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H
Hsu, C-Y, Wang Y-S, Chen J-M, Huang F-C, Ke Y-T, Huang EK, Hung W, Chao K-L, Hsaio S-S, Chen Y-H, Chuu C-S, Chen Y-C, Chen Y-F, Yu IA.  2021.  Generation of sub-MHz and spectrally-bright biphotons from hot atomic vapors with a phase mis-match-free scheme. Optics Express. 29, 4632(2021)
Huang, SJ, Hsu YT, Lee H, Chen YC, Volosniev AG, Zinner NT, Wang DW.  2012.  Field-induced long-lived supermolecules, May 7. Physical Review A. 85 AbstractWebsite

We demonstrate that the long-lived bound states (supermolecules) can exist in the dilute limit when we tune the shape of the effective potential between polar molecules by an external microwave field. Binding energies, average sizes, and phase diagrams for both s-orbital (bosons) and p-orbital (fermions) dimers are studied, together with bosonic trimer states. We explicitly show that the nonadiabatic transition rate can be easily tuned small for such ground-state supermolecules, so that the system can be stable from collapse even near the associated potential resonance. Our results, therefore, suggest a feasible cold molecule system to investigate novel few-body and many-body physics (for example, the p-wave BCS-Bose-Einstein-condensate crossover for fermions and the paired condensate for bosons) that cannot be easily accessed in single species atomic gases.

J
Jen, HH, Lin G-D, Chen Y-C.  2022.  Resonant dipole-dipole interactions in electromagnetically induced transparency.. PHYSICAL REVIEW A. 105, 063711(2022)
Jen, H-H, Lin G-D, Chen Y-C.  2022.  Resonant dipole-dipole interactions in electromagnetically induced transparency. Phys. Rev. A. 105, 063711(2022)
Jen, HH, Chen YC.  2016.  Spectral shaping of cascade emissions from multiplexed cold atomic ensembles. Physical Review A. 93 :013811.
Jen, HH, Chang M-S, Chen Y-C.  2018.  Cooperative light scattering from helical-phase-imprinted atomic rings. Scientific Reports. 8(9570)
Jen, HH, Chang M-S, Lin G-D, Chen YC.  2020.  Subradiance dynamics in a singly excited chirally coupled atomic chain. PHYSICAL REVIEW A. 101(023830)Link
Jen, HH, Chang MS, Chen YC.  2016.  Cooperative single-photon subradiant states. Physical Review A. 94(1):013803.
Jen, HH, Chang M-S, Lin G-D, Chen Y-C.  2019.  Subradiance dynamics in a singly-excited chiral-coupled atomic chain. arXiv:1905.00558.
K
Killian, TC, Chen YC, Gupta P, Laha S, Martinez YN, Mickelson PG, Nagel SB, Saenz AD, Simien CE.  2005.  Absorption imaging and spectroscopy of ultracold neutral plasmas, Jan 28. Journal of Physics B-Atomic Molecular and Optical Physics. 38:S351-S362. AbstractWebsite

Absorption imaging and spectroscopy can probe the dynamics of an ultracold neutral plasma during the first few microseconds after its creation. Quantitative analysis of the data, however, is complicated by the inhomogeneous density distribution, expansion of the plasma and possible lack of global thermal equilibrium for the ions. In this paper, we describe methods for addressing these issues. Using simple assumptions about the underlying temperature distribution and ion motion, the Doppler-broadened absorption spectrum obtained from plasma images can be related to the average temperature in the plasma.

Killian, TC, Chen YC, Gupta P, Laha S, Martinez YN, Mickelson PG, Nagel SB, Saenz AD, Simien CE.  2005.  Ultracold neutral plasmas, May. Plasma Physics and Controlled Fusion. 47:A297-A306. AbstractWebsite

Ultracold neutral plasmas are formed by photo-ionizing laser-cooled atoms near the ionization threshold. Through the application of atomic physics techniques and diagnostics, these experiments stretch the boundaries of traditional neutral plasma physics. The electron temperature in these plasmas ranges from 1 to 1000 K and the ion temperature is around 1 K. The density can approach 10(11) cm(-3). Fundamental interest stems from the possibility of creating strongly coupled plasmas, but recombination, collective modes, and thermalization in these systems have also been studied. Optical absorption images of a strontium plasma, using the Sr+ S-2(1/2) -> P-2(1/2) transition at 422 mn, depict the density profile of the plasma, and probe kinetics on a 50 ns time-scale. The Doppler-broadened ion absorption spectrum measures the ion velocity distribution, which gives an accurate measure of the ion dynamics in the first microsecond after photo-ionization.

Kim, B, Chen K-T, Hsiao S-S, Wang S-Y, Li K-B, Ruseckas J, Juzeliūnas G, Kirova T, Auzinsh M, Chen Y-C, Chen Y-F, Yu IA.  2021.  A weakly-interacting many-body system of Rydberg polaritons based on electromagnetically in-duced transparency. Commun. Phys. 4:101(2021)
L
Laha, S, Chen YC, Gupta P, Simien CE, Martinez YN, Mickelson PG, Nagel SB, Killian TC.  2006.  Kinetic energy oscillations in annular regions of ultracold neutral plasmas, Oct. European Physical Journal D. 40:51-56., Number 1 AbstractWebsite

A study of ion equilibration in annular regions of ultracold strontium plasmas is reported. Plasmas are formed by photoionizing laser-cooled atoms with a pulsed dye laser. The experimental probe is spatially-resolved absorption spectroscopy using the S-2(1/2)-P-2(1/2) transition of the Sr+ ion. The kinetic energy of the ions is calculated from the Doppler broadening of the spectrum, and it displays clear oscillations during the first microsecond after plasma formation. The oscillations, which are a characteristic of strong coulomb coupling, are fit with a simple phenomenological model incorporating damping and density variation in the plasma.

Lee, C-Y, Wu B-H, Wang G, Chen Y-F, Chen Y-C, Yu IA.  2016.  High conversion efficiency in resonant four-wave mixing processes. Optics Express. 24 :1008-1016.
Lin, C-C, Wu M-C, Shiau B-W, Chen Y-H, Yu IA, Chen Y-F, Chen Y-C.  2012.  Enhanced all-optical switching with double slow light pulses, Dec 28. Physical Review A. 86 AbstractWebsite
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Lin, PY, Shiau BW, Hsiao YF, Chen YC.  2011.  Creation of arbitrary spectra with an acousto-optic modulator and an injection-locked diode laser, Aug. Review of Scientific Instruments. 82:6., Number 8 AbstractWebsite

We use a double-passed acousto-optic modulator (AOM), driven by an arbitrary waveform generator to produce multiple frequency components for a laser with arbitrary frequency spacings. A programmed sequence containing various sections of radio-frequency sinusoidal signal at different frequency is applied to drive the AOM. The diffracted light is used to injection-lock a diode laser. The combined techniques allow us to generate the multi-line spectra for the diode laser with arbitrary frequency spacings in the range of 100 MHz at a relatively high output power of 80 mW and a small power variation of 2%. Such a light source can be used in the application for laser cooling of molecules. (C) 2011 American Institute of Physics. [doi:10.1063/1.3626903]

Lin, YW, Chou HC, Dwivedi PP, Chen YC, Yu IA.  2008.  Using a pair of rectangular coils in the MOT for the production of cold atom clouds with large optical density, Mar. Optics Express. 16:3753-3761., Number 6 AbstractWebsite

We demonstrate a simple method to increase the optical density (OD) of cold atom clouds produced by a magneto-optical trap (MOT). A pair of rectangular anti-Helmholtz coils is used in the MOT to generate the magnetic field that produces the cigar-shaped atom cloud. With 7.2 x 10(8) Rb-87 atoms in the cigar-type MOT, we achieve an OD of 32 as determined by the slow light measurement and this OD is large enough such that the atom cloud can almost contain the entire Gaussian light pulse. Compared to the conventional MOT under the same trapping conditions, the OD is increased by about 2.7 folds by this simple method. In another MOT setup of the cigar-shaped Cs atom cloud, we achieve an OD of 105 as determined by the absorption spectrum of the |6S(1/2), F = 4 > ->| 6P(3/2), F ' = 5 > transition. (C) 2008 Optical Society of America

Liu, Z-Y, Chen Y-H, Chen Y-C, Lo H-Y, Tsai P-J, Yu IA, Chen Y-C, Chen Y-F.  2016.  Large Cross-Phase Modulations at the Few-Photon Level. Phys. Rev. Lett. 117(203601)
Lo, HY, Chen YC, Su PC, Chen HC, Chen JX, Yu IA, Chen YF.  2011.  Electromagnetically-induced-transparency-based cross-phase-modulation at attojoule levels, Apr. Physical Review A. 83:4., Number 4 AbstractWebsite

We report the experimental demonstration of electromagnetically-induced-transparency-based cross-phase-modulation at attojoule or, equivalently, few-hundred-photon levels. A phase shift of 0.005 rad of a probe pulse modulated by a signal pulse with an energy of similar to 100 aJ, equivalent to similar to 400 photons, was observed in a four-level system of cold (87)Rb atoms.

M
Mickelson, PG, Martinez YN, Saenz AD, Nagel SB, Chen YC, Killian TC, Pellegrini P, Cote R.  2005.  Spectroscopic determination of the s-wave scattering lengths of Sr-86 and Sr-88, Nov 25. Physical Review Letters. 95 AbstractWebsite

We report the use of photoassociative spectroscopy to determine the ground-state s-wave scattering lengths for the main bosonic isotopes of strontium, Sr-86 and Sr-88. Photoassociative transitions are driven with a laser red detuned by up to 1400 GHz from the S-1(0)-P-1(1) atomic resonance at 461 nm. A minimum in the transition amplitude for Sr-86 at -494 +/- 5 GHz allows us to determine the scattering lengths 610a(0)< a(86)< 2300a(0) for Sr-86 and a much smaller value of -1a(0)< a(88)< 13a(0) for Sr-88.

N
Nagel, SB, Mickelson PG, Saenz AD, Martinez YN, Chen YC, Killian TC, Pellegrini P, Cote R.  2005.  Photoassociative spectroscopy at long range in ultracold strontium, Mar 4. Physical Review Letters. 94 AbstractWebsite

We report photoassociative spectroscopy of Sr-88(2) in a magneto-optical trap operating on the S-1(0)-->P-3(1) intercombination line at 689 nm. Photoassociative transitions are driven with a laser red detuned by 600-2400 MHz from the S-1(0)-->P-1(1) atomic resonance at 461 nm. Photoassociation takes place at extremely large internuclear separation, and the photoassociative spectrum is strongly affected by relativistic retardation. A fit of the transition frequencies determines the P-1(1) atomic lifetime (tau=5.22+/-0.03 ns) and resolves a discrepancy between experiment and recent theoretical calculations.

S
Shiau, BW, Wu MC, Lin CC, Chen YC.  2011.  Low-Light-Level Cross-Phase Modulation with Double Slow Light Pulses, May. Physical Review Letters. 106:4., Number 19 AbstractWebsite

We report on the first experimental demonstration of low-light-level cross-phase modulation (XPM) with double slow light pulses based on the double electromagnetically induced transparency (EIT) in cold cesium atoms. The double EIT is implemented with two control fields and two weak fields that drive populations prepared in the two doubly spin-polarized states. Group velocity matching can be obtained by tuning the intensity of either of the control fields. The XPM is based on the asymmetric M-type five-level system formed by the two sets of EIT. Enhancement in the XPM by group velocity matching is observed. Our work advances studies of low-light-level nonlinear optics based on double slow light pulses.

Simien, CE, Chen YC, Gupta P, Laha S, Martinez YN, Mickelson PG, Nagel SB, Killian TC.  2005.  Absorption imaging of ultracold neutral plasmas, Apr. Ieee Transactions on Plasma Science. 33:540-541. AbstractWebsite

We report optical absorption imaging of ultracold neutral plasmas. Imaging allows direct observation of the ion density profile and expansion of the plasma. The frequency dependence of the plasma's optical depth gives the ion absorption spectrum, which is broadened by the ion motion. We use the spectral width to monitor ion equilibration in the first 250 ns after plasma formation. On a microsecond time scale, we observe the radial acceleration of ions resulting from pressure exerted by the trapped electron gas.

Simien, CE, Chen YC, Gupta P, Laha S, Martinez YN, Mickelson PG, Nagel SB, Killian TC.  2004.  Using absorption imaging to study ion dynamics in an ultracold neutral plasma, Apr. Physical Review Letters. 92:4., Number 14 AbstractWebsite

We report optical absorption imaging of ultracold neutral strontium plasmas. The ion absorption spectrum determined from the images is Doppler broadened and thus provides a quantitative measure of the ion kinetic energy. For the particular plasma conditions studied, ions heat rapidly as they equilibrate during the first 250 ns after plasma formation. Equilibration leaves ions on the border between the weakly coupled gaseous and strongly coupled liquid states. On a longer time scale of microseconds, pressure exerted by the trapped electron gas accelerates the ions radially.

T
Tsai, P-J, Chen Y-C.  2018.  Ultrabright, narrow-band photon-pair source for atomic quantum memories. Quantum Sci. Technol. 3 (034005)