Optical channel waveguides with trapezoidal-shaped cross sections in KTiOPO4 crystal fabricated by ion implantation

Optical channel waveguides were fabricated in KTiOPO₄ crystal by He⁺-ion implantation using photoresist masks with wedged-shaped cross sections. Semi-closed barrier walls with reduced refractive indices inside the crystal constructed the enclosed regions to be channel waveguides with trapezoidal-shaped cross sections. The m-line as well as end-fire coupling arrangements were performed to characterize the waveguides with light at wavelength of 632.8 nm. The propagation loss of the channel waveguides was determined to be as low as ∼2 dB/cm after simple post-irradiation thermal annealing treatment in air.     

Characterization of optical planar waveguide in Ce:KNSBN crystal formed by triple-energy helium ion implantation

We report on the optical planar waveguide formation and modal characterization in a Ce:KNSBN crystal by triple helium ion implantation at energies of (2.0, 2.2 and 2.4 MeV) and fluences of (1.5, 1.65 and 2.25) × 10¹⁵ cm⁻². The prism-coupling method is used to investigate the dark-line spectroscopy at wavelength of 632.8 and 1539 nm, respectively. The refractive index profiles of the waveguide are reconstructed by an effective refractive index method. It is found that the ion-beam irradiation creates slight increase of extraordinary index whilst decreases ordinary one in the guide region. The modal analysis shows, at wavelength of 632.8 nm, the fields of one TE and three TM modes are well restricted in the guiding region, which means the formation of non-leaky waveguide in the crystal. The damping coefficients of the waveguide are 0.6 and 1.6 cm⁻¹ for ordinary and extraordinary polarized light at 632.8 nm, respectively.     

Characterization of laser waveguides in Nd:CNGG crystals formed by low fluence carbon ion implantation

We report on Nd:CNGG active planar waveguides produced by 6.0 MeV carbon ion implantation at fluence from 1 × 10¹⁴ ions/cm² to 8 × 10¹⁴ ions/cm². The refractive index profiles, which were reconstructed according to the measured dark mode spectroscopy, showed that the refractive indices had negative changes in the surface region, forming typical barrier waveguide. The width of waveguide structure induced by carbon ion implantation is ∼3.8 μm. The typical barrier-shaped distribution may be mainly due to the nuclear energy deposition of the incident ions into the substrate. By performing a modal analysis on the observed TE modes, it was found that the TE₀ and TE₁ modes can be well-confined inside the waveguide.     

Laser emission in Nd:YVO<Subscript>4</Subscript> channel waveguides at 1064 nm

In this work, we report 1064 nm laser emission in Nd:YVO₄ channel waveguides fabricated by carbon implantation. Typical threshold pump powers (∼808 nm) were ≥45 mW. Maximum conversion efficiency was 11.5% (29.6% slope efficiency), and up to 9 mW of signal was delivered. Sample lengths of 4 mm were sufficient to completely absorb the pump power. The special spectral characteristics of this material such as broad absorption band and superior cross sections compared to the YAG crystal makes it suitable for developing compact sources to be integrated in optoelectronic devices.     

Low‐dose ion implanted active waveguides in Nd3+ doped near‐stoichiometric lithium niobate: promising candidates for near infrared integrated laser

By applying low‐dose oxygen ion implantation, active planar waveguides in Nd³⁺ doped near‐stoichiometric lithium niobate laser crystals have been, for the first time to our knowledge, successfully produced. The waveguide exhibits good transmission properties with relatively low propagation loss of ～2 dB/cm. The confocal micro‐luminescence investigations indicate that the emission properties of Nd³⁺ ions in the waveguide are well preserved with respect to the bulk, thus showing promising potentials for efficient waveguide laser action operating at the Nd³⁺ near‐infrared bands. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Packing density of conventional waveguides and photonic crystal waveguides

We compare coupling between parallel waveguides within one-dimensional photonic crystals and coupling between conventional waveguides. We consider the situation in which coupling between the waveguides is minimized, so that light in the waveguides propagates essentially independently. Subject to this condition, we compare the minimum mutual distance between conventional planar waveguides and waveguides in one-dimensional photonic crystals. We find that the packing densities of the conventional and periodic structures are comparable.     

Design, Fabrication, and Measurement of Two-Dimensional Photonic Crystal Slab Waveguides

Two-dimensional photonic crystal slab waveguides on SOI wafer are designed and fabricated. Photonic band gap, band gap guided mode, and index guided mode are observed by measuring the transmission spectra. The experimental results are in good agreement with the theoretical ones.     

Reconstruction of extraordinary refractive index profiles of optical planar waveguides with single or double modes fabricated by O ion implantation into lithium niobate

A method named intensity calculation method (ICM), which is based on beam propagation method (BPM) and image processing, was carried out to reconstruct the extraordinary refractive index profile (RIP) of single-mode planar waveguide in lithium niobate (LiNbO₃), which was fabricated by multi-energy megaelectron-volt (MeV) O²⁺ ion implantation. In addition, it has been proved reasonable that the alternation of extraordinary refractive index induced by ion implantation into LiNbO₃ is mainly due to the degradation of polarization and reduction of material physical density. As a result, the possible extraordinary RIP of the double-mode planar waveguide could be reconstructed using BPM according to such a hypothesis and the calculated guiding mode values. The end-fire coupling and m-line arrangements were carried out to obtain the near-field modal patterns and dark-mode spectra of waveguides, respectively.     

An He-implanted optical planar waveguide in an Nd:YGG laser crystal preserving fluorescence properties

We report the formation of a planar waveguide in an Nd:YGG laser crystal by low-energy He-ion implantation at liquid nitrogen temperature (77 K). The optical properties are measured by the prism coupling and end-face coupling methods, the absorption properties the waveguide and Nd:YGG substrate are obtained. The fluorescence spectrums are investigated by confocal methods. The experimental results revealed that the planar waveguide preserved the absorption and fluorescence properties of the Nd:YGG laser crystal. Thus, the planar waveguide formed by the ion implantation method is a promising candidate in waveguide lasers.     

Characterization of optical waveguide in Nd: LuVO4 crystals by triple-energy oxygen ion implantation

We report on the optical planar waveguide formation and modal characterization in Nd:LuVO₄ crystals by triple-energy O³⁺-ion implantation at energies of 2.4, 3.0, and 3.6 MeV and doses of 1.4, 1.4, and 3.1×10¹⁴ ions/cm², respectively. The prism-coupling method is used to investigate the dark-mode property at a wavelength of 633 nm. The refractive index profiles of the waveguide are reconstructed by the reflectivity calculation method (RCM). The modal analysis shows that the fields of TE modes are well restricted in the guiding region, which indicates the formation of non-leaky waveguide in the crystal.     

Vertically and laterally waveguide-coupled cylindrical microresonators in Si3N4 on SiO2 technology

High-finesse laterally and vertically waveguide-coupled cylindrical microresonators have been designed and realized in Si₃N₄ on SiO₂ technology using conventional optical lithography. Based on the experimental results and detailed simulations, a comparison between the lateral and vertical coupling schemes is made. Received: 16 May 2001 / Revised version: 13 August 2001 / Published online: 2 November 2001     

Efficient blue upconversion emission due to confined radiative energy transfer in Tm-Nd co-doped Ta2O5 waveguides under infrared-laser excitation

Intense blue upconversion emission at 480 nm has been obtained at room temperature in Tm³⁺-Nd³⁺ co-doped Ta₂O₅ channel waveguides fabricated on a Si substrate, when the sample is excited with an infrared laser at 793 nm. The upconversion mechanism is based on the radiative relaxation of the Nd³⁺ ions (⁴F_3/2 → ⁴I_11/2) at about 1064 nm followed by the absorption of the emitted photons by Tm³⁺ ions in the ³H₄ excited state. A coefficient of energy transfer rate as high as 3 × 10⁻¹⁶ cm³/s has been deduced using a rate equation analysis, which is the highest reported for Tm-Nd co-doped systems. The confinement of the 1064 nm emitted radiation in the waveguide structure is the main reason of the high energy transfer probability between Nd³⁺ and Tm³⁺ ions.     

Vector modes of rectangular-core dielectric waveguides: An improved perturbation approach

We present an improved analysis to obtain vector modes of a rectangular-core waveguide (RCW) structure whose dielectric constant profile is separable in x and y coordinates. Using this analysis, a perturbation method is then developed to obtain vector modes of a practical RCW. The propagation constants so obtained for a fully-buried and a ridge RCW structure using the present analysis are found to be in better agreement with reported numerical values than the ones obtained with an earlier reported perturbation approach [Kumar et al., Opt. Lett. 8 (1983) 63].     

Property study of Si + -ion-implanted Nd:YVO 4 waveguides

Planar waveguides were formed in Nd:YVO₄ crystals by 3.0-MeV Si⁺-ion implantation at doses of 1×10¹³–1.5×10¹⁵ ions/cm² at room temperature. The effective refractive indices of the waveguide propagation modes were measured by using a prism-coupling method. It was found that the number of the propagation modes is dependent on the doses for the waveguides in Nd:YVO₄. The atom displacement in the near-surface region (about 2 μm beneath the surface) of the Nd:YVO₄ crystal induced by the implantation was simulated by using the TRIM 98 (transport and range of ions in matter) code. The possible reasons for the waveguide formation are discussed in a primary way. Received: 17 July 2002 / Revised version: 20 September 2002 / Published online: 11 December 2002 RID="*" ID="*"Corresponding author. Fax: +86-531-8565167, E-mail: drfchen@sdu.edu.cn     

Improved determination of phosphorus contamination during ion implantation by SRP and simulations

Experimental determination of phosphorous cross-contamination during antimony implantation is presented. As a suitable structure for this experiment, a buried layer was employed which is created by implanting antimony followed by a long diffusion process. The implanted samples were analysed by SIMS and spreading resistance (SRP) methods. SRP method has been improved by applying a correction for the carrier spilling effect. A conversion chart for p-n junction depth dependence on phosphorus doping has been calculated by program SUPREM-IV. Comparison of SRP and SIMS methods has shown that SRP method can be used for monitoring the phosphorus cross-contamination and can be easily implemented as an in-line monitor and present an alternative to expensive and time consuming SIMS analysis.     

Determination of phosphorus contamination during antimony implantation by measurement and simulation

Experimental determination of phosphorus cross-contamination during antimony implantation is presented. As a suitable structure for this experiment, a buried layer was employed which is created by implanting antimony followed by a long diffusion process. The samples implanted in different implanters were analysed by secondary ion mass spectrometry (SIMS), four-point probe and spreading resistance methods. The obtained results were compared with those calculated by program SUPREM-IV. Methods that can and cannot be used to determine phosphorus contamination during antimony implantation and to estimate the fluence of phosphorus being co-implanted with antimony are described in detail.     

Thermal fixing of holographic gratings in planar LiNbO3:Ti:Fe waveguides

3 :Ti:Fe waveguides are thermally fixed during hologram recording at elevated temperatures. Different guides are fabricated by titanium indiffusion using iron-doped and nominally pure y-cutLiNbO₃ substrates and characterization is performed by dark-mode spectroscopy. The refractive index modulation of gratings written and simultaneously fixed at 180 °C is investigated as a function of propagation depth, titanium and iron concentration. The experimental results are compared with those obtained for unfixed holograms recorded at room temperature. Received: 21. July 1997/Revised version: 13 October 1997     

Comparison of the electro-optic coefficient r33 in well-defined phases of proton exchanged LiNbO3 waveguides

The electro-optic coefficient, r₃₃, of proton exchanged LiNbO₃ waveguides has been measured in well-defined phases of the exchanged layer. Namely, in two low index-jump α-phases, i.e. unannealed soft-exchanged (SPE) and annealed (APE) guides, and in two high index-jump phases, i.e. β₁ guides and, for comparison, ordinary proton exchanged (PE) guides (having a mixture of phases). The following values have been obtained (in pm/V): 22.1±0.6 for SPE; 20.9±0.7 for APE; 0.33±0.01 for β₁; and 0.76±0.04 for PE. Differences between these values are discussed in terms of the structure of the phase involved. Received: 18 May 2001 / Revised version: 22 August 2001 / Published online: 30 October 2001     

Self-guiding of infrared and visible light in photonic crystal slabs

We experimentally demonstrate diffractionless guidance and efficient routing of light in two-dimensional photonic crystal slabs at infrared and visible wavelengths. Our particular design allows for simultaneous guidance of TE and TM polarized light beams at the same wavelength. Routing performance and possibilities of propagation loss reduction are investigated experimentally. Experimental results are in excellent agreement with three-dimensional simulations.