A wavelength conversion element includes a crystal having a periodically poled structure in which polarization is inverted with an inversion period along a z-axis which is an input axis of a light pulse. The wavelength conversion element is configured to generate an output the inversion period (x) at each position x by change of the inversion period according to the position x, and when a target frequency linearly changing with the position x is set to f.sub.T(x)=b+ax, a frequency width of the output frequency is set to f(x), and the output frequency is set to f(x)=f.sub.T(x)+(x), the output frequency is set to coincide with the target frequency within a range satisfying a condition |(x)|f(x).

An apparatus for frequency comb generation comprises a component of second order nonlinearity, where the component is configured to interact with a laser beam or derivatives of the laser beam and thereby generate frequencies for the frequency comb. The apparatus comprises advantageously an optical manipulator, which both comprises the component but additionally is configured to introduce the beam or its derivatives in a repetitive or resonating manner to the component. The component is e.g. a monolithic or other solid optical resonator or microresonator comprising optical crystal and having said second order nonlinearity.

A method of making a quasi-phase-matching (QPM) structure comprising the steps of: applying a pattern to a substrate to define a plurality of growth regions and a plurality of voids; growing in a growth chamber a crystalline inorganic material on only the growth regions in the pattern, the crystalline inorganic material having a first polarity; applying an electric field within the growth chamber containing the patterned substrate with the crystalline inorganic material, wherein the electric field reaches throughout the growth chamber; and growing a crystalline organic material having a second polarity in the voids formed in the inorganic material under the influence of the electric field to influence the magnitude and the direction of the second polarity of the crystalline organic material, wherein the second polarity of the crystalline organic material is influenced to be different from the first polarity of the crystalline inorganic material in magnitude and/or direction.

A wavelength converter stabilizes output light intensity in which the light coupling efficiency to a light waveguide core is not easily varied. A mounting structure is adopted in which a substrate of a wavelength conversion element is a material with a lower refractive index for signal light than that of the core, and a support structure that suppresses elastic deformation by supporting the element through a contact at a tip end surface at a position corresponding to both end portions of the core at the occurrence of elastic deformation due to the thermal stress of the element is provided. The support structure is provided at a portion apart from a temperature control element at the top surface of a metal housing bottom surface member, and its top surface is disposed in the vicinity of a portion corresponding to both end portions of the core of the element in a support member.

A system for conversion or amplification using quasi-phase matched nonlinear optical wave-mixing includes a first radiation source for providing a pump radiation beam, a second radiation source for providing a signal radiation beam, a bent structure for receiving the pump radiation beam and the signal radiation beam, and an outcoupling radiation propagation portion for coupling out an idler radiation beam generated in the bent structure. A radiation propagation portion of the bent structure is made of a uniform three-dimensional material at least partly covered by a two-dimensional or quasi-two-dimensional material layer and has a dimension taking into account the spatial variation of the nonlinear optical susceptibility along the radiation propagation portion as experienced by radiation traveling along the bent structure for obtaining quasi-phase matched nonlinear optical wave-mixing in the radiation propagation portion. The dimension thereby is substantially inverse proportional with the linear phase mismatch for the nonlinear optical process.

A wavelength conversion element includes a crystal having a periodically poled structure in which polarization is inverted with an inversion period along a z-axis which is an input axis of a light pulse. The wavelength conversion element is configured to generate an output light pulse converted to have an output frequency f(x) corresponding to the inversion period (x) at each position x by change of the inversion period according to the position x, and when a target frequency linearly changing with the position x is set to f.sub.T(x)=b+ax, a frequency width of the output frequency is set to f(x), and the output frequency is set to f(x)=f.sub.T(x)+(x), the output frequency is set to coincide with the target frequency within a range satisfying a condition |(x)|f(x).

A heterogeneous waveguide is configured to achieve a nonlinear optical interaction, the waveguide including at least two materials in cross-section. The first material may or may not be poled or patterned and generally has a nonlinear optical property for generating at least one new frequency by mixing two of a plurality of input optical waves, and at least one of the other (second) materials is patterned for defining a waveguide mode in the cross-section, and for achieving phase-matched interactions of the waves along the propagation direction. Alternatively, the second material may be employed in increasing the modal confinement and improving efficiency. The optical modes are distributed between the two or more materials (e.g., in a hybrid mode). Implementations described also include methods of fabricating the heterogeneous waveguide.

Systems and methods implementing a stack on a substrate, where the stack includes a plurality of films structured as layers to convert radiation incident to the stack to radiation of a nonlinear optical signal different from the incident radiation or to a harmonic of the incident radiation, can be used in a variety of applications. The stack can be structured having parameters selected with respect to conversion efficiency and bandwidth the converted radiation. Additional systems and methods can be used in a variety of applications.

A method for growing a periodically-poled nonlinear crystal may include placing a seed crystal into a melt to form a seed crystal melt mixture, where the seed crystal may include at least one of strontium tetraborate (SBO) or lithium triborate (LBO), and where the melt includes at least one of a mixture of Sr, B, and O or a mixture of Li, B, and O. The method may further include heating the seed crystal melt mixture to a predetermined temperature until the periodically-poled nonlinear crystal forms.

An optical parametric device (OPD), which is selected from an optical parametric oscillator (OPO) or optical parametric generator (OPG), is configured with a nonlinear optical element (NOE) which converts an incoupled pump radiation at first frequency into output signal and idler radiations at one second frequency or different second frequencies, which is/are lower than the first frequency, by utilizing nonlinear interaction via a random quasi-phase matching process (RQPM-NOE). The NOE is made from a nonlinear optical material selected from optical ceramics, polycrystals, micro and nanocrystals, colloids of micro and nanocrystals, and composites of micro and nanocrystals in polymer or glassy matrices. The nonlinear optical material is prepared by modifying a microstructure of the initial sample of the NOE such that an average grain size is of the order of a coherence length of the three-wave interaction which enables the highest parametric gain achievable via the RQPM process.