Rolf-Hermann Rinkleff

White-light cavities, atomic phase coherence, and gravitational wave detectors

We propose a new concept to realize optical cavities with large buildup but broadband response (white-light cavities) using atomic phase coherence. We demonstrate that strongly driven double-12 systems can show negative dispersion without absorption, which is needed in order to compensate for the variation of the wavelength with frequency. Internal buildup profiles and the cavity bandwidth of standard devices and whire-lighr cavities will be briefly compared. These devices may be useful to improve the bandwidth and sensitivity of future generations of laser interferometric gravitational wave detectors.

Low-noise, tunable diode laser for ultra-high-resolution spectroscopy

We demonstrate the excellent spectral properties of a diode laser setup that combines good tunability with superb short-term frequency stability and controllability. It is based on merging two concepts, the diode laser with resonant optical feedback and the grating stabilized diode laser. To characterize the short-term performance we beat two essentially identical diode lasers and find a short-term linewidth of ~11 kHz. Phase locking between these lasers is achieved with a servo bandwidth as small as 46 kHz, although an analog phase detector is used that requires subradian residual phase error. Despite small phase error detection range and small servo bandwidth, cycle-slip-free phase locking is accomplished for typically many 10 min, and the optical power is essentially contained in a spectral window of less than 20 mHz relative to the optical reference. Due to the excellent performance this laser concept is well suited for atomic or molecular coherence experiments, which require phase locking of different lasers to each other, and as part of a flywheel for optical clocks.

A new kind of heterodyne measurement of coherent population trapping in an atomic beam

Abstract A new heterodyne technique is presented for the simultaneous measurement of dispersion and absorption of atomic transitions useful especially for coherent two photon transitions. This technique is compared with traditional homodyne interferometer and with modern frequency modulation techniques. First results are the properties of a coherent population trapping (CPT) scheme realized in a cesium atomic beam. The measured linewidth of the CPT-resonance is ⋍ 300 kHz (FWHM) with a residual absorption of less than 2 × 10−3 cm−1 and the dispersion is equivalent to a group velocity of v g ≈ c 5000 .

Experimental demonstration of negative dispersion without absorption

We present the results of an experiment proving in principle that negative anomalous dispersive transparent media can be realized. The Ca-transition 4s 2 1 S 4s4p 1 Pa tl s 423 nm was chosen to investigate the absorption and index of 01

External-cavity diode laser in second-order Littrow configuration

In this Letter, we propose and demonstrate an external-cavity diode laser in second-order Littrow configuration. This topology utilizes a low-efficiency diffraction grating to establish a high-finesse external cavity, strong optical feedback, a high polarization discrimination, and a circular TEM00 output mode. In our proof-of-concept experiment, we realized a cavity with a finesse of 1855, being, to the best of our knowledge, the highest value ever reported for a three-port-grating-coupled cavity. With optical feedback, the laser threshold of the laser diode employed was reduced by a factor of 4.

Electromagnetically induced transparency, electromagnetically induced absorption and giant Kerr effect in closed degenerate two level systems

Spontaneous transfer of coherence has proven to be a good interpretative scheme for the explantation of the spectra of a probe laser probing a closed degenerate two-level systems. With its aid it was possible to give an explanation for the emergence of electromagnetically induced absorption and also to make predictions on the associated coupling laser spectra. Here we extend our work on the role of the coupling laser in electromagnetically induced absorption presenting new measurements of the probe and coupling laser absorption and dispersion spectra - taken in the D2 line of caesium - which reassert the importance of spontaneous transfer of coherence in the generation of electromagnetically induced absorption spectra. All measurements were performed with linearly polarised coupling and probe laser of orthogonal polarisation, acting on a perpendicularly propagating caesium atomic beam to minimise the Doppler broadening of the lines. For sake of completeness we compared the electromagnetically induced absorption spectra with electromagnetically induced transparency spectra obtained in another two-level system within the same line. The measured probe spectra were used to calculate the refractive index of caesium in the presence of electromagnetically induced transparency and absorption. On that basis we could calculate the effect of Kerr nonlinearities and measure nonlinear Kerr coefficients of the order of n2 ≈ 10-5 cm2/mW with absorption coefficients of the order of &agr; ≈ 0.1 cm-1.

Comparative study of index of refraction: The strongly driven and the degenerate two-level systems

This study compares the experimental results of absorption and refractive index of a probe laser measured in a strongly driven two-level atom with the results measured in a degenerate two-level system using pump-probe spectroscopy. This work demonstrates the possibility of realization an anomalous dispersive transparent medium using the strongly driven 4s2 1S0 - 4s4p 1P1 Ca transition. Absorption and phase shift profiles are measured as function of the driving field intensity using a Ca atomic beam. With increasing driving field intensities absorption and phase shift decrease, but the absorption decreases stronger than the dispersion. Results show that the resonant absorption and the anomalous dispersion are reduced with respect to the non-driving case by a factor 490 and 47, respectively. This means that a ~ 10-fold enhancement of the amount of dispersion provided per amount of absorption is attained.

Experimental Comparison between the Index of Refraction in Strongly Driven and Degenerate Two-Level Systems

Negative dispersion and transparency in a strongly driven calcium two-level system and positive dispersion and transparency or anomalous dispersion and enhanced absorption in closed degenerate two-level systems in caesium have been observed using pump-probe spectroscopy.

Inversion of the Coupling Absorption at the Two-Photon Resonance in a Coupling-Probe-Spectroscopy Experiment

After the discovery of electromagnetically induced absorption (EIA), both theoretical and experimental research was performed to explain not only the probe laser absorption and dispersion spectra, but also those of the coupling laser. The investigations of EIA in degenerate two-level systems have often been realized using two linearly polarized lasers of orthogonal polarization [1]. However, the simplest configuration leading to EIA is the so-called N-system [2] which basically requires the simultaneous adoption of a circularly polarized coupling laser and a linearly polarized probe (here called σ−π). To our knowledge, no experimental measurements of the coupling laser exist in the configurations (σ+−σ−, π−σ− or σ+−π).

Giant Kerr effect in degenerate closed transitions

Giant Kerr nonlinearities about twelve orders of magnitudes greater than in glass were measured under negligible absorption conditions within two different closed transitions of the cesium D2 line characterized y electromagnetically induced transparency or absorption.