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Dipartimento di Fisica - Politecnico di Milano

SOlid-state LAseRs (SOLAR)

The SOLAR lab is devoted to the development of innovative solid-state lasers and amplifiers in the near-infrared (NIR) spectral region from 0.75 to 1.5 µm and their applications in advanced laser sensing technologies such as high-precision atomic and molecular spectroscopy, remote sensing of the atmosphere and optical radars, frequency metrology and astronomical measurements. In particular, solid-state lasers operating in the spectral regions around 0.8 µm, 1 µm, and 1.5 µm are based on crystals doped with transition metals titanium (Ti) and with rare earth ions of ytterbium (Yb) and erbium (Er), whereas optical amplifiers are based on Yb-doped and Er-doped fibers. The research carried out in the SOLAR laboratory has led to the realization of laser sources operating in continuous regime, which have demonstrated exceptional performance in terms of spectral purity, and sources operating in pulsed regime, through the passive mode-locking technique (effect Kerr or via saturable absorbers), which led to the generation of ultra-short laser pulses necessary both for the synthesis of new frequency comb sources in the spectral region from 0.5 to 2 µm and for the creation of innovative spectrometers operating in the THz spectral region ( from 0.5 to 5 THz). The activities are specifically aimed at: building a frequency comb in the region between 0.6 and 1.3 µm based on a Yb: CALGO laser system; realization of optical amplifiers in Yb doped fiber capable of generating average output powers up to 100 W at a wavelength of 1030 nm for the generation of coherent X-rays; development of two THz spectrometers based on femtosecond lasers (Ti: sapphire and Yb: CALGO) and photoconductive antennas for the identification of black plastics; development of an ultra-compact Er-glass oscillator in passive mode-locking mode with a repetition frequency greater than 10 GHz for the synthesis of a new frequency comb in the region between 0.5 and 2 µm for the calibration of astronomical spectrometers (astrocomb) .

Kerr-lens mode-locked Ti:sapphire laser.



The SOLAR lab is equipped with: i) 100-Hz narrow-linewdth optical standard at 1.5 µm based on frequency-stabilized Er:fiber laser against Ultra-Low-Expansion (ULE) high-finesse resonator; ii) single-frequency Non-Planar-Ring-Oscillator (NPRO) Nd:YAG at 1064 nm; iii) Kerr-lens mode-locked Ti:sapphire laser at 800 nm (250-MHz pulse repetition frequency, 30-fs pulse duration, 0.3-W average output power); iv) mode-locked Yb:CALGO laser at 1045 nm (160-MHz pulse repetition frequency, 70-fs pulse duration, 70-mW average output power); v) mode-locked Er:fiber laser at 1550 nm (250-MHz pulse repetition frequency, 70-fs pulse duration, 90-mW average output power; vi) pump diode lasers in the wavelength range from 460 to 980 nm; vii) fast photoconductive antennas for THz generation and detection; viii) general purpose optical and electrical instrumentations (optical autocorrelators, optical wavemeter, optical and electrical spectrum analyzers, Fabry-Perot interferometers, fast digital sampler with 40 GHz,  fast digital oscilloscopes).

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