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Register a new userIntegrated ultra-high-performance graphene optical modulator
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With the growing demand for massive amounts of data processing transmission and storage it is becoming more challenging to optimize the trade off between high speed and energy consumption in current optoelectronic devices. Heterogeneous material integration into Silicon and Nitride photonics has demonstrated high speed potential but with millimeter to centimeter large footprints. The search for an electro optic modulator that combines high speed with energy efficiency and compactness to enable high component density on chip is yet ongoing. Here we demonstrate a 60 GHz fast (3dB roll off) micrometer compact and 4 fJ per bit efficient Graphene based modulator integrated on Silicon photonics platform. Two dual Graphene layers are capacitively biased into modulating the waveguide modes optical effective index via Pauli blocking mechanism. The electro optic response which is further enhanced by a vertical distributed Bragg reflector cavity thus reducing the drive voltage by about 40 times while preserving an adequate modulation depth (10 dB). Compact efficient and fast modulators enable high photonic chip density and performance with key applications in signal processing sensor platforms and analog and neuromorphic photonic processors.
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High performance integrated electro-optic modulators operating at low temperature are critical for optical interconnects in cryogenic applications. Existing integrated modulators, however, suffer from reduced modulation efficiency or bandwidth at low temperatures because they rely on tuning mechanisms that degrade with decreasing temperature. Graphene modulators are a promising alternative, since graphenes intrinsic carrier mobility increases at low temperature. Here we demonstrate an integrated graphene-based electro-optic modulator whose 14.7 GHz bandwidth at 4.9 K exceeds the room-temperature bandwidth of 12.6 GHz. The bandwidth of the modulator is limited only by high contact resistance, and its intrinsic RC-limited bandwidth is 200 GHz at 4.9 K.
We report enhanced nonlinear optics in complementary metal oxide semiconductor compatible photonic platforms through the use of layered two dimensional (2D) graphene oxide (GO) films. We integrate GO films with silicon on insulator nanowires (SOI), high index doped silica glass (Hydex) and silicon nitride (SiN) waveguides and ring resonators, to demonstrate an enhanced optical nonlinearity including Kerr nonlinearity and four wave mixing (FWM). The GO films are integrated using a large area, transfer free, layer by layer method while the film placement and size are controlled by photolithography. In SOI nanowires we observe a dramatic enhancement in both the Kerr nonlinearity and nonlinear figure of merit (FOM) due to the highly nonlinear GO films. Self phase modulation (SPM) measurements show significant spectral broadening enhancement for SOI nanowires coated with patterned films of GO. The dependence of GO Kerr nonlinearity on layer number and pulse energy shows trends of the layered GO films from 2D to quasi bulk like behavior. The nonlinear parameter of GO coated SOI nanowires is increased 16 fold, with the nonlinear FOM increasing over 20 times to a FOM greater than 5. We also observe an improved FWM efficiency in SiN waveguides integrated with 2D layered GO films. FWM measurements for samples with different numbers of GO layers and at different pump powers are performed, achieving up to 7.3 dB conversion efficiency (CE) enhancement for a uniformly coated device with 1 layer of GO and 9.1 dB for a patterned device with 5 layers of GO. These results reveal the strong potential of GO films to improve the nonlinear optics of silicon, Hydex and SiN photonic devices.
Silicon nitride (SiN) waveguides with ultra-low optical loss enable integrated photonic applications including low noise, narrow linewidth lasers, chip-scale nonlinear photonics, and microwave photonics. Lasers are key components to SiN photonic integrated circuits (PICs), but are difficult to fully integrate with low-index SiN waveguides due to their large mismatch with the high-index III-V gain materials. The recent demonstration of multilayer heterogeneous integration provides a practical solution and enabled the first-generation of lasers fully integrated with SiN waveguides. However a laser with high device yield and high output power at telecommunication wavelengths, where photonics applications are clustered, is still missing, hindered by large mode transition loss, nonoptimized cavity design, and a complicated fabrication process. Here, we report high-performance lasers on SiN with tens of milliwatts output through the SiN waveguide and sub-kHz fundamental linewidth, addressing all of the aforementioned issues. We also show Hertz-level linewidth lasers are achievable with the developed integration techniques. These lasers, together with high-$Q$ SiN resonators, mark a milestone towards a fully-integrated low-noise silicon nitride photonics platform. This laser should find potential applications in LIDAR, microwave photonics and coherent optical communications.
We report second harmonic generation from a titanium indiffused lithium niobate waveguide resonator device whose cavity length is locked to the fundamental pump laser using an on-chip phase modulator. The device remains locked for more than 5 minutes, producing more than 80% of the initial second harmonic power. The stability of the system is seen to be limited by DC-drift, a known effect in many lithium niobate systems that include deposited electrodes. The presented device explores the suitability of waveguide resonators in this platform for use in larger integrated networks.
Nanoscale and power-efficient electro-optic (EO) modulators are essential components for optical interconnects that are beginning to replace electrical wiring for intra- and inter-chip communications. Silicon-based EO modulators show sufficient figures of merits regarding device footprint, speed, power consumption and modulation depth. However, the weak electro-optic effect of silicon still sets a technical bottleneck for these devices, motivating the development of modulators based on new materials. Graphene, a two-dimensional carbon allotrope, has emerged as an alternative active material for optoelectronic applications owing to its exceptional optical and electronic properties. Here, we demonstrate a high-speed graphene electro-optic modulator based on a graphene-boron nitride (BN) heterostructure integrated with a silicon photonic crystal nanocavity. Strongly enhanced light-matter interaction of graphene in a submicron cavity enables efficient electrical tuning of the cavity reflection. We observe a modulation depth of 3.2 dB and a cut-off frequency of 1.2 GHz.
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