We report the optical architecture, experimental performance, and simulated performance of polarization- maintaining CW and pulsed single clad Tm-doped fiber amplifiers designed to operate over a wavelength span of 1760—1960 nm. We highlight the potential applications of these amplifiers to quantum computing and quantum qubit experiments using 1762 nm light. Our amplifier exhibits 3 W CW output power and 20 W peak pulsed output power (2 MHz rep. rate, 10% duty cycle) at 1762 nm. Measurements of the wavelength response of the TDFA yield an experimental operating bandwidth extending from < 1750 nm to > 1920 nm. Simulations of the amplifier bandwidth indicate a 3 dB (50% FWHM) wavelength span of 1745 nm to 1980 nm (135 nm). Experimental output power and bandwidth results agree well with the simulations. The external noise figure for this amplifier ranges from 7.5 dB to 9.5 dB. No linewidth broadening was observed in a typical TDFA output when using a single frequency input laser source with a linewidth of 10 kHz. We discuss suitability and applications of the TDFA to 1762 nm enabled manipulation of optical qubits in trapped 133Ba+ ions.
We present the design and experimental and simulated results for a 2050 nm band fiber amplifier with high optical-optical slope efficiency and low ion pairing, using a novel high performance single clad Ho-doped fiber from the Naval Research Laboratory (NRL). We report a measured optical-optical slope efficiency of 57% using 1 mW input signal power and 1860 nm pumping which we believe is the highest slope efficiency measured to date for a single clad copumped HDFA. This efficiency is linked to a low ion pairing coefficient of 4% in the doped fiber derived from our data.
We demonstrate ASE pumping of rare-earth-doped fiber amplifiers, fiber lasers, and broadband ASE sources. Pumping with an ASE source yields the advantages of optical-optical efficiencies comparable to conventional pumps, generation of ultra-broad-band ASE sources, and reduced low frequency noise transferred from the pump to the signal.
Highly stable, high peak output power pulsed transmitter sources in the 2000 nm band are essential seed lasers for diverse applications such as LIDAR, ground-to-space optical communications, detection of trace gases in the atmosphere, medical applications, and pumping optical parametric oscillators and supercontinuum sources. Previous work utilizing single clad, single mode fibers has demonstrated pulsed mode operation of an optically amplified source at 2051 nm and 2090 nm with pulse widths ranging from 5–500 ns, pulse repetition frequencies (PRFs) of 20–300 kHz, and peak output pulse energies of 10 μJ. In this paper, we report the design and performance of a novel nanosecond MOPA optical transmitter at a signal wavelength of 2070 nm with more than 250 W peak output power and highly stable output pulses. The seed laser is broadened using a phase modulator, to minimize the onset of optical nonlinearities such as SBS and MI and then amplified using a two-stage Ho-doped fiber amplifier (HDFA) employing 8-μm core active fiber. The amplified signal is then transmitted through a tandem arrangement with a 250 MHz acousto-optic modulator (AOM) followed by a high-speed electro-optic amplitude modulator (EOM). This pulses signal is then reamplified by a two-stage HDFA where the second stage employs a 20-μm core active fiber, which reduces the threshold for the onset of nonlinear effects such as modulation instability (MI) and four-wave mixing. We present a comparison of optical simulation results with experimental data for the medium- and large-core Ho-doped fibers in the MOPA transmitter.
We present the design and performance of novel, highly stable, broadband, packaged single mode Tm-doped and Ho-doped ASE sources in the 2000 nm spectral band. Centroid wavelengths of 1850–1900 nm are achieved for Tm-doped sources and ~2070 nm for Ho-doped sources. Measured -10 dB spectral bandwidths exceed 100 nm for the Tm-doped sources and 60 nm for the Ho-doped sources. Output powers for two stage Tm-doped sources exceed 1 W CW.
We report the results of gamma radiation testing of the performance of 1064 nm packaged butterfly single mode DFB lasers (QD Laser QLD1061) for satellite and space applications. Both passive and active tests were conducted, with measurements of output power, optical signal-to-noise-ratio (OSNR), output spectra, and polarization extinction ratio (PER) as a function of dose rates and total radiation exposure. No significant changes in laser behavior were observed for total doses up to 100 kRad.
We present the design and performance of a narrow linewidth single frequency 2039 nm distributed feedback (DFB) fiber Bragg grating (FBG) fiber laser source with a novel optical pumping configuration at 1567 nm that significantly increases optical-optical pump conversion efficiency. Our new configuration employs an optical circulator and a reflector at 1567 nm to efficiently recycle pump light that is not absorbed in the first pass through the FBG-DFB fiber laser. We report a comparison of simulations with experimental results for the novel high efficiency single frequency 2039 nm Tm-doped fiber laser source.
Coherent nanosecond pulses with high peak powers in the 2μm region are in demand for applications such as LIDAR and atmospheric sensing. In this paper we present a PM pulsed laser based on a MOPA configuration providing up to 50W of peak power. The 2039nm seed laser is a pre-amplified DFB-FBG laser with <10kHz linewidth. Nanosecond pulses produced by an acousto-optic modulator are amplified by a single booster stage amplifier using a double clad PM thulium-doped fiber. We demonstrate >10W of output peak power for 50ns pulses over repetition rates from 50kHz to 2MHz. For 4-μs pulses and a repetition rate of 50kHz, our MOPA delivers 28μJ of pulse energy.
We report the design, optical architecture, and performance of a multi-watt tunable polarization-maintaining Tm-doped fiber laser that can be tuned from 1890—2050 nm. The compact OEM laser exhibits peak fiber coupled output powers of > 3.5 W CW and a linewidth of < 0.05 nm. Data as a function of output wavelength are presented for the output spectrum, output power, OSNR, and long term power stability.
To date, the supersymmetric (SUSY) formalism in optics has been used to engineer the spatial distributions of refractive indices. Here, we use SUSY formalism to engineer the shape of the corrugated dielectric waveguide instead of its refractive index profile to enable the insertion of an arbitrary number of transmission peaks in the stopband. These peaks can be used to make low-power intensity-dependent optical switches. Moreover, at microwave frequencies, the embedded states can be used to design leaky wave antennas, capable of scanning continuously from forward to the backward direction through broadside without degradation in beam quality.
The growing demand for high-capacity optical-transmission technologies sparked the growth of integrated and silicon photonics. Efficient on-chip manipulation of optical signals requires development of high-fidelity Y-junctions, photonic lanterns, mode filters and multiplexers, and interferometers.
The concept of supersymmetry (SUSY) originated in the fields of particle physics and enabled treatment for bosons and fermions on equal footing. Supersymmetry has expanded to quantum mechanics, and optics where it can be used, for instance, to design (de)multiplexing arrays of waveguides. To date, the majority of optical applications employed the unbroken SUSY that relates partners supporting the same set of eigenstates with the exception of the fundamental state.
We propose a design of a mode sorter made of fully iso-spectral permittivity profiles related by a continuous SUSY transformation in the broken regime. This ensures that the propagation constants of the all the modes to be sorted are preserved along the length of the device. As a result of this global matching of the propagation constants, the SUSY design allows for reduction of the modal cross-talk by two orders of magnitude compared with a standard asymmetric Y-splitter. Moreover, the SUSY mode sorter operates for both transverse-electric and transverse-magnetic light polarization, and it shows low losses and modal cross-talk over a broad wavelength range (1300-1700 nm). Compared with the previous SUSY based modes sorters, our design offers similar performance with an order of magnitude smaller sorter length and can separate modes without losing energy via radiative modes.
Topological insulators are materials that behave as insulators in their interior but support boundary conducting states due the non-trivial topological order. These edge states are robust to defects and imperfections, allowing lossless energy transport along the surface. Topological insulators were first discovered in field of electronics, but recently photonic analogues of these systems were realized. Most of experimentally demonstrated photonic topological insulators to date are bulky, incompatible with current semiconductor fabrication process or operate in microwave frequency range. In this work, we show silicon photonic-crystal-based Valley-Hall topological insulator operating at telecommunication wavelengths. Light propagation along the trapezoidally-shaped path with four 120 degrees turns is demonstrated and compared with propagation along the straight line. Nearly the same transmittance values for both cases confirm robust light transport in such Valley-Hall topological photonic crystal. In the second part of this talk, we discuss the possibility of dynamic tuning of the proposed topological insulator by modulation of the refractive index of silicon. The modulation is facilitated by shining focused ultraviolet pulsed light onto silicon photonic crystal slab. Ultraviolet light illumination causes formation of electron-hole pairs, excitation of free-carriers and results into decrease of refractive index with estimated modulation on the order of 0.1. Due to the index change, spectral position of the bandgap and the edge states shift allowing their dynamic control. Proposed concept can find applications in communication field for fast all-optical switching and control over light propagation.
Optical beams with a phase term proportional to the azimuthal angle possess a singularity at the beam center and carry an orbital angular momentum (OAM). The OAM beams find important applications including the trapping and rotation of microscopic objects, atom-light interactions and optical communications. The OAM beams can be generated by spiral phase plates or spatial light modulators which are bulky. Recently, planar optical components including q-plates, arrays of nano-antennas and all-dielectric metasurfaces, have attracted significant attention. However, they lack reconfigurability, which means that once the components are fabricated, their functionality cannot be changed.
In this work, we experimentally demonstrate a nonlinear metasurface-based beam converter which is designed to transform a Hermite-Gaussian beam to a vortex beam with an OAM in a transmission mode. The proposed converter is built of an array of nano-cubes made of chalcogenide(As2S3) glass. Chalcogenides offer several advantages for designing all-dielectric, nonlinear metasurfaces, including high linear refractive index at near-infrared wavelengths, low losses, and relatively high third-order nonlinear coefficient. In particular, reconfigurability is enabled by the intensity-dependent refractive index or Kerr nonlinearity. Input Hermite-Gaussian beam at low intensity transmitting through the metasurface acquired an OAM, while at high intensity, remained its original intensity and phase profile. The parameters of the reconfigurable metasurface were optimized and its functionality was verified using numerical simulation and in laboratory experiments. Compared to conventional metasurfaces, their nonlinear counterparts are likely to enable a number of novel devices for all-optical switching and integrated circuits applications.
The concept of supersymmetry originated in the fields of particle physics and enabled treatment for bosons and fermions on equal footing. Supersymmetry has rapidly expanded to other fields such as quantum mechanics, where it provided a way of generating pairs and families of potentials with similar properties, e.g. different reflection-less potentials; and optics where it can be used to design (de)multiplexing arrays of waveguides.
In the first part of the talk, we show that for parity-time symmetric structures supersymmetric transformation is isospectral only locally (at a specific amplitude of gain and loss). Moreover we show that depending on whether a passive mode (with real propagation constant) or an active mode (with gain or loss) is removed, the parity-time symmetry of the system is preserved or broken as a function of gain/loss amplitude.
In the second part of the talk we investigate the influence of supersymmetric transformation on the scattering spectrum of reflection-less structures and systems with epsilon-near-zero materials. We show that the transmission/reflection properties of a structure containing an epsilon-near-zero material can be mimicked using materials with refractive index values above unity, which are more easily accessible and introduce smaller losses to the system. The relation between these two systems is governed by supersymmetry. We conduct a quantitative performance analysis of realistic structure in which the continuous variation of the refractive index is replaced by the step-wise profile corresponding to a realistic layered structure.
Our studies pave the way towards achieving remarkable properties of the epsilon-near-zero materials with the use of much more accessible materials compatible with the state-of-the-art integrated optics fabrication.
Colloidal suspensions offer as a promising platform for engineering polarizibilities and realization of large and tunable nonlinearities. Previous studies of Gaussian beams propagation in various colloidal suspensions predicted in a number of remarkable optical phenomena and applications, including initiation and regulation of chemical reactions, sorting different species of nanoparticles and imaging through highly scattering media. As compared to the conventionally used Gaussian beams, optical vortices that are characterized by the doughnut-shaped intensity profile and a helical phase front offer even more degrees of freedom for, in particular, optical trapping or imaging applications. In our earlier work, we predicted, using the linear stability analysis and numerical simulations, that the perturbations with an orbital angular momentum of a particular charge will be amplified and lead to the formation of a necklace beam with a particular number of peaks, or “beads.” Here, we performed detailed experimental studies of such necklace beam formation that show an excellent agreement with the analytical and numerical predictions. This work might bring about new possibilities for dynamic optical manipulation and transmission of light through scattering media as well as formation of complex optical patters in colloids.
High-power femtosecond filaments—laser-light beams capable of kilometer-long propagation—attract interest of nonlinear-optics community due to their numerous applications in remote sensing, lightning protection, virtual antennas, and waveguiding. Specific arrangements of filaments, into waveguides or hyperbolic metamaterials, allow for efficient control and guiding of electromagnetic radiation, radar-beam manipulation, and resolution enhancement. These applications require spatially uniform distribution of densely packed filaments.
In order to address this challenge, we investigate the dynamic properties of large rectangular filament arrays propagating in air depending on four parameters: the phase difference between the neighboring beams, the size of the array, separation between the beams, and excitation power. We demonstrate that, as a result of the mutual interaction between the filaments, the arrays where the nearest neighbor beams are out-of-phase are more robust than the arrays with all the beams in phase.
Our analysis of the array stability reveals that there exist certain trade-offs between the stability of a single filament and the stability of the entire array. We show that in the design of the experiment, the input parameters have to be chosen in such a way that they ensure a sufficiently high filling fraction, but caution has to be used in order not to compromise the overall array stability.
In addition, we show the possibility of filament formation by combining multiple beams with energies below the filamentation threshold. This approach offers additional control over filament formation and allows one to avoid the surface damage of external optics used for filamentation.
Structured light and structured matter are two fascinating branches of modern optics that recently started having a significant impact on each other. However, integrating structured light, which commonly is created using bulk optics, on miniaturized silicon chips represents a significant challenge. In this talk, we discuss fundamental optical phenomena at the interface of structured light and engineered optical structures, including theoretical and experimental studies of light-matter interactions of vector and singular optical beams in optical metamaterials and microcavities. The synergy of complex beams, such as the beams carrying an orbital angular momentum (OAM), with nanostructured “engineered” media is likely to bring new dimensions to the science and applications of structured light ranging from fundamentally new regimes of spin-orbit interaction to novel ways of information encoding for the future optical communication systems.
We show that unique optical properties of engineered micro- and nanosctructures open unlimited prospects to “engineer” light itself. We discuss several approaches to ultra-compact structured light wavefront shaping using metal-dielectric and all-dielectric resonant metasurfaces. Moreover, by exploiting the emerging non-Hermitian photonics design at an exceptional point, we demonstrate a microring laser generating a single-mode OAM vortex lasing with the ability to precisely define the topological charge of the OAM mode. We show that the polarization associated with OAM lasing can be further manipulated on demand, creating a radially polarized vortex emission. Our OAM microlaser could find applications in the next generation of integrated optoelectronic devices for optical communications in both quantum and classical regimes.
Colloidal metamaterials are a robust and flexible platform for engineering of optical nonlinearities and studies of light filamentation. To date, nonlinear propagation and modulation instability of Gaussian beams and optical vortices carrying orbital angular momentum were studied in such media.
Here, we investigate the propagation of necklace beams and the conservation of the orbital angular momentum in colloidal media with saturable nonlinearity. We study various scenarios leading to generation of helical necklace beams or twisted beams, depending on the radius, power, and charge of the input vortex beam. Helical beams are build of two separate solitary beams with circular cross-sections that spiral around their center of mass as a result of the equilibrium between the attraction force of in-phase solitons and the centrifugal force associated with the rotational movement. A twisted beam is a single beam with an elliptical cross-section that rotates around it's own axis. We show that the orbital angular momentum is converted into the rotational motion at different rates for helical and twisted beams.
While earlier studies reported that solitary beams are expelled form the initial vortex ring along straight trajectories tangent to the vortex ring, we show that depending on the charge and the power of the initial beam, these trajectories can diverge from the tangential direction and may be curvilinear. These results provide a detailed description of necklace beam dynamics in saturable nonlinear media and may be useful in studies of light filamentation in liquids and light propagation in highly scattering colloids and biological samples.
The emergence of metamaterials also has a strong potential to enable a plethora of novel nonlinear light-matter interactions and even new nonlinear materials. In particular, nonlinear focusing and defocusing effects are of paramount importance for manipulation of the minimum focusing spot size of structured light beams necessary for nanoscale trapping, manipulation, and fundamental spectroscopic studies. Colloidal suspensions offer as a promising platform for engineering polarizibilities and realization of large and tunable nonlinearities. We will present our recent studies of the phenomenon of spatial modulational instability leading to laser beam filamentation in an engineered soft-matter nonlinear media as well as in negative index metamaterials. We will also discuss the possibilities of guiding, manipulating, and processing radio-and microwave-frequency radiation using photonic structures built of filaments in air. In particular, we introduce so-called virtual hyperbolic metamaterials formed by an array of plasma channels in air as a result of self-focusing of an intense laser pulse, and show that such structure can be used to manipulate microwave beams in a free space. Generation of virtual hyperbolic metamaterials requires a regular and spatially invariant distribution of plasma channels. Therefore, we discuss the generation of such large regular arrays of filaments and consider the interactions between multiple filaments, multiple filament formation, and phase-controlled structured filaments.
We study the behavior of refracted angle for k-vector at the interface of uniaxial anisotropic media in the case of nanosphere dispersed liquid crystal (NDLC) matematerial. Finite Element (FE) calculations (COMSOL Multiphysics) are used to trace the propagation of the electromagnetic wave. Preliminary results on the influence of incident angle on refracted angle wave-vector are presented.
We discuss the effect of a negative refraction at the interface of uniaxial anisotropic media in the case of nanosphere dispersed liquid crystal (NDLC) matematerial. Finite Element (FE) calculations (COMSOL Multiphysics) are used to trace the propagation of the electromagnetic wave. We show that for chosen values of the parameters of nanospheres and of nematic liquid crystal (NLC) host negative refraction can be obtained for a wide range of incident angles.
In this paper the concept and design of infrared cloaking using nanosphere dispersed liquid crystal (NDLC)
matematerial in cylindrical geometry is presented for TM polarization of incident light. The influence of material
losses on the cloaking efficiency is discussed. The loss can be tuned by changing design parameters.
We discuss the concept of infrared cloaking using nanosphere dispersed liquid crystal (NDLC) matematerial in
cylindrical geometry for TM polarization. The system consists of layers of NDLC with different values of ordinary
refractive index and the same value of extraordinary refractive index of liquid crystal host. Finite element
calculations (COMSOL Multiphysics), which include the Poynting vector calculations, show that scattering from
the hidden object is limited in the presence of the layered cloak.
We discuss the concept of infrared cloaking using nanosphere dispersed liquid crystal (NDLC) matematerial in
cylindrical geometry for TM polarization. The system consists of six layers of NDLC with different values of
ordinary refractive index. Finite element calculations (COMSOL Multiphysics) show that scattering from the
hidden object is strongly limited in the presence of the cloak.
We discuss the concept of infrared cloaking using nanosphere dispersed liquid crystal (NDLC) matematerial in
cylindrical geometry. Preliminary results show that NDLC is a promising candidate for cloak design. Monte
Carlo simulations are used for the design.
Monte Carlo studies of the field induced complex refractive index changes in nano-dispersed nematic liquid crystals
exhibiting negative - positive refractive indices1, 2 have been performed for various cases of applied field
strengths,3 anchoring profiles and temperatures over a broad spectral regime. The resultant induced spatially
inhomogeneous molecular order and the corresponding metamaterial properties are obtained for various wavelengths,
applied field strengths, anchoring forces and temperatures below and above the Freedericksz transition.
In general, the director axis reorientation and the resultant refractive index distribution are spatially inhomogeneous,
even under an uniform applied field. The detailed computation have identified parameter sets for obtaining
negative index of refraction and maximal index modulations that can be more than an order of magnitude larger
than those obtainable from pure NLC systems.
Recently, we have discussed anchoring forces and the electric field as new control parameters for negative-
positive refraction index tuning in nanosphere dispersed nematic liquid crystal (NDLC). The present study is
focused on calculation of the amplitude modulation of the refractive index caused by amplitude variation of
anchoring forces and spatial modulation of anchoring forces. Preliminary results indicate that, similarly to
case studied earlier,1 refractive index amplitude modulation can be significantly larger as compared with a
conventional liquid crystal (LC) system. The inhomogeneous molecular order in nematic liquid crystal (NLC)
cells is modelled using Monte Carlo simulations with the Lebwohl-Lasher effective Hamiltonian with the Rapini-
Papoular term for anchoring forces.
Khoo et al.1 have introduced the concept of tuning of negative refractive index using nanosphere dispersed
nematic liquid crystal (NDLC). Recently,2, 3 we have discussed anchoring forces as a new control parameter for
negative-positive refraction index tuning in NDLC. In particular, we have calculated3 the phase diagrams in
variables electric field - anchoring force for real and imaginary parts of permittivity and permeability for NDLC
using averaged (global) value of refractive index for the inhhomogeneous system. In current paper we analyze an
influence of anchoring forces and of spatial modulation of electric field on local distribution of negative refraction
index in NDLC. The study constitutes a generalization of homogenous isotropic dielectric layer approximation
used in papers.1 Inhomogeneous molecular order in planar NLC cells is modeled using Monte Carlo simulations
with Lebwohl - Lasher effective hamiltonian and Rapini - Papoular term for anchoring forces.
Khoo et al.1, 2 have shown that nanosphere dispersed nematic liquid crystal (NDLC) constitutes a new type of
metamaterial with index of refraction tunable from negative to positive values. Recently3 we have combined this
approach with Monte Carlo simulations of inhomogeneous molecular order in planar NLC cells. Lebwohl - Lasher
effective hamiltonian with Rapini - Papoular term for anchoring forces was used. Electric field and amplitude
of anchoring forces are control parameters which determine the profiles of order parameter. In this paper we
study, using the same approach, local spatial distribution of refractive index in NDLC planar cell. We show
that NDLC material consists of layers with negative-zero-positive index of refraction. The spatial organization
of those layers strongly depends on incident light wavelength. The role of spatially modulated external electric
field for tuning of refractive index of NDLC is briefly discussed.
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