High-speed plasmonic modulator in a single metal layer Ayata, Masafumi; Fedoryshyn, Yuriy; Heni, Wolfgang ...
Science (American Association for the Advancement of Science),
11/2017, Letnik:
358, Številka:
6363
Journal Article
Recenzirano
Odprti dostop
Plasmonics provides a possible route to overcome both the speed limitations of electronics and the critical dimensions of photonics. We present an all-plasmonic 116–gigabits per second ...electro-optical modulator in which all the elements—the vertical grating couplers, splitters, polarization rotators, and active section with phase shifters—are included in a single metal layer. The device can be realized on any smooth substrate surface and operates with low energy consumption. Our results show that plasmonics is indeed a viable path to an ultracompact, highest-speed, and low-cost technology that might find many applications in a wide range of fields of sensing and communications because it is compatible with and can be placed on a wide variety of materials.
Electro-optic modulators are essential for sensing, metrology and telecommunications. Most target fiber applications. Instead, metasurface-based architectures that modulate free-space light at ...gigahertz (GHz) speeds can boost flat optics technology by microwave electronics for active optics, diffractive computing or optoelectronic control. Current realizations are bulky or have low modulation efficiencies. Here, we demonstrate a hybrid silicon-organic metasurface platform that leverages Mie resonances for efficient electro-optic modulation at GHz speeds. We exploit quasi bound states in the continuum (BIC) that provide narrow linewidth (Q = 550 at Formula: see text nm), light confinement to the non-linear material, tunability by design and voltage and GHz-speed electrodes. Key to the achieved modulation of Formula: see text are molecules with r
= 100 pm/V and optical field optimization for low-loss. We demonstrate DC tuning of the resonant frequency of quasi-BIC by Formula: see text 11 nm, surpassing its linewidth, and modulation up to 5 GHz (f
= 3 GHz). Guided mode resonances tune by Formula: see text 20 nm. Our hybrid platform may incorporate free-space nanostructures of any geometry or material, by application of the active layer post-fabrication.
For nearly two decades, researchers in the field of plasmonics
-which studies the coupling of electromagnetic waves to the motion of free electrons near the surface of a metal
-have sought to realize ...subwavelength optical devices for information technology
, sensing
, nonlinear optics
, optical nanotweezers
and biomedical applications
. However, the electron motion generates heat through ohmic losses. Although this heat is desirable for some applications such as photo-thermal therapy, it is a disadvantage in plasmonic devices for sensing and information technology
and has led to a widespread view that plasmonics is too lossy to be practical. Here we demonstrate that the ohmic losses can be bypassed by using 'resonant switching'. In the proposed approach, light is coupled to the lossy surface plasmon polaritons only in the device's off state (in resonance) in which attenuation is desired, to ensure large extinction ratios between the on and off states and allow subpicosecond switching. In the on state (out of resonance), destructive interference prevents the light from coupling to the lossy plasmonic section of a device. To validate the approach, we fabricated a plasmonic electro-optic ring modulator. The experiments confirm that low on-chip optical losses, operation at over 100 gigahertz, good energy efficiency, low thermal drift and a compact footprint can be combined in a single device. Our result illustrates that plasmonics has the potential to enable fast, compact on-chip sensing and communications technologies.
The development of organic electro-optic (EO) materials that concurrently possess a high electro-optic coefficient (r 33), high index of refraction, and long-term or high-temperature stability of ...chromophore alignment has been a crucial goal. To address this challenge, we developed a crosslinkable EO system consisting of two chromophores, HLD1 and HLD2, which can be electric field poled and then thermally crosslinked in situ to form a stable EO material. This approach avoids the necessity for nonlinear optically inactive materials such as polymers or small molecule cross-linkers, thus resulting in high chromophore density (>5 × 1020 molecules/cm3) and high index of refraction (n = 1.89 at 1310 nm) for HLD1/HLD2. Different ratios of HLD1 and HLD2 were evaluated to optimize poling efficiency and thermal stability of the poling-induced order. With 2:1 HLD1/HLD2 (wt/wt), a maximum r 33 of 290 ± 30 pm/V was achieved in a cross-linked film. Thermal stability tests showed that after heating to 85 °C for 500 h, greater than 99% of the initial r 33 value was maintained. This combination of large EO activity, high index of refraction, and long-term alignment stability is an important breakthrough in EO materials. HLD1/HLD2 can also be poled without the subsequent cross-linking step, and even larger maximum r 33 (460 ± 30 pm/V) and n 3 r 33 figure of merit (3100 ± 200 pm/V) were achieved. Hyperpolarizabilities of HLD and control molecules were analyzed by hyper-Rayleigh scattering and computational modeling with good agreement, and they help explain the high acentric order achieved during poling.
Coherent optical communications provides the largest data transmission capacity with the highest spectral efficiency and therefore has a remarkable potential to satisfy today's ever-growing bandwidth ...demands. It relies on so-called in-phase/quadrature (IQ) electro-optic modulators that encode information on both the amplitude and the phase of light. Ideally, such IQ modulators should offer energy-efficient operation and a most compact footprint, which would allow high-density integration and high spatial parallelism. Here, we present compact IQ modulators with an active section occupying a footprint of 4 × 25 µm × 3 µm, fabricated on the silicon platform and operated with sub-1-V driving electronics. The devices exhibit low electrical energy consumptions of only 0.07 fJ bit
at 50 Gbit s
, 0.3 fJ bit
at 200 Gbit s
, and 2 fJ bit
at 400 Gbit s
. Such IQ modulators may pave the way for application of IQ modulators in long-haul and short-haul communications alike.
Terahertz sources and detectors have enabled numerous new applications from medical to communications. Yet, most efficient terahertz detection schemes rely on complex free-space optics and typically ...require high-power lasers as local oscillators. Here, we demonstrate a fiber-coupled, monolithic plasmonic terahertz field detector on a silicon-photonics platform featuring a detection bandwidth of 2.5 THz with a 65 dB dynamical range. The terahertz wave is measured through its nonlinear mixing with an optical probe pulse with an average power of only 63 nW. The high efficiency of the scheme relies on the extreme confinement of the terahertz field to a small volume of 10
(λ
/2)
. Additionally, on-chip guided plasmonic probe beams sample the terahertz signal efficiently in this volume. The approach results in an extremely short interaction length of only 5 μm, which eliminates the need for phase matching and shows the highest conversion efficiency per unit length up to date.
Abstract
Tailored nanostructures provide at-will control over the properties of light, with applications in imaging and spectroscopy. Active photonics can further open new avenues in remote ...monitoring, virtual or augmented reality and time-resolved sensing. Nanomaterials with
χ
(2)
nonlinearities achieve highest switching speeds. Current demonstrations typically require a trade-off: they either rely on traditional
χ
(2)
materials, which have low non-linearities, or on application-specific quantum well heterostructures that exhibit a high
χ
(2)
in a narrow band. Here, we show that a thin film of organic electro-optic molecules JRD1 in polymethylmethacrylate combines desired merits for active free-space optics: broadband record-high nonlinearity (10-100 times higher than traditional materials at wavelengths 1100-1600 nm), a custom-tailored nonlinear tensor at the nanoscale, and engineered optical and electronic responses. We demonstrate a tuning of optical resonances by Δ
λ
= 11 nm at DC voltages and a modulation of the transmitted intensity up to 40%, at speeds up to 50 MHz. We realize 2 × 2 single- and 1 × 5 multi-color spatial light modulators. We demonstrate their potential for imaging and remote sensing. The compatibility with compact laser diodes, the achieved millimeter size and the low power consumption are further key features for laser ranging or reconfigurable optics.
The performance of highly nonlinear organic electro-optic (EO) materials incorporated into nanoscale slots is examined. It is shown that EO coefficients as large as 190 pm/V can be obtained in 150 nm ...wide plasmonic slot waveguides but that the coefficients decrease for narrower slots. Possible mechanism that lead to such a decrease are discussed. Monte-Carlo computer simulations are performed, confirming that chromophore-surface interactions are one important factor influencing the EO coefficient in narrow plasmonic slots. These highly nonlinear materials are of particular interest for applications in optical modulators. However, in modulators the key parameters are the voltage-length product U
L and the insertion loss rather than the linear EO coefficients. We show record-low voltage-length products of 70 Vµm and 50 Vµm for slot widths in the order of 50 nm for the materials JRD1 and DLD164, respectively. This is because the nonlinear interaction is enhanced in narrow slot and thereby compensates for the reduced EO coefficient. Likewise, it is found that lowest insertion losses are observed for slot widths in the range 60 to 100 nm.
The performance of electro-optic devices based on organic second order NLO materials has been improved by orders of magnitude through theory-guided improvement in the electro-optic activity and other ...relevant properties of organic materials and by field compression of radio frequency (RF) and optical fields associated with the transition from microscale/mesoscale devices to silicon–organic hybrid (SOH) and plasmonic–organic hybrid (POH) devices with nanoscopic dimensions. This paradigm shift in organic electro-optic R&D has led to many performance improvements, including record performance for voltage-length performance of less than 50 V-μm, energy consumption of less than 70 attojoules/bit, bandwidths of greater than 500 gigahertz (GHz), and device footprints of less than 20 μm2. Another consequence of improving electro-optic performance is the corresponding improvement of the converse second order nonlinear optical property of optical rectification (transparent photodetection). Theory has permitted identification of optimum optical nonlinearity/transparency values and dipole moments for newly developed chromophores, which have led, in turn, to state-of-the-art materials and device performance.
PDF
