Abstract
The use of an unbalanced interferometer has been shown to be an interesting alternative to high-finesse optical cavities to reduce the frequency noise of a laser by active stabilization. In a self-heterodyne configuration, the resulting frequency-to-amplitude noise discrimination obtained when demodulating the heterodyne beat signal scales with the pathlength difference between the two interferometer arms, so that long fiber delays up to a few kilometers have typically been used in the near-infrared [1]. Here, we apply this approach to reduce the frequency noise of a quantum cascade laser (QCL) in the mid-infrared (MIR) spectral region. Owing to the poor availability of frequency-shifter modulators and low-loss single-mode optical fibers in the MIR, we temporarily restricted the experimental scheme to a self-homodyne configuration with a short free-space pathlength difference of 1 m acting as a frequency-to-amplitude noise converter. With this preliminary scheme, we achieved a reduction of the QCL frequency-noise power spectral density (PSD) by almost 40 dB over a large range of Fourier frequencies and a resulting linewidth narrowed below 10 kHz at 1-s integration time, compared to almost 500 kHz for the free-running laser.
© 2019 IEEE
PDF ArticleMore Like This
Atif Shehzad, Pierre Brochard, Renaud Matthey, Thomas Südmeyer, and Stéphane Schilt
SW4N.5 CLEO: Science and Innovations (CLEO:S&I) 2019
X. Chen, A. Golinelli, B. Bussière, E. Gontier, P.-M. Paul, O. Tcherbakoff, P. d’Oliveira, and J.-F. Hergott
cf_p_38 The European Conference on Lasers and Electro-Optics (CLEO/Europe) 2019
Gang Zhao, D. Michelle Bailey, and Adam J. Fleisher
SF3G.2 CLEO: Science and Innovations (CLEO:S&I) 2020