Ion-exchanged Waveguides Research Articles

Velocity distribution of Gold nanoparticles trapped on an optical waveguide

The velocity distributions of 250nm diameter gold nanospheres trapped in the evanescent fields of optical waveguides are studied. The automated analysis of a large number of particles and temporal frames is described. It is used to show that the envelope of the particles' speed follows the mode intensity profile of the evanescent field along a length of the waveguide and across its width. Modal beating in a dual-moded waveguide is mapped by analysis of nanoparticle distributions above the waveguide. A modal power of _150mW at l=1066nm in a Cs+ ion-exchanged monomode waveguide results in speeds of up to 500microm/s.

Simple approach to calculate the refractive index profile of ion-exchanged waveguides

In graded-index glass waveguides a key factor for the design of components and devices is usually the accurate determination of the refractive index profile as a function of depth. The problem of reconstructing the index profile using the measured effective refractive indices has been faced by several authors. Here we suggest a new expression, linear combination of two analytical functions, which is able to provide a good approximation of the solution of the differential equation that rules the thermal diffusion process. The use of this equation, in connection with the general approach of inverting the Wentzel-Kramer-Bruilloin (WKB) eigenvalue equation, leads to a simple, fast, and accurate computation of the refractive index profile obtained by ion exchange. The application of the method to various Ag-exchanged waveguides in different glass matrices, with better accuracy than most of the usual procedures, has been demonstrated.

Bend loss effects in diffused, buried waveguides

Bend loss effects can be a significant concern in the design and performance of diffused, buried waveguide devices. Since diffused, buried waveguides typically do not have analytical mode solutions, the bend mode must be expressed as an expansion of straight waveguide modes. For the case of buried ion-exchanged waveguides, the bend loss is affected by bend radius, the duration of the ion exchange and burial processes, as well as the size of the mask opening used to create the waveguides and applied field during burial. The bend loss effects for each of these variables are explored under typical fabrication conditions.

Hybridization of III-V semiconductor membranes onto ion-exchanged waveguides

In this paper, we present an original method for the realization of hybrid photonic integrated circuits (PICs) based on ion-exchanged (IE) waveguides and III-V semiconductor materials. In our approach, we propose to bond thin semiconductor membranes at designated locations of the PIC where active functions are required. The advantage of very thin membranes is the possibility to keep the optical pathway defined by the IE waveguides even if the semiconductor refractive index is much higher than the glass refractive index. Modal analysis and beam propagation method simulations have been carried out in order to predict the modal structure of the propagated light into the membrane loaded IE waveguide and the transition from the IE waveguide itself through adiabatic tapers.

Tin-Diffused Glass Slab Waveguides Locally Covered with Tapered Thin TiO2 Films for Application as a Polarimetric Interference Sensor with an Improved Performance

Common soda lime slide glass substrates made by floating molten glass on the surface of molten tin contain a tin-diffused layer that is demonstrated to be a low-loss polarization-insensitive slab optical waveguide. In this study, such a tin-diffused waveguide was locally covered with a tapered thin TiO2 film to form a composite structure in which the zeroth-order transverse electric (TE0) and magnetic (TM0) modes are spatially separated from each other. This feature enables the composite structure to serve as a highly sensitive polarimetric interferometer. Moreover, a negligible modal birefringence of tin-diffused waveguides offers the polarimetric interferometer an improved performance relative to those fabricated earlier using single-mode potassium ion-exchanged glass waveguides. In situ detection of both the protein adsorption and a small change in refractive index of liquid was accomplished using the tin-diffused waveguide-based polarimetric interferometer. With horse heart myoglobin, adsorption from aqueous solution less than 0.125 monolayer coverage can cause the interferometer to yield a phase-difference change of delta phi = 2pi.

Buried ion-exchanged glass waveguides using field-assisted annealing

Theoretical and experimental studies on buried ion-exchanged waveguides using field-assisted annealing (FAA) in erbium-doped phosphate glasses are reported. The procedure for making buried waveguides with the use of a two-step process is demonstrated. An analytical model for the FAA process was developed to simulate the experimental conditions, and both the refractive index profiles and the effective buried depths of these waveguides are predicted. The mode intensity profiles as well as the buried depths are measured, and the measured data are in good agreement with the simulated results.

Ion-exchanged waveguides in glass doped with PbS quantum dots

The lowest-loss (≲1dB∕cm) ion-exchanged waveguides in glass doped with PbS quantum dots are presented. Near-field mode profile and refractive index profile using the refracted near-field technique were measured for these waveguides. We demonstrate that the optical properties of this glass remain unchanged during the ion-exchange process.

Semicircular glass waveguide dependence on exchange-time and window width

A detailed theoretical and experimental study of the semicircular waveguide dependence of surface Tl+–Na+ ion-exchange waveguide on exchange-time and window width is reported. Modeling, which includes the effect of ion-exchange time t and window width W, agrees well with our experiments showing that a surface semicircular waveguide depends on Defft≫W/2. The result may be used in the proper design of arrayed microlens and integrated optical circuits, such as diffractive waveguide gratings, and so on.

Measurement of ion-exchanged waveguide burial depth with a camera

We present a novel method of measuring the depth of a mode for a buried ion-exchanged channel waveguide in glass while si- multaneously measuring its near-field mode profile. The method is simple to implement and can be used without removing the sample from a standard waveguide characterization system. Experimental results for surface and buried Ag 1 /Na 1 exchanged waveguides are presented. It is demonstrated that the depth of a mode can be determined with an un- certainty of 60.2 mm. © 2004 Society of Photo-Optical Instrumentation Engineers.

4.25 dB gain in a hybrid silicate/phosphate glasses optical amplifier made by wafer bonding and ion-exchange techniques

In this letter, we present the realization of a hybrid optical amplifier composed of an erbium/ytterbium (Er3+∕Yb3+) co-doped phosphate glass wafer bonded on a silicate glass substrate. Indeed, a thin guiding phophate glass layer has been reported on an ion-exchanged channel passive waveguide by the wafer bonding technique creating a hybrid guiding structure. A 4.25dB gain for 140mW launched pump has been demonstrated with a 1.16-cm-long hybrid amplifier.

Modeling of ion-exchanged glass waveguide structures

Glass waveguide devices fabricated by ion exchange have evolved to the point where conventional assumptions of waveguide symmetry and mutual independence are no longer valid. We describe a modeling tool that allows for the presence of an arbitrary, nonhomogeneous electric field distribution during the ion exchange process. An asymmetric waveguide produced by selective field-assisted burial is modeled and discussed. A directional coupler fabricated by field-assisted thermal ion exchange and subsequent field-assisted burial is modeled, and it is shown that a proximity effect exists in which the waveguides exert a mutual influence upon each other during processing.

Rare-earth doped tungsten tellurite glasses and waveguides: fabrication and characterization

Tungsten tellurite glasses doped with Er3+, Tm3+, Pr3+, and Ho3+ ions were prepared by melt quenching. The glass matrix was the same for all types of glasses and had a high sodium content in order to allow the fabrication of waveguides using an ion-exchange technique. The absorption spectra of the glasses were measured and the Judd–Ofelt parameters Ωq were obtained from the experimental oscillator strengths of the f→f transitions. Er3+ doped glasses showed a very high quantum efficiency when comparing the calculated radiative decay time with the measured lifetime of the 4I13/2 metastable level. Ag+↔Na+ ion-exchanged planar waveguides were successfully obtained in all types of glasses and characterized by the prism coupling technique. It turned out that the diffusion constant values are very similar for glasses containing different rare-earth ions with the same concentration, while, at least for the Er3+ doped ones, the diffusion constant changes with the ions concentration.

High-reflectivity Bragg gratings fabricated by 248-nm excimer laser holographic ablation in thin Ta2O5 films overlaid on glass waveguides

We demonstrate strong Bragg grating reflection in Ta2O5 (tantalum pentoxide) thin films overlaid on potassium ion-exchanged channel waveguides in BK-7 glass, inscribed using 248-nm excimer laser holographic ablation. The experimental data presented are divided into two sections: the first section refers to the study of the grating ablation process of thin Ta2O5 films with respect to the exposure conditions, while the second focuses on the implementation of these relief gratings in functional waveguide devices. Firstly, experimental data on grating morphology versus exposure conditions, accomplished with scanning electron microscopy microscans, are presented. In the second section diffraction spectra for waveguide gratings are presented and analysed. Spectral notches in transmission of depth ≈-18 dB for the TM polarisation were obtained from 16-mm-long gratings patterned in waveguides overlaid with a 105-nm-thick Ta2O5 film, using 50 pulses of 60-mJ/cm2 energy density.

K(+)-Na+ ion-exchanged waveguides in Er(3+)-Yb3+ codoped phosphate glasses using field-assisted annealing.

Buried channel waveguides were fabricated in Er(3+)-Yb3+ codoped phosphate glasses with use of the thermal two-step ion-exhange method. The K(+)-Na+ ion-exchange process was first carried out in pure KNO3 molten bath, and then field-assisted annealing (FAA) was used to make the buried waveguides. The fluorescence properties of bulk glasses and channel waveguides were characterized, and the waveguide properties were studied. The formation mechanism of buried waveguides was analyzed, and the improved gain characteristics of the waveguide amplifiers with use of different FAA temperatures were measured. The maximum net gain of the waveguide amplifiers at 1.534-microns wavelength was measured to be approximately 3.4 +/- 0.1 dB/cm with 120-mW pump power at 975-nm wavelength.

Measurement of Waveguide Birefringence Using a Ring Resonator

A simple method for accurately measuring the birefringence of a ring resonator waveguide using its resonant characteristics is presented. A measurement accuracy of 1/spl times/10/sup -6/ is observed. This approach is then used to measure the effect of thermal annealing on the level of birefringence in an ion-exchanged waveguide.

Towards a more accurate refractive index profile of ion-exchanged waveguides

We evaluated the accuracy of the standard m-line method in the description of the refractive index profile of ion-exchanged waveguides by comparing its results with those from energy dispersion spectroscopy and direct near-surface/extended Brewster–Pfund (DNS-B) Method. Looking at a few single and double-exchange processes, the comparison shows three major situations: (i) the m-line accuracy is validated by the other two methods; (ii) discontinuity of ion-concentration does not allow the assumption of a continuous refractive index profile; or (iii) although the overall m-line profile is compatible with results from the other two methods, these significantly depart by a near-surface inflection-in which case, the DNS-B can be used together with the m-line experimental data to produce a more accurate index profile.

Advanced spectral filtering functionalities in ion-exchanged waveguides with artificial cladding gratings

We report on a concept of a waveguide integrated filter with ion exchange technology. The manufacturing of a cladding around a core waveguide allows the coupling between a guided mode and several cladding modes as it is usually encountered in long period fiber gratings. Good isolation can thus be obtained in a low cost manufacturing process. Experimental results and behaviour scheme are given.

Excimer laser inscribed submicron period relief gratings in InOx films and overlaid waveguides

Relief gratings of submicron periodicity are patterned in InOx thin oxide films using 248 nm interferometric excimer laser ablation. The ablation process is studied in terms of grating depth versus exposure conditions, using optical diffraction efficiency measurements. Real time monitoring of grating growth and film resistivity during grating writing are also presented. To study the exact grating morphology, scanning electron microscopy and atomic force microscopy microscans of the machined structures are performed. A discussion on the ablation behavior of InOx thin films is given in accordance with the experimental data obtained. Relief gratings are patterned in InOx thin films overlaid on ion-exchanged channel waveguides, and reflection spectra are also reported.

Design and fabrication of a glass waveguide optical add–drop multiplexer by use of an amorphous-silicon overlay distributed Bragg reflector

We report the fabrication of a distributed Bragg reflector (DBR) on a silver ion-exchanged glass waveguide with a patterned overlay of sputter-deposited amorphous silicon (a-Si). Using this high-refractive-index overlay DBR technology, we demonstrate a fully functional glass-integrated optic add-drop multiplexer (OADM). The OADM consists of a Mach-Zehnder interferometer (MZI) containing overlay DBR gratings in both arms. The design, fabrication, and characterization procedures of the sputter-deposited a-Si overlay DBR and the ion-exchanged glass waveguide MZI are discussed in detail. The completed 3-cm-long OADM exhibited a 24-dB transmission dip with a 3-dB bandwidth of 0.5 nm. The 1-cm-long a-Si overlay DBR induced an additional attenuation of 1.2 dB. A simplified method for overlay DBR fabrication that utilizes a lift-off technique is also proposed and demonstrated.

An Integrated 2 × 2 SSFLC Optical Switch with Channel Ion-Exchanged Glass Waveguides

A novel compact structure suitable for the realization of a 2 × 2 bistable integrated optical switch using ferroelectric liquid crystal is reported. The switch consists of a vertical coupler formed by two Ag+-Na+ ion-exchanged single-mode channel waveguides diffused in two BK7 glass substrates of a surface stabilized liquid crystal cell. The coupling properties, and thus the switching state (bar or cross), of this structure can be controlled by electrically reorienting the director of the aligned liquid crystal layer. The device was simulated and optimized at λ = 1550 nm by using a beam propagation method algorithm. The simulation of the TE 00 mode propagating along the designed device showed crosstalk attenuation and losses of 42.5 dB and 0.49 dB respectively with a coupling length of 141 μ m.