Nanowires and sidewall Bragg gratings in silicon as enabling technologies for microwave photonic filters

Abstract

We describe the use of various silicon photonic device technologies to implement microwave photonic filters (MPFs). We demonstrate four-wave mixing in a silicon nanowire waveguide (SNW) to increase the number of taps for MPFs based on finite impulse response filter designs. Using a 12 mm long SNW reduces the footprint by five orders of magnitude compared to silica highly nonlinear fiber while only requiring approximately two times more input power. We also demonstrate optical delays based on serial sidewall Bragg grating arrays and step-chirped sidewall Bragg gratings in silicon waveguides. We obtain up to 63 ps delay in discrete steps from 15 ps to 32 ps over a wide bandwidth range from 33 nm to at least 62 nm. These components can be integrated with other silicon-based components such as integrated spectral shapers and modulators to realize a fully integrated MPF.

Generating UWB and Microwave Waveforms Using Silicon Photonics

“…As with the systems described previously, it is based on a FIR MPF. Partially degenerated four wave mixing (FWM) in a nonlinear medium is used to increase the number of optical carriers/taps [18]- [20]. In particular, at least N = 2M taps can be obtained starting from M sources.…”

“…The SNW is 20 mm in length and has a cross-section of W × H = 500 nm × 220 nm with a top oxide cladding. It is designed to have a small amount of anomalous dispersion near 1550 nm with a dispersion slope ∼0 ps/(nm 2 ·km) for broadband FWM [20]. Vertical grating couplers (VGCs) are used for input and output coupling and to ensure operation with TE-polarized light in the SNW.…”

Nonlinear Integrated Microwave Photonics

“…On-chip ultrafast Kerr nonlinearity has been exploited in the context MWP signal processing for ultra-wideband (UWB) signal generation [36] and reconfigurable multi-tap filtering [37]. In [36], Tan et al combine the effects of cross-phase modulation (XPM) and birefringence in an As 2 S 3 rib waveguide to generate polarity-inverted UWB monocycles with a single optical carrier.…”

“…Very recently, Chen et al [37] have reported a step towards the integration of a reconfigurable MWP filter concept in [14], by exploiting an FWM process in a silicon nanowire, instead of using HLNF. The silicon waveguide (h= 220 nm, w= 650 nm, length= 12 mm) was dispersion engineered to yield broadband FWM.…”

Subwavelength grating waveguide devices in silicon-on-insulators for integrated microwave photonics (Invited Paper)

“…MRRs can be cascaded to obtain higher-order filter responses or to provide time delays [5] . A serial array of BGs at different resonant wavelengths can also be used to implement a discretely tunable delay line [19] . Cascaded MRRs with different resonant wavelengths (i.e., unique wavelengths within an FSR) or BGs can be used as spectral shapers for generating chirped microwave waveforms based on the principle of spectral shaping followed by wavelengthto-time mapping [7,20,21] .…”