Vincent Crozatier

Phase locking of a frequency agile laser

The authors report on the development and phase locking of a frequency agile laser. The use of a simple unbalanced Mach-Zehnder interferometer together with a wideband phase-locked loop permits to control very fast frequency chirps (up to 3GHz in 5μs) with an excellent precision (frequency error less than 100kHz). The servoloop could be applied to many tunable lasers.

Active stabilization of a rapidly chirped laser by an optoelectronic digital servo-loop control.

We propose and demonstrate a novel active stabilization scheme for wide and fast frequency chirps. The system measures the laser instantaneous frequency deviation from a perfectly linear chirp, thanks to a digital phase detection process, and provides an error signal that is used to servo-loop control the chirped laser. This way, the frequency errors affecting a laser scan over 10 GHz on the millisecond timescale are drastically reduced below 100 kHz. This active optoelectronic digital servo-loop control opens new and interesting perspectives in fields where rapidly chirped lasers are crucial.

Approaching the limits of carrier-envelope phase stability in a millijoule-class amplifier.

The demand for ever shorter light pulses presents a challenge to the detection and stabilization of the carrier-envelope phase (CEP) in amplifier systems. Here we present a combination of single-shot detection and a fast actuator that is capable of measuring and correcting the CEP in every single shot emitted by a millijoule-scale, multi-kHz femtosecond laser amplifier. The residual CEP noise within 50 s amounts to 98 mrad rms in-loop (fast detection, 5·10⁵ shots) and 140 mrad out-of-loop (slow detection, 6250 shots), approaching the noise floor of the f-to-2f measurement. Both values represent a twofold improvement of the CEP stability over previously published results in comparable systems.

Wideband and high-resolution coherent optical transients with a frequency-agile laser oscillator

We report what is believed to be the first experimental demonstration of a wideband spectral coherent process driven by a frequency-agile laser in a rare-earth-ion-doped crystal. The very demanding chirp-transform algorithm is studied in detail and is applied to radio-frequency spectral analysis. A time-bandwidth product of 24,000 is demonstrated.

Sub-12 fs pulses characterization by self-referenced spectral interferometry

11.7 fs nearly perfect Fourier Transform pulses were characterized with Self-referenced spectral interferometry after precise optimization. A measurement quality control criterion is presented. Each experimental result was cross-checked with SPIDER.

Broadband photonic arbitrary waveform generation using a frequency agile laser at 1.5 μm

We use a pulse-compression chirp-transform algorithm to generate broadband photonic arbitrary waveforms. A phase-locked loop frequency agile laser provides the needed broadband frequency scans. The experiment operates at the telecom wavelength of 1.5µm.

Atomic spectral analyzers for radio frequency signal processing

We review recent demonstrations of wide band radio frequency (RF) spectral analyzers based on spectral hole burning technology. The optically-carried RF signal can be analyzed with sub-MHz resolution over tens of GHz instantaneous bandwidth.

Experimental observation of spectral diffusion in an optically pumped Er3+:Y2SiO5 crystal

We report on experimental observations of spectral diffusion mechanisms occurring in an optically pumped erbium-doped Y2SiO5Y2SiO5 crystal. The diffusion is characterized using photon echo spectroscopy on the I15/24→I13/24 transition. Optical pumping creates population inversion on the transition before the echo sequence. Spectral diffusion is then studied under different population inversion conditions. These observations raise new questions on the spectral diffusion mechanisms.

Experimental investigations for designing low phase noise 10-GHz coupled optoelectronic oscillator

We experimentally investigate the impact of relevant parameters such as dispersion regime, and coupling ratio between the two loops on the phase noise performances of a 10 GHz coupled optoelectronic oscillator (COEO). The setup is based on a mode-locked semi-conductor laser at 1.55μm combined to a classical OEO. Optimization of these parameters leads to ultra-low phase noise at close-to-carrier frequencies (-100 dBc/Hz at 100 Hz and -125 dBc/Hz at 1 kHz).

A Model for Designing Ultralow Noise Single- and Dual-Loop 10-GHz Optoelectronic Oscillators

A complete model describing both single- and dual-loop optoelectronic oscillators (OEO) is introduced. It is compared to several experimental configurations, with excellent agreement in all cases. The physical insight into noise coupling mechanisms brought by the model further allows us for the design of ultralow noise OEO. Phase noise performances at 10 GHz with a single 1 km delay line and with a dual 1 km/100 m delay lines are reported. An optimized dual loop configuration exhibits low phase noise floor at high offset frequency (–160 dBc/Hz at 100 kHz) and low spur levels (–145 dBc/Hz), here again in close agreement with our model.