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Accepted papers to appear in an upcoming issue

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March


Reliable multiple pulse reconstruction from second-harmonic generation frequency-resolved optical gating spectrograms

  • Fedor Mitschke, Alexander Hause, Philipp Rohrmann, and Sven Kraft
  • received 11/05/2014; accepted 03/02/2015; posted 03/05/2015; Doc. ID 226231
  • [full text: PDF (1452) KB)]
  • Abstract: Frequency-resolved optical gating (FROG) has become an established method to assess the amplitude-and-phase profiles of ultrashort laser pulses. Second harmonic generation (SHG) FROG is the most widely used version because it is relatively simple to set up and operate. However, for some complex pulse shapes it tends to produce false results. Here we discuss the reconstruction of multiple pulse structures, a situation in which SHG FROG frequently fails. We suggest a modification of the standard procedure and demonstrate that the rate of false results is significantly reduced. We also discuss reconstruction in the presence of noise. A procedure to obtain error bars is given; they allow to gauge the quality of the reconstruction.

Keywords (OCIS):

  • (320.0320) Ultrafast optics : Ultrafast optics
  • (320.7100) Ultrafast optics : Ultrafast measurements

Optical and Transport Characteristics of Raman Injection Laser with Enhanced Stokes Emission

  • hossein yousefvand and Vahid Ahmadi
  • received 12/04/2014; accepted 03/02/2015; posted 03/04/2015; Doc. ID 224938
  • [full text: PDF (662) KB)]
  • Abstract: Detailed theoretical study and modeling of Raman injection quantum cascade laser (RI-QCL) with modification of structure for improved laser performance are presented.The band structure of RI-QCL utilizing techniques with both material-dependent effective mass and band nonparabolicityis calculatedby solving the Schrodinger–Poisson equations self-consistently. With combination of coherent transport and simplified five-level rate equations model, we present a theory describing the Stark-effect rollover in QC lasers. This leads to a compact predictive model to analyze the output characteristics of a QC laser, such as the electric field-current (F-I), light-electric field (L-F) and light-current (L-I) curves. The excellent agreement of the experimental data with the simulated L-I characteristic confirms the validity of our new approach. Additionally, modifications of original RI-QCL structure focus on improving the Stokes-Raman nonlinearity. The results show that, the main characteristics of the modified design including threshold current, external quantum efficiency and output power for both the pump and Stokes lasers are improved in comparison with the reference design. © 2014 Optical Society of America

Keywords (OCIS):

  • (140.3550) Lasers and laser optics : Lasers, Raman
  • (190.0190) Nonlinear optics : Nonlinear optics
  • (290.5910) Scattering : Scattering, stimulated Raman
  • (140.5965) Lasers and laser optics : Semiconductor lasers, quantum cascade

February


Third order nonlinear optical properties exhibited by a bilayer configuration of silver nanoparticles integrated to silicon nanocrystals embedded in ion-implanted silica

  • Carlos Torres-Torres, Alejandra López-Suárez, Bonifacio Can-Uc, Raul Rangel-Rojo, Carlos Valencia, and Alicia Oliver
  • received 11/11/2014; accepted 02/28/2015; posted 03/03/2015; Doc. ID 226749
  • [full text: PDF (632) KB)]
  • Abstract: We present optical Kerr effect, and nonlinear optical absorption studies of two closely spaced distributions of silver nanoparticles embedded in silica containing ion-implanted silicon nanocrystals. The z-scan technique was used to explore the third-order optical nonlinear response at 830 nm with 80 fs pulses. Two-wave mixing experiments were comparatively examined by a vectorial method at 532 nm wavelength using nanosecond pulses. The femtosecond results reveal that both saturated, and two-photon absorption seem to contribute to the nonlinear absorption observed. From nanosecond observations we identify that a remarkable enhancement in the third order optical nonlinearity is achieved by the double-implantation process.

Keywords (OCIS):

  • (160.4330) Materials : Nonlinear optical materials
  • (190.0190) Nonlinear optics : Nonlinear optics
  • (190.3270) Nonlinear optics : Kerr effect
  • (190.4400) Nonlinear optics : Nonlinear optics, materials
  • (160.4236) Materials : Nanomaterials

Optimization of pulse compression in fiber CPA system by adjusting dispersion parameters of temperature-tuned CFBG stretcher

  • Julijanas Zeludevicius, Kestutis Regelskis, and Rokas Danilevicius
  • received 01/13/2015; accepted 02/25/2015; posted 02/26/2015; Doc. ID 232356
  • [full text: PDF (875) KB)]
  • Abstract: In this work we present a femtosecond fiber CPA (FCPA) system with a temperature tuned CFBG stretcher for uncompensated higher-order spectral phase reduction. An improvement in pulse compression through the optimization of nonlinear temperature distribution along CFBG stretcher is predicted numerically and verified experimentally by using CFBG stretcher with 4 independent thermoelectric cooler (TEC) elements.

Keywords (OCIS):

  • (060.2320) Fiber optics and optical communications : Fiber optics amplifiers and oscillators
  • (320.7090) Ultrafast optics : Ultrafast lasers
  • (230.2035) Optical devices : Dispersion compensation devices
  • (060.3735) Fiber optics and optical communications : Fiber Bragg gratings

Improving the sensitivity of optically pumped magnetometers by hyperfine repumping

  • Volkmar Schultze, Theo Scholtes, Rob IJsselsteijn, and Hans-Georg Meyer
  • received 12/04/2014; accepted 02/24/2015; posted 02/25/2015; Doc. ID 229148
  • [full text: PDF (1989) KB)]
  • Abstract: Most optically pumped magnetometers based on alkali atom vapor cells and pumped by a single narrow-band laser suffer from a loss of signal since atoms become trapped in the ground state hyperfine states that are not coupled to the laser beam. This can be counteracted by additional optical repumping these ground state levels. We study hyperfine repumping using cesium vapor cells with partly overlapped ground state splitting due to their nitrogen buffer gas filling. We implement two ways of repumping and compare them to the conventional case of F=4 pumping: F=3 repumping with an additional repumper laser and combined pumping/repumping in the light-narrowing mode, where a single high-power laser is tuned near to the F=3 transitions. The three modes each are investigated for two different ways of spin-phase synchronization; the Mx and intensity modulation method. For both methods, any kind of repumping results in a clear improvement of the magnetometer sensitivity compared to operation without it, but in the Mx mode it is more pronounced (about 50 vs. 200 fT/√Hz for a 50 mm3 Cs vapor cell). The mechanisms responsible for the distinct results in the different working modes are discussed.

Keywords (OCIS):

  • (020.2930) Atomic and molecular physics : Hyperfine structure
  • (020.7490) Atomic and molecular physics : Zeeman effect
  • (040.1880) Detectors : Detection
  • (140.5560) Lasers and laser optics : Pumping

Effects of Deep-Subwavelength Surface Roughness on Fields of Plasmonic Thin Film Based on Lippmann-Schwinger Equation in the Spectral Domain

  • Leung Tsang, Nicholaos Limberopoulos, Kung-Hau Ding, Xudong Li, Philippe Duvelle, Jarrett Vella, Christie Devlin, and John Goldsmith
  • received 09/17/2014; accepted 02/23/2015; posted 02/24/2015; Doc. ID 222770
  • [full text: PDF (1691) KB)]
  • Abstract: In this paper, we consider a line source over a plasmonic thin film with surface roughness. Using layered medium Green’s functions, we derive the Lippmann-Schwinger equation in the spectral domain with scattering potentials. Because of deep-subwavelength surface roughness, the scattering potentials are next approximated by the small height approximation so that the solutions of fields in the spectral domain can be computed readily. Numerical results are illustrated for the surface fields on the rough surface and the fields in the image plane. For periodic roughness, small periods, on the order of 0.1λ, and small heights, on the order of 0.01λ, are used. For the case of random roughness, we choose the correlation length to be much smaller than a wavelength, on the order of 0.1λ, and height on the order of 0.01λ. The results of the fields on the rough surface in the spectral domain show that subwavelength roughness creates fields with wave vector components that are many times larger than the free space wavenumber ( 10k or larger ). In the spatial domain, the imaging is enhanced by the deep-subwavelength roughness. Results of the small roughness approximation are in good agreement with that of exact potential and that of the method of moments (MoM).

Keywords (OCIS):

  • (220.3630) Optical design and fabrication : Lenses
  • (240.0240) Optics at surfaces : Optics at surfaces
  • (240.0310) Optics at surfaces : Thin films
  • (240.5770) Optics at surfaces : Roughness
  • (240.6680) Optics at surfaces : Surface plasmons
  • (250.5403) Optoelectronics : Plasmonics

Optical nanoantenna based on asymmetric nanohole pair milled in an opaque gold film

  • Mohsen Janipour and Mohammad Azim Karami
  • received 01/19/2015; accepted 02/23/2015; posted 02/23/2015; Doc. ID 232591
  • [full text: PDF (1397) KB)]
  • Abstract: The optical interaction of two asymmetric nanoholes milled in an opaque gold film through surface plasmon polariton (SPP) propagation is investigated. It is shown that the interaction between the nanoholes, strongly depends on the polarization direction of the incident light. Moreover, it is found that the asymmetric nanohole pair can direct the incident light. The directivity of the nanohole pair depends on the separation distance between the nanoholes, which leads to in-phase and anti-phase interaction of the nanoholes. For short distances, (comparable to the SPP wavelength launched by each nanohole) the interaction can be considerable, in contrast to the high separation distance, which leads to weaker interaction between the nanoholes. The interaction mechanism of the nanoholes has been supported by magnetic-coupled dipole approximation method.

Keywords (OCIS):

  • (050.1220) Diffraction and gratings : Apertures
  • (250.5403) Optoelectronics : Plasmonics
  • (310.6628) Thin films : Subwavelength structures, nanostructures

Quantum dot based single photon avalanche detector for mid infrared applications

  • Mahdi Zavvari
  • received 06/12/2014; accepted 02/23/2015; posted 02/23/2015; Doc. ID 213956
  • [full text: PDF (415) KB)]
  • Abstract: A single photon detector is presented with quantum dot layers in its absorption region. The proposed detector is a three-terminal device in which a quantum dot infrared photodetector (QDIP) is integrated with an avalanche multiplication region through a tunneling barrier and the applied bias of each region can be controlled separately. The mid-infrared single photons (λ=3~5μm) can be absorbed in QDIP and drifted to avalanche region to trigger an avalanche and generate an output pulse. Since the absorption region consists of doped quantum dot layers, it is expected to have higher orders of dark count. However by separate controlling the bias and keeping the electric field of absorption region low, the dark current of this region can be reduced. Our simulations predict a single photon detection efficiency (SPQE) about 0.7 at T=50K for proposed detector. For higher temperatures dark count rate increases and results in reduced SPQE. To improve the operation temperature, resonant tunneling barriers (RTB) are included in absorption region to inhibit the thermally excited electrons from contribution in dark current generation. Our results show that the SPQE for RTB based device is about 0.65 at T=77K which is approximately equivalent to the SPQE of the device without RTB at T=50K.

Keywords (OCIS):

  • (040.3060) Detectors : Infrared
  • (040.5160) Detectors : Photodetectors
  • (040.5570) Detectors : Quantum detectors
  • (230.5590) Optical devices : Quantum-well, -wire and -dot devices
  • (040.1345) Detectors : Avalanche photodiodes (APDs)

Gap solitons attached to a gapless layer

  • Thawatchai Mayteevarunyoo and Boris Malomed
  • received 01/28/2015; accepted 02/22/2015; posted 02/23/2015; Doc. ID 233495
  • [full text: PDF (1091) KB)]
  • Abstract: We consider linear and nonlinear modes pinned to a grating-free layer placed between two symmetric or asymmetric semi-infinite Bragg gratings (BGs), with a possible phase shift between them, in a medium with the uniform Kerr nonlinearity. The asymmetry is defined by a difference between widths of the bandgap in the two BGs. In the linear system, exact defect modes (DMs) are found. Composite pinned gap solitons are found, analytically and numerically, in the full nonlinear model. In the asymmetric system, existence boundaries for the DMs and gap solitons, due to the competition between attraction to the gapless layer and repulsion from the reflectivity step, are obtained in an analytical form. Stability boundaries for solitons in the asymmetric system are identified by means of direct simulations. Collisions of moving BG solitons with the gapless layer are studied too.

Keywords (OCIS):

  • (190.5530) Nonlinear optics : Pulse propagation and temporal solitons
  • (060.3735) Fiber optics and optical communications : Fiber Bragg gratings
  • (160.5293) Materials : Photonic bandgap materials

PROBABILITY DENSITY FUNCTION OF THE RATE OF ENERGY TRANSFER FROM LUMINESCENT IONS TO A RANDOM DISTRIBUTION OF TRAPS IN THE STATIC LIMIT

  • Jean-Francois Bisson
  • received 12/08/2014; accepted 02/22/2015; posted 02/23/2015; Doc. ID 229080
  • [full text: PDF (745) KB)]
  • Abstract: The transfer of excitation of luminescent ions to a random distribution of traps is revisited in the static limit, with the emphasis on the probability density function (pdf) of the decay rate. Knowledge of the pdf is advantageous for situations where the time evolution of an individual ion’s excited state differs from an exponential decay or when no closed-form solution for the ensemble average exists, because it allows one to reconstruct an ensemble average from the knowledge of the behavior of a single class of ions. A model with dipole-dipole interactions with no minimum distance leads, in the continuum limit, to an inverse gamma (IG) probability distribution with shape parameter α=1/2 which has infinite moments. With a minimum nearest trap distance, close-form solutions of the moments of the actual pdf are well matched with those of a smoothly truncated IG distribution. Experimental luminescence decay obtained on Yb3+-doped Y2O3 thin films displaying non exponential decay behavior agrees well with the proposed model.

Keywords (OCIS):

  • (000.5490) General : Probability theory, stochastic processes, and statistics
  • (140.3380) Lasers and laser optics : Laser materials
  • (140.5680) Lasers and laser optics : Rare earth and transition metal solid-state lasers
  • (160.3380) Materials : Laser materials
  • (160.5690) Materials : Rare-earth-doped materials
  • (140.3615) Lasers and laser optics : Lasers, ytterbium

Tackling the Limits of Optical Fiber Links

  • Paul-Eric Pottie, Fabio Stefani, Olivier Lopez, Anthony Bercy, Won-Kyu Lee, Christian Chardonnet, GIORGIO SANTARELLI, and Anne Amy-Klein
  • received 12/04/2014; accepted 02/21/2015; posted 02/23/2015; Doc. ID 228924
  • [full text: PDF (1534) KB)]
  • Abstract: We theoretically and experimentally investigate relevant noise processes arising in optical fiber links, which fundamentally limit their relative stability. We derive the unsuppressed delay noise for three configurations of optical links : two-way method, Sagnac interferometry, and actively compensated link, respectively designed for frequency comparison, rotation sensing, and frequency transfer. We also consider an alternative two-way setup allowing real-time frequency comparison and demonstrate its effectiveness on a proof-of-principle experiment with a 25-km fiber spool. For these three configurations, we analyze the noise arising from uncommon fiber paths in the interferometric ensemble and design optimized interferometers. We demonstrate interferometers with very low temperature sensitivity of respectively -2.2, -0.03 and 1 fs/K. We use one of these optimized interferometers on a long haul compensated fiber link of 540 km. We obtain a relative frequency stability of 3 1E-20 after 10000 s of integration time.

Keywords (OCIS):

  • (060.2360) Fiber optics and optical communications : Fiber optics links and subsystems
  • (120.0120) Instrumentation, measurement, and metrology : Instrumentation, measurement, and metrology
  • (120.5050) Instrumentation, measurement, and metrology : Phase measurement
  • (120.5790) Instrumentation, measurement, and metrology : Sagnac effect
  • (350.4600) Other areas of optics : Optical engineering

Hartman effect in a doped one dimensional photonic crystal at normal and oblique incidences

  • Mostafa Sahrai, Hamed Sattari, Jafar Poursamad Bonab, and Roghayeh Aghaei
  • received 12/10/2014; accepted 02/20/2015; posted 02/23/2015; Doc. ID 228987
  • [full text: PDF (4002) KB)]
  • Abstract: Hartman effect in one dimensional photonic crystal containing a defect layer doped by three level ladder type atoms is theoretically investigated for normal and oblique incidences. Influence of the relative phase of applied fields and the intensity of coupling field on Hartman effect is then discussed. We find that Hartman effect can be switched from positive to negative (or vic versa) just by adjusting the relative phase of applied fields, the intensity of coupling field and the proper choice of incident angle.

Keywords (OCIS):

  • (160.4760) Materials : Optical properties
  • (240.7040) Optics at surfaces : Tunneling
  • (270.1670) Quantum optics : Coherent optical effects
  • (160.5298) Materials : Photonic crystals

Electromagnetic trapping of chiral molecules: Orientational effects of the irradiating beam

  • David Bradshaw and David Andrews
  • received 12/17/2014; accepted 02/20/2015; posted 02/20/2015; Doc. ID 231037
  • [full text: PDF (445) KB)]
  • Abstract: The photonic interaction generally responsible for the electromagnetic trapping of molecules is forward-Rayleigh scattering, a process that is mediated by transition electric dipoles connecting the ground electronic state and virtual excited states. Higher order electric and magnetic multipole contributions to the scattering amplitude are usually negligible. However, on consideration of chiral discrimination effects (in which an input light of left-handed circular polarization can present different observables compared to right-handed polarization, or molecules of opposite enantiomeric form respond differently to a set circular polarization), the mechanism must be extended to specifically accommodate transition magnetic dipoles. Moreover, it is important to account for the fact that chiral molecules are necessarily non-spherical, so that their interactions with a laser beam will have an orientational dependence. Using quantum electrodynamics, this article quantifies the extent of the energetic discrimination that arises when chiral molecules are optically trapped, placing particular emphasis on the orientational effects of the trapping beam. An in-depth description of the intricate ensemble-weighted method used to incorporate the latter is presented. It is thus shown that, when a mixture of molecular enantiomers is irradiated by a continuous beam of circularly polarized light, a difference arises in the relative rates of migration of each enantiomer in and out of the most intense regions of the beam. In consequence, optical trapping can be used as a means of achieving enantiomer separation.

Keywords (OCIS):

  • (020.7010) Atomic and molecular physics : Laser trapping
  • (260.2110) Physical optics : Electromagnetic optics
  • (270.5580) Quantum optics : Quantum electrodynamics
  • (160.1585) Materials : Chiral media
  • (290.2558) Scattering : Forward scattering

Hysteresis assisted narrowband resonances in a chain of nonlinear plasmonic arrays

  • Arkadi Chipouline, Nikolay Rosanov, Sergey Fedorov, and Thomas Pertsch
  • received 09/19/2014; accepted 02/20/2015; posted 02/23/2015; Doc. ID 223397
  • [full text: PDF (1178) KB)]
  • Abstract: The plasmonic structures exhibiting narrowband resonances (NBR) are of a great interest for various applications. We propose to use hysteresis behavior in a 1D system of nonlinear nanoresonators in order to achieve the NRB; the nonlinearity is provided by saturation of a two-level quantum system coupled with the nanoresonators (nanolaser/spaser configuration). Quantum Dots (QD) were assumed as quantum systems; their numerical parameters have been adopted for estimations. Role of the loss compensation on the quality of the NBR is shown for below (under compensation) and above threshold (generating spasers) operation modes. Amplitude and phase detection schemes of the prospective experimental realization are compared using the developed model. Possible sensor oriented applications of the proposed system are discussed.

Keywords (OCIS):

  • (140.3290) Lasers and laser optics : Laser arrays
  • (190.0190) Nonlinear optics : Nonlinear optics
  • (190.1450) Nonlinear optics : Bistability

Polarisation and Mutual Coupling Effects in Aluminium Nanoantenna Arrays

  • Neciah Dorh, Martin Cryan, and Jamie Stokes
  • received 12/10/2014; accepted 02/17/2015; posted 02/23/2015; Doc. ID 229021
  • [full text: PDF (2310) KB)]
  • Abstract: This paper studies two arm aluminium dipole nanoantennas in both single and 2 x 2 array configurations. Purcell and Power Enhancement results are shown highlighting the importance of including antenna losses when quantifying antenna performance. Point source excitation in the antenna gap is used and the paper studies the effect of different polarizations of this source with respect to the dipole antenna. The paper then studies the impact of source orientation within the 2 x 2 array and shows strong dependence of resonant wavelength and radiation pattern on the distribution of source orientations in the array.

Keywords (OCIS):

  • (240.6680) Optics at surfaces : Surface plasmons
  • (260.5740) Physical optics : Resonance
  • (260.7190) Physical optics : Ultraviolet
  • (250.5403) Optoelectronics : Plasmonics
  • (310.6628) Thin films : Subwavelength structures, nanostructures
  • (240.5440) Optics at surfaces : Polarization-selective devices

Recurrence for motion of solitons of the Bose-Einstein condensate in a dynamic trap

  • Nikolay Rosanov and Nina Vysotina
  • received 01/07/2015; accepted 02/15/2015; posted 02/18/2015; Doc. ID 231587
  • [full text: PDF (538) KB)]
  • Abstract: We consider, analytically and numerically, the dynamics of an atomic Bose-Einstein condensate soliton bouncing in a magnetic or optical trap between two ideal barriers oscillating harmonically with coinciding frequency and opposite phases. There are zones of parametric instability of soliton central position in the trap for certain ranges of the frequency of barriers’ oscillations. We demonstrate the Fermi-Pasta-Ulam recurrence in the Fermi-Ulam scheme for solitons: the soliton’s deviations from the trap’s center grow and decay quasi-periodically in time. The results allow one to excite and investigate various structures of matter waves in traps and to manipulate their localization and dynamics.

Keywords (OCIS):

  • (020.0020) Atomic and molecular physics : Atomic and molecular physics
  • (020.7010) Atomic and molecular physics : Laser trapping
  • (020.1335) Atomic and molecular physics : Atom optics
  • (020.1475) Atomic and molecular physics : Bose-Einstein condensates

Radiation from Free Electrons in a Laser Focus at 10¹⁸W/cm²: modeling of photon yields and required focal conditions

  • Michael Ware, Justin Peatross, Eric Cunningham, Grayson Tarbox, and Ryan Sandberg
  • received 12/23/2014; accepted 02/13/2015; posted 02/18/2015; Doc. ID 231361
  • [full text: PDF (946) KB)]
  • Abstract: In support of an experiment designed to measure the strength of radiation scattered from low-density free electrons in an intense laser focus, we explore a variety of physical parameters that impact the rate of scattered photons. We employ a classical model to characterize duration of electron exposure to high-intensity laser light in a situation where the electrons are driven by strong ponderomotive gradients. Free electrons are modeled as being donated by low-density helium, which undergoes strong-field ionization early on in the pulse or during a pre pulse. When exposed to relativistic intensities, free electrons experience a Lorentz drift that causes redshifting of the scattered 800 nm light. This redshift can be used as a key signature to discern light scattered from the more intense regions of the focus. We characterize the focal volume of initial positions leading to significant redshifting, given a peak intensity of $2\times10^{18}$~W/cm$^2$. Under this scenario, the beam waist needs to be larger than several wavelengths for a pulse duration of 35~fs. We compute the rate of redshifted scattered photons from an ensemble of electrons distributed throughout the focus and relate the result to the scattered-photon rate of a single electron. We also estimate to what extent the ionization process may produce unwanted light in the redshifted spectral region.

Keywords (OCIS):

  • (000.1600) General : Classical and quantum physics
  • (020.5580) Atomic and molecular physics : Quantum electrodynamics
  • (120.5820) Instrumentation, measurement, and metrology : Scattering measurements
  • (350.5720) Other areas of optics : Relativity

(OCT2015) Storage time of cold Rb atoms in an optical dipole trap formed by a multimode fiber laser

  • Ite Yu, Weilun Hung, Panpan Huang, Feng-Chuan Wu, Hau-Yl Xiao, Martins Bruvelis, and Aigars Ekers
  • received 01/09/2015; accepted 02/12/2015; posted 02/12/2015; Doc. ID 231992
  • [full text: PDF (441) KB)]
  • Abstract: We systematically studied the storage time of Rb-87 atoms in an optical dipole trap (ODT) formed by a multimode fiber laser. Storage time is an important parameter in cold atom experiments. If atoms are prepared in the hyperfine state |F=2>, hyperfine-state-changing collisions can transfer these atoms from |F=2> to |F=1>, whereby the released kinetic energy leads to considerable trap loss. In most ODT experiments, atoms are prepared in the hyperfine state |F=1>. However, two-photon Raman transitions induced by high-power multimode fiber lasers can optically pump these atoms from |F=1> to |F=2> and the following hyperfine-state-changing collision results in the trap loss. In this work, our experimental data indicate that both the two-photon Raman transition and the hyperfine-state-changing collision can be inhibited if the atoms are prepared in the single Zeeman sublevel of |F=2,m=2> (or |F=2,m=-2>) and an auxiliary magnetic field is applied.

Keywords (OCIS):

  • (020.2070) Atomic and molecular physics : Effects of collisions
  • (020.7010) Atomic and molecular physics : Laser trapping
  • (190.5650) Nonlinear optics : Raman effect

Computational toolbox for optical tweezers in geometrical optics

  • Agnese Callegari, Giovanni Volpe, Mite Mijalkov, and Burak Gokoz
  • received 01/09/2015; accepted 02/12/2015; posted 02/19/2015; Doc. ID 232002
  • [full text: PDF (865) KB)]
  • Abstract: Optical tweezers have found widespread application in many fields, from physics to biology. Here, we explain in detail how optical forces and torques can be described within the geometrical optics approximation and we show that this approximation provides reliable results in agreement with experiments for particles whose characteristic dimensions are larger than the wavelength of the trapping light. Furthermore, we provide an object-oriented software package implemented in MatLab for the calculation of optical forces and torques in the geometrical optics regime: \texttt{OTGO - Optical Tweezers in Geometrical Optics}. We provide all source codes for \texttt{OTGO} as well as the documentation and code examples -- e.g., standard optical tweezers, optical tweezers with elongated particle, windmill effect, Kramers transitions between two optical traps -- necessary to enable users to effectively employ it in their research.

Keywords (OCIS):

  • (140.7010) Lasers and laser optics : Laser trapping
  • (080.1753) Geometric optics : Computation methods
  • (350.4855) Other areas of optics : Optical tweezers or optical manipulation

January


(OCT2014) Optical collimation of an atomic beam using a white light molasses

  • Rohan Glover and Thierry Bastin
  • received 11/04/2014; accepted 01/02/2015; posted 01/16/2015; Doc. ID 226250
  • [full text: PDF (1739) KB)]
  • Abstract: We investigate optical collimation of an atomic beam using a spectrally broadened `white light molasses'. We compare this technique with the standard technique using an atomic collimator and find that under certain conditions the white light molasses is preferable. Specifically, a white light molasses is suitable for atomic beams with relatively low mean velocities and broad velocity distributions, for example a beam effusing from a cryogenically cooled reservoir. This result is demonstrated by numerically modeling the atomic trajectories of argon atoms effusing from a cryogenically cooled reservoir. We find that given sufficient power a white light molasses captures a larger fraction of atoms when compared to an atomic collimator and the velocity distribution of the resulting beam is shifted towards slower velocities. Further, an optical molasses is geometrically relatively simple compared to an atomic collimator and therefore the complexity of the in vacuum optical arrangement can be significantly reduced.

Keywords (OCIS):

  • (000.2170) General : Equipment and techniques
  • (020.0020) Atomic and molecular physics : Atomic and molecular physics
  • (020.3320) Atomic and molecular physics : Laser cooling

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