Carrier-envelope frequency stabilization of a Ti:Sapphire oscillator using different pump lasers

Abstract

Summary form only given. Among the various femtosecond laser oscillators that are commonly used as optical frequency combs in a wide range of fields, Ti:sapphire oscillators offer the advantage of operating at the highest repetition rates, supporting the shortest pulses with octave-spanning spectra directly from the laser, and exhibiting very low residual frequency noise due to the high quality factor of their resonators. However, they require a pump laser with excellent beam quality emitting around 532nm and show inferior performance when operated with nonideal pump laser. Recently, several cost-efficient alternative pump lasers with smaller footprints than the most commonly used bulky and costly frequency-doubled single-longitudinal-mode (SLM) diode-pumped solid-state (DPSS) lasers became commercially available.In an initial set of measurements [1], we characterized and compared the performance of a carrier-envelope frequency stabilized femtosecond Ti:sapphire oscillator when pumped by four different pump lasers: a frequency-doubled multi-longitudinal-mode (MLM) DPSS laser with active noise cancellation (Lighthouse Photonics Sprout G-10W NET), a frequency-doubled MLM optically pumped semiconductor laser (OPSL, Coherent Verdi G5) and two frequency-doubled SLM DPSS lasers (Coherent Verdi V10, Coherent Verdi V5). The carrier-envelope frequency f0 of the oscillator was stabilized by means of the f-to-2f self-referencing technique, and the residual phase noise of the stabilized oscillator was measured with a second identical f-to-2f interferometer outside the feedback loop. The best performance of the oscillator obtained with each pump laser is shown in Fig. 1. We found an integrated rms residual phase jitter of below 160mrad for all tested pump lasers, which is less than 1/40 of an optical cycle and amounts to an rms timing jitter of less than 70as.The relative intensity noise (RIN) of the pump lasers was also measured. While showing certain signatures that could be traced in the residual phase jitter, the RIN was found to be low enough to enable stabilization of f0 in all cases. We found both SLM and both MLM pump lasers under test to be suitable for carrier-envelope frequency stabilization. More recent results obtained with additional pump sources that were not available in the first study will be presented.