Fabrication Of Optical Channel Waveguides Research Articles

Fabrication of optical channel waveguides in crystals and glasses using macro- and micro ion beams

Active and passive optical waveguides are fundamental elements in modern telecommunications systems. A great number of optical crystals and glasses were identified and are used as good optoelectronic materials. However, fabrication of waveguides in some of those materials remains still a challenging task due to their susceptibility to mechanical or chemical damages during processing. Researches were initiated on ion beam fabrication of optical waveguides in tellurite glasses. Channel waveguides were written in Er:TeO2–WO3 glass through a special silicon mask using 1.5MeV N+ irradiation. This method was improved by increasing N+ energy to 3.5MeV to achieve confinement at the 1550nm wavelength, too. An alternative method, direct writing of the channel waveguides in the tellurite glass using focussed beams of 6–11MeV C3+ and C5+ and 5MeV N3+, has also been developed. Channel waveguides were fabricated in undoped eulytine-(Bi4Ge3O12) and sillenite type (Bi12GeO20) bismuth germanate crystals using both a special silicon mask and a thick SU8 photoresist mask and 3.5MeV N+ irradiation. The waveguides were studied by phase contrast and interference microscopy and micro Raman spectroscopy. Guiding properties were checked by the end fire method.

Femtosecond laser writing of multifunctional optical waveguides in a Nd:YVO_4+KTP hybrid system

We report on the fabrication of optical channel waveguides supporting both visible and IR TE and TM confinement in a hybrid system composed of a Nd:YVO4 laser gain medium glued to a potassium titanyl phosphate (KTP) nonlinear crystal. The microphotoluminescence and second harmonic confocal images of the fabricated waveguides have revealed that the laser and nonlinear properties of the constituent crystals have not been deteriorated because of the waveguide inscription. The resulting structures emerge as promising candidates for the development of multifrequency waveguide lasers.

Proton-implanted optical channel waveguides in Nd : YAG laser ceramics

We report on the fabrication of optical channel waveguides in Nd : YAG ceramics by multi-energy proton implantation at a total dose of 8 × 1016 ions cm−2. The modal distribution of the guided modes obtained from numerical calculation was in good agreement with the experimental result. The propagation loss of the waveguide was determined to be ∼4 dB cm−1 after post-annealing up to 400 °C in air. Confocal micro-photoluminescence experiments have revealed relevant changes in the Nd spectroscopic properties in the waveguide's active volume. These changes include line broadening and shifting as well as a clear luminescence quenching, which were attributed to the strong structural modifications induced by the high-dose proton implantation.

Ion-implanted optical channel waveguides in neodymium-doped yttrium aluminum garnet transparent ceramics for integrated laser generation

We report, for the first time to our knowledge, on the fabrication of optical channel waveguides in neodymium-doped yttrium aluminum garnet transparent ceramics by oxygen implantation. The fabricated waveguides show reduced propagation losses (1.5 dB/cm), as well as the possibility of waveguide-mode tailoring. The confocal fluorescence images of the channel waveguides reveal that oxygen implantation causes only slight changes in the fluorescence properties of neodymium ions making the fabricated structures promising candidates for integrated laser sources in the infrared bands.

Buried channel waveguides in Yb-doped KY(WO 4) 2 crystals fabricated by femtosecond laser irradiation

We report on the fabrication of optical channel waveguides inside KY(WO 4) 2 crystals, both undoped and Yb-doped, for applications in compact solid-state lasers and three-dimensional photonic devices. Nonlinear absorption of femtosecond laser pulses has been employed in order to induce refractive-index changes in these crystals. The irradiation damage results in a decrease of the material density compared to the surrounding bulk. In this work, two types of buried channel waveguides have been fabricated in the KY(WO 4) 2 crystals. First ones (type I) were formed in the vicinity of the irradiated regions due to the presence of an induced compressive lattice strain, which causes an increase of the local refractive index. Light can be better confined in the second (type II) of channel waveguides that are created between pairs of damaged regions. For the best confined channels (type II), the propagation loss value measured at 1 μm amounted to 2–2.5 dB/cm.

Photosensitivity and volume gratings in phosphate glasses for rare-earth-doped ion-exchanged optical waveguide lasers

Phosphate glasses containing enough sodium to allow the fabrication of optical channel waveguides by ion exchange are photosensitive to intense ultraviolet irradiation from excimer lasers at 193 and 248nm. Permanent submicrometer-period volume index gratings with modulation amplitudes larger than 10−4 were obtained even after annealing the irradiated samples for 2h at 230°C. Ultraviolet-visible absorption changes were measured in the irradiated areas, as well as structural modifications observed by surface profiling. Comparative studies were carried out for glasses that were also codoped with erbium and ytterbium to provide high gain at wavelengths near 1.5μm. Finally, we demonstrate narrowband gratings with reflectivities larger than 80% in silver ion-exchanged channel waveguides made in these phosphate glass substrates.

Systematic modeling study of channel waveguide fabrication by thermal silver ion exchange

A systematic study of thermal silver ion exchange used for the fabrication of optical channel waveguides is reported in a single-alkali glass. The diffusion equilibrium and diffusion dynamics are experimentally studied, and the concentration-dependent diffusion coefficients are determined. The relationship between the fabrication conditions, i.e., time, temperature, and melt concentration, and the induced waveguide refractive index profile is established. It is demonstrated that the diffusion equation can be solved, without use of any free parameters, to predict the refractive index profiles of both planar and channel waveguides. A 1.6 cm diameter integrated optic ring resonator, with a propagation loss of 0.1 dB/cm, is fabricated in a glass by thermal silver ion exchange. The induced refractive index profile is related to the optical characteristics of the functional device.

Fabrication of Silica-Based Glass Optical Waveguide by UV Beam Scanning

UV induced refractive index increase, the photosensitivity, in Ge-doped silica glass has been utilized for the fabrication of fiber Bragg gratings and long period fiber gratings. Recently, this phenomenon has also been applied to the fabrication of optical channel waveguides in order to achieve cost efficiency and fabrication flexibility. In this work, the fabrication of various optical waveguides by UV beam scanning is demonstrated. 10-mm-long straight optical waveguides and a Y-Branch waveguide with a branching ratio of nearly 50% are realized. We also propose and demonstrate a technique for the simultaneous fabrication of an optical waveguide and a Bragg grating by scanning UV beam through a phase mask.

UV‐written channel waveguides in Er 3+ ‐doped Bi 2 O 3 ‐based glass

The present paper describes the fabrication of optical channel waveguides in an Er3+-doped Bi2O3-based glass using direct laser writing with a UV beam at 244 nm. A buried positive refractive index change was achieved through this method and a description of the observed phenomena is given, based on optical and electron microscopy. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Direct ultraviolet writing of channel waveguides in congruent lithium niobate single crystals.

We report the fabrication of optical channel waveguides in congruent lithium niobate single crystals by direct writing with continuous-wave ultraviolet frequency-doubled Ar+ laser radiation (244 nm). The properties and performance of such waveguides are investigated, and first results are presented.

Texture developing in TiO 2/ORMOSIL composite sol–gel films by ECR etching

Composite waveguide film based on TiO 2/organically modified silane (ORMOSIL) has been synthesized through a sol–gel technique. Tetrapropylorthotitanate (Ti(OC 3H 7) 4) and ÿ-Glycidoxypropyltrimethoxysilane (GLYMO, [(CH 2OCH)CH 2O(CH 2) 3]Si(OCH 3) 3) were used as precursors for TiO 2/ORMOSIL composite films. Chain-like texture structure in the electron cyclotron resonance (ECR)-etched composite waveguide film was observed during the fabrication of optical channel waveguides. The morphology and structure were characterized by using scanning electron microscopy (SEM) and Fourier transforms infrared spectroscopy (FTIR). It is proposed that the formation of the texture structure be due to the induced polymerization of the GLYMO monomer in the presence of plasma or gas catalyst.

Simultaneous fabrication of optical channel waveguides and out-of-plane branching mirrors from a polymeric slab structure

Recently, polymeric multimode optical waveguides have been widely studied for low-cost interconnection use. We describe fabrication processes for a low-loss poly(methyl methacrylate) (less than 0.1 dB/cm at 675 nm) waveguide based on the reactive-ion-etching technique and for a slope (45 degrees mirror face) formed on the waveguide. To obtain a ridge core with a crack-free and extremely smooth surface, we applied a heating process at a temperature greater than the glass transition point and a smoothening process by solvent. Furthermore, to fabricate simultaneously both vertical and sloped sidewalls, we applied a unique phenomenon in the process that decreases the etching rate directly under a narrow opening of etching mask. By using the above fabrication techniques, we demonstrated an out-of-plane branching mirror.

Fabrication of Optical Channel Waveguides in the GaAs/AlGaAs System by Mev Ion Beam Bombardment

AbstractWe have fabricated optical channel waveguides in planar GaAs/AlGaAs waveguides using 10 MeV oxygen ions at a fluence of 3x1013 and 3x1014 ions/cm2. Although disordering of GaAs/AlGaAs quantum well structures has previously been reported, to the best of the authors' knowledge the fabrication of channel waveguides using high energy oxygen bombardment has not been demonstrated in this material system. This technique may provide a totally new concept of localized material modifications in GaAs/AlGaAs waveguides by creating compositional disordered regions that act as optical confinement channels. The masking technique used to provide selective disordering of the planar waveguide structures will be presented. Optical measurements were performed on the channel waveguides at a wavelength of 1.3 μm.

Use of a rapid thermal annealing system to initiate indiffusion for fabrication of Ti:LiNbO_3 optical channel waveguides

A rapid thermal annealing (RTA) system has been used to initiate indiffusion of Ti into LiNbO(3) for fabrication of optical channel waveguides. Four separate processes are investigated, each with different RTA temperature vs time variations followed by furnace heating. The sample processed with a fast initial ramp of temperature vs time to 875 degrees C yielded the lowest waveguide propagation loss of 1 dB/cm at a wavelength of 632.8 nm, compared with samples processed with other RTA variations and with a sample undergoing only furnace processing. Use of a dry O(2) ambient during RTA resulted in a smoother waveguide surface with no outdiffusion, when compared with use of a wet O(2) ambient.