Vol. 41, Issue 1, pp. 7-14

Abstract

In most applications of vertical-cavity surface-emitting diode lasers (VCSELs), their stable and efficient single-mode operation is required. In standard VCSEL designs, single-longitudinal-mode operation is assured because of their short optical cavities. There is, however, a real problem, how to reach single fundamental-transverse-mode (SFM) operation, especially in modern intra-cavity contacted VCSELs demonstrating the current-crowding effect close to active-region edges. This problem becomes even more acute in detuned oxide-confined VCSELs, where wavelengths of higher-order transverse modes are distinctly lower than that of the fundamental one. VCSEL structures enable spectral detuning of the cavity modes with respect to the peak value of the optical gain spectrum. Such a red-direction detuning is used in GaInNAs VCSELs designed for the 1300-nm wavelength of the second generation of optical fibre communication. In this case, the above detuning enhances at room temperature the excitation of lower-wavelength higher-order transverse modes spectrally located closer to the peak value of the optical gain than the fundamental one. At elevated temperatures, however, the above detuning is reduced leading to higher values of the optical gain available for the fundamental mode. Then the desired stable and efficient SFM 1300-nm operation may be reached.