摘要:

A saddle point variational principle, for estimating the propagation constant of an optical rib waveguide mode from a discontinuous trial function, is generalised to provide a theoretical underpinning for the familiar effective index method. It is shown that better accuracy can be achieved in a rigorous manner, while maintaining much of the simplicity that makes the original effective index approach so attractive.

DOI:10.1049/ip-j.1992.0012

出版商:IEE    

年代:1992

数据来源: IET

摘要:

The guiding mechanism of (AlxGa1−x)0.5In0.5P visible lasers is analysed using a simple effective index approach and is found to be analogous to that of AlGaAs channelled substrate planar lasers. Outside the ridge, the bound mode is leaky, resulting in a real lateral index guide. Furthermore, the loss outside the ridge provides good discrimination against oscillation of higher order modes. The best ridge widths, based on the tradeoff of low loss in the fundamental mode along with high lateral mode discrimination, are in the range 5–7 μm.

DOI:10.1049/ip-j.1992.0013

出版商:IEE    

年代:1992

数据来源: IET

摘要:

Laser interferometry uses the wavelength of light as the unit of measurement, and therefore the absolute wavelength of the source must be accurately known and must be stable. The technique of normal absorption was used to stabilise the frequency of the laser diode output. A molecular iodine vapour having a detailed absorption spectrum was chosen for the stabilisation of visible 670 nm laser diodes. This vapour has a number of absorption features in the 600–700 nm spectrum range which enabled the frequency stabilisation of several visible output laser diodes. At 670 nm a relative frequency stability of ±42 MHz was achieved over a period of 20 min with an Allan variance of between 1.5 MHz and 200 kHz over an averaging time between 2.5 and 250 ms.

DOI:10.1049/ip-j.1992.0014

出版商:IEE    

年代:1992

数据来源: IET

摘要:

The reciprocal behaviour of an optical switch based on a twin-guide laser-amplifier incorporating active flared output waveguides is reported. It is experimentally demonstrated that the optical switch can operate both as a 1×2 splitter switch and as a 2×1 combiner switch, depending on the propagation direction of the input signal(s).

DOI:10.1049/ip-j.1992.0015

出版商:IEE    

年代:1992

数据来源: IET

摘要:

III–V integrated circuits associating on one hand a photoconductive detector and on the other hand an MSM photodetector with HIGFETs for optical clock distribution are presented. First, static and dynamic properties of these planar photodetectors are studied, taking into account the main characteristics of their structures (ion implantation for photoconductive detectors and AlxGa1−xAs upper layer withx=0.45 for MSM photodetectors). Secondly, their integration with a III–V digital IC is reported. This IC includes a divider by two and its operation has been investigated up to 1.2 GHz.

DOI:10.1049/ip-j.1992.0016

出版商:IEE    

年代:1992

数据来源: IET

摘要:

Under some simplifying assumptions, an inequality is derived which must be satisfied for a pair of index guided coupled waveguide semiconductor lasers to be phase-locked. The physically realistic situation of small technological differences between the devices is included. If this criterion is not met then, in the most severe case, the system operates in a scanning mode whereby the far-field pattern scans with a period of a few hundred picoseconds. If phase locking is only weakly broken a stable far-field pattern results, punctuated by periodic phase jumps of 2π.

DOI:10.1049/ip-j.1992.0017

出版商:IEE    

年代:1992

数据来源: IET