Abstract
We report on hybrid mode-locked laser operation of a tapered semiconductor amplifier in an external ring cavity, generating pulses as short as 0.5 ps at 88.1 MHz with an average power of 60 mW. The mode locking is achieved through a combination of a multiple quantum well saturable absorber (>10% modulation depth) and an RF current modulation. This designed laser has 20 nm tuning bandwidth in continuous wave and 10 nm tuning bandwidth in mode locking around 786 nm center wavelength at constant temperature.
Highlights
Ultrashort-pulse semiconductor lasers have been introduced as compact, efficient, low-cost sources for a wide variety of applications, ranging from nonlinear frequency conversion, remote sensing, and spectroscopy, to free-space communication
Tapered amplifiers are more commonly used in a master-oscillator power amplifier (MOPA) setup, where the temporal and spatial characteristics of the output of a low-power oscillator are well maintained through amplification in a tapered structure [7, 8]
The tap amplifiers (TAs) was first characterized in an MOPA setup, to determine the input intensity and pump current that lead to a saturated output
Summary
Ultrashort-pulse semiconductor lasers have been introduced as compact, efficient, low-cost sources for a wide variety of applications, ranging from nonlinear frequency conversion, remote sensing, and spectroscopy, to free-space communication. The average output power is limited to only a couple of milliwatts, and the energy typically to 20 pJ per pulse [3] Another difficulty is the complex nonlinear interrelation between the optical field, the current density, and the index of refraction, resulting in pulse-phase modulation that can not be compensated. The advantages over the MOPA configuration are ease of alignment, a superior beam quality mostly defined by the cavity, and cost saving, since only one laser device is used. It is an unusual mode-locked oscillator for having the highest gain per cavity roundtrip as compared to most solid-state mode-locked oscillators. As compared to conventional mode-locked semiconductor lasers, the short pulse duration is achieved at a higher peak power and pulse energy
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