Mingzhen Tian

Optical pulse shaping using optical coherent transients

Using multiple temporally-overlapped, frequency offset and phase-tuned, linear frequency chirps, a new method of multi-GHz optical coherent transient optical pulse shaping and processing in inhomogeneously broadened rare-earth doped crystals is proposed. Using this technique with properly chirped laser sources, multi-GHz processing can be controlled with conventional low-bandwidth electronics and optical modulators. Specifically, this technique enables pulse shaping in the MHz to THz frequency regime with time-bandwidth-products exceeding 100,000, filling the gap between the operating regimes of femtosecond pulse shaping and analog electronics. The low bandwidth (~20 MHz) proof-of-concept demonstrations presented in this paper include pulse train creation, self-convolution, auto-correlation, and chirped pulse compression.

Recovery of spectral features readout with frequency-chirped laser fields

A data-processing technique is proposed for use with conventional frequency-chirped absorption spectroscopy to ensure accurate mapping of spectral features into time-domain signatures with arbitrarily fast readout chirp rates. This technique recovers the spectrum from a signal that is distorted owing to the fast chirp rate and therefore facilitates fast measurement of the spectral features over a broad spectral range with high resolution. Both numerical simulations and experimental results are presented.

Temporally overlapped linear frequency-chirped pulse programming for true-time-delay applications

A novel technique for programming broadband true-time delays that uses two frequency-offset temporally overlapped linear frequency-chirped pulses to produce periodic spectral gratings in an inhomogeneously broadened absorber is presented. Advantages of this technique include its ability to use chirped pulses that are longer than the coherence time of the crystal, less stringent laser frequency-stability requirements for grating accumulation, lower power requirements, a simplified system design, and the ability to tune broadband (multigigahertz) delays over a wide dynamic range (picoseconds to microseconds).

Persistent spectral hole burning in an organic material for temporal pattern recognition

A broad-bandwidth persistent spectral hole-burning organic material is used as a fast optical processor that compares an input temporal-frequency profile with a recorded reference spectral shape. This pattern-recognition procedure relies on a subpicosecond temporal cross-correlation process. The size of the phase-encoding spectral interval exceeds 1 THz. The storage material, the spectral encoder, and the interferometric detector are examined in detail for optimal pattern discrimination. Experimental temporal pattern-recognition results are reported.

Demonstration of optical coherent transient true-time delay at 4 Gbits/s

Multigigabit-per-second true time delay (TTD) was experimentally demonstrated by use of optical coherent transient techniques in a Tm(3+):YAG crystal. A delay accuracy of 1 ps and a delay resolution of 7 ps (both measurement limited) were achieved. The retrieved data retained good fidelity.

Dynamics of broadband accumulated spectral gratings in Tm 3+ :YAG

High-bandwidth accumulated spectral gratings are experimentally studied in Tm3+:YAG by the stimulated-photon-echo technique with a mode-locked picosecond Ti:sapphire laser system. The experimental results show that the spectral grating builds up and decays on the time scale of the metastable-state lifetime (∼10 ms), provided that the time interval of accumulating shots is of the order of the excited-state lifetime (800 µs). An echo efficiency of the order of 0.1% was achieved with pulse intensities 2 orders of magnitude less than those needed for a single-shot process. These results fit well an analytic solution of the Bloch equations and a three-level system relaxation model.

Amplification of high-bandwidth phase-modulated signals at 793 nm

Amplification of high-bandwidth phase-modulated optical signals from integrated-optics phase modulators at 793 nm is experimentally demonstrated using an injection-locking technique. Off-the-shelf wide-bandwidth integrated-optics modulators are power limited at 793 nm owing to photorefractive damage of the LiNbO3 waveguides. Typical optical input powers for these devices at this wavelength are less than 10 mW with optical output powers typically less than 1 mW. To amplify the outputs of these modulators, we injected the phase-modulated light into an antireflection-coated 100-mW single-mode diode laser. With the injection-locking technique, small-signal gains of 23 dB are demonstrated with good signal fidelity up to bandwidths of 3 GHz. A bandwidth limitation is found at approximately 3 GHz for sinusoidal phase-modulated signals, above which signal fidelity is seriously degraded. This limitation is significantly less than the measured relaxation oscillations of ∼5.6 GHz, suggesting a new limitation to injection locking of phase-modulated signals. Amplification of binary-phase-shift-keyed-modulated signals to 6 Gbit/s is also demonstrated with no bit errors over the 256-bit test sequences.

Study of two-wave coupling in Cu:KNSBN using red light

Abstract Two red-wave light mixing amplification in Cu:KNSBN is extensively studied through the gain versus the grating wavelength. The crystal has shown excellent response in the red region. The time evolution of the diffraction efficiency is also investigated.

Multiple-hologram storage for thin layers of Methyl Orange dyes in polyvinyl alcohol matrices

We realized hologram storage within a 0.07-cm(2) light spot in thin layers of polyvinyl alcohol matrices doped with Methyl Orange dyes preirradiated by the 488.0-nm line of an Ar-ion laser with two orthogonal linearly polarized 632.8-nm light beams. By rotation of the sample, multiple-hologram storage was achieved. By controlling the writing time, we have recorded three-hologram and f ive-hologram images in the same light spot. The mechanism of the multiple-hologram storage in Methyl Orange-doped polyvinyl alcohol thin films is discussed.

Broadband photonic arbitrary waveform generation based on spatial-spectral holographic materials

We discuss an approach for the practical implementation of photonic arbitrary waveform generation of microwave signals. We describe and demonstrate an approach using spatial-spectral (S2) holography in rare earth ion doped crystals that has the potential to achieve extremely wide bandwidths (>40 GHz) using conventional electro-optic phase modulators and low bandwidth (<100 MHz) control electronics. We provide analysis of this approach, show simulations, and perform experimental demonstrations of the technique. We show a pulse compression factor of ~15,000 and demonstrate the largest effective bandwidth of 3.8 GHz to date for pulse compression using S2 holography. We also show control and manipulation of up to 30 independent compressed pulses for the creation of arbitrary waveforms.