Integration Of Optical Components Research Articles

Integrated optics components and devices using periodic structures

The selected research activities on integrated optics components and devices using periodic structures are reviewed, with emphasis on the authors' works employing the electron-beam writing technique. The periodic structures include static gratings and dynamic ones produced through acoustooptic (AO) and electrooptic (EO) effects. They provide a variety of passive functions and effective means for guided-wave control. The review is made from the integration point of view, including the most recent results. First, the theoretical fundamentals are outlined and the electron-beam writing techniques, including the writing system, are discussed. Next, passive components (grating deflectors, filters, lenses, couplers, etc.) and elements for guided-wave controlling and detecting (AO and EO grating elements and photodetectors) are described. Then, integrated optic devices, i.e., wavelength demultiplexers, RF spectrum analyzers, optical disk pickup, etc., are presented. Finally, the possibility of future applications is discussed.

Plasma deposition of metal oxide films for integrated optics

The search for alternatives to sputtered or ion exchanged glass or sputtered metal oxide films as a medium for use in integrated optics components forms the background to this paper. Aluminium oxide is currently being studied and preliminary experiments indicate that there may be some new pathways to produce the thin films organically by plasma deposition. Such a process might enable substrate temperatures to be lowered, and thus offer the possibility of producing reduced loss, controlled refractive index waveguiding films: often these films are deposited onto materials which are thermally sensitive. Comparison of films deposited from aluminium alkoxide, an organic precursor, and aluminium chloride indicate that the process is viable.

Utilization of the selectivity of dissolution of glassy chalcogenide semiconductor films in the formation of passive integrated-optics components

A study was made of the influence of the stoichiometry profile of films in the As–S system on the dynamics of their dissolution in an alkali etchant. It was found that the surface changes in the stoichiometry of As–S films exposed to laser radiation influenced the rate of dissolution. The dynamics of dissolution of glassy chalcogenide semiconductor films with given stoichiometry profiles was analyzed and methods of formation of grating structures with a high diffraction efficiency were considered.

Single-crystal silicon: a new material for 1.3 and 1.6 μm integrated-optical components

The first all-silicon integrated-optical components for 1.3/1.6 μm have been demonstrated. An optical power divider with end-fire coupling was constructed from intersecting channel waveguides. Guides were fabricated by plasma-etching of an intrinsic Si layer grown epitaxially on a heavily doped Si substrate (n on n + or p on p + ). Active components are proposed.

The Clifford Parterson Lecture, 1983 Optical fibre communication, present and future

The original objectives established in the mid-1960s for optical fibre systems were more than met by the first production equipment in1980. Now, second-generation single-mode systems, with still greater per­formance, are entering service. However, current research shows that the technology is still in its infancy. The use of highly coherent semiconductor laser transmitters coupled with heterodyne detection has given large improvements in receiver sensitivity. Understanding the nonlinear properties of glass fibres has paved the way to higher transmitter powers and the use of picosecond pulses. Many integrated-optic components such as modulators, couplers and other components will probably be used while the monolithic integration of optical and electronic components may lead to further cost reductions. The paper will describe these advances, examine their possible appli­cations in systems and discuss how these may be exploited in the future.

New physical effects on periodically grooved optical planar waveguides

Open dielectric waveguides are of prime importance in the field of integrated optics. Almost all of the published literature concerned with guiding, radiating or scattering effects on open dielectric structures involves a surface wave striking a structural discontinuity at normal incidence. Under those conditions, the TE and TM modes remain independent of each other. When the surface waves are incident at an arbitrary angle, however, the TE and TM modes couple to each other at the geometrical discontinuity, giving rise to a rich variety of interesting and sometimes unexpected new physical effects. We have previously examined such TE-TM mode coupling, and the interesting new physical effects that result from it, in the context of uniform open waveguiding structures. We found that on most dielectric strip waveguides leaky modes can occur instead of the previously expected purely-bound modes, and that resonance effects appear in the leakage process. Furthermore, these leaky modes constitute a new class of leaky modes, since the leaking energy possesses a polarization opposite to tl~at present in the main body of waveguide, in contrast to customary leaky modes. Here we are concerned with periodically-grooved open dielectric waveguides, involving a wide planar dielectric layer. We find that guidance in a direction oblique to the grooves produces four stop bands instead of the usual two in the Bragg reflection region; also produced are interesting anisotropy phenomena such as beam steering and focusing, radiation at peculiar skew angles, and surprisingly large cross-polarization effects. The physical effects are relevant to integrated optics components such as multiplexers, filters and mode deflectors. The guidance of optical surface waves propagating in a direction normal to the grooves on a periodically:corrugated planar dielectric waveguide is well known, and various theoretical treatments are available. Such structures have been used in grating couplers and in distributed-feedback lasers, for example. The electromagnetic boundary-value problem for the case of normal incidence is scalar, however, where the TE and TM surface waves remain independent of each other. When the

Spectral channel demultiplexer utilizing a planar multimode waveguide

The technology of fabrication of glass planar multimode waveguides with a guiding layer a few tens of microns thick was mastered. Such waveguides should find use in various integrated-optics components of fiber-optical communication lines employing multimode fibers. A waveguide of this type was used to construct a channel demultiplexer with a holographic concave diffraction grating designed for lines with spectral channel multiplexing in multimode or single-mode fiber waveguides. The reciprocal linear dispersion of this demultiplexer was 43 nm/mm and the crosstalk level was less than 15 dB (measured in terms of the optical power) after demultiplexing of channels for monochromatic carriers separated by spectral intervals of 43 nm.

Components for optical communications systems: A review

Current trends in research and development of components for optical communication are reviewed. Emphasis is placed on active components for fiber-optic systems which have undergone recent major advances. Basic properties of optical fibers and recent technological improvements in splices, connectors, and source/detector-fiber couplers are presented first. This background information serves as a basis for describing recent developments in optical sources (e.g., device reliability, LED's and laser diodes) and photodetectors. Developments in both the 0.8-0.9-µm and 1.0-1.7-µm wavelength regions are covered. Also surveyed are results of research in areas of potential interest for optical communications: novel fiber-optic components, integrated optics (sources and modulators/switches), novel device fabrication methods, and integration of optical components.

Investigation of waveguide structures formed by irradiation of fused quartz with hydrogen ions

The effective refractive index of modes traveling in waveguides formed by irradiation of fused quartz with hydrogen ions was determined as a function of the implanted-ion dose, ion energy, and annealing temperature. The change in the refractive index Δn in the irradiated layer was estimated. Annealing in the temperature range 600–700°C reduced the waveguide thickness without altering significantly the value of Δn. Two integrated-optics components—a mode selector and a waveguide polarizer—were made from these waveguides.

Growth of GaAs-Ga1−xAlxAs over preferentially etched channels by molecular beam epitaxy: A technique for two-dimensional thin-film definition

In this paper, studies of the molecular beam epitaxy (MBE) of GaAs-Ga1−xAlxAs multilayer structures over preferentially etched channels on GaAs substrates are described. It is found that the growth characteristics with MBE are entirely different from those obtained from similar experiments when LPE is used. Results obtained indicate that this etch-and-fill technique using MBE as the growth process should be particularly useful in fabricating injection lasers, laser arrays, and integrated optics components which require planar definition.

Formation of integrated optics components by multiphoton photorefractive processes

Phase holograms have been formed in pure outdiffused LiNbO3 waveguides using the photorefractive effect initiated by two-photon absorption. Efficient holograms were recorded with two guided waves, of less than 100 W peak power, and less than 10 μJ optical energy. This technique automatically compensates for wave front perturbations in the guide and allows the formation of various integrated components such as wavelength multiplexers and optical switches.

Phase profile synthesis for integrated optics

In this paper, a technique to synthesize a very narrow and apodized slit image is described and, by extension, a method using Fourier synthesis to realize phase profiles suitable for fabricating integrated-optics components is proposed.

Embedded heterostructure epitaxy: A technique for two-dimensional thin-film definition

Selective multilayer epitaxial growth of GaAs-Ga1−xAlxAs through stripe openings in Al2O3 mask is reported. The technique results in prismatic layers of GaAs and Ga1−xAlxAs ’’embedded’ in each other and leads to controllable uniform structures terminated by crystal faces. The crystal habit (shape) has features which are favorable for fabrication of cw injection lasers, laser arrays, and integrated optics components which require planar definition.

Ion Beam Micromachining of Integrated Optics Components

Thin film integrated optics components such as light guides, modulators, directional couplers, and polarizers demand high quality edge smoothness and high resolution pattern formation in dimensions down to submicrometer size. Fabrication techniques combining holographic and scanning electron beam lithography with ion beam micromachining have produced planar phase gratings with intervals as small as 2800 A, guiding channel couplers in GaAs, and also wire- grid polarizers for 10.6-,microm radiation.