Laser Cooling of Silica Glass

Laser cooling of a solid is achieved when a coherent laser illuminates the material in the red tail of its absorption spectrum, and the heat is carried out by anti-Stokes fluorescence of the blue-shifted photons. Solid-state laser cooling has been successfully demonstrated in several materials, including rare-earth-doped crystals and glasses. Silica glass, being the most widely used optical material, has so far evaded all laser cooling attempts. In addition to its fundamental importance, many potential applications can be conceived for anti-Stokes fluorescence cooling of silica. These potential applications range from the substrate cooling of optical circuits for quantum information processing and cryogenic cooling of mirrors in high-sensitivity interferometers for gravitational wave detection to the heating reduction in high-power fiber lasers and amplifiers. Here we report the net cooling of high-purity Yb-doped silica glass samples that are primarily developed for high-power fiber laser applications, where special care has been taken in the fabrication process to reduce their impurities and lower their parasitic background loss. The non-radiative decay rate of the excited state in Yb ions is very small in these glasses due to the low level of impurities, resulting in near-unity quantum efficiency. We report the measurement of the cooling efficiency as a function of the laser wavelength, from which the quantum efficiency of the silica glass is calculated

MOPA-Lasersystem mit Rückreflexschutz

The invention relates to a MOPA laser system having at least one laser oscillator (MO) which generates laser radiation at an emission wavelength (λ0), and having an optical amplifier (PA) after the laser oscillator (MO) in the direction of propagation of the laser radiation, which amplifier amplifies the laser radiation and thereby expands it spectrally to a useful bandwidth (∆λ). The problem addressed by the invention is that of providing an improved MOPA laser system which is designed for a high power of the amplified laser radiation and which is insensitive to back reflections. Unavoidable back reflections should neither influence the output power of the optical amplifier (PA) nor lead to the destruction of the laser oscillator (MO) or other components of the system. The invention solves this problem by arranging an optical band pass filter (BPF) between the laser oscillator (MO) and the amplifier (PA), which filter is transparent for laser radiation at the emission wavelength (λ0), wherein those spectral fractions of the reflecting laser radiation, i.e. the laser radiation incident on the band pass filter (BPF) contrary to the propagation direction, which lie outside the permitted range (4) in respect of wavelength, are reflected in the propagation direction at the band pass filter (BPF)

Optisches Fasersystem mit Modenfeldanpassung

Die Erfindung betrifft ein Fasersystem mit wenigstens einer lichtleitenden aktiven Faser (1) und wenigstens einer damit verbundenen lichtleitenden passiven Faser (2), wobei die aktive Faser (1) in einem lichtführenden Bereich (7) einen ersten Dotanden enthält, der bei einer Pumpwellenlänge optisch anregbar ist und bei einer Arbeitswellenlänge Licht emittiert. Es ist Aufgabe der Erfindung, die Herstellung passiver Fasern, die jeweils an spezielle aktive Fasern angepasst sind, gegenüber dem Stand der Technik flexibler und kostengünstiger zu gestalten. Diese Aufgabe löst die Erfindung bei dem genannten Fasersystem dadurch, dass die passive Faser (2) in einem lichtführenden Bereich (7) einen zweiten Dotanden enthält, der bei der Pump- und Laserwellenlänge nicht optisch anregbar ist. Außerdem betrifft die Erfindung ein Verfahren zur Herstellung modenfeldangepasster lichtleitender Fasern, wobei eine erste und eine zweite Faser (1, 2), die unterschiedliche Funktionalitäten aufweisen, hinsichtlich der stofflichen Zusammensetzung und hinsichtlich der Prozessführung bei der Faserherstellung, bis auf den jeweils enthaltenen Dotanden, übereinstimmen