We present a novel industrial-grade prototype version of a continuous-wave 193 nm laser system entirely based on solid state pump laser technology. Deep-ultraviolet emission is realized by frequency-quadrupling an amplified diode laser and up to 20 mW of optical power were generated using the nonlinear crystal KBBF. We demonstrate the lifetime of the laser system for different output power levels and environmental conditions. The high stability of our setup was proven in > 500 h measurements on a single spot, a crystal shifter multiplies the lifetime to match industrial requirements. This laser improves the relative intensity noise, brilliance, wall-plug efficiency and maintenance cost significantly. We discuss first lithographic experiments making use of this improvement in photon efficiency.
Single-frequency optical synthesizers (SFOS) provide an optical ﬁeld with arbitrarily adjustable frequency and phase which is phase-coherently linked to a reference signal. Ideally, they combine the spectral resolution of narrow linewidth frequency stabilized lasers with the broad spectral coverage of frequency combs in a tunable fashion. In state-of-the-art SFOSs tuning across comb lines requires comb line order switching,1, 2 which imposes technical overhead with problems like forbidden frequency gaps or strong phase glitches. Conventional tunable lasers often tune over only tens of GHz before mode-hops occur. Here, we present a novel type of SFOSs, which relies on a serrodyne technique with conditional ﬂyback,3 shifting the carrier frequency of the employed frequency comb without an intrusion into the comb generator. It utilizes a new continuously tunable diode laser that tunes mode-hop-free across the full gain spectrum of the integrated laser diode. We investigate the tuning behavior of two identical SFOSs that share a common reference, by comparing the phases of their output signals. Previously, we achieved phase-stable and cycle-slip free frequency tuning over 28.1 GHz with a maximum zero-to-peak phase deviation of 62 mrad4 when sharing a common comb generator. With the new continuously tunable lasers, the SFOSs tune synchronously across nearly 17800 comb lines (1 THz). The tuning range in this approach can be extended to the full bandwidth of the frequency comb and the 110 nm mode-hop-free tuning range of the diode laser.
The ESA mission “Space Optical Clock” project aims at operating an optical lattice clock on the ISS in approximately 2023. The scientific goals of the mission are to perform tests of fundamental physics, to enable space-assisted relativistic geodesy and to intercompare optical clocks on the ground using microwave and optical links. The performance goal of the space clock is less than 1 × 10-17 uncertainty and 1 × 10-15 τ-1/2 instability. Within an EU-FP7-funded project, a strontium optical lattice clock demonstrator has been developed. Goal performances are instability below 1 × 10-15 τ-1/2 and fractional inaccuracy 5 × 10-17. For the design of the clock, techniques and approaches suitable for later space application are used, such as modular design, diode lasers, low power consumption subunits, and compact dimensions. The Sr clock apparatus is fully operational, and the clock transition in 88Sr was observed with linewidth as small as 9 Hz.
We report on the realization of a narrow-band continuous-wave laser source in the deep-ultraviolet. Via two consecutive second-harmonic processes starting from a near-infrared diode laser system, we demonstrate an output power of more than 15 mW at 193 nm. The setup is capable of mode hop-free frequency tuning over a range of 100 GHz und coarse tuning over more than 5 nm. We see direct applications of this laser source in the fields of semiconductor metrology and high-resolution spectroscopy in the deep-ultraviolet.
A continuous-wave deep-ultraviolet light source is demonstrated based on a grating-stabilized diode laser pump system and two consecutive nonlinear conversion stages. Using the crystal Potassium Fluoroberylloborate (KBBF), direct second-harmonic generation to 191 nm could be realized with an output power of up to 1.3 mW. The linewidth at this wavelength is estimated to be around 100 kHz. The emission can be tuned mode hop-free over 40 GHz. Our scheme can be easily extended to 193 nm or – given the availability of suitable fundamental sources – to wavelengths as small as 165 nm. These parameters make our light source an ideal tool for applications in deep-ultraviolet metrology and photoemission spectroscopy.
We briefly review the key technology of modern fiber based femtosecond laser sources summarizing advantages and
disadvantages of different mode-locking solutions. A description of possible extensions of a FemtoFiber-type modelocked
Er-doped fiber laser oscillator (1560 nm) reveals the flexibility with respect to wavelength coverage (488 nm ..
2200 nm) and pulse duration (10 fs .. 10 ps). The resulting FemtoFiber family and its versions for instrument integration
allow one to use these state-of-the-art light sources in many important applications, e.g. THz spectroscopy and
microscopy. We show that, depending on the fiber laser model and the THz emitter, THz radiation can be produced with
4-10 THz bandwidth and detected with up to 60 dB signal-to-noise ratio (SNR). Electronically controlled optical
scanning (ECOPS) - a unique method for fast, precise and comfortable sampling of the THz pulse or other pump-probe
experiments - is described and recommended for efficient data acquisition. As examples for modern microscopy with
ultrafast fiber lasers we present results of two-photon fluorescence, coherent microscopy techniques (SHG/THG/CARS)
and fluorescence lifetime imaging (FLIM).
We have observed Bose-Einstein condensation of chromium atoms , whose large magnetic dipole
moment is unique among all species that have been Bose-condensed so far. The arising magnetic forces
are of anisotropic and long-range character and therefore introduce a novel type of interaction in the
physics of ultracold quantum gases. In addition, it is expected that the character of the interaction
present in a chromium BEC can be varied from mainly contact to purely dipolar utilizing one of the
recently observed Feshbach resonances in 52Cr-collisions.
We describe two experiments that use neutral atomic beam techniques to write nanostructures. In the chromium experiment we have used neutral chromium atoms to write periodic nanometerscale structures in a direct way. In a second experiment we have used a self-assembling monolayer as a resist for metastable helium atoms.