Cascaded modulator architecture for WDM applications

Abstract

Integration density, channel scalability, low switching energy and low insertion loss are the major prerequisites for on-chip WDM systems. A number of device geometries have already been demonstrated that fulfill these criteria, at least in part, but combining all of the requirements is still a difficult challenge. Here, we propose and demonstrate a novel architecture consisting of an array of photonic crystal modulators connected by a dielectric bus waveguide. The device architecture features very high scalability and the modulators operate with an AC energy consumption of less than 1fJ/bit. Furthermore, we demonstrate cascadeability and multichannel operation by using a comb laser as the source that simultaneously drives 5 channels.

Recent breakthroughs in carrier depletion based silicon optical modulators

“…The optical modulator is not the only element in the system and therefore can only consume a proportion of this target power. Some state that the maximum power consumption for the modulator should therefore be on the order of 10 fj/bit [55] which is clearly very demanding although some devices have shown potential [51,56]. Ultimately the power consumption required is likely to be driven by the application in which the modulator is to be employed and this will also determine the modulator configuration to be employed.…”

Highly efficient optical filter based on vertically coupled photonic crystal cavity and bus waveguide

“…We fabricated the PhC cavity in a silicon-on-insulator platform [9]. The cavity was created by locally modifying the width of a W1 PhC waveguide.…”

Hybrid photonic crystal lasers

“…The laser cavity is formed by butt-coupling a short Reflective Semiconductor Optical Amplifier (RSOA) to SOI chips containing tunable Photonic Crystal (PhC) cavity-based resonant reflectors, similar to those of [14], providing a route to accessing the advantages of resonant modulation without the wavelength matching issues. PhC cavities provide very precise control of their resonant wavelengths by lithographic tuning [17], significantly assists channel scalability.…”

“…The RSOA chip was a 250-μm-long InPbased amplifier with HR coated back facet and AR coated front facet, bonded to a ceramic tile/carrier. The Si passive chip was fabricated on a 220-nm SOI platform and comprised an SU8 polymer bus waveguide vertically coupled to a Dispersion Adapted (DA) PhC cavity, with a p-i-n junction extending in the PhC defect as described in [14]. The physical principle behind the functionality of the latter component as a resonant reflector is described in [17,19].…”

“…Traditionally losses have been a major drawback, however, recent developments have largely overcome this issue [11,12] and have enabled a ten times reduction in length [13]. Photonic Crystal cavities based modulators take this to the extreme, providing large reductions in footprint and power consumption relative to ring resonators [14,15], see Figure 1. But the resonant nature of such a modulator makes it intrinsically wavelength selective, creating matching issues between it and the external laser which requires the use of tuning elements and control circuitry [16].…”