Abstract: An improved solid-state laser for generating sub-200 nm light is described. This laser uses a fundamental wavelength between about 1030 nm and 1065 nm to generate the sub-200 nm light. The final frequency conversion stage of the laser creates the sub-200 nm light by mixing a wavelength of approximately 1109 nm with a wavelength of approximately 234 nm. By proper selection of non-linear media, such mixing can be achieved by nearly non-critical phase matching. This mixing results in high conversion efficiency, good stability, and high reliability.

Abstract: A repetition rate (pulse) multiplier includes one or more beam splitters and prisms forming one or more ring cavities with different optical path lengths that delay parts of the energy of each pulse. A series of input laser pulses circulate in the ring cavities and part of the energy of each pulse leaves the system after traversing the shorter cavity path, while another part of the energy leaves the system after traversing the longer cavity path, and/or a combination of both cavity paths. By proper choice of the ring cavity optical path length, the repetition rate of an output series of laser pulses can be made to be a multiple of the input repetition rate. The relative energies of the output pulses can be controlled by choosing the transmission and reflection coefficients of the beam splitters. Some embodiments generate a time-averaged output beam profile that is substantially flat in one dimension.

Abstract: Improved inspection systems utilize laser systems and associated techniques to generate an ultra-violet (UV) wavelength of approximately 193.368 nm from a fundamental vacuum wavelength near 1063.5 nm. Preferred embodiments separate out an unconsumed portion of an input wavelength to at least one stage and redirect that unconsumed portion for use in another stage. The improved laser systems and associated techniques result in less expensive, longer life lasers than those currently being used in the industry. These laser systems can be constructed with readily-available, relatively inexpensive components.

Abstract: A repetition rate (pulse) multiplier includes one or more beam splitters and prisms forming one or more ring cavities with different optical path lengths that delay parts of the energy of each pulse. A series of input laser pulses circulate in the ring cavities and part of the energy of each pulse leaves the system after traversing the shorter cavity path, while another part of the energy leaves the system after traversing the longer cavity path, and/or a combination of both cavity paths. By proper choice of the ring cavity optical path length, the repetition rate of an output series of laser pulses can be made to be a multiple of the input repetition rate. The relative energies of the output pulses can be controlled by choosing the transmission and reflection coefficients of the beam splitters. Some embodiments generate a time-averaged output beam profile that is substantially flat in one dimension.

Abstract: The present invention is directed to a beam dump which is configured for not increasing a temperature of a laser with which it may be implemented. The beam dump may include an opaque enclosure which is configured for receiving light (ex.—initial light) from a light source (ex.—a frequency-converted laser), said light being delivered through an aperture of the enclosure via one or more connected optical fibers. The received light may be scattered within the enclosure. However, the beam dump is configured for minimizing the amount of light which is back scattered light into the fiber(s). For instance, the amount of back scattered light may be less than 1/1000 of the initial light. Further, the beam dump may be configured for minimizing photocontamination which may be caused when the light contacts interior surfaces of the enclosure. Still further, the beam dump may be a small size, low cost structure.

Abstract: A pulse multiplier includes a polarizing beam splitter, a wave plate, and a set of multi-surface reflecting components (e.g., one or more etalons and one or more mirrors). The polarizing beam splitter passes input laser pulses through the wave plate to the multi-surface reflecting components, which reflect portions of each input laser pulse back through the wave plate to the polarizing beam splitter. The polarizing beam splitter reflects each reflected portion to form an output of the pulse multiplier. The multi-surface reflecting components are configured such that the output pulses exiting the pulse multiplier have an output repetition pulse frequency rate that is at least double the input repetition pulse frequency.

Abstract: A pulsed UV laser assembly includes a partial reflector or beam splitter that divides each fundamental pulse into two sub-pulses and directs one sub-pulse to one end of a Bragg grating and the other pulse to the other end of the Bragg grating (or another Bragg grating) such that both sub-pulses are stretched and receive opposing (positive and negative) frequency chirps. The two stretched sub-pulses are combined to generate sum frequency light having a narrower bandwidth than could be obtained by second-harmonic generation directly from the fundamental. UV wavelengths may be generated directly from the sum frequency light or from a harmonic conversion scheme incorporating the sum frequency light. The UV laser may further incorporate other bandwidth reducing schemes. The pulsed UV laser may be used in an inspection or metrology system.

Abstract: A frequency-conversion crystal annealing process includes a first ramp-up period (e.g., increasing the crystal's temperature to a first set point in the range of 100° C. to 150° C. over about 2 hours), a first fixed temperature period (e.g., maintaining at the first set point for 10 to 20 hours), a second ramp-up period (e.g., increasing from the first set point to a second set point above 150° C. over about 1 hour or more), a second fixed period (e.g., maintaining at the second set point for 48 to 300 hours), and then a temperature ramp-down period (e.g., decreasing from the second set point to room temperature over about 3 hours). Transitions from the first and second fixed temperature periods are optionally determined by —OH bonds absorption levels that are measured using Fourier transform infrared spectroscopy, e.g., by monitoring the absorption of —OH bonds (including H2O) near 3580 cm?1 in the infra-red spectrum.

Abstract: A catadioptric objective configured to inspect a specimen is provided. The catadioptric objective includes a Mangin element having one surface at a first axial location and an extension element positioned together with the Mangin element. The extension element provides a second surface at a second axial location. Certain light energy reflected from the specimen passes to the second surface of the extension element, the Mangin element, and through a plurality of lenses. An aspheric surface may be provided, and light energy may be provided to the specimen using diverting elements such as prisms or reflective surfaces.

Abstract: A laser for generating an output wavelength of approximately 193.4 nm includes a fundamental laser, an optical parametric generator, a fourth harmonic generator, and a frequency mixing module. The optical parametric generator, which is coupled to the fundamental laser, can generate a down-converted signal. The fourth harmonic generator, which may be coupled to the optical parametric generator or the fundamental laser, can generate a fourth harmonic. The frequency mixing module, which is coupled to the optical parametric generator and the fourth harmonic generator, can generate a laser output at a frequency equal to a sum of the fourth harmonic and twice a frequency of the down-converted signal.

Abstract: A laser assembly for generating laser output light at an output wavelength of approximately 183 nm includes a fundamental laser, an optical parametric system (OPS), a fifth harmonic generator, and a frequency mixing module. The fundamental laser generates fundamental light at a fundamental frequency. The OPS generates a down-converted signal at a down-converted frequency. The fifth harmonic generator generates a fifth harmonic of the fundamental light. The frequency mixing module mixes the down-converted signal and the fifth harmonic to produce the laser output light at a frequency equal to a sum of the fifth harmonic frequency and the down-converted frequency. The OPS generates the down-converted signal by generating a down-converted seed signal at the down-converted frequency, and then mixing the down-converted seed signal with a portion of the fundamental light.

Abstract: A pulsed UV laser assembly includes a partial reflector or beam splitter that divides each fundamental pulse into two sub-pulses and directs one sub-pulse to one end of a Bragg grating and the other pulse to the other end of the Bragg grating (or another Bragg grating) such that both sub-pulses are stretched and receive opposing (positive and negative) frequency chirps. The two stretched sub-pulses are combined to generate sum frequency light having a narrower bandwidth than could be obtained by second-harmonic generation directly from the fundamental. UV wavelengths may be generated directly from the sum frequency light or from a harmonic conversion scheme incorporating the sum frequency light. The UV laser may further incorporate other bandwidth reducing schemes. The pulsed UV laser may be used in an inspection or metrology system.

Abstract: An improved laser uses a pump laser with a wavelength near 1109 nm and a fundamental wavelength near 1171 nm to generate light at a wavelength between approximately 189 nm and approximately 200 nm, e.g. 193 nm. The laser mixes the 1109 nm pump wavelength with the 5th harmonic of the 1171 nm fundamental, which is at a wavelength of approximately 234.2 nm. By proper selection of non-linear media, such mixing can be achieved by nearly non-critical phase matching. This mixing results in high conversion efficiency, good stability, and high reliability.

Abstract: A repetition rate (pulse) multiplier includes one or more beam splitters and prisms forming one or more ring cavities with different optical path lengths that delay parts of the energy of each pulse. A series of input laser pulses circulate in the ring cavities and part of the energy of each pulse leaves the system after traversing the shorter cavity path, while another part of the energy leaves the system after traversing the longer cavity path, and/or a combination of both cavity paths. By proper choice of the ring cavity optical path length, the repetition rate of an output series of laser pulses can be made to be a multiple of the input repetition rate. The relative energies of the output pulses can be controlled by choosing the transmission and reflection coefficients of the beam splitters. Some embodiments generate a time-averaged output beam profile that is substantially flat in one dimension.

Abstract: A pulse multiplier includes a beam splitter and one or more mirrors. The beam splitter receives a series of input laser pulses and directs part of the energy of each pulse into a ring cavity. After circulating around the ring cavity, part of the pulse energy leaves the ring cavity through the beam splitter and part of the energy is recirculated. By selecting the ring cavity optical path length, the repetition rate of an output series of laser pulses can be made to be a multiple of the input repetition rate. The relative energies of the output pulses can be controlled by choosing the transmission and reflection coefficients of the beam splitter. This pulse multiplier can inexpensively reduce the peak power per pulse while increasing the number of pulses per second with minimal total power loss.

Abstract: A laser system for semiconductor inspection includes a fiber-based fundamental light source for generating fundamental light that is then converted/mixed by a frequency conversion module to generate UV-DUV laser light. The fundamental light source includes a nonlinear chirp element (e.g., a Bragg grating or an electro-optic modulator) that adds a nonlinear chirp to the seed light laser system prior to amplification by the fiber amplifier(s) (e.g., doped fiber or Raman amplifiers). The nonlinear chirp includes an x2 or higher nonlinearity and is configured to compensates for the Self Phase Modulation (SPM) characteristics of the fiber-based amplifiers such that fundamental light is generated that has a spectral E95 bandwidth within five times that of the seed light. When multiple series-connected amplifiers are used, either a single nonlinear chirp element is provided before the amplifier string, or a chirp elements are included before each amplifier.

Abstract: A frequency-conversion crystal annealing process includes a first ramp-up period (e.g., increasing the crystal's temperature to a first set point in the range of 100° C. to 150° C. over about 2 hours), a first fixed temperature period (e.g., maintaining at the first set point for 10 to 20 hours), a second ramp-up period (e.g., increasing from the first set point to a second set point above 150° C. over about 1 hour or more), a second fixed period (e.g., maintaining at the second set point for 48 to 300 hours), and then a temperature ramp-down period (e.g., decreasing from the second set point to room temperature over about 3 hours). Transitions from the first and second fixed temperature periods are optionally determined by —OH bonds absorption levels that are measured using Fourier transform infrared spectroscopy, e.g., by monitoring the absorption of —OH bonds (including H2O) near 3580 cm?1 in the infra-red spectrum.

Abstract: The present invention includes a fundamental laser light source configured to generate fundamental wavelength laser light, a first nonlinear optical crystal configured to generate first alternate wavelength light, a second nonlinear optical crystal configured to generate second alternate wavelength light, a dual wavelength Brewster angle waveplate configured to rotate a polarization of the first alternate wavelength light relative to the second alternate wavelength light such that the first and second alternate wavelength light have the same polarization, a set of Brewster angle wavefront processing optics configured to condition the first and second alternate wavelengths of light, a harmonic separator configured to separate the first alternate wavelength light from the second alternate wavelength light, and a Brewster angle output window configured to transmit the first or second alternate wavelengths of light from the interior of a laser frequency conversion system to the exterior of the laser frequency con

Abstract: A pulse multiplier includes a beam splitter and one or more mirrors. The beam splitter receives a series of input laser pulses and directs part of the energy of each pulse into a ring cavity. After circulating around the ring cavity, part of the pulse energy leaves the ring cavity through the beam splitter and part of the energy is recirculated. By selecting the ring cavity optical path length, the repetition rate of an output series of laser pulses can be made to be a multiple of the input repetition rate. The relative energies of the output pulses can be controlled by choosing the transmission and reflection coefficients of the beam splitter. This pulse multiplier can inexpensively reduce the peak power per pulse while increasing the number of pulses per second with minimal total power loss.

Abstract: An optical system for detecting contaminants and defects on a test surface includes an improved laser system for generating a laser beam and optics directing the laser beam along a path onto the test surface, and producing an illuminated spot thereon. A detector and ellipsoidal mirrored surface are also provided with an axis of symmetry about a line perpendicular to the test surface. In one embodiment, an optical system for detecting anomalies of a sample includes the improved laser system for generating first and second beams, first optics for directing the first beam of radiation onto a first spot on the sample, second optics for directing the second beam onto a second spot on the sample, with the first and second paths at different angles of incidence to the sample surface. In another embodiment, a surface inspection apparatus includes an illumination system configured to focus beams at non-normal incidence angles.