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.

A device for combining at least two input laser beams having different spectral components. At least one pre-compensation unit for the at least two input laser beams has a diffractive optical unit which expands the input laser beam into an intermediate beam bundle in which the spectral components are spatially arranged so as to be adjacent to one another with increasing wavelength. A combination unit has at least a first diffractive optical element and a second diffractive optical element, the combination unit being aligned with the pre-compensation unit in such a way that the first diffractive optical element converts an intermediate beam bundle into a convergent beam bundle having a beam waist, the beam waist lying on the second diffractive element, and the second diffractive optical element being designed in this way that all incident spectral components are diffracted in a common radiation direction.

In accordance with various embodiments, a multi-wavelength beam output is formed by stabilizing beams each to a unique wavelength with a stabilizing dispersive element, which reflects a portion of the beam back to its emitter to stabilize the beam and transmits the stabilized beam. The stabilized beams are then transmitted to a combining dispersive element that combines the stabilized beams into the multi-wavelength beam output.

A laser system connectable to an exposure apparatus includes a spectrometer configured to acquire a measurement waveform from an interference pattern of laser light output from the laser system, and a processor configured to calculate a convolution spectrum waveform using the measurement waveform and a first intermediate function obtained through a process of deconvolution of an aerial image function of the exposure apparatus with an instrument function of the spectrometer.

Example embodiments relate to lasers that include loop resonators. One example laser includes a loop resonator forming a closed loop light path. The loop resonator includes an optical gain medium configured to lase. The loop resonator is configured to, during lasing, present a pair of modes: a mode of light propagating in a clockwise direction in the closed loop light path of the loop resonator (termed CW mode) and a mode of light propagating in a counter-clockwise direction in the closed loop light path of the loop resonator (termed CCW mode). The laser also includes a first light output configured to output laser light from the laser. Additionally, the laser includes an optical power modulating unit. The optical power modulation unit is configured to modulate an optical power of the CW mode of the loop resonator and an optical power of the CCW mode of the loop resonator.

A radiation field generating system comprising an optical unit with an optical assembly which defines an optical path is provided, wherein the optical unit is operable in several different operation conditions and the optical assembly comprises at least one optical switching component with which switching between at least two different operation conditions of the several operation conditions can be performed.

Disclosed is a multimode interference effect-based wide tunable single-frequency optical fiber laser device. The laser device comprises a high-reflectivity chirped optical fiber grating, a high-gain optical fiber, a low-reflectivity chirped optical fiber grating, a pump source, an optical circulator, an optical fiber etalon and an SMS optical fiber structure apparatus. The high-reflectivity chirped optical fiber grating, the high-gain optical fiber and the low-reflectivity chirped optical fiber grating are connected in sequence to form a short linear resonant cavity; the optical circulator, the optical fiber etalon and the SMS optical fiber structure apparatus form a ring cavity, a stress loader is fixed onto the SMS optical fiber structure apparatus, and a transmitting wavelength of the SMS optical fiber structure apparatus is changed and tunable filtering by the SMS optical fiber structure apparatus is realized by loading stress to the SMS optical fiber structure apparatus.

A continuous optical beat laser element for generating terahertz (THz) waves and a laser source using same includes periodically poled lithium niobate (ppLN) crystals arranged along a predetermined direction forming a surface generally parallel to the predetermined direction. A Ti diffused region is applied on the surface and an array of gold nanowires are applied on the Ti diffused region to form a gold metal-insulator-metal (MIM) element that optimizes coupling and channeling of THz radiation from the crystals into the gold nanowires. The system provides a simple, stable, compact and cost-effective THz source using a widely tunable C-band SOA-based laser to excite a non-linear photo-mixer to produce terahertz radiation that ranges from 0.8 to 2.51 THz at room temperature. This laser source can be modified into an all fiber-based THz generator by embedding ppLN crystals in a fiber filament configuration resulting in less absorption and producing high output power.

A wavelength tunable laser includes a filter region having a wavelength selection function on light from a gain region, wherein the filter region is a Sagnac interferometer and includes two ring resonators. The ring resonator has two optical couplers, and first and second curved waveguides connecting the two optical couplers, each of the two optical couplers is configured to receive input of the light from the gain region through an input-output port, to couple light of a resonant peak to a bar port of the input-output port, and to couple light except light at a resonant peak wavelength to a cross port of the input-output port, and each of radiation waveguides connected to the cross ports of the input-output ports of the two optical couplers has a structure that radiates the light except the light at the resonant peak wavelength to a front surface or a back surface of a substrate.

A fiber laser producing a beam of ultrashort laser pulses at a repetition rate greater than 200 MHz includes a linear fiber resonator and a fiber branch. Ultrashort laser pulses are generated by passive mode-locking and circulate within the linear fiber resonator. Each circulating laser pulse is split into a portion that continues propagating in the linear fiber resonator and a complementary portion that propagates through the fiber branch and is then returned to the linear fiber resonator. The optical length of the linear fiber resonator is an integer multiple of the optical length of the fiber branch. The repetition rate of the ultrashort laser pulses is the reciprocal of the propagation time of the laser pulses through the fiber branch.