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Effective model for nonlinear refraction and extinction coefficients in the presence of stimulated light scattering

Anderson Amaral, Edilson Falcao-Filho, Albert Reyna Ocas, and Cid Bartolomeu de Araujo

Doc ID: 342588 Received 17 Aug 2018; Accepted 17 Oct 2018; Posted 17 Oct 2018  View: PDF

Abstract: We present in this paper a wave-coupled model(WCM) to describe the effective nonlinear (NL)optical response of transparent materials illuminated by strong lightbeams in conditions such that stimulated light scattering is relevant.At low intensities the WCM indicates that the NL scatteringbehaves similarly to a third and fifth order polarizationsusceptibility. However, at sufficient high intensities NL lightscattering will lead to highly non-perturbative effective NL refractionand NL absorption coefficients. This is an important remark, given thatattempts to explain NL scattering contributions as a perturbative NLresponse from data obtained at low intensities will become discrepantfrom the data obtained at high intensities. As an applicationof the model we show that the existing divergent interpretations of thecarbon disulfide (\(\text{CS}_{2}\)) NL response in the picosecond andfemtosecond regimes by several authors can be clarified in the frameworkof the WCM.

Nonlinear Recovery of Narrow Spectral Features with Fast Chirped Readout

Zeb Barber, Lou Oberto, and Wm. Randall Babbitt

Doc ID: 341053 Received 30 Jul 2018; Accepted 16 Oct 2018; Posted 17 Oct 2018  View: PDF

Abstract: A new nonlinear signal processing algorithm for recovery of narrow and high contrast spectral features for fast chirping tunable laser spectroscopy is described. The algorithm improves on previous linear spectral recovery algorithm by estimating and removing nonlinearities resulting from combinations of chirping faster than the conventional spectroscopic limit, large absorption depth, and high contrast spectral features. The new nonlinear algorithm was tested on a set of spectrally narrow holes burned into the inhomogeneous line, both theoretically and experimentally, The experimental data included multiple sets of spectral holes of different depths and widths <~1~ MHz, which spectrally burned into cryogenic Tm$^{3+}$:YAG and readout using a chirp rate of 11.88 MHz/$\mu$s. This technique improves the qualitative and quantitative spectral estimates made by spectral holeburning based RF spectrum analyzers, but can be applied to any tunable laser spectroscopy applications that requires the fast measurement of multiple, high-contrast, and narrow-spectral features.

Robust switching of superposition-states via a coherent double stimulated Raman adiabatic passage

Jing Qian, Luyao Yan, Dandan Ma, and Dongmin Yu

Doc ID: 341190 Received 31 Jul 2018; Accepted 16 Oct 2018; Posted 17 Oct 2018  View: PDF

Abstract: Coherent manipulation of quantum states is of crucial importance in accurate control of a quantum system. A fundamental goal is coherently transferring the population of a desired state with near-unit fidelity. For this propose, we theoretically demonstrate a novel coherent double-stimulated Raman adiabatic passage (STIRAP) in a three-level Λ-type system for realizing the switch of unequal initial preparations on two ground states. This operation uses single optical pulse sequence accomplishing both bright-STIRAP and dark-STIRAP processes, in which the intermediate-level detuning and the pulse delay must be given an optimal adjustment. Besides, owing to the imperfection of double-STIRAP transition, the sensitivity of the switch fidelity with respect to the spontaneous loss from the intermediate state, to the pulse amplitude, and to the population difference, are also discussed. This work suggests a simple and experimentally-feasible all-optical approach to switch the a superposition quantum state, serving as one-step closer to the goal of coherent manipulation of quantum systems.

Noise reduction by a single photo diode in CPT atomic clocks

Ruiyuan Liu, cong wang, Ping Guo, and Jy Zhao

Doc ID: 334265 Received 04 Jun 2018; Accepted 16 Oct 2018; Posted 17 Oct 2018  View: PDF

Abstract: We present a digital differential detection scheme using a single photodiode (PD) to suppress the diode laser frequency noise and improve the short-term stability in atomic clocks based on coherent population trapping (CPT) resonance. In the experimental structure, one laser beam is divided into two beams via modulation of an acousto-optic modulator (AOM). One beam induces CPT resonance with circularly polarized light and the other beam induces only absorption with linearly polarized light. A differential algorithm counteracts common-mode noise from the transmission of linearly and circularly polarized beams. To ensure observed data quality, we control switching between conventional detection and differential detection by simply blocking the linearly polarized beam. With the characteristics of a single photodiode, we do not need to integrate two photo detectors into the system, so problems arising from the asymmetry of double photo diodes are avoided. The stability of 6.86E-12 at 100 s and 2.26E-12 at 1000 s has been demonstrated with the new scheme. Accordingly, it improves the short-term stability of the clock by a factor of 2.4 at 100 s. The proposed scheme promises to develop a new approach to eliminate laser-related noise and explore potential applications in chip-scale atomic clocks.

A Chip-Based Non-Mechanical Beam Steerer in the Mid-Wave Infrared

Jesse Frantz, Jason Myers, Robel Bekele, Christopher Spillmann, Jawad Naciri, Jakub Kolacz, Henry Gotjen, Vinh Nguyen, Collin McClain, Brandon Shaw, and Jasbinder Sanghera

Doc ID: 336489 Received 29 Jun 2018; Accepted 16 Oct 2018; Posted 17 Oct 2018  View: PDF

Abstract: Mid-wave infrared (MWIR) light is critically important for a variety of applications such as chemical sensing and LIDAR. Directional control over MWIR light is required for these applications and is typically accomplished using mechanical devices such as gimbal-mounted mirrors. Mechanical steerers, however, are subject to a host of problems, and replacing them has been a long-standing goal. In this paper, we describe the first non-mechanical beam steerer capable of continuous angular tuning in the MWIR. These devices are chip-based and provide steering in two dimensions without relying on moving parts. Previous work has demonstrated non-mechanical beam steering (NMBS) in the short-wave infrared (SWIR) and near infrared (NIR) using a waveguide in which a portion of the propagating light is evanescently coupled to a liquid crystal (LC) layer in which the refractive index is voltage-tuned. We have extended this NMBS technology into the MWIR by utilizing a unique combination of materials, specifically chalcogenide glass waveguides and LC materials that exhibit high MWIR transparency. We explain the working principles behind these steerers, discuss material considerations for transparency in the MWIR, describe steerer fabrication, and present experimental results showing up to 14° in-plane and 0.6° out-of-plane steering.

Optimized Birefringent Filter Design for Broadly-Tunable Multi-color Laser Operation of Nd-based Lasers: Nd:YAG Example

Umit Demirbas

Doc ID: 337622 Received 02 Jul 2018; Accepted 15 Oct 2018; Posted 17 Oct 2018  View: PDF

Abstract: Nd-based gain media has more than 30 emission lines in the near infrared, which potentially provides a very rich set of lines for multicolor laser operation. On the other hand, due to the methods employed, most of the two-color laser experiments with Nd-systems only demonstrated dual-wavelength operation in just one pair of wavelengths. In this work, we have numerically investigated performance of off-surface optic axis crystal quartz birefringent filters (BRF) as frequency selective elements in two-color laser operation of Nd-doped gain media. Our analysis has shown that, a crystal quartz birefringent filter with an optic axis diving by 25 into the plate could provide two-color laser operation in more than 40 pairs of Nd-lines in properly designed cavities. The two-color operation wavelengths could be adjusted by simple rotation of the birefringent plate about an axis normal to the surface. Fine adjustment of the angle via a motorized rotation stage fed by an error signal from a balanced detector could provide control of power in each lasing line. To our knowledge such diversity in wavelength selection has not been achieved from any Nd-based system before, showing the potential of the method. Moreover, the proposed filters could be used in tuning of two-color lasers in continuous-wave, long-pulsed and femtosecond operation regimes. We believe the proposed system in this work might be useful for experimentalists working on multicolor lasers.

Blowing up light: A nonlinear amplification scheme for electromagnetic waves

Ali Mostafazadeh, Hamed Ghaemi-Dizicheh, and Sasan Hajizadeh

Doc ID: 342855 Received 21 Aug 2018; Accepted 15 Oct 2018; Posted 17 Oct 2018  View: PDF

Abstract: We use blow-up solutions of nonlinear Helmholtz equations to introduce a nonlinear resonance effect that is capable of amplifying electromagnetic waves of particular intensity. To achieve this, we propose a scattering setup consisting of a Kerr slab with a negative Kerr constant placed next to a linear slab in such a way that a left-incident coherent TE wave with a specific incidence angle and intensity realizes a blow-up solution of the corresponding Helmholtz equation whenever its wavenumber k takes a certain critical value, k₀. For k=k₀, the solution blows up at the right-hand boundary of the Kerr slab. For k < k₀, the setup defines a scattering system with a transmission coefficient that diverges as (k-k₀)¯⁴ for k approaching k₀. By tuning the distance between the slabs we can use this setup to amplify coherent waves with a wavelength in an extremely narrow spectral band. For nearby wavelengths the setup serves as a filter. Our analysis makes use of a nonlinear generalization of the transfer matrix of the scattering theory as well as properties of unidirectionally invisible potentials.

Investigation of pernicious oscillation inside a LD-pumped cesium vapor cell

Shunyan Wang, Xiaoxu Liu, Qiang Yu, Guofei An, He Cai, Juhong Han, and You WANG

Doc ID: 344587 Received 30 Aug 2018; Accepted 15 Oct 2018; Posted 18 Oct 2018  View: PDF

Abstract: After finding that some unbelievable laser radiation emitted from a cesium cell end-pumped by a narrow-linewidth laser diode (LD) without any additional oscillator mirrors, we established a kinetic model to theoretically investigate the lasing oscillation inside an alkali vapor cell. Then, we demonstrated that some pernicious oscillation could be generated by three possible oscillators formed by our alkali vapor cell. Afterwards, we built the system mentioned above to experimentally evaluate these undesired lasing oscillation. We also compared the theoretical results with experimental ones of outputted laser power from the both sides of the Cs cell changing with the cell temperature. It has been found that the experimental outputted power from the pump side of the Cs cell was basically greater than the theoretical result. The conclusions could be helpful for the structural design in a high-powered alkali vapor laser system in the near future.

Rigorous formulation of surface plasmon-polariton- waves propagation along the direction of periodicity of one-dimensional photonic crystal

Mehran Rasheed and Muhammad Faryad

Doc ID: 342582 Received 17 Aug 2018; Accepted 14 Oct 2018; Posted 18 Oct 2018  View: PDF

Abstract: A rigorous formulation of the canonical boundary-value problem is presented to find the surface plasmon-polariton waves guided by the interface of the one-dimensional photonic crystal and metal along the direction of the periodicity. The problem is formulated using the rigorous coupled-wave approach and a dispersion equation has been obtained. The Muller's method and Newton--Raphson method were used to obtain illustrative numerical results of the dispersion equation. The solutions were found to converge as the number of Floquet harmonics increases. This formulation does not require the computation of the photonic bandgaps and directly computes the surface-wave modes. This formulation could engender new applications of plasmonics exploiting the neglected interface along the direction of periodicity of the one dimensional photonic crystals.

Trajectory engineering of Airy-Talbot effect via dynamic linear potential

Kaiyun Zhan, Zhendong Yang, and Bing Liu

Doc ID: 342635 Received 17 Aug 2018; Accepted 13 Oct 2018; Posted 17 Oct 2018  View: PDF

Abstract: We demonstrate, both theoretically and numerically, the efficient trajectory manipulation of Airy-Talbot effect in dynamic linear potentials. Exact solutions of this accelerating self-imaging phenomenon, designed by adding shifted copies of the fundamental accelerating beam with arbitrary coefficients, are derived. It is shown that Airy-Talbot effect can follow predefined trajectory by engineering the index gradient, while its Talbot length is same as that in free space. The generalization to higher dimension is also discussed.

Optical vortex trapping and annihilation by means of nonlinear Bessel beams in nonlinearly absorbing media

Miguel Porras, Francisco Ramos, and José García-Riquelme

Doc ID: 340158 Received 19 Jul 2018; Accepted 13 Oct 2018; Posted 17 Oct 2018  View: PDF

Abstract: In nonlinear Kerr media at intensities such that multiphoton absorption is significant, a vortex of topological charge $m$ in the center of a high-order nonlinear Bessel beam (NBB) can be stable and subsist endlessly. We show that the $m$-charged NBB is not only stable but is formed spontaneously from any other $n$-charged NBB and $N$ "foreign" vortices of total charge $s$ randomly nested in the beam cross section if $n+s=m$. All nested vortices merge in the center of the original NBB, which undergoes a mode conversion to the NBB that preserves the topological charge and the inward-directed power current that sustains the diffraction-free and attenuation-free propagation in the medium with nonlinear absorption. We foresee different applications such as the creation of stable, multiply charged vortices without tight alignment requirements but by spontaneous vortex combination, mixing waves or particles that the vortices can guide, fast annihilation of vortex dipoles, and cleaning of speckled beams by massive annihilation of vortices.

Vortex lattices with transverse-mode-locking states switching in a large-aperture off-axis-pumped solid-state laser

Yijie Shen, Zhensong Wan, Xing Fu, and Mali Gong

Doc ID: 340490 Received 24 Jul 2018; Accepted 11 Oct 2018; Posted 12 Oct 2018  View: PDF

Abstract: We report the optical vortex lattices (OVL) beams with phase-singularity arrays from a large-aperture diode-pumped Yb:CALGO laser. A distinct transverse-mode-locking (TML) effect is found in the OVL formation via controlling pump aperture and off-axis displacement. Various OVL patterns with vortex arrays can be generated in a TML state. While in a non-TML state, the emission is always a high-order Hermite-Gaussian or Ince-Gaussian mode. Interestingly, a stable TML can be started from a non-TML state by an intentionally induced perturbation. Based on TML principle, a new closed-form expression is theoretically proposed for interpreting both the transverse patterns and the evolution principle of various OVL modes, showing good agreements with the experimental results.

Creating mid-infrared single photons

Richard McCracken, Francesco Graffitti, and Alessandro Fedrizzi

Doc ID: 340177 Received 23 Jul 2018; Accepted 10 Oct 2018; Posted 12 Oct 2018  View: PDF

Abstract: Single-photon creation through parametric downconversion underpins quantum technology for quantum sensing and imaging. Here we numerically study the creation of single photons in the near- and mid-infrared regime from 1.5-12μm in a range of novel nonlinear semiconductor and chalcopyrite materials. We identify phase-matching conditions and single out regimes in which group-velocity matching can be achieved with commercially available pump lasers. Finally, we discuss how mid-infrared single photons can be detected. Using our numerical results, we identify materials and pump lasers for up-conversion detection in conventional wavelength bands. Our study provides a complete recipe for mid-IR single-photon generation and detection, opening up quantum enhancements for mid-IR applications such as bio-medical imaging, communication, and remote sensing.

“Hybridized” amplification of superposition of coherent states with homodyne detection

Changhun Oh and Hyunseok Jeong

Doc ID: 341354 Received 01 Aug 2018; Accepted 08 Oct 2018; Posted 10 Oct 2018  View: PDF

Abstract: We investigate an experimentally feasible scheme for amplification of superpositions of coherent states (SCSs) in light fields. This scheme mixes two input SCSs at a 50:50 beam splitter and performs post-selection by a homodyne detection on one output mode. The key idea is to use two different types of SCSs with opposite parities for input states, which results in an amplified output SCS with a nearly perfect fidelity.

A general solution to wave propagation in media undergoing arbitrary transient or periodic temporal variations of permittivity

Mahdi Chegnizadeh, Khashayar Mehrany, and Mohammad Memarian

Doc ID: 340457 Received 24 Jul 2018; Accepted 08 Oct 2018; Posted 09 Oct 2018  View: PDF

Abstract: A novel and general formulation for wave propagation in time-varying media is presented. Unlike previous reports, our formalism is able to solve propagation in media with arbitrary time-variations of permittivity or permeability, for both transient and steady-state periodic variations. The formulation is approximate yet strikingly accurate in most practical cases. The provided closed form expressions show that the normalized average power after the transition of the permittivity does not depend on the details of the transition while the energy density does. Some important discussions are made about time-periodic media and it is shown that there is an accumulation of energy when the Bragg condition is met. All results are validated through comparison against analytical or numerical solutions.

Ultrafast excitation of conduction-band electrons by high-intensity ultrashort laser pulses in wide-band-gap solids: Vinogradov equation vs Drude model

Olga Sergaeva, Vitaly Gruzdev, Drake Austin, and Enam Chowdhury

Doc ID: 331595 Received 24 May 2018; Accepted 07 Oct 2018; Posted 09 Oct 2018  View: PDF

Abstract: Heating of conduction-band electrons is one of the major processes of energy absorption and transfer in high-intensity ultrafast laser interactions with band-gap solids. It is frequently simulated by assuming high rate of electron-phonon collisions to support intensive one-photon absorption. We utilize the approximation of rare electron-phonon collisions and the non-perturbative Vinogradov equation for the rate of collision-assisted absorption by electrons performing laser-driven oscillations. Band-structure modification by ponderomotive energy of the oscillations is taken into account. The Vinogradov model delivers highly non-equilibrium distribution of the conduction electrons dominated by ponderomotive energy of the oscillations. Presented data suggest substantial reconsideration of the physics of ultrafast free-carrier heating.

Ultrabroadband supercontinuum generation through filamentation in lead fluoride crystal

Yang yuxia, wanjun bi, Xia Li, Meisong Liao, Weiqing Gao, Yasutake Ohishi, Yongzheng Fang, and Yigui Li

Doc ID: 341889 Received 08 Aug 2018; Accepted 05 Oct 2018; Posted 09 Oct 2018  View: PDF

Abstract: We report the filamentation and supercontinuum generation of femtosecond pulse in a piece of bulk lead fluoride (PbF2) crystal with high bandgap and ultra-broadband frequency window covering 5.6 octaves. A broadband supercontinuum spanning 4.7 octaves from 350 to 9000 nm is demonstrated. The filament traces and bright conical visible emission patterns of the supercontinuums are observed. Additionally, simulations are performed to investigate the supercontinuum generation in the PbF2 crystal by using waveguide model which considers the supercontinuum generated in the filamentation as a pulse propagated process in the waveguides writing by filamentation. The findings of this study demonstrated that PbF2 crystal is a very suitable nonlinear medium used for supercontinuum generation by filamentation. This is of significance for the development of ultra-broadband SC sources based on bulk media and high-peak power lasers.

Experimental Evidence of Two-Photon Absorption and its saturation in Malachite Green Oxalate: A Femtosecond Z-scan Study

Anshu Gaur, Hamad Syed, Yendeti Balaji, and Venugopal Rao Soma

Doc ID: 335566 Received 20 Jun 2018; Accepted 05 Oct 2018; Posted 09 Oct 2018  View: PDF

Abstract: Third order nonlinear optical properties of malachite green oxalate (MGO) dye were systematically studied at different input intensities and in a wide range of wavelengths by the Z-scan method using ~150 fs, MHz femtosecond pulses. The sample transmittance results are explained by fitting the data with phenomenological models of linear and multi-photon absorption, and their saturations. Intensity dependent measurement shows the influence of saturation on the absorption process. The data suggests that by tuning the input intensity single or combination of nonlinear phenomena can be achieved in MGO. Wavelength based measurements reveal a strong correlation between linear and nonlinear optical responses. The combinations of two- and three photon absorption and saturation of two-photon absorption occur simultaneously in a wide wavelength range (750-900 nm). Nonlinear absorption cross-sections have been calculated using fitted saturation intensity data. Two- and three-photon absorption coefficients (including an excited state) are determined as the excitation mechanisms of nonlinear absorption in MGO.

Scheme for enhancing quadripartite entangled opticalmodes from an opto-mechanical system

Jing Zhang, Xiaoyu Liu, Rongguo Yang, and Tiancai Zhang

Doc ID: 328994 Received 23 Apr 2018; Accepted 03 Oct 2018; Posted 04 Oct 2018  View: PDF

Abstract: Multipartite entanglement is a key resource for quantum information processing and quantum communication.We show that the robust entanglement among four filtered output optical modes can be achievedwhen there is a nonlinear crystal inside an opto-mechanical cavity. The optical parametric amplifier (OPA) gives rise to single-mode squeezing of the cavity modes, therefore the entanglement among four output optical modes can be enhanced remarkably. Furthermore, the degree of quadripartite entanglement is influenced by the nonlinear gain of OPA and the bandwidth of filters. Large entanglement can be obtained by optimizing the filter functions, which is important for utilizing the entangled light beams more efficiently in real experiments. And such kind of multipartite entanglement will be useful and valuable in the area of quantum communication networks.

Correlated electron beam microbunching andshot-noise characterization with near and far fieldoptical transition radiation

Ariel Nause, Reuven Ianconescu, and Avraham Gover

Doc ID: 341655 Received 06 Aug 2018; Accepted 03 Oct 2018; Posted 04 Oct 2018  View: PDF

Abstract: In this work we demonstrate how to analyze the dynamics of the correlated longitudinal current noiseabove and below the Poissonian shot-noise level in an e-beam, by calculating the emitted TransitionRadiation (OTR) using a complex vector field formulation which is exact in the near and far field. We simulatea non zero emittance electron beam, uncorrelated in the transverse cross section, but with differenttypes of longitudinal correlations, resulting in Coherent Optical Transition Radiation (COTR). We showhow this method is applied on the opposite case (suppression), by tracking simulated beam particles thatcorrelate due to quarter plasma oscillation during drift, and show how the OTR tracks the dynamics ofthe electron beam noise level.

Unveiling of control on polarization of supercontinuum spectra based on ultrafast birefringence induced by filamentation

Hui-Tian Wang, Ping-Ping Li, Mengqiang Cai, Jia-Qi Lv, Dan Wang, Gui-Geng Liu, Chenghou Tu, and Yongnan Li

Doc ID: 340025 Received 17 Jul 2018; Accepted 02 Oct 2018; Posted 03 Oct 2018  View: PDF

Abstract: An intensity pump femtosecond (fs) pulse incident into a transparent medium will produce the filamentation and accompany the supercontinuum (SC) spectrum generation. The polarization of the SC spectrum is always parallel to that of the pump pulse. How to control the polarization of the SC spectrum is a very interesting and crucial issue, due to its great potential applications such as in remote-sensing and time-resolved spectroscopy. Here we present a method to control the polarization of the SC spectrum generated in an optical isotropic medium, based on the nonlinear interaction between the two pump pulses with different linear polarizations. During the fs pulse filamentation, the optical Kerr effect induces the ultrafast birefringence in the optical isotropic medium, which leads to different refractive indices in the two orthogonal directions parallel and perpendicular to the incident polarization, hence the resulting relative phase difference changes the polarizations of the pump pulses. The polarization states of both the pump pulses and the SC spectra can be achieved by changing the angle between the polarization directions of two pulses. We unveil the mechanism of the polarization changes of the pump pulses and the SC spectra.

Mid-infrared optical characterization of InGaAsP

Alice Bernard, Marco Ravaro, Iännis Roland, Jean-Michel Gerard, Michel Krakowski, Olivier Parillaud, Bruno Gérard, Ivan Favero, and Giuseppe Leo

Doc ID: 337678 Received 02 Jul 2018; Accepted 01 Oct 2018; Posted 02 Oct 2018  View: PDF

Abstract: We present a measurement of the refractive index of In(1-x)Ga(x)As(y)P(1-y) lattice-matched to InP outside of the range available in literature. We have accurately determined the refractive index of In(1-x)Ga(x)As(y)P(1-y) lattice-matched to InP as a function of wavelength (λ = 1.55, 2.12 and 3 µm) and arsenic molar fraction (y = 0.55, 0.7 and 0.72). Data is interpolated with a theoretical model and compared to literature whenever possible. Agreement with currently available data is good. Uncertainties are estimated, the largest one being related to the samples composition. We also measure propagation losses dominated by scattering (0.15 to 1.2 cm-1) in ridge waveguides, for the same range of compositions at wavelengths 1.55 µm and 2.12 µm.

Magneto-optical control of Imbert-Fedorov shifts of a light beam reflected from interfaced monolayer graphene

luo chang-you, zhiteng wang, Xiaoyu Dai, and Yuanjiang Xiang

Doc ID: 335329 Received 20 Jun 2018; Accepted 30 Sep 2018; Posted 09 Oct 2018  View: PDF

Abstract: We investigate the Imbert-Fedorov (IF) shifts of a reflected light beam from the dielectric interface containing a planar anisotropic monolayer graphene sheet which subject to an external perpendicular magnetic field. We calculate and discuss the dependence of the IF shifts on the intensity of the magnetic field, the incidence angle of the beam and the central frequency of the beam. It is shown that IF shifts can be controlled by modifying the intensity of the magnetic field and the incidence angle without changing material and the structure of the dielectric interface. Moreover, there exists an optimum nonzero control magnetic field under which the IF shift can reach maximum value.

Flexible Design of Multifocal Metalenses Based on Autofocused Airy Beams

Mahdieh Hashemi, mohammad mahdi shanei, and Carlos Zapata-Rodriguez

Doc ID: 340222 Received 19 Jul 2018; Accepted 29 Sep 2018; Posted 03 Oct 2018  View: PDF

Abstract: Extreme miniaturization of on-demand optical devices such as ultrathin lenses is currently on permanent progress based on novel materials and nanotechnologies. Flexibility and tunability in engineering layouts enable efficient integration of complex photonic modules. In this respect, here we designed an Autofocused Airy (AFA)-based metalens which operates, depending on the molded phase profile, as a multifocal focusing lens which up to our knowledge has not been reported before. To do this, we call the attention to the fact that the two conjugate focal points of an AFA beam can be brought into the real space by applying a proper convex lens phase profile. Considering full control of the phase and amplitude of the incident light with dielectric C-shaped metaatoms, we conceived that both generations of the AFA beam and its focusing with a convex lens could be carried out by a compact wavelength-scale metasurface. In addition, hybrid AFA focusing and phase-only lensing are demonstrated as a versatile method to be implemented in designing multifocal setups.

Electrodiffusion of molecules in porous glass under the action of laser excitation

Igor Meshkovskiy and George Miroshnichenko

Doc ID: 338361 Received 10 Jul 2018; Accepted 25 Sep 2018; Posted 27 Sep 2018  View: PDF

Abstract: An original molecular separation method is proposed and investigated in which optical excitation of the molecules to be separated is used. The transition of molecules to an excited state substantially reduces their mobility on the capillary surface. An original model of molecular mobility is presented. It is shown that, due to the intercombination conversion, the excited molecules are amassed in the triplet excited state. An analysis of the mobility of excited molecules shows that molecules in a triplet excited state have six times less mobility than molecules in the ground singlet state.

Theoretical investigation of the capture effect inIMDD-based microwave photonic mixers

S.Esmail Hosseini and M. Mahdi Keshavarz

Doc ID: 332276 Received 21 May 2018; Accepted 04 Sep 2018; Posted 04 Sep 2018  View: PDF

Abstract: We study the large-signal behavior of microwave photonic (MWP) mixers to investigate the small-signal suppression phenomenon commonly referred to as the capture effect. We introduce and theoretically study the capture effect in the context of MWP mixers. Theoretical expressions are derived for calculatingthe capture effect in three basicMWPmixer types based on intensity-modulation direct-detection (IMDD). We show that the capture effect is not only a function of the power ratio between the input radio-frequency (RF) signals to the MWP mixers, but also depends on the absolute value of their powers. We extendthe study to different unequal-power frequency components of a signal, and as a practical example, we investigate the capture effect when a narrowband FM signal is applied to the RF input of an IMDD-based MWP mixer, theoretically demonstrating considerations and limitations in using MWP mixers.

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