No Arabic abstract
Optical isolators, while commonplace in bulk- and fiber-optic systems, remain a key missing component in integrated photonic systems. Isolation using magneto-optic effects has been difficult to implement due to fabrication restraints, motivating use of other non-reciprocal effects such as temporal modulation. We demonstrate a non-reciprocal modulator comprising a pair of microring modulators and a microring phase shifter in an active silicon photonic process which, in combination with standard frequency filters, facilitates isolation. Isolation up to 13 dB is measured with a 3 dB bandwidth of 2 GHz and insertion loss of 18 dB. As one potential application is cross-talk suppression in bi-directional communication links, we also show transmission of a 4 Gbps data signal through the isolator while retaining a wide-open eye diagram. This compact design, in combination with increased modulation efficiency, could enable modulator-based isolators to become a standard `black-box component in integrated photonics foundry platform component library.
Graphene is a 2D material with appealing electronic and optoelectronic properties. It is a zero-bandgap material with valence and conduction bands meeting in a single point (Dirac point) in the momentum space. Its conductivity can be changed by shifting the Fermi level energy via an external electric field. This important property determines broadband and tunable absorption at optical frequencies. Moreover, its conductivity is a complex quantity, i.e. Graphene exhibits both electro-absorption and electro-refraction tunability, and this is an intriguing property for photonic applications. For example, it can be combined as an active material for silicon waveguides to realize efficient detectors, switches and modulators. In this paper, we review our results in the field, focusing on graphene-based optical modulators integrated on Silicon photonic platforms. Results obtained in the fabrication of single- and double-layer capacitive modulators are reported showing intensity and phase modulation, resilience of the generated signals to chromatic dispersion because of proper signal chirp and operation up to 50 Gb/s.
We introduce phase-change material Ge2Sb2Te5 (GST) into metal-insulator-metal (MIM) waveguide systems to realize chipscale plasmonic modulators and switches in the telecommunication band. Benefitting from the high contrast of optical properties between amorphous and crystalline GST, the three proposed structures can act as reconfigurable and non-volatile modulators and switches with excellent modulation depth 14 dB and fast response time in nanosecond, meanwhile possessing small footprints, simple frameworks and easy fabrication. This work provides new solutions to design active devices in MIM waveguide systems, and can find potential applications in more compact all-optical circuits for information processing and storage.
We demonstrated a silicon integrated microring modulator working at the 2-um waveband with an L-shaped PN junction. 15-GHz 3-dB electro-optic bandwidth and <1 Vcm modulation efficiency for 45-Gbps NRZ-OOK signaling is achieved at 1960 nm.
We describe a resonantly enhanced Mach-Zehnder modulator (MZM) that can be operated over a wide temperature range of 55C without being actively biased, while providing a significant resonant enhancement of 6.8 at the nominal wavelength / temperature compared to a linear MZM driven with a distributed driver. More importantly, it enables a ~20X improvement in power consumption compared to a 50 {Omega} matched linear traveling wave modulator with comparable phase shifter technology, drive voltage and output optical modulation amplitude. Passive biasing of the Mach-Zehnder interferometer is further implemented by replacing a splitter element in the MZM with a novel device combining splitting and fiber coupling functionalities in a single, multi-modal structure, that converts permanent fiber placement into a phase correction. Both concepts are combined in a single modulator device, removing the need for any type of active control in a wide temperature operation range.
Reliable operation of photonic integrated circuits at cryogenic temperatures would enable new capabilities for emerging computing platforms, such as quantum technologies and low-power cryogenic computing. The silicon-on-insulator platform is a highly promising approach to developing large-scale photonic integrated circuits due to its exceptional manufacturability, CMOS compatibility and high component density. Fast, efficient and low-loss modulation at cryogenic temperatures in silicon, however, remains an outstanding challenge, particularly without the addition of exotic nonlinear optical materials. In this paper, we demonstrate DC-Kerr-effect-based modulation at a temperature of 5 K at GHz speeds, in a silicon photonic device fabricated exclusively within a CMOS process. This work opens up the path for the integration of DC Kerr modulators in large-scale photonic integrated circuits for emerging cryogenic classical and quantum computing applications.