Broadband Wavelength Filter Device using Sidewall Grating for Filtering Optical Signals

Technology: Broadband Wavelength Filter Device with grating structure;

Industry: Electronic Hardware, ICT, Photonics;

Application: Semiconductor, Optoelectronics;

Market: The global filter market by wavelength is projected to reach $158.76B by 2030, at a CAGR of 8.22% during (2023-2030)

Generally, the Silicon-on-Insulator waveguides has a compact design and prominent wavelength dependent characteristics with sub-wavelength grating which makes the SOI waveguides sought after in many applications.
Further many SOI waveguides are used like multilayer interference filters. In conventional filters, the fundamental mode of the optical signal is passed along with the unwanted higher order modes, leading to loss of power & causing signal interference.
In conventional DBR filters broad band pass wavelength response is not possible.
Hence, there is a need to address above issues in efficient manner.

Present invention describes a Broadband wavelength filter device, and a method for fabricating said broadband wavelength filter device for filtering optical signals.
Said broadband wavelength filter device comprises a buried oxide layer, a silicon layer over the buried oxide layer;
Moreover, said silicon layer comprises an input & output waveguide and an optical filtering portion and input & output taper region.
Said Input waveguide and output waveguide is used to operate in a fundamental mode of transverse electric (TE) field.
Further, the optical filtering portion is to operate in the fundamental mode and a first order mode.
Input & output taper region filters out higher order leaky modes leading to remove loss of power & signal interference.
The below smart chart along with figure describes the steps involved in the proposed method for fabricating a broadband wavelength filter device for filtering optical signals. (Refer Figs.2 & 3)

Technical Perspective & Industrial Perspective:

Provide a broadband wavelength filter device, & the waveguide structure over the buried oxide (SiO2) is unique & it comprises multimode waveguide, wherein the distributed Bragg grating (DBR) structure describes the optical filtering portion which is configured in between two single mode input, & output waveguides. (Refer Fig. 1)
Using sidewall grating for filtering optical signals.
Provide an optical filtering portion in the broadband wavelength filter device, with periodic perturbations on one side such that the optical filtering portion supports at least two modes i.e., a fundamental mode & a first order mode, which couples back with forward propagating fundamental mode thus resulting broadband filter response. However, propagating further in backward direction, it travel through taper region followed by single mode input waveguide, hence removing higher order leaky mode which in turn remove interference & signal cluttering. Hence, facilitates said device to filter higher order leaky modes.
Advantageous in obtaining all the power in the fundamental mode of the transverse electric mode & neglects the power in the first order mode.
Applicable as a broad band pass wavelength filter in an on chip optical WDM networking system/Raman spectroscopy.

Prof. Bijoy Krishna Das

Department of Electrical Engineering

TRL-2/3

Proof of concept tested in Lab

Technology Transfer