A nonlinear fiber interferometer is disclosed suitable for fiber sensor and other applications. A first nonlinear fiber section amplifies probe and conjugate sidebands of a pump through four-wave mixing. A second section introduces a phase shift to be measured, for example from a sensor. A third nonlinear fiber section amplifies with phase-sensitive gain to increase signal-to-noise ratio. Based on phase-sensitive output power of probe and/or conjugate components, the phase shift can be measured. Superior performance can be obtained by balancing gain between the (first and third) nonlinear sections. Non-fiber, for example photonic integrated circuit, embodiments are disclosed. Differential sensing, alternative detection schemes, sensing applications, associated methods, and other variations are disclosed.

A hollow-core anti-resonant-reflecting fibre (HC-AF) includes a hollow-core region, an inner cladding region, and an outer cladding region. The hollow-core region axially extends along the HC-AF. The inner cladding region includes a plurality of anti-resonant elements (AREs) and surrounds the hollow-core region. The outer cladding region surrounds the inner cladding region. The hollow-core region and the plurality of AREs are configured to provide phase matching of higher order hollow-core modes and ARE modes in a broadband wavelength range.

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.

A technique to generate terahertz radiation is disclosed, where a pump beam (12) is coupled into an optical element (50) made of a medium with non-linear optical properties having plane-parallel front and rear boundary surfaces (51, 52), wherein the pump beam (12) is split into a set of partial pump beams (121) by reflection and/or diffraction on a periodic relief structure (53) of said optical element (50). The partial pump beams travel along a direction at an angle γ that satisfies the velocity matching condition of v.sub.p,cs cos(γ)=v.sub.THz,f within the given medium, where v.sub.p,cs is the group velocity of the pump beam, v.sub.THz,f is the phase velocity of the terahertz radiation and the speed a planar envelope (212) travels toward the front boundary surface (51) of the optical element (50), and angle γ is the angle formed by the pulse front envelope and the phase front of the pump beam.

A nonlinear fiber interferometer is disclosed suitable for fiber sensor and other applications. A first nonlinear fiber section amplifies probe and conjugate sidebands of a pump through four-wave mixing. A second section introduces a phase shift to be measured, for example from a sensor. A third nonlinear fiber section amplifies with phase-sensitive gain to increase signal-to-noise ratio. Based on phase-sensitive output power of probe and/or conjugate components, the phase shift can be measured. Superior performance can be obtained by balancing gain between the (first and third) nonlinear sections. Non-fiber, for example photonic integrated circuit, embodiments are disclosed. Differential sensing, alternative detection schemes, sensing applications, associated methods, and other variations are disclosed.

A system for nonlinear frequency conversion includes an acousto-optic modulator for diffracting a portion of an input laser beam as a first-order beam and transmitting a non-diffracted portion of the input laser beam as a zeroth-order beam. The system also includes a nonlinear crystal arranged to receive and frequency convert each of the zeroth-order and first-order beams to generate two respective frequency-converted laser beams, whereby, when the acousto-optic modulator changes the average-power ratio between the zeroth-order and first-order beams, variations of the heat load in the nonlinear crystal are minimized. Either one of the two frequency-converted laser beams may be used as an output laser beam of the system, while the other one of the two frequency-converted laser beams serves to stabilize the heat load in the nonlinear crystal when the acousto-optic modulator is operated to change the average power in the output laser beam.

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.

A device for high-speed real-time sampling of mid-infrared ultrafast light signals includes a time domain amplification unit and a detection unit. The time domain amplification unit is used to perform sampling and time domain amplification on signal light incident to the time domain amplification unit, and convert the signal light of a mid-infrared band into a near-infrared/visible band. The detection unit is used to receive and record information of the to-be-detected signal light processed by the time domain amplification unit to realize high-speed real-time sampling and measurement of the mid-infrared ultrafast light signal. The present disclosure can accurately obtain subpicosecond transient characteristics of the light signal, breaks through the capacity limit to the response rate of a traditional photoelectric detector, the bandwidth of the oscilloscope and the like, and is applicable to femtosecond-level mid-infrared ultrafast light signals.

Methods and apparatuses for manipulating and modulating of laser beams. The methods and apparatuses enable activating and deactivating of laser beams, while the laser systems maintain their operating power. Further, a hybrid pump module configured to be coupled to an optical fiber having a core and at least one clad, comprising: at least one focusing lens in optical with the optical fiber; plurality of diode modules, each configured to output a multi-mode beam in optical path with the clad; and at least one core associated module, in optical path with the core, configured to provide selected functions. Further, apparatus and methods configured for frequency doubling of optical radiation.

An optical frequency conversion method, apparatus, and device are provided. Micro-nano fibers and guiding fibers are cascaded, to change an optical frequency conversion manner from using a long micro-nano fiber as a frequency conversion medium to cascading a first quantity of shorter micro-nano fibers and a second quantity of guiding fibers to perform optical frequency conversion. A length of each micro-nano fiber is not greater than a coherence length of a fundamental-frequency pump light signal and a frequency-tripled light signal. The frequency-tripled light generated by cascaded micro-nano fibers is coherently superposed. A phase difference between frequency-tripled light components is controlled by adjusting incident power of the fundamental-frequency pump light, to achieve constructive interference, thereby significantly enhancing the frequency-tripled light signal and effectively improving the optical frequency conversion efficiency.