GaInAsP/InP vertical-cavity surface-emitting laser for 1.5-μm operation

Abstract

Long-wavelength vertical cavity surface emitting lasers (VCSELs) operating in the 1 .3tm to 1 .5im wavelength range are ideal light sources for optical fibre communication applications. However, a number of problems have hindered progress in the development of cost-effective long wavelength VCSELs. These are (a) inthnsically high non-radiative losses, (b) difficulty in fabricating highly reflecting mirrors, lattice-matched to InP, and (c) the disparity between the predicted and observed temperature dependence of the operation of the devices. In this report we present the results of our studies concerning the pulsed operation of a bulk GaInAsP/InP VCSEL fabricated at BT laboratories. The device is tailored to emit at around 1 .5 im at room temperature. The structure has a 45 period n-doped GaInAsPIInP bottom Distributed Bragg Reflector (DBR), and a 4 period Si/A1203 dielectric top reflector. Spectral electroluminescence (EL) from a 16 im diameter window is measured in the pulsed injection mode. Device parameters are recorded in the temperature range between 90 K and 240K. Threshold current exhibits an approximate parabolic temperature dependence with a broad minimum of J = 13.2 kA cm2, at temperatures between 170K and 195K. Temperature dependence of the threshold current is compared with the theoretical calculations which consider radiative transitions with and without k-selection. Best agreement with the experimental results is obtained when a partial k-selection model, with an energy broadening of about 4.4 meV, is used in the calculations.

Temperature dependence of the spontaneous emission factor in microcavities

“…With inclusion of cavity effects, it is seen that the spectrum is large and encompasses a large proportion of the resonant ridge, so there is a large total spontaneous emission. The mode definitions in angle and space, (16) and (17), determine the proportion of the ridge which belongs to the resonant mode and it is seen that β, with cavity effects, is enhanced when compared to β without cavity effects , Fig. 7.…”

“…The result of this change is to move the resonant mode to longer wavelengths with increasing temperature. Experimental data has been reported which shows a linear variation of resonant wavelength with temperature (T) [16,17]. Thus we may write the energy temperature dependence of the cavity resonance E res as E res = 0.84-5.5x10 -5 T (19) where E res is in eV and T in K.…”

“…Integration of the product of the lineshape r sp at threshold and the mode distribution over all energies and angles using 37,47 pairs of layers, yields the total spontaneous emission over angle and energy for the VCSEL in Fig.3. The spontaneous emission in the resonant mode is calculated as above, where the mode definitions (16) and (17) are used as limits of integration.…”

An Intra-cavity bottom emitting 1325 nm VCSEL using GaInAs / GaInP MQWs and AlGaInAs / InP DBRs for epitaxial fabrication

“…InP materials i.e., InAlGaAs/InP QWs and InGaAsP/ InP QWs have been found suitable for long wavelength lasers by a number of researchers [1] [2]. Some researchers worked with GaInAsP/IP QW VCSELs [6]. Subsequently, with the same or similar compound semiconductors researches were done on 1550 nm VCSELs [6].…”

“…Some researchers worked with GaInAsP/IP QW VCSELs [6]. Subsequently, with the same or similar compound semiconductors researches were done on 1550 nm VCSELs [6]. Difficulties also arise in reducing the number of DBR layers to achieve high reflectivity required for a VCSEL because of small difference in refractive indices between the high and low index materials of the DBR layers if lattice matched materials are used.…”