Time-dependent laser linewidth: beat-note digital acquisition and numerical analysis

Abstract

We revisit and improve the optical heterodyne technique for the measurement of the laser coherence, by digital acquisition of the beat-note and numerical analysis of the resulting signal. Our main result is that with the same experimental setup we reach the very "short-time linewidth" with the highest accuracy as well as the frequency noise spectrum.

Linewidth narrowing via low-loss dielectric waveguide feedback circuits in hybrid integrated frequency comb lasers

“…Each spectrum in this set was analyzed using a Voigt fit to extract the Lorentzian width. Each spectrum showed a slightly different center position and spectral shape, due to drift of the hybrid laser and reference laser [45]. Two representative examples are shown in Fig.…”

Highly-Sensitive Phase and Frequency Noise Measurement Technique Using Bayesian Filtering

“…In this paper, we demonstrate both numerically and experimentally that optical phase and frequency noise measurement methods which solve the MMSE problem significantly outperform -in the achievable measurement range and accuracy -conventional techniques relying on delayinterferometer and direct demodulation, respectively [3], [4]. The reason for this is that the methods reported in [3], [4], are not a solution to the MMSE problem and thereby do not employ any filtering of the measurement noise. Another widely used approach, not compared to in this paper, is based on cross-correlation [5].…”

“…It should be noted that the phase and frequency noise measurement techniques reported in [3], [4], [5] do provide accurate phase and frequency noise measurements if the optical power is sufficiently high and the frequency range of interest is not too large (up to ∼10 MHz). However, the conventional methods do not scale well for low optical signal powers and when measuring frequencies exceeding ∼10 MHz (SNR decreases for increasing measurement bandwidth).…”

Comparative Study of Techniques for Measurement of Linewidth and Frequency Noise of Single-Frequency Lasers

“…Ongoing work will extend these experiments to study the time-dependence of the linewidth [1], and apply these techniques to lasers at various wavelengths of interest for quantum technologies (including 698, 780 and 813 nm).…”

“…Heterodyne measurement -beat note between ring laser and commercial NPRO (Coherent Inc, Mephisto, specified linewidth of 1 kHz over 100 ms), recorded in frequency domain (RF spectrum analyser) and in time domain (high-speed digitiser). Time-domain data used to calculate frequency noise PSD [1] (independent measurement from frequency discriminator approach).…”