We present a micrometer scale, on-chip integrated, plasmonic enhanced graphene photodetector (GPD) for telecom wavelengths operating at zero dark current. The GPD is designed and optimized to directly generate a photovoltage and has an external responsivity∼12.2V/W with a 3dB bandwidth∼42GHz. We utilize Au split-gates with a∼100nm gap to electrostatically create a p-n-junction and simultaneously guide a surface plasmon polariton gap-mode. This increases light-graphene interaction and optical absorption and results in an increased electronic temperature and steeper temperature gradient across the GPD channel. This paves the way to compact, on-chip integrated, power-efficient graphene based photodetectors for receivers in tele and datacom modules.The ever-growing demand for global data traffic[1] is driving the development of next generation communication standards [2,3]. The increasing numbers of connected devices[4], the need for new functionalities, and the development of high-performance computing [5,6] require optical communication systems performing at higher speeds, with improved energy-efficiency, whilst maintaining scalability and cost-effective manufacturing. Si photonics[7-9] offers the prospect of dense (nanoscale) integration[10] relying on mature, low-cost (based on complementary metal-oxide-semiconductor (CMOS) fabrication processes) manufacturing [8,9], making it one of the key technologies for short-reach (<10km) optical interconnects[11] beyond currently employed lithium niobate[12] and indium phosphate[13]. A variety of functionalities have been developed and demonstrated in Si photonics for local optical interconnects[11]. Electro-optic modulators based on carrier-depletion (phase-modulation) in Si[14, 15] or the Franz-Keldysh effect[16] (amplitude-modulation) in strained Si-Ge[17, 18] encode information into optical signals at telecom wavelengths (λ =1.3-1.6µm). On the receiver side, Ge[19] or bonded III-V[20, 21] photodetectors (PD) are needed for optical-to-electrical signal conversion, since the telecom photon energies are not sufficient for direct (band-to-band) photodetection in Si[22].On-chip integrated Ge PDs [23][24][25][26][27] are standard components in Si photonics foundries [8,9,22]. Their external responsivities (in A/W), R I = I ph /P in , where I ph is the photocurrent and P in is the incident optical power, can exceed 1A/W [8,23] and their bandwidth can reach 60GHz [25][26][27]. Following the development of high temperature (> 600 • C) [19] heterogeneous integration of Ge-on-Si using epitaxial growth and cyclic thermal annealing [19,28,29], the concentration of defects and threading dislocations in Ge epilayers and at Si/Ge interfaces can be reduced [19], resulting in low (<10nA[9, 27]) dark current in waveguide integrated Ge p-i-n photodiodes [24,27]. However, Ge-on-Si integration is a complex process [19,22,29], as the lattice mismatch between Si and Ge [19], ion implantation [23,25], thermal budget (i.e. thermal energy transfer to the wafer) management [22], and the non-plan...

There is a rapidly growing demand to use silicon and silicon nitride (Si 3 N 4 ) integrated photonics for sensing applications, ranging from refractive index to spectroscopic sensing. By making use of advanced CMOS technology, complex miniaturized circuits can be easily realized on a large scale and at a low cost covering visible to mid-IR wavelengths. In this paper we present our recent work on the development of silicon and Si 3 N 4 -based photonic integrated circuits for various spectroscopic sensing applications. We report our findings on waveguide-based absorption, and Raman and surface enhanced Raman spectroscopy. Finally we report on-chip spectrometers and on-chip broadband light sources covering very near-IR to mid-IR wavelengths to realize fully integrated spectroscopic systems on a chip.

We present a silicon implementation of a 4-port universal linear optical circuit. Instead of predefining the exact functionality of a photonic circuit at design time, we demonstrate a simple generic silicon photonic circuit, combined with electronic control and software feedback, that can perform any linear operation between its 4 input and output ports. The circuit consists of a network of thermally tunable symmetric Mach-Zehnder interferometers with phase and amplitude control, in-circuit optical power monitors, and local software controlled feedback loops. The circuit can be configured using a training mechanism, which makes it to self-adapt to implement the desired function. We use the circuit to demonstrate an adaptive, universal beam coupler, as well as a switch matrix.

Efficient complementary metal-oxide semiconductor-based nonlinear optical devices in the near-infrared are in strong demand. Due to two-photon absorption in silicon, however, much nonlinear research is shifting towards unconventional photonics platforms. In this work, we demonstrate the generation of an octave-spanning coherent supercontinuum in a silicon waveguide covering the spectral region from the near- to shortwave-infrared. With input pulses of 18 pJ in energy, the generated signal spans the wavelength range from the edge of the silicon transmission window, approximately 1.06 to beyond 2.4 μm, with a −20 dB bandwidth covering 1.124–2.4 μm. An octave-spanning supercontinuum was also observed at the energy levels as low as 4 pJ (−35 dB bandwidth). We also measured the coherence over an octave, obtaining , in good agreement with the simulations. In addition, we demonstrate optimization of the third-order dispersion of the waveguide to strengthen the dispersive wave and discuss the advantage of having a soliton at the long wavelength edge of an octave-spanning signal for nonlinear applications. This research paves the way for applications, such as chip-scale precision spectroscopy, optical coherence tomography, optical frequency metrology, frequency synthesis and wide-band wavelength division multiplexing in the telecom window.

Graphene integrated photonics provides several advantages over conventional Si photonics. Single layer graphene (SLG) enables fast, broadband, and energy-efficient electro-optic modulators, optical switches and photodetectors (GPDs), and is compatible with any optical waveguide. The last major barrier to SLG-based optical receivers lies in the current GPDs’ low responsivity when compared to conventional PDs. Here we overcome this by integrating a photo-thermoelectric GPD with a Si microring resonator. Under critical coupling, we achieve >90% light absorption in a ~6 μm SLG channel along a Si waveguide. Cavity-enhanced light-matter interactions cause carriers in SLG to reach ~400 K for an input power ~0.6 mW, resulting in a voltage responsivity ~90 V/W, with a receiver sensitivity enabling our GPDs to operate at a 10−9 bit-error rate, on par with mature semiconductor technology, but with a natural generation of a voltage, rather than a current, thus removing the need for transimpedance amplification, with a reduction of energy-per-bit, cost, and foot-print.

A tunable laser source is a crucial photonic component for many applications, such as spectroscopic measurements, wavelength division multiplexing (WDM), frequency-modulated light detection and ranging (LIDAR), and optical coherence tomography (OCT). In this article, we demonstrate the first monolithically integrated erbium-doped tunable laser on a complementary-metal-oxide-semiconductor (CMOS)-compatible silicon photonics platform. Erbium-doped AlO sputtered on top is used as a gain medium to achieve lasing. The laser achieves a tunability from 1527 nm to 1573 nm, with a >40 dB side mode suppression ratio (SMSR). The wide tuning range (46 nm) is realized with a Vernier cavity, formed by two SiN microring resonators. With 107 mW on-chip 980 nm pump power, up to 1.6 mW output lasing power is obtained with a 2.2% slope efficiency. The maximum output power is limited by pump power. Fine tuning of the laser wavelength is demonstrated by using the gain cavity phase shifter. Signal response times are measured to be around 200 μs and 35 µs for the heaters used to tune the Vernier rings and gain cavity longitudinal mode, respectively. The linewidth of the laser is 340 kHz, measured via a self-delay heterodyne detection method. Furthermore, the laser signal is stabilized by continuous locking to a mode-locked laser (MLL) over 4900 seconds with a measured peak-to-peak frequency deviation below 10 Hz.

We demonstrate a phase shifter using a silicon slot waveguide infiltrated with liquid crystal. For a 1 mm long device we achieve 73π phase shift with a 5 V voltage, with a voltagelength product of 0.0224 V·mm around 1 V. We drive the phase shifter with a digital 1 V, duobinary pulse-width-modulated signal, or a 1 V frequency-modulated signal. This enables direct digital CMOS control of an analog optical phase shifter.

Mid-infrared laser sources are of great interest for various applications, including light detection and ranging, spectroscopy, communication, trace-gas detection, and medical sensing. Silicon photonics is a promising platform that enables these applications to be integrated on a single chip with low cost and compact size. Silicon-based high-power lasers have been demonstrated at 1.55 μm wavelength, while in the 2 μm region, to the best of our knowledge, high-power, high-efficiency, and monolithic light sources have been minimally investigated. In this Letter, we report on high-power CMOS-compatible thulium-doped distributed feedback and distributed Bragg reflector lasers with single-mode output powers up to 267 and 387 mW, and slope efficiencies of 14% and 23%, respectively. More than 70 dB side-mode suppression ratio is achieved for both lasers. This work extends the applicability of silicon photonic microsystems in the 2 μm region.