RESUMEN
We present a novel high-power, frequency-stabilized UV laser source at 326.2 nm, resonant with the Cd 1S0-3P1 narrow intercombination transition. We achieve a maximum produced power of 1 W at 326.2 nm by two successive frequency doubling stages of a narrow-linewidth (<1 kHz) seed laser at 1304.8 nm. Approximately 3.4 W of optical power at 652.4 nm is produced by a visible Raman fiber amplifier (VRFA) that amplifies and generates the second harmonic of the infrared radiation. The visible light is subsequently frequency-doubled down to 326.2 nm in a nonlinear bow-tie cavity using a Brewster-cut beta-barium-borate (BBO) crystal, with a maximum conversion efficiency of approximately 40% for 2.5 W of coupled red power. Full characterization of the laser source, together with spectroscopy signals of all Cd isotopes, spanning more than 4 GHz in the UV, are shown.
RESUMEN
High-power and narrow-linewidth laser light is a vital tool for atomic physics, being used for example in laser cooling and trapping and precision spectroscopy. Here we produce Watt-level laser radiation at 457.75 nm and 460.86 nm of respective relevance for the cooling transitions of cadmium and strontium atoms. This is achieved via the frequency doubling of a kHz-linewidth vertical-external-cavity surface-emitting laser (VECSEL), which is based on a novel gain chip design enabling lasing at > 2 W in the 915-928 nm region. Following an additional doubling stage, spectroscopy of the 1S0 â 1P1 cadmium transition at 228.87 nm is performed on an atomic beam, with all the transitions from all eight natural isotopes observed in a single continuous sweep of more than 4 GHz in the deep ultraviolet. The absolute value of the transition frequency of 114Cd and the isotope shifts relative to this transition are determined, with values for some of these shifts provided for the first time.
RESUMEN
Despite investigations for over 70 years, the absolute limits of human vision have remained unclear. Rod cells respond to individual photons, yet whether a single-photon incident on the eye can be perceived by a human subject has remained a fundamental open question. Here we report that humans can detect a single-photon incident on the cornea with a probability significantly above chance. This was achieved by implementing a combination of a psychophysics procedure with a quantum light source that can generate single-photon states of light. We further discover that the probability of reporting a single photon is modulated by the presence of an earlier photon, suggesting a priming process that temporarily enhances the effective gain of the visual system on the timescale of seconds.