Charalambos Klitis

Generation of photonic orbital angular momentum superposition states using vortex beam emitters with superimposed gratings

An integrated approach to produce orbital angular momentum (OAM) superposition states has been demonstrated. Superposition states between two vector OAM modes have been achieved by integrating a superimposed angular grating in one silicon micro-ring resonator.

Direct fiber vector eigenmode multiplexing transmission seeded by integrated optical vortex emitters

Spatial modes have received substantial attention over the last decades and are used in optical communication applications. In fiber-optic communications, the employed linearly polarized modes and phase vortex modes carrying orbital angular momentum can be synthesized by fiber vector eigenmodes. To improve the transmission capacity and miniaturize the communication system, straightforward fiber vector eigenmode multiplexing and generation of fiber-eigenmode-like polarization vortices (vector vortex modes) using photonic integrated devices are of substantial interest. Here, we propose and demonstrate direct fiber vector eigenmode multiplexing transmission seeded by integrated optical vortex emitters. By exploiting vector vortex modes (radially and azimuthally polarized beams) generated from silicon microring resonators etched with angular gratings, we report data-carrying fiber vector eigenmode multiplexing transmission through a 2-km large-core fiber, showing low-level mode crosstalk and favorable link performance. These demonstrations may open up added capacity scaling opportunities by directly accessing multiple vector eigenmodes in the fiber and provide compact solutions to replace bulky diffractive optical elements for generating various optical vector beams.

Performance evaluation of analog signal transmission in an integrated optical vortex emitter to 3.6-km few-mode fiber system.

We experimentally demonstrate and evaluate the performance of an analog signal transmission system with photonic integrated optical vortex emitter and 3.6-km few-mode fiber (FMF) link using orbital angular momentum (OAM) modes. The fabricated photonic integrated device is capable of emitting vector optical vortices carrying well-defined and quantized OAM modes with topological charge l=-2 and 2. After propagating through 3.6-km FMF, we measure and assess the spurious free dynamic range of the second-order harmonic distortion. Moreover, we study the impact of nonlinearity-induced resonance wavelength shift of the optical vortex emitter on the analog link performance as increasing the input optical power.

Wavelength Locking of Silicon Photonics Multiplexer for DML-Based WDM Transmitter

We present a wavelength locking platform enabling the feedback control of silicon (Si) microring resonators (MRRs) for the realization of a 4 × 10 Gb/s wavelength-division-multiplexing (WDM) transmitter. Four thermally tunable Si MRRs are employed to multiplex the signals generated by four directly modulated lasers (DMLs) operating in the L-band, as well as to improve the quality of the DMLs signals. Feedback control is achieved through a field-programmable gate array controller by monitoring the working point of each MRR through a transparent detector integrated inside the resonator. The feedback system provides an MRR wavelength stability of about 4 pm (0.5 GHz) with a time response of 60 ms. Bit error rate (BER) measurements confirm the effectiveness and the robustness of the locking system to counteract sensitivity degradations due to thermal drifts, even under uncooled operation conditions for the Si chip.

Wavelength locking platform for DML-based multichannel transmitter on a silicon chip

We present a platform for the feedback control of a multichannel transmitter based on DML sources and a silicon photonic multiplexer and carver circuit. Automatic tuning and wavelength locking are demonstrated in about 150 ms.

High accuracy transfer printing of single-mode membrane silicon photonic devices

A transfer printing (TP) method is presented for the micro-assembly of integrated photonic devices from suspended membrane components. Ultra thin membranes with thickness of 150nm are directly printed without the use of mechanical support and adhesion layers. By using a correlation alignment scheme vertical integration of single-mode silicon waveguides is achieved with an average placement accuracy of 100±70nm. Silicon (Si) μ-ring resonators are also fabricated and show controllable optical coupling by varying the lateral absolute position to an underlying Si bus waveguide.

Two-Layer Interconnection Network Architectures Based on Integrated Concentric Orbital Angular Momentum Emitters

Novel architectures for two-layer interconnection networks based on concentric OAM emitters are presented. A scalability analysis is done in terms of devices characteristics, power budget and OSNR by exploiting experimentally measured parameters.

Silicon photonic filters with high rejection of both TE and TM modes for on-chip four wave mixing applications

Wavelength selective filters represent one of the key elements for photonic integrated circuits (PIC) and many of their applications in linear and non-linear optics. In devices optimised for single polarisation operation, cross-polarisation scattering can significantly limit the achievable filter rejection. An on-chip filter consisting of elements to filter both TE and TM polarisations is demonstrated, based on a cascaded ring resonator geometry, which exhibits a high total optical rejection of over 60 dB. Monolithic integration of a cascaded ring filter with a four-wave mixing micro-ring device is also experimentally demonstrated with a FWM efficiency of -22dB and pump filter extinction of 62dB.

Demonstration of few mode fiber transmission link seeded by a silicon photonic integrated optical vortex emitter

We experimentally demonstrate a chip to few mode fiber (FMF) transmission link with on-off-keying (OOK) signal. The device emits TM01 and TE01 vortex modes which propagate through a 1.1 km FMF with measured OSNR penalties less than 2 dB at a BER of 2e-3.

Trimming of silicon-on-insuiator micro-ring resonators by laser irradiation

Silicon on Insulator (SOI) is a well-established photonic platform that is of interest to photonic integrated circuits (PICs) due to its compatibility with existing fabrication processes used in the manufacture of electronic integrated circuits. Although SOI offers a high refractive index contrast that enables strong optical confinement of the propagating optical mode in the silicon layer, the performance of the photonic circuit components (such as, for example, ring resonators) is significantly dependant on fabrication tolerance. This can result in ring resonances that substantially deviate from the designed ones. It is therefore advantageous to be able to trim or tune such components post-processing, so as to adjust a resonance to the desired wavelength.