0000000000136757
AUTHOR
S. Riva-sanseverino
Silica masks for improved surface poling of lithium niobate
Surface periodic poling of congruent lithium niobate was performed with the aid of photolithographically defined silica masks. The latter helped improving the control of duty cycle in the periodic domain poling, with 50:50 mark-to-space ratios. The role of silica was ascertained by numerically solving the Poisson equation.
Multi-line NIR-RGB emission in Nd:LiNbO3 RPE optical waveguides
Simultaneous generation of four spectral emission lines has been achieved in Nd-doped lithium niobate reverse proton exchange optical waveguide cavities. Using a pump at 800 nm, the four lines were found and they are due to lasing at 1.3735 combined with parametric conversion at 0.687, 0.574 and 0.4 mum.
Ultraviolet quasi-phase-matched second harmonic generation in surface periodically poled lithium niobate optical waveguides
The compatibility of low concentration (alpha-phase) proton exchange channel waveguides with electric field surface periodic poling of congruent lithium niobate (SPPLN) crystals has been experimentally demonstrated. With such waveguides, we obtained ultraviolet second harmonic generation (SHG) by first order quasi-phase-matching (QPM), a result made possible by the fabrication, on Z-cut LN crystals, of periodic structures with a pitch down to 750 nm. Nonlinear copropagating QPM-SHG measurements have been carried out on such structures. The pump source was a Ti:sapphire laser with a tunability range of 700-980 nm and a 40 GHz linewidth. We have measured UV continuous wave light at 390 nm by …
Integrated optic surface plasmon resonance measurements in a borosilicate glass substrate
The surface plasmon resonance (SPR) technique is a well-known optical method that can be used to measure the refractive index of organic nano-layers adsorbed on a thin metal film. Although there are many configurations for measuring biomolecular interactions, SPR-based techniques play a central role in many current biosensing experiments, since they are the most suited for sensitive and quantitative kinetic measurements. Here we give some results from the analysis and numerical elaboration of SPR data from integrated optics experiments in a particular borosilicate glass, chosen for its composition offering the rather low refractive index of 1.4701 at 633 nm wavelength. These data regard the…
Nanopatterned ferroelectric crystals for parametric generation
We report on recent results by surface periodic poling on lithium niobate and lithium tantalate. Such approach allows periodic inversion of the second order susceptibility with nanoscale features using insulating masks. We achieved a world-best 200 nm feature size, as well as good compatibility with alpha-phase proton exchanged channel waveguides in lithium niobate. Preliminary results of surface periodic poling in lithium tantalate also show similar characteristics. Surface poling is best suited for integrated optics devices in technologically-demanding configurations such as backward second harmonic generation and counter propagating optical parametric amplification
Continuous-wave backward frequency doubling in periodically poled lithium niobate
We report on backward second-harmonic-generation in bulk periodically poled congruent lithium niobate with a 3.2 microns period. A tunable continuous-wave Ti:sapphire laser allowed us exciting two resonant quasi-phase-matching orders in the backward configuration. The resonances were also resolved by temperature tuning and interpolated with standard theory to extract relevant information on the sample.
Nanotechnology in lithium niobate for integrated optic frequency conversion in the UV
In the domain of Earth Explorer satellites nanoengineered nonlinear crystals can optimize UV tunable solid-state laser converters. Lightweight sources can be based on Lithium Niobate (LN) domain engineering by electric field poling and guided wave interactions. In this Communication we report the preliminary experimental results and the very first demonstration of UltraViolet second-harmonic generation by first-order quasi-phase-matching in a surface-periodically-poled proton-exchanged LN waveguide. The pump source was a Ti-Sapphire laser with a tunability range of 700- 980 nm and a 40 GHz linewidth. We have measured UV continuous-wave light at 390 nm by means of a lock-in amplifier and of …
Guided-wave frequency doubling in surface periodically poled lithium niobate: competing effects
We carried out second-harmonic generation in quasi-phase-matched ? -phase lithium niobate channel waveguides realized by proton exchange and surface periodic poling. Owing to a limited ferroelectric domain depth, we could observe the interplay between second-harmonic generation and self-phase modulation due to cascading and cubic effects, resulting in a nonlinear resonance shift. Data reduction allowed us to evaluate both the quadratic nonlinearity in the near infrared as well as the depth of the uninverted domains. © 2007 Optical
Integrated Optical Technique for Detection of Electro-Optical Non-Linearities in Thin Films
A simple method for detection of electro-optical non-linearities in thin films is presented. The method involves an easily fabricated structure and a little practice in integrated optical techniques. It is also possible to detect small induced variations of refractive index, using lower voltage with respect to those applied in a conventional Kerr cell. We have sucessfully tested our method using two different polymer materials as thin films. In both of these we have observed an induced ?n ? 3 10?5 with an electric field of 60 V/?, with a response time round about 300 nsec. The experimental values of induced ?n versus electric field fit very well a parabola, proving the quadratic behavior of…
Light-Induced Sublimation of Cadmium Sulphide
It has recently been shown that single crystal CdS, illuminated by light whose photon energy exceeds the bandgap, can eject particles from its surface while the temperature is well below the value required for vacuum sublimation. This phenomenon has obvious applications to the fabrication of surface structures as well as to the production of thin films that can show good CdS stoichiometry. This work will present several data on the morphology of the etched surface and its dependance on crystal orientation; results of an analysis of the recondensed thin film phase from the ejected material will also be shown. Emphasis will be devoted to examples of high resolution surface structures fabricat…
Frequency doubling in surface periodically poled lithium niobate waveguides: Competing effects
We fabricated α-phase pro ton-exchanged (PE) lithium niobate (LN) channel waveguides quasi phase-matched (QPM) via surface periodic poling (SPP) and carried out the first experimental demonstration of second harmonic generation (SHG) in such devices.[1] Experiments were performed by employing an optical parametric amplifier/oscillator producing 25 ps pulses in the range 1.1-1.6 μm with a line-width less than 2cm−1 and a repetition rate of 10Hz. SHG measurements were performed either at a fixed wavelength by varying the fundamental frequency (FF) input power or by scanning the FF wavelength, ratioing the second harmonic (SH) output to the FF input to obtain the conversion efficiency. By repe…
Study of Photo-Induced Thin Film Growth on Cds Substrates.*
ABSTRACTPhoto-induced growth of ZnS on CdS has been studied using amorphous (thin film) and single-crystal substrates. The effect has been found to occur for light of wavelength shorter than the CdS absorption edge; a maximum light-induced thickness enhancement of 700 Å has been obtained for the ZnS film, with a growth rate of 2000 Å/min. The lightinduced growth, with its observed “memory” of several minutes is consistent with photo-desorption of an adlayer.
Nonstoichiometric silica mask to fabricate reverse proton-exchange waveguides in lithium niobate crystals
Producing channel waveguides requires a photolithographic mask, but the standard technique of using thermally evaporated metal films for proton exchange has proved to be unsuitable for withstanding the rather aggressive process of reverse proton exchange. We report the fabrication of a nonstoichiometric silica mask by ion-plating plasma-assisted deposition. This mask is strong enough to resist both direct and reverse proton exchange and is also compatible with anisotropic dry etching for patterning the mask and with electric field poling. Our technique is a practical alternative to the use of SiO2 sputtered masks.