Fabrication of long-wavelength-range quantum wire lasers

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When quantum wires is applied to vertical cavity surface emitting lasers (VCSELs), a problem of polarization switching is expected to be resolved where the polarization direction changes by 90 degrees with increasing the excitation current of VCSELs. Quantum wires (QWRs) have preferential gain for the light with the polarization along the wire direction and stabilize the polarization of the laser light from VCSELs. There is no paper reports the stabilization of polarization for the 1.3-1.55 μm range VCSEL QWRs. The purposes of our project are to develop 1.3-1.55 μm range QWRs with (i)high density (>3 x 10^5 cm^<-1>), (ii)high uniformity (PL FWHM<10 meV at 20 K), (iii)high lateral confinement energy (>30 meV), (iv)enough high optical quality for application to laser diodes at the same time, and to achieve room temperature oscillation of QWR-VCSELs and QWR stripe laser using such high quality quantum wires. After three-years project, we achieved all of most important purposes.Three layer … More s of In_<0.53>Ga_<0.47>As/In_<0.52>Al_<0.48>As QWRs were stacked and they have (i)a density of 4.5×10^5 cm^<-1>, (ii)PL FWHM of 9.7 meV at 15 K,55 meV at 300 K (iii)lateral confinement energy of 91 meV calculation, (iv)much improved optical quality by post-annealing process. The results indicate we have successfully developed high quality QWRs with four specifications at the same time. Stripe contact type laser showed room-temperature lasing at a threshold current density of J_<th>=5.3 kA/cm^3.On the other hand, 1.55-μm range QWRs grown on (775)B InP substrates have a density of 2.4×10^5 cm^<-1> (ii)PL FWHM of 44 meV at 300 K (iii)layer thickness modulation of 3.6-10.8 nm which implies that enough high lateral confinement energy (iv)high optical quality. Only the first specification is not fulfilled. Nine stripe contact lasers show room temperature lasing at a threshold current of 4.0 kA/cm^3 (average), and 2.8 kA /cm^3 (minimum). The quantum wires were grown at a growth rate of 2 μm/h, which is two times faster than the conventional growth rate and necessary for the fabrication of 40 μm thick distributed Bragg reflector. VCSEL with the QWRs lased at 1517 nm at room temperature with a polarization parallel to the wire direction.We also fabricated VCSELs with (775)B GaAs/(AlAs)_1(GaAs)_6 QWRs and with (775)B GaAs/(AlAs)_1(GaAs)_6 QWRs and both VCSELs showed room temperature laser oscillation. by current excitation. For the GaAs QWR VCSEL, the lasing wavelength is 769 nm and orthogonal polarization suppression ratio (OPSR) 20 dB over wide-range of current. There is no paper report the such a high OPSR value for the VCSEL with GaAs active layer. The result indicates that (775)B GaAs QWRs realizes the high stability of polarization of VCSELs. Less