Integration of multimode interference device with electroabsorption modulators as simple switches

A 1×2 multimode interference device is monolithically integrated to two electroabsorption modulator based switches at the output ports by means of quantum-well intermixing. At the wavelength range of 1550–1570nm, both arms act as separate DC switches which can be modulated with the extinction ratios of up to 10dB. Monolithic integration of active and passive photonic components is attractive due to its miniaturized size which can simultaneously satisfy multifunctional purposes. The potential of compacted optical circuits along with low-cost batch fabrications and high stability ensures the viability of such endeavours. The integration of an MMI device (passive device) with EAMs (active devices) enables it to be used as a compact multiplexer or optical transmitter. The prototype made is of a relatively larger size (∼2000µm) but its size can be potentially reduced to around 500µm or less. The material structure employed is the InGaAlAs/InGaAlAs MQW with dual depletion structure (DDR) and large optical cavity (LOC) structure design. The LOC material structure was designed for the realization of lower insertion loss. The QWI technology utilized here is the impurity-free vacancy diffusion (IFVD) method and it resulted in a 56nm blue-shift in the bandgap structure. The etching process executed here was the dry etching process using inductively coupled plasma (ICP) etching based on a CH4/Cl2/H2 gas combination. The MMI length is 1150µm whereas the modulators are both 500µm long.