A device and a method for measuring thermal load caused by excited state absorption in laser gain crystal are disclosed. Thermal focal lengths on the tangential and sagittal planes of the laser gain crystal are obtained by obtaining the threshold when the pump power is decreased, the optimal operating point, and cavity parameters of the single-frequency laser. Individual ABCD matrices of the laser gain crystal on the tangential plane and the sagittal plane are obtained based on thermal focal length. The thermal load corresponding to the threshold when the pump power is decreased, the ESA thermal load corresponding to the threshold when the pump power is decreased, and the ESA thermal load at the optimal operating point are obtained

A device and a method for measuring a thermal load caused by energy transfer upconversion in a laser gain crystal. Increasing the pump power multiple times so that the power meter obtains multiple thresholds for a single-frequency laser; obtaining an average pump threshold of the output laser; obtaining cavity parameters of the single-frequency laser; obtaining thermal focal lengths on the tangential and sagittal planes of the laser gain crystal inside the single-frequency laser; obtaining individual ABCD matrices of the laser system on the tangential and the sagittal planes; obtaining a thermal load at the threshold based on the ABCD transfer matrix of the laser gain crystal on the tangential plane, the ABCD transfer matrix of the laser gain crystal on the sagittal plane, and the average pump threshold of the laser system; obtaining a thermal load caused by ETU at threshold based on the thermal load at the threshold.

Photonic chip includes an external cavity (EC) optical circuit to provide wavelength-selective optical feedback to a length of active optical fiber. Light generated in the active optical fiber may be coupled from the EC circuit to a light processing circuit of the photonic chip, such as an optical modulator or an optical mixer. The EC circuits may include single-frequency and multi-frequency optical filters, which may include ring resonators, dual-ring resonators, and optical modulators to support multi-frequency lasers. The EC circuits may further include pump combiners and optical isolators.

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.

A method of inducing light losses at a parasitic wavelength in a fiber laser system includes providing a wavelength discriminator (WD) spaced from and between feeding and process fibers or from the end output of the feeding fiber so as to induce losses of light at parasitic wavelength. The device implementing the disclosed method is configured with a laser source, the delivery fiber and WD spaced at a distance between the surface to be treated and the end of the delivery fiber, wherein the WD receives the parasitic light over free space and is configured as a dichroic filter inducing losses to the light at the parasitic wavelength.

The technology disclosed in this patent document allows mode locking of both selected longitudinal and transverse modes to produce laser pulses. The laser light produced based on such mode locking exhibits a 3-dimensional mode profile based on the locked longitudinal and transverse modes.

A method or apparatus for narrowing the linewidth of a single mode laser is provided. The linewidth of a single mode laser is narrowed by injecting an optical feedback simultaneously into the first laser cavity mirror and the second laser cavity mirror of the single mode laser.

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.

An optical assembly provides dispersion control, modelocking, spectral filtering, and/or the like in a laser cavity. For example, the optical assembly may comprise a diffraction grating pair arranged to temporally and spatially disperse a beam on a forward pass through the optical assembly, a reflective device at an end of the optical assembly, and a focusing optic arranged to create a beam waist at the reflective device. The beam waist created at the reflective device may cause the beam to be inverted on a reverse pass through the optical assembly, and a temporal dispersion and a spatial dispersion of the beam may be doubled on the reverse pass through the optical assembly to form a temporally and spatially dispersed output from the optical assembly.

A mode-locked solid state laser apparatus including an optical film, a gain medium crystal, a Fabry-Perot element, a first mirror, a second mirror, a third mirror and an output coupler is disclosed. The optical film is configured to receive a pumping light having a first wavelength incident in a first direction. The gain medium crystal receives the pumping light passing the optical film, and generates an initial laser beam having a second wavelength, wherein the initial laser beam forms a first optical path starting at one end thereof from the gain medium crystal. The Fabry-Perot element is disposed on the other end of the first optical path opposite to the one end, and reflects the initial laser beam along a second optical path having one end thereof starting from the Fabry-Perot element. The first mirror is disposed on the other end of the second optical path opposite to the one end of the second optical path, and reflects the initial laser beam along a third optical path having one end thereof starting from the first mirror.