We report on extended measurements and theory on the recently developed monolithic wavelength demultiplexer consisting of voltage tunable superlattice p-i-n photodetectors in a waveguide configuration. This includes a reduced wavelength spacing, an investigation of the polarization dependence of the crosstalk and bit-error-rate measurements for various crosstalk levels. We show that the device is able to demultiplex and detect two optical signals with a wavelength separation of 20 nm directly

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... to different electrical channels at a data rate of 1 Gbit/s and with a crosstalk attenuation varying between 20 and 28 dB, depending on the polarization. The minimum acceptable crosstalk attenuation at a data rate of 100 Mbits/s is determined to be 10 dB. The feasibility of using the device as a polarization angle sensor for linearly polarized light is also demonstrated. The paper includes a theory for the emission of photogenerated carriers out of the quantum wells since this is potentially a speed limiting mechanism in these detectors. We show that a theory of thermally assisted tunneling by polar optical phonon interaction is able to predict emission times consistent with the observed temporal response. I. INTRODUCTION R ECENT developments in epitaxial growth techniques with monolayer precision such as molecular beam epitaxy (MBE) [1] and metal-organic chemical vapor deposition (MOCVD) [2] have made possible a new class of optoelectronic devices based on physical phenomena in quantum wells and superlattices [3] . In these materials the carriers are confined to thin semiconductor layers. When the layer thickness approaches the Bohr radius, the electronic system enters the quantum regime and the material exhibits modified electrical and optical properties as compared to bulk material [4] . Among these so-called quantum size effects are the step-like density of states function [5], the structure dependent energy spectrum of allowed states [6], the room temperature excitonic nonlinear [7] and polarization dependent [8] absorption, and the enhanced electroabsorption effect [9]. New and improved optoelectronic devices such as quantum well lasers [ 1 0], nonlinear optical elements [11], infrared detectors [12],