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In this paper, we provide a review of recent progress in integrated nonlinear photonics with a focus on emerging applications in all-optical signal processing, ultra-low-power all-optical switching, and quantum information processing.
We present optically tunable operations of deoxyribonucleic acid (DNA) biopolymer devices, where a single high-resistance state, write-once read-many-times memory state, write-read-erase memory state, and single low-resistance state can be achieved by controlling UV irradiation time. The device is a simple sandwich structure with a spin-coated DNA biopolymer layer sandwiched by two electrodes. Upon irradiation, the electrical properties of the device are adjusted owing to a phototriggered synthesis of silver nanoparticles in DNA biopolymer, giving rise to multiple switching scenarios. This technique, distinct from the strategy of doping of pre-formed nanoparticles, enables a post-film fabrication process for achieving optically controlled memory device operations, which provides a more versatile platform to fabricate organic memory and optoelectronic devices.
Highlights: • Phosphate glass-clad Se{sub 0.5}Te{sub 0.5} semiconductor core optical fibers were fabricated. • Crystalline Se{sub 0.5}Te{sub 0.5} semiconductor core optical fibers were successfully obtained. • The fibers can detect light incident on it from at any point along its entire length. • The fibers can be used as stress sensing without the use of optical probing signals. - Abstract: Se{sub 0.5}Te{sub 0.5} semiconductor core optical fibers with phosphate glass cladding were fabricated by using a reactive molten core approach. The core was found to be amorphous with some oxygen diffusing in from the cladding glass. Crystalline Se{sub 0.5}Te{sub 0.5} (c-Se{sub 0.5}Te{sub 0.5}) semiconductor core fibers were obtained by a post-drawing annealing process. Significant disparities in conductivity under stress and without stress were observed in c-Se{sub 0.5}Te{sub 0.5} semiconductor core fibers. To the best of our knowledge, this is the first time that stress sensing can be realized in c-Se{sub 0.5}Te{sub 0.5} semiconductor core optical fibers. This is in contrast to all previous work on stress sensing using fibers, which require the use of optical probing signals. In addition, it is found that more than 60 times change in conductivity between dark and illuminated states in c-Se{sub 0.5}Te{sub 0.5} semiconductor core fibers. These results demonstrate that c-Se{sub 0.5}Te{sub 0.5} semiconductor core optical fibers have promising applications in stress sensor, photodetector, and optical switch.
A polarization-independent optical switch is disclosed for switching at least one incoming beam from at least one input source to at least one output drain. The switch includes a polarizing beam splitter to split each of the at least one incoming beam into a first input beam and a second input beam, wherein the first input beam and the second input beams are independently polarized; a wave plate optically coupled to the second input beam for converting the polarization of the second input beam to an appropriately polarized second input beam; a beam combiner optically coupled to the first input beam and the modified second input beam, wherein the beam combiner accepts the first input beam and the modified second input beam to produce a combined beam; the combined beam is invariant to the polarization state of the input source's polarization; and a controllable spatial light modulator optically coupled to the combined beam, wherein the combined beam is diffracted by the controllable spatial light modulator to place light at a plurality of output locations.
Synthetic ferrimagnets are composite magnetic structures formed from two or more anti-ferromagnetically coupled magnetic sublattices with different magnetic moments. Here, we report on atomistic spin simulations of the laser-induced magnetization dynamics on such synthetic ferrimagnets and demonstrate that the application of ultrashort laser pulses leads to sub-picosecond magnetization dynamics and all-optical switching in a similar manner as in ferrimagnetic alloys. Moreover, we present the essential material properties for successful laser-induced switching, demonstrating the feasibility of using a synthetic ferrimagnet as a high density magnetic storage element without the need of a write field.
Optical selection rules fundamentally determine the optical transitions between energy states in a variety of physical systems, from hydrogen atoms to bulk crystals such as gallium arsenide. These rules are important for optoelectronic applications such as lasers, energy-dispersive X-ray spectroscopy, and quantum computation. Recently, single-layer transition metal dichalcogenides have been found to exhibit valleys in momentum space with nontrivial Berry curvature and excitons with large binding energy. However, there has been little study of how the unique valley degree of freedom combined with the strong excitonic effect influences the nonlinear optical excitation. Here in this paper, we report the discovery of nonlinear optical selection rules in monolayer WS 2 , an important candidate for visible 2D optoelectronics because of its high quantum yield and large direct bandgap. We experimentally demonstrated this principle for second-harmonic generation and two-photon luminescence (TPL). Moreover, the circularly polarized TPL and the study of its dynamics evince a sub-ps interexciton relaxation (2p → 1s). The discovery of this new optical selection rule in a valleytronic 2D system not only considerably enhances knowledge in this area but also establishes a foundation for the control of optical transitions that will be crucial for valley optoelectronic device applications such as 2D valley-polarized THz sources with 2p-1s transitions, optical switches, and coherent control for quantum computing.
All-optical switches have been considered as a promising solution to overcome the fundamental speed limit of the current electronic switches. However, the lack of a suitable third-order nonlinear material greatly hinders the development of this technology. Here in this paper we report the observation of ultrahigh third-order nonlinearity about 0.45 cm 2 /GW in graphene oxide thin films at the telecommunication wavelength region, which is four orders of magnitude higher than that of single crystalline silicon. Besides, graphene oxide is water soluble and thus easy to process due to the existence of oxygen containing groups. These unique properties can potentially significantly advance the performance of alloptical switches.
Here, this Letter reports on a vertical, bulk-conducting photoconductive semiconductor switch (PCSS) fabricated on an intrinsic Type IIa single-crystal diamond substrate. Under near-bandgap excitation at 225 nm with a 20 μ J pulse, a strong photocurrent response of 17.1 A at 1 kV DC bias magnitude is obtained by (i) tuning the optical trigger wavelength to the “matched-absorption” window (224–235 nm) near the band edge, where the optical penetration depth becomes comparable to the 500 μ m substrate thickness, and (ii) choosing the bias polarity ensuring electron-dominant conduction, given that electrons have a higher mobility than holes in diamond. The PCSS has an area-normalized responsivity of 54.2 mA W −1 cm −2 and an effective on-resistance of 8.48 Ω, with a fast 90%–10% transient fall time of 25 ns, attributed to carrier sweep-out. These results support vertical, bulk-conducting intrinsic diamond PCSS as a promising platform for high-power optical switching and provide new insight into intrinsic photoconductivity in diamond.
The strong coherent coupling of quantum emitters to vacuum fluctuations of the light field offers opportunities for manipulating the optical and transport properties of nanomaterials, with potential applications ranging from ultrasensitive all-optical switching to creating polariton condensates. Often, ubiquitous decoherence processes at ambient conditions limit these couplings to such short time scales that the quantum dynamics of the interacting system remains elusive. Prominent examples are strongly coupled exciton-plasmon systems, which, so far, have mostly been investigated by linear optical spectroscopy. Here, we use ultrafast two-dimensional electronic spectroscopy to probe the quantum dynamics of J-aggregate excitons collectively coupled to the spatially structured plasmonic fields of a gold nanoslit array. We observe rich coherent Rabi oscillation dynamics reflecting a plasmon-driven coherent exciton population transfer over mesoscopic distances at room temperature. This opens up new opportunities to manipulate the coherent transport of matter excitations by coupling to vacuum fields.
Second-order optical effects are essential to the active control of light and the generation of new spectral components. The inversion symmetry, however, prevents achieving a bulk $χ^{(2)}$ response, limiting the portfolio of the second-order nonlinear materials. Here, we demonstrate subpicosecond conversion of a statically passive dielectric to a transient second-order nonlinear medium upon the ultrafast transfer of hot electrons. Induced by an optical switching signal, the amorphous dielectric with vanishing intrinsic $χ^{(2)}$ develops dynamically tunable second-order nonlinear responses. By taking the second-harmonic generation as an example, we show that breaking the inversion symmetry through hot-electron dynamics can be leveraged to address the critical need for all-optical control of second-order nonlinearities in nanophotonics. We report our approach can be generically adopted in a variety of material and device platforms, offering a new class of complex nonlinear media with promising potentials for all-optical information processing.
A fluid self-assembly sphere phase (SP) of liquid crystal induced by chiral dopant is observed in a narrow temperature range between isotropic and blue phase or between isotropic and chiral nematic phase. The SP consists of three-dimensional twist spheres (3-DTSs) and disclinations among 3-DTSs. The temperature range of the SP has been broadened to more than 85 °C by stabilizing the disclinations with amorphous polymer chains. The electro-optical switching time of the polymer-stabilized SP is demonstrated in sub-millisecond with a low switching electric field of 4.4 V μm{sup −1}, which is of promising applications in displays, 3-D tunable photonic crystals, and phase modulators.
Sputtered vanadium-rich films were subjected to rapid thermal annealing-cooling (RTAC) in air to produce vanadium dioxide (VO{sub 2}) thin films with thermochromic switching behavior. High heating and cooling rates in the thermal oxidation process provided an increased ability to control the film's microstructure. X-ray diffraction patterns of the films revealed less intense VO{sub 2} peaks compared to traditional polycrystalline samples fabricated with a standard (slower) cooling time. Such films also exhibit a high optical switching reflectance contrast, unlike the traditional polycrystalline VO{sub 2} thin films, which show a more pronounced transmittance switching. The authors find that the RTAC process stabilizes the VO{sub 2} (M2) metastable phase, enabling a rutile-semiconductor phase transition (R-M2), followed by a semiconductor–semiconductor phase transition (M2-M1).
As an example of microsystems fabricated by the LIGA-technique (x-ray lithography, electroplating and molding), three systems are described and characterized: a triaxial acceleration sensor system, a micro-optical switch, and a microsystem for the analysis of pollutants. The fabrication technologies are reviewed with respect to the key components of the three systems: an acceleration sensor, and electrostatic actuator, and a spectrometer made by the LIGA-technique. Aa micro-pump and micro-valve made by using micromachined tools for molding and optical fiber imaging are made possible by combining LIGA and anisotropic etching of silicon in a batch process. These examples show that the combination of technologies and components is the key to complex microsystems. The design of such microsystems will be facilitated is standardized interfaces are available.
We consider a method of probe analysis employing fiber-optic a composite Y-circulator design for the implementation of laser-induced fluorescence (LIF) spectroscopy diagnostics. The proposed principle of the LIF analyzer is based on spatially separated directed optical beams of excitation and fluorescence radiations. Conditions of the effective Y-circulator operation as a passive fiber-optic switch are determined. Experimental investigation of the switched radiation losses is performed. An example of using the proposed analyzer for LIF diagnostics of biological media is presented.
Most of the nanoscale fabrication in the semiconductor industry is based on patterning with scanning-electron beam lithography (SEBL). Although this approach is very versatile and has very high resolution, it is intrinsically a serial writing process, and therefore, relatively slow. Our group has been investigating alternative nano-fabrication techniques, adapted from ideas of saturating optical transitions such as those used in stimulated emission-depletion microscopy and related methods, and optical interference lithography. Linewidths and resolutions on the scale of a few tens of nanometers and below are highly desirable for various applications in nanotechnology. However, the spatial resolution of optical lithography is restricted by diffraction. In the past, we developed absorbance modulation to overcome this limit. This approach utilizes photochromic molecules that can be optically switched between two thermally stable states, one opaque and the other transparent. However, absorbance modulation is limited to surface (2-D) patterning. Here, we report on an alternative approach that exploits unique combinations of spectrally selective reversible and irreversible photochemical transitions to achieve deep subwavelength resolution with potential extension to 3-dimensions. This approach, which we refer to as patterning via optical-saturable transformations have the potential for massive parallelism, enabling the creation of nanostructures and devices at a speed far surpassing what is possible with SEBL. The aim of our research is to translate the success in circumventing Abbe's diffraction limit in optical microscopy to optical lithography.
Ferroelectric nematic liquid crystals represent not only fascinating, fundamental science, but they also hold promise for new technologies including high-density power storage or sub-millisecond switching information displays. In this work, we describe the synthesis and measurements of the physical properties of a new compound, 4-nitrophenyl 4-[(2,4-dimethoxylbenzoyl)oxy]-2-fluorobenzoate (RT11001). This material exhibits multiple, highly polar, ferroelectric nematic phases that have not been previously reported. Here we employ a wide range of physical characterisation methods including differential scanning calorimetry (DSC), mass density measurement, optical birefringence, polarising optical microscopy (POM), dielectric spectroscopy, electric current analysis, electro-optical switching, small-angle and wide-angle x-ray scattering measurements to show that RT11001 has multiple, distinct ferroelectric phases. We argue that the highest temperature phase is a polar nematic fluid with non-polar smectic clusters. Directly below appears to be a transition to another polar nematic phase containing polar positionally ordered clusters. Lastly, there are indications of an additional, polar biaxial liquid crystal phase at lower temperatures.
Recently, we developed two ultra-fast all-optical switches in the nanosecond and picosecond regimes. The picosecond switch is made of a polydiacetylene thin film coated on the interior wall of a hollow capillary of approximately 50 micron diameter by a photo-polymerization process. In the setup a picosecond Nd:YAG laser at 10 Hz and at 532 nm with a pulse duration of approximately 40 ps was sent collinearly along a cw He-Ne laser beam and both were waveguided through the hollow capillary. The setup functioned as an Exclusive OR gate. On the other hand, the material used in the nanosecond switch is a phthalocyanine thin film, deposited on a glass substrate by a vapor deposition technique. In the setup a nanosecond, 10 Hz, Nd:YAG laser of 8 ns pulse duration was sent collinearly along a cw He-Ne laser beam and both were wave-guided through the phthalocyanine thin film. The setup in this case functioned as an all-optical AND logic gate. The characteristic table of the ExOR gate in polydiacetylene film was attributed to an excited state absorption process, while that of the AND gate was attributed to a saturation process of the first excited state. Both mechanisms were thoroughly investigated theoretically and found to agree remarkably well with the experimental results. An all-optical inverter gate has been designed but has not yet been demonstrated. The combination of all these three gates form the foundation for building all the necessary gates needed to build a prototype of an all-optical system.
Ultrafast modulation of semiconductor quantum well (QW) laser is of technological importance for information technology. Improvement by order(s) of magnitude in data transfer rate is possible as terahertz (THz) radiation is available for heating the laser at picosecond time scale. Optical gain modulation in the QW is achieved via temperature modulation of electron-hole plasma (EHP). Applications include free-space THz communication, optical switching, and pulse generation. The EHP in the semiconductor QW is described with a two-band model. Semiconductor Bloch equations with many-body effects are used to derive a hydrodynamical model for the active QW region. Because of ultrafast carrier-carrier scatterings in the order of 50 fs, EHP follows quasiequilibrium Fermi-Dirac distributions and THz field interacts incoherently with it. Carrier-longitudinal optical (LO) phonon scatterings and coherent laser-EHP interaction are treated microscopically in our physical model. A set of hydrodynamical equations for plasma density, temperature, and laser envelop amplitude are derived and Runge-Kutta method is adopted for numerical simulation. A typical 8 nm GaAs/Al(0.3)Ga(0.7) As single QW at 300 K is used. Additional information is contained in the original extended abstract.