摘要:

The paper reports on a systematic study of planar optical waveguides in X-cut LiNbO3fabricated by the proton-exchange technique. The extent of the exchange process was monitored by measuring the infrared absorption peak at 3510 cm−1. It was established that the waveguide profile could be accurately modelled by a step index change with Δn= 0.127 at λ0= 632.8 nm and Δn= 0.096 at λ0= 1150 nm. From the mode effective refractive index measurements, the effective diffusion coefficients for the exchange process were calculated. A value for the activation energy for the proton-exchange process was established. The effect of off-Y-axis propagation on the mode effective indices of the waveguide was studied. A waveguide mode cutoff at 29° from the C-axis was established. The lowest optical losses measured in single-mode planar waveguides were 1.4 dB/cm at λ0= 632.8 nm and 1.3 dB/cm at λ0= 1150 nm for light propagating normal to the C-axis.

DOI:10.1049/ip-j.1986.0016

出版商:IEE    

年代:1986

数据来源: IET

摘要:

A survey is made of the experimental and theoretical values available in the literature on radiative and Auger recombination rates in 3-dimensional, 2-dimensional, and 1-dimensional systems for materials used in long-wavelength quaternary lasers. The values are compared with order-of-magnitude estimates based on simple dimensional arguments, with a view to the possibility of tailoring recombination rates in lowdimensional systems. It is concluded that the use of low-dimensional systems may not produce large changes in the relative sizes of the radiative and Auger rates.

DOI:10.1049/ip-j.1986.0017

出版商:IEE    

年代:1986

数据来源: IET

摘要:

A simple theory is given for the spectral properties of homogeneously broadened semiconductor lasers. The results show how the spectrum is changed when facet coatings are used.

DOI:10.1049/ip-j.1986.0018

出版商:IEE    

年代:1986

数据来源: IET

摘要:

Attenuation increases have been measured on installed cables containing high-phosphorus doped fibres, mainly at wavelengths above 1300 nm, the operating wavelength. The hydrogen concentration was determined in some of these cables, making possible a correlation with fibre-in-hydrogen tests. An accelerated aging test was carried out in which two types of cable, each containing three types of fibre, were held at 90°C. Using data from the field measurements and from the aging test, it was confirmed that the fibre-in-hydrogen test results can be extrapolated to the low hydrogen pressures present in cables. The upper limit for degradation of single-mode fibre after a long period in cable was calculated, and shown to be negligible.

DOI:10.1049/ip-j.1986.0019

出版商:IEE    

年代:1986

数据来源: IET

摘要:

Reaction kinetics is applied to the case of hydrogen reacting with defect centres in an optical fibre. The equations are extended to the case of a general distribution of activation energies and to a time varying hydrogen concentration. Experimental results on loss increase at two difference hydrogen pressures are consistent with the reaction being first order with respect to hydrogen concentration. A new method of forecasting long-term degradation is derived from the kinetics equation. Experimental results from a test at 50°C are reported, which enable forecasts to be extended to temperatures different from the laboratory ambient. Some recovery in the ‘permanent’ loss increase has been measured and the impact of this reverse reaction is discussed.

DOI:10.1049/ip-j.1986.0020

出版商:IEE    

年代:1986

数据来源: IET

摘要:

The first measurements of the dispersion ofdg/dNanddn/dN, the variation in the gain and refractive index with injected carrier concentration, are reported for λ = 1.5 µm InGaAsP laser diodes. Particular attention has been paid to the accurate evaluation of the injected carrier concentrationNthrough the direct measurement of the carrier lifetime coupled with the use of the ridge-waveguide laser structure, which benefits from real-index lateral waveguiding, together with low parallel leakage currents and low parasitic capacitance. The values ofdg/dNanddn/dN, at the lasing wavelength, were determined to be 2.7 × 10−16cm2and − 1.8 × 10−20cm3respectively.

DOI:10.1049/ip-j.1986.0022

出版商:IEE    

年代:1986

数据来源: IET

摘要:

A fully self-consistent model for DH-lasers is proposed, in which the coupling between the current injection and the active layer carrier concentration has been taken into account. It is found that this interaction has an appreciable influence on the mode displacement along the lateral direction, at high injection levels, due to preferential injection.

DOI:10.1049/ip-j.1986.0023

出版商:IEE    

年代:1986

数据来源: IET

摘要:

We examine the flow of current, parallel to the front surface, in the conventional p-n junction and in the field induced junction (FIJ) solar cell. The influence of grid finger spacing and gate voltage (FIJ cell) are studied, and the I-V characteristics of the cells computed. An algorithm for the determination of the optimum finger spacing is demonstrated.

DOI:10.1049/ip-j.1986.0024

出版商:IEE    

年代:1986

数据来源: IET

摘要:

It is shown that the dynamic linewidth of 1.5µm ridge-waveguide distributed-feedback lasers can be reduced by appropriate shaping of the modulating current waveform. A theoretical model is used to predict the result of two different shaping techniques, both in terms of the optical pulse and spectral outputs, with the optimum conditions being derived for each shaping method. Experimental results confirm the theoretical predictions and demonstrate between 40% and 60% dynamic linewidth reduction with optimum shaped modulating pulses.

DOI:10.1049/ip-j.1986.0025

出版商:IEE    

年代:1986

数据来源: IET

摘要:

The spectral properties of distributed feedback (DFB) lasers depend on the mirror reflectivities and positions, and can be modified by using a phase shifted grating. The expected yield of dynamic single-mode lasers for various DFB structures is estimated.

DOI:10.1049/ip-j.1986.0027

出版商:IEE    

年代:1986

数据来源: IET