METHOD OF CREATING AN OPTICAL ATOM TRAP AND ATOM TRAP APPARATUS, EMPLOYING AN INCOHERENT LIGHT FIELD

Abstract

A method of creating an optical atom trap comprises the steps of providing an incoherent light field with a light source apparatus, by creating a pulsed laser light beam of laser pulses with a repetition rate equal to or above 100 kHz and a relative spectral width of 10.sup.−4 to 10.sup.−2, coupling the pulsed laser light beam to an input end of a multimode waveguide device and guiding the pulsed laser light beam by total internal reflection to an output end of the multimode waveguide device, wherein the incoherent light field is provided at the output end, and creating the optical atom trap for trapping atoms in an atom trap chamber device by coupling the incoherent light field to the atom trap chamber device, wherein the optical atom trap has a trap frequency and the atoms have multiple resonance frequencies, and the laser pulses for providing the incoherent light field are created such that the repetition rate is above the trap frequency and the spectral width is below a spectral range between the resonance frequencies. Furthermore, an optical atom trap apparatus for optically trapping atoms is described.

Claims

1-15. (canceled)

16. Method of creating an optical atom trap, comprising the steps of: providing an incoherent light field by creating a pulsed laser light beam of laser pulses with a repetition rate equal to or above 100 kHz and a relative spectral width of 10.sup.−4 to 10.sup.−2, coupling the pulsed laser light beam to an input end of a multimode waveguide device and guiding the pulsed laser light beam by total internal reflection to an output end of the multimode waveguide device, wherein the incoherent light field is provided at the output end, and creating the optical atom trap for trapping atoms in an atom trap chamber device by coupling the incoherent light field to the atom trap chamber device, wherein the optical atom trap has a trap frequency and the atoms have multiple resonance frequencies, and the laser pulses for providing the incoherent light field are created such that the repetition rate is above the trap frequency and the spectral width is below a spectral range between the resonance frequencies.

17. Method according to claim 16, wherein the multimode waveguide device has at least one of the features the multimode waveguide device has a circularly asymmetrical cross-sectional shape, the multimode waveguide device comprises a square core optical fibre, and the multimode waveguide device has a longitudinal length of at least 80 cm.

18. Method according to claim 16, wherein the pulsed laser light beam is created with a mode-locked pulse laser.

19. Method according to claim 16, further comprising stabilizing the output power of the incoherent light field at the output end of the multimode waveguide device by employing a feedback stabilization loop device.

20. Method according to claim 16, wherein the incoherent light field is spatially modulated by and a trap potential of the atom trap is generated with a digital micro-mirror device.

21. Method according to claim 16, wherein the optical atom trap is an optical dipole trap.

22. Optical atom trap apparatus, comprising: a light source apparatus including a multimode waveguide device having an input end and an output end and being arranged for receiving a pulsed laser light beam at the input end and guiding the pulsed laser light beam by total internal reflection, wherein the multimode waveguide device is adapted for providing an incoherent light field at the output end, and a pulse laser source device arranged for creating the pulsed laser light beam of laser pulses with a repetition rate equal to or above 100 kHz and a relative spectral width of 10.sup.−4 to 10.sup.−2, and an atom trap chamber device configured for receiving the incoherent light field and creating an optical atom trap for trapping atoms having multiple resonance frequencies, said optical atom trap having a trap frequency, wherein the pulsed laser source device is configured for creating the laser pulses such that the repetition rate is above the trap frequency and the spectral width is below a spectral range between the resonance frequencies.

23. Optical atom trap apparatus according to claim 22, wherein the multimode waveguide device has a circularly asymmetrical cross-sectional shape.

24. Optical atom trap apparatus according to claim 22, wherein the multimode waveguide device comprises a square core optical fibre.

25. Optical atom trap apparatus according to claim 22, wherein the multimode waveguide device has a longitudinal length of at least 80 cm.

26. Optical atom trap apparatus according to claim 22, wherein the pulse laser source device comprises a mode-locked pulse laser.

27. Optical atom trap apparatus according to claim 22, further comprising a feedback stabilization loop device arranged for stabilizing the output power of the incoherent light field at the output end of the multimode waveguide device.

28. Optical atom trap apparatus according to claim 22, wherein the light source apparatus is arranged in combination with an atom trap chamber device configured for receiving the incoherent light field and creating an optical atom trap for trapping atoms having multiple resonance frequencies, said optical atom trap having a trap frequency, and the pulse laser source device is configured for creating the laser pulses such that the repetition rate is above the trap frequency and the spectral width is below a spectral range between the resonance frequencies.

29. Optical atom trap apparatus according to claim 22, further comprising a digital micro-mirror device being arranged for shaping the incoherent light field and selecting a shape of the atom trap.

30. Optical atom trap apparatus according to claim 22, wherein the optical atom trap is an optical dipole trap.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Further details and advantages of the invention are described in the following with reference to the attached drawings, which show in:

[0053] FIG. 1: a schematic illustration of a light source apparatus with features according to preferred embodiments of the invention; and

[0054] FIG. 2: a schematic illustration of an optical atom trap apparatus with features according to preferred embodiments of the invention.

PREFERRED EMBODIMENTS OF THE INVENTION

[0055] Features of preferred embodiments of the invention are described in the following with reference to a light source apparatus, wherein the waveguide device comprises an optical fibre, the pulse laser source device comprises a fs pulse laser and the power of the output light field is actively stabilized using a control loop. It is noted that the implementation of the invention is not restricted to these features. Depending on the application of the invention, another waveguide device or pulse laser source device can be used and/or the active stabilization can be omitted. Further optical components can be added. For instance, the pulse laser source device can be provided with a mode filter, like a single mode fibre. Exemplary reference is made to an optical atom trap apparatus, which is operated with the incoherent light provided according to the invention. Details of operating the optical atom trap apparatus are not described as they are known per se from conventional techniques.

[0056] According to FIG. 1, an embodiment of the light source apparatus 100 for creating incoherent light 1 and an atom trap comprises a waveguide device 10, including an optical fibre 11 with an input end 12 and an output end 13. The optical fibre 11 is a square-core (or other circularly asymmetrical) multimode optical step-index fibre, e. g. with a core dimension of 150 μm*150 μm and a length of 300 cm, made of e. g. fused silica. Each of the input and output ends 12, 13 comprise flat smooth end facets. The input end 12 can be provided with an anti-reflective coating (not shown). The optical fibre 11 can be arranged with a straight or curved shape, e. g. in a protective container.

[0057] Furthermore, the light source apparatus 100 has a pulse laser source device 20, which comprises a mode-locked femtosecond pulse laser 21, e. g. a frequency-doubled Er laser or a Ti-sapphire laser. The fs pulse laser 21 generates spatially coherent light providing a pulsed laser light beam 2 of laser pulses to be coupled via focussing optics 22 (coupling lens in) to the optical fibre 11. With a practical example, the pulsed laser light beam 2 has a repetition frequency of 80 MHz, a central wavelength of 700 nm to 800 nm, a spectral width of 5 nm and an average power of 0.2 W. The mode-locked femtosecond laser 21 provides spectral widths of multiple nanometres which allows fast decorrelation. Its comb-like spectrum gives rise to well-defined beating frequencies in the range of hundreds of MHz such that the intensity noise spectrum (apart from these beating frequencies) is similarly low as that of single-mode lasers.

[0058] By coupling the pulsed laser light beam 2 to the optical fibre 11 accommodating multiple fibre modes, fast decorrelation is obtained. The optical fibre 11 provides a delaying element with different propagation times for each of the fibre modes. In the picture of totally internally reflected light rays, straightly propagating rays arrive at the output end 13 earlier than rays travelling at an angle since the distance covered is longer. In an electromagnetic wave picture, the different rays correspond to different spatial modes. Since the spatial modes have distinct intensity profiles, the spatial decorrelation is achieved, so that the incoherent light field 1 is output at the output end 13 of the optical fibre 11.

[0059] The fibre output end 13 acts as a secondary, incoherent light source, and is imaged with an output optics 14 (coupling lens out) into an atom trap chamber device 210 (see FIG. 2).

[0060] The light source apparatus 100 is provided with a feedback stabilization loop device 30, comprising a photodiode 31, a feedback control unit 32 and an acousto-optical modulator (AOM) 33. A portion of the output light field 1 is deflected with a beam sampler 34, e. g. a semi-transmissive plate, and a focussing lens 35 to the photodiode 31. Depending on the current power of the output light field 1, the feedback control unit 32 drives the AOM 33, such that possible temporal power changes are compensated and the output light field 1 has a constant power. By driving the AOM 33, the transmission of the pulsed laser light beam 2 is modified. To this end, preferably a mode filter (not shown) is arranged between the femtosecond pulse laser 21 and the AOM 33. Thus, a feedback-based intensity stabilization may be installed and residual temporal noise of the femtosecond pulse laser 21 is minimized.

[0061] According to FIG. 2, an embodiment of an optical atom trap apparatus 200 according to the invention comprises the light source apparatus 100 of FIG. 1 and a schematically illustrated atom trap chamber device 210. By focussing the incoherent light field 1 into the atom trap chamber device 210, an atom trap 3, in particular a trapping potential thereof, is formed. The atom trap chamber device 210 has a configuration and is operated as known per se in prior art, e. g. as described in [8]. A digital micro-mirror device 211 (arrangement schematically shown) can be provided for spatially modulating the shape of the light field and generating a shape of the atom trap 3.

[0062] The features of the invention disclosed in the above description, the drawings and the claims can be of significance individually, in combination or sub-combination for the implementation of the invention in its different embodiments.