External cavity laser systems are described that can operate with essentially no mode hopping. One example configuration of the laser system includes a semiconductor laser device, a folded cavity external to the semiconductor laser device, where at the semiconductor laser device is positioned at a fold in the folded cavity. In this configuration, at least one mirror is positioned in the folded cavity to enable sustained propagation of light within the folded cavity, and at least two polarization elements are positioned in the folded external cavity. The polarization elements cause a polarization state of the light that impinges in different directions on each semiconductor laser device that is positioned at a fold to be orthogonal to one another, thus eliminating or substantially reducing mode hopping in the laser output.

A collinear T-cavity VECSEL system generating intracavity Hermite-Gaussian modes at multiple wavelengths, configured to vary each of these wavelengths individually and independently. A mode converter element and/or an astigmatic mode converter is/are aligned intracavity to reversibly convert the Gaussian modes to HG modes to Laguerre-Gaussian modes, the latter forming the system output having any of the wavelengths provided by the spectrum resulting from nonlinear frequency-mixing intracavity (including generation of UV, visible, mid-IR light). The laser system delivers Watt-level output power in tunable high-order transverse mode distribution.

This invention is a broadband intra cavity laser mode convertor. This is a hologram of a complex phase mask imprinted inside of a volume Bragg grating with wide spectral width recorded in photo-thermo-refractive (PTR) glass. This hologram is a broadband phase converting monolithic device capable of use over a broad wavelength range at high instant and average power because of low absorption coefficient and low nonlinear refractive index of PTR glass. Therefore, it can be used for broadband optical beam transformations and conversion of modes in laser resonators.

The present invention relates to a diode laser with external spectrally selective feedback. It is an object of the invention is to provide an external cavity diode laser with wavelength stabilization which allows an increased overall output power in the desired wavelength range. According to the invention, an external cavity diode laser arrangement is disclosed comprising: an active medium positioned inside an internal laser cavity (10), the internal laser cavity (10) comprising an exit facet (12) adapted for outcoupling laser radiation; an external frequency-selective element (14) positioned outside the internal laser cavity (10) and adapted for wavelength stabilization of the laser radiation; a beam divider (16) positioned outside the internal laser cavity (10) and adapted to divide the outcoupled laser radiation (BO) into a first beam (B1) extending along a first beam path (P1) and a second beam (B2) extending along a second beam path (P2), the first beam (B1) having higher radiant intensity than the second beam (B2) and the first beam path (P1) being different from the second beam path (P2); and an intensity control means to control the radiant intensity incident to the external frequency selective element (14); wherein the external frequency-selective element (14) and the intensity control means are arranged in the second beam path (P2). The intensity control means in the second beam path (P2) may comprise a polarization modifying means (18) and a polarizer (20) in order to reduce thermal stress at the frequency-selective element (14).

A laser apparatus including a pulsed laser radiation source is disclosed, wherein the laser radiation has spectral components in at least two wavelength ranges W1, W2 that differ from one another, and a dispersion control element including at least one dielectric multilayer mirror, wherein the laser radiation is reflected one or more times at the multilayer mirror. The multilayer mirror is reflective in the two wavelength ranges W1, W2, and the reflection of the spectral component in the second wavelength range W2 has a time delay relative to the reflection of the spectral component in the first wavelength range W1 such that the spectral components of the laser radiation reflected at the multilayer mirror in the two wavelength ranges W1, W2 coincide in time in an interaction center of the laser apparatus, and a nonlinear optical element is situated in the interaction center.

The present disclosure provides an optical sub-system for a passive, mode-locked laser optical system. The optical sub-system may include a graphene-based saturable absorber and an optical device configured to control dispersion properties of the laser optical system. The graphene-based saturable absorber may be supported by the optical device.

To prevent an output decrease of laser light due to impurities that could be formed in a guide-light emitting device or an imaging device. A laser-light guiding section includes a transmission window section, an optical component disposed to cause an optical path of the UV laser light emitted from the laser-light output section and an optical path of transmitted light transmitted through the transmission window section to cross, and a sealing member in which the transmission window section is provided, the sealing member configuring a sealed space for airtightly housing the optical component. At least one of a guide-light emitting device configured to emit guide light for visualizing a scanning position of the UV laser light toward the transmission window section and an imaging device configured to receive light for imaging a workpiece via the transmission window section is disposed on the outer side of the sealed space.

To appropriately change an output of laser light without deteriorating laser characteristics. A control section of a laser machining device controls, when a target output is larger than a predetermined threshold, an output of laser light by changing a driving current supplied to an excitation light source and, on the other hand, controls, when the target output is equal to or smaller than the threshold, the output of the laser light by changing a duty ratio of a Q switch while keeping the driving current supplied to the excitation light source substantially fixed.

To prevent an output decrease of laser light due to impurities formed in a Q switch. A laser machining device includes a Q-switch housing section configured by housing a Q switch and a first mirror and a wavelength converting section including a housing in which a transmission window section capable of transmitting a fundamental wave is formed, the wavelength converting section being configured by airtightly housing, with an internal space surrounded by the housing, at least a first wavelength conversion element, a second wavelength conversion element, and a second mirror. A resonator forming a resonant optical path passing through the transmission window section is configured by the first mirror in the Q-switch housing section and the second mirror in the wavelength converting section.

A frequency-doubled laser, including: a first reflecting mirror, a second reflecting mirror, a gain medium, a telescope module, a polarizing element, and a nonlinear crystal; the first reflecting mirror and the second reflecting mirror are spaced apart to form a resonator of the frequency-doubled laser; the polarizing element, the gain medium, the telescope module, and the nonlinear crystal are located in the resonator, and the telescope module is located between the gain medium and the nonlinear crystal. The present disclosure further provides a method of generating harmonic laser. The frequency-doubled laser and the method of generating harmonic laser make the position of nonlinear crystal more flexible, and the possibility of damage to the nonlinear crystal is reduced.