High extinction ratio on-chip pump-rejection filter based on cascaded grating-assisted contra-directional couplers in silicon nitride rib waveguides

Abstract

We present an on-chip filter that is based on the gratingassisted contra-directional coupler (GACDC) implemented on a silicon nitride rib waveguide platform. This filter enjoys the benefit of an unlimited free spectral range (FSR) on the red side of the stop/pass band. Not like a Bragg reflector, the GACDC filter has the advantage of coupling the rejected light into a bus waveguide, instead of reflecting it into the input. This property makes it an add/drop filter suitable for pump rejection and allows effective cascading between multiple stages to provide even higher rejection ratio compared to the single stage version. In this work, we experimentally show that a 16-stage cascaded GACDC filter possesses a stop band with a bandwidth smaller than 3 nm and rejection ratio as high as 68.5 dB.Recently, silicon nitride (SiN) has become one of the most prominent platforms for the miniaturization of photonic circuits in the visible or near infrared range (< 1 µm), where the silicon is no longer transparent [1]. Like the silicon-on-insulator (SOI) technology, SiN nanophotonics is also a CMOS-compatible technology that allows large-scale, cost-effective fabrication of photonic integrated circuits together with the possibility to cointegrate the electronics.A wide range of high-performance components, including grating couplers [2], polarization splitters [3], and wavelength selective filters [4], have been developed on the silicon nitride platform to open the road to further integration of complicated on-chip systems [5][6][7]. As an essential component, the on-chip wavelength filter has attracted a lot of attention from researchers interested in on-chip lasers [8], optical sensors [9] as well as wavelength-division multiplexers [10]. Filters based on the Bragg gratings, ring resonators, and Mach-Zehnder cascades have been studied and demonstrated to meet the requirement

Waveguide-based surface-enhanced Raman spectroscopy detection of protease activity using non-natural aromatic amino acids

“…Currently, we still need to use the Raman confocal microscope to measure the SERS spectra of the nanoplasmonic slot waveguide. In the last years, several papers were published which explore how to implement the functionalities of the Raman microscope on an integrated photonic chip, including a III/V integrated laser [43], integrated filters [44], a waveguide-based collection region [19] and an on-chip spectrometer [45]. Further effort is however needed to ensure the compatibility of all the different components and integrate them on the same photonic chip.…”

Mitigation of photon background in nanoplasmonic all-on-chip Raman sensors

“…The obvious answer to the demand for cheap and compact Raman systems lies in the nanophotonic integration of those elements on a single photonic chip. All the elements have indeed been demonstrated individually: spectrometers [1][2][3], lasers [4,5], spectral filters necessary to remove the strong excitation radiation [6] and also Raman sensors that boost the Raman response [7][8][9]. Recent progress [10][11][12][13][14] has been made regarding the Raman sensor itself by taking advantage of the evanescent field around a dielectric waveguide that allows an analyte to be probed over long optical path lengths.…”

“…Proceeding to integrate this sensor with a circuit capable of analyzing the Raman scattered light demands that no further inelastic scattering or photoluminescence occurs in the circuit surrounding the sensor. Unfortunately, the Raman-like background from the dielectric waveguide (in our case a silicon nitride waveguide [16]) becomes significant over propagation distances that can easily exceed millimeters for spectral filters [6] or AWG. The resulting background ultimately limits the concentration of analytes that can be probed because of the shot noise associated to it.…”

The Structural, Electronic, and Optical Properties of Ge/Si Quantum Wells: Lasing at a Wavelength of 1550 nm

“…We have seen that the material palette of silicon photonics extends well beyond silicon to incorporate low-loss waveguides, efficient modulators and detectors and to produce optical gain. Apart from silicon-based light sources, other silicon-based photonic devices, such as waveguides [1,2], gratings [3,4], modulators [5,6], detectors [7,8], polarization splitters [9], mixers and filters [10], have been realized. Nevertheless, the realization of a silicon-based light source remains an urgent issue in the field of silicon-based photonic devices.…”