venteon CEP5: A progress report

13 Oct 2016

For many years, the creation of a carrier-envelope-phase stabilised pulse train, in a Ti:Sapphire laser, involved taking a portion of the oscillator output beam and putting it through a photonic crystal fibre or DFG crystal to create an octave spanning spectrum. Then, taking the longer frequency, doubling it, and a creating a beat note against the short end of the spectrum in an f-to-2f interferometer. Any error signal in the f-to-2f signal was fed back to an AOM to modulate the 532 nm pump power to the Ti:Sapphire crystal or into an AOM placed into the ultrashort pulse beam path.

Laser Quantum has recently established a next generation CEP locking scheme (CEP5^TM) that shows major improvements over previous technologies by eliminating two of the most challenging parts of this process: the nonlinear broadening and the AOM.

The nonlinear broadening, as required in any other commercial laser sources, takes typically more than 200 mW to create the octave spanning spectrum, significantly reducing the available optical power for the experiment. The venteon product range includes lasers that are designed to have a natural octave spanning spectrum. Using the whole emission spectrum of Ti:Sapphire and additional spectral enhancing, plus the use of specially designed chirped mirrors to control the phase of pulses, the CEP5 system can lock the CEP phase naturally by taking the extreme wings of this huge spectrum.

Introducing an AOM in the ultrashort output pulse beam path implicates several problems. It not only reduces the available power drastically, but its very design moves the beam. An AOM causes an angular shift in the beam and due to first order diffraction, and even worse, causes spatial angular dispersion of the ultrabroadband pulse.This means that the post-AOM beam changes direction and introduces a frequency shift across the beam profile. In our novel CEP5 systems, we avoid all these problems by using a patented technique of CEPLoQ™. Here, the f-to-2f interferometer error signal is fed back directly into the pump laser, thus eliminating the need for the AOM. As a direct result, no beam pointing instabilities are introduced by the CEP lock. Additionally, this direct feedback operates with a faster response rate to a deeper modulation level. A ±1% modulation depth can be achieved with a bandwidth of 1 MHz, the phase behaviour at 750 kHz is <90˚.

The venteon CEP5 by Laser Quantum is the most natural way for CEP locking. CEP5 is complete carrier-envelope-phase stabilised laser system with sub-5 fs transform-limited pulse duration and extreme low CEP phase noise. Delivering true sub-two cycle pulse with less than 50 as timing jitter, the venteon CEP5 is the ideal source for extreme nonlinear physics.