Generation of broadband sub-Poissonian-light in light-emitting diodes

Summary form only given. Generally, light-emitting diodes (LEDs) are considered to be low-performance devices in comparison with laser diodes (LDs). However, for future applications such as the parallel inter- or intra-integrated-circuit chip optical-connections, where very low power-consumption is required for the light emitters, a LED can be a very attractive device because of the threshold-free input-output characteristics. So far, continuous efforts have been made to improve the performance of LEDs. In this paper, we focus on another very important aspect, i.e. the noise characteristics. In comparison with LDs, in general, LEDs exhibit excellent noise characteristics, particularly at low injection levels. We show that the intensity fluctuation of the output light from an LED can be squeezed below the full shot-noise (FSN) level in a wide frequency range up to 800 MHz at room temperature. Such a squeezing bandwidth, three orders of magnitude wider than that in the first report on shot-noise suppression in a LED and rather close to the widest bandwidth (1.1 GHz) obtained with LDs at 77 K has been believed to be impossible. In addition, use of a separate confinement hetero(SCH-) structure in the active region allowed us to use a moderate doping concentration (5 /spl times/ 10/sup 18/ cm/sup -3/), resulting in a sufficiently high internal quantum efficiency, /spl sim/30%.