Peter B. Sellin

Programmable frequency reference for subkilohertz laser stabilization by use of persistent spectral hole burning.

We report what is believed to be the first demonstration of laser frequency stabilization directly to persistent spectral holes in a solid-state material. The frequency reference material was deuterated CaF(2): Tm(3+) prepared with 25-MHz-wide persistent spectral holes on the H(6)(3)?H(4)(3) transition at 798 nm. The beat frequency between two lasers that were independently locked to persistent spectral holes in separate crystal samples showed typical root Allan variances of 780+/-120Hz for 20-50-ms integration times.

Semiconductor lasers stabilized to spectral holes in rare-earth crystals

Single-frequency diode lasers have been frequency stabilized to 200 Hz at 1.5 microns and to 20 Hz at 793 nm with 10-100 ms integration times using narrow spectral holes in the absorption lines of Er3+ and Tm3+ doped cryogenic crystals. The narrow spectral holes are used as frequency references, and this laser performance was obtained without requiring vibrational isolation of either the laser or frequency reference. Kilohertz frequency stability for 100 s integration times is provided by these techniques, and that performance should be improved to the Hertz level and should be extended to longer integration times with further development. Miniaturized external cavity diode lasers and 5 mm-sized reference crystals will provide compact portable packages with a closed cycle cryocooler. The achieved frequency stabilization provides lasers that are ideal for interferometry, high-resolution spectroscopy such as photon echoes, real time optical signal processing based on spectral holography, and other applications requiring ultranarrow-band light sources or coherent detection.

Spatial-spectral holographic real-time correlative optical processor with >100 Gb/s throughput

The demonstration of an all-optical, ultra-high-speed, time-domain signal correlator based on spatial-spectral holographic (SSH) technology is described. The fully programmable signal correlator demonstration operates asynchronously and continuously on signals with up to 32 GHz of bandwidth and correlative filter length exceeding a time-bandwidth product of 104, for the equivalent of teraflop-scale processing. Experimental demonstrations are presented that show both digital and analog correlation capability using phase-shift keyed modulation formats to search plain text ASCII data sources for arbitrary phrases at continuous line rate throughputs up to 200 Gbps with minimal latency. These high-bandwidth demonstrations were enabled by improvements in the photonic supporting components and cryogenic SSH for RF and microwave signal processing methods. Potential application of the SSH real-time correlator for high-bandwidth analog or multi-level format signals is discussed.

Efficient spectral and correlative processing with spatial-spectral holography

Spatial-spectral holographic (SSH) materials function as a coherent frequency domain resource for high-performance spectral and correlative processing. Real-time matched filtering of 25 GHz bandwidth signals is demonstrated including simple text searches. Despite cryogenic cooling, SSH processing can be efficient for large scale processing systems.

Programmable frequency reference for laser stabilization using persistent spectral hole burning

Summary form only given. The first known demonstration of laser frequency stabilization using a solid-state persistent spectral hole burning material as the frequency reference is reported. Unlike gas phase transitions or Fabry-Perot resonances, spectral holes for frequency references can be prepared at any frequency within a broad inhomogeneous absorption profile (15 GHz in the material demonstrated here). Several lasers may be stabilized to multiple spectral holes, either in the same or separate absorption bands, with arbitrary frequency separations.