By shifting the first and second rows of air holes of slotted photonic crystal waveguide, the bandwidth of slow light can be increased, with small group velocity dispersion.
The axial resolution of PAOM is 23 µm, which is determined by the ultrasonic bandwidth, and the axial resolution of the SD-OCT is 6 µm, which is determined by the bandwidth of the light source [ 1].
In our system, the axial resolution, determined by the bandwidth of the light source, is approximately 6.2 μm, and the lateral resolution, determined by the imaging system, is approximately 9.5 μm.
Figure 1(b) shows the theoretical longitudinal resolution at each wavelength, estimated from 2ln 2/π (λc/Δ λ), where λc is the center wavelength, and Δ λ is the bandwidth of the light source in the case of a Gaussian-shaped spectrum.
The depth range is determined by the spectrometer design and the bandwidth of the OCT light source and commercially available SD-OCT devices have limited scan depth up to 7 mm.
We know that almost everyone has three types of "cone cells" in their retina that each respond to a different bandwidth of light.
The sensitivity roll-off was limited by the bandwidth of the balanced photodetector and finite light source coherence length (the roll-off from the coherence length itself introduces a 6 dB sensitivity drop at 6 mm in air).
Moreover, due to the improvement of the spectral resolution, the spectral bandwidth of the light falling onto one pixel could also be reduced, giving a reduced sensitivity fall off over the imaging depth for the system (see below).
In addition, the control of the bandwidth of the reflection resonance, related to the light intensity and spatial porosity distributions, was investigated to optimize the optical performance.
With the bandwidth of state-of-the-art semiconductor-based light sources, water absorption is not a severely limiting factor for the axial resolution, provided that the center wavelength is close to the absorption minimum.
