the transverse cross section to regions have a length to width ratio in excess of 1 2 favors emission with polarization in the long dimension at the fundamental mode a cruciform structure favors emission with switchable orthogonal polarization the transverse shape can be configured by dry etching a particular cavity shape in index guided lasers or by forming a shaped ion implantation region around gain guided lasers application_number US 3786793 A description referring to the drawings fig1 is a perspective view of a surface emitting laser 9 whose active area has been configured into a rhomboidal diamond shape abcd in longitudinal cross section laser 9 comprises in essence an active region 10 disposed between a pair of distributed bragg reflector stacks 11 and 12 the structure is fabricated on a semiconductor substrate 13 such as n type gallium arsenide the inner reflector stack 11 comprises a periodic sequence of layers such as layers of aluminum gallium arsenide and aluminum arsenide advantageously the layers of inner stack 11 are doped with the same type impurity as the substrate the active region 10 can comprise alternating barrier layers and quantum well layers such as alternating layers of aluminum gallium arsenide and gallium arsenide alternatively the active region can be a gaas heterostructure the outer reflector stack 12 is made up of periodic layers such as p type aluminum gallium arsenide and aluminum arsenide regions 14 peripheral to the active region 10 are either etched away as.