We report the compression of intense, carrier-envelope phase stable mid-IR pulses down to few-cycle duration using an optical filament. A filament in xenon gas is formed by using self-phase stabilized 330 J 55 fs pulses at 2 m produced via difference-frequency generation in a Ti:sapphire-pumped optical parametric amplifier. The ultrabroadband 2 m carrier-wavelength output is self-compressed below 3 optical cycles and has a 270 J pulse energy. The self-locked phase offset of the 2 m difference-frequency field is preserved after filamentation. This is to our knowledge the first experimental realization of pulse compression in optical filaments at mid-IR wavelengths ͑Ͼ0.8 m͒. © 2007 Optical Society of America OCIS codes: 190.5530, 320.5520. Progress in strong-field physics has been accelerated by the development of lasers operating near the 0.8 m wavelength that feature high peak power, few-cycle duration, and reliable control over the carrier-envelope phase 1 (CEP). Furthermore, the fundamental scaling laws 2,3 governing the intense laseratom interaction suggest that the advancement of longer-wavelength mid-IR laser sources capable of similar optical quality will have a major impact in strong-field physics. The most compelling examples include the generation of shorter attosecond x-ray bursts and the rescattering of electrons at kilovolt energies. [3][4][5] A recently demonstrated 80 J, 2 m prototype system 6 based on optical parametric chirped-pulse amplification via difference-frequency generation defines a standard for future development of longwavelength drivers. However, the optical parametric chirped-pulse amplification architecture is faced with important technical challenges, 7 such as the need for specific pump laser design and unwanted generation of parasitic fluorescence underlying the primary pulse for high parametric gain configurations. 6 Currently, femtosecond optical parametric amplifiers (OPAs) pumped by multimillijoule Ti:sapphire chirped-pulse amplification systems can deliver multicycle pulses in the mid-IR with sufficient peak power to investigate the efficacy of the nonlinear pulse compression techniques developed at shorter wavelengths. In particular, optical filaments formed in a noble gas by intense 0.8 m pulses have demonstrated pulse compression down to the few-cycle regime with excellent beam stability and spatial mode quality. 8This Letter demonstrates, for the first time to our knowledge, the self-compression in an optical filament of high-peak-power mid-IR pulses derived by difference-frequency generation in a Ti:sapphire pumped OPA. This efficient scheme produces fluorescence-free, sub-3 optical cycle pulses near the 2 m wavelength with 270 J energy at a 1 kHz repetition rate. The intense 2 m field carries a constant CEP offset, thus making it an attractive longwavelength driver for benchmark strong-field experiments.A schematic of the experimental setup is shown in Fig. 1. High-peak-power multicycle mid-IR pulses are produced in a slightly modified traveling-wave OPA (TOPAS, L...

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We report on the generation and measurement of a >10 8 contrast ratio between main pulse and amplified spontaneous emission (ASE) from a relativistic kHz chirped-pulse amplified laser. We have enhanced the ASE contrast ratio as much as >400 times by employing a pulse cleaner composed of a µJ preamplifier and a saturable absorber. A third-order cross-correlator with a dynamic range of >10 9 and a scanning range of up to 4 ns has been developed for the contrast measurement. Detailed analysis of the cross-correlation trace shows that the random noise of spectral phase generates 20-ps pedestal structure starting from 10 −6 level of the main pulse.

Isolated attosecond pulses and electron buncht-s can be efficiently yeiif rated in the interaction of intense lasers with pliismn in the confined voliiine of the }? regime. Scaling with intensitj' is found m improve pulse hre\ ity and focusabilit>-greatly vvhile the efficiency of the attoseeond pulse generation continues to remain high. Practical consideration of the tools needed to generate such pulses indicates that sueh interactions are surprisingly accessible. We mention some introductory experiments whereby we may verify the theoretical predictions of this new class of attosecond pulses. This techni(.|ue may enable us to reach the Schwinger intensity 10^''Wcm~ .

We present a design for a continuous-wave (CW) atom laser on a chip and describe the process used to fabricate the device. Our design aims to integrate quadrupole magnetic guiding of ground state 87 Rb atoms with continuous surface adsorption evaporative cooling to create a continuous Bose-Einstein condensate; out-coupled atoms from the condensate should realize a CW atom laser. We choose a geometry with three wires embedded in a spiral pattern in a silicon subtrate. The guide features an integrated solenoid to mitigate spin-flip losses and provide a tailored longitudinal magnetic field. Our design also includes multiple options for atom interferometry: accomodations are in place for laser-generated atom Fabry-Perot and Mach-Zehnder interferometers, and a pair of atomic beam X-splitters is incorporated for an all-magnetic atom Mach-Zehnder setup. We demonstrate the techniques necessary to fabricate our device using existing micro-and nano-scale fabrication equipment, and discuss future options for modified designs and fabrication processes.

We describe an all-reflective interferometric autocorrelator designed to measure ultrabroadband optical pulses in the UV through IR spectral regions. By carefully choosing the device geometry we are able to obtain approximations for the nonlinear autocorrelation functions that reduce computation times to values acceptable for use in iterative pulse reconstruction schemes. We describe the optical design, autocorrelation functions, and present proof-of-principle experimental results measuring 20.6 fs pulses with a transform limit of 9.6 fs.

We study the guiding of 87 Rb 59D 5/2 Rydberg atoms in a linear, high-gradient, two-wire magnetic guide. Time delayed microwave ionization and ion detection are used to probe the Rydberg atom motion. We observe guiding of Rydberg atoms over a period of 5 ms following excitation. The decay time of the guided atom signal is about five times that of the initial state. We attribute the lifetime increase to an initial phase of l-changing collisions and thermally induced RydbergRydberg transitions. Detailed simulations of Rydberg atom guiding reproduce most experimental observations and offer insight into the internal-state evolution.There has been a recent surge of interest in cold Rydberg atoms in a linear trapping geometry. Such systems present the possibility of creating one-dimensional spin chains by exciting atoms into high-lying Rydberg levels, which interact strongly due to their large dipole moments [1][2][3]. Rydberg crystals, which have been proposed in a frozen atomic gas using the Rydberg excitation blockade effect, may be an interesting application within a linear structure [4]. Entangled Rydberg atoms prepared in a linear guiding geometry could act as a shuttle for quantum information [5,6]. A one-dimensional trap or guide for Rydberg atoms could be used to further these types of research. Cold Rydberg atoms have been experimentally trapped using magnetic [7], electrostatic [8], and light fields [9]. Conservative trapping of Rydberg atoms in magnetic atom guides has been theoretically investigated in [10][11][12]. Theoretical calculations also indicate the possibility of stationary Rydberg atoms confined in magnetic traps and magnetoelectric traps [13][14][15]. These systems would allow one to study Rydberg gases in a one-dimensional geometry. The Rydberg-Rydberg interaction properties in such a system have been theoretically studied in [16]. In the present paper we report the first guiding of Rydberg atoms in a linear magnetic guide.Two parallel wires carrying equal currents guide cold atoms in low magnetic field seeking states along a linear guiding channel located between the guide wires, where the magnetic field approaches zero. Briefly, our 1.5 m long linear guide [17,18] operates with a magnetic field gradient of ∼1.5 kG/cm, which tightly confines a beam of 87 Rb atoms (prepared in the |F = 1, m F = −1 level of the 5S 1/2 ground-state) in the guiding channel. The forward velocity of the guided atoms is adjusted to ≈1 m/s. The ground state atoms have transverse and longitudinal temperatures of T x,y ≈ 400 µK and T z ≈ 1 mK, respectively. An excitation and detection region for Rydberg atoms is located 85 cm down the guide, illustrated in Fig. 1. We use a three-step Rydberg atom excitation process. A pulsed 780 nm beam (duration 10 µs) pumps the atoms from 5S 1/2 |F = 1, m F = −1 to F = 2. A second pulsed 780 nm beam (duration 5 µs) subsequently drives the atoms on the cycling transition into 5P 3/2 F ′ = 3. The atoms are excited from the 5P 3/2 level to the 59D 5/2 Rydberg level with a tunable, cont...

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