Silicon Phase Modulators Research Articles

Graphene-Based Silicon Photonic Electro-Absorption Modulators and Phase Modulators

Graphene-Based Silicon Photonic Electro-Absorption Modulators and Phase Modulators

Silicon Photonics Multi-Function Integrated Optical Circuit for Miniaturized Fiber Optic Gyroscope

Interferometric fiber optic gyroscope (IFOG) is advantageous for inertial navigation due to its high reliability as a solid-state technology with no moving parts. The size, weight, power, and cost of IFOG can be improved by employing photonic integration technology. Here, by leveraging the foundry-enabled silicon photonics platform, we demonstrate a silicon multi-function integrated optical circuit (Si-MIOC) with a fingertip size that can easily interfaces with light source and fiber coil to perform a tactical-grade gyroscope (0.1 °/hr bias instability). This achievement comes from the pros of high-index-contrast silicon waveguide that enables high polarization extinction ratio of > 60 dB and high electro-optic efficiency in silicon phase modulator, while the cons of the signature lead to non-negligible optical back-reflection at silicon/fiber interfaces and generate spurious bias voltage offset at the gyroscope outputs. Nevertheless, the results of earth rotation measurement and Allan deviation analysis confirmed that Si-MIOC based IFOG is a promising angular sensor and can be utilized to construct a compact and low-cost inertial measurement unit.

Development of thin film quarter-waveplate for polarization-independent liquid crystal on silicon phase modulators

Liquid crystal on silicon (LCoS) phase modulators spatially modulate the phase of light across the panel. The orientation order and elongated molecules of nematic liquid crystals (LCs) means that traditional LCoS phase modulators are inherently polarization-dependent, resulting in either complicated polarization manipulation systems or high optical power loss for unpolarized incident light. We propose a polarization-independent LCoS (PI-LCoS) device that combines existing technologies, which allows for cost-effective fabrication. Our PI-LCoS phase modulator is suitable for a wide variety of applications in telecommunication, adaptive optics, and display technologies. We have demonstrated the feasibility of the proposed PI-LCoS device by fabricating polarization-independent LC cells using a thin-film quarter-wave plate composed of a photoalignment layer and a layer of LC polymer. We show experimentally that the proposed design can efficiently modulate the phase of light with arbitrary input polarization.

Chip-based microwave photonic frequency mixer (Invited)

A microwave photonic frequency mixer constituted of an optically-carried local oscillator (LO) and a wavelength-division modulator was proposed. The wavelength-division modulator chip, which was consisted of a silicon phase modulator, two micro-ring filters, a photodetector, two optical couplers, and two grating couplers, was designed and fabricated. Based on the chip, a microwave photonic harmonic frequency mixer was implemented. In the experiment, an optically-carried LO was generated by double-sideband suppressed-carrier modulation at a Mach-Zehnder modulator. An RF signal from 6 to 16 GHz was successfully converted into a signal with a frequency of 33 to 23 GHz. In order to suppress the remaining mixing spurs, two solutions, i.e., increasing the rejection ratio of the micro-ring filter to decrease the intensity of the leaked optically-carried LO and introducing an optical phase shifter to correct the phase of the leaked optically-carried LO, were proposed and verified by simulation. It should be noted that the latter is simpler and more suitable for photonic integration.

Fast beam steering enabled by a chip-scale optical phased array with 8 × 8 elements

We present a two-dimensional (2D) optical phased array (OPA) with 8 × 8 elements in which light is electro-optically controlled by silicon phase modulators. The randomly distributed initial phases are calibrated through an interference technique to achieve a beam divergence of 0.92∘×0.32∘ and a scanning range of 8.9∘×2.2∘. A bandwidth of 324 MHz and beam steering at a point-to-point speed of 20 MHz was realized on the fabricated chip. Systematic analysis revealed that the 2D electro-optical OPA is promising and feasible for many applications ranging from optical communication to light detection and ranging (LiDAR).

Characterization of the spatially anamorphic phenomenon and temporal fluctuations in high-speed, ultra-high pixels-per-inch liquid crystal on silicon phase modulator.

High-birefringence liquid crystal (LC) in ultrathin LCOS panels was adopted to prepare high phase precision (mSTD =λ/50) and phase accuracy (mAPAE% ∼8%) with suppressed pixel-level crosstalk effects. In conjunction with optimized digital driving scheme, the zero order light loss was found directly related to the phase accuracy error. Meanwhile, the world's fastest pure phase modulation LCOS with a response time of ∼0.87 ms at 45 °C was also achieved. The low-temporal flicker (P-P ∼2.0%) with high-speed LC responses was demonstrated by applying new digital driving scheme. Finally, the 4K2 K LCOS-SLM (∼7000 PPI) was evaluated its difficulties and opportunities.

Graphene–silicon phase modulators with gigahertz bandwidth

We demonstrate a 10Gb/s Graphene Phase Modulator (GPM) integrated in a Mach-Zehnder interferometer configuration. This is a compact device, with a phase-shifter length of only 300$\mu$m, and 35dB extinction ratio. The GPM has modulation efficiency of 0.28Vcm, one order of magnitude higher compared to state-of-the-art depletion p-n junction Si phase modulators. Our GPM operates with 2V peak-to-peak driving voltage in a push-pull configuration, and it has been tested in a binary transmission of a non-return-to-zero data stream over 50km single mode fibre. This device is the key building block for graphene-based integrated photonics, enabling compact and energy efficient hybrid Si-graphene modulators for telecom, datacom and other applications

Simplified modeling and optimization of silicon modulators based on free-carrier plasma dispersion effect.

In this paper, a simplified model of silicon phase modulators is presented that enables favorable accuracy together with a substantial reduction in computational effort and without the requirement of semiconductor TCAD device simulation software. This permits fast optimization of the different parameters of a modulator. The model was successfully implemented in Phoenix Optodesigner optical software allowing the optimization of silicon phase shifters for different applications. Moreover, this model presents a great potential for the simulation of modulators based on PN interdigitated junctions, which normally require complex and time consuming 3D simulations. Simulation time was reduced by a factor of 6 for the lateral PN junction based modulator, and two orders of magnitude reduction was obtained for interdigitated PN junctions based modulators.

Holography using pixelated spatial light modulators—Part 2: applications

Dynamic holography can replace or enhance traditional basic optical functionalities within a lot of different optical systems. In particular, the possibility of considerably changing the function of a system is an important strength that is rarely possible in conventional optical systems. Today, different spatial light modulators can be employed in order to achieve dynamic holography, but most often liquid crystal on silicon phase modulators are used. We give an overview of applications for the usage of pixelated spatial light modulators in dynamic holography based on the functionalities that the dynamic holograms fulfill.

Dynamic Characterization of Distortion in Hybrid Silicon Evanescent Phase Modulators

We report the dynamic distortion of hybrid silicon phase modulators for three types of active layers. The third-order intermodulation distortion for each modulator was measured under various bias conditions by means of a two-tone technique. A peak phase input intercept point of 2.6pi for doped quantum-well modulators was achieved at a reverse bias of 4 V and a signal frequency of around 500 MHz.

High efficient silicon phase modulator based on n-p-n configuration

A Mach-Zehnder modulator based on n-p-n electronic configuration and a single mode waveguide is proposed and analysed. The excellent optical confinement together with the reversed biased operation enables high efficiency and fast modulation. An optimum overlap between the optical field and the depletion regions warrants a VπLπ merit of 0.87 V · cm. The rise and fall times are 0.063 and 0.006 ns, respectively, when conventional electrodes are utilised.

Direct measurement of the refractive index change of silicon with optically injected carriers

Silicon phase modulators are important silicon optoelectronic devices. The relationship of the refractive index change with injected carrier concentration is the basis for the operation of silicon phase modulators. No direct experimental data of this relationship have been reported. We have developed a new method for the direct measurement of this relationship using a Fabry–Perot interference and optical injection of carriers. The experimental results of the refractive index change are reported for the first time in the range of injected carrier concentration between 1013 and 1015 cm−3. It should be noted that our experiment results are about 5 to 10 times larger than those predicted by theory. The reliability of our experiments is also discussed.