M. Meliga

Analysis and design criteria of three-section DBR tunable lasers

Three-section distributed Bragg reflector (DBR) tunable lasers emitting in the 1.55 mu m region are studied through a theoretical model which takes into account thermal effects and exploits an accurate calculation of the optical parameters. Static modal competition is discussed for transverse and longitudinal modes in operation at and above threshold. The static tuning characteristics are presented; a saturation of the wavelength shift is found for control current densities of approximately=20 kA-cm/sup -2/ due to Auger recombination processes and heating effects. The dependence of the tuning ranges on the section lengths, waveguide thickness results, and some design criteria are derived. >

REFRACTIVE INDICES OF INGAALAS GROWN BY MOLECULAR BEAM EPITAXY

The accurate determination of the refractive indices of InGaAlAs, grown by molecular beam epitaxy, is reported for the first time. The method used, modal, cutoff spectroscopy, is applied to InGaAlAs/InP single heterostructure waveguides, with compositions corresponding to band‐gap wavelengths in the range of 1.02–1.12 μm. The refractive indices are determined at different wavelengths between 1.1 and 1.6 μm, with an accuracy better than 10−3.

Refractive indices of semiconductor films measured by waveguide cutoff spectroscopy

It is shown that by measuring the cutoff wavelengths of supported modes in waveguides it is possible to determine accurately the refractive index of the guiding layer. This method has been applied to InGaAsP/InP waveguides, and their refractive indices are obtained with accuracy to the third decimal place.

Balanced optical mixer integrated in InGaAlAs/InP for coherent receivers

3-dB couplers integrated on InGaAlAs/InP grown by Molecular Beam Epitaxy (MBE) have been studied designed and fabricated. The device structure is based on the modal interference principle modelling has been performed by beam propagation and effective index methods and on this basis devices were designed covering a range of geometrical parameters. Devices have been fabricated on single and double heterostructures by wet chemical etching and characterized over the 1. 47-1. 53 im range by a tunable color center laser. Balanced coupling has been observed in several devices with a best one of output balanced within 0. 1 dB over 15 nm.

A Simple, Very High Sensitivity Method For Measurement Of Ti Films For Integrated Optics Applications In Linb03

This paper presents an experimental investigation on the characteristics and the capabilities of optical densitometry as a low cost, easy and non destructive technique to measure Ti film thickness. Optical density yields a sensitivity and a resolution equal or better than 3 Å and can be absolutely calibrated for the total metal content at given deposition conditions.

Novel accurate measurement technique for carrier lifetime in 1.5-μm semiconductor laser

We propose a new accurate method for differential carrier lifetime measurement, in which the laser under test biased below threshold is optically modulated. Experimental results are very reproducible and show very high signal/noise ratio. No additional technological process for the laser under test are required.

High-accuracy characterization of titanium films for LiNbO/sub 3/ guided wave devices by optical densitometry

An experimental study of optical densitometry as a technique for accurate determination of Ti film thickness for integrated optical devices on LiNbO/sub 3/ is discussed. Densitometric data, obtained with a simple instrument for photographic applications, are compared to conventional stylus profilometric measurements and to microgravimetric and Rutherford backscatter measurements; excellent linearity and a sensitivity of about 3 AA are evidenced, as well as capability of absolute calibration in terms of metal atoms per unit surface area, over the entire range of Ti thickness commonly used in integrated optics. The possibility of using this very simple, rapid, and nondestructive method for systematic sample testing, online deposition monitoring, and utilizing optimum coating area is also presented. >

Spectral Cut-Off Behaviour Of Ti:LiNbO3 And Semiconductor Waveguides: Analysis And Experiment

The spectrum of modal cut-off wavelengths is studied for waveguides with step and graded index profile. It is shown that by measuring the cut-off wavelength of supported modes it is possible to obtain values for the refractive index of the guiding layer in the step-index case, and information on the diffusion length and the best profile shape for graded-index guides. This method has been experimentally applied to InGaAsP and InGaAlAs waveguides, whose indices are obtained with accuracy to the third decimal place, in favorable comparison to other techniques, and to Ti:LiNb03 guides.