Development of ion-implanted optical waveguides in optical materials: A review

Energetic ion beams with diverse energies, species and beam dimensions have been extensively utilized to modify the properties of materials to achieve versatile applications in many aspects of industry, agriculture and scientific research. In optics, the ion-beam technology has been applied to fabricate various micro- and submicrometric guiding structures on a wide range of optical crystals through the efficient modulation of the refractive indices or structuring of the surface, realizing various applications in many branches of photonics. The ion-beam fabricated optical waveguides and other photonic structures have shown good guiding performance as well as properties related to the materials, suggesting promising potential for many aspects of photonics. This paper gives the state-of-the-art review of fabrication, characterization and application on the ion-beam-processed micro- and submicrometric photonic structures by highlighting the most recent research progress. A brief prospect is presented by focusing on a few potential spotlights.

Micro- and submicrometric waveguiding structures in optical crystals produced by ion beams for photonic applications

A range of ion beam techniques have been used to fabricate a variety of photonic guiding structures in the well-known lithium niobate (LiNbO3 or LN) crystals that are of great importance in integrated photonics/optics. This paper reviews the up-to-date research progress of ion-beam-processed LiNbO3 photonic structures and reports on their fabrication, characterization, and applications. Ion beams are being used with this material in a wide range of techniques, as exemplified by the following examples. Ion beam milling/etching can remove the selected surface regions of LiNbO3 crystals via the sputtering effects. Ion implantation and swift ion irradiation can form optical waveguide structures by modifying the surface refractive indices of the LiNbO3 wafers. Crystal ion slicing has been used to obtain bulk-quality LiNbO3 single-crystalline thin films or membranes by exfoliating the implanted layer from the original substrate. Focused ion beams can either generate small structures of micron or submicron dimen...

Photonic guiding structures in lithium niobate crystals produced by energetic ion beams

We report herein on an efficient sonochemical method for the synthesis of rare earth orthovanadate nanorods/nanoparticles/nanospindles, (general formula RVO4; R = La, Ce, Nd, Sm, Eu and Gd). TGA, XRD, FTIR, Raman, UV–Vis, and TEM studies are employed for their characterization and for understanding their morphologies. In order to vary the textural properties of the rare earth vanadates, two surfactants, polyethylene glycol (PEG) and amphiphilic triblock copolymer Pluronic P123, are chosen in the preparation. While the sonochemical synthesis in the presence of PEG results in the formation of nearly spherical nanoparticles of LaVO4, CeVO4, SmVO4 and EuVO4, the same technique yields nanorods and nanospindles of NdVO4 and GdVO4, respectively. When P123 is used as the surfactant, the morphologies of RVO4 are strikingly different, and in most cases nanorods and nanospindles are formed. The photocatalytic activities of the rare earth orthovanadate have been evaluated by studying the degradation of methylene blue, and CeVO4 seems to be the best catalyst in the heterogeneous photolysis. The electrocatalytic activity of the vanadates has been examined by studying the hydrogen evolution reaction using a linear sweep voltammogram technique in 1 M of a H2SO4 solution. GdVO4 seems to be the best electrocatalyst.

Synthesis and Characterization of Rare Earth Orthovanadate (RVO4; R = La, Ce, Nd, Sm, Eu & Gd) Nanorods/Nanocrystals/Nanospindles by a Facile Sonochemical Method and Their Catalytic Properties

Silicon(II) Coordination Chemistry: N‐Heterocyclic Carbene Complexes of Si2+ and SiI+

The planar waveguides have been fabricated in z-cut β-BaB2O4 crystal by 22MeV O+ ion implantation at doses ranging from 5×1012 to 5×1014ions∕cm2 at room temperature The waveguides were characterized by the prism-coupling method Monomode, nonleaky planar waveguides at λ=633nm in β-BBO single crystals were fabricated at doses from 5×1012 to 2×1013ions∕cm2, and two mode and three mode waveguides were fabricated at doses from 4×1013 to 5×1014ions∕cm2, respectively The refractive index profiles of the waveguides are reconstructed using reflectivity calculation method The propagation loss of the measured ion implanted waveguide was about 16dB∕cm It was found that positive changes of extraordinary refractive indices happened in the guiding regions, and such changes increased with the doses, which were different from most of the observed ion-implanted waveguides

Planar optical waveguides in β-BaB2O4 produced by oxygen ion implantation at low doses

We report on the fabrication and characterization of low-loss planar and stripe waveguides in a Nd3+-doped glass by 6MeV oxygen-ion implantation at a dose of 1×1015ions∕cm2. The dark mode spectroscopy of the planar waveguide was measured using a prism coupling arrangement. The refractive index profile of the planar waveguide was reconstructed from a code based on the reflectivity calculation method. The results indicate that a refractive index enhanced region as well as an optical barrier have been created after the ion beam processing. The near-field mode profiles of the stripe waveguide were obtained by an end-fire coupling arrangement, by which three quasitransverse electric modes were observed. After annealing, the propagation losses of the planar and stripe waveguides were reduced to be ∼0.5 and ∼1.8dB∕cm, respectively.

Low-loss planar and stripe waveguides in Nd3+-doped silicate glass produced by oxygen-ion implantation

The planar waveguides in z-cut stoichiometric LiNbO3 crystal have been fabricated by 3.0 MeV oxygen ion implantation with the dose of 6×1014ions∕cm2 at room temperature. The modes of the waveguides were measured by the prism-coupling method with the wavelength 633 and 1539 nm, respectively. The refractive index profiles of the waveguides were reconstructed using reflectivity calculation method. The Rutherford backscattering/channeling technique was used to investigate the damage produced by the ion implantation, the minimum yield of the spectra was 4.52%. The propagation loss of waveguide was 0.61 dB/cm obtained by fiber probe technique. It was found that positive changes of extraordinary refractive indices happened in the guiding regions, and such change increased after the annealing treatment at 260 °C for 60 min.

Optical properties of stoichiometric LiNbO3 waveguides formed by low-dose oxygen ion implantation

Planar waveguides in x-cut YVO4 crystals were produced by ion-implanted Si+ ions with energies from 2.6 to 3.0 MeV at doses of 1×1013−1.5×1014 ions/cm2. The number of propagation modes varied from 1 to 3 as the doses of the implanted ions increased. The effective refractive indices of all the observed waveguide modes were higher than the refractive index of the substrate, which meant an index-enhanced guiding layer with thickness of ∼2 μm formed to confine the light propagation. The minimum propagation loss of the measured YVO4 waveguide was 0.27 dB/cm after annealing under suitable conditions.

Low-loss optical planar waveguides in YVO4 produced by silicon ion implantation at low doses

The selected etching in lithium niobate (LiNbO 3 ) crystals is carried out by two different ion implantation and differential wet etching. The LiNbO 3 samples are cleaned and partially masked with photoresist in lithographic procedure firstly, followed by 1.5 MeV O + or Si + ion implantation at a dose of 1×10 15 ions/cm 2 at room temperature. It is found that the ion implanted region can be etched more easily than that protected by photoresist mask using mixture of hydrofluoric and nitric acids at room temperature. The surface morphology of the etched samples is examined using surface profilometer and SEM. Ridge structures are formed by the ion implantation and the subsequent selective wet etching. The results show that this technique may be suitable for fabrication of high quality ridge waveguides.

Rui Nie

Papers

Planar optical waveguides in β-BaB2O4 produced by oxygen ion implantation at low doses

Low-loss planar and stripe waveguides in Nd3+-doped silicate glass produced by oxygen-ion implantation

Optical properties of stoichiometric LiNbO3 waveguides formed by low-dose oxygen ion implantation

Low-loss optical planar waveguides in YVO4 produced by silicon ion implantation at low doses

Selective etching in LiNbO3 combined of MeV O and Si ion implantation with wet-etch technique