Simple carrier-envelope phase control and stabilization scheme for difference frequency generation-based systems

Intensity noise in difference frequency generation-based tunable femtosecond MIR sources

We characterize the intensity noise of two mid-infrared (MIR) ultrafast tunable (3.5-11 μm) sources based on difference frequency generation (DFG). While both sources are pumped by a high repetition rate Yb-doped amplifier delivering 200 μJ 300 fs at a central wavelength of 1030 nm, the first is based on intrapulse DFG (intraDFG), and the second on DFG at the output of an optical parametric amplifier (OPA). The noise properties are assessed through measurement of the relative intensity noise (RIN) power spectral density and pulse-to-pulse stability. The noise transfer mechanisms from the pump to the MIR beam is empirically demonstrated. As an example, improving the pump laser noise performance allows reduction of the integrated RIN (IRIN) of one of the MIR source from 2.7% RMS down to 0.4% RMS. The intensity noise is also measured at various stages and in several wavelength ranges in both laser system architectures, allowing us to identify the physical origin of their variation. This study presents numerical values for the pulse to pulse stability, and analyze the frequency content of the RINs of particular importance for the design of low-noise high repetition rate tunable MIR sources and future high performance time-resolved molecular spectroscopy experiments.

Spectral coherence properties of continuum generation in bulk crystals

The stability of the phase difference between two white-light continua, generated from the same 180-fs pulses at ≃1035 nm, is assessed by a modified Bellini-Hänsch interferometer. Mutual spectral phase stability is studied and quantified as a function of several parameters: pulse energy, position of the nonlinear crystal with respect to the beam waist and interaction length. Our results show that intrapulse decoherence may significantly contribute to the measured CEP noise floor. In addition, spectrally-resolved intensity-to-phase coupling coefficients are measured and stability regions are identified.

Versatile optical frequency combs based on multi-seeded femtosecond optical parametric generation

This study proposes and demonstrates a versatile method for near- and mid-infrared optical frequency comb generation using multi-seeded femtosecond optical parametric generation. The method allows one to divide the repetition rate by an arbitrarily large integer factor, freely tune the offset frequency, and adjust the common phase offset of the comb modes. Since all possible degrees of freedom are adjustable, the proposed method manifests itself as versatile optical frequency synthesis.