Wenchao Liao

Ultrahigh-speed optical coherence tomography utilizing all-optical 40 MHz swept-source

We present an ultrahigh-speed optical coherence tomography (OCT) based on an all-optical swept-source with an A-scan rate of 40 MHz. The inertia-free swept-source, which has its output power of 41.2 mW and tuning range of 40 nm and high scan linearity in wavenumber with Pearsons correlation coefficients r of 0.9996, consists of a supercontinuum laser, an optical band-pass filter, a linearly chirped fiber Bragg grating, an erbium-doped fiber amplifier, and two buffer stages. With sensitivity of 87 dB, high-speed OCT imaging of biological tissue in vivo is also demonstrated.

Linear-in-wavenumber swept laser with an acousto-optic deflector for optical coherence tomography

We report a novel linear-in-wavenumber (k-linear) swept laser source based on an acousto-optic deflector (AOD). The AOD-based optical filter includes an acousto-optic deflector and a reflection grating. The laser may tune k linearly in wavenumber over time due to its appropriate configuration and is favorable for fast imaging because it avoids data resampling and recalibration, as are required in conventional swept source optical coherence tomography (SS-OCT). We achieved k-linearity with Pearsons r correlation coefficients of 0.99995 without and 0.99997 with optimization. The laser has a tuning range of 50 nm, a 3 dB swept range of 42 nm (FWHM), output power of 2.56 mW, 6 dB sensitivity roll-off depth of 0.941 mm, and central wavelength of 1064 nm at a scanning rate of ∼20 kHz. Scanning rate as high as ∼400 kHz is also achieved for this laser with the tuning range 49 nm, swept linearity of 0.99990, output power of 2.30 mW, and a 6 dB sensitivity roll-off depth 0.550 mm. SS-OCT imaging with linear-in-wavenumber swept laser is also demonstrated.

Optical computing for optical coherence tomography

We propose an all-optical Fourier transformation system for real-time massive data processing in high speed optical coherence tomography (OCT). In the so-called optical computing OCT, fast Fourier transformation (FFT) of A-scan signal is optically processed in real time before being detected by photoelectric detector. Therefore, the processing time for interpolation and FFT in traditional Fourier domain OCT can be dramatically eliminated. A processing rate of 10 mega-A-scans/second was experimentally achieved, which is, to our knowledge, the highest speed for OCT imaging. Due to its fiber based all-optical configuration, this optical computing OCT system is ideal for ultrahigh speed volumetric OCT imaging in clinical application.

AUTOMATED ASSESSMENT OF EPIDERMAL THICKNESS AND VASCULAR DENSITY OF PORT WINE STAINS OCT IMAGE

Optical coherence tomography (OCT) enables in vivo imaging of port wine stains (PWS) lesions. The knowledge of vascular structure and epidermal thickness (ET) of PWS may aid the objective diagnosis and optimal treatment. To obtain the structural parameters more rapidly and avoid user intervention, an automated algorithm of energy map is introduced based on intensity and edge information to extract the skin surface using dynamic programming method. Subsequently, an averaged A-scan analysis is performed to obtain the mean ET and the relative intensity of dermis indicating the corresponding vascular density. This approach is currently successfully applied in clinical diagnosis and shows promising guidance and assessment of PDT treatment.

All-Fiber-Optics-Based Microwave Photonic Filter With Tunable Center Frequency and Passband Plus Notch

We propose and demonstrate a microwave photonic band-pass filter (MPF), which features a single light source, with continuously and independently tunable center frequency and bandwidth. The center frequency and bandwidth can be adjusted by tuning the variable optical delay line and the position of a spatial filter, respectively. Using a balanced photodetector, the baseband, which is ineradicable in some conventional designs, and the common-mode noise are canceled in our proof-of-concept experiment. Alternatively, a notch with continuously tunable frequency can also be added in the MPF. The experimental measurements of the frequency response of this MPF are demonstrated, which have a good agreement with the theoretical simulations.

The ultimate road to real time 3D optical coherence tomography imaging

We have presented linear-in-wavenumber swept laser and all-optical 40MHz swept-source as the optical source, and compressed sensing and time serial optical computing to process the massive imaging data for real time 3D optical coherence tomography imaging.