Pulses from a mid-infrared quantum cascade laser frequency comb using an external compressor

Abstract

A Martinez-type stretcher-compressor is used to modify the spectral phases of a high-power (∼1 W) QCL comb emitted at 8.2 µm with more than 100 cm −1 spectral bandwidth. Using this scheme, we demonstrate a compression of the QCL output from a 134 ps continuous wave waveform, to a train of pulses of width 12 ps, and a power with peak to average ratio of 40.7. An evaluation of the phase noise of the free-running device yields an integrated timing jitter of 335 fs over the frequency range 20 kHz -100 MHz, and a pulse-to-pulse jitter of 2.0 fs.

Femtosecond pulses from a mid-infrared quantum cascade laser

“…2a-c and shows a double-peaked amplitude spectrum. In accordance with previous experimental 21,29 and theoretical 24 findings, these spectral lobes individually exhibit quadratic spectral phases with different GDD. The high degree of mutual coherence among comb modes, is, up to a constant prefactor, shown in Fig.…”

“…Pulse compressor and coherent beat note interferometry. The requirement to compensate large amounts of positive group delay dispersion (GDD)-of the order of some picoseconds squared 13 suggests the use of a grating compressor 28 , as previously proposed 29 . The precise configuration utilized in this work is shown in Fig.…”

Mode-locked short pulses from an 8 μm wavelength semiconductor laser

“…This corresponds to anti-phase synchronization and will be called frequency modulated (FM) comb in the following. It should be mentioned that another approach for generating pulses from QCL FM combs is to compensate their linear chirp using an external grating compressor 32 . However, this approach has to overcome the challenge that the chirp of the QCL is not perfectly linear, which results in relatively long pulses.…”

“…Initial numerical simulations already predict a pulse width reduction of more than a factor two using this approach. A possible alternative direction can be the combination with an external pulse compressor 32 . In this case, the laser could be operated in a regime where a residual but perfectly linear chirp is accepted in order to optimize for a larger spectral span and more efficient use of the gain.…”

Phase analysis and full phase control of chip-scale infrared frequency combs

“…Among them, QCLs generating FCs (QCL-combs) play a key role. The capability of these devices to generate FCs was demonstrated only few years ago both in the MIR and in the THz 16,17 , and they are currently experiencing intense research and development [18][19][20][21] . In order to apply them for high-resolution molecular spectroscopy and metrology, a full frequency stabilization of all the emitted modes is required, together with a technique enabling to monitor the obtained degree of coherence.…”