Andreas Wicht

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.

Space-borne frequency comb metrology

Precision time references in space are of major importance to satellite-based fundamental science, global satellite navigation, earth observation, and satellite formation flying. Here we report on the operation of a compact, rugged, and automated optical frequency comb setup on a sounding rocket in space under microgravity. The experiment compared two clocks, one based on the optical D2 transition in Rb, and another on hyperfine splitting in Cs. This represents the first frequency comb based optical clock operation in space, which is an important milestone for future satellite-based precision metrology. Based on the approach demonstrated here, future space-based precision metrology can be improved by orders of magnitude when referencing to state-of-the-art optical clock transitions.

Micro-integrated extended cavity diode lasers for precision potassium spectroscopy in space

We present a micro-integrated, extended cavity diode laser module for space-based experiments on potassium Bose-Einstein condensates and atom interferometry. The module emits at the wavelength of the potassium D2-line at 766.7 nm and provides 27.5 GHz of continuous tunability. It features sub-100 kHz short term (100 μs) emission linewidth. To qualify the extended cavity diode laser module for quantum optics experiments in space, vibration tests (8.1 g(RMS) and 21.4 g(RMS)) and mechanical shock tests (1500 g) were carried out. No degradation of the electro-optical performance was observed.

An alignment-free fiber-coupled microsphere resonator for gas sensing applications

In this paper we report on the assembly of a robust sensor system consisting of a polystyrene microsphere resonator attached to an optical fiber taper. Since the sphere is only supported by the micrometer-sized fiber no further alignment is necessary. This results in a thermally and mechanically well isolated optical resonator system with quality factors as high as 6×105. The narrow resonances of whispering gallery modes supported by the polystyrene resonators shift with temperature at a rate of 3.8 GHz/K. Thus, a sensitive thermometer is established which allows to detect the surrounding gas via its characteristic thermal conductivity.In this paper we report on the assembly of a robust sensor system consisting of a polystyrene microsphere resonator attached to an optical fiber taper. Since the sphere is only supported by the micrometer-sized fiber no further alignment is necessary. This results in a thermally and mechanically well isolated optical resonator system with quality factors as high as 6×105. The narrow resonances of whispering gallery modes supported by the polystyrene resonators shift with temperature at a rate of 3.8 GHz/K. Thus, a sensitive thermometer is established which allows to detect the surrounding gas via its characteristic thermal conductivity.

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 .

Ultra-narrow linewidth DFB-laser with optical feedback from a monolithic confocal Fabry-Perot cavity.

We present a compact, ultra-narrow-linewidth semiconductor laser based on a 780 nm distributed feedback diode laser optically self-locked to a mode of an external monolithic confocal Fabry-Perot resonator. We characterize spectral properties of the laser by measuring its frequency noise power spectral density. The white frequency noise levels at 5 Hz(2)/Hz above a Fourier frequency as small as 20 kHz. This noise level is more than five orders of magnitude smaller than the noise level of the same solitary diode laser without resonant optical feedback, and it is three orders of magnitude smaller than the noise level of a narrow linewidth, grating-based, extended-cavity diode laser. The corresponding Lorentzian linewidth of the laser with resonant optical feedback is 15.7 Hz at an output power exceeding 50 mW.

Micro-integrated 1 Watt semiconductor laser system with a linewidth of 3.6 kHz

We demonstrate a compact, narrow-linewidth, high-power, micro-integrated semiconductor-based master oscillator power amplifier laser module which is implemented on a footprint of 50 x 10 mm(2). A micro-isolator between the oscillator and the amplifier suppresses optical feedback. The oscillator is a distributed Bragg reflector laser optimized for narrow-linewidth operation and the amplifier consists of a ridge waveguide entry and a tapered amplifier section. The module features stable single-mode operation with a FWHM linewidth of only 100 kHz and an intrinsic linewidth as small as 3.6 kHz for an output power beyond 1 W.

High-power distributed Bragg reflector ridge-waveguide diode laser with very small spectral linewidth

We manufactured and investigated distributed Bragg reflector ridge-waveguide diode lasers having sixth-order surface gratings and an emission wavelength around 974 nm. The single-mode output power of the lasers with a total length of 4 mm exceeded 1 W. A very small spectral linewidth of 1.4 MHz (3 dB) consisting of a Lorentzian part of 146 kHz and a Gaussian part of 1308 MHz was measured using a self-delayed heterodyne measurement technique.

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