A mid-infrared semiconductor saturable absorber mirror based on InAs/GaSb superlattice comprises a GaSb substrate with an anti-reflection film coated on the lower surface of the GaSb substrate; InAs/GaSb superlattice which has a specific structure and thickness and is arranged on the GaSb substrate; and Bragg reflection film which is arranged on the InAs/GaSb superlattice, wherein Bragg reflection film is composed of multiple pairs of ZnS and YbF.sub.3 film layers with a thickness of ¼ wavelength, and the YbF.sub.3 film layer is connected with the InAs/GaSb superlattice. The device not only has a mid-infrared working range with a broadband operation bandwidth, but also has the advantages of designable parameters, outstanding robustness, high damage threshold and the like, and sets a foundation for the development of mid-infrared ultrafast mode-locked lasers.

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.

An optical oscillator includes a first reflection part configured to reflect light of a first wavelength, a laser medium excited by excitation light of a second wavelength different from the first wavelength and configured to emit light of the first wavelength, a second reflection part configured to form an unstable resonator together with the first reflection part, the unstable resonator being configured to output annular laser light of the first wavelength, and a saturable absorption part disposed between the laser medium and the second reflection part and of which a transmittance increases with absorption of light of the first wavelength. When a power of the excitation light is indicated by P.sub.p (kW), and an inner diameter of the annular laser light is indicated by d.sub.i, and an outer diameter is indicated by d.sub.o, and d.sub.o/d.sub.i is a magnification m, the magnification m satisfies a.sub.0+a.sub.1 Log(P.sub.p)≤m≤b.sub.0+b.sub.1P.sub.p+b.sub.2P.sub.p.sup.2.

A distributed gain polygon ring laser system includes a substrate ring, top and bottom cover plates, an input pump laser, an output coupler and a number of reflection points. The substrate ring has inner and outer surfaces. The top and bottom cover plates are configured for vacuum sealing with the substrate ring. The input pump laser is configured to direct light into the substrate ring. The plurality of reflection points are spaced around the inner surface of the substrate ring and are configured to reflect light from the input pump laser to the output coupler in a series of reflections.

A technique which is suitable in joining an end surface of a laser medium to a transparent heat sink for maintaining thermal resistance therebetween low and avoiding large thermal stress from acting on the laser medium is to be provided. An end coat is provided on the end surface of the laser medium, a same-material layer constituted of a same material as the heat sink is provided on a surface of the end coat, a surface of the same-material layer and an end surface of the heat sink are activated in a substantially vacuum environment, and those activated surfaces are bonded in the substantially vacuum environment. A laser apparatus having low thermal resistance between the laser medium and the heat sink and high transparency at a joint interface therebetween, and no large thermal stress acting on the laser medium is thereby obtained.

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.

An optical resonator may be provided. The optical resonator may comprise a laser system with an adjustable optical path length. The optical resonator may include a back mirror. The back mirror may include a first back mirror surface and a second back mirror surface. The first back mirror surface and may provide a first optical path length for the optical resonator if the first back mirror surface may be included in the optical path. The second back mirror may provide a second optical path length for the optical resonator if the second back mirror surface is included in the optical path.

A laser apparatus including an optical element made of a CaF.sub.2 crystal and configured to transmit an ultraviolet laser beam obliquely incident on one surface of the optical element, the electric field axis of the P-polarized component of the laser beam propagating through the optical element coinciding with one axis contained in <111> of the CaF.sub.2 crystal, with the P-polarized component defined with respect to the one surface. A method for manufacturing an optical element, the method including causing a seed CaF.sub.2 crystal to undergo crystal growth along one axis contained in <111> to form an ingot, setting a cutting axis to be an axis inclining by an angle within 14.18±5° with respect to the crystal growth direction toward the direction of another axis contained in <111>, which differs from the crystal growth direction, and cutting the ingot along a plane perpendicular to the cutting axis.

Examples of the present invention include integrated erbium-doped waveguide lasers designed for silicon photonic systems. In some examples, these lasers include laser cavities defined by distributed Bragg reflectors (DBRs) formed in silicon nitride-based waveguides. These DBRs may include grating features defined by wafer-scale immersion lithography, with an upper layer of erbium-doped aluminum oxide deposited as the final step in the fabrication process. The resulting inverted ridge-waveguide yields high optical intensity overlap with the active medium for both the 980 nm pump (89%) and 1.5 μm laser (87%) wavelengths with a pump-laser intensity overlap of over 93%. The output powers can be 5 mW or higher and show lasing at widely-spaced wavelengths within both the C- and L-bands of the erbium gain spectrum (1536, 1561 and 1596 nm).

An optical oscillator according to an embodiment includes a first reflecting portion that transmits light having a first wavelength and reflects light having a second wavelength different from the first wavelength, a second reflecting portion that forms an unstable resonator together with the first reflecting portion and reflect light having the second wavelength, a laser medium that is disposed between the first reflecting portion and the second reflecting portion and emits light having the second wavelength due to incidence of light having the first wavelength, and a saturable absorption portion disposed on a side opposite to the first reflecting portion when viewed from the laser medium in the one direction, the first reflecting portion includes an incidence surface on which light having the first wavelength is incident, on a side opposite to the laser medium, a size of the second reflecting portion is smaller than a size of the first reflecting portion when viewed in the one direction, at least a part of a surface of the saturable absorption body on the side opposite to the laser medium includes a curved region curved toward the laser medium side, and the second reflecting portion is a dielectric multilayer film provided in the curved region.