Waveguide Arrangement Research Articles

Nonlinear light propagation in fs laser-written waveguide arrays

The femtosecond laser direct writing technique has been the driving force behind significant progress in the experimental investigation of wave dynamics in discrete systems over the recent years. In this chapter, we review selected results of our research in the field of nonlinear light propagation in coupled waveguide arrangements.

Propagation of acoustic waves in phononic-crystal plates and waveguides using a finite-difference time-domain method

Propagation of acoustic waves in a phononic-crystal plate and related waveguides are analyzed in this paper. A two-dimensional phononic-crystal plate consisting of circular steel cylinders which form a square lattice in an epoxy matrix is studied first using the finite-difference time-domain (FDTD) method. The Bloch theorem is employed to deal with the periodic condition, and the traction free condition is set on the top and bottom boundaries of the plates. The dispersion curves and displacement fields are calculated to identify the band gaps and eigenmodes. With the existence of a complete band gap in the phononic-crystal plate, an acoustic waveguide is presented accordingly. Eigenmodes of acoustic waves inside the waveguides are indicated, and the modes are affected by the geometry arrangement of waveguides. Inside the phononic-crystal plate waveguides, wave propagation is well confined within the structure.

Neutronics analysis of the ECW launching system in the ITER upper port

Abstract This paper is devoted to the neutronics analysis of the electron cyclotron wave (ECW) launching system installed in the ITER upper port. The launcher design developed by FOM Rijnhuizen with a twisted arrangement of straight waveguides was selected to facilitate the maintenance of the ECW system by avoiding mitre bends. Two types of ECW launcher designs were considered in this paper: limited and full focusing. Three dimensional MCNP models of the ECW launchers were developed with high accuracy directly from the CAD geometry models by means of an interface programme. A shielding analysis was performed to estimate the length and thickness required for the shield around the waveguides. A two-step method making use of surface sources and point detectors was applied in the neutron streaming calculations in order to estimate the radiation load on the CVD diamond window. The neutron and gamma fluxes, the nuclear heat density, and the helium production were calculated. The results show that the design limits both for the limited and the full focusing ECW models are met.

PLC platform for bidirectional transceiver with wide multimode output waveguide to receiver

We present a new configuration of a thin-film-filter (TFF)-embedded planar-light-circuit platform for a bidirectional transceiver module to enhance a tolerance of the insertion loss to the positional deviation of the TFF, by using a wide multimode waveguide structure that guides a reflected light from the TFF to a photoreceiver. It is experimentally shown that the new scheme has a merit in a high tolerance to the positional deviation of the TFF, and that it maintains a considerably high optical isolation by a proper arrangement of waveguides.

The optical measurement station for complex testing of microelements

The paper presents a concept of optical measurement station for complex testing of microelements including MEMS, MOEMS and electronic components and assemblies. The wide selection of examples proves that the specific measurement requirements are fulfilled by alternative usage of combined conventional and grating interferometers CI/GI (reflective surfaces), in-plane and out-of-plane ESPI (scattering surfaces) and digital holographic interferometry DHI (mixed surfaces) supported by thermovision. All these methods are realized by integrated microinterferometer (IWaM) based on a glass waveguide or air cavity waveguide arrangements. The air cavity IWaM allows to form a thermal output for combined thermovision CI/GI or ESPI measurements. IWaM has a compact design insensitive to mechanical vibrations and may be easily rearranged to work with the selected measurement techniques. It is also fully integrated with an optical microscope and it is designed to work both in laboratories and in production environments.

Steered coupled-cavity-backed Hertzian dipole array

This paper presents the operating characteristics of a coupled-cavity-backed Hertzian dipole resonator array excited with mutually injection-locked voltage-controlled oscillators (VCOs). It is demonstrated that microwave spatial power-combined inter-injection locking through mutual coupling of individual antenna oscillators can be obtained with an auxiliary coupling network formed by a cavity iris configuration introduced within a reduced-height waveguide arrangement. As a result, strong mutual-coupling control can be realized and exploited in conjunction with self-injection-locked oscillators in order to achieve direct phase modulation of the locked oscillators. Beam scanning up to 10/spl deg/ off the broadside through locked VCO phase modification has been demonstrated in a three-element array occupying a space of only 0.6 /spl lambda//sub 0//spl times/0.027 /spl lambda//sub o/ at 998 MHz.

Optical waveguide sensors in analytical chemistry: today's instrumentation, applications and trends for future development

Current concepts for chemical and biochemical sensing based on detection with optical waveguides are reviewed. The goals are to provide a framework for classifying such sensors and to assist a designer in selecting the most suitable detection techniques and waveguide arrangements. Sensor designs are categorized on the basis of the five parameters that completely describe a light wave: its amplitude, wavelength, phase, polarization state and time-dependent waveform. In the fabrication of a successful sensor, the physical or chemical property of the determined species and the particular light wave parameter to detect it should be selected with care since they jointly dictate the sensitivity, stability, selectivity and accuracy of the eventual measurement. The principle of operation, the nature or the detected optical signal, instrumental requirements for practical applications, and associated problems are analyzed for each category of sensors. Two sorts of sensors are considered: those based on direct spectroscopic detection of the analyte, and those in which the analyte is determined indirectly through use of an analyte-sensitive reagent. Key areas of recent study, useful practical applications, and trends in future development of optical waveguide chemical and biochemical sensors are considered.

Design procedures for passive planar coupled waveguide devices

Many useful optical systems make use of coupled waveguides configured in nonplanar arrangements. This paper deals with the emulation of such systems in planar waveguide arrangements, so that otherwise nonplanar systems can be implemented as compact, integrated optics chips. As an example, design procedures are presented for a wholly planar 3*3 coupler to emulate the symmetric 3*3 fibre coupler; the first procedure is readily implemented yet holds only for weakly coupled guides, whereas the second is unwieldy but can accommodate arbitrarily strongly coupled guides. This discussion leads to general remarks about passive planar coupled waveguide devices and it is proven that, in theory, any lossless nonplanar coupled waveguide device's behaviour can be emulated by a wholly planar coupled waveguide device. Lastly, using these ideas, implementations of planar emulations of the symmetric 4*4 and 5*5, fibre couplers are presented.

Measuring humidity with planar polyimide light guides

Planar polyimide light guides can be used for optical detection of humidity. In a phase-matched guide a TE mode and a TM mode of different orders are influenced differently by a humid atmosphere. With crossed polarizers a phase shift induced by the moisture is detectable in the form of an oscillating output signal. For fully cured and thus well-defined and stable fluorinated polyimide light guides a sensitivity curve is presented for the humidity range of 10-75% relative humidity. A special sensitivity is obtained by using a four-layer waveguide arrangement with two layers of polyimide. The shift of the effective mode indices is also measured for each polarization by using a half-integrated interferometer. The results are interpreted in terms of a refractive-index increase that is due to water indiffusion and a swelling process for higher humidities. The measurement in the waveguide interferometer required a moisture-insensitive coating of the reference channel. This was achieved by the use of fluorinated polymers.

Experimental study of forward scattering for a periodic arrangement of slotted waveguides

Phase reversal sound barriers, composed of periodic slotted waveguides, have shown promising results in low-frequency noise control for plane waves normal to the obstacle, when compared with solid barriers. The phase reversal effect results in destructive interferences in the shadow zone of the barrier. In order to introduce this new phase-controlling device in real conditions (obliquely incident ground reflections, variable source position, etc.), it was necessary to investigate its performance at any angle of incidence. This complementary experimental study, performed in an anechoic chamber, is a verification of the previous theoretical [Mongeau et al., J. Acoust. Soc. Am. 80, 665–671 (1986)] and experimental [Chvojka et al., J. Acoust. Can. 13 (1985)] studies. The results show that, in a measuring plane normal to the slots (waveguide entrances), the performance of this new type of barrier remains quite unchanged at any oblique angle of incidence within −60 ° to +60 °. On the other hand, the studies have clearly shown that this performance is much more angle dependent in a measuring plane parallel to the slots.

Microwave Hall conductivity of the two-dimensional electron gas in GaAs-AlxGa1-xAs.

For the first time the quantum Hall effect was observed in ${\ensuremath{\sigma}}_{\mathrm{xy}}$ at microwave frequencies in the two-dimensional electron gas in GaAs-${\mathrm{Al}}_{0.35}$${\mathrm{Ga}}_{0.65}$As using a crossed waveguide arrangement. These frequencies were ${10}^{3}$--${10}^{4}$ higher than those used in previous experiments where a so-called low-frequency breakdown of the integer quantum Hall effect was observed. Our microwave results show that this effect does not occur in GaAs-${\mathrm{Al}}_{\mathrm{x}}$${\mathrm{Ga}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$As heterostructures. Therefore, we have to rule out the mechanism of an effective delocalization at low frequencies and the existence of long semiclassical orbits in the sample.

Microwave electron spin resonance spectrometer with operation to 54 mK in a dilution refrigerator

A 9.5-GHz electron spin resonance ESR spectrometer which operates in conjuction with a helium dilution refrigerator down to 54 mK is described. Instead of the conventional waveguide and cavity arrangement, coaxial and superconducting twisted pair transmission lines are used to bring the microwave power into the mixing chamber, where a tiny coil surrounds the sample. This low Q, high-filling factor configuration has a sensitivity about the same as that of a conventional high Q cavity with a small filling factor. Several suggestions for further development and improvement are presented.

Afterglow Plasma Diagnostics with a Microwave Sampling Radiometer

A simple waveguide arrangement has been developed for the study of microwave absorption and emission from a magnetized afterglow plasma column. The time and frequency resolved measurements are performed by a sampling radiometer. A comparison and null technique permits the direct measurement of the electron temperature. Continuous plots of the temperature vs frequency, magnetic field, and afterglow time are made possible by means of a servoloop. The width of the emission or absorption spectrum in the range of upper hybrid frequencies is used to derive the electron density which, together with the temperature measurement, allows a more complete analysis of the plasma decay.