A laser amplifier for a green laser pulse includes at least one gain medium doped with praseodymium and at least one gallium nitride based diode laser for pumping the gain medium. A green seed laser pulse going through the gain medium becomes an amplified green laser pulse.

Provided is a quantum sensor based on a rare-earth-ion doped optical crystal, having: a rare-earth-ion doped optical crystal; a low temperature providing unit, which provides a low temperature operating environment to the rare-earth-ion doped optical crystal; a constant magnetic field generation unit, which applies a constant magnetic field to the rare-earth-ion doped optical crystal; a light field generation unit, which provides a light field performing optical pumping on the rare-earth-ion doped optical crystal to prepare the rare-earth-ions in an initial spin state, and a light field for exciting Raman scattering of the rare-earth-ion doped optical crystal; a pulsed magnetic field generation unit, which applies a pulsed magnetic field perpendicular to the constant magnetic field to the rare-earth-ion doped optical crystal to make the rare-earth-ion doped optical crystal generate a spin echo; and a heterodyne Raman scattering light field detection and analysis unit, which detects and analyzes a Raman scattering light field radiated from the rare-earth-ion doped optical crystal. Further provided are uses of this quantum sensor for magnetic field sensing and electric field sensing as well as a sensing method.

A ring cavity laser source, a tunable ring cavity laser source and a method of fabricating a ring cavity laser source. The fiber ring cavity laser source comprises a fiber pigtailed pump laser; a fiber-based gain medium; a fiber-based circulator; a fiber-based coupler, wherein an input fiber port of the fiber-based coupler is coupled to a first end of the fiber-based gain medium, a first output fiber port of the fiber-based coupler is coupled to a first fiber port of the fiber-based circulator, and a second output fiber port of the fiber-based coupler is configured for extracting a laser output of the fiber ring cavity laser source; a fiber-based reflector coupled to a second fiber port of the fiber-based circulator; and a fiber-based combiner, wherein a first input fiber port of the fiber-based combiner is coupled to the fiber pigtailed pump laser, a second input fiber port of the fiber-based combiner is coupled to a third fiber port of the fiber-based circulator, and an output fiber port of the fiber-based combiner is coupled to a second end of the fiber-based gain medium; wherein the fiber-based reflector is configured for wavelength tuning of the laser output.

A multi-clad optical fiber design is described in order to provide low optical loss, a high numerical aperture (NA), and high optical gain for the fundamental propagating mode, the linearly polarized (LP) 01 mode in the UV and visible portion of the optical spectrum. The optical fiber design may contain dopants in order to simultaneously increase the optical gain in the core region while avoiding additional losses during the fiber fabrication process. The optical fiber design may incorporate rare-earth dopants for efficient lasing. Additionally, the modal characteristics of the propagating modes in the optical core promote highly efficient nonlinear mixing, providing for a high beam quality (M.sup.2<1.5) output of the emitted light.

A fiber laser apparatus includes: a short-length type fiber to which an active element is added and that has a length of 300 mm or less: a ferrule attached to an end of the fiber; and a housing that accommodates the fiber and supports the fiber with the ferrule. Each of the housing and the ferrule is composed of a material having a first thermal expansion coefficient that is equal to or have a predetermined difference from a second thermal expansion coefficient of a raw material of the fiber. The predetermined difference between the first and second thermal expansion coefficients is within −8.6×10.sup.−6 to 11.4×10.sup.−6/K.

A light-emitting device includes an optical fiber, a first light source unit, and a second light source unit. The optical fiber includes a wavelength converting portion. The wavelength converting portion is provided between a light incident portion and a light emerging portion. The wavelength converting portion contains a wavelength converting material. The wavelength converting material is excited by excitation light to produce a spontaneous emission of light having a longer wavelength than the excitation light and amplifies the spontaneous emission of light to produce an amplified spontaneous emission of light. The first light source unit makes the excitation light incident on the light incident portion. The second light source unit makes seed light, causing a stimulated emission of light to be produced from the wavelength converting material that has been excited by either the excitation light or the amplified spontaneous emission of light, incident on the light incident portion.

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 fiber laser apparatus includes: a short-length type fiber to which an active element is added and that has a length of 300 mm or less: a ferrule attached to an end of the fiber; and a housing that accommodates the fiber and supports the fiber with the ferrule. Each of the housing and the ferrule is composed of a material having a first thermal expansion coefficient that is equal to or have a predetermined difference from a second thermal expansion coefficient of a raw material of the fiber. The predetermined difference between the first and second thermal expansion coefficients is within −8.6×10.sup.−6 to 11.4×10.sup.−6/K.

A laser apparatus includes: a laser oscillator that includes a mirror and emits a laser beam; and an external resonator that includes a nonlinear optical crystal that functions as a phase conjugate mirror. The phase conjugate mirror reflects the laser beam and produces a phase conjugate wave that reaches the mirror of the laser oscillator, and the mirror of the laser oscillator and the phase conjugate mirror cause laser oscillation such that a wavelength and a phase of the laser beam oscillated by the laser oscillation are automatically fixed.

The present invention provides a way to use anisotropic laser gain media to make a laser that can lase in two longitudinal modes at different wavelengths with orthogonal polarizations. The two longitudinal mode (LM) laser output can be separated to generate two single LM outputs. This type of lasers can also be used to generate low noise continuous wave (CW) harmonics through intracavity harmonic generation.