J. Webjörn

Blue light generated by frequency doubling of laser diode light in a lithium niobate channel waveguide

Blue light was generated in a LiNbO/sub 3/ channel waveguide by frequency doubling radiation from a laser diode in a guided to guided wave interaction, utilizing first-order quasi-phase-matching in a periodically domain inverted structure. A fabrication method that does not depend on the use of titanium was used. A periodic pattern of silicon oxide on the positive c-face of LiNbO/sub 3/ was used in combination with a heat treatment to achieve a periodic outdiffusion and domain reversal in the surface layer. A channel guide was subsequently formed by proton exchange.<<ETX>>

Fabrication of periodically domain-inverted channel waveguides in lithium niobate for second harmonic generation

A method to produce periodically domain-inverted channel waveguides in LiNbO/sub 3/ is reported. With this type of waveguide, using quasi-phase matching (QPM), arbitrary wavelengths can be frequency doubled by choosing the appropriate period. It is concluded that, with improved fabrication methods, it will be possible to generate milliwatts of blue light with a diode laser as pump, which is of considerable interest. >

Wet etching of proton-exchanged lithium niobate-a novel processing technique

It is known that in proton-exchanged wave-guides in lithium niobate,1 the crystal structure is modified. We demonstrate that proton-exchanged regions on the c+-face can be etched away selectively using a mixture of HF and HNO3. In this way it is possible to form, for example, a groove with a smooth bottom surface. The unexchanged c+-face of lithium niobate is only very slowly etched by this acid.

Influence of various imperfections on the conversion efficiency of second-harmonic generation in quasi-phase-matching lithium niobate waveguides

The generation of coherent blue light by frequency doubling of radiation from semiconductor lasers in quasi-phase-matching lithium niobate waveguides has recently been demonstrated, but with a conversion efficiency significantly lower than the theoretically predicted value. We have experimentally investigated the performance of some quasi-phase-matching waveguides by measurements of the second-harmonic power and the integral of the second-harmonic power with respect to the fundamental wavelength at a wavelength scan. These experimental results are combined with a theoretical analysis. It is concluded that the inhomogeneities in the effective index, the absence of domain inversion in some regions along the waveguide, and the suppression of the nonlinearity that is due to the proton exchange process are the most important imperfections to deal with in the future optimization of the domain inversion process and the waveguide formation.

Postfabrication changes and dependence on hydrogen concentration of the refractive index of proton‐exchanged lithium tantalate waveguides

Postfabricationchanges and dependence on hydrogen concentration of the refractive index ofproton-exchanged lithium tantalate waveguides

Structural influence of proton exchange on domain-inverted lithium niobate revealed by means of selective etching

Selective etching is used to study the influence of different proton-exchange methods on the crystal structure of periodically domain-inverted lithium niobate. The annealed proton-exchange method is shown to interfere strongly with previously patterned domains. A less common graded proton-exchange method that leaves the ferroelectric domain structure intact is demonstrated. >

Periodic domain inversion and generation of blue light in lithium tantalate waveguides

Generation of blue light from small solid-state light sources is a technological challenge with applications in many areas, among others optical data storage. The authors report frequency doubling using third-order quasi-phase matching in periodically domain-inverted lithium tantalate waveguides. Periodic proton exchange followed by heat treatment caused periodic domain inversion and waveguide formation in a single step. Infrared radiation from a dye laser was coupled through the waveguides and second-harmonic generation corresponding to third-order quasi-phase-matching was observed.<<ETX>>

SINGLE-DOMAIN LAYERS FORMED IN MULTIDOMAIN LITAO3 BY PROTON EXCHANGE AND HEAT TREATMENT

Proton exchange and subsequent heat treatment can yield single‐domain layers at the surfaces of initially multidomain z‐cut LiTaO3. The thickness of these single‐domain layers is equal to the thickness of the domain‐inverted layer that the same processing parameters cause in initially single‐domain samples. This letter also describes how the domain structure develops when heat treatment is carried out above the Curie temperature. The results are discussed in relation to a recently proposed model for the domain‐inversion mechanism.

Efficient quasi-phase-matched frequency doubling of a high power, unpolarized fiber laser source

Summary form only given. The combination of sum frequency generation (SFG) and SHG processes has generated 590 mW of green light from a planar periodically poled lithium niobate (PPLN) waveguide, which, to the best of our knowledge, is the highest power ever reported from such a device. In this experiment, combining the SFG and SHG processes within the planar waveguide produced 35% more green power than would be obtained by frequency doubling the two infrared polarizations separately.