Giuseppe Tandoi was born in Bari, Italy, in 1984. He received the M.Sc. degree in Optoelectronics Systems from the Electrical and Electronics Engineering Department at the Politecnico di Bari, Bari, Italy, in 2007. He then worked on the design lateral gratings for distributed feedback quantum cascade lasers operating at 3.34 μm work in collaboration with the School of Engineering at the University of Glasgow. He received his Ph.D. degree in 2010 from the School of Engineering of the University of Glasgow, UK, for its work on monolithic high power passively mode locked GaAs/AlGaAs quantum well lasers. He is currently working on the integration of optoelectronic devices with gasfilled hollow core fibres for the development of miniature atomic clocks and room temperature magnetometers at the School of Engineering of the University of Glasgow, UK, in collaboration with the National Physical Laboratory, London, UK.

In this paper, we present results from monolithic passively mode-locked GaAs/AlGaAs quantum well lasers operating at 830 nm. Colliding pulse mode locking is achieved at repetition rates of 126 GHz with pulsewidths as short as 0.43 ps, an unprecedented value in monolithic semiconductor lasers operating at such high pulse repetition rates. We use a double quantum well laser epistructure with larger mode size d/Г (d is the quantum well thickness and Г is the optical confinement) and investigate the effect of the saturable absorber length on the mode-locking operation. The experimental results are theoretically explained and reproduced using a traveling wave model with an improved timedomain response for both the gain and the absorber sections of the device. The model confirms that the thermally induced spectral detuning of the absorber relative to the gain section determines both the optimal absorber length and the optimal biasing conditions to achieve the shortest pulse duration and highest peak power.Index Terms-Mode-locked (ML) laser, quantum well (QW) laser, semiconductor laser, short pulse generation.

There is a great desire to extend ultrasonic techniques to the imaging and characterization of nanoobjects. This can be achieved by picosecond ultrasonics, where by using ultrafast lasers it is possible to generate and detect acoustic waves with frequencies up to terahertz and wavelengths down to nanometers. In our work we present a picosecond ultrasonics setup based on miniaturized mode-locked semiconductor lasers, whose performance allows us to obtain the necessary power, pulse duration and repetition rate. Using such a laser, we measure the ultrasonic echo signal with picosecond resolution in a Al film deposited on a semiconductor substrate. We show that the obtained signal is as good as the signal obtained with a standard bulky mode-locked Ti-Sa laser. The experiments pave the way for designing integrated portable picosecond ultrasonic setups on the basis of miniaturized semiconductor lasers.

No abstract

No abstract