Threshold current density of InGaAsP/InP surface-emitting laser diodes with hemispherical resonator

Surface emitting laser diodes (SELD) are characterized by the fact that light is emitted vertically from the surface of the chip. The hemispherical resonator consists of one spherical mirror and one flat mirror placed approximately at the center of curvature of the sphere. In the past, the InGaAsP/InP SELD with hemispherical etched mirror was demonstrated at 77K. The authors have made theoretical calculations, considering material losses, resonator losses and angle deviation from the axis of cavity. The theoretical calculations indicate that in the case of the cavity length L more than 10 micrometers , the InGaAsP/InP SELD with hemispherical resonator is featured by having lower threshold current density Jth than with plane parallel resonator and will be possible in room temperature cw operation by using R equals (root)R1 (DOT) R2 equals 0.75 (Jth is congruent to 80 KA/cm2) or R equals 0.9(Jth is congruent to 25 KA/cm2), L equals 50 micrometers , d equals 1 micrometers and B 1, R2 are reflectivities of planar and hemispherical mirrors separately, d is the active layer thickness and B is the angle deviation from axis of cavity.