Some implementations described herein provide a laser device. The laser device includes a first portion of the laser device, at a proximal end of the laser device, that includes one or more optical devices, where the first portion is configured to emit first electromagnetic waves having a first wavelength. The laser device includes a second portion of the laser device, at a distal end of the laser device, that includes an optical crystal configured to receive the first electromagnetic waves and to emit second electromagnetic waves having a second wavelength based on reception of the first electromagnetic waves, where the optical crystal includes a thin film coating disposed on an end of the optical crystal, the thin film coating configured to: support emission of the second electromagnetic waves from the optical crystal, and support internal reflection of the first electromagnetic waves within the optical crystal.

Systems, apparatuses, and methods are provided for dual-pass amplification of laser beams along a common beam path. An example method can include generating a first laser beam and a second laser beam. Subsequently, the example method can include performing dual-pass amplification of the first laser beam and the second laser beam along a common beam path. In some aspects, the first laser beam can include a first wavelength, the second laser beam can include a second wavelength different from the first wavelength.

Various example embodiments relate to active optical fibers and devices comprising active optical fibers. A section of an active optical fiber may comprise an active core doped with at least one rare-earth element. The active core may have a first refractive index and be configured to support a single mode operation of an optical signal. The section of the active optical fiber may further comprise at least one cladding layer having a second refractive index. The second refractive index may be less than the first refractive index. Birefringence of the active core may be less than 10.sup.-5. Fiber lasers and power amplifiers comprising the section of the active optical fiber are also disclosed.

A method using femtosecond laser for nano precision preparation. Initial damage nanoholes formed by using femtosecond laser multiphoton excitation are used as a seed structure, and the energy and polarization state of subsequent laser pulses are adjusted in real time, such that uniform and directional optical near-field enhancement is generated near the seed structure and finally the high-precision removal of machined materials is realized. Benefiting from the high localization of near-field spot energy in space, the method uses femtosecond laser pulses having the wavelength of 800 nm to achieve a machining accuracy having the minimum linewidth of only 18 nm, and the linewidth resolution reaches 1/40 of the wavelength; and the method using femtosecond laser for nano precision preparation does not need a vacuum environment, having good air/solution machining compatibility.

A short-pulse, narrowband, line-selectable and tunable solid-state laser is described. The device requires a pump source, an active solid-state laser medium, an enclosing cavity, mirrors to contain the light, a method of removing the pulse from the cavity, a wavelength selection system, and a laser linewidth narrowing system. One implementation of this is an Er:YAG laser, side pumped by semiconductor lasers in the erbium absorption band near 1475 nm, with an intracavity etalon and a switchable spectral filter. To remove the pulse from the cavity, cavity dumping issues, which assures constant pulse energy and pulse length over a range of repetition rates, in this case from 100 Hz to 20 kHz. Line selection is obtained by use of wavelength filters and fine tuning with an etalon, which also acts as the linewidth narrowing system.

Additive manufacturing devices and methods for the same are provided. The additive manufacturing device may include a stage configured to support a substrate, a printhead disposed above the stage, and a targeted heating system disposed proximal the printhead. The printhead may be configured to heat a build material to a molten build material and deposit the molten build material on the substrate in the form of droplets to fabricate the article. The targeted heating system may be configured to control a temperature or temperature gradient of the droplets deposited on the substrate, an area proximal the substrate, or combinations thereof.

Systems and apparatuses for a polarization laser sensor are disclosed. The polarization laser sensor can include a pump source, a common section, a reference section and a detection section. The common section is provided with a gain medium, and the detection section is provided with a sensing element configured to cause an optical path difference. The reference section and the detection section are connected to the common section though a first polarization splitting unit and a second polarization splitting unit. The common section is provided with an output unit or each of the reference section and the detection is provided with the output unit, the output unit is connected to a photoelectric detector through a light uniting unit, and a polarization rotation unit is disposed between the light uniting unit and the output unit.

A hybrid optical amplifier is proposed that includes a preamplifier element formed of single-clad Ho-doped optical fiber and a power amplifier element formed of single-clad Tm-doped (or Tm—Ho co-doped) optical fiber. The preamplifier is used to impart gain to an input signal propagating at a wavelength λ.sub.S in the presence of a first pump beam operating at λ.sub.P1, creating an amplified output over a defined transmission bandwidth. The power amplifier element is disposed at the output of the preamplifier element and provides an additional level of gain to the output of the preamplifier element in the presence of a second pump beam operating at λ.sub.P2. A passband filter may be used between the preamplifier and the power amplifier to ensure that only wavelength components within the defined transmission bandwidth are applied as an output to the power amplifier.

An apparatus for emitting pulsed electromagnetic laser radiation includes a laser gain element; an optical arrangement defining a laser resonator and arranged to re-direct radiation emitted by the gain element along a beam path back onto the gain element, the optical arrangement comprising an output coupler configured to couple a portion of the radiation in the laser resonator out of the laser resonator; and, a pump arrangement configured to pump the laser gain element. The optical arrangement includes a mode locker placed in the laser resonator in the beam path, and a birefringent element placed in the laser resonator in the beam path.

A device may include a first photodetector to generate a first current based on an optical power of an optical beam. The device may include a beam splitter to split a portion of the optical beam into a first beam and a second beam. The device may include a wavelength filter to filter the first beam and the second beam. The wavelength filter may filter the second beam differently than the first beam based on a difference between an optical path length of the first beam and an optical path length of the second beam through the wavelength filter. The device may include second and third photodetectors to respectively receive, after the wavelength filter, the first beam and the second beam and to generate respective second currents.