AlGaAs hot-electron optical modulator

Abstract

We propose and analyze a promising surface-normal optical modulator for use in optical interconnects. The device is based on n-AlGaAs materials, operating with red light, and is therefore fully compatible with silicon photodetectors. The operation principle is based on current-induced electron heating, with redistribution of carriers between conduction band valleys playing a significant part. Calculations predict efficient absorption modulation with operating voltages <1 V and switching times of units of picoseconds.

Effect of carrier loss through waveguide layer recombination on the internal quantum efficiency in large-optical-cavity laser diodes

“…3, the broadening of the waveguide, required for improving the beam divergence and possibly to avoid catastrophic degradation, can lead to a drastic reduction in the internal quantum efficiency i due to the increased carrier density in the "p OCL." In our previous paper, 18 we showed that the same effect may also lead to a significant degradation of the slope efficiency, due to an increased free-carrier absorption in the OCL. To alleviate this danger while preserving the broad equivalent spot size, we proposed the use of a narrow but asymmetric waveguide structure.…”

“…15, we consider the case when the current in the OCL is to a significant extent controlled by diffusion and, correspondingly, the carrier density distribution is not flat across the OCL. In our previous work, 18 this carrier distribution was evaluated for the case when the recombination in the OCL can be neglected, and it was shown that the part of the carrier density proportional to the current in the part of the OCL adjacent to the n contact ͑0 Ͻ x Ͻ l a ͒ is usually negligible compared to its counterpart in the other side of the OCL, adjacent to the p contact ͑l a Ͻ x Ͻ h͒, due to the electron mobility being much higher than that of holes. The recombination does not change this relationship of mobilities and hence of carrier densities; therefore, below, we shall concentrate our analysis on the "p side" of the OCL ͑between the active layer and the p cladding, l a Ͻ x Ͻ h͒, assuming that the total carrier recombination in the n side, and thus its contribution to the internal efficiency reduction, is negligible.…”

“…As in Ref. 18, we shall consider a structure ͑Fig. 1͒ with a narrow active layer consisting of, say, one to three quantum wells embedded in the OCL at a certain position x = l a .…”

“…In our previous work, 18 we have shown that the presence of current-supplied carriers in the OCL, even with N l = 0, can a͒ Electronic mail: ryvkin@switch.ioffe.rssi.ru b͒ Electronic mail: eaa2@ohm.york.ac.uk; FAX: ϩ44-1904-432335. lead to significant optical loss ͑due to free-carrier absorption͒, which increases with the OCL thickness h ͑roughly as h 2 ͒ and can be one of the reasons of the output efficiency decrease at high currents and suggested using narrow asymmetric waveguide structures as one possible means of reducing the effect.…”

Polarization-dependent intersubband absorption saturation and its effect on polarization selection in vertical cavity surface-emitting lasers

“…The absorption coefficient for light polarized in parallel to the polarization of the saturating radiation ͑in the direction x͒ can be expressed, following Ref. 22, as…”