Fiber-optic distributed sensing, employing the Brillouin effect, is already a commercially available measurement technique for the accurate estimation of the static strain/temperature fields along tens of kilometers with a spatial resolution of the order of a meter. Furthermore, relentless research efforts are paving the way to even much wider usability of the technique through recently achieved enhanced performance in each of its critical dimensions: measurement range has been extended to hundreds of kilometers; spatial resolution is of the order of a centimeter or less, signal to noise ratio has been significantly improved; fast dynamic events can be captured at kHz’s sampling rates; and a much better understanding of the underlying physics has been obtained, along with the formulation of figures of merit, and the preparation and early adoption of appropriate standards and guidelines. This paper describes the basics, as well as the state of the art, of the leading Brillouin interrogation methods, with emphasis on the significant progress made in the last 3 years. It also includes a short introduction to coding, which has proven instrumental in many of the recently obtained performance records.

[INVITED] State of the art of Brillouin fiber-optic distributed sensing

An EUV light source is disclosed that may include a laser source, eg CO2 laser, a plasma chamber, and a beam delivery system for passing a laser beam from the laser source into the plasma chamber Embodiments are disclosed which may include one or more of the following; a bypass line may be provided to establish fluid communication between the plasma chamber and the auxiliary chamber, a focusing optic, eg mirror, for focusing the laser beam to a focal spot in the plasma chamber, a steering optic for steering the laser beam focal spot in the plasma chamber, and an optical arrangement for adjusting focal power

Laser produced plasma euv light source

Embodiments described herein include a system for producing ultrashort tunable pulses based on ultra broadband OPA or OPG in nonlinear materials. The system parameters such as the nonlinear material, pump wavelengths, quasi-phase matching periods, and temperatures can be selected to utilize the intrinsic dispersion relations for such material to produce bandwidth limited or nearly bandwidth limited pulse compression. Compact high average power sources of short optical pulses tunable in the wavelength range of 1800 - 2100 nm and after frequency doubling in the wavelength range of 900 - 1050 nm can be used as a pump for the ultra broadband OPA or OPG. In certain embodiments, these short pump pulses are obtained from an Er fiber oscillator at about 1550 nm, amplified in Er fiber, Raman-shifted to 1800 - 2100 nm, stretched in a fiber stretcher, and amplified in Tm-doped fiber. To produce short pulses in the 900 - 1050 nm wavelength range, the pulses are frequency-doubled with a chirped frequency doubler for nearly bandwidth-limited output.

Optical parametric amplification, optical parametric generation, and optical pumping in optical fibers systems

We demonstrate the suppression of stimulated Raman scattering in a high power, single-mode Yb-doped fiber amplifier using a W-type core structure. Raman-scattered light is not guided by the core. The amplifier consists of a master oscillator power amplifier (MOPA) system, seeded with 103 ps pulses at 32 MHz repetition rate in the final amplification stage. An average output power of 53 W, which corresponds to 13 kW of peak power, was achieved in the 23 m long W-type double-clad fiber without any significant loss of power due to transfer from the signal wavelength at 1060 nm to the Raman Stokes wavelength at 1114 nm and amplified spontaneous emission from Yb-ions at longer wavelengths (~1070 nm). The power conversion efficiency at 1060 nm was 80% with respect to the absorbed pump power.

Suppression of stimulated Raman scattering in a high power Yb-doped fiber amplifier using a W-type core with fundamental mode cut-off.

An LPP EUV light source is disclosed having an optic positioned in the plasma chamber for reflecting EUV light generated therein and a laser input window For this aspect, the EUV light source may be configured to expose the optic to a gaseous etchant pressure for optic cleaning while the window is exposed to a lower gaseous etchant pressure to avoid window coating deterioration In another aspect, an EUV light source may comprise a target material positionable along a beam path to participate in a first interaction with light on the beam path; an optical amplifier; and at least one optic directing photons scattered from the first interaction into the optical amplifier to produce a laser beam on the beam path for a subsequent interaction with the target material to produce an EUV light emitting plasma

Drive laser delivery systems for euv light source

Laser apparatus and methods involving multiple amplified outputs are disclosed. A laser apparatus may include a master oscillator, a beam splitter coupled to the master oscillator, and two or more output heads optically coupled to the beam splitter. The beam splitter divides a signal from the master oscillator into two or more sub-signals. Each output head receives one of the two or more sub-signals. Each output head includes coupling optics optically coupled to the beam splitter. An optical power amplifier is optically coupled between the beam splitter and the coupling optics. Optical outputs from the two or more output heads do not spatially overlap at a target. The master oscillator signal may be pulsed so that optical outputs of the output heads are pulsed and substantially synchronous with each other.

Laser apparatus having multiple synchronous amplifiers tied to one master oscillator

Control of average wavelength-converted power and/or wavelength converted pulse energy is described. One or more seed pulses may be generated and amplified with an optical amplifier to produce one or more amplified pulses. The amplified pulses may be wavelength converted to produce one or more wavelength converted pulses characterized by an average wavelength-converted power or pulse energy. Wavelength-converted power or pulse energy may be controlled by adjusting wavelength conversion efficiency without substantially changing the amplified power or pulse energy. Average wavelength-converted power may be controlled over a time scale comparable to a pulse period of the amplified pulses without adjusting an average power of the amplified pulses over the time scale comparable to a pulse period of the amplified pulses. A wavelength-converted optical system, may comprise a seed source, an optical amplifier optically coupled to the seed source, a wavelength converter optically coupled to the optical amplifier; and a controller operably coupled to the seed source and/or optical amplifier and/or wavelength converter. The controller may include logic adapted to control an average wavelength-converted power of an output of the wavelength converter over a time scale comparable to a pulse period of amplified pulses from the optical amplifier without adjusting an average power of the amplified pulses over that time scale. Alternatively, the controller logic may be adapted to control wavelength-converted pulse energy by adjusting the wavelength conversion efficiency without substantially changing the pulse energy of the amplified pulses.

Light source with precisely controlled wavelength-converted average power

Methods and apparatus for reducing a thermal load on an optical head are described. Waste light is captured at one or more locations in the optical head and directed to a location that is thermally isolated from the one or more locations in the optical head using or more optical fibers.

Reducing thermal load on optical head

We derive analytic expressions for the Brillouin thresholds of square pulses in optical fibers. The equations are valid for pulse durations in the transient Brillouin scattering regime (less than 100 nsec), as well for longer pulses, and have been confirmed experimentally. Our analysis also gives a firm theoretical prediction that the Brillouin gain width increases dramatically for intense pulses, from tens of MHz to one GHz or more.

Stimulated Brillouin scattering of pulses in optical fibers.

A cladding-pumped Nd:silica fiber with a fundamental-mode cut-off near 1000 nm was used to build an amplifier with gain over a range near 920 nm. Pulses from an Nd:YVO4 passively Q-switched laser were amplified and then frequency doubled in LBO to produce blue with 3-W average power.

Mark W. Byer

Papers

Laser apparatus having multiple synchronous amplifiers tied to one master oscillator

Light source with precisely controlled wavelength-converted average power

Reducing thermal load on optical head

Stimulated Brillouin scattering of pulses in optical fibers.

3-Watt blue source based on 914-nm Nd:YVO4 passively-Q-switched laser amplified in cladding-pumped Nd:fiber