Abstract
We demonstrate a novel wavelength-comb-swept laser based on two intra-cavity filters: an acousto-optic tunable filter (AOTF) and a Fabry-Pérot etalon filter. The AOTF is used for the tunable selection of the output wavelength with time and the etalon filter for the narrowing of the spectral linewidth to extend the coherence length. Compared to the conventional wavelength-swept laser, the acousto-optic–based wavelength-comb-swept laser (WCSL) can extend the measureable range of displacement measurements by decreasing the sensitivity roll-off of the point spread function. Because the AOTF contains no mechanical moving parts to select the output wavelength acousto-optically, the WCSL source has a high wavenumber (k) linearity of R2 = 0.9999 to ensure equally spaced wavelength combs in the wavenumber domain.
Highlights
Wavelength-swept laser (WSL) sources have been developed to be a powerful tool for the application of optical sensing and imaging techniques, such as optical Fourier-domain reflectometry (OFDR) and swept-source optical coherence tomography (SS-OCT) [1,2,3]
Among the various factors affecting wavelength-swept lasers, the narrowing of the spectral linewidth is especially important for increasing the interferometric displacement measurement range in OFDR and SS-OCT by improving the coherence length of the light source [3]
Because the frequency of the radio frequency (RF) signal applied to the acousto-optic tunable filter (AOTF) is inversely proportional to the output wavelength, Figure 4a shows that the center of the output wavelength is continuously swept from 1579.4 to 1514.36 nm when an RF signal from 35.4 to 37.0 MHz, respectively, is applied
Summary
Wavelength-swept laser (WSL) sources have been developed to be a powerful tool for the application of optical sensing and imaging techniques, such as optical Fourier-domain reflectometry (OFDR) and swept-source optical coherence tomography (SS-OCT) [1,2,3]. The performance of the wavelength-swept laser can be determined by various factors, such as the spectral bandwidth, linewidth (or coherence length), swept repetition rate, center wavelength and linearity in wavenumber (k). Many studies have been performed to achieve better wavelength-swept laser performance with a broad spectral bandwidth, narrow linewidth, high swept repetition rate, various center wavelengths, and k-linear sweeping. Among the various factors affecting wavelength-swept lasers, the narrowing of the spectral linewidth is especially important for increasing the interferometric displacement measurement range in OFDR and SS-OCT by improving the coherence length of the light source [3]. There has been a limitation in reducing the linewidth in the conventional continuous-spectrum broadband light source of spectral-domain optical coherence tomography (SD-OCT) and the continuous wavelength-swept laser source of SS-OCT. A spectrally sampled broadband light source for SD-OCT and a wavelength-comb-swept laser (WCSL)
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