Toolkit for photonic integrated circuits based on inverted rib waveguides

This work was supported by an EPSRC Doctoral Prize and a European Research Council Starting under Grant 337508.We have performed an exploration of inverted rib waveguide platform for use in optical backplanes. This entailed the design, optimization, and characterization of a variety of passive optical components that may serve as a basis for the functions required of an on-chip optical networks. The presented design introduces an inverted-rib template, which consists of a polymer waveguide layer. We have successfully fabricated and demonstrated low-loss waveguides, and also functional passive devices such as directional couplers, multimode interferometers, waveguide bends and crossings, and distributed Bragg reflectors. We also demonstrate a way of coupling active components (e.g., in silicon) to such a photonic integrated circuit.PostprintPeer reviewe

Hybrid external cavity laser with an amorphous silicon-based photonic crystal cavity mirror

Funding: EU ERC-SG 337508 DANCER, EU H2020 Marie Skłodowska-Curie 713654 and SFI 18/TIDA/6128.The authors present results on the performance of a hybrid external cavity photonic crystal laser-comprising semiconductor optical amplifier, and a 2D photonic crystal cavity fabricated in low-temperature amorphous silicon. The authors demonstrate that lithographic control over amorphous silicon photonic crystal cavity-resonant wavelengths is possible, and that single-mode lasing at optical telecommunications wavelengths is possible on an amorphous silicon platform.Publisher PDFPeer reviewe

Wavelength-controlled external-cavity laser with a silicon photonic crystal resonant reflector

This work was partially funded by the EPSRC, Scottish Enterprise, and the European Research Council under the Starting Grant 337508.We report the experimental demonstration of an alternative design of external-cavity hybrid lasers consisting of a III-V Semiconductor Optical Amplifier with fiber reflector and a Photonic Crystal (PhC) based resonant reflector on SOI. The Silicon reflector comprises a polymer (SU8) bus waveguide vertically coupled to a PhC cavity and provides a wavelength-selective optical feedback to the laser cavity. This device exhibits milliwatt-level output power and sidemode suppression ratio of more than 25 dB.Publisher PD

Tunable optical buffer through an analogue to electromagnetically induced transparency in coupled photonic crystal cavities

We acknowledge funding from the European Research Council (ERC) under the European Union’s Seventh Framework Programme (FP7/2007- 2013) / ERC grant agreement n337508.Tunable on-chip optical delay has long been a key target for the research community, as it is the enabling technology behind delay lines, signal retiming and other applications vital to optical signal processing. To date, the field has been limited by high optical losses associated with slow light or delay structures. Here, we present a novel tunable delay line, based on a coupled cavity system exhibiting an electromagnetically induced transparency-like transmission spectrum, with record low loss, around 15 dB/ns. By tuning a single cavity, the delay of the complete structure can be tuned over 120 ps, with the maximum delay approaching 300 ps.PostprintPeer reviewe

Hybrid photonic crystal lasers

Energy efficient Wavelength Division Multiplexing (WDM) is the key to satisfying the future bandwidth requirements of datacentres. As the silicon photonics platform is regarded the only technology able to meet the required power and cost efficiency levels, the development of silicon photonics compatible narrow linewidth lasers is now crucial. We discuss the requirements for such laser systems and report the experimental demonstration of a compact uncooled external-cavity mW-class laser architecture with a tunable Si Photonic Crystal resonant reflector, suitable for direct Frequency Modulation.Postprin

Transfer printing for heterogeneous silicon PICs

Photonic integrated circuits (PICs), implementing optical functions such as light generation, modulation, routing and detection on a single chip, are emerging as a powerful platform to realize miniaturized optical systems. These chips find applications in various fields, ranging from high-speed optical transceivers to disposable biosensors, LiDARs for detection and ranging, spectroscopic analytical sensors, etc. Silicon photonics is the field that is using silicon fabrication technologies, developed over the last decades for advanced electronic integrated circuits, to realize PI Cs. Using this approach advanced PICs can be realized on 200 mm or 300 mm wafers in high volume and at low cost. On the silicon photonics platform many device structures are readily available: Si or SiN waveguides, micro-heaters for tuning/switching, Si or Ge based modulators and photodetectors. However, other optical functions such as light generation require the integration of III-V semiconductors on the silicon wafers. This can be realized using different approaches ranging from hybrid assembly over die-towafer bonding to monolithic integration. Every approach has its advantages and disadvantages. An interesting approach that we are developing is the use of microtransfer- printing technology for the integration of III-V semiconductor devices on a silicon photonic wafer, which is a scalable and minimally-invasive approach

Wavelength stability in a hybrid photonic crystal laser through controlled nonlinear absorptive heating in the reflector

The need for miniaturized, fully integrated semiconductor lasers has stimulated significant research efforts into realizing unconventional configurations that can meet the performance requirements of a large spectrum of applications, ranging from communication systems to sensing. We demonstrate a hybrid, silicon photonics-compatible photonic crystal (PhC) laser architecture that can be used to implement cost-effective, high-capacity light sources, with high side-mode suppression ratio and milliwatt output output powers. The emitted wavelength is set and controlled by a silicon PhC cavity-based reflective filter with the gain provided by a III–V-based reflective semiconductor optical amplifier (RSOA). The high power density in the laser cavity results in a significant enhancement of the nonlinear absorption in silicon in the high Q-factor PhC resonator. The heat generated in this manner creates a tuning effect in the wavelength-selective element, which can be used to offset external temperature fluctuations without the use of active cooling. Our approach is fully compatible with existing fabrication and integration technologies, providing a practical route to integrated lasing in wavelength-sensitive schemes

Frequency modulated external cavity laser with photonic crystal resonator and microheater

We demonstrate frequency modulation (FM) in an external cavity III-V/Silicon laser, comprising a Reflective Semiconductor Optical Amplifier (RSOA) and an SU8 polymer waveguide vertically coupled to a 2D Silicon Photonic Crystal (PhC) cavity. Laser FM was achieved by local heating of the PhC using a resistive element of Ni-Cr metal as a microheater to change the refractive index in the cavity hence changing the lasing frequency. Presented is a thermal study of the laser dynamics and observations of the shift in lasing frequency

Wavelength stability in a hybrid photonic crystal laser through controlled nonlinear absorptive heating in the reflector

This work was supported by the Science Foundation Ireland under Grants SFI12/RC/2276 and 16/ERCS/3838, Engineering and Physical Sciences Research Council (EPSRC) (doctoral grant EP/L505079/1 and equipment grant EP/L017008/1); European Research Council (ERC) (Starting Grant 337508); and Scottish Enterprise.The need for miniaturized, fully integrated semiconductor lasers has stimulated significant research efforts into realizing unconventional configurations that can meet the performance requirements of a large spectrum of applications, ranging from communication systems to sensing. We demonstrate a hybrid, silicon  photonics-compatible photonic crystal (PhC) laser architecture that can be used to implement cost-effective, high-capacity light sources, with high side-mode suppression ratio and milliwatt output output powers. The emitted wavelength is set and controlled by a silicon PhC cavity-based reflective filter with the gain provided by a III–V-based reflective semiconductor optical amplifier (RSOA). The high power density in the laser cavity results in a significant enhancement of the nonlinear absorption in silicon in the high Q-factor PhC resonator. The heat generated in this manner creates a tuning effect in the wavelength-selective element, which can be used to offset external temperature fluctuations without the use of active cooling. Our approach is fully compatible with existing fabrication and integration technologies, providing a practical route to integrated lasing in wavelength-sensitive schemes.Publisher PDFPeer reviewe

Heterogeneous integration in silicon photonics through micro-transfer-printing

Micro-transfer-printing enables the intimate integration of a wide range of opto-electronic micro-components on a silicon photonics platform. This technique allows for wafer-scale integration in a massively parallel manner with high alignment accuracy, high throughput and high yield, therefore leading to a cost reduction of complex photonic integrated circuits