Octave Spanning 1 GHz Ti:sapphire Oscillator For HeNe CH4-based Frequency Combs and Clocks

In this paper, we demonstrate a greatly improved octave spanning 1 GHz Ti:sapphire laser (Fortier, 2006) using the most broadband double-chirped mirror pairs, optimized Kerr-Lens modelocking (KLM) and an optimized output coupler. As a result the laser generates, at 9 W of pump power, 0.6 W-1 W of output power with an output spectrum of more than one octave as measured on a linear scale. The spectrum corresponds to a Fourier limited pulse of 3.5 fs duration. Second harmonic generation with this output in 1mm BBO directly generates 1f-2f beatnotes for carrier-envelop phase stabilization with >55 dB signal-to-noise (SNR) in 100 kHz bandwidth, and by difference frequency generation (DFG) in a 5 mm long PPLN radiation at 3.39 mum is generated. The 3.39 mum radiation is strong enough to result in a beatnote with a single frequency HeNe reference laser of 30 dB. This laser will serve as the clockwork of a HeNe CH₄-based molecular clock (Foreman, 2005) with a measured Allan variance approaching 10~14 in 100 s and as an absolute femtosecond laser frequency comb for an optical arbitrary waveform generator.