Bright entangled photon sources including an alignment-free, fiber-based, mechanically-rugged and generic interferometric module are disclosed. The inherent phase-stability of a Sagnac interferometer is deployed. High down-conversion efficiency of periodically poled nonlinear-waveguides is combined with the optical gain of semiconductor optical amplifiers and immunity of fiber optics. A single compact interferometric engine combines these attributes, allowing highly stable, integrable and bright polarization entangled-photon sources operating at room temperature. Using a minimum number of in-line optical parts, the compact module is based on a novel method that enhances the long-term stability and efficiency without compromising the entanglement quality. Besides energy entanglement, polarization entanglement is presented and set through the operational conditions. An optional periodically poled nonlinear waveguide can be hosted to achieve the desired spectral bandwidth and photons generation rate. The result is a zero-maintenance, lightweight, low-power consumption engine of compact and fully-integrable bright polarization-entangled photon sources.

An optical waveguide structure comprises a first coupler and a second coupler that, in combination, direct a first-wavelength light to travel through a nonlinear-optical waveguide, the two couplers and an extension waveguide but not a secondary waveguide, a first resonator loop is defined for which the first-wavelength light is resonant. The two couplers, in combination, also direct a second-wavelength light to travel through the nonlinear-optical waveguide, the two couplers and the secondary waveguide but not the extension waveguide, wherein a different second resonator loop is defined for which the second-wavelength light is resonant.

An optical waveguide structure comprises a nonlinear optical waveguide comprising a nonlinear optical material having a second order nonlinear coefficient that changes with a direction of light propagation. A first portion of the nonlinear optical waveguide in which a light propagating through the first portion is affected by a positive value of a second order nonlinear coefficient. A second portion of the nonlinear optical waveguide in which the light propagating through the first portion is affected by a negative value of a second order nonlinear coefficient, wherein a set of dimensions in the nonlinear optical waveguide in the first portion and the second portion is selected to cause the light to have a phase walk-off that is an odd multiple of 180 degrees.

A method for frequency-converting a source optical signal in order to produce a useful optical signal, by mixing a plurality of waves, implements a plurality of waveguides that are coupled together. Individual parameter values of the waveguides, as well as at least one coupling parameter, are selected so as to obtain the useful signal with a high intensity. Such a method for producing the useful signal is suitable for a spectroscopic application, in particular a molecular spectroscopy application.

Improved efficiency for nonlinear optical interactions is provided by using strongly confining waveguides for simultaneous imposition of dispersion design constraints at two or more dispersion orders. Quasi-phase-matching allows for phase-matching to be accomplished independently of the waveguide design, which helps provide sufficient design freedom for the dispersion design.

The present invention discloses a distributed pulsed light amplifier based on optical fiber parametric amplification, comprising a pump pulsed light source, a sensing pulsed light source, a synchronization device, a two-in-one optical coupler, an optical circulator, a parametric amplification optical fiber, a first optical filter, a photoelectric detector and a signal acquisition device. According to the distributed pulsed light amplifier, high-power pulsed light is used as pump light to generate an optical fiber parametric amplification effect near a zero-dispersion wavelength of an optical fiber, thereby amplifying a power of another sensing pulsed light. Meanwhile, due to the fact that effective optical fiber parametric amplification cannot be achieved through low-power light leakage outside a duration interval of the pump pulsed light, leaked light from the sensing pulsed light cannot be amplified, and the effect of amplifying a pulse extinction ratio can be achieved at the same time.

A cylindrical electrode module of a fiber optic laser system includes an inner cylinder having an inner repeating pattern of longitudinally-aligned positive and negative electrodes on an outer surface of the inner cylinder. The cylindrical electrode mode includes an outer cylinder that encloses the inner cylinder. The outer cylinder that has an outer repeating pattern of longitudinally-aligned negative and positive electrodes on an inner surface of the inner cylinder that are in corresponding and complementary, parallel alignment with the positive and negative electrodes of the inner repeating pattern on the outer surface of the inner cylinder. The cylindrical electrode module includes an optical fiber having an input end configured to align with and be optically coupled to a high power pump laser. The optical fiber is wrapped around the inner cylinder within the outer cylinder to form a cylindrical fiber assembly. The electrodes are activated to achieve quasi-phase matching.

A fiber laser system includes a high power pump laser, an optical fiber that is aligned to receive output from the high power pump laser. The fiber laser system includes a first pair of orthogonally opposed, periodic electrode structures longitudinally aligned on opposite first and second sides of the optical fiber. The fiber laser system includes a controller that is communicatively coupled to the first pair of periodic electrode structures. The controller performs variable period poling of the first pair of periodic electrode structures to achieve quasi-phase matching (QPM).

A planar optical resonator capable of parametrically generating frequency combs includes two optical waveguide cores forming inner and outer loops, the resonator having two sections, in which laterally adjacent segments of the cores are resonantly optically coupled to each other at two separate wavelength regions causing separate peaks in the second order dispersion. The resonator sections may be configured to suppress integrated dispersion of the resonator in a broad spectral range favorably for generating a spectrally uniform frequency comb.

Improved efficiency for nonlinear optical interactions is provided by using strongly confining waveguides for simultaneous imposition of dispersion design constraints at two or more dispersion orders. Quasi-phase-matching allows for phase-matching to be accomplished independently of the waveguide design, which helps provide sufficient design freedom for the dispersion design.