Separate Confinement Heterostructure Layer Research Articles

High-coupling-efficient 1.3-μm laser diodes with good temperature characteristics

We have proposed uniformly beam-expanded structures based on the advanced concept for realizing high coupling efficiency and good temperature characteristics. Beam expansion (optical confinement reduction) by narrowing the core layer width as well as a carrier confinement are strongly enhanced by adopting a larger bandgap InGaAsP for MQW barriers and separate confinement heterostructure layers. These laser diodes (LD's) were fabricated by the conventional buried heterostructure laser process, which is very important in reducing the cost. Our results have proven the effectiveness of our proposition. The LD's with high coupling efficiency (-3.2 dB) and good temperature characteristics have been achieved even using the simple approach of reducing optical confinement. The threshold currents at 25 and 85/spl deg/C are 9.3 and 39.4 mA, respectively. The slope efficiency at 25/spl deg/C is 0.39 W/A and still high (0.26 W/A) even at 85/spl deg/C.

Theoretical analysis of the influence of the barrier composition on properties of GaInAs/GaInAsP/GaInP laser diodes

Recently 980 nm separate confinement heterostructure (SCH) InGaAs/GaInAsP/GaInP lasers have become of great interest because of potential improvements in threshold current and optical far field divergence over SCH InGaAs/GaAs/GaInP lasers. The authors report the first theoretical study on the influence of barrier composition on threshold current density and the optical far field of GaInAs/GaAs/GaInP and GaInAs/GaInAsP/GaInP SCH lasers. The paper presents the CADILAC model for computer-aided design of aluminium-free GaInAs strained quantum well lasers taking into account in particular the effects of strain on modification of the well band structure. A comparison between theoretical and experimental results is reported. The variations of the threshold current density and the transverse far field divergence versus energy bandgap of the SCH layer in multiple quantum well GaInAs/GaAs/GaInP and GaInAs/GaInAsP/GaInP SCH laser emitting at 980 nm are analysed. It is found that the increase of the bandgap energy of the barrier layer causes only a slight degradation of the radiative current density and a reduction of the far field divergence due to the refraction index decrease of the GaInAsP material and to well broadening in order to allow for the emission at 980 nn. Expecting the decrease in barrier current resulting from better confinement of the carriers in GaInAs/GaInAsP wells, these results tend to confirm the superiority of the InGaAs/GaInAsP/GaInP laser as a candidate for the pump sources of erbium-doped fibre optic amplifiers.

Analysis of temperature dependent optical gain of strained quantum well taking account of carriers in the SCH layer

The temperature dependence of optical gain in strained quantum well is analyzed taking account of carriers in the separate confinement heterostructure (SCH) layer. Taking account of these carriers in the SCH layer can explain to a considerable extent the difference in the temperature performance between the /spl lambda/=0.98 μm laser and /spl lambda/=1.3 μm laser. It is shown that well depth plays a crucial role for the temperature dependence of optical gain. A strained quantum well on an InGaAs ternary substrate is shown to give a high gain with a small temperature dependence.

Separate-confinement heterostructure dependence of the effective carrier recombination coefficient of strained InGaAs/InGaAsP multiple quantum well lasers

We experimentally investigated the separate-confinement heterostructure (SCH) layer thickness and SCH band-gap wavelength dependence of the effective carrier recombination coefficient of strained InGaAs/InGaAsP multiple quantum well lasers. The dependence is explained by the carrier transport between the SCH layers and the wells.

High-temperature operation of InGaAs/InGaAsP compressive-strained QW lasers with low threshold currents

We investigated the influence of the band gap wavelength of barrier layers and separate confinement heterostructure (SCH) layers lambda /sub SCH/ on the high-temperature operation of InGaAs/InGaAsP compressive-strained quantum-well (QW) lasers. The optimum lambda /sub SCH/ was 1.2 mu m, at which carriers were sufficiently confined into quantum wells. The QW laser with lambda /sub SCH/ = 1.2 mu m exhibited low threshold currents of 2.3 mA at 20 degrees C and 9.7 mA at 100 degrees C and CW lasing up to 150 degrees C. >

Influence of free carrier plasma effect on carrier-induced refractive index change for quantum-well lasers

The influence of the free carrier component due to the plasma effect on carrier-induced refractive index change and its dependency on polarization for multiple-quantum-well (MQW) and bulk lasers are experimentally studied. The ratios of the component to the total index change, R/sub fc/, are 0.6, 0.4, and 0.1 for 1.3- mu m MQW, 1.3- mu m bulk, and 0.8- mu m MQW lasers, respectively. The TM/TE polarization ratios of the component, R/sub TM/TE/, are 0.8 and 0.3 for 1.3- mu m MQW and 0.8- mu m MQW lasers. The relationship between the index change and the carrier overflow (to barrier and separate confinement heterostructure layers) for MQW lasers is also discussed. Large R/sub fc/ and R/sub TM/TE/ for the 1.3- mu m MQW laser result from the carrier overflow.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>