Coherent anti-Stokes Raman metrology of phonons powered by photonic-crystal fibers

Ultrafast background-free ro-vibrational fs/ps-CARS thermometry using an Yb:YAG crystal-fiber amplified probe

A novel laser system for ro-vibrational spectroscopy using coherent anti-Stokes Raman Scattering in hybrid fs/ps regime is presented. A single Yb:KGW laser source is used as a master laser to generate the three CARS laser beams, namely the pump and Stokes femtosecond pulses and a 58 ps probe pulse. Master oscillator power amplifier (MOPA) architecture is implemented to increase the probe output power using a custom two stage free space linear amplifier. The probe is 0.37 cm^-1 in width and 100 µJ in energy to allow resolving the Q-branch ro-vibrational lines of N₂ and recording single shot CARS spectra at kHz repetition rate in flames. An original and simple technique based on the study of the influence of probe delay and polarization has been setup to optimize nonresonant background rejection, with no loss in resonant contribution. CARS performances are reported for N₂ thermometry between 300 K and 3000 K, demonstrating state of the art precision.

Free-beam spectral self-compression at supercritical peak powers

We demonstrate free-beam spectral self-compression of ~100-GW femtosecond laser pulses due to self-phase modulation (SPM) in a transparent dielectric. While all the earlier studies of SPM-induced spectral narrowing have been performed using optical fibers, experiments and simulations presented in this Letter show that this type of spectral transformation can be implemented as a part of a full three-dimensional field-waveform dynamics and can be extended to peak powers ∼10⁵ times higher than the critical power of self-focusing. With a properly chosen initial chirp, spectral self-compression is accompanied by pulse compression, providing spectral-temporal mode self-compression as a whole.

Enhanced-contrast optical readout in ultrafast broadband Raman quantum memories

The signal-to-noise contrast of the optical readout in broadband Raman quantum memories is analyzed as a function of the pulse widths and phase properties of tailored optical field waveforms used to write in and read out broadband photon wave packets. Based on this analysis, we quantify the tradeoff between the readout contrast and the speed of such memories. Off-resonance coherent four-wave mixing is shown to provide a source of noise photons, lowering the readout contrast in broadband Raman quantum memories. This noise cannot be suppressed by phase matching, but can be radically reduced with a suitable polarization arrangement and proper field-waveform tailoring.

Accurate modeling of high-repetition rate ultrashort pulse amplification in optical fibers

A numerical model for amplification of ultrashort pulses with high repetition rates in fiber amplifiers is presented. The pulse propagation is modeled by jointly solving the steady-state rate equations and the generalized nonlinear Schrödinger equation, which allows accurate treatment of nonlinear and dispersive effects whilst considering arbitrary spatial and spectral gain dependencies. Comparison of data acquired by using the developed model and experimental results prove to be in good agreement.

Pulse-width-tunable 0.7 W mode-locked Cr: forsterite laser

A mode-locked chromium forsterite laser with output power in excess of 0.7 W, a central wavelength of 1.25 μm, a pulse repetition rate of 29 MHz, and an output pulse-width-tunable from 40 to 200 fs is demonstrated. The dynamics behind the buildup of ultrashort light pulses in this laser is shown to involve spectral and temporal breathing due to the interplay of gain, Kerr nonlinearity, and dispersion effects. The pulse-width-tunable 1.25 μm output delivered by the developed laser source suggests a powerful tool for nonlinear-optical bio-imaging and offers an advantageous front end for extreme-power laser technologies.

Ultrafast three-dimensional submicrometer-resolution readout of coherent optical-phonon oscillations with shaped unamplified laser pulses at 20 MHz

An ultrafast three-dimensional readout of coherent optical-phonon oscillations from a diamond film is demonstrated using temporally and spectrally shaped ultrashort laser pulses, delivered by a compact, oscillator-only laser system. This system integrates a long-cavity ytterbium-fiber-laser-pumped 30 fs Cr:forsterite oscillator with a photonic-crystal-fiber soliton frequency shifter and a periodically poled lithium niobate spectrum compressor, providing coherent Raman excitation and time-delayed interrogation of optical phonons in diamond at a 20 MHz repetition rate with a submicrometer spatial resolution.