Provided is a single-crystal fiber including a waveguide structure for a wavelength to be subjected to optical amplification, in which at least one end of the single-crystal fiber is planar, an angle θ between a normal to a facet of the single-crystal fiber and an optical axis of the single-crystal fiber satisfies a relationship of θ=90°−tan.sup.−1(n.sub.2/n.sub.1), where n.sub.1 represents a refractive index of a medium of a space that uses the single-crystal fiber, and n.sub.2 represents a refractive index of the single-crystal fiber for a guided light beam having a polarization direction parallel with a plane that includes the normal to the facet and the optical axis, and a diameter Dx in an X-direction and a diameter Dy in a Y-direction of a cross-section of the single-crystal fiber perpendicular to the optical axis satisfies a relationship of (n.sub.2/n.sub.1)0.9≤Dx/Dy≤(n.sub.2/n.sub.1)1.1.

An electrodeless laser-driven light source includes a laser source that generates CW sustaining light. A pump laser generates pump light. A Q-switched laser crystal is positioned to receive the pump light and generates pulsed laser light in response to the generated pump light that propagates to a breakdown region in a gas filled bulb comprising an ionizing gas. A detector detects plasma light generated by a CW plasma located at least partly in a CW plasma region in the gas filled bulb comprising the ionizing gas and generates a detection signal. A controller generates control signals that control the pump light to the Q-switched laser crystal so as to extinguish the pulsed laser light within a time delay after the detection signal exceeds a threshold level.

An optical amplifier comprises a gain medium having an input surface and an output surface wherein the output surface is larger than the input surface. The gain medium may be frustum shaped. The optical amplifier includes a negative diverging lens to receive an extraction laser beam and to cause the laser beam to expand as the beam passes through the gain medium. The amplifier further comprises a positive collimating lens configured to receive the expanding amplified beam and reduce the divergence. The gain medium can be pumped by counter-propagating radiation. The fluence of the laser beam within the gain medium is configured to be near constant along the length of the gain medium and may be within 1.5-2.0 F.sub.SAT. The gain medium may be doped with dopant to provide gain, with larger concentration of dopants proximal the input surface and smaller concentration proximal the output surface.

The invention includes a device for amplifying light having a pumping resonator and a Raman resonator that share an output mirror and are divided by an interior mirror. A pumping beam is directed though a gain medium in each resonator. A seed signal is directed into the Raman resonator, which is configured to contain cascaded Raman-shifted signals generated through the interaction of the pumping beam, seed signal, and gain medium, and to transmit a selected Raman-shifted signal as optical output. Also disclosed is a method of amplifying light using a Raman resonator that partially overlaps a pump resonator. A pumping beam is directed through a pump gain medium and a Raman gain medium and generates cascading Raman-shifted signals within the Raman resonator. A seed signal is used to shape the temporal profile, and improve the coherence, of the Raman-shifted signals.

Methods, systems and apparatus are disclosed for delivery of pulsed treatment radiation by employing a pump radiation source generating picosecond pulses at a first wavelength, and a frequency-shifting resonator having a lasing medium and resonant cavity configured to receive the picosecond pulses from the pump source at the first wavelength and to emit radiation at a second wavelength in response thereto, wherein the resonant cavity of the frequency-shifting resonator has a round trip time shorter than the duration of the picosecond pulses generated by the pump radiation source. Methods, systems and apparatus are also disclosed for providing beam uniformity and a sub-harmonic resonator.

One or more embodiments relates to a method of growing ultrasmooth and high quantum efficiency CsTe photocathodes. The method includes exposing a substrate of Cs using an alkali source such as an effusion cell; and controlling co-evaporating growth and co-deposition forming a CsTe growth. The method further includes monitoring a stoichiometry of the CsTe growth.

A lidar system comprises (1) an array of pixels for sensing incident light and (2) a circuit for processing a signal representative of the sensed incident light to detect a reflection of a laser pulse from a target within a field of view. The circuit can comprise a plurality of matched filters that are tuned to different reflected pulse shapes for detecting pulse reflections within the incident light, and wherein the circuit (1) applies the signal to the matched filters to determine an obliquity for the target based how the matched filters respond to the applied signal and (2) determines a correction angle based on the determined target obliquity, the correction angle for orienting the field of view to a frame of reference in response to a tilting of the lidar system. In an example embodiment, the circuit can comprise a signal processing circuit that performs the signal application and correction angle determination operations. In another example embodiment, the circuit can comprise (1) a signal processing circuit that performs the signal application operation and (2) a receiver controller circuit that performs the correction angle determination operation.

Methods, systems and apparatus are disclosed for delivery of pulsed treatment radiation by employing a pump radiation source generating picosecond pulses at a first wavelength, and a frequency-shifting resonator having a losing medium and resonant cavity configured to receive the picosecond pulses from the pump source at the first wavelength and to emit radiation at a second wavelength in response thereto, wherein the resonant cavity of the frequency-shifting resonator has a round trip time shorter than the duration of the picosecond pulses generated by the pump radiation source. Methods, systems and apparatus are also disclosed for providing beam uniformity and a sub-harmonic resonator.

A planar waveguide amplifier includes a planar waveguide including a flat plate-like core; a first cladding provided on a first principal face of the core; and a second cladding provided on a second principal face of the core, and signal light and pumping light travel into the planar waveguide so that the signal light and the pumping light propagate inside the core in such a manner that optical paths of the signal light and the pumping light overlap each other, and in a zig-zag manner, and the core is an amplification medium containing a rare-earth element serving as an active ion of a three-level system, and absorbs the signal light on the basis of a reduction in intensity of the pumping light.

A broadband source device configured for generating broadband radiation or white light output. The broadband source device includes a gas cell, and a hollow-core photonic crystal fiber at least partially enclosed within the gas cell. A gas mixture is within the gas cell and the hollow-core photonic crystal fiber. The gas mixture includes at least one Raman active molecular gas constituting more than 2% of the gas mixture, such that the broadband source device operates in a balanced Kerr-Raman nonlinear interaction regime.