A macroscopic entanglement state in which a polarization state has a strong quantum correlation is realized by use of a macroscopic laser light. A laser oscillator includes a ring resonator having an optical fiber ring, an optical amplifier for maintaining an amplitude of a laser pulsed light propagating on the optical fiber ring, and three optical fibers that are connected with respective polarization controllers, and, after changing a polarization state of the laser pulsed light being a qubit extracted at a predetermined branch ratio from the optical fiber ring by the polarization controllers, couples the changed laser pulsed light whose polarization state has been changed with the laser pulsed light propagating on the optical fiber ring, and each polarization controller rotates the polarization state of the laser pulsed light with an S1 axis, an S2 axis, and an S3 axis, which are orthogonal to each other, as a rotation axis.

A fiber amplifier is provided, including a pump laser (202), a pump and signal combiner (203), and a few-mode doped fiber (204). The pump laser (202) is configured to output pump light. The pump and signal combiner (203) is configured to couple input few-mode signal light and the pump light into the few-mode doped fiber (204). Refractive indexes of a fiber core of the few-mode doped fiber (204) are distributed to be gradient along a radial direction of a cross section, the fiber core is etched with periodic gratings along an axial direction, and periods of the gratings satisfy a phase matching condition. The fiber amplifier achieves strong coupling and co-amplification between optical signal modes, thereby reducing a differential gain between mode groups.

A method of fabricating an optical fiber, the method including providing a core portion including a doped portion having greater than or equal to 1.6 wt. % of a halide dopant and eliminating seed precursor sites at an exterior surface of the core portion, the seed precursor sites forming seeds in the optical fiber, wherein the eliminating the seed precursor sites includes one or more of: (i) fabricating the core portion by densifying an exterior portion of a silica soot body prior to exposing the silica soot body to the halide dopant, and (ii) exposing the exterior surface of the core portion to a reactive etchant. The method further including forming an optical fiber preform by applying cladding material to the exterior surface of the core portion and drawing the fiber preform into the optical fiber.

A system includes multiple first thulium-doped fiber lasers each configured to generate pumplight. The system also includes a second thulium-doped fiber laser configured to receive the pumplight from the first thulium-doped fiber lasers and a seed signal. The second thulium-doped fiber laser is also configured to amplify the seed signal using the pumplight. The first thulium-doped fiber lasers are configured to forward-pump the second thulium-doped fiber laser. The second thulium-doped fiber laser includes a fiber gain medium, where the fiber gain medium includes a core doped with thulium and a cladding. The fiber gain medium is longitudinally up-tapered such that a diameter of the core and a diameter of the cladding increase along at least a portion of a length of the fiber gain medium.

An apparatus includes a first photonic crystal fiber. The first photonic crystal fiber includes a first dispersion at a pump wavelength. The first photonic crystal fiber includes a zero dispersion. The pump wavelength is within 100 nm of the zero dispersion. The first dispersion is normal. The first photonic crystal fiber includes a first mode field diameter at the pump wavelength. The apparatus also includes a second photonic crystal fiber coupled to the first photonic crystal fiber and outputs a broadband spectrum. The second photonic crystal fiber includes a second dispersion at the pump wavelength. The second dispersion is anomalous. The second dispersion is negative, and the first dispersion is positive. The second photonic crystal fiber includes a second mode field diameter at the pump wavelength. The second mode field diameter is smaller than the first mode field diameter.

An objective is to provide an optical amplifier having a core excitation configuration that improves amplification efficiency. An optical amplifier according to the present invention includes an excitation light conversion fiber 11 that absorbs first excitation light L1 propagating in a cladding and having a first wavelength and emits, into a core, spontaneous emission light having a second wavelength, an oscillator 12 for causing the spontaneous emission light to be reflected on two reflectors 15 to reciprocate the light within the core of the excitation light conversion fiber 11 and laser-oscillating second excitation light L2 having the second wavelength, and an amplification fiber 13 that is connected to the excitation light conversion fiber 11 and amplifies signal light with the second excitation light L2 supplied from the excitation light conversion fiber 11 to the core.

An object is to provide an optical amplifier with a cladding pumped configuration that improves amplification efficiency. The optical amplifier according to the present invention includes a pump light conversion fiber 11 that converts first pump light L1 with a first wavelength propagating in a cladding into second pump light L2 with a second wavelength, an amplification fiber 13 that is connected to the pump light conversion fiber 11 and optically amplifies signal light Ls with the second pump light L2 supplied to the cladding from the pump light conversion fiber 11, and an oscillator 12 that causes the second pump light L2 to be reflected on two reflectors 15 and to reciprocate within the claddings of the pump light conversion fiber 11 and the amplification fiber 13 to cause laser oscillation of the second pump light L2.

A lidar device, comprising a laser generator and a lidar unit, is provided and operated with frequency modulation continuous wave. The laser generator comprises an amplifier unit; and a reflector unit connected with at least one end of the amplifier unit. The amplifier unit comprises at least one first luminous gain area and at least one second luminous gain area. The first luminous gain area is operated in a saturated region with a first current source applied. The second luminous gain area is operated in a linear region with a second current source applied. Thus, a laser is generated and outputted to the lidar unit. The laser generator is operated with the luminous gain areas of the amplifier unit pushed into the saturated region to suppress intensity modulation and fix power. Even if current changes, frequency drifts only with continuity and adjustability achieved and no mode hop happened.

An optical-resolution photoacoustic microscopy (OR-PAM) system for visualizing water content deep in biological tissue uses an all-fiber 1930-nm hybrid optical parametrically-oscillating emitter. The emitter includes a tunable laser source whose output is amplified by a first erbium-doped fiber amplifier (EDFA). The output of the first amplifier is modulated with a Mach-Zehnder amplitude modulator that receives an RF signal with a nanosecond pulse width and a multiple kilohertz repetition rate. A second EDFA further amplifies the signal and passes it to a fiber circulator that in turn delivers it to a 1950/1550 mm fiber wavelength-division-multiplexing coupler WDM. The coupler introduces the signal to a cavity that includes a spool of highly nonlinear fiber and a Thulium-doped fiber amplifier TDFA. From the TDFA the signal reaches a 50/50 fiber coupler that sends part to a second output TDFA and guides part back to the cavity through a port of the WDM.

The system and method for a scalable optically pumped CO.sub.2 laser. The optically pumped CO.sub.2 laser having a Tm fiber laser configured to pump a Q-switched Ho laser that is configured to pump a molecular isotopologue mix of CO.sub.2 above atmospheric pressure, to produce a broadband, high energy, tunable output beam.