摘要:

The circuit theory of laser diode modulation and noise is based only on the energy and electron-number conservation laws, and on the well known expressionhv(Gb+Ga) for the spectral density of Nyquist noise currents. The conductancesGbandGarepresent stimulated absorption and stimulated emission, respectively. This theory leads to results that are in exact agreement with the predictions of quantum optics, even in the case of electronic feedback and non-classical states of light, but the optical field is not quantised. The theory is presented in a general form, applicable to arbitrary optical and electrical configurations, but is exemplified for only a single active element model of laser diode. For independent electron-hole injection, the results are the same as those obtained from standard rate equations, except for a phase-noise term. Important differences do occur for more realistic laser models.

DOI:10.1049/ip-j.1990.0012

出版商:IEE    

年代:1990

数据来源: IET

摘要:

Spectral gain studies were carried out for two different laser diode structures from the recordings of Fabry-Perot modes. The Cassidy method [1] was found to be superior to other methods for determining gain and for application even at laser threshold. Maximum gain versus current values were derived for both AlGaAs/ GaAs and InGaAsP/InP lasers, and showed good agreement with published theoretical values [2, 3].

DOI:10.1049/ip-j.1990.0013

出版商:IEE    

年代:1990

数据来源: IET

摘要:

The operation principle and fabrication process of the tunable twin-guide (TTG) DFB laser diode are presented. The TTG-DFB laser is a novel single-frequency tunable laser which needs only a single control current for a wide continuous tuning range. Very low cw threshold currents of 12–18 mA at room temperature, spectral line-widths as low as 20–30 MHz, and a continuous tuning range of 1.5 nm at a tuning current of 60 mA are obtained with first, still non-optimised devices. The threshold current and spectral line-width vary only slightly over the entire tuning range.

DOI:10.1049/ip-j.1990.0014

出版商:IEE    

年代:1990

数据来源: IET

摘要:

InGaAs planar-structure PIN photo-diodes fabricated from MOVPE material have been demonstrated to have outstanding reliability. The predicted random failure rate at 20°C is less than 0.3 FITs, and the mean time to failure is estimated to be 1011hours at 20°C. By contrast, the reliability of mesa-structure photodiodes is unacceptable because of an instability of the dark current. A similar kind of instability has been observed in commercially available mesa photodiodes. Extensive life testing of planar-structure and mesa-structure PINs made by several manufacturers shows that the reliability of mesa-structure PINs is inferior in all cases.

DOI:10.1049/ip-j.1990.0015

出版商:IEE    

年代:1990

数据来源: IET

摘要:

We have studied experimentally and theoretically impact ionisation thresholds in the indirect band-gap semiconductors, silicon and germanium. The threshold energies for electron- and hole-initiated ionisation processes were calculated numerically using an empirical pseudopotential band-structure which includes spin-orbit interactions. In silicon, the threshold energy for holes is significantly greater than that for electrons, whereas in germanium the thresholds are almost equal. We point out the band-structure features responsible for this behaviour, and its influence on the multiplication noise of avalanche photodiodes fabricated in these materials. We have measured the breakdown voltage in silicon and germanium avalanche photodiodes while varying the band-structure using hydrostatic pressure. For silicon, the results are consistent with impact ionisation dominated by electron-initiated umklapp processes associated with the Δ minima, in agreement with the calculations. The results for germanium show experimental evidence for impact ionisation above the threshold energy (‘soft’ threshold), and for multiple ionisation processes contributing to the carrier multiplication. We have also calculated the thresholds for impact ionisation in strained silicon grown on (100) germanium, and for strained germanium grown on (100) silicon. The results show that strained layers fabricated in indirect band-gap semiconductors are potentially attractive for use in low-noise avalanche photodiodes.

DOI:10.1049/ip-j.1990.0016

出版商:IEE    

年代:1990

数据来源: IET