Temp Tracker and Temp Tracker 12 ch (single-channel and 12-channel versions) programs are designed for use with an atomic gravity gradiometer. They support the stable operation of the injection-locked slave laser(s) in an autonomous regime. Due to changes of environmental conditions and aging, slave lasers tend to drift from the locking range and need to be relocked. This program checks the injection-locking range for each slave laser and re-centers them with respect to the master lasers, if needed. The master laser is assumed to be locked at an absorption line of Cs.

The software monitors the state of up to 12 injection-locked lasers. It feed-forwards the found value to the lasers’ temperature controllers so as to keep the free-running lasers’ wavelengths in the center of the locking range. The software insures the stable operation of the system over long periods of time, and allows the system to recover from accidental unlocking.

The program uses 12 channels for temperature control, and 12 channels for current control by outputting the voltage to the slave laser controllers. The channels are explicitly shown in the front panel. Current is used for the fast scan of the wavelength. Its linear ramp is determined by the Offset and Amplitude input from the front panel. Temperature controls output the voltage, offsetting the initial temperature settings in order to keep the absorption signal always centered on the ramp.

A single input channel of DAQ is coupled with a 12-channel multiplexer circuit to receive the input signals from the absorption cells. To query each channel, the program produces a digital code word corresponding to the desired combination of eight binary inputs of the multiplexer. A specially designed algorithm is used for determining the center of the locking range, which is found to be stable to varying signal contrast and to the presence of the noise.

This work was done by Dmitry Strekalov of Caltech for NASA’s Jet Propulsion Laboratory.

This software is available for commercial licensing. Please contact Karina Edmonds of the California Institute of Technology at (626) 395-2322. Refer to NPO-45907.

Photonics Tech Briefs Magazine

This article first appeared in the October, 2008 issue of Photonics Tech Briefs Magazine.

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