摘要:

In semiconductor lasers, spectral hole burning, asymmetrical, longitudinal-mode competition, and population fluctuations in the carrier density are modelled by a nonlinear gain term in the rate equations. For physical, realistic values of the nonlinear gain parameter (10−24m3), period doubling bifurcations and chaotic behaviour resulting from periodic forcing are suppressed in agreement with experimental findings. In the paper we predict the bifurcations as a result of instabilities in the fully nonlinear solutions to the rate equations with nonlinear gain. The predictions are shown to agree with our direct numerical solutions of the rate equations.

DOI:10.1049/ip-j.1988.0054

出版商:IEE    

年代:1988

数据来源: IET

摘要:

An InGaAs-cap-monitor photodiode is monolithically integrated with a 1.55 μm InGaAsP/InP λ/4-shifted DFB laser that has a higher output design. The optical coupling between the laser and the monitor is calculated using a Gaussian beam approximation, which shows that 20–40% of the rear light output can be monitored. The actual ratio of monitor current to front output at a temperature of 10–40°C is typically 0.1–0.2 mA/mW. It is shown that the integrated cap-monitor can be used, not only for the control of the laser power, but also for probing the threshold current and the single-wavelength property of an individual laser in a wafer, without cleaving out into chips. For the laser part with an antireflecting coating on the front facet, the maximum output power of 30 mW at 25°C and the highest CW temperature (as high as 100°C inp-side-up bonding) were obtained.

DOI:10.1049/ip-j.1988.0055

出版商:IEE    

年代:1988

数据来源: IET

摘要:

Recently, there has been considerable interest in superlattice avalanche photodiodes (SAPDs) as photodetectors for optical receivers. This paper describes the influence, on receiver sensitivity, of the number of multiplication stages of these devices, taking into account both residual hole ionisation and dark current. It is shown that SAPDs with a large number of stages only offer a sensitivity improvement when the hole to electron ionisation rate ratiokis kept to a very low value. Askincreases, a small number of stages are required for better sensitivity, and this also facilitates high speed operation.

DOI:10.1049/ip-j.1988.0057

出版商:IEE    

年代:1988

数据来源: IET

摘要:

Fibre-loop reflectors are applied to Nd3+doped fibre lasers operating in the4F3/2→4I11/2transition. The splitting ratio of the fused fibre coupler used in a loop reflector is varied thermo-optically, giving rise to a spectral variation in the reflectivity of the device. Using the fibre loop in a configuration with a broadband dielectric mirror to form a resonant cavity, we demonstrate wavelength tuning of the fibre laser and continuously variable power output for a constant pump power.

DOI:10.1049/ip-j.1988.0058

出版商:IEE    

年代:1988

数据来源: IET

摘要:

A model is proposed in which the conduction band is discretised into energy intervals corresponding to longitudinal-mode separations for the simulation of inhomogeneous broadening and mode beating effects in semiconductor lasers. Four first-order relaxation processes are proposed to take account of intraband relaxations, and mode beating is included as a separate nonlinear gain term in the rate equations. In addition to the usual results of spectral-hole burning, single longitudinal-mode stabilisation and increased damping of relaxation oscillations, the model also accounts for the excitation of nonadjacent longitudinal modes experimentally observed at high bias in narrow planar-stripe lasers and the temperature dependence of spectral behaviour in CSP lasers.

DOI:10.1049/ip-j.1988.0059

出版商:IEE    

年代:1988

数据来源: IET

摘要:

Plane-wave diffraction by metallic reflection gratings with finite conductivity of arbitrary profile is analysed by a new analytical-numerical technique. The obliquely incident radiation is of linear polarisation with either of its fields parallel to the rulings. The solution method is simple, general and numerically efficient. It involves expansion by a Fourier series of the periodic permittivity function in the inhomogeneous grating region, and application of finite differences to numerically solve the inhomogeneous vector-wave equation in this region. Numerical results are presented for several gratings to demonstrate the convergence, reliability and accuracy of the method. They also show effect of the finite conductivity of metal on the diffraction characteristic of gratings.

DOI:10.1049/ip-j.1988.0060

出版商:IEE    

年代:1988

数据来源: IET

摘要:

A theory is developed and compared with experimental results. The theory enables calculation of the curvature loss from a partially buried dielectric waveguide in the presence of a strong air/dielectric planar interface. Comparison is made between numerical predictions based on this theory and experimental results for a smooth waveguide of rectangular cross-section. Agreement is found to be striking, even when the position of the caustic should, in theory, render the waveguide lossy.

DOI:10.1049/ip-j.1988.0061

出版商:IEE    

年代:1988

数据来源: IET