Time-encoded mid-infrared Fourier-domain optical coherence tomography: erratum.

We present an erratum to our Letter [Opt. Lett.46, 4108 (2021)OPLEDP0146-959210.1364/OL.434855] and make a correction to the labeling of the absorption bands (reversed order for CH vibrations) indicated in Fig. 2(a). This does not change the scientific conclusions of the original Letter.

Time-encoded mid-infrared Fourier-domain optical coherence tomography.

We report on a technically simple approach to achieve high-resolution and high-sensitivity Fourier-domain optical coherence tomography (OCT) imaging in the mid-infrared (mid-IR) range. The proposed OCT system employs an InF3 supercontinuum source. A specially designed dispersive scanning spectrometer based on a single InAsSb point detector is employed for detection. The spectrometer enables structural OCT imaging in the spectral range from 3140 nm to 4190 nm with a characteristic sensitivity of over 80 dB and an axial resolution below 8µm. The capabilities of the system are demonstrated for imaging of porous ceramic samples and transition-stage green parts fabricated using an emerging method of lithography-based ceramic manufacturing. Additionally, we demonstrate the performance and flexibility of the system by OCT imaging using an inexpensive low-power (average power of 16 mW above 3µm wavelength) mid-IR supercontinuum source.

Full-field optical coherence tomography in a balanced detection mode.

We discuss balanced time-domain full-field optical coherence tomography (FF-OCT) realized in a Mach-Zehnder configuration. The balanced detection scheme and spatial phase shifting allow single-shot acquisition and reconstruction in FF-OCT. Combined with a 2D quadrature signal-based demodulation technique applying the Riesz transform, previously illustrated for a dual-shot temporal phase shifting in FF-OCT, we demonstrate the concept for single-shot spatial phase shifting. The monitoring of dynamic processes by time-domain FF-OCT is enabled by this approach. The advantage of single-shot acquisition consists of having no failure due to phase changes over time. However, it demands an accurate registration of both spatially shifted interferograms.

Mid-infrared Fourier-domain optical coherence tomography with a pyroelectric linear array.

Optical technology in the mid-infrared wavelength range is currently a rapidly developing field initiated by the availability of novel high-power and spatially coherent sources. Non-destructive testing techniques based on these sources are very promising for industrial and medical applications. However, there are still many engineering problems due to the technical challenges and high prices of the optical elements suitable for the mid-infrared region. In this paper, we report the development and performances of the first mid-infrared Fourier-domain optical coherence tomography based on a supercontinuum source and low-cost pyroelectric detector. The system is designed to operate in the spectral region around 4 µm. Experimental results are demonstrated for detections of embedded microstructures in ceramic materials and subsurface oil paint layers.