Ari Tervonen

Ion-exchanged glass waveguide technology: a review

We review the history and current status of ion exchanged glass waveguide technology. The background of ion exchange in glass and key developments in the first years of research are briefly described. An overview of fabrication, characterization and modeling of waveguides is given and the most important waveguide devices and their applica- tions are discussed. Ion exchanged waveguide technology has served as an available platform for studies of general waveguide properties, in- tegrated optics structures and devices, as well as applications. It is also a commercial fabrication technology for both passive and active wave- guide components. C 2011 Society of Photo-Optical Instrumentation Engineers (SPIE).

Reduced propagation loss in silicon strip and slot waveguides coated by atomic layer deposition

When silicon strip and slot waveguides are coated with a 50 nm amorphous titanium dioxide (TiO2) film, measured losses at a wavelength of 1.55 μm can be as low as (2 ± 1)dB/cm and (7 ± 2)dB/cm, respectively. We use atomic layer deposition (ALD), estimate the effect of ALD growth on the surface roughness, and discuss the effect on the scattering losses. Because the gap between the rails of a slot waveguide narrows by the TiO2 deposition, the effective slot width can be back-end controlled. This is useful for precise adjustment if the slot is to be filled with, e. g., a nonlinear organic material or with a sensitizer for sensors applications.

Atomic layer deposited titanium dioxide and its application in resonant waveguide grating

We demonstrate good optical quality TiO(2) thin films grown by atomic layer deposition at 120 degrees C. The optical properties were studied using spectroscopic ellipsometry and prism coupling methods. The refractive index was 2.27, and the slab waveguide propagation loss was less than 1dB/cm at 1.53microm. A high quality resonant waveguide grating was fabricated using a thin TiO(2) layer on top of a SiO(2) grating.

Single-layer one-dimensional nonpolarizing guided-mode resonance filters under normal incidence

We demonstrate that properly designed one-dimensional guided-mode resonance filters (GMRFs) with only one grating layer can exhibit a nonpolarizing resonant filtering effect under normal incidence. A sinusoidal profile nonpolarizing GMRF is realized by photoinduced surface-relief grating formation on thin films of polymer-azobenzene complexes and subsequent atomic layer deposition, showing the feasibility of fabrication of such compact GMRFs.

Low-loss silicon slot waveguides and couplers fabricated with optical lithography and atomic layer deposition

We demonstrate low-loss silicon slot waveguides patterned with 248 nm deep-UV lithography and filled with atomic layer deposited aluminum oxide. Propagation losses less than 5 dB/cm are achieved with the waveguides. The devices are fabricated using low-temperature CMOS compatible processes. We also demonstrate simple, compact and efficient strip-to-slot waveguide couplers. With a coupler as short as 10 µm, coupling loss is less than 0.15 dB. The low-index and low-nonlinearity filling material allows nonlinearities nearly two orders of magnitude smaller than in silicon waveguides. Therefore, these waveguides are a good candidate for linear photonic devices on the silicon platform, and for distortion-free signal transmission channels between different parts of a silicon all-optical chip. The low-nonlinearity slot waveguides and robust couplers also facilitate a 50-fold local change of the waveguide nonlinearity within the chip by a simple mask design.

A guided-wave Mach-Zehnder interferometer structure for wavelength multiplexing

A guided-wave Mach-Zehnder interferometer structure, based on the use of a four-port hybrid optical coupler consisting of symmetric and nonsymmetric y junctions, is proposed for wavelength-division multiplexing application. This structure provides less sensitivity to fabrication parameters and optical polarization, and can also be applied to a wide-wavelength spacing operation. Interferometers for wavelength splitting in the 1.3- and 1.55- mu m windows were designed and fabricated into a glass substrate with a dry silver ion exchange process. The measured crosstalk was -30 dB with nonpolarized light.<<ETX>>

Challenges and opportunities for integrated optics in optical networks

Ever-increasing needs for more telecommunication bandwidth have brought about the recent emergence of WDM technology as a commercial reality with a very substantial volume, and prospects for near future development of optical networking. The new optical functionalities in networks will also provide conmiercial opportunities for integrated optics, which have been yearned for a long time. Integrated optics must meet the new challenges of fulfilling the strict performance, reliability and cost requirements for applications in the field. Integrated optics community is experiencing a transition to a new era, with their work moving from research laboratories to industrial production. Various expected applications for integrated optics devices in the areas of wavelength division multiplexing, optical modulation, optical switching, wavelength conversion and others are reviewed. General views on development of packaging technologies, component design and testing are also included.

Angled sidewalls in silicon slot waveguides: conformal filling and mode properties

Effect of angled sidewalls on the filling and properties of silicon slot waveguides is discussed. We demonstrate complete filling of slot waveguide structures with oxide material systems using the atomic layer deposition technique and discuss use of various slot filling materials. Properties of the optical modes in angled-sidewall slot waveguides are studied. Enhanced vertical confinement is obtained with certain waveguide parameters. The reduced effective mode area enhances e.g. nonlinear effects in the waveguide. We discuss the use of atomic layer deposition in realization of filled slot waveguides optimized for all-optical functionalities.

Ytterbium-doped fibers fabricated with atomic layer deposition method

We report on a new fabrication method of producing ytterbium doped fibers by atomic layer deposition (ALD) in combination with the conventional modified chemical vapor deposition (MCVD) technique. An MCVD soot-preform with a porous layer of SiO(2) is coated with layers of Yb(2)O(3) and Al(2)O(3) prior to sintering, using the gas-phase ALD method. An SEM/EDS material analysis study shows that the dopants successfully penetrate the full thickness of 320 µm of the soot layer. An Yb-doped fiber fabricated by this technique shows a background attenuation of 20 dB/km, a uniform longitudinal Yb-doping profile, and good laser characteristics with a slope efficiency of 80%. Furthermore, we present a comparison in terms of photodarkening between the MCVD-ALD fiber and a solution doped fiber, fabricated with the same MCVD recipe. The new MCVD-ALD fiber appears to be more photodarkening resistant.

Evanescent-field amplification in Nd3+-doped fluoride planar waveguide

Planar channel waveguides of rare‐earth doped fluoride glass are demonstrated with single mode excitation and propagation losses below 3 dB/cm. The waveguide core was fabricated by Ag+–Na+ molten salt ion exchange process in a borosilicate glass (BGG31), and a Nd3+‐doped ZBLAN glass was used as a cladding. A 0.45 dB signal amplification at 1.064 μm was observed in the fabricated 1 cm long waveguide, and a 0.9 dB amplification is expected at the emission peak (1.049 μm). Modeling results show 2.5 dB/cm potential gain with the improvement in surface flatness of ZBLAN glass.