A laser system includes a resonant laser cavity configured to output a laser signal. The system also includes a utility waveguide configured to receive the laser signal from the laser cavity. The utility waveguide includes a perturbation region that is external to the laser cavity and receives the laser signal from the laser cavity and outputs a laser beam. The perturbation region includes one or more perturbation structures that each causes one or more perturbation(s) in the index of refraction of the utility waveguide. The perturbation structures are selected to provide optical feedback to the resonant laser cavity such that a power versus wavelength distribution in the laser beam is different from the power versus wavelength distribution that would be in the laser signal in the absence of the perturbation structures.

A method includes driving, while producing a burst of pulses at a pulse repetition rate, a spectral feature adjuster among a set of discrete states at a frequency correlated with the pulse repetition rate; and in between the production of the bursts of pulses (while no pulses are being produced), driving the spectral feature adjuster according to a driving signal defined by a set of parameters. Each discrete state corresponds to a discrete value of a spectral feature. The method includes ensuring that the spectral feature adjuster is in one of the discrete states that corresponds to a discrete value of the spectral feature of the amplified light beam when a pulse in the next burst is produced by adjusting one or more of: an instruction to the lithography exposure apparatus, the driving signal to the spectral feature adjuster, and/or the instruction to the optical source.

An optical filter includes a first ring resonator a second ring resonator having different perimeters, and a waveguide optically coupled to the first ring resonator and transmit light to the first ring resonator. Light incident on the waveguide is transmitted to the second ring resonator through the first ring resonator. A free spectral range of a transmission spectrum of the first ring resonator and a free spectral range of a transmission spectrum of the second ring resonator are staggered to each other, and are set so that a transmission spectrum of a double ring corresponding to a synthetic spectrum of the transmission spectrum of the first ring resonator and the transmission spectrum of the second ring resonator has a highest first peak at an arbitrary wavelength.

Multi-clad optical fiber cladding light stripper (CLS) comprising an inner cladding with one or more recessed surface regions to remove light propagating within the inner cladding. A CLS may comprise such recessed surface regions along two or more azimuthal angles about the fiber axis, for example to improve stripping efficiency. One or more dimensions, or spatial distribution, of the recessed surface regions may be randomized, for example to improve stripping uniformity across a multiplicity of modes propagating within a cladding. Adjacent recessed surface regions may abut, for example, end-to-end, as segments of a recess that occupies a majority, or even an entirety, of the length of a fiber surrounded by a heat sink. One or more dimensions, or angular position, of individual ones of the abutted recessed surface regions may vary, according to a regular or irregular pattern.

To provide a mode-locked pulse photoproduction filter for easily realizing self-starting mode-locking, and a laser device for generating a picosecond or femtosecond-pulse laser light by including such filter, the laser device including an amplifying unit for amplifying and outputting a light inside a resonator, and the mode-locked pulse photoproduction filter having a first filter part for selectively outputting a first wavelength component that is a wavelength component of an oscillation band inside the resonator, and a second filter part for selectively outputting a second wavelength component that is a wavelength component different from the oscillation band inside the resonator.

An electrically tunable non-reciprocal phase shifter, an electrically tunable polarization filter, a NALM mode-locked laser and a Sagnac loop are provided. The electrically tunable non-reciprocal phase shifter includes a modulation crystal device, a birefringent crystal device, a Faraday rotator, and a fiber coupler. The phase shifter is configured to couple two beams of light to a fast axis and a slow axis of the modulation crystal device, respectively; and change a refractive index difference between the fast axis and the slow axis to introduce different phase delays for the two beams of the light, so as to control a non-reciprocal linear phase shift amount between the two beams of the light.

It is an aim of the present invention to provide ultra-compact highly-integrated diffraction-grating semiconductor lasers on chips. Various embodiments combined enable the lasers to be compact in size, light weight, mechanically rugged, low in manufacturing cost, and in some cases high in electrical wall-plugged power efficiency or high in optical power output, comparing to typical lasers based on discrete optical components.

A steerable laser transmitter and active situational awareness sensor that achieves SWaP-C, steering rate and spectral diversity improvements by scanning a beam with a Micro-Electro-Mechanical System (MEMS) Micro-Minor Array (MMA). One or more sections of non-linear material (NLM) positioned in the optical path (e.g. as annular sections around a conic mirror or as reflective optical coatings on the MMA) are used to convert the wavelength of the beam to a different wavelength while preserving the steering of the beam. The MEMS MMA may include piston actuation of the mirrors to shape the spot-beam.

The present invention benefits from the determination that pre-selected spectral bandwidths that avoid the spectrum of an electronic transition of a metal/alloy vapor allow for welds substantially free from detritus that may discolor the weld. Accordingly, the present invention provides analytical methods, welding methods and fiber lasers configured to provide high quality metal/alloy welds.

A photonic integrated circuit (PIC) assembly comprising a semiconductor optical amplifier (SOA) array and a U-turn chip. The SOA array includes an input SOA and a plurality of SOAs. The input SOA and the plurality of SOAs are arranged parallel to one another. The U-turn chip includes an optical splitter and a waveguide assembly. The optical splitter is configured to receive amplified input light propagating in a first direction from the input SOA, and divide the amplified light into beams. The waveguide assembly guides the beams to a corresponding SOA of the plurality of SOAs, and adjusts a direction of prorogation of each of the guided beams to be substantially parallel to a second direction that is substantially opposite the first direction.