A reconfigurable architecture for continuously variable optical slow-wave delay lines

Abstract

A novel reconfigurable architecture based on slow-wave propagation in integrated optical ring resonators is proposed for the realization of variable optical delay lines. A continuously variable delay is achieved by combining a coarse discrete (digital) delay, provided by a coupled resonator slow-wave structure, with a fine continuous (analog) delay given by a cascaded ring- resonator phase-shifter. The reflective configuration of the structure enables a simple, accurate and robust tuning of the delay and provides a footprint reduction by a factor 2 with respect to conventional coupled resonator optical waveguides. Proof-of-concept devices realized in 4.4% silicon oxynitride waveguides and activated by a thermal control are discussed. Experimental results demonstrate, in both spectral and time domain, a continuously variable delay, from zero to 800 ps (2 bit fractional delay), on a 2.5 Gbit/s NRZ signal, with less than 8 dB insertion loss and less than 5 mm2 device footprint.

Chains of coupled square dielectric optical microcavities

“…Corresponding studies could concern the slow transfer of light pulses along the chain path (Melloni et al 2003;Poon et al 2006), or the time delay properties (Morichetti et al 2007;Morichetti et al 2008) of a chain when attached to one branch in an interferometer setting.…”

“…A variety of concepts exist; among these are series of microring or -disk resonators (Yariv et al 1999;Little et al 2004;Morichetti et al 2007), sequences of defects in photonic crystals or photonic crystal slabs (Bayindir et al 2000;Reynolds et al 2001;Scheuer et al 2005), and coupled dielectric spheres (Astratov et al 2004;Chen et al 2006). Some configurations can also be viewed as specific extended cases of photonic molecules (Boriskina 2005(Boriskina , 2006Boriskina et al 2007).…”

Tunable optical delay line based on integrated grating-assisted contradirectional couplers

“…However, the delay-bandwidth product of a single microring is limited by 2∕π [16]. To increase the delay-bandwidth product, all-pass filters and coupled resonator optical waveguides with several cascaded microrings have been employed with compact structure and large delay [17][18][19][20][21][22]. In PhCWs, the strong optical confinement and slow light effects were used to realize true-time delay as well, which reduced the footprint and power consumption [23][24][25][26][27].…”

All-Optical Delay Module Using Cascaded Polymer All-Pass-Filter Ring Resonators

“…The resonator slow-wave structure can be implemented using Fabry-Perot resonators [10,11], coupled ring resonators [12][13][14][15][16][17][18][19][20], or coupled defect mode resonators in photonic crystals [21]. CROW's (Coupled Resonator Optical Waveguides), in which a few tens ring resonators are coupled together, have been implemented in the form of glass waveguides or polymer waveguide [12][13][14][15][16][17][18][19][20]. In addition, fixed delay modules in the form of CROW and all pass filters composed of a few hundreds micro-ring resonators have been realized in SOI (Silicon on Insulator) photonic wire waveguide.…”

“…Recently, a CROW with eight rings has been fabricated in SiON waveguide structure and variable delay as long as a few hundreds picoseconds has been demonstrated [19].…”