Sadahiko Yamamoto

Measuring mode propagation losses of integrated optical waveguides: a simple method.

A semiautomatic method is described for measuring, fast and accurately, the mode propagation losses of planar or channel waveguides for integrated optical circuits. It involves a video camera aided by a microcomputer, and the real-time measurement is feasible over a broad range from low loss (<1 dB/cm) to high loss (of the order of 102 dB/cm). We examined the propagation properties of several optical waveguides prepared by sputtering or ion migration.

Normal‐mode analysis of anisotropic and gyrotropic thin‐film waveguides for integrated optics

This paper is concerned with thin‐film optical waveguides using anisotropic and gyrotropic materials, which may play an important role in the field of integrated optics. As a fundamental problem on such waveguides, normal (propagating) modes are analyzed here by the Rayleigh‐Ritz variational technique. The analysis can be interpreted directly in terms of coupling of normal modes of the basic guide with simpler material parameters. Results are placed in the form of a matrix eigenvalue problem suitable for computer calculation, whose eigenvalues and eigenvectors lead to propagation constants and field expansion coefficients, respectively. Characteristics of anisotropic guides are discussed and compared with those of conventional isotropic guides. As a typical application TE↔TM mode converters are analyzed in some detail and numerical examples are presented.

Optical pulse generation by electrooptic-modulation method and its application to integrated ultrashort pulse generators

We have developed ultrashort pulse generation by the electrooptic modulation method, where continuous-wave laser light of any wavelength can be converted to trains of ultrashort optical pulses with a variable and high repetition frequency by means of an electrooptic phase modulator for the generation of deeply chirped light, and an optical group-delay-dispersion circuit or an optical synthesizer for the compression of the chirped light. Adopting the technologies of domain inversion and guided-wave optics to this electrooptic modulation method, it will be possible to realize integrated ultrashort optical pulse generators.

Circuit theory for a class of anisotropic and gyrotropic thin‐film optical waveguides and design of nonreciprocal devices for integrated optics

A circuit‐theoretic treatment is presented for thin‐film optical waveguides using a class of real anisotropic and gyrotropic materials. The analysis is based on the two‐mode approximation in normal‐mode theory. The terminal behavior of those guides is described by the 2 × 2 transmission matrix and expressions for matrix elements of six systems that are introduced as canonical elements in circuit synthesis are derived. Properties of canonical elements are discussed with particular attention on their reciprocity. Using the transmission matrix, we can treat the design of thin‐film optical devices by a simple matrix operation familiar in conventional transmission‐line circuit synthesis. As a typical application the design of various nonreciprocal integrated‐optical devices is treated in detail. The desired response is synthesized by cascading selected canonical elements in an appropriate order. Examples include the gyrator, unidirectional mode converter, differential phase shifter, isolator, and circulator.

Integrated optical isolator and circulator using nonreciprocal phase shifters: a proposal

In this paper, we propose an integrated optical isolator and circulator using nonreciprocal phase shifters combined with Y-branch couplers or hybrid couplers. They are not used in mode coupling between orthogonally polarized waves, which leads to reduce the fabrication tolerance. We present a design example using the guide structure of YIG film and GGG substrate.

Guided‐wave optical wavelength demultiplexer using an asymmetric Y junction

An optical wavelength demultiplexer using an asymmetric Y junction is numerically analyzed and the experimental results are reported. This demultiplexer utilizes both the mode splitting characteristic of an asymmetric Y junction and the waveguide dispersion of channel waveguides. Analysis shows that the device with step‐index profile has more than 20 dB isolation for wavelengths with 6.5% separation from the center wavelength. The fabricated device composed of two‐step ion exchanged soda‐lime glass waveguides coated asymmetrically with Corning 7059 glass thin film separated the lights of 0.63 and 0.84 μm wavelengths.

Simple method of measuring propagation properties of integrated optical waveguides: an improvement

In this paper we report a simple method of measuring mode propagation losses of integrated optical waveguides with small scattering. The basic technique, reported previously, uses a microcomputer-assisted video camera; here we have improved our observation scheme by coating the optical waveguide with a thin film of fluorescent dye (Nile Blue A perchlorate) thus permitting observation of the optical fields. The Nile Blue A perchlorate absorbs light centered at 0.63 microm and emits light centered at 0.69 microm. We have measured a mode propagation loss of the order of 0.1 dB/cm of a potassium ion-exchanged glass waveguide and confirmed the damped oscillatory behavior of the attenuation vs a slightly lossy thin-film thickness curve for the ion-exchanged waveguide coating with an indium tin oxide film.

Nonreciprocal propagation in magnetooptic YIG rib waveguides

In this paper, we describe the experimental results on the nonreciprocal propagation in the magnetooptic YIG rib waveguides. First, we demonstrate the nonreciprocal phase shift in the straight waveguide, and next we confirm the nonreciprocal intensity propagation in the Mach-Zehnder interferometric waveguide with asymmetric arms. These are important for the construction of the differential phase shifter type nonreciprocal devices.

Optically induced propulsion of small particles in an evenescent field of higher propagation mode in a multimode, channeled waveguide

We report experimental results in which Mie particles were optically propelled in an evanescent field generated in a multimode, channeled waveguide. Polystyrene latex spheres 4 μm in diameter were trapped laterally at the high intensity region of the evanescent field and were driven along the waveguide channel in the evanescent field of either fundamental or higher guided modes.

Rhodamine-B-doped and Au(III)-doped PMMA film for three-dimensional multi-layered optical memory

We developed a rhodamine-B-doped and Au(III)-doped PMMA medium for three-dimensional multi-layered optical memory. Using the quenching of rhodamine-B by Au(III)-ions and the photochemical reduction of Au(III)-ions to the Au particle, the developed medium can record and store binary bit data in the form of a fluorescent patterns inside a thick medium. The recorded fluorescent pattern is read out three-dimensionally by confocal laser-scanning fluorescent pickup.