Spectral Hole Burning Medium Research Articles

Observations of self-induced ultraslow light in a persistent spectral hole burning medium

We present observations of self induced ultraslow light in a persistent spectral hole-burning rare-earth doped crystal. The observed group delay (velocity) is as long as 40 micros (75 m/s), which is comparable to that obtained using electromagnetically induced transparency or coherent population oscillations. We analyze the observed ultraslow light as a function of frequency detuning, light intensity, and atom population (oscillator strength). The present observation of ultraslow light in a persistent spectral hole-burning medium gives potentials to all-optical information processing such as on-demand all-optical buffer memories.

Slow light with persistent spectral hole burning in waveguides

We model numerically the reshaping of a weak probe pulse propagating in an absorptive, optically dense, persistent spectral hole burning medium under conditions of slow group velocity. Saturated holes are burned in waveguide geometry by illumination in the transverse direction with low absorption, whereas the probing is carried out in longitudinal wave guiding directions with high absorption. We show that by choosing optimum hole spectrum, the Gaussian probe pulse may be delayed by several times its original duration, while overall pulse shape distortion is less than 1% and average energy loss is less than 10%.

Coherent integration of 0.5 GHz spectral holograms at 1536 nm using dynamic biphase codes

Spectral hole-burning-based optical processing devices are proposed for coherent integration of multiple high-bandwidth interference patterns in a spectral hole-burning medium. In this implementation, 0.5 GHz spectral holographic gratings are dynamically accumulated in Er3+:Y2SiO5 at 4.2 K using a 1536 nm laser frequency stabilized to a spectral hole, along with commercial off-the-shelf components. The processed data, representing time delays over 0.5–2.0 μs, were optically read out using a frequency-swept probe; this approach makes possible the use of low-bandwidth, large-dynamic-range detectors and digitizers and enables competitive processing for applications such as radar, lidar, and radio astronomy. Coherent integration dynamics and material advances are reported.

Spectroscopy, persistent hole burning, and holographic applications of naphtophthalocyanine/haloanthracene systems

We report on the spectroscopic and hole burning properties of free-base naphtophthalocyanine with and without 1-chloranthracene in polymer host. These materials exhibit a strong 0–0 absorption band in the region 800 nm matching the wavelength range of most semiconductor and Ti:Sapphire lasers. The materials studied feature two persistent hole burning photochemical mechanisms, i.e. one-photon proton tautomerization, and two-photon-gated hole burning likely due to donor–acceptor electron transfer. The last mechanism includes the long living intermediate state. The hole width at 1.5 K is about 300–400 MHz depending on the hole burning conditions, while the inhomogeneous width is about 10 7 MHz. Holographic storage is an important potential application of these materials. We demonstrated 10 plane wave holograms angularly multiplexed at one frequency channel in a spectral hole burning medium. It was shown that the M/# is still a valid system metric and the measured M/# in one frequency channel is about 0.01.

Temporally multiplexed Fourier holography and pattern recognition of femtosecond-duration images

Image frames of femtosecond duration have been recorded and successively played back by (1 + 2)-dimensional Fourier holograms in a spectral hole burning medium. The duration and timing of frames are encoded into modulation of the distribution of dye molecules over their absorption frequencies, while images are encoded (in 2-D spatial-frequency representation) into modulation of dye density over the hologram plate. It is shown that separately recorded frames are recalled successively by the read-out pulse. Streak-camera measurements on model signals ascertain that despite the circumstance that molecules of the same absorption frequency and spatial location carry simultaneously information about the different frames recorded, there is no crosstalk between the frames, i.e. they are distinctly separated in time in accordance with values of delays set relative to the reference pulse in the recording procedure. A possibility to perform pattern recognition by a single hologram plate containing two 2-D filters matched to different text fragments on a microfilm slide, is demonstrated.

Holography in frequency selective media II: Controlling the diffraction efficiency

A novel hologram storage technique based on recently reported causality effects in spectral hole-burning media [1] is presented. Simultaneously sweeping the phase and frequency of CW recording light produces holograms with new diffraction properties. In particular the distribution of the light in the different diffraction orders becomes asymmetric and can be easily controlled by the direction of the phase shift. The line shape of phase and frequency swept holograms can be designed in a way which yields many advantages for optical data storage. Compared with normal holograms recorded at a single frequency the maximum diffraction efficiency has been increased by a factor of 5.

Frequency‐Selective Time‐Domain Data Storage and Processing by the Interference of Stimulated Photon Echoes

Controlled picosecond time-domain interference of photochemically accumulated stimulated photon echoes excited by different laser pulses have been analyzed theoretically and observed experimentally in octhaethylporphin-doped polystyrene at 2K. The methods of segment wise storage and reconstruction of light signals in a selected time interval and performing operations of addition and subtraction have also been demonstrated. Potential applications of observed time-domain interference of different type coherent responses in spectral hole-burning media have been discussed