High output power injection lasers

In an injection laser having an active layer of narrow bandgap and high refractive index for guided optical wave propagation, said laser including a cladding layer provided on adjacent sides of said active layer and having a substantially lower index of refraction relative to said active layer, said cladding layers of very thin cross-sectional thickness, their minimum thickness being sufficient to confine injected carriers to said active layer but permit extension of the optical wave propagation beyond said cladding layers, a further layer provided on the surface of each of said cladding layers remote from said active layer, said further layers having a relatively large thickness compared to said cladding and active layers to confine the optical wave thereto, said further layers having an index of refraction intermediate of said active layer and said cladding layers, the index of refraction of said further layers being chosen to be lower than the equivalent refractive index of the fundamental mode of the guided optical wave.

In an injection laser comprising a plurality of contiguous layers of semiconductor material, one of said layers fabricated to have a lower bandgap and a higher refractive index than said other layers to form an active layer for optical wave propagation under lasing conditions, said active layer being sandwiched by two first layers each of semiconductor material having a higher bandgap and a lower refractive index than said active layer, said first layers forming an optical waveguide for said optical wave propagation, a thin second layer contiguous with said first layer and a third layer contiguous with said second layer, said second layer having a higher bandgap and lower refractive index than any of said other layers, said second layer of thinner cross-sectional thickness compared to the thickness of any of the other of said layers, said second layer thickness being sufficiently thin to provide high optical loss for higher order transverse modes but sufficiently thick to provide low optical loss for the lowest order transverse mode, the refractive index of said third layer being greater than the equivalent refractive index of the higher order transverse modes of the guided optical wave.

In an injection laser comprising a plurality of contiguous layers of semiconductor material, one of said layers fabricated to have a lower bandgap and a higher refractive index than said other layers to form an active layer for optical wave propagation under lasing conditions, a first layer contiguous with one surface of said active layer and of semiconductor material having a higher bandgap and a lower refractive index than said active layer but sufficient in closeness thereto to form an applied waveguide for said optical wave propagation, said active and first layers being sandwiched by two second layers each having a higher bandgap and lower refractive index than any of said other layers, said second layers being sandwiched by two outer third layers, one of said second layers being sufficiently thin in thickness to provide high optical loss for higher order modes but sufficiently thick to provide low optical loss for the lowest order transverse mode, the refractive indices of said third layers being greater than the equivalent refractive index of the higher order transverse modes of the guided optical wave.