Abstract: A broadband radiation device, comprising: a pulse shaper configured to impose a temporal profile onto an input pump pulse so as to generate a temporally-modulated pump pulse, the temporally-modulated pump pulse having a different temporal profile than the input pump pulse; and a hollow-core photonic crystal fiber (HC-PCF) having a hollow core for confining in use a working medium under a pressure, the HC-PCF being operable to receive the temporally-modulated pump pulse; wherein the temporally-modulated pump pulse is configured to be spectrally broadened by a soliton self-compression process to form broadband output radiation while propagating through the hollow core of the HC-PCF; and said temporal profile is configured so as to configure a spectrum of the broadband output radiation to have target spectrum characteristics.

Abstract: A radiation source includes: a hollow core optical fiber, a working medium; and a pulsed pump radiation source. The hollow core optical fiber has a body and has a hollow core. The working medium is disposed within the hollow core. The pulsed pump radiation source is arranged to produce pulsed pump radiation that is received by, and propagates through, the hollow core from an input end to an output end. One or more parameters of the pulsed pump radiation, the optical fiber and the working medium are configured to allow soliton self-compression of the pulsed pump radiation so as to change a spectrum of the pulsed pump radiation so as to form output radiation. In some embodiments, a length of the optical fiber is such that the output end substantially coincides with a position at which a temporal extent of the pulsed pump radiation is minimal.

Abstract: A supercontinuum radiation source including a modulator being operable to modulate pump laser radiation including a train of radiation pulses to provide modulated pump laser radiation, the modulation being such to selectively provide a burst of the pulses; and a hollow-core photonic crystal fiber being operable to receive the modulated pump laser radiation and excite a working medium contained within the hollow-core photonic crystal fiber so as to generate supercontinuum radiation.

Abstract: A broadband light source device for creating broadband light pulses includes a hollow-core fiber and a pump laser source device. The hollow-core fiber is configured to create the broadband light pulses by an optical non-linear broadening of pump laser pulses. The hollow-core fiber includes a filling gas, an axial hollow light guiding fiber core configured to support core modes of a guided light field, and an inner fiber structure surrounding the fiber core and configured to support transverse wall modes of the guided light field. The pump laser source device is configured to create and provide the pump laser pulses at an input side of the hollow-core fiber. The transverse wall modes include a fundamental transverse wall mode and second and higher order transverse wall modes.

Abstract: A broadband radiation source device configured for generating broadband output radiation upon receiving substantially linearly polarized input radiation, the source device including: a hollow-core photonic crystal fiber; at least a first polarization element operable to impose a substantially circular or elliptical polarization on the input radiation prior to being received by the hollow-core photonic crystal fiber; and a second polarization element operable in combination with the first polarization element to impose a substantially elliptical polarization on the input radiation, wherein the second polarization element and the first polarization element are oriented such that the elliptical polarization compensates at least partially for birefringence of the hollow-core photonic crystal fiber.

Abstract: A method of producing photonic crystal fibers (PCFs) is disclosed, the method includes: 1) obtaining an intermediate PCF having an initial outer fiber diameter of less than 1 mm; and 2) elongating the intermediate PCF so as to controllably reduce at least one dimension of the intermediate PCF.

Abstract: Provided are light sources and methods of controlling them, and devices and methods for use in measurement applications, particularly in metrology, for example in a lithographic apparatus. The methods and devices provide mechanisms for detection and/or correction of variations in the light source, in particular stochastic variations. Feedback or feedforward approaches can be used for the correction of the source and/or the metrology outputs. An exemplary method of controlling the spectral output of a light source which emits a time-varying spectrum of light includes the steps of: determining at least one characteristic of the spectrum of light emitted from the light source; and using said determined characteristic to control the spectral output.

Abstract: A monolithic optical element for generating broadband radiation upon receiving input radiation at an input end of the optical element is disclosed, the optical element including: a hollow core region for guiding the input radiation along a longitudinal axis of the optical element towards an output end of the optical element; a cladding region surrounding the core region along the longitudinal axis and including transversally arranged micro-structures configured to provide non-linear optical behavior to the optical element causing the generation of the broadband radiation; and a supporting region surrounding the cladding region along the longitudinal axis of at least part of the optical element, wherein the supporting region has a transversal dimension which is sufficiently large to render the at least part of the optical element substantially rigid.

Abstract: A radiation source including: a hollow core optical fiber having a body having a hollow core for confining a working medium, the hollow core optical fiber being operable to receive pulsed pump radiation such that the received pulsed pump radiation propagates through the hollow core from an input end to an output end of the hollow core optical fiber, wherein one or more source parameters of the radiation source are configured such that the pulsed pump radiation undergoes a soliton self-compression process so as to change a spectrum of the pulsed pump radiation to form output radiation; and at least one dispersion control mechanism being operable to change dispersion characteristics in a first portion of the optical fiber so as to spectrally shift a dispersive wave generated in the soliton self-compression process.

Abstract: Provided are light sources and methods of controlling them, and devices and methods for use in measurement applications, particularly in metrology, for example in a lithographic apparatus. The methods and devices provide mechanisms for detection and/or correction of variations in the light source, in particular stochastic variations. Feedback or feedforward approaches can be used for the correction of the source and/or the metrology outputs. An exemplary method of controlling the spectral output of a light source which emits a time-varying spectrum of light includes the steps of: determining at least one characteristic of the spectrum of light emitted from the light source; and using said determined characteristic to control the spectral output.

Abstract: An optical filter apparatus including an optical divergence device, operable to receive optical pulses and spatially distribute the optical pulses over an optical plane in dependence with a pulse energy of each of the optical pulses; and a spatial filter, located at the optical plane, operable to apply spatial filtering to the optical pulses based on a location of each of the optical pulses at the optical plane resulting from the spatial distributing.

Abstract: A broadband radiation source device configured for generating a broadband output radiation upon receiving pump radiation, the device including: a hollow-core photonic crystal fiber (HC-PCF) including at least one structurally varied portion having at least one structural parameter of the HC-PCF varied with respect to one or more main portions of the HC-PCF, wherein the at least one structurally varied portion includes at least a structurally varied portion located downstream of a position along the length of the HC-PCF where the pump radiation will be spectrally expanded by a modulation instability dominated nonlinear optical process, and wherein the at least one structurally varied portion is configured and located such that the broadband output radiation includes wavelengths in the ultraviolet region.

Abstract: A supercontinuum radiation source including a modulator being operable to modulate pump laser radiation including a train of radiation pulses to provide modulated pump laser radiation, the modulation being such to selectively provide a burst of the pulses; and a hollow-core photonic crystal fiber being operable to receive the modulated pump laser radiation and excite a working medium contained within the hollow-core photonic crystal fiber so as to generate supercontinuum radiation.

Abstract: A radiation source for generating broadband radiation, the source including an input assembly for providing input radiation and a hollow-core photonic crystal fiber configured to receive and confine the input radiation coupled into the fiber for generating broadband radiation through spectral broadening, wherein the input assembly includes a pump source configured to provide input radiation having an average power of at least 50 W, and wherein the hollow core photonic crystal fiber includes: a hollow core having a diameter of at least 35 ?m; and a cladding region including a plurality of anti-resonant structures surrounding the hollow core, the anti-resonant structures including a wall portion having a wall thickness smaller than half the wavelength of the lower end of a wavelength range of the broadband radiation.

Abstract: A radiation source for generating broadband radiation, the source including: a pump source having only one single fiber amplifier configured to generate pump radiation including a plurality of radiation pulses having a pulse energy of 2.5 ?J or less; and a hollow core fiber having a hollow core region and a cladding surrounding the hollow core region, the hollow core region having a pressurized gas therein, and the hollow core fiber being arranged to receive, at an input end, the pump radiation, wherein the hollow core region is dimensioned such that the radiation pulses have a soliton order higher than 16 so as to broaden a spectrum of the pump radiation using modulation instability as the pump radiation propagates along the hollow-core fiber, for providing output broadband radiation from an output end of the hollow core fiber.

Abstract: Optical components and methods of manufacture thereof. A first optical component has a hollow-core photonic crystal fiber includes internal capillaries for guiding radiation and an outer capillary sheathing the internal capillaries; and at least an output end section having a larger inner cross-sectional dimension over at least a portion of the output end section than an inner cross-sectional dimension of the outer capillary along a central portion of the hollow-core photonic crystal fiber prior to the output end section. A second optical component includes a hollow-core photonic crystal fiber and a sleeve arrangement.

Abstract: A radiation source arrangement including: a radiation source operable to generate source radiation including source energy pulses; and at least one non-linear energy-filter operable to filter the source radiation to obtain filtered radiation including filtered energy pulses. The at least one non-linear energy-filter is operable to mitigate variation in energy in the filtered radiation by reducing the energy level of the source energy pulses which have an energy level corresponding to one of both extremities of an energy distribution of the source energy pulses by a greater amount than the source energy pulses which have an energy level corresponding to a peak of the energy distribution.

Abstract: A broadband radiation source device configured for generating a broadband output radiation upon receiving pump radiation, the device including: a hollow-core photonic crystal fiber (HC-PCF) including at least one structurally varied portion having at least one structural parameter of the HC-PCF varied with respect to one or more main portions of the HC-PCF, wherein the at least one structurally varied portion includes at least a structurally varied portion located downstream of a position along the length of the HC-PCF where the pump radiation will be spectrally expanded by a modulation instability dominated nonlinear optical process, and wherein the at least one structurally varied portion is configured and located such that the broadband output radiation includes wavelengths in the ultraviolet region.

Abstract: A supercontinuum radiation source including a modulator being operable to modulate pump laser radiation including a train of radiation pulses to provide modulated pump laser radiation, the modulation being such to selectively provide a burst of the pulses; and a hollow-core photonic crystal fiber being operable to receive the modulated pump laser radiation and excite a working medium contained within the hollow-core photonic crystal fiber so as to generate supercontinuum radiation.

Abstract: Optical components and methods of manufacture thereof. A first optical component has a hollow-core photonic crystal fiber includes internal capillaries for guiding radiation and an outer capillary sheathing the internal capillaries; and at least an output end section having a larger inner cross-sectional dimension over at least a portion of the output end section than an inner cross-sectional dimension of the outer capillary along a central portion of the hollow-core photonic crystal fiber prior to the output end section. A second optical component includes a hollow-core photonic crystal fiber and a sleeve arrangement.