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Diffusivity of Er3+ into LiNbO3 crystal has been studied as a function of Li2O content and crystal orientation. The Li2O content in single-crystal LiNbO3 plates was adjusted by Li-rich vapor transport equilibration (VTE) technique. Five X-cut and five Z-cut congruent substrates were VTE treated at first at 1100 °C for different durations ranging from 6 to 74 h, and then were subjected to a special post-VTE anneal procedure at the same temperature for 60 h to obtain homogeneous Li2O content. The Li2O content was determined from the measured fundamental optical absorption edge. Its homogeneity is verified by measuring the optical absorption edge as a function of the crystal thickness. After the composition characterization, the substrates were coated with 45 nm thick Er film and annealed at 1130 °C for 40 h in argon atmosphere. The Er3+ profile was analyzed by secondary ion mass spectrometry. The results show that the Er3+ diffusivity decreases monoexponentially with the increase in the Li2O content in both cases of X- and Z-cut. As the Li2O content is increased from the congruent point (48.4 mol %) to the near-stoichiometric composition (∼49.9 mol %), the diffusivity decreases from 0.107 (0.072) to 0.017 (0.018) μm2/h for the Z (X)-cut substrate. The diffusion shows considerable anisotropy for the lower Li2O content and the diffusivity in a Z-cut substrate is larger. The anisotropy weakens gradually with the increase in the Li2O content, and the diffusivities in the X- and Z-cut substrates ultimately tend to a same value (∼0.02 μm2/h) at the Li-rich phase boundary. After the Er diffusion procedure, endface coupling experiment was carried out to check if a planar waveguide layer was formed near the Er-diffused surface due to the Li outdiffusion. The results show that the Li outdiffusion did not accompany the Er diffusion procedure. [ABSTRACT FROM AUTHOR]

Buried channel waveguide amplifiers in erbium/ybtterbium codoped phosphate glass were fabricated using proton-beam writing. Single-mode waveguides were fabricated with fluences ranging from 0.4 to 2.0×1015 particles/cm2. The end-of-range and surface profiles of the waveguides were investigated using atomic force microscopy. The waveguiding effect was investigated using the end-fire coupling technique. From the near-field mode profiles, the refractive index profiles of these waveguides were recovered using the propagation mode near-field method. From these results, it can be deduced that for phosphate glass waveguides fabricated with fluences <1.0×1015 particles/cm2, the ionization from the electronic stopping, rather than the nuclear damage processes, is the major contributing factor leading to an increase in the refractive index near the end of range. [ABSTRACT FROM AUTHOR]

Discusses a study which characterized fabricated waveguides in iron doped KTiOPO[sub4] substrates. Background on the sample materials; Methodology; Findings.

The variational method is proposed to analyze the influence of the fabrication parameters on the performance of buried K+–Na+ ion-exchanged Er3+–Yb3+ ions co-doped glass waveguide. The unknown parameters of the Hermite–Gaussian functions as the trial field distribution are determined based on the scalar variational principle. It is demonstrated that the results calculated in this paper agree with those measured in the experiment. The mode dimensions, the effective refractive index, and the overlap factor as the functions of the fabrication parameters are investigated. These results of the variational analysis are useful for the design and optimization of Er3+–Yb3+ ions co-doped waveguides. [ABSTRACT FROM AUTHOR]

Secondary-ion-mass spectrometry was applied to study Ti-concentration profiles in the depth direction and on the surface of near-stoichiometric (NS) Ti:LiNbO3 strip waveguides fabricated using vapour transport equilibration (VTE) and co-diffusion of Ti-metal strips. Results show that the profile of Ti concentration along the width direction on the waveguide surface can be well fitted by a sum of two error functions, while, in the depth direction, the Ti concentration follows either a complementary error function or a generalized Gaussian function. Surface Ti concentration, 1/e width and depth, mean diffusivities along the width and depth directions of the guide are, respectively, 1.04 × 1021 cm–3, 8.5 µm, 6.3 µm, 0.18 and 0.1 µm2/h. Two-dimensional refractive index profile in the NS waveguides is indirectly constructed by assuming linearity between Ti-induced index change and Ti concentration. The surface refractive index increments at 1545 nm, Δno and Δne, are evaluated to be 3.132 × 10–3 and 1.186 × 10–2, respectively. All of the above-mentioned diffusion and optical parameters are compared with the corresponding data of the common congruent Ti:LiNbO3 waveguide or NS waveguide fabricated starting from a NS substrate. The rationality of the assumed linear relationship between the index change and the Ti concentration is discussed. The results show that the assumed linearity remains controversial, and all expressions and data with regard to the refractive index are the approximate results and need to be verified by direct measurement on refractive index. [ABSTRACT FROM AUTHOR]

The newly synthesized polymer, bisphenol A-aldehyde resin (BPA-resin) has many unique thermo-optical characteristics. The polymer has high transparency, relatively high refractive index, low birefringence, and large thermo-optics coefficient at the optical telecommunication wavelengths. Also, the single-mode channel waveguides have been fabricated using BPA-resin polymer. The experimental results show, that the polymer waveguide has a low propagation loss of 0.43 and 0.51 dB/cm at a wavelength of 1.31 and 1.55 µm, respectively, for both TE and TM polarizations. The low polarization dependence loss (PDL) of the waveguide was less than 0.1 dB/cm at above wavelengths, which can be applied in thermal-optical tuned devices. [ABSTRACT FROM AUTHOR]

A new-type flat-field arrayed waveguide grating (AWG), with the focal signals of all wavelengths of operation focusing along a straight line, has been designed. The work bases on the aberration theory of AWG, in which the restraints imposed on the conventional Rowland-type AWG have been released. In the design of flat-field AWG, three stigmatic points restrain three dominant geometry parameters: geometry of star couplers, ports distribution of phased-array, and length increment between adjacent paths. An eight-channel 200-GHz spacing flat-field AWG has been designed and simulated. As stigmatic points introduced, the aberration of this device is much lower than that of the Rowland-type AWG. [ABSTRACT FROM AUTHOR]

Er 3+ doped Na2O–Nb2O5–TeO2 (NNT) glasses suitable for making optical waveguide devices has been fabricated and characterized. Intense 1.53 μm infrared fluorescence and green upconversion luminescence were observed under 975 nm diode laser and 798 nm laser excitation. The optical absorption, the Judd–Ofelt parameters and the spontaneous transition probabilities have been measured and calculated. The quantum efficiency of 1.53 μm emission band is proved to be ~100%. The maximum emission cross-section is 1.02×10-20 cm2 at 1.533 μm, and it is more than 30% higher than the values in silicate and phosphate glasses. Under 798 nm excitation, strong green and weak red upconversion luminescence was observed at room temperature. The 546 nm green band shows a broad full-width at half-maximum of 16 nm. Intense and broad green upconversion fluorescence in Er 3+ doped NNT glass can be used in colour display, undersea communication and infrared sensor. High concentration of Na2O is a benefit to developing waveguide device from the glass. [ABSTRACT FROM AUTHOR]

Annealing properties of proton-exchanged optical waveguides in z-cut LiNbO3 fabricuted using toluic acid are reported. Variations in the surface refractive index and waveguide depth with annealing time are found to follow a power-taw relationship, and a minimum propagation loss of 0.23 dB/cm is measured at 0.633-µm wavelength. [ABSTRACT FROM AUTHOR]

Annealing of proton-exchanged planar optical waveguides in z-cut LiNbO3 fabricated using stearic acid has been studied systematically. The effects of annealing on waveguide propagation loss, surface index change, and waveguide depth were measured as a function of annealing time, and were found to follow a power-law relationship. [ABSTRACT FROM AUTHOR]

The article presents a computational method for calculating the electric potential and field distributions in a coupled coplanar waveguide with finite electrode thickness. This method provides a simple and fast approach to the quasistatic analysis of the structures. The same structure with infinitely thin electrodes is also analyzed using conformal-mapping techniques, and excellent agreement of the results is obtained between the two methods. [ABSTRACT FROM AUTHOR]

Europium (\Eu^3+)-doped deoxyribonucleic acid-cetyltrimethylammonium (DNA-CTMA) biopolymers have been prepared and characterized optically. Quartz capillary tube encapsulated \Eu^3+-doped biopolymeric waveguides have been fabricated via a simple withdrawal molding technique. Optical amplification at 612-nm wavelength has been demonstrated in these waveguide devices, and the signal enhancements for different lengths of the devices have been measured. A maximum signal enhancement of 24 dB has been obtained for a 15-mm-long device. [ABSTRACT FROM PUBLISHER]

Compact 1×4 multimode interference splitter with tapered sections has been designed and fabricated based on deoxyribonucleic acid-cetyltrimethylammonium biopolymer material. A multistep processing and reactive ion etching technique have been developed to fabricate the device. There is excellent agreement between experimental and theoretical results and the splitter exhibits low excess loss, negligible polarization dependent loss, and well output uniformity for both TE and TM modes at 1550 nm wavelength. [ABSTRACT FROM AUTHOR]

Signal amplification at the polymer optical fiber low-loss window of 650 nm is reported in an SU8 rib waveguide coated with Rhodamine-640 doped poly(methyl methacrylate). A signal beam is end-fired into the facet of a 7×100 μm waveguide and amplified by top pumping of the 2-μm-thick cladding region with a pulsed pump source focused into a 9-mm-long stripe. A gain of 14dB and a minimum signal-to-noise ratio of around 2 dB are achieved in a 15-mm-long device with a low threshold pump intensity of 0.25 μJ/mm2, which is an order of magnitude lower than previously reported. [ABSTRACT FROM AUTHOR]

Polymer channel waveguide amplifier arrays were fabricated using ultraviolet direct printing methodology. The effects of different weight percentage (wt. %) combinations of rare-earth ions erbium (Er3+) and ytterbium (Yb3+) on the absorption spectrum, as well as the internal gain, were investigated. With an input signal power of ∼-18 dBm, the highest internal gain obtained is ∼16.5 dB at a wavelength of 1533 nm for a 20 mm long multimode channel waveguide codoped with ∼1 wt. % of Er3+ and ∼10 wt. % of Yb3+ derivatives. The UV direct printing methodology opens a simple platform for the fabrication of dense and compact polymer waveguide laser arrays. [ABSTRACT FROM AUTHOR]

Near-stoichiometric planar and strip LiNbO3 optical waveguides were demonstrated using vapor transport equilibrium process and co-diffusion of titanium metal. Optical confinement is better in z-cut substrates than in x-cut substrates, and the waveguides were characterized optically. Spectral measurements, such as OH- absorption, optical absorption near the fundamental edge, and Raman scattering, were carried out to examine the Li-composition and crystalline phase inside and outside the guiding layer. The results have shown that the vapor transport equilibration process has brought these waveguides toward stoichiometric composition, the Li content inside and outside the waveguide layer is essentially identical, and the LiNbO3 phase is still retained within the waveguide layer. [ABSTRACT FROM AUTHOR]

Polymeric waveguide wavelength filters based on a low-loss negative tone epoxy Novolak resin polymer have been fabricated using electron-beam direct writing. Both the waveguides and the gratings were exposed simultaneously, which effectively eliminate the alignment errors that can be generated during fabrication. A first-order Bragg grating around 1550 nm wavelength was used, and a transmission peak of -27 dB was obtained with a 5 mm long grating length, corresponding to >99% reflection. The 3 dB transmission bandwidth was found to be ∼0.8 nm and the 10 dB bandwidth was ∼1.0 nm. Dependence of the Bragg wavelength on electron-beam dosage and waveguide width was also investigated.© 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Low-loss optical waveguides based on a negative tone epoxy Novolak resin polymer have been fabricated using electron-beam direct writing. This polymer has a high refractive index, high sensitivity, large hardness, and T[sub g]>200 °C. For single-mode channel waveguides with upper claddings, the propagation losses measured were 0.22 and 0.48 dB/cm at 1330 and 1550 nm, respectively. For waveguides without upper claddings, the losses were 0.5 dB/cm at both wavelengths. The stability of these waveguides was also investigated, and no significant change was observed after 200 h at 90 °C and 95% relative humidity. [ABSTRACT FROM AUTHOR]

Abstract: Efficient infrared emissions at ~ 1.2 and ~ 2.0 µm were recorded in Ho3+-single-doped and Ho3+/Yb3+-co-doped aluminum germanate glasses (NMAG), respectively. The maximum stimulated emission cross-sections for the ~ 1.2- and ~ 2.0 µm emissions were derived to be 2.3 × 10−21 and 5.8 × 10−21 cm2, respectively; then the gain cross-sections were further evaluated and the effective gains have been anticipated. In addition, the channel waveguide fabricated by K+-Na+ ion-exchanged method exhibited a complete single mode at 1.55 µm and the field diameters were identified to be horizontally 10.6 µm and vertically 6.7 µm. Effective amplified spontaneous emission at ~ 2.0 µm was recorded under 980 nm laser pumping. Broad bandwidth, large emission cross-section and perfect thermal ion-exchangeability indicate that Ho3+- and Yb3+-doped NMAG glasses are promising for the development of optical amplifier, tunable laser and light source operating at ~ 1.2 and ~ 2.0 µm.Graphical abstract: [ABSTRACT FROM AUTHOR]