Compact InP-based ring lasers employing multimode interference couplers and combiners

Abstract

Multimode interference (MMI) 3 dB couplers and MMI power combiners have been integrated with compact InP/InGaAsP ring lasers (R=150 μm). Radiative loss from the curves is small, and MMI 3 dB couplers are shown to be more efficient than conventional Y junctions. In addition, we demonstrate improved efficiency by combining counterpropagating beams in a single output by means of a MMI combiner. Single mode spectral behavior, with 35 dB side mode suppression, has been measured and is explained as resulting from coupled cavities.

Optical multi-mode interference devices based on self-imaging: principles and applications

“…The selective excitation requirement dictates an increase in the multimode waveguide width-and therefore in its length (see (6))-which cancels out the potential length reduction. However, general interference mechanisms in weakly guiding structures may suffer from higher losses than paired interference, due to decreased image resolution (Section 6.2).…”

“…The first ring lasers using MMI 3-dB outcouplers ( L = 233 pm) were reported for Xo z 1.6 pm in GaInAsP/InP using deeply etched waveguides thereby enabling low-loss R = 150 pm bends [5], [6]. A differential quantum efficiency of qext = 3.9% was reported with almost kink-free LI curves at CW operation and at 20°C [6].…”

“…A differential quantum efficiency of qext = 3.9% was reported with almost kink-free LI curves at CW operation and at 20°C [6]. An additional MMI combiner has been used to combine both counter-propagating beams in a single output waveguide, thereby increasing the efficiency to vext = 5.2% [6].…”

“…Optical devices based on MMI effects fulfil all of the above requirements, and their excellent properties and ease of fabrication have led to their rapid incorporation in more complex PICs such as phase diversity networks [l], MachZehnder switches [2] and modulators [3], balanced coherent receivers [4], and ring lasers [5], [6]. This paper reviews the principles and properties of MMI devices and their applications.…”

Recent advances in miniaturized optical gyroscopes

“…The first one has very strong intracavity back-reflection, while this is negligible in the case of the evanescent coupler, even if this latter requires a very accurate fabrication process because of the very small gap between the resonator and the waveguide. For the MMI coupler the fabrication tolerance is not so stringent and intracavity back-reflection is weak [22,23].…”