摘要:

A general and simple expression for the natural linewidth of lasers with high, spatially inhomogeneous gain, such as semiconductor lasers, has recently been reported by the author in a short paper. In the present paper, the relation is applied to a number of circuits relevant to semiconductor injection lasers. Its significance is clarified by considering simple lumped circuits. It is further generalised to anisotropic materials which may be nonreciprocal, and the role of dispersion inside and outside the laser cavity is discussed. The theory is restricted to single-mode operation (well above threshold operation), but saturation is neglected.

DOI:10.1049/ip-j.1987.0002

出版商:IEE    

年代:1987

数据来源: IET

摘要:

The waveguiding properties of double heterostructure lasers with nonsymmetrical structure have been investigated. Either large optical cavity (LOC) lasers with separate carrier and optical confinement or distributed feedback (DFB) and distributed Bragg reflector lasers (DBR), respectively, can be investigated easily with the aid of our analytical expressions for the near-field distribution, the confinement factors and the DFB coupling coefficients. Formulas are given here for the first time in analytical form; in connection with analytical expressions for the bulk refractive indexes of the quaternary InGaAsP/InP system they have been used for the design of 2nd-order λ = 1.55 μm DFB lasers. Thus, threshold currents of 12 mA have been achieved experimentally.

DOI:10.1049/ip-j.1987.0003

出版商:IEE    

年代:1987

数据来源: IET

摘要:

Lateral mode stability in index guided semiconductor lasers is discussed. As is well known, the fundamental mode self-focuses at high power due to perturbations in the refractive index profile produced by spatial hole burning. However, the lateral waveguide is not strengthened for all modes. The first order mode, for example, is actually slightly defocused. In strong waveguides the gain profile perturbation due to hole burning is the dominant cause of the first-order mode reaching threshold. In weak wave-guides, however, the defocusing effect can compete with the gain profile perturbation effect leading to stable fundamental mode operation at high output powers.

DOI:10.1049/ip-j.1987.0004

出版商:IEE    

年代:1987

数据来源: IET

摘要:

A numerically efficient model for the evaluation of InGaAsP ridge waveguide laser operation at threshold is presented. It includes the treatment of the electrical behaviour of the junction and an ‘hybrid’ optical waveguide analysis that approximately takes into account the coupling between TE and TM modes at the ridge interfaces. The adopted optical model is slightly more complex than the effective refractive index method and the electrical model gives an almost analytical solution; this allows the use of optimisation routines in designing structures which present minimum threshold current. Numerical results that highlight the advantages of this method in the optical modal analysis are reported and three widely used laser structures are numerically analysed and compared.

DOI:10.1049/ip-j.1987.0005

出版商:IEE    

年代:1987

数据来源: IET

摘要:

The bridge-contacted ridge-waveguide (BCRW) laser structure is used to investigate the influence of the lateral refractive-index step Δneffon lasing characteristics at 1.55 μm wavelength. For this purpose the dependence of δneffon the device parameters is numerically calculated by solving the slab-waveguide problem for the guiding region. It is proved that lateral refractive-index steps up to 10−1can be obtained with the BCRW structure and result in strongly index-guided lasers even for small stripe widths. These BCRW lasers show low CW-threshold currents of 33 mA and quantum efficiencies of 29%. A maximum quantum efficiency of 45% is obtained for δneff$ 8 × 10−3at which the applied index step just compensates carrier-induced antiguiding. It is demonstrated that BCRW lasers can be operated in a stable longitudinal single mode at a side-mode suppression exceeding 20 dB.

DOI:10.1049/ip-j.1987.0006

出版商:IEE    

年代:1987

数据来源: IET

摘要:

From a phenomenological model of InGaAsP/InP double heterostructures emitting around 1.5 μm we have analysed both theoretically and experimentally the influence of the active-layer thickness, cavity length, mirror reflectivity and scattering losses on the useful laser parameters. Due to the high intervalence band absorption and the small electron effective mass of the quaternary material, the external quantum efficiency and the lasing emission wavelength have been found to vary strongly with the active-layer thickness. It is shown that the external quantum efficiency can be increased by reducing the active-layer thickness to less than 0.1 μm and improving the interfaces. Thus BH lasers have been made with a 50% external quantum efficiency and stable fundamental transverse mode up to 35 mW per facet, for 400 μm long devices operating at 300 K. The lasing wavelength, determined by the threshold carrier density, depends on the different laser parameters. As predicted, experiments show a lasing wavelength shift of 400 Å when the active-layer thickness varies between 0.1 and 0.2 μm. Improvement of the LPE process leading to a better control of the thickness uniformity of the active layer has been found determinant in reducing the lasing-wavelength dispersion.

DOI:10.1049/ip-j.1987.0007

出版商:IEE    

年代:1987

数据来源: IET

摘要:

New theoretical and experimental results are presented for optical bistability in distributed feedback amplifiers at 1.5 μm. The onset of bistability occurs at input powers as low as 1 μW, a factor of about 1000 times less than the input predicted for passive DFB structures. The transient response exhibits a large spike as the amplifier goes through a resonance, in good agreement with the theoretical prediction.

DOI:10.1049/ip-j.1987.0008

出版商:IEE    

年代:1987

数据来源: IET

摘要:

This paper reviews optical bistability in semiconductor lasers, with particular reference to the potential switching speeds of the systems demonstrated to date. Devices which switch by redistributing a nearly constant number of carriers within the active region should be faster, although less stable, than systems whose transitions are attended by large changes in carrier numbers. One system of the former type, the self-focused coupled cavity laser, is analysed in some detail and is compared with the twin-stripe laser and the Fabry-Perot laser amplifier.

DOI:10.1049/ip-j.1987.0009

出版商:IEE    

年代:1987

数据来源: IET

摘要:

The occurrence of Hopf bifurcations in twin-stripe semiconductor lasers is predicted using a recently developed formalism for analysis. Control of the bifurcation phenomenon appears to be possible by both electronic and optical means.

DOI:10.1049/ip-j.1987.0010

出版商:IEE    

年代:1987

数据来源: IET

摘要:

Recently a multilongitudinal-mode model for the analysis of cleaved coupled-cavity lasers has been proposed. In this paper the method is described in full detail. The model includes the optical interactions between the two cavities as well as the noise (spontaneous emission) in each of the resonators. It takes several longitudinal modes into account simultaneously and solves the nonlinear field equations self consistently, together with a nonlinear resonance condition for each longitudinal mode. These conditions are coupled with each other, through the nonlinearity of the laser medium. The results of this model are compared with those from an analytic model, based on an effective mirror concept. In a subsequent paper, an extensive study of the device behaviour as a function of various parameters will be presented, as derived from these models.

DOI:10.1049/ip-j.1987.0011

出版商:IEE    

年代:1987

数据来源: IET