Formation Of Optical Waveguides Research Articles

Formation of optical planar waveguides on fused quartz by MeV ion implantation

AbstractThe optical losses and the refractive index change of optical planar waveguides formed by MeV ion implantation were correlated with the experimental ion implantation parameters. Direct ion implantation was performed by means of carbon, silicon and copper ion beams impinging on the substrate surface at normal incidence. The ions were accelerated at energies ranging from 3 to 12 MeV with fluences varying from 1 × 1012 to 2 × 1016 ion/cm2, according to the type of implanted ion. The modification of the substrate refractive index due to the ion irradiation‐induced damage was evaluated using the prism coupler method, and the refractive index profiles were determined by means of a reconstruction method using a multilayer structure approximation. The guiding properties of the waveguides were analysed using the fibre‐coupling technique to determine both the optical transmission and transversal modes at 635 nm. The main practical relevance of our research is the obtention of high‐quality waveguides at low current density MeV ion implantation (≤80 nA/cm2) without post‐implantation annealing.

Optical properties of the proton-implanted waveguide in the Dy3+-doped Y3Al5O12 transparent ceramic

The high-quality waveguide structure in the Dy[Formula: see text]-doped Y3Al5O[Formula: see text] transparent ceramic is of significance for the application of integrated micro-light elements. However, there have been no reports on the preparation of optical waveguides by ion implantation in the Dy[Formula: see text]-doped Y3Al5O[Formula: see text] transparent ceramic. The work reports on the formation of optical planar waveguides by using the proton implantation in the Dy[Formula: see text]-doped Y3Al5O[Formula: see text] transparent ceramic. The acceleration energy and the dose of the protons are 400[Formula: see text]keV and [Formula: see text] ions/cm2, respectively. The structure of the fabricated waveguide is captured with the high-res/mag images by a metallurgical microscope. The dark-mode spectrum and the refractive index distribution are gained by the prism coupling system and the RCM software, respectively. The measurement and simulation of the near-field intensity distribution indicate the propagation of light field in the waveguide. The results are of potential to the compact devices in the photonics.

Optical Waveguides Fabricated via Femtosecond Direct Laser Writing: Processes, Materials, and Devices

AbstractAs the most fundamental unit of photonic integration, optical waveguides offer the possibility of developing efficient and practical photonic chips by facilitating the on‐chip integration of devices with different functions. Femtosecond direct laser writing (FsDLW), as a burgeoning 3D microfabrication technology, can realize the rapid formation of arbitrary optical waveguides without any mask inside versatile materials, such as crystalline dielectric crystals, glasses, polymers, and photoresists. This significant material‐independence allows FsDLW to combine different materials and manufacturing processes to implement a cross‐platform solution. This review first describes the different optical loss types and suitable measurement methods for different applicable scenes, then summarizes the two fabrication mechanisms and points out the general direction for adjusting the waveguide properties by fabrication processes. Finally, the application fields and development prospects of different materials are discussed by overviewing the characteristics of different materials and the material selection preferences of different devices. With a panoramic view of the development, it is concluded with insights and perspectives of the future development of optical waveguides and processing technology via FsDLW.

Specific features of the formation of optical waveguides, contact pads and electrical interconnections on lithium tantalate substrates

The article considers the formation of titanium channel optical waveguides in LiTaO3 substrates. These structures were obtained by dry etching of grooves in SF6 plasma and magnetron sputtering of titanium film. After that, waveguides were formed by plasma etching using photoresist as mask. Technological features and modes of microstructure production are described. Al contact pads were produced by magnetron sputtering thin metal films on LiTaO3. Aluminum wires were ultrasonically bonded to Al contact pads using Delvotec 5630. The developed technology of formation of contact pads and bonding modes made it possible to obtain a bonded joint with a bond strength of 23-25 Gs.

Direct Inscription of on-surface waveguides in polymers using a mid-ir fiber laser.

A detailed study of photo-inscribed optical waveguides in PMMA and polycarbonate using a mid-IR laser is presented. The wavelength of the laser is tuned near the absorption peaks of stretching C-H molecular bonds and the focused beam is scanned onto the surface of planar polymer samples. For the first time, we report the formation of optical waveguides in both polymers through resonant absorption of the laser beam. The optical properties of the waveguides were thoroughly assessed. An elliptic Gaussian mode is guided at the surface of both polymers. Insertion losses of 3.1 dB for a 30 mm long on-surface waveguide inscribed in PMMA were recorded. Such waveguides can interact with the external medium through evanescent coupling. As a proof of concept, the surface waveguides are used as highly sensitive refractometric sensors. An attenuation dynamical range of 35 dB was obtained for a liquid that matches the index of the PMMA substrate. Our results pave the way for large scale manufacturing of low cost biocompatible photonic devices.

The formation and characterization of optical waveguide in Nd:YLF crystal by 4.5-MeV Si ion implantation

The planar waveguides have been fabricated in Nd:YLF crystals by Si implantation. The guiding properties of Si-implanted waveguide are evaluated by the prism-coupling technique and reflectivity calculation method (RCM), exhibiting good confinement and monomode behavior at 632.8 nm. The investigation of the photoluminescence (PL) measurement demonstrates that the luminescence characteristics of the Nd3+ ions are not significantly altered by the Si ions irradiation process, whereas the up-conversion (UC) luminescence intensity can be effectively improved. Based on the pump-power-dependent fluorescence, the possible emission mechanism in Nd:YLF is proposed.

ОСОБЕННОСТИ СТРУКТУРНО-ФАЗОВЫХ ПРЕВРАЩЕНИЙ ПРИ ОТЖИГЕ ПРОТОНООБМЕННЫХ СЛОЕВ НА Z-СРЕЗЕ КРИСТАЛЛА НИОБАТА ЛИТИЯ

С использованием методов оптической микроскопии в поляризованном свете, модовой спектроскопии, ИК-спектроскопии и рентгеноструктурного анализа подтверждена последовательность фазовых превращений, происходящих при отжиге протонообменных слоев на Z-срезе кристалла ниобата лития: b2-, b1-фазы ® k2-фаза ® k1-фаза ® α-фаза. Установлено, что в процессе отжига в ходе фазовых превращений когерентность слоев, образованных из различных фаз, не нарушается, что обусловлено меньшей величиной деформаций (напряжений) формирующихся протонообменных фаз по сравнению с деформациями (напряжениями) на X-срезе кристалла. 
 Работа выполнена при финансовой поддержке гранта РФФИ (проект № 17-43-590309 р_а).

Effect of He+ ion implantation on Rb+-K+ exchanged KTiOPO4 optical waveguide

We report on the effect of 500 keV He[Formula: see text] ion implantation with a fluence of [Formula: see text] ions/cm2 on Rb[Formula: see text]-K[Formula: see text] ion exchanged KTiOPO4 optical waveguide. The refractive index distribution after ion implantation, ion exchange, and ion implantation and subsequent ion exchange were reconstructed by reflectivity calculation method, inverse Wentzel–Kramers–Brillouin, and intensity calculation method, respectively. The near field intensity distribution of the waveguides was simulated by Beam Propagation Method. The phase analysis of the samples was measured by X-ray diffraction technique. The damage layer formed in the depth of maximum nuclear energy deposition by ion implantation acts as a barrier to block the ions diffusion into the sample. Results exhibit that ion implantation and subsequent ion exchange are effective means for optical waveguide formation.

Integrated waveguides and deterministically positioned nitrogen vacancy centers in diamond created by femtosecond laser writing.

Diamond's nitrogen vacancy (NV) center is an optically active defect with long spin coherence times, showing great potential for both efficient nanoscale magnetometry and quantum information processing schemes. Recently, both the formation of buried 3D optical waveguides and high-quality single NVs in diamond were demonstrated using the versatile femtosecond laser-writing technique. However, until now, combining these technologies has been an outstanding challenge. In this Letter, we fabricate laser-written photonic waveguides in quantum grade diamond which are aligned to within micron resolution to single laser-written NVs, enabling an integrated platform providing deterministically positioned waveguide-coupled NVs. This fabrication technology opens the way toward on-chip optical routing of single photons between NVs and optically integrated spin-based sensing.

Comparative analysis of ways for femtosecond laser formation of optical waveguides

Comparative analysis of ways for femtosecond laser formation of optical waveguides

Formation of channel optical waveguides in polymethylmethacrylate with embedded electro-optic chromophore DR13 by the photoinduced bleaching method

A composite polymeric material based on polymethylmethacrylate (PMMA) with embedded electro- optical (EO) chromophore DR13 is designed. Irradiation with electromagnetic radiation in the visible range leads to a bleaching of the composite and its refractive index n decreases due to the irreversible photodestruction of the chromophore. Changes in the absorption spectrum and refractive index of the composite with the irradiation time are measured. It is shown that the change in n depends on the concentration of DR13 in the polymer matrix and can reach a value of Δn = 0.034 in the telecommunication C-range near a wavelength of 1.55 μm. The rate of bleaching depends on the wavelength of the actinic light and reaches its maximum when the wavelength is near the maximum of chromophore absorption. With the use of the photobleaching method and the PMMA/DR13 composite, channel waveguides and the other elements of the integrated optical devices are fabricated, including waveguide splitters, directional couplers, and Mach–Zehnder interferometers. This simple one-step method does not involve the removal of polymer material by liquidphase or reactive ion etching.

Optical Formation of Waveguide Elements in Photorefractive Surface Layer of a Lithium Niobate Sample

Formation of channel optical waveguides due to the sequential point-to-point exposure of local stripe-like regions of Y-cut lithium niobate sample surface is experimentally investigated. The surface layer of the sample is thermally doped with Cu ions to increase its photorefractive sensitivity. The laser radiation with wavelength of 532 nm and optical power of 10 mW is used for the crystal exposure in experiments. The optical inhomogeneities formed during the sample exposure are studied with their probing by laser beams with wavelength of 633 nm.

Formation of Crystalline Si Optical Waveguides on Bulk (100) Si Substrate as a New Platform for On-Chip Interconnect Applications

Lightwave transmission is a promising candidate for data interconnections, including the short-distance data communication. The method by which photonics and electronics ought to be integrated is developing and not well resolved yet. In particular, the different requirements of buried oxide thickness for photonics and electronics hamper their integration on the same chip. In this paper, we present a crystalline Si-core waveguide as the platform of interconnection and proceed to investigate its characteristics. The Si-core of the waveguide on bulk (100) Si substrate is formed by an excimer laser system through shape reformation. The SiO2 cladding is later on created through oxidation process. Though the Si-core's shape has changed, it still preserves its monocrystalline properties, and displays a broadband transmission. This test shows several local defects along axial direction cause obvious scattering of the guided wave, and propagation loss is estimated to be about 7 dB/cm. We think the defects come from an observed wavy structure and this loss is improvable via our proposed methods. In addition, the core distance to substrate is adjustable and the sidewall roughness is good. Hence we proceed to analyze the losses theoretically. The various kinds of loss are potentially reducible to 1 dB/cm, except coupling loss on end facets, which is also improvable with the use of proper coupling devices. These demonstrate the potentiality of the platform for on-chip interconnect applications.

Damage evolution and waveguide formation in SrTiO3 crystal irradiated by tens of MeV Si ions

In this work, lattice damage behavior and optical waveguide formation in SrTiO3 crystal induced by swift ion irradiation have been studied. SrTiO3 crystal with (100) surface normal zone axis direction has been irradiated by 20MeV Si3+ ions with a fluence of 1×1015cm−2 at 300K. Subsequently, structural damage induced by nuclear or electronic energy loss processes along ion penetration path has been analyzed by complementary characterization techniques, and the results indicate that the produced lattice damage in this case should be attributed to the nuclear energy loss. Utilizing the change of refractive index in lattice damage region, waveguide structure has been successfully prepared and the related optical properties have been studied through various coupling techniques. The iWKB (inverse Wentzel-Kramers-Brillouin)-reconstructed refractive-index profile of irradiation region appears reasonable correspondence (symmetrical inversion) with SRIM-simulated dpa profile, which also proves that lattice damage and waveguide formation in SrTiO3 should be ascribed to the nuclear energy loss during tens of MeV Si-ion irradiation process.

Femtosecond laser direct inscription of surface skimming waveguides in bulk glass.

We present a detailed study of waveguide inscription near the surface of bulk glass using a femtosecond laser. Three silicate glasses used extensively as hosts for photo-induced photonic devices were examined. Our results show that near-surface waveguides generally present a low-index contrast, as the pulse energy damage threshold decreases sharply at close proximity to the surface. We devised a novel method to allow the formation of optical waveguides that exhibit a high-index contrast up to the surface of any transparent material. As a proof of concept, the inscription of near-surface single-mode waveguides operating at a wavelength of 405 nm is demonstrated.

Influence of chemical polymer composition on integrated waveguide formation induced by excimer laser surface irradiation

We show that the chemical composition and the amount of residual monomers in polymethylmethacrylate significantly affect the evolution of optical waveguide formation induced by UV surface irradiation. We employ an interferometric approach in Mach-Zehnder configuration to determine the refractive index depth profile in different planar polymethylmethacrylate materials. Our results reveal a distinctive different surface and buried waveguide formation for materials having different monomer content. In particular, we find that for smaller residual monomer content buried waveguide formation is less pronounced, which is in turn preferential for a selective light guidance in planar polymer structures. Attenuation measurements confirm a difference in attenuation coefficient of 0.5dB/cm.

Formation of luminescent optical waveguides in silicate glass matrix by the ion-exchange technique

We present spectra of the alkali-silicate glasses with copper ions in near-surface area, introduced by ion exchange of different temperature and duration. It is shown that the reduction of Cu2+ in the near-surface area causes existence of Cu+ and neutral atoms in glass after the ion-exchange in divalent salt. The ion-exchange itself involves only Cu+ and Na+ ions. The formation of subnanometer clusters Cun is due to neutral copper atoms staying in near-surface zone. We have shown that the waveguide layer in near-surface area, made by ion-exchange, has а visible luminescence with the excitation by UVradiation. At the same time, the contribution to luminescence is made by Cu+ ions, molecular clusters Cun and by dimers Cu+ - Cu+ . During the high-temperature ion-exchange at 600 °С the formation and destruction equilibrium shift of molecular clusters Cun can be seen. An hour ion-exchange leads to molecular clusters Cun destruction, while at time periods less than 30 min and around 18 hours it leads to the formation of Cun. The sample turns green after 18,5 hours ion-exchange showing formation of a considerable amount of divalent copper ions Cu2+ therein.

Specific features of the formation of optical waveguides in silicate glass at high energy and doze of electron irradiation

The formation of an optical waveguide in silicate glass that contains alkali-metal ions is experimentally studied under electron irradiation at an energy of 50 keV and a doze of 25–50 mC/cm2. A gradient waveguide with a maximum variation in the refractive index of 0.01–0.04 is formed in the glass due to irradiation. It is demonstrated that a variation in the refractive index results from both field migration of alkalimetal ions to the region of negative space charge and structural modifications in the glass related to the destruction of glass structure by high-energy electrons.

Thermal annealing property of KOTiPO_4 planar and ridge waveguides formed by MeV Si ion implantation

We report on the formation of KOTiPO4 optical ridge waveguide combined ion implantation and Ar-ion beam etching in this manuscript. We used 6 MeV silicon ion implanted into our samples with the fluence of 6 × 1014 ions/cm2, which is relative high values for both energy and fluence. The guided mode and light propagation properties were investigated by prism-coupling and end-face coupling method. Numerical simulation was performed based on the reconstructed 2D refractive index profile of waveguides cross section for comparison. We obtain non-leaky waveguide structure in nx direction after proper annealing treatment. The fabricated waveguide structures emerge as promising candidate for photonic design which will work at high temperature.

M-line spectroscopic, spectroscopic ellipsometric and microscopic measurements of optical waveguides fabricated by MeV-energy N+ ion irradiation for telecom applications

Irradiation with N+ ions of the 1.5–3.5MeV energy range was applied to optical waveguide formation. Planar and channel waveguides have been fabricated in an Er-doped tungsten–tellurite glass, and in both types of bismuth germanate (BGO) crystals: Bi4Ge3O12 (eulytine) and Bi12GeO20 (sillenite). Multi-wavelength m-line spectroscopy and spectroscopic ellipsometry were used for the characterisation of the ion beam irradiated waveguides. Planar waveguides fabricated in the Er-doped tungsten–tellurite glass using irradiation with N+ ions at 3.5MeV worked even at the 1550nm telecommunication wavelength. 3.5MeVN+ ion irradiated planar waveguides in eulytine-type BGO worked up to 1550nm and those in sillenite-type BGO worked up to 1330nm.