Showing papers by "Jörg Schmiedmayer published in 1994"

Magnetic coherences in atom interferometry

Abstract: We have used a separated beam atom interferometer to investigate magnetically-induced phase shifts of the different magnetic substates of the sodium ground state. We have observed periodic rephasing of the 8 independent magnetic substates present in an unpolarized sodium beam as the differential magnetic field is increased on opposite sides of the interferometer. We have also demonstrated that two phase shifts with similar velocity dependences can be used to cancel each other, creating an interference pattern from one magnetic substate although an unpolarized beam is sent into the interferometer. Finally we discuss some applications of these techniques.

Interferometry with atoms and molecules

Abstract: Three 0.2-μm period diffraction gratings were used to realize an interferometer for atoms and molecules1 that passes the interfering components of the deBroglie wave on opposite sides of a stretched metal foil positioned between two side plates. The foil was 10 cm long and 10 μ.m. thick, and a gas sample of density −2 × 1012 atoms/ cm3 could be introduced on one side of the foil only.

Interferometry with atoms and molecules

Abstract: and detected after the germanium filter with a liquid-N2 cooled photoconductive HgCdTe detector. The three diode lasers used in this experiment were unmodified commercial devices operating at 671 nm, 690 nm, and 808 nm. Each was operated in a single longitudinal mode. By varying the temperature and the current of the diodes, their emission wavelength could be tuned over about 2 nm. The collimated diode laser beam was converted to a beam dimension of approximately 5 mm by using an anamorphic prism pair. A3: 1 telescope transformed the diode laser beam size to a dimension comparable to that of the Ti:A1203 laser. The diode laser output had a polarization ratio of -100: I; the appropriate polarization direction for type I phase-matching was chosen by proper mounting of the diodes. For a signal and pump wavelength of 808.3 nm ri:A1203 laser) and 690.3 nm (Toshiba TOLD 9140(s) diode laser), respectively, an idler wavelength of 4.73pm was detected. For 1 W of Ti : A1,0, laserpower and 12.1 mW of diode laser power, a DFG power of up to 1.4 pW was measured. The phase-matching bandwidth of the diode/Ti:AI,O, pump laser configuration was observed to be as large as 600 GHz. This is much larger than thephase-matching bandwidth of about 30 GHz observed for the dye/Ti:A120, pump laser configuration.’ The highresolution capability of this novel spectroscopic source was demonstrated by obtaining a Doppler-limited CO absorption spectrum around 2119 cm-’ using a 20-cm absorption cell and about 10 Torr of CO pressure. In this case the diode laser wavelength was fixed, and the infrared wavelength was varied by tuning the Ti : A120, laser. One way to increase the DFG output power to a level that is useful for spectroscopic applications is the use of optical semiconductor amplifiers to boost the power output of the single-mode diode lasers. Significant progress has been made in obtaining diffraction-limited coherent radiation from high-power broadarea diode amplifiers. We demonstrated difference-frequency mixing of a high power GaAlAs tapered traveling-wave semiconductor amplifie3 with a cw Ti:A1,0, laser in a 45-mm long AgGaS, crystal cut for type I noncritical phase-matching at room temperature. The master laser was an index-guided diode laser emitting up to 130 mW in a single-longitudinal mode around 860 nm with a less than 20-MHz linewidth. With 100 mW of master laser power incident on the amplifier, 38 mW was coupled into the amplifier. The pump wave was provided by a Ti : Al20, ring laser operated at 715 nm. Both beams were overlapped using a polarizing beam splitter and focused into the 45mm-long AgGaS, crystal using a 30-cmfocal-length lens. The beam waists were set to -33 pm in both vertical and horizontal planes, close to optimum focusing. Phase-matching was found to occur at a wavelength of 714.50 nm and 858.60 nm for pump and signal wave, respectively, corresponding to a generated differencefrequency wavelength of -4.26 pm (2350 cm-’). Tuning of the infrared wavelength was limited to-25 cm-’ by the limited temperature tuning range of the master diode laser. In conclusion, DFG in AgGaS, utilizing diode/Ti: A1203 and diode/diode laser input configurations has been demonstrated, producing tunable infrared radiation at a wavelength around 5 pm. As much as 47 pW of cw and 89 pW of pulsed infrared radiation around 4.3 pm have been generated by difference-frequency mixing the outputs of an injection-seeded GaAlAs tapered semiconductor amplifier and aTi:Al,O, laser in AgGaS, using type I noncritical phasematching. It is anticipated that the use of an extemal enhancement cavity for the nonlinear mixing crystal will also result in significantly improved DFG performance. This compact mid-infrared source is promising for a wide range of applications, including chemical analysis, remote sensing, pollution detection, and medical research.

Guides for atoms

Abstract: mirror, we use the evanescent wave that is formed by total internal reflection of a strong laser beam in a (glass) prism. The evanescent wave provides a strong intensity gradient, and thus combines a large potential with a very short interaction time, thereby limiting spontaneous emission even further. To reflect sodium atoms with a velocity of 1 m/s, at a detuning of 2 GHz, a laser intensity of -6 W/ cm' is required. To obtain a reasonable reflective area mirror, this means a laser power of -1 W is required, just barely within the range of commercial dye lasers. We achieve high laser intensities over a bigger spot sue by coupling the laser to a thin dielectric wave guide, that is deposited on a prism. Thus we obtain an evanescent wave which is a factor of 100-1000 stronger than would be the case for the bare prism.' We present the first measurements using such an enhanced evanescent wave as a mirror in which to reflect atoms at normal incidence. Sodium atoms are collected in a magneto-optical trap, cooled to -40 p K using polarization gradient cooling and then released to accelerate in the gravity field. The atomic mirror sits 1 M O mm under the trap, and reflects the atomic wave. The reflected atoms are detected in the trap region after their ballistic flight time. We report a large enhancement of the evanescent wave, observed by reflection of atoms dropped from a 10mm hei ht on a large area atomic mirror (10 mm) up until large detunings (10 GHz) using moderate amounts of laser power (500 mW). 'Institut d'Optique Thhorique et Appliqute, B.P. 147, F-91403 d'orsay, France