Abstract

Two Photon Absorption (TPA) is a non-linear optical-to-electrical conversion process that can be significantly enhanced by placing the active region within a resonance microcavity [1]. Such a structure exhibits a resonance wavelength-selective characteristic dependent on the cavity design. This makes a microcavity detector a good candidate for applications in WDM systems, as the wavelength selective characteristic of the cavity can replace the need for additional optical filters. Furthermore the possibility of tuning the resonance wavelength by tilting the cavity such that the incident angle of the light is varied, gives a possibility of using the non-linear TPA response in a single device for monitoring or sampling of wavelength channels in a WDM system [2], Fig 1 (a) presents the TPA photocurrent generated within the resonance microcavity as a function of incident wavelength for a 10 GHz optical pulse train. From the plot the cavity resonance width measured at the 3dB point is 7nm. Fig. 1 (b) presents the cavity resonance wavelength as a function of incident angle. The cavity resonance wavelength for normal incident light is 1563 nm and can be tuned downwards by 60nm when the cavity is tilted by 60°. As the sampling pulse source used had a small tuning range and could not access the peak resonance wavelengths of the device at normal incidence, the cavity was tilted by 20° during the experiment, resulting in off-incidence resonance wavelength of 1557 nm.

© 2007 IEEE