G. Gorju

10-GHz bandwidth RF spectral analyzer with MHz resolution based on spectral hole burning in Tm/sup 3+/:YAG

We demonstrate the first 10-GHz instantaneous bandwidth radio-frequency spectrum analyzer based on spectral hole burning in Tm/sup 3+/:YAG. It exhibits 10 000 frequency channels and a resolution better than 1 MHz. Thanks to the fast and linear chirping capabilities of the laser used, it has a potential 100% probability of interception and a response time in the millisecond range. Its linear dynamic range of 16 dB is presently essentially limited by the modest amount of optical power available and can be further improved.

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.

10GHz Bandwidth rf spectral analyzer with megahertz resolution based on spectral-spatial holography in Tm 3+ :YAG: experimental and theoretical study

Different architectures of rf spectral analyzers based on the spectral photography scheme in spectral-hole-burning materials are theoretically and experimentally investigated. The microscopic atomic response for the recording and reading of the rf spectra and taking into account the spatial extension of the beams is calculated for different analyzer configurations. The spectral resolution and the signal-to-noise ratio of the analyzer are derived. These predictions are experimentally tested using spectral-hole burning in Tm3+:YAG for a couple of configurations and sizes of the beams. In each case, the resolution, linear dynamic range, and bandwidth of the spectrum analyzer are determined.

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.

Stimulated optical pumping in a Tm3+:YAG crystal

The possibility of using stimulated emission to improve the optical pumping of Tm3+ ions embedded in Tm3+:YAG to the 3F4 level is explored. The oscillator strengths and the frequencies of the transitions between the ground crystal field level of 3H4 to the different crystal field levels of 3F4 are measured at low temperature. Stimulated emission measurements at 1461 nm are performed to evaluate the optical pumping efficiency. Application to the spectral tailoring of Tm3+:YAG for quantum information applications is discussed.

Photon echoes in an amplifying rare-earth-ion-doped crystal

In this contribution, we report on what is believed to be the first experimental demonstration of photon echoes in an amplifying rare-earth ion-doped crystal and highlighted the advantages of the process. It considerably improves the diffraction efficiency and the echo power in single shot, up to a factor 3 in our relatively low optical density sample.

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.

Active Stabilization of External Cavity Diode Laser Rapidly Chirped over 10 GHz by an Optoelectronic Digital Servo-loop Control

Monomode laser sources with fast frequency chirping capabilities are crucial in several fields, including optical processing of RF signals (Gorju, et. al., 2005), reflectometry or coherent manipulation of atoms. All these domains need fast and mode-hop-free frequency scans through a broad spectral range (typically 10 GHz in 1 ms) with high spectral purity. It means that the frequency deviation from a perfect linear chirp has to be much lower than 1 MHz when integrated over the whole chirp bandwidth.

Wide Band & high resolution optical coherent processing of RF signals in Er:YSO using a frequency agile laser

In this paper, the first wide band and high resolution demonstration of the chirp transform algorithm is presented. Because it is performed with a frequency agile laser source, this demonstration opens the way to the wealth of wide band spectral coherent processes that rare-earth ion doped crystals can handle. Using this source, the chirp transform process is demonstrated with a bandwidth in excess of 1 GHz together with more than 20,000 independent frequency channels.