Application of digital signal processing in locking of CW lasers on optical frequency combs

0426202 - ÚPT 2015 ME eng A - Abstrakt
Čížek, Martin - Číp, Ondřej - Šmíd, Radek - Hrabina, Jan - Mikel, Břetislav - Lazar, Josef
Application of digital signal processing in locking of CW lasers on optical frequency combs.
21th annual International Conference on Advanced Laser Technologies ALT´13. Book of Abstracts. Budva: University of Montenegro, 2013. s. 146.
[ALT´13. Annual International Conference on Advanced Laser Technologies /21./. 16.09.2013-20.09.2013, Budva]
Grant CEP: GA ČR GPP102/11/P819; GA ČR GAP102/10/1813; GA TA ČR TA01010995; GA MŠMT ED0017/01/01; GA MŠMT EE2.4.31.0016
Institucionální podpora: RVO:68081731
Klíčová slova: digital signal processing * CW lasers * optical frequency combs
Kód oboru RIV: BH - Optika, masery a lasery

In cases when it is needed to lock the optical frequency of a CW laser such as a DFB diode laser to a precise metrological reference a possible way is to utilize a setup where an optical frequency comb is used for transferring the stability of a radio frequency (RF) normal (GPS-disciplined oscillator, H-maser, etc.) to the optical domain. Such system takes the signal generated by the RF standard (usually 10 MHz or 100 MHz) as a reference and stabilizes the repetition (frep) and offset (fceo) frequencies of the comb contained in the RF output of the f-2f interferometer. In the next level, the frequency of a beat note (fbeat) between the tunable DFB diode laser and a selected component of the comb spectrum is locked to the same RF standard. As a result, we get a diode laser with optical frequency derived directly from a stable RF reference. These control loops are usually built around analog electronic circuits processing the output signals from fast photodetectors. The presented work describes a different approach based on digital signal processing and software-defined radio algorithms used for processing the f-2f and beat-note signals. The measurements of frep, fceo and fbeat were analyzed by means of calculating Allan deviations for times ranging up to 10 000 s. The digital system is able to stabilize the 100 MHz repetition frequency with absolute deviations observed in mHz. The offset frequency stabilized at 10.7 MHz center exhibits fluctuations in kHz order. In case of fbeat stabilized at 5 MHz offset from a comb spectrum component, the observed fluctuations were in 0.1 kHz order of magnitude. Observed stabilities in the RF domain result in the overall performance of the complete system in the optical domain where it is able to stabilize a diode laser with optical frequency stability in the 10–11 order.
Trvalý link: http://hdl.handle.net/11104/0235657