Electronically tunable picosecond pulse generation from Ho3+-doped fluoride fiber laser using frequency-shifted feedback.

Abstract

In this Letter, we demonstrate electronically tunable picosecond (ps) pulse emission from the 5I6-5I7 transition of the Ho3+ ion by using an acousto-optic tunable filter. The holmium- and praseodymium-codoped ZBLAN fiber laser produced sub-50 ps pulses over a 100 nm tuning range, critically reaching a longest wavelength of 2.94 µm, which overlaps with the peak absorption of liquid water. Measured pulse energies of 8.1 nJ well exceed those expected from picosecond solitonic operation, suggesting possible application in ablative medicine. Furthermore, we present harmonically mode-locked operation of the oscillator, which indicates the possibility of expanding the capabilities of mid-infrared frequency shifted-feedback lasers through the ability to achieve higher pulse repetition rates.