The semiconductor lasers in use today are on one hand, prized, and highly praised, for their small size, light weight, longevity and
energy-efficiency, -and on the other, criticized for their susceptibility to frequency-fluctuations brought about by changes in
temperature and driving current. Once this "wrinkle" is ironed out, semiconductor lasers will become the default light-sources, for
satellites' onboard interferometers. Our studies have been directed at stabilizing oscillation frequency to the atomic absorption line,
and using negative electrical feedback to the injection current. Frequency stabilization is accomplished, by either; a) applying direct
modulation to the semiconductor laser's driving current, or b) modulating the reference frequency, to obtain the error signal needed
for stabilization. In this instance, Faraday effect-based stabilization was used. This indirect oscillation frequency stabilization has no
discernable effect on spectra width, but, stability was no better than that observed in the system using the direct modulation.
When we compared Faraday effect- and direct modulation-based methods of stabilization, in order to uncover the root-cause of the
discrepancy, sensors picked up system noise, the source of which was heat generated by the heavy current applied to a magnetic coil
used to apply the Faraday effect. We also substituted a permanent magnet for the electromagnet.
We have succeeded, thus far, in stabilizing laser diode (LD) frequencies to Rb absorption lines, by means of negative electrical
feedback. While the absorption lines were stable over the long term, the Doppler Effect's influence was evident, in broadened spectrum
linewidth. To avoid the problem in subsequent tests, we used Rb-saturated absorption signals.
In this work, we demonstrated potentials of two applications; one was as a reference signal source for estimation of other LD's
frequency stabilization system, and the other was a light source for generation of THz radiation.¬«W
The precise interferometric systems employed in today's artificial satellites require semiconductor lasers of the
highest caliber. To this end, efforts to stabilize their oscillation frequencies and narrow spectrum line-widths
continue relentlessly. While a number of different approaches have been tested, none have provided overall,
long-term stability. Most recently, we employed a Doppler-free absorption line of Rb atoms, with a precision
temperature controller and an improved laser mount. In this instance, relative optical frequency stability rated
9.07×10-13≤σ(2,τ)≤7.54×10-10, in averaging time for 0.01s≤τ23s. By introducing an optical feedback, which
narrows the laser's linewidth, we obtained improved frequency stability.