A laser system involving coupled distributed resonators disposed serially, with the lasing gain medium located in the main resonator and the output of that resonator being directed into a free space resonator, such that the main resonator output mirror is effectively the free space resonator. The distributed resonators end mirrors are retroreflectors. Interference occurs between light traveling towards the remote mirror of the free space resonator and light reflected therefrom, generating regions of high reflectivity. The coupling of the free space resonator to the regions of high reflectivity of the free space resonator enables the first resonator to lase efficiently, even though the true reflectivity of the main resonator output mirror outside of those regions is insufficient to enable efficient lasing, if at all. This coupled resonator structure enables lasing to occur with a high field of view and the high gain engendered by the high reflectivity regions.

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 laser device includes a gain medium, a zero-degree reflective mirror, a first retro-reflective mirror, a second retro-reflective mirror, and an output coupling mirror. The gain medium is used to generate radiation light; the zero-degree reflective mirror has a common optical axis with the gain medium, and the zero-degree reflective mirror is used to totally reflect second-direction radiation light that is incident on the zero-degree reflective mirror in an optical-axis direction; the first-direction radiation light and the first emitted light are spaced from and parallel to each other in opposite directions; the first emitted light and the second emitted light are spaced from and parallel to each other in opposite directions; a resonant cavity is formed between the zero-degree reflective mirror and the output coupling mirror; the output coupling mirror is used to transmit and output first partial radiation light, and reflect second partial radiation light.

Apparatus, systems and methods to spectrally beam combine a group of diode lasers in an external cavity arrangement. A dichroic beam combiner or volume Bragg grating beam combiner is placed in an external cavity to force each of the diode lasers or groups of diode lasers to oscillate at a wavelength determined by the passband of the beam combiner. In embodiments the combination of a large number of laser diodes in a sufficiently narrow bandwidth to produce a high brightness laser source that has many applications including as to pump a Raman laser or Raman amplifier.

A laser system involving coupled distributed resonators disposed serially, with the lasing gain medium located in the main resonator and the output of that resonator being directed into a free space resonator, such that the main resonator output mirror is effectively the free space resonator. The distributed resonators end mirrors are retroreflectors. Interference occurs between light traveling towards the remote mirror of the free space resonator and light reflected therefrom, generating regions of high reflectivity. The coupling of the free space resonator to the regions of high reflectivity of the free space resonator enables the first resonator to lase efficiently, even though the true reflectivity of the main resonator output mirror outside of those regions is insufficient to enable efficient lasing, if at all. This coupled resonator structure enables lasing to occur with a high field of view and the high gain engendered by the high reflectivity regions.

A single loop hardware-based system for producing laser pulses in a microsecond scale operational mode includes a GUI to enable a user to select the operational mode of the system; a laser source for producing one or more laser beam pulses, the laser source being a diode laser pump source module; a DSP which enables and disables a hardware-based FPGA. The FPGA controls the diode pump source module. When a user selects one or more microsecond scale laser sub-pulses on the GUI, the DSP transmits to the FPGA the sub-pulse energy level and the sub-pulse on-time selected by the user on the GUI. A photodetector operatively connected to the hardware-based system measures the power of the laser pulse beam that was transmitted to the photodetector and, in a feedback mode, transmits a feedback signal of that power measurement to the FPGA. The FPGA compares the power of the laser beam measured by the photodetector to the power of the laser beam selected by the user on the GUI. If the power level read by the FPGA is higher than the selected power level, the FGPA decreases the power level to the pumping source module for any subsequent laser pulses; and if the power level read by the FPGA is less than the selected power level, the FGPA increases the power level to the pumping source module for subsequent laser pulses.

A spectral beam combining system includes a plurality of input fibers and a prism having a curved input surface. The plurality of input fibers are attached to the curved input surface. The spectral beam combining system also includes an immersion grating defined on a second surface of the prism, a protective cap disposed over the immersion grating, and an output surface.

An external optical feedback element (108) for tuning an output beam of a gas laser (102) having multiple wavelengths includes a partially reflective optical element (108) positioned on a beam path of the output beam (106) outside of an internal optical cavity of the gas laser (102), and a stage (114) to support the optical element and adjust rotation, horizontal tilt angle, and vertical tilt angle of the optical element with respect to the beam path. The output beam (106) is partially reflected at the optical element (108) and fed back into the internal optical cavity of the gas laser (102), with the intensity varying for multiple wavelengths and adjusted by changing rotation, horizontal tilt angle and vertical tilt angle of the optical element. Thereby, a variable feedback of the output beam into the internal optical cavity of the gas laser is provided, which leads to a selective output wavelength of the gas laser, either at a single line or at multiple lines simultaneously. This setup may allow to control the wavelength of a commercial CO2 gas laser without a modification of the laser itself by adding a coupled cavity with a wavelength selective element like a grating to the given gas laser resonator.

In a Q-switched solid-state laser having a resonator (3, 30) in the form of a linear resonator or a ring resonator having an active laser material (1) and at least one first and one second mirror (4, 5) and a resonator length (a) of less than 50 mm, preferably less than 25 mm, in the case of the configuration as a linear resonator and of less than 100 mm, preferably less than 50 mm, in the case of the configuration as a ring resonator, at least substantially only one longitudinal mode oscillates in the resonator (3). The resonator (3, 30) is in the form of an unstable resonator, with one of the mirrors (4, 5) being a gradient mirror.

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.