Robust 2 × 2 Multimode Interference Optical Switch

Abstract

A robust 2 × 2 photonic switch based on multimode interference (MMI) effects is proposed. We demonstrate that the device is very tolerant to material modifications and typical fabrication errors. This is a result of the MMI design and the high symmetry of the switch. The key parameter for the operation of the device is that the input light forms a pair of well defined self-images exactly in the middle of the switch. The index modulated regions precisely overlap the positions where these two self-images are formed. By creating identical contact features at these locations, any refractive index change induced in the material as a result of electrical isolation will be replicated in both self-images, and therefore the off-state output will not be altered. In the same way, offset and dimension errors are reflected symmetrically on both self-images and do not seriously affect the imaging. The characteristics of the switch under different scenarios are investigated using the finite difference beam propagation method. By employing this configuration, crosstalk levels better than −20 dB are achievable over a wavelength range of 100 nm while maintaining polarization independence.

Modeling of a high-performance multimode interference optical switch using reconfigurable image modulated region

“…We have modeled 2 × 2 tunable MMI switches realized with straight waveguides, which have substantially smaller device geometries than the MMI switches reported earlier. [14][15][16] Existence of stable and clear images in symmetric waveguides and inbuilt IM regions in a high refractive index contrast has been theoretically verified. Use of reconfigurable additional IM region to enhance the switch performance is elaborated in detail.…”

“…11 LN can provide excellent transmission characteristics while maintaining a high extinction ratio and low power operation. This article deals with MMI structure and use of their self-imaging principle [12][13][14][15][16] to design 2 × 2 MMI switches by defining the partial refractive index regions in the coupling area. The devices have been simulated for a popular communication wavelength of 1.55 μm.…”

Use of Reconfigurable IM Regions to Suppress Propagation and Polarization Dependent Losses in a MMI Switch

“…[12][13][14][15] Index profile of the channel waveguides is chosen in the range of 2.10-2.20 in agreement with available data and the literature survey to investigate the switching characteristics. Various EO/TO crystals such as Ti-indiffused or proton exchanged lithium niobate (α : LiNbO 3 ), lithium tantalate (LiTaO 3 ), potassium niobate (KNbO 3 ), barium-sodium niobate (BNN), strontium-barium niobate (SBN), bismuth germinates crystals of evlitine structure (Bi 4 Ge 3 O 12 ), lithium iodate (α -LiIO 3 ) etc.…”

Multimode interference photonic switches

“…40,41 After that, several photonic switches have been proposed using the IM inside the MMI section to modify the phase relation between the self-images. 9,37,[42][43][44][45][46][47] The switching mechanism of all these switches is the same-they operate by modifying the refractive index at specific areas within the MMI waveguide, which are collocated with the occurrence of multiple self-images. This change in the refractive index effectively alters the phase relation between the selfimages, which ultimately modifies the output image and switches the light between the output waveguides.…”