the pulse energy at the output of the PDM 144. The SAM 46 and LAM 28 can be interfaced (not shown) with a laser control system, which in turn provides active control based on, among other things, feedback from these measurement modules.

  As shown in FIG. 4, the beam 114 exiting the secondary beam splitter 140 enters the adjustable M1 mirror 146 and is directed into the front cylindrical telescoping lens 204 housed in the lens mount 150, Next, as will be described in more detail in connection with FIG. 7, an optical instrument combination unit 152 that includes a rear telescoping lens 220, a first stage diffuser 222, and a focusing lens 224 in turn is reached. The beam 114 then passes through the second stage diffuser 160 after being reflected from the adjustable M2 mirror 156. The beam then passes through the etalon 162. The fringe pattern created by passing the beam through the etalon 162 is reflected from the adjustable M3 mirror 164 and reaches approximately the center of the elongated M4 fixed 45 ° training mirror 166, on the surface of the adjustable M5 normal incidence mirror 168. Reach. The fringe pattern is then reflected back from the right hand portion of the mirror 166, reflected from another adjustable M6 normal incidence mirror 180, back onto the left hand portion of the mirror 166, and finally incident on the PDA 182. With the exception of M1 (146), the mirror is adjustable in some ways, for example during installation, but field access for adjustment is not possible, while M1 (146) is field adjustable.

The function of the SAM 46 according to an embodiment of the present invention is to provide a high resolution measurement of, for example, the bandwidth of the laser output beam 64 at the PA 50, such as the FWHM bandwidth. As a result of the positioning of the SAM 46 to the output of the PA 50, the energy density level visible from the optical elements in the SAM 46 is the corresponding element, for example in the LAM 28 and / or in conventional lasers such as the assignee's assignee's “70XX” product Can be very significantly higher. This can significantly increase the lifetime risk for the primary beam splitter 80 and some other optical components, for example in the SAM 46. For example, to mitigate damage promoted by fluence to the primary beam splitter 80, the SAM module 46 allows the primary splitter 104 to perform, for example, 70 on the beam 62 from the MO 22 and the beam 64 from the PA 50 according to embodiments of the present invention. Designed in a state that is directed to the degree. This has been selected to thereby reduce the fluence level (per cm ² ) by a factor of 2 compared to a beam splitter oriented at 45 degrees, for example. Further, for example, in the beam homogenization method in the SAM 46 according to the embodiment of the present invention, calcium fluoride is selected as the selected optical material for the selected optical apparatus.

  The operating parameters required for a SAM according to an embodiment of the present invention are a wavelength operating range between 193.2 nm and 193.5 nm such that the SAM module 46 functions from either end of the wavelength range, and the module 46 is pulse-by-pulse. Including a laser pulse repetition rate of 1 Hz to 4000 Hz with a bandwidth measurable on a per-fire basis, and a pulse energy of 10 mJ to 30 mJ exiting the PA 50, and the module includes that range of pulse energy Provides bandwidth measurements across. Furthermore, the bandwidth (Δλ) resolution requires 0.001 pm accuracy required for bandwidth calculation, and a bandwidth (Δλ) accuracy of 0.04 pm is the spectrometer (LTB) used to calibrate the SAM module. Etc.), the bandwidth measurement range is required to be 0.1 pm ≦ Δλ ≦ 0.3 pm, and the FWHM measurement is performed by the SAM module 46 with 0.1 pm ≦ Δλ ≦ 0. Requires that bandwidth can be tracked over 3 pm, the accuracy of the blur correction is the BW difference between the innermost and outermost fringe positions (comparison of the two averages: 0. 0 on either side of the jump range of the fringe). 3 points BW reading within 0.03 pm within 03 pm) is required to be ≦ 0.02 pm, and “fringe position” vs. “bandwidth accuracy” is ≦ ± from the reference (LTB etc.) spectrometer. 0.0 Required to be pm delta, as well as the ability to scan through the entire FSR (3pm) in 0.02pm increments starting at the center wavelength to compare the BW against the deconvolved spectrometer values Is done.

  For power and pulse energy measurements for a specific pulse energy range of 10 mJ to 20 mJ (nominal 15 mJ), the system is required to meet all optical specifications and the energy monitor 144 calibration accuracy is 0.05 watt resolution. Is required to be <± 3% based on a NIST traceable commercial wattmeter with a nominal 15 mJ, in continuous operation at 1000 Hz, and the energy monitor calibration drift is commercially available over the nominal launch of the laser gas test. It must be <± 2% peak-to-peak variation over 100 million pulses when measuring at a resolution of 0.05 watts with a wattmeter, and power linearity at 1000 Hz continuous is measured when using a water-cooled wattmeter head. 10mJ is 10 watts, 15mJ is 15 watts, and 20mJ is 20 watts Must be within 1 watt. The implicit linearity specification for constant energy and variable repetition rate need not be applied.

  The etalon starting raw video level (both left and right peaks) operates at 15 mJ at the output of PA 50 according to an embodiment of the present invention, with a maximum value of 1.0 volts and a minimum value when measured in a laser frame that meets the BW specification. Is required to be 0.6 volts. The voltage level is defined as the raw peak value minus the floor value. The fringe symmetry is required to be 115 ≦ fringe symmetry ≦ 85, and fringe symmetry = 100 × (left peak / right peak). The raw video level (both left and right peaks) of the end-of-life etalon 162 operates at 15 mJ at the output of the PA 50 according to embodiments of the present invention, and when measured in a laser frame that meets the BW specification, A) the maximum value is 2.5 volts, B) The requirement that the minimum value be 0.3 volts must be met. The signal level at 15 mJ pulse energy of the energy monitor 144 must be 15K ADC maximum and 5K ADC minimum.

  According to embodiments of the present invention, certain reliability specifications are required to be met, which are, for example, a target mean failure interval of ≧ 12B pulses, a field replacement of the SAM logic assembly is 15 minutes, for example ≦ 2 Target average exchange time of time, 60 minutes of field replacement of damaged primary splitter including recalibration of energy monitor, 10 minutes of inspection of etalon fringe pattern to correct possible low image or fringe asymmetry, and> Includes 95% device-dependent uptime.

  Maintenance requirements involve, for example, replacement of logic assembly 74 that requires access to unit 74 while in the laser frame, and access to main splitter 80 by a removable fastening assembly (not shown) connected to flange 118. Includes replacement of primary beam splitter 80. Maintenance is performed by removing the module from the laser frame and accessing the 5/64 inch hexagon head adjustment screw 170 (shown in FIG. 7) through the holes in the cover of two separate modules during laser operation. Requires fringe symmetry and height adjustment. When this maintenance is done in the field, a gas panel is required.

Further, according to an embodiment of the present invention, the design can be completed for the SAM module 46, for example, replacement of the module 46 and the energy calibration of the energy measurement by the PDM 144, for example in a frequency of 12 billion pulses, for example within 2 hours. , PDM 144 also requires that it be calibrated once a year over 2 hours.
The design of the SAM 46 is required to allow quick access to facilitate quick removal of the module 46 from the system 20. This includes the elimination of improper mounting and installation in the superstructure. In order to facilitate handling and prevent damage to the device or injury to the operator, a guide, trajectory or stop device may be provided.

According to embodiments of the present invention, the SAM 46 will be required to measure bandwidth, for example, every pulse that reaches an accuracy of at least 10 femtometers, for example, exceeding 4000 Hz and reaching 8000 Hz. For example, with PDA 182 having a pixel size of horizontal 0.025 mm × vertical 0.5 mm in PDA 182 and an array of 1024 photodiodes (pixels), the focal length of the imaging lens shown in FIG. 7 and the 3 pm free spectrum of etalon 162 Using the range (FSR), we can use the basic interferometer equation to handle the etalon fringe intensity distribution, ie λ = (2 ^* n ^* d / m) ^* Cos (θ), where , Λ is the wavelength, nominally 193.350 nm, n is the internal refractive index of the etalon, d is the mirror distance of the etalon, m is the order and the integer value of the wavelength at the fringe peak, and θ is within the etalon The incident angle of the optical path with respect to the interferometer axis. The above equation can be rewritten as λ = (2 ^* n ^* d / m) ^* Cos (R / f), where R is a fringe radius, for example 250-450 PDA pixels, The pixel is about 25 pm and f is the focal length from the lens to the PDA entrance plane, for example 61280 pixels wide, ie at the focal length of the focusing lens 224 which is a lens with a nominal focal length of 1.5 m. 1.532 m / 25 μm.

In order to deal with the mechanical drift in beam pointing following the introduction of interference in the etalon 162, it is preferable to handle the diameter D rather than the radius of the fringe. Accordingly, λ = (2 ^* n ^* d / m) Cos (D / 2f). Since the fringe width is a measure of the bandwidth of the light source passing through the etalon 162, assuming that the center wavelength is known, the difference in wavelength calculated for the inner and outer diameters is the raw Will give a bandwidth value. Assuming that two peaks in the same ring are only visible from PDA 182 as two separate peaks along the axis of the ring, λ _ID (inner diameter) = (2 ^* n ^* d / m) ^* Cos (D _ID / 2f), and λ _OD (outer diameter) = (2 ^* n ^* d / m) ^* Cos (D _OD / 2f). Since Δλ = λ _ID −λ _OD , Δλ = λ ₀ [Cos (D _ID / 2f) −Cos (D _OD / 2f)] / Cos (D ₀ / 2f), where D ₀ = ( D _ID + D _OD ) / 2, λ ₀ is the bandwidth at the line center with respect to D ₀ according to λ = (2 ^* n ^* d / m) ^* Cos (D ₀ / 2f). In embodiments of the present invention, in these equations, as long as the actual λ ₀ is within 0.5 nm of the assumed value (assuming), the registered value at λ ₀ is sufficient, so that the input from the LAM 28 or λ Neither use of a portion of the pixels in the PDA 182 for _zero path measurement is necessary. However, a predetermined bandwidth can also be used as a calibration value.

Thus, in order not to lose significant processor time, the above equation results in the equation Δλ = λ ₀ [D _OD ² −D _ID ² ] / [8f ² −D ₀ ² ] using a small angle approximation. . Using this equation over the detector range instead of the prior art approach, the resulting error can be ignored, i.e. <10 ^-5 fm. The minor angle error is essentially zero over about 200-800 pixels and increases approximately linearly from these points to about 0.0005 fm to the edge of the detector.

By treating λ ₀ as, for example, a constant value of 193.350 nm, in the bandwidth calculation for a range of about 193.200 to 193.500, that is, about 0.3 nm, the error in bandwidth is a range smaller than 0.1 fm. Will stay. D _OD is equal to, for example, 325 pixels, D _ID is equal to, for example, 300 pixels, and D ₀ is equal to 312.5 pixels, which is f = 61280 pixels wide as described above.

Using error propagation, typically used for error analysis, assuming that independent variables and covariates are omitted, and ignoring the error contribution from various gains / quantum efficiencies / responses between PDA 182 pixels, the laser error σ λ0 / λ ₀ that results from assuming a lambda ₀ constant over the tunable range will <8 × 10 ^-4. For a comparable or lower contribution to bandwidth error from the focal length, σ _f will need to be smaller than 24 pixels (ie, about 0.5 mm). Similarly, for a similar or lower contribution to the error in bandwidth from fringe diameter measurements, σ _D would need to be better than 1/73 of a pixel. This demonstrates Applicant's choice of contribution based on focal length error and fringe diameter measurements to optimize bandwidth calculations, ie by assuming that λ ₀ is a known constant. .

According to an embodiment of the present invention, the fluence level in the first stage diffuser 222 is reduced, for example, along the long axis of the beam 114 passing through the first stage diffuser 222, as opposed to using a spherical lens. It is further confined by using a collimating cylindrical lens telescope. The resulting reduction in energy density dramatically reduces the possibility of damage to all optics in the SAM 46, except perhaps for the primary beam splitter mirror 104, but the primary beam splitter mirror. At 104, for example, when the output from the PA chamber 50 is operating at 40 mJ, the fluence level may reach approximately 25 mJ / cm ² . The energy density level at the mirror 104 of the primary splitter is closely tied to several system parameters and the ability to mitigate problems with pure SAM module 46 design is limited.

  To allow bandwidth measurements down to 0.2 pm and below, bandwidth tracking of currently used wavemeters such as the assignee's assignee's “7000A” laser product The ability is inappropriate. The 20 pm FSR etalon slit function used in standard wavemeters makes it difficult to track bandwidth changes in a reasonably stable manner. The inability to produce “better” 20 pm etalon with finesse improvements severely limits the ability to achieve the required bandwidth measurements with existing configurations. As a result, Applicants improved to an etalon 162 with a shorter FSR (to narrow the etalon slit function) and used a longer focal length imaging lens (the linearity of the etalon spectrometer 162 circuit including the PDA 1182). To improve dispersion). A relatively very narrow slit function etalon 162, for example a combined 3 pm FSR etalon, is selected with, for example, a 1.5 m imaging lens, which together has a FWHM range of, for example, 0.15-0.3 pm It was determined to provide a desirable bandwidth tracking capability over a wide range.

  The improvement in the slit function and linear dispersion of the etalon 162 provides a significant improvement in the ability to track bandwidth without having to resort to so-called “slope correction” measures. Nevertheless, there is a need to perform “blur correction” because the apparent bandwidth difference between the measurements from the inner and outer fringes can be as large as 0.025 pm, for example. . This can be as large as almost all error accumulations for the bandwidth measurement accuracy required for the SAM module according to embodiments of the present invention, so that, for example, “blur correction” is bandwidth calculation. Incorporated into.

  In accordance with an embodiment of the present invention, the energy monitor 144 in the SAM 46 is polarization sensitive because the uncoated beam splitter mirrors 104 and 140 that supply a small fraction of the main beam 64 to the energy monitor 144 may have polarization sensitivity. May have. Using the Fresnel equation, the polarization sensitivity of the energy monitor 144 to the input beam was determined to be 2.85: 1 :: horizontal: vertical.

  A high speed photodiode array 182 can be added to the SAM, in which case, for example, an automatic adjustment circuit is provided to other users using lithography or light sources, for example to trigger extinction in a synchronizable output circuit etc. that can be equipped Will be able to. This is believed to eliminate the need for certain measurements, such as with diode equipment, to measure pulse length (DIMPLE), and adjustment when any of several modules are replaced.

  The bandwidth number from the LAM 28 could be used in combination with the value reported by the SAM 46, eg, to accurately determine “in specification” and “out of specification” conditions. For example, the different relative sensitivities of LAM 28 and SAM 46 to the FWHM and E95 of the laser spectrum visible from each is a linear combination of two recorded values, eg, to accurately determine the FWHM or E95 of the spectrum over a range of different spectral shapes. Can be used.

  The selected etalon 162 can be constituted by, for example, a pair of air separating mirrors 174 (shown in FIG. 7) at a predetermined interval. The specifications of the etalon 162 are narrowed down by requirements for proper functioning of the etalon 162, for example, under the operating parameters described above, including requirements for extending the lifetime of this component. The selected parameters are, for example, a free spectral range of eg 3 pm at 193.36 nm, eg ≧ 25 effective finesse over an aperture of 10 mm, and a peak transmission (fringe peak optoelectric signal of ≧ 50% at 193.35 nm normal incidence. And the ratio of the input peak signal).

  Referring now to FIG. 7, the optical elements of the optical module 72 of the SAM 46 between the adjustable mirror M1 (146) and the etalon 162 are shown in more detail. In this embodiment, the telescope front lens 150 of FIG. 4 and the combination optical element 152 of FIG. 4 are all shown to be housed in a single mounting frame 200 and the telescope front lens 204 is shown. Is housed in a mount 150 attached to the mounting frame 200 by mounting screws 206, which also hold a finger spring clip holding the lens 204 in place in the mounting frame 150 in place. It plays a role. Within the mounting frame 200 are housed components of the combined optical instrument 152 shown in FIG. 4, ie, the telescope rear lens 220, first stage diffuser 222, and spherical lens 224. Telescope rear lens 220 can be held in place on mounting frame 200 by mounting screw 246 and circular spring clip 242. The spherical focusing lens 224 can be held in place by a pair of mounting screws 240 and an accompanying finger spring clip 248. Second stage diffuser 230 is held in place on mounting frame 160 of the second stage diffuser by mounting screw 236 and finger spring clip 238. The mounting frame 200 can be attached to the plate 122 of the optical instrument module 72 by the mounting screw 210, and the mounting frame 160 of the second stage diffuser can be attached to the plate 122 by the mounting screw 232. The etalon 162 can be attached to the plate 122 by mounting screws 170.

The front telescope lens can be a CaF ₂ convex cylindrical lens, which works in conjunction with a rear telescope lens 220 that can also be made of CaF ₂ and can also be a concave cylindrical lens. Can reduce the beam 114, ie, reduce its cross-section. The diffractive diffuser 222 can be made from CaF ₂ as well. The spherical focusing lens 224 can also be made from CaF ₂ and can have a focal length of 1.5 meters, for example. The etalon 162 can be, for example, a Fabry-Perot etalon with a free spectral range of about 3 pm at 193.350 nm and a finesse greater than 23. The etalon parameters and focal length are selected to provide the PDA 182 with essentially only the fringes from the two innermost interference rings, which essentially covers all of the photodiodes (pixels) in the array, There is some tolerance, for example ± 5 pixels, and the width of D _OD relative to the outermost of the two fringes will certainly change when the bandwidth and / or center wavelength changes.

A diffractive diffuser 222, which can be made from ArF laser grade fused silica, serves to homogenize the beam, resulting in a uniform redistribution of the input light beam. This ensures, for example, proper mixing of the spatial information in the beam so that the edge and center light will have uniform wavelength resolution and brightness. The approximate specifications of such a binary diffraction diffuser 222 include, for example, a 10 mm × 10 mm × 2 mm diffraction diffuser 222 size, a rectangular output pattern shape, ≦ 1% zero-order bleed through, and a horizontal of 10 ° ± 0. Includes full angle divergence of 1 °, vertical 5 ° ± 0.1 °. The selected material is believed to also be a excimer laser grade CaF _2.

The logic assembly 74 (SAM 46 electronics) is located near the SAM 46 optics module 72 because of the close interaction of the two modules 72 and 74. The PDM 144 according to the embodiment of the present invention can be installed in the optical device module 72 of the SAM 46. The SAM 46 and PDM 144 contain optical and electronic equipment to perform these roles, and the logic assembly 74 contains only electronic equipment to perform those roles.
The SAM 46 can be mounted perpendicular to an optical table (not shown). To simplify module replacement, the module 46 can be attached to the septum 122 within the module using three captive thumbscrews 78. At the interface, a non-elastomeric sealing can be provided.

  A link to a laser control system (not shown) can be provided, for example, through a local network or an Ethernet port on the SAM 46. This connection may be for non-time critical commands and information, for example. It can also have a direct connection from the SAM 46 to the firing control processor (FCP), which can provide a high-speed data stream of measurements for use in the control algorithm for controlling the laser system 20. .

  In order to avoid damage due to contamination and loss from absorption by oxygen, the path of the laser beam in module 46 can be purged. For example, a nitrogen purge gas flows from the WEB 42 of the PA through the interior of the primary beam splitter 80 and a purge outlet line in the chamber window (not shown) of the PA 50, that is, a blower (not shown) connected to the flange 118 of the primary beam splitter. For example, a purge interface for the primary beam splitter 80 can be provided to be evacuated through.

The remaining optical equipment within the SAM 46 (but outside the purge beam of the primary beam splitter 80) is exposed to a gas bath in dry nitrogen that can be supplied to the module 46 by, for example, a pipe joint through the housing 76. be able to. The housing 76 can have a nitrogen purge rate for a housing of, for example, 4 liters / minute, and an oxygen concentration not exceeding 5 ppm, and the leakage rate in the primary beam splitter purge cell under an overpressure of 100 kPa is, for example, 1 × 10 ^-5 scc / s.
Due to the possibility of so-called “white fuzz” damage (due to compression under high UV fluence) to the mirror 104 of the CaF ₂ primary beam splitter 80, the applicant has made use of the 70 ° angle beam incidence described above. It came. Accordingly, the internal optical layout of the SAM 46 has been modified from the prior art wavemeter version.

In the configuration of the SAM 46 prototype, the fluence level in the mirror 104 of the primary beam splitter 80 is such that the pulse energy is 20 to 40 mJ, the beam size is 9 mm × 3 mm, and the mirror 104 of the primary beam splitter 80 is 45 with respect to the beam propagation direction. It was estimated to be 52-105 mJ / cm ² assuming it was oriented at °. This corresponds to 13 mJ / cm ² found in the assignee's assignee's “70XX” product assuming a beam of 12.5 mm × 2.2 mm at 5 mJ / pulse.
The reorientation of the primary beam splitter mirror 104 from 45 ° to 70 ° results in a fluence reduction of approximately 25-51 mJ / cm ^{2 in} the primary splitter mirror 104. However, “white fuzz” damage still remains and this still needs to be addressed in the design. It is believed that the redesigned mount can accommodate CaF ₂ or MgF ₂ materials.

For example, as can be seen in FIG. 5, when the coordinate system for the laser system 20 is defined using the right-handed coordinate system, the z-axis is, for example, the laser beam propagation direction, the x-axis is vertically upward, and the y-axis is It can be set in a horizontal direction toward the user, that is, a direction of jumping out from the drawing sheet. In such a coordinate system, the mirror of the primary splitter 80 is, for example, 2 mm thick and is a circular 40 mm plane oriented at an angle θ = 70 ° with respect to the x axis and an angle φ = 0 ° with respect to the z axis. it can. This results in a total beam center displacement by distance d after passing through the mirror 104 of the primary splitter. For example, for a CaF ₂ material (n=1.518@193 nm), the beam displacement amount related to the coordinate system defined above is as follows.
Δx = + 0.0mm
Δy = + 1.33mm
Here, it is assumed that the refractive index of N ₂ at 1 atm = 1.0003.

For MgF ₂ material, the refractive index along the propagation direction should be determined first. Assume that the refractive index for ordinary light is n _o = 1.4305, the refractive index for extraordinary light is n _e = 1.444, and the optical device is cut by the plane surface of the optical device that intersects the c-axis perpendicularly. The refractive index in the medium in the propagation direction along the z axis is reduced to n = 1.4362. As a result, the beam displacement amount is as follows.
Δx = + 0.0mm
Δy = + 1.29mm
This is not much different from the displacement in CaF ₂ .

The beam separation between the centers of the two Fresnel reflections of the mirror 104 of the primary splitter is considered as follows.
d = 2 ^* t ^* (tan θ _i ) ^* (cos θ _r )
Using the material properties listed above for θ _i = 70 °:
⇒For CaF ₂ , d = l. lmm
⇒d = 1.2mm for MgF ₂

For light that is completely polarized along the y-axis, the reflectivity of the splitter is:
I ₁₁ = I _0y [{P ₇₀ Cos ² (0)} + {S ₇₀ Sin ² (0)}] = I _0y P ₇₀
Here, P ₇₀ is the reflectivity of p-polarized light at an incident angle of 70 °, I ₁₁ is the intensity of light reflected from the front surface of the mirror 104 of the primary splitter, and I _0y is horizontal Is the intensity of the incident light polarized in the direction.
I ₁₂ = (I _0y −I ₁₁ ) P ₇₀ − (I _0y −I ₁₁ ) (P ₇₀ ) ²
Here, I ₁₂ is the intensity of light emitted from the front surface of the primary splitter mirror 104 after reflection from the rear surface of the primary splitter mirror 104. The total intensity reflected in the measurement module 46 of the beam 114 is as follows:
I _R = I ₁₁ + I ₁₂
Against ⇒CaF _2, = 0.08133I _0y
Against ⇒MgF _2, = 0.08632l _0y

Secondary splitter 140 then reflects a portion of this light in beam 114 to energy monitor 144. The direction is the direction in which the reflected light is as follows.
I ₂₁ = S ₄₅ (I ₁₁ + I ₁₂ )
I ₂₂ = S ₄₅ (I ₁₁ + I ₁₂ −I ₂₁ ) − (S ₄₅ ) ² (I ₁₁ + I ₁₂ −I ₂₁ )
Here, I ₂₁ and I ₂₂ are the intensities of light reflected on the energy monitor 144 from the front and rear surfaces of the mirror 140 of the secondary splitter. The proportion of the intensity of incident light reflected into the energy monitor 144 for horizontally polarized light is as follows:
I _R = I ₂₁ + I ₂₂
Against ⇒CaF _2, = 0.0137I _0y
Against ⇒MgF _2, = 0.01454l _0y
The ratio of the intensity of incident light reflected into the energy monitor 144 for vertically polarized light is as follows:
⇒ = 0.756I _0x for CaF ₂
Against ⇒MgF _2, = 0.00702I _0y

  This analysis assumes that there is no loss between the primary splitter mirror 104 and the secondary splitter 140 (there is no window or additional secondary splitter between the two), but in the embodiment disclosed above, Between the primary beam splitter mirror 104 and the secondary beam splitter 140 are two windows 110 and 112, and a steering mirror 102, assuming light polarized perpendicular to the horizontal axis of the beam and known in the prior art. Thus, the intensity calculated with these decreases by about 10%.

An incident angle of 70 degrees dramatically increases the size of the beam footprint on the surface of the splitter mirror 104. As shown in FIGS. 3 and 8, due to the requirement that the mirror 104 of the primary splitter in the SAM 46 should accommodate double passes (one path of the MO beam 62 and the other path of the PA beam 64), The situation is getting more complicated. The beam size, separation, and angle defined by the ray traces of the system are as follows, as shown in FIG.
MO beam:
Horizontal profile: 2.0 mm, vertical profile: 7.5 mm
PA beam:
Horizontal profile: 5.0mm, Vertical profile: 11.0mm
Distance between centers: 3.72 mm
Tilt between MO and PA beams: 6.7 mrad

  FIG. 8 shows the beam footprint on the chamber surface 104 ′ of the primary splitter mirror 104 and the shutter surface 104 ″ of the primary splitter mirror 104. Hatched area 105 is an approximate “lock out” area used to mount optical instrument 104. The 32 mm diameter circle serves to allocate some margin for the available space for the two beams. At the chamber surface 104 ′ of the primary splitter mirror 104, the MO beam 62 and PA beam 64 are positioned so that the midpoint of the line 105 across the two beams 62 and 64 coincides with the face center of the optical instrument 104 ′.

  For example, on the shutter surface 104 ″ facing the output shutter in the WEB 42 of PA, a beam movement of 1.3 mm, for example, is observed. However, this movement is sufficiently corrected by the 1.88 mm surface movement due to 70-degree projection of the 2 mm thick splitter mirror 104. As a result, the midpoint of the line extending between the two beams is 0.58 mm from the center of the shutter surface 104 ″ of the optical device 104. Under such strict space constraints, there is almost no range that allows alignment errors.

A schematic diagram of a typical optical layout is shown in FIG. FIG. 5 schematically shows the direction of the mirror 104 of the primary splitter. The reflected light 66 and 66 ′ is guided by the steering mirror 102 into the optical plane of the wavemeter. The incident angle of the steering mirror 102 is 25 ° with respect to the incident angle of 70 degrees by the mirror 104 of the primary splitter of CaF ₂ . For a beam 64 having a nominal pulse energy of 30 mJ in a 9 mm × 3 mm beam, assuming a top hat profile across the beam path, ie, approximately equal intensity distribution across all beam paths, the maximum fluence at the mirror 104 of the primary splitter Is where the incident beam 66 at the chamber-side primary surface 104 ′ and the beam 66 ′ reflected from the shutter-side secondary surface 104 ″ overlap (see FIG. 5 for schematic and illustrative purposes, The beam overlap is not shown.) This maximum fluence can be estimated as follows.
Incident beam fluence = Cos (70) ^* 30.0 / (0.9 ^* 0.3) = 38 mJ / cm ²
Reflected beam fluence = Cos (70) ^* (0.0389) ^* 30.0 / (0.9 ^* 0.3) = 1.48 mJ / cm ²
⇒Total fluence = 39.5mJ / cm ²
For a range of 20-40 mJ / pulse, the fluence range at the mirror 104 of the primary splitter is 26.3-52.6 mJ / cm ² .

In the steering mirror 102, the maximum fluence level is as follows.
Fluence due to front reflection = Cos (25) ^* (0.0424) ^* 30.0 / (0.9 ^* 0.3) = 4.27 mJ / cm ²
Fluence due to back reflection = Cos (25) ^* (0.0389) ^* 30.0 / (0.9 ^* 0.3) = 3.92 mJ / cm ²
⇒Total fluence = 8.2mJ / cm ²
For a range of 20-40 mJ / pulse, the fluence range of the steering mirror (dielectric coating optical instrument) is 5.5-11.0 mJ / cm ² .

Returning to FIG. 4, the overall optical layout within the optical portion 72 of the SAM 46 is shown. As described above, light from the primary splitter mirror 104 is reflected into the optical plane of the wavemeter in the beam 114. The approximate fluence in the various optical elements leading up to the second stage diffuser 160 can be estimated by continuing the assumptions made above. The fluence ranges listed below are for energy of 20-40 mJ / pulse, as described above, assuming a reduction rate along the long axis of the beam 114 of 2.2 using a cylindrical telescope setting. Is.
M1 adjustable mirror 146: 4.1-8.3 mJ / cm ²
Telescope front lens 204: 5.8 to 11.7 mJ / cm ²
Telescope rear lens 220: 11.8 to 23.7 mJ / cm ²
Diffraction diffuser 222: 10.9 to 21.8 mJ / cm ²
Focusing lens 224: 7.6 to 15.3 mJ / cm ²
Second stage diffuser 230: 7-14 mJ / cm ²
As a result of the overlap of the two Fresnel reflections from the mirror 104 of the primary splitter, the fluence level in the telescope rear lens 220 and the diffractive diffuser 222 is believed to be quite high, with possible damage. To alleviate this, the applicant, for example, incorporate cylindrical telescope, and / or using a MgF _2.

  Referring now to FIG. 6, the output signal levels from the PDA 182 in the SAM 46 for different fluence levels (20 mJ / pulse, 30 mJ / pulse, and 40 mJ / pulse) and their intersection with the 1.5V signal output line are shown. Has been. At 1.5V output for each of the above fluence levels, the incident angles are 65.9 °, 70.8 °, and 73.2 °, respectively. This assumes a cone angle diffuser 230 of about 10 degrees, for example.

During lifetime testing of the experimental module of the SAM 46 wavelength meter portion, Applicants have accumulated approximately 1 billion firings in a design that is likely to exhibit a much lower fluence than in the embodiments described in this application. Later, traces of damage to the first stage diffractive diffuser 222 were discovered. The first stage diffractive diffuser 222 in the SAM 46 faces significant damage risk from high fluence levels, for example because the risk of damage is very significant at fluence levels greater than 1 mJ / cm ² due to compression, for example. Silica optics are probably not usable. Different possible solutions expose themselves to possible damage to the diffractive diffuser 222. Making a diffractive diffuser from CaF ₂ instead of fused silica is one option. Another option is to increase the incident size of the beam 114 on the diffractive diffuser 222, thereby reducing the fluence in cm ² , for example, by combining a front telescope lens 204 and a telescope rear lens 220. It would be to reduce the magnification rate. Furthermore, combinations of these two or even other possible fused silica material choices can be utilized with beam reduction. Applicants believe that other life limits due to damage to fused silica optical elements may also be improved in this effort. For example, the front telescope lens 220 can be made large enough to have an acceptable fluence, even if it is a fused silica material. Similar fluence level incidence on a polished glass diffuser such as the second stage diffuser 230 is ignored because compressive damage to the element is not expected to dramatically change or affect the diffusion properties can do. The second stage diffuser 230 can be formed with a flat portion of glass having a polished surface to induce diffusion, which in turn enhances diffusion uniformity, such as ammonium bifluoride (ABF). For example, etching can be performed by immersing the surface in a bath.

In one embodiment, Applicants note that the front telescope lens 204, rear telescope lens 220, first stage diffractive diffuser 222, and focusing lens 224 are all made from CaF ₂ and further reduced. Although selected, this embodiment could also include other variants of a front telescope lens and a focusing lens made of fused silica of ArF grade or better (from a compression standpoint). These choices are, for example, compression by firing up to 20 billion shots with a small fluence (1-3 mJ / cm ² ) incident on a fused silica lens used in non-imaging applications, for example to calcium fluoride material It is determined at least in part by the question of whether it is strong enough to justify the change.

  In order to reduce the fluence level in the diffractive diffuser 222, redesigning the illumination technique primarily by, for example, changing the telescope reduction ratio, for example, generates significant potential benefits. Further, since the applicant has selected a telescope with a cylindrical lens, the lens orientation is such that only the long axis of the beam 114 is reduced. As a result, the fluence can spread better across the rectangular shape with the long axis of the rectangular shape of the diffuser 222 coinciding with the long axis of the beam 114, so that the fluence in the diffractive diffuser 222 is from a similar spherical lens. Lower than the fluence associated with the telescope.

  In another possible embodiment, it may be necessary to remove all of the telescope systems 204 and 220. The disadvantage of having an extended light source incident on the diffractive diffuser 222 would be a steep incident angle of the beam 114 on the polished glass diffuser 230. The polished glass diffuser 230 that disrupts the angular information in the beam is not perfect. When the angle becomes steep, the ability to uniformly mix the angle information in the beam 114 is reduced. As a result, the etalon cannot sample the entire light source beam 114 uniformly, which causes errors in the measurement.

  The implementation of embodiments utilizing spherical lenses can alternatively be further optimized by expanding the beam along the minor axis using, for example, a prism. For example, a 3 × beam expansion can result in the incidence of a 9 mm × 9 mm beam on telescope systems 204 and 220, for example. For example, after passing through a 1.8 × reduction telescope, the beam can be reduced to, for example, 5 mm × 9 mm, and the fluence level is further reduced in the diffractive diffuser 222. However, such beam expansion may result in an undesirably increased separation between the two Fresnel images, causing overfilling of the diffractive diffuser 222. For example, the minor axis of the beam 114 at a 30 degree angle with respect to the horizon may result in the light in the beam 144 being guided along a distorted angle as the beam expands toward the incidence into the etalon 162. In order to return the beam 114 to the required height above the bottom plate 122, an additional mirror is simply required. However, this is possible, but is probably a more complex option.

  However, by using a cylindrical lens pair for each of the horizontal and vertical axes, the size of the beam 114 in the diffractive diffuser 222, for example, by expanding the beam along the minor axis and reducing the beam size along the major axis. It is particularly effective to optimize. Assuming a symmetric setting with a reduction factor of 1.87x along the major axis and an enlargement factor of 1.87x along the minor axis, the beam size should be, for example, a 4.8 mm x 5.6 mm beam. Can do. This makes it possible to produce an ideal system. However, the expansion along the minor axis can also increase the separation between the two Fresnel reflection images 66 and 66 'upon incidence on the aperture of the diffractive diffuser 222. This can be avoided, for example, by blocking one of the Fresnel images 66 and 66 '. However, if the center-to-center separation between the two Fresnel images 66 and 66 ′ exiting the primary splitter 80 is about 5.3 mm, the implementation of the aperture to block one of the Fresnel reflections 66 and 66 ′ is implemented. It can be difficult but not impossible. For example, the implementation of the design can be performed, for example, with three lenses, including a symmetrical setting with a spherical lens in the middle of two cylindrical lenses that are oriented perpendicularly to each other. This can result in enlargement along one axis and reduction along the other axis.

  Improvements related to other optical instruments in embodiments of the present invention that relate to beam uniformity efficiency and effectiveness include improvements in the low quantum efficiency of PDA 182 used for fringe detection. Improvements in detector efficiency may reduce the need to use relatively high fluences in the entire series of optics within the SAM 46 and also within the LAM 28, to preserve the fused silica optical components. It is particularly useful. However, if constrained to the same PDA 182, the optical improvements described above will be required.

To summarize the possibility of using a diffractive diffuser 222 made of calcium fluoride according to an embodiment of the present invention, the use of a spherical lens with a reduction ratio of 2.0, a cylindrical lens with a reduction ratio of 2.0 Use, removal of the telescope, or use of two cylindrical lenses and one spherical lens with a reduction factor of 1.87 along the major axis and an enlargement factor of 1.87 along the minor axis. Various combinations of materials and embodiments between CaF ₂ and SF can also be useful depending on the choice of a particular solution.

  Referring now to FIGS. 9a and 9b and FIGS. 10a and 10b, there are shown perspective and cross-sectional views of the adjustable mirror mount 260 and the front and rear of the mirror, eg, mirror M2 (156), and FIG. 10b is a cross section of the mirror mount 260 along the line 10b-10b in FIG. 10a (except that the mirror 264 has been removed in the embodiment in FIG. 10a). The mirror 156 has an adjustable mirror mounting frame 260 that extends laterally from the generally vertical mirror mounting portion 261 along the lower leg 272 and forms a base for the vertical portion 261. 270 can be included. As shown in more detail in FIG. 10b, the vertical portion 261 and its upper leg 270 are attached to the lower leg 272 by a thin, relatively narrow bend 300, and the vertical plane of the incident beam (not shown). Due to the alignment of the mirror 264 mounted on the inner mount 260, the upper leg 270 and the vertical mirror mounting portion 261 can bend with respect to the lower leg 272, ie, the horizontal axis of the bent portion 300 is It can be rotated as a center. In addition, the front surface 263 of the vertical portion 262 causes the surface 263 to deflect approximately 2 ° to 3 ° in order to have a constant spring force in the bend 300 to maintain a constant spring force during tilt adjustment. Machined into.

  The mirror optic 264 is mounted in a recess on the rear side of the vertical portion 261, indexed to the work surface, and fastened by a circular spring clip 310 as shown in more detail in FIG. The spring clip mounting screw 312 is held in place. The indexing can be performed, for example, using a plurality of spherical push balls 314, one of which is shown in FIG. 10b, which balances the holding force on the optical instrument and is within the optical instrument. 10b can be placed in a machined opening in the vertical portion of the mount in FIG. 10b, for example 261, or mounted mirror or other optical device, for example in FIG. 10c. The spring clip engagement balls shown are aligned to engage, for example, the mirror 264 in FIG. Such stress can cause, for example, birefringence in the optical instrument. The embodiment shown in FIG. 9 a uses a plurality of finger spring clips 320. Mount 260 can be mounted on a dowel pin (not shown) that extends into dowel pin opening 304 in bottom leg 272 and pivots to align mirror 264 within the horizontal plane of the incident beam (not shown). Can be rotated. The dwell pin opening 304 and the dwell pin (not shown) mounted on the plate 122 it receives are indexed to the required position in the optical plane of the optical instrument, eg mirror 264. That is, when a dwell pin (not shown) is inserted into the dwell pin opening 304, the mirror indexed to the mount 260 is there if it can be adjusted in its axis when it is also aligned in the indicated direction, for example. Placed exactly in the power plane. Thus, the dowel pin and its receiving opening 304 also play an important role in aligning the optical plane of the optical instrument, eg, the mirror 264, and for horizontal pivoting as needed.

  It extends into a circular slot (not shown) in the plate 122 of the SAM 46 through a rotation adjustment fixing screw opening 294 in the upper leg 270 and a similar opening 292 in the lower leg 272, and a cap screw (not shown). The rotation adjustment fixing screw 290 held at a fixed position in (No) fixes the horizontal alignment of the mount 260. A vertical (tilt) adjustment screw 278 that extends through a through opening 280 in the upper leg 270 and has a ball tip that engages the lower leg 272 can be used to set the tilt of the vertical portion 261. The position can then be fixed by a tilt adjustment fixing screw 266 that extends through a tilt adjustment fixing screw opening 268 in the upper leg 270 and into a through opening 274 in the lower leg.

  The embodiment of FIG. 10a shows a similar mount 260 with a circular spring clip 310, shown in more detail in FIG. 10c, with the mirror in the form of a circular mirror removed. The circular spring clip 310 can have an annulus portion 320 that includes a plurality of attachment screw extensions 322 in which attachment screw holes 324 are formed. The circular spring clip 310 is also attached to the annulus by a spring clip connection 332 and can be placed with a hemispherical spring clip engagement protrusion 340 that facilitates engagement of the optical element without damaging the optical element, for example. It has a plurality of spring clips 330 that extend through spring clip arms 334 to a possible end extension.

  The embodiment shown in FIG. 11 is similar to that in FIGS. 9 and 10 but with the upper and lower legs, and the secondary beam splitter mirror mount 350 without bends, i.e. fixed to the secondary beam splitter, for example. It is a non-adjustable mirror mount. What is shown in FIGS. 12 a to 12 b is a mounting frame for mounting the combination optical element shown in FIG. 7, for example, a mounting frame 152. FIG. 12 a shows a combined optical instrument mounting frame 360 that includes a telescope rear lens 220 that is held in place by a retaining clip 363 mounted on the combined optical mount 360 by a pair of mounting screws 364. FIG. 12 b shows the rear end of the mount 360 having a spherical focusing lens 224 held in place in the Pb recess of the mount 360 by a plurality of finger spring clips attached to the mount by a plurality of mounting screws 372. FIG. 12b shows the focusing lens 224 removed to show the first stage diffractive diffuser 222 held in place in the recess by a retaining clip attached to the mount 360 by a pair of retaining clip mounting screws 382. Shows the mount.

  FIGS. 13a and 13b show a slit assembly for mounting, for example, a second stage diffuser, ie, 160 shown in FIG. The slit assembly mounting frame 390 includes a slit assembly 392 that is adjustably disposed on the mounting frame 390 by a pair of slots 400, and each pair and side of an adjustment screw 404 in the front vertical portion 401 of the slit assembly 392. A side slot 402 may be included that extends vertically with a side adjustment screw 406 in the side portion of the slit assembly. The front side of the slit assembly 390 faces the etalon as shown in FIG. The slit assembly 390 also includes a slit 394 in the front vertical portion that is attached to the slit assembly 392 by a pair of mounting screws 396. FIG. 13 a shows the slit assembly 392 in a lowered position that acts as an opening for the diffuser 230 between the second stage diffuser 230 and the etalon 162. FIG. 13 b shows the slit assembly 392 in a retracted position for alignment between the diffuser 230 and the etalon 162. FIG. 13c shows a vertical positioning screw 412 passing through the vertical positioning flange 418 on the mount 390 with the slit assembly 392 in the lowered position and the second stage diffuser 230 held in place by a plurality of finger spring clips. Is shown. FIG. 13d shows the slit assembly 392 in the retracted position.

  The slit opening 394 can be adjusted from side to side by a horizontal adjustment screw 406 and the slot 414 at the top of the assembly 392 is adapted for side to side movement of the screw 412. Adjustment screws 406 and 412 have a very fine pitch of M4 × 0.50, allowing a very fine positioning of the slit assembly 392 to optically align the slits. These screws 406 and 412 can have hex nuts or similar tops, for example, to facilitate rotation with an adjustable wrench, as shown.

In operation, it will be appreciated that selected narrow widths of the primary beam splitter mirror 104 that result in overlapping Fresnel reflections have been addressed in embodiments of the present invention. The primary beam splitter mirror 104 is well protected from damage due to exceeding the fluence damage threshold, eg, for MgF _2, so that the beams 62 and 64 pass through the mirror 104 without overlapping the incident areas of the beams 62 and 64. MO22 (although Fresnel reflections in both the passed and reflected portions of the PA beam are likely to overlap), resulting in a minimum displacement of the path of the PA beam 64. The angle of incidence for both the output laser beam 62 and the output laser beam 64 of PA 50 was selected to be at least 70 °. At the same time, enough of the beam 64 to allow the PDM 144 and PDA 182 to function (providing an accurate output signal with sufficient signal-to-noise ratio, for example, that would be useful within the above specifications on a pulse-by-pulse basis). The quantity is reflected into the wavemeter portion of the SAM 46. Furthermore, the 70 ° AOI of embodiments of the present invention allows the secondary beam splitter to reduce its damage threshold, for example due to high UV fluence levels passing through the optics, even if there is exposure to overlapping Fresnel reflections in the beam 114. It is possible to avoid exceeding. There may also be a maximum angle of incidence depending on, for example, the overall size of the mirror, the footprint of each beam 62 and 64 at incidence on the mirror 104, and the desired tolerance. For example, if a material having a high threshold for damage at DUV wavelengths and smaller light becomes available and / or used in the wavemeter portion of the SAM 46, the material used for the mirror 104 will be different. A PDA with more pixels per current pitch and / or with a more sensitive / accurate detector forming each of the pixels will have an AOI in the primary beam splitter mirror 104 somewhat higher than 70 °. Although the result can be small, the AOI of the primary beam splitter remains significantly greater than in previous lasers, the overall output power requirement of the laser according to embodiments of the present invention, or the primary beam Any of the outputs 62 of the MO laser chamber 22 sharing the available surface of the splitter mirror 104 Do not be.

  The slit function of the etalon 162 along with the focal length of the focusing lens 224 was chosen to provide essentially only the innermost ring of the interference pattern generated by the etalon to the photodiode array of the PDA 182, and this innermost The ring can also be generated by other optical interferometers, eg, diffraction gratings that also have a slit function, so that the PDA can perform BW calculations over a range of BW measurements and laser wavelength tuning. It can be ensured that at least one of the two interference rings used to determine the fringe pixel location is included. Bandwidth calculations have been simplified to facilitate processing within the wavemeter microprocessor.

  The primary beam splitter 104 may vary somewhat based on the overwhelming majority of the output laser beam 64 from the PA 50, i.e. its exact amount, such as power requirements and fluence limits within the SAM. The first small portion 114 that passes approximately 95% and is the remainder of the beam 64 is reflected back to the SAM's wavemeter. The beam splitter 140 at the SAM 46 reflects the overwhelming majority of the first small portion 114 of the beam 64, eg, about 95%, to the PDM 144. This may also vary somewhat depending on the amount of light required by the PDM 144 and the fluence limit in the SAM, but the rest, which is about 5% of the first small portion of the beam 64, is the SAM 46 A second subsection is formed that passes through the remaining optical equipment in the wavemeter.

  The above-described embodiments of the present invention are intended for purposes of illustration and illustration only and are not the only embodiments in which the present invention may exist. Those skilled in the art will appreciate that many modifications and changes to the described embodiments can be made without changing the spirit and spirit of the invention. For example, embodiments of the present invention contemplate detectors that use an array of photodiodes. However, other photosensitive elements can be used, for example, photosensitive integrated circuits such as CMOS or CCD devices could be used, effectively illuminating each photodiode in the photodiode array. When the expression is used, it contemplates other such forms of effective illumination of the photosensitive element. Furthermore, what is currently considered is to illuminate the photodiodes of the embodiments of the present invention over their entire vertical range, ie 0.5 mm, but more efficient photodiodes or for example the SN ratio of these outputs. Improvement would be able to enable effective illumination (this is from light sensitive elements such as photodiodes that would allow measurement of the amplitude of light intensity at a particular light sensitive element. Meaning illumination that produces a satisfactory and accurate electrical output signal). The scope of the invention should, therefore, be considered only in light of the claims and their legal equivalents.

FIG. 2 shows a gas discharge laser with a MOPA configuration in which embodiments of the present invention can be used. It is a perspective view of a spectrum analysis module according to an embodiment of the present invention. FIG. 3 shows components of a primary beam splitter according to an embodiment of the present invention. FIG. 3 shows components of a primary beam splitter according to an embodiment of the present invention. FIG. 3 shows components of a primary beam splitter according to an embodiment of the present invention. It is a top view of the spectrum analysis module by embodiment of this invention. FIG. 3 is a schematic diagram of a portion of a spectral analysis module according to an embodiment of the present invention. 4 is a graph of the performance of a module element according to an embodiment of the present invention. FIG. 5 shows in more detail a plan view of the elements shown in FIG. 4 according to an embodiment of the invention. It is a figure which shows the fluence pattern on the front part of the beam splitting mirror by embodiment of this invention. FIG. 6 is a diagram showing a fluence pattern on a rear portion of a beam splitting mirror according to an embodiment of the present invention. 1 is a perspective view of an adjustable mirror mount according to an embodiment of the present invention. FIG. 1 is a perspective view of an adjustable mirror mount according to an embodiment of the present invention. FIG. FIG. 10 shows an additional embodiment with a circular mirror of the adjustable mirror mount shown in FIGS. 9a-9b. 9a or 9b shows an additional embodiment with a circular mirror of the adjustable mirror mount shown in FIGS. 9a to 9b and is a cross-sectional view of FIG. 9a or 10a along the cross-sectional line 10b-10b shown in FIG. 10a. FIG. 10b shows the mount of FIG. 10a with the additional embodiment mirror having the circular mirror of the adjustable mirror mount shown in FIGS. 9a-b removed. FIG. 6 shows another optical mount according to an embodiment of the present invention. FIG. 6 shows another optical mount according to an embodiment of the present invention. FIG. 6 shows another optical mount according to an embodiment of the present invention. FIG. 6 shows another optical mount according to an embodiment of the present invention. FIG. 3 shows a slit assembly according to an embodiment of the present invention. FIG. 3 shows a slit assembly according to an embodiment of the present invention. FIG. 3 shows a slit assembly according to an embodiment of the present invention. FIG. 3 shows a slit assembly according to an embodiment of the present invention.

Explanation of symbols

80 Primary beam splitter 88 Bandwidth meter 114 Beam 140 Secondary beam splitter 144 Photodetector module 162 Etalon

Claims (152)

Sub-nanometer equal to or greater than 15 mJ per pulse with femtometer bandwidth accuracy and tens of femtometer bandwidth accuracy range for measuring bandwidth per pulse at 4000 Hz and higher pulse repetition rates A wavelength meter for a high repetition rate gas discharge laser having a laser output beam including a pulse output of a pulse of bandwidth tuning range,
A focusing lens having a focal length;
An optical interferometer that generates an interference fringe pattern;
An optical detector positioned at the focal length from the focusing lens;
Calculate the bandwidth from the position of the interference fringe in the interference fringe pattern incident on the optical detector and assume that λ ₀ is constant, D ₀ = (D _OD −D _ID ) / 2, and f In accordance with the equation Δλ = λ ₀ [D _OD ² -D _ID ² ] / [8f ² -D ₀ ² ], the interference fringes on the axis of the interference pattern according to D _ID and D _OD A bandwidth calculator for determining respective distances between a pair of first fringe boundaries and a pair of second fringe boundaries in the pattern;
A wavelength meter comprising: The optical detector is a photodiode array;
The apparatus of claim 1 further comprising: The optical interferometer having a slit function;
The slit function and the focal length selected to provide two innermost fringes of the optical interference fringe pattern to the optical detector;
The apparatus of claim 1 further comprising: The optical interferometer having a slit function;
The slit function and the focal length selected to provide two innermost fringes of the optical interference fringe pattern to the optical detector;
The apparatus of claim 2 further comprising: The optical detector, wherein each pixel comprises an array of pixels having a height and a width, the array having a full width;
Light to the optical interferometer, wherein the output of the optical interferometer selectively inputs a portion of the light beam sufficient to illuminate the optical detector over the height of each respective pixel. The input opening,
The apparatus of claim 1 further comprising: The optical detector, wherein each pixel comprises an array of pixels having a height and a width, the array having a full width;
The optical interferometer, wherein the output of the optical interferometer selectively inputs to the optical interferometer a portion of the light beam sufficient to illuminate the optical detector over the height of each respective pixel height. The opening of the light input to the
The apparatus of claim 2 further comprising: The optical detector, wherein each pixel comprises an array of pixels having a height and a width, the array having a full width;
The optical interferometer, wherein the output of the optical interferometer selectively inputs to the optical interferometer a portion of the light beam sufficient to illuminate the optical detector over the height of each respective pixel height. The opening of the light input to the
4. The apparatus of claim 3, further comprising: The optical detector, wherein each pixel comprises an array of pixels having a height and a width, the array having a full width;
The optical interferometer, wherein the output of the optical interferometer selectively inputs to the optical interferometer a portion of the light beam sufficient to illuminate the optical detector over the height of each respective pixel height. The opening of the light input to the
The apparatus of claim 4 further comprising: The optical interferometer is an etalon;
The apparatus of claim 1 further comprising: The optical interferometer is an etalon;
The apparatus of claim 2 further comprising: The optical interferometer is an etalon;
4. The apparatus of claim 3, further comprising: The optical interferometer is an etalon;
5. The apparatus of claim 4, further comprising: The optical interferometer is an etalon;
6. The apparatus of claim 5, further comprising: The optical interferometer is an etalon;
The apparatus of claim 6 further comprising: The optical interferometer is an etalon;
The apparatus of claim 7 further comprising: The optical interferometer is an etalon;
The apparatus of claim 8 further comprising: The etalon is an etalon having a slit function of 3 pm or less and a finesse of 25 or more,
The focal length is 1.5 meters;
10. The apparatus of claim 9, further comprising: The etalon is an etalon having a slit function of 3 pm or less and a finesse of 25 or more,
The focal length is 1.5 meters;
The apparatus of claim 10 further comprising: The etalon is an etalon having a slit function of 3 pm or less and a finesse of 25 or more,
The focal length is 1.5 meters;
The apparatus of claim 11 further comprising: The etalon is an etalon having a slit function of 3 pm or less and a finesse of 25 or more,
The focal length is 1.5 meters;
The apparatus of claim 12, further comprising: The etalon is an etalon having a slit function of 3 pm or less and a finesse of 25 or more,
The focal length is 1.5 meters;
14. The apparatus of claim 13, further comprising: The etalon is an etalon having a slit function of 3 pm or less and a finesse of 25 or more,
The focal length is 1.5 meters;
15. The apparatus of claim 14, further comprising: The etalon is an etalon having a slit function of 3 pm or less and a finesse of 25 or more,
The focal length is 1.5 meters;
The apparatus of claim 15 further comprising: The etalon is an etalon having a slit function of 3 pm or less and a finesse of 25 or more,
The focal length is 1.5 meters;
The apparatus of claim 16 further comprising: A first diffuser for supplying narrow cone light to the etalon;
The apparatus of claim 17, further comprising: A first diffuser for supplying narrow cone light to the etalon;
The apparatus of claim 18 further comprising: A first diffuser for supplying narrow cone light to the etalon;
20. The apparatus of claim 19, further comprising: A first diffuser for supplying narrow cone light to the etalon;
21. The apparatus of claim 20, further comprising: A first diffuser for supplying narrow cone light to the etalon;
The apparatus of claim 21, further comprising: A first diffuser for supplying narrow cone light to the etalon;
The apparatus of claim 22 further comprising: A first diffuser for supplying narrow cone light to the etalon;
24. The apparatus of claim 23, further comprising: A first diffuser for supplying narrow cone light to the etalon;
25. The apparatus of claim 24, further comprising: An opening between the first diffuser and the etalon that supplies the etalon with a thin strip of narrow cone light;
26. The apparatus of claim 25, further comprising: An opening between the first diffuser and the etalon that supplies the etalon with a thin strip of narrow cone light;
27. The apparatus of claim 26, further comprising: An opening between the first diffuser and the etalon that supplies the etalon with a thin strip of narrow cone light;
28. The apparatus of claim 27, further comprising: An opening between the first diffuser and the etalon that supplies the etalon with a thin strip of narrow cone light;
30. The apparatus of claim 28, further comprising: An opening between the first diffuser and the etalon that supplies the etalon with a thin strip of narrow cone light;
30. The apparatus of claim 29, further comprising: An opening between the first diffuser and the etalon that supplies the etalon with a thin strip of narrow cone light;
32. The apparatus of claim 30, further comprising: An opening between the first diffuser and the etalon that supplies the etalon with a thin strip of narrow cone light;
32. The apparatus of claim 31, further comprising: An opening between the first stage diffuser and the etalon that supplies the etalon with a thin strip of narrow cone light;
The apparatus of claim 32, further comprising: Sub-nanometer equal to or greater than 15 mJ per pulse with femtometer bandwidth accuracy and tens of femtometer bandwidth accuracy range for measuring bandwidth per pulse at 4000 Hz and higher pulse repetition rates A wavelength meter for a high repetition rate gas discharge laser having a laser output beam including a pulse output of a pulse of bandwidth tuning range,
A focusing lens having a focal length;
An optical interference pattern generating means for generating an interference fringe pattern;
Optical detection means positioned at the focal length from the focusing lens;
Calculate the bandwidth from the position of the interference fringe in the interference fringe pattern incident on the optical detection means, and assume that λ ₀ is constant, D ₀ = (D _OD −D _ID ) / 2, and f In accordance with the equation Δλ = λ ₀ [D _OD ² -D _ID ² ] / [8f ² -D ₀ ² ], the interference fringes on the axis of the interference pattern according to D _ID and D _OD Bandwidth calculating means for determining respective distances between the pair of first fringe boundaries and the pair of second fringe boundaries in the pattern;
A wavelength meter comprising: The optical detection means is a photodiode array;
42. The apparatus of claim 41, further comprising: The optical interference pattern generating means having a slit function;
The slit function and the focal length selected to provide two innermost fringes of the optical interference annular pattern to the optical detection means;
42. The apparatus of claim 41, further comprising: The optical interference pattern generating means having a slit function;
The slit function and the focal length selected to provide the optical detector with two innermost fringes of the optical interference annular pattern;
43. The apparatus of claim 42, further comprising: The optical detection means wherein each pixel comprises an array of pixels having a height and a width, the array having a full width;
The output of the interference pattern generation means selectively inputs a portion of the light beam sufficient to illuminate the optical detection means over the height and full width of each respective pixel height to the optical interference pattern generation means. An aperture of a light input to the optical interferometer;
42. The apparatus of claim 41, further comprising: The optical detection means wherein each pixel comprises an array of pixels having a height and a width, the array having a full width;
The output of the interference pattern generation means selectively inputs a portion of the light beam sufficient to illuminate the optical detection means over the height and full width of each respective pixel height to the optical interference pattern generation means. An aperture of a light input to the optical interferometer;
43. The apparatus of claim 42, further comprising: The optical detection means wherein each pixel comprises an array of pixels having a height and a width, the array having a full width;
The output of the interference pattern generation means selectively inputs a portion of the light beam sufficient to illuminate the optical detection means over the height and full width of each respective pixel height to the optical interference pattern generation means. An aperture of a light input to the optical interferometer;
44. The apparatus of claim 43, further comprising: The optical detection means wherein each pixel comprises an array of pixels having a height and a width, the array having a full width;
The output of the interference pattern generation means selectively inputs a portion of the light beam sufficient to illuminate the optical detection means over the height and full width of each respective pixel height to the optical interference pattern generation means. An aperture of a light input to the optical interferometer;
45. The apparatus of claim 44, further comprising: The optical interference pattern generating means is an etalon.
42. The apparatus of claim 41, further comprising: The optical interference pattern generating means is an etalon.
43. The apparatus of claim 42, further comprising: The optical interference pattern generating means is an etalon.
44. The apparatus of claim 43, further comprising: The optical interference pattern generating means is an etalon.
45. The apparatus of claim 44, further comprising: The optical interference pattern generating means is an etalon.
46. The apparatus of claim 45, further comprising: The optical interference pattern generating means is an etalon.
The apparatus of claim 46, further comprising: The optical interference pattern generating means is an etalon.
48. The apparatus of claim 47, further comprising: The optical interference pattern generating means is an etalon.
49. The apparatus of claim 48, further comprising: The etalon is an etalon having a slit function of 3 pm or less and a finesse of 25 or more,
The focal length is 1.5 meters;
50. The apparatus of claim 49, further comprising: The etalon is an etalon having a slit function of 3 pm or less and a finesse of 25 or more,
The focal length is 1.5 meters;
51. The apparatus of claim 50, further comprising: The etalon is an etalon having a slit function of 3 pm or less and a finesse of 25 or more,
The focal length is 1.5 meters;
52. The apparatus of claim 51, further comprising: The etalon is an etalon having a slit function of 3 pm or less and a finesse of 25 or more,
The focal length is 1.5 meters;
53. The apparatus of claim 52, further comprising: The etalon is an etalon having a slit function of 3 pm or less and a finesse of 25 or more,
The focal length is 1.5 meters;
54. The apparatus of claim 53, further comprising: The etalon is an etalon having a slit function of 3 pm or less and a finesse of 25 or more,
The focal length is 1.5 meters;
55. The apparatus of claim 54, further comprising: The etalon is an etalon having a slit function of 3 pm or less and a finesse of 25 or more,
The focal length is 1.5 meters;
56. The apparatus of claim 55, further comprising: The etalon is an etalon having a slit function of 3 pm or less and a finesse of 25 or more,
The focal length is 1.5 meters;
57. The apparatus of claim 56, further comprising: A first diffuser for supplying narrow cone light to the etalon;
58. The apparatus of claim 57, further comprising: A first diffuser for supplying narrow cone light to the etalon;
59. The apparatus of claim 58, further comprising: A first diffuser for supplying narrow cone light to the etalon;
60. The apparatus of claim 59, further comprising: A first diffuser for supplying narrow cone light to the etalon;
61. The apparatus of claim 60, further comprising: A first diffuser for supplying narrow cone light to the etalon;
62. The apparatus of claim 61, further comprising: A first diffuser for supplying narrow cone light to the etalon;
64. The apparatus of claim 62, further comprising: A first diffuser for supplying narrow cone light to the etalon;
64. The apparatus of claim 63, further comprising: A first diffuser for supplying narrow cone light to the etalon;
65. The apparatus of claim 64, further comprising: An opening between the first diffuser and the etalon that supplies the etalon with a thin strip of narrow cone light;
66. The apparatus of claim 65, further comprising: An opening between the first diffuser and the etalon that supplies the etalon with a thin strip of narrow cone light;
68. The apparatus of claim 66, further comprising: An opening between the first diffuser and the etalon that supplies the etalon with a thin strip of narrow cone light;
68. The apparatus of claim 67, further comprising: An opening between the first diffuser and the etalon that supplies the etalon with a thin strip of narrow cone light;
69. The apparatus of claim 68, further comprising: An opening between the first diffuser and the etalon that supplies the etalon with a thin strip of narrow cone light;
70. The apparatus of claim 69, further comprising: An opening between the first stage diffuser and the etalon that supplies the etalon with a thin strip of narrow cone light;
71. The apparatus of claim 70, further comprising: An opening between the first diffuser and the etalon that supplies the etalon with a thin strip of narrow cone light;
72. The apparatus of claim 71, further comprising: An opening between the first diffuser and the etalon that supplies the etalon with a thin strip of narrow cone light;
75. The apparatus of claim 72, further comprising: Sub-nanometer equal to or greater than 15 mJ per-pulse with femtometer bandwidth accuracy and tens of femtometer bandwidth accuracy range for measuring bandwidth per pulse at 4000 Hz and higher pulse repetition rates A method for measuring the bandwidth of light produced by a high repetition rate gas discharge laser having a laser output beam including a pulse output of a pulse of bandwidth tuning range comprising:
Focusing light onto a lens having a focal length;
Generating an interference fringe pattern; and
Detecting the interference fringe pattern at an optical detector positioned at the focal length from the lens;
A bandwidth is calculated from the position of the interference fringe in the interference fringe pattern incident on the optical detector, and a wavelength assuming that λ ₀ is constant, D ₀ = (D _OD −D _ID ) / 2, and f is calculated. According to the formula Δλ = λ ₀ [D _OD ² -D _ID ² ] / [8f ² -D ₀ ² ] when the focal length is used, the interference fringe on the axis of the interference fringe pattern is represented by D _ID and D _OD . Determining respective distances between a pair of first fringe boundaries and a pair of second fringe boundaries in the pattern;
A method comprising the steps of: The optical detector is a photodiode array;
82. The method of claim 81, further comprising: Generating the interference pattern in an optical interferometer having a slit function;
Further including
The slit function and the focal length are selected to provide two innermost fringes of the optical interference annular pattern to the optical detection means,
82. The method of claim 81, wherein: Generating the interference pattern in an optical interferometer having a slit function;
Further including
The slit function and the focal length are selected to provide two innermost fringes of the optical interference annular pattern to the optical detector,
83. The method of claim 82, wherein: The optical detector includes an array of pixels, each pixel having a height and width, and the array has a full width;
Generating the interference fringe pattern in an optical interferometer;
Selectively inputting into the optical interferometer a slit portion of a light beam sufficient for the output of the optical interferometer to illuminate the optical detection means over the height of each respective pixel height;
The method of claim 81, further comprising: The optical detector includes an array of pixels, each pixel having a height and width, and the array has a full width;
Generating the interference fringe pattern in an optical interferometer;
Selectively inputting into the optical interferometer a slit portion of a light beam sufficient for the output of the optical interferometer to illuminate the optical detection means over the height of each respective pixel height;
The method of claim 82, further comprising: The optical detector includes an array of pixels, each pixel having a height and width, and the array has a full width;
Selectively inputting into the optical interferometer a slit portion of a light beam sufficient for the output of the optical interferometer to illuminate the optical detection means over the height of each respective pixel height;
84. The method of claim 83, further comprising: The optical detector includes an array of pixels, each pixel having a height and width, and the array has a full width;
Selectively inputting into the optical interferometer a slit portion of a light beam sufficient for the output of the optical interferometer to illuminate the optical detection means over the height of each respective pixel height;
85. The method of claim 84, further comprising: Generating the interference pattern in an etalon having a slit function;
The method of claim 81, further comprising: Generating the interference pattern in an etalon having a slit function;
The method of claim 82, further comprising: The optical interferometer is an etalon;
84. The method of claim 83, further comprising: The optical interferometer is an etalon;
85. The method of claim 84, further comprising: The optical interferometer is an etalon;
86. The method of claim 85, further comprising: The optical interferometer is an etalon;
90. The method of claim 86, further comprising: The optical interferometer is an etalon;
88. The method of claim 87, further comprising: The optical interferometer is an etalon;
90. The method of claim 88, further comprising: The etalon is an etalon having a slit function of 3 pm or less and a finesse of 25 or more,
The focal length is 1.5 meters;
90. The method of claim 89, further comprising: The etalon is an etalon having a slit function of 3 pm or less and a finesse of 25 or more,
The focal length is 1.5 meters;
The method of claim 90, further comprising: The etalon is an etalon having a slit function of 3 pm or less and a finesse of 25 or more,
The focal length is 1.5 meters;
94. The method of claim 91, further comprising: The etalon is an etalon having a slit function of 3 pm or less and a finesse of 25 or more,
The focal length is 1.5 meters;
94. The method of claim 92, further comprising: The etalon is an etalon having a slit function of 3 pm or less and a finesse of 25 or more,
The focal length is 1.5 meters;
94. The method of claim 93, further comprising: The etalon is an etalon having a slit function of 3 pm or less and a finesse of 25 or more,
The focal length is 1.5 meters;
95. The method of claim 94, further comprising: The etalon is an etalon having a slit function of 3 pm or less and a finesse of 25 or more,
The focal length is 1.5 meters;
96. The method of claim 95, further comprising: The etalon is an etalon having a slit function of 3 pm or less and a finesse of 25 or more,
The focal length is 1.5 meters;
99. The method of claim 96, further comprising: Supplying a narrow cone of diffused light to the etalon;
98. The method of claim 97, further comprising: Supplying a narrow cone of diffused light to the etalon;
99. The method of claim 98, further comprising: Supplying a narrow cone of diffused light to the etalon;
The method of claim 99, further comprising: Supplying a narrow cone of diffused light to the etalon;
101. The method of claim 100, further comprising: Supplying a narrow cone of diffused light to the etalon;
102. The method of claim 101, further comprising: Supplying a narrow cone of diffused light to the etalon;
103. The method of claim 102, further comprising: Supplying a narrow cone of diffused light to the etalon;
104. The method of claim 103, further comprising: Supplying a narrow cone of diffused light to the etalon;
105. The method of claim 104, further comprising: Passing the narrow cone light through the slit opening;
106. The method of claim 105, further comprising: Passing the narrow cone light through the slit opening;
107. The method of claim 106, further comprising: Passing the narrow cone light through the slit opening;
108. The method of claim 107, further comprising: Passing the narrow cone light through the slit opening;
109. The method of claim 108, further comprising: Passing the narrow cone light through the slit opening;
110. The method of claim 109, further comprising: Passing the narrow cone light through the slit opening;
111. The method of claim 110, further comprising: Passing the narrow cone light through the slit opening;
112. The method of claim 111, further comprising: Passing the narrow cone light through the slit opening;
113. The method of claim 112, further comprising: A beam reducer in the path of the beam in front of the optical interferometer;
A second diffuser between the beam reducer and the optical interferometer;
Further including
The beam reducer reduces the beam more in a first axis than in a second axis to conform the beam cross-section to the shape of the second diffuser;
34. The apparatus of claim 33. A beam reducer in the path of the beam in front of the optical interferometer;
A second diffuser between the beam reducer and the optical interferometer;
Further including
The beam reducer reduces the beam more in a first axis than in a second axis to conform the beam cross-section to the shape of the second diffuser;
35. The apparatus of claim 34. A beam reducer in the path of the beam in front of the optical interferometer;
A second diffuser between the beam reducer and the optical interferometer;
Further including
The beam reducer reduces the beam more in a first axis than in a second axis to conform the beam cross-section to the shape of the second diffuser;
36. The apparatus of claim 35. A beam reducer in the path of the beam in front of the optical interferometer;
A second diffuser between the beam reducer and the optical interferometer;
Further including
The beam reducer reduces the beam more in a first axis than in a second axis to conform the beam cross-section to the shape of the second diffuser;
37. The apparatus of claim 36. A beam reducer in the path of the beam in front of the optical interferometer;
A second diffuser between the beam reducer and the optical interferometer;
Further including
The beam reducer reduces the beam more in a first axis than in a second axis to conform the beam cross-section to the shape of the second diffuser;
38. The apparatus of claim 37. A beam reducer in the path of the beam in front of the optical interferometer;
A second diffuser between the beam reducer and the optical interferometer;
Further including
The beam reducer reduces the beam more in a first axis than in a second axis to conform the beam cross-section to the shape of the second diffuser;
40. The apparatus of claim 38. A beam reducer in the path of the beam in front of the optical interferometer;
A second diffuser between the beam reducer and the optical interferometer;
Further including
The beam reducer reduces the beam more in a first axis than in a second axis to conform the beam cross-section to the shape of the second diffuser;
40. The apparatus of claim 39. A beam reducer in the path of the beam in front of the optical interferometer;
A second diffuser between the beam reducer and the optical interferometer;
Further including
The beam reducer reduces the beam more in a first axis than in a second axis to conform the beam cross-section to the shape of the second diffuser;
41. The apparatus of claim 40. Beam reduction means in the path of the beam in front of the optical interferometer;
A second diffuser between the beam reducing means and the optical interferometer;
Further including
The beam reducing means reduces the beam more in the first axis than in the second axis in order to match the cross section of the beam to the shape of the second diffuser;
74. The apparatus of claim 73. Beam reduction means in the path of the beam in front of the optical interferometer;
A second diffuser between the beam reducing means and the optical interferometer;
Further including
The beam reducing means reduces the beam more in the first axis than in the second axis in order to match the cross section of the beam to the shape of the second diffuser;
75. The apparatus of claim 74. Beam reduction means in the path of the beam in front of the optical interferometer;
A second diffuser between the beam reducing means and the optical interferometer;
Further including
The beam reducing means reduces the beam more in the first axis than in the second axis in order to match the cross section of the beam to the shape of the second diffuser;
78. The apparatus of claim 75. Beam reduction means in the path of the beam in front of the optical interferometer;
A second diffuser between the beam reducing means and the optical interferometer;
Further including
The beam reducing means reduces the beam more in the first axis than in the second axis in order to match the cross section of the beam to the shape of the second diffuser;
77. The apparatus of claim 76. Beam reduction means in the path of the beam in front of the optical interferometer;
A second diffuser between the beam reducing means and the optical interferometer;
Further including
The beam reducing means reduces the beam more in the first axis than in the second axis in order to match the cross section of the beam to the shape of the second diffuser;
78. The apparatus of claim 77. Beam reduction means in the path of the beam in front of the optical interferometer;
A second diffuser between the beam reducing means and the optical interferometer;
Further including
The beam reducing means reduces the beam more in the first axis than in the second axis in order to match the cross section of the beam to the shape of the second diffuser;
79. The apparatus of claim 78. Beam reduction means in the path of the beam in front of the optical interferometer;
A second diffuser between the beam reducing means and the optical interferometer;
Further including
The beam reducing means reduces the beam more in the first axis than in the second axis in order to match the cross section of the beam to the shape of the second diffuser;
80. The apparatus of claim 79. Beam reduction means in the path of the beam in front of the optical interferometer;
A second diffuser between the beam reducing means and the optical interferometer;
Further including
The beam reducing means reduces the beam more in the first axis than in the second axis in order to match the cross section of the beam to the shape of the second diffuser;
81. The device of claim 80. Reducing the beam before generating the interference pattern;
Diffusing the reduced beam into a second diffuser;
Shrinking the beam more in the first axis than in the second axis to conform the cross-section of the beam to the shape of the second diffuser;
114. The method of claim 113, further comprising: Reducing the beam before generating the interference pattern;
Diffusing the reduced beam into a second diffuser;
Shrinking the beam more in the first axis than in the second axis to conform the cross-section of the beam to the shape of the second diffuser;
115. The method of claim 114, further comprising: Reducing the beam before generating the interference pattern;
Diffusing the reduced beam into a second diffuser;
Reducing the beam more in the first axis than in the second axis to match the cross-section of the beam to the shape of the diffuser;
118. The method of claim 115, further comprising: Reducing the beam before generating the interference pattern;
Diffusing the reduced beam into a diffuser;
Shrinking the beam more in the first axis than in the second axis to conform the cross-section of the beam to the shape of the second diffuser;
117. The method of claim 116, further comprising: Reducing the beam before generating the interference pattern;
Diffusing the reduced beam into a second diffuser;
Shrinking the beam more in the first axis than in the second axis to conform the cross-section of the beam to the shape of the second diffuser;
118. The method of claim 117, further comprising: Reducing the beam before generating the interference pattern;
Diffusing the reduced beam into a second diffuser;
Shrinking the beam more in the first axis than in the second axis to conform the cross-section of the beam to the shape of the second diffuser;
119. The method of claim 118, further comprising: Reducing the beam before generating the interference pattern;
Diffusing the reduced beam into a second diffuser;
Shrinking the beam more in the first axis than in the second axis to conform the cross-section of the beam to the shape of the second diffuser;
120. The method of claim 119, further comprising: Reducing the beam before generating the interference pattern;
Diffusing the reduced beam into a second diffuser;
Shrinking the beam more in the first axis than in the second axis to conform the cross-section of the beam to the shape of the second diffuser;
121. The method of claim 120, further comprising: The first diffuser includes an etched polished glass diffuser that emits a cone angle less than 15 degrees;
26. The apparatus of claim 25, further comprising: The first diffuser includes an etched polished glass diffuser that emits a cone angle less than 15 degrees;
27. The apparatus of claim 26, further comprising: The first diffuser includes an etched polished glass diffuser that emits a cone angle less than 15 degrees;
28. The apparatus of claim 27, further comprising: The first diffuser includes an etched polished glass diffuser that emits a cone angle less than 15 degrees;
30. The apparatus of claim 28, further comprising: The first diffuser includes an etched polished glass diffuser that emits a cone angle less than 15 degrees;
30. The apparatus of claim 29, further comprising: The first diffuser includes an etched polished glass diffuser that emits a cone angle less than 15 degrees;
32. The apparatus of claim 30, further comprising: The first diffuser includes an etched polished glass diffuser that emits a cone angle less than 15 degrees;
32. The apparatus of claim 31, further comprising: The first diffuser includes an etched polished glass diffuser that emits a cone angle less than 15 degrees;
The apparatus of claim 32, further comprising:

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